Dr Devendra Saroj

Increase in anthropogenic activities proliferated the consumption of resources such as phosphorus; and increase the adverse environmental impacts especially eutrophication on water resources such as lakes. Nutrient recovery from domestic wastewaters to produce a fertiliser has been explored to address these challenges in the context of a sustainable circular nutrient economy. Life cycle assessment (LCA) was performed to holistically assess the impacts of integrating a nutrient recovery system on wastewater and water resource management using Laguna de Bay, Philippines as the geographical boundary. The inventory was developed based on the results of the emerging nutrient recovery reactor operations and the application of the recovered fertiliser on the agricultural crops. The LCA results for the proposed scenario showed environmental benefits of about 83.6% freshwater eutrophication, 102.5% terrestrial ecotoxicity, 26.9% water consumption, 100.7% mineral resource scarcity, while the global warming potential is 95.4% higher than the baseline scenario. Results imply policy review for septage management, system optimisation, and evaluation of alternative methods of wastewater management, in terms of life cycle thinking and sustainability across the globe. The traditional linear supply chains brought about by the industrial revolution and economic development have ensued massive extraction of resources, and significant increase in waste generation resulting in the decline of planetary health 1. This affects transgressions in the global food security and increase in adverse environmental impacts that are interconnected with water-nutrient management and agricultural systems in hotspot regions, mainly in Asia 2. However, the improvement of the quality of water resources and nutrient pathways would require complex problem-solving and collective efforts from scientists, policy makers, and the rest of the society 3. Hence, a paradigm shift from the linear flow model to integrated industrial ecosystem is required, that adapts the circular economy approach and life cycle thinking 4. Nutrient recovery and recycling from waste streams, particularly wastewater, has been considered an efficient driver in closing the loop towards sustainable development and resilience in water-nutrient management 5. This would also particularly address the urgent challenges in phosphorus resource depletion and eutrophication in the context of agri-food systems, clean water, and sustainable sanitation 6. Eutrophication is one of the leading environmental issues, that is as complicated to control and manage as climate change 7,8. Developing countries in Asia, such as Philippines, are greatly affected with eutrophication due to high population density and lack of appropriate sewage and septage treatment systems 9. In fact, the biggest inland water body in the Philippines, Laguna de Bay (Laguna Lake), is already experiencing the effects of eutrophication with regular occurrences of mass fish mortalities 10. This affects 21.4 million people who rely on the lake as their major source of food, water, and livelihood. This prompted the Philippine government to amend its existing policies to update the wastewater effluent quality standards as most of the wastewater treatment plants do not involve nutrient removal yet 11,12. Consequently, about 84% of the households in the Philippines use OPEN

Suspended growth biological process (SGBP) with post-ozonation (O3) was investigated for treatment of simulated complex mixed industrial and domestic wastewater at specific conditions. The SGBP was operated under complete aeration, 30/30-min and 60/30-min on/off aeration cycles and effluent was exposed to ozone at 250 mgO3/h fixed dose and contact time 1 to 60-min. The SGBP performance was maximum under 60/30-min aeration conditions achieving 92.1, 90.6, 83.3 and 83.8% reduction in COD, BOD5, TN and PO4-P respectively. Nitrification (64.1%) was uninhibited even on transition to pulse aeration cycles. The concentrations of diesel oil and methylene blue dye were reduced by 83.6 and 93.5% respectively. Post-ozonation oxidized residual organics up to 19.9%, based on COD measurement, and increased effluent BOD5 up to 49.5%. The results including the crop growth outcomes indicate that SGBP-O3 process has great potential to improve the quality of mixed industrial and domestic wastewater considerably for various water reuse applications.

This study looks at the application of delayed action Passive Infrared (PIR) sensors in the control of water use for urinal flushing. In this we briefly review the literature on urinal controls before reviewing four different approaches to PIR urinal controls. Existing literature discusses some of the pros and cons of different types of urinal control. However, the literature does not consider the differences that occur within individual approaches, based on the way controls operate. This study was initiated at the University of Surrey during 2019 following a water saving audit, in an attempt to bring down one of their largest users of water. This paper therefore aims to identify the most effective way to reduce water consumption of urinal systems, through retro-fitting PIR control systems within the variety of settings across university campuses. This paper also reviews the different reductions achieved over periods of differing use, during term-time, holidays, COVID-19 lockdowns, and the 'new normal'. It found that grouped delayed action flushing was the most effective form of urinal control for reducing water use. It, achieved a 59-64% adjusted reduction during non-COVID-19 periods, and a 35% reduction against the control group during lockdowns saving 98,000 L/day on average across the study.

The main goal of this work is to evaluate the usage of ozone (O3) as a pre-treatment or simultaneously combined with UVC/H2O2 process for the polishing stage treatment of real bio-treated slaughterhouse wastewater. Two different treatment strategies were tested: i) pre-ozonation of the wastewater followed by an UVC/H2O2 process (two-step treatment); ii) simultaneous application of O3/UVC/H2O2 combined process (one-step treatment). For the two-step strategy, the pre-treatment with 30 mg O3/min for 10 min reduces significantly total suspended solids (TSS), turbidity and colour, reducing light filtering effects and increasing the efficiency of the following UVC/H2O2 process. In turn, the one-step treatment strategy (O3/UVC/H2O2) allows a more efficient use of injected O3 by reducing the amount of O3 required (from 273 to 189 mg O3/Leffluent) to achieve similar mineralization levels. The real bio-treated slaughterhouse wastewater treated by O3/UVC/H2O2 process achieved final colour values of 20 Pt/Co, TSS of 35 mg/L and COD of 61 mg O2/L, allowing its direct discharge into water compartments according to European Council Directive 91/271/EEC.

This study aims to assess the physicochemical characteristics of the particulate matter ≤10 µm (PM10) at both congested and non-congested areas of Lahore, the second-largest city of Pakistan. PM10 samples from 10 urban sites in Lahore were analysed for source apportionment. The techniques of scanning electron microscopy/energy dispersive spectrometry (SEM/EDX) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) were used to determine the morphology and the chemical composition of PM10. Thirteen elements including toxic metals were consequently detected and quantified: Ca (48.1%), Zn (17.0%), Fe (13.3%), Al (8.2%), Mg (6.6%), Pb (5.5%), Mn (0.4%), Cu (0.3%), Ba (0.17%), Cd (0.15%), Ni (0.04%), Cr (0.01%) and Co (0.008%). The results showed that the daily PM10 concentration was 6%–9% higher than the World Health Organization’s guideline values at all urban sites of Lahore. The congested sites showed higher contents than the non-congested areas for most of the elements, including Cd (41.8%), Cr (35.0%), Zn (19.7%), Cu (12.7%), Ni (6.2%), Ca (3.4%), Ba (1.2%), Mg (1.2%) and Al (0.07%). The non-congested areas showed higher contents only for Pb (0.07%) and Co (4.3%). The principal component analysis indicated that 72% of PM10 originates from road dust and vehicular sources, and 38% from industrial sources.

In this study, a pilot-scale trickling biofilter (TBF) using pebbles and gravels media was evaluated for the treatment of domestic wastewater. The TBF system was installed in an open environment at residential area of Quaid-i-Azam University, Islamabad, Pakistan, and was operated at three different recirculation flow rates (Q), i.e. 0.04, 0.072 and 0.1 m³/day and under three different HRTs, i.e. 48, 72 and 96 h. It was observed that the efficiency of pilot-scale TBF system in terms of pathogens removal was significant, i.e. at flow rates of 0.04, 0.072 and 0.1 m³/day, an average reduction of 39.8–62.5% (p = 0.007), 35.9–48.6% (p = 0.01) and 25.8–57.3% (p = 0.009) respectively were attained in CFU/mL under different HRTs. Moreover, it has been observed that due to high void spaces up to 30%, pebbles and gravels filter media in co-ordination allowing good microbial growth and increased the diversity of bacterial species. Furthermore, it also facilitate the removal of different pollutant indicators, i.e. chemical oxygen demand (COD) (74.2–80.5%), total dissolved solids (TDS) (60.3–69.5%), electric conductivity (EC) (62.8–68.6%) and phosphates (PO4) (45.3–60.3%). A significant reduction in total nitrogen (TN) (59–63.3%) was observed at flow rates of 0.04 and 0.072 m³/day (p = 0.005). The experimental data of this research study will be helpful for further modification in the TBF system using different filter media in association and selecting optimal HRTs and flow rates in future study to get maximum efficiency of TBF system while treating domestic wastewater.

Current experiences in pilot sanitation projects indicate that the spontaneous precipitation in urine diversion (UD) systems has been one of the main challenges for the implementation of urine source separation on large-scale. As a result of microbial ureolysis, an increased pH leads to the formation of inorganic precipitates, which increases the risk of pipe blockage. Although significant advancements have been made in controlling the spontaneous precipitation in UD systems, experimentation in pilot projects is not enough to provide the feasible and reliable support for technical selection to adapt quickly to changing boundary conditions, such as population size and density. Therefore, established techniques should be constantly reassessed and improved in a broader variety of experimental settings to ensure the wide applicability, economic and environmental benefits, and social acceptance. This work also clarified the importance of establishing standardized evaluation methods, which helps to integrate the knowledge gained from reported specific case studies and provide detailed information that can support the decision makers. On the other hand, the economic assessment indicated that maximizing the value of the urine-derived fertilizers can ensure a favorable rate of return, which is important to attract investors and promote the implementation of urine source separation. Meanwhile, current legislation and government support have provided the opportunities for large-scale implementation of urine source separation. The decision makers should be prepared well to deal with such a paradigm shift.

The adverse environmental impact caused by eutrophication has recently prompted the Philippine government to issue stringent regulatory standards for wastewater effluent quality. The involved stakeholders and industries are assessing the integration of biological nutrient removal (BNR) technologies in the current sewage treatment plant (STP) scenario. Moreover, efforts are being done to utilize wastewater as a resource such us recovery of nutrients as struvite fertilizer from the wastewater sludge. Since BNR and nutrient recovery systems are not yet integrated in STPs, the magnitude of the environmental impacts are yet to be evaluated in the Philippine setting. This study covers the holistic evaluation of the overall environmental performance scores of the following scenarios using a consequential Life Cycle Assessment (LCA) framework integrated with Analytic Hierarchy Process (AHP) in the context of Water-Energy-Food Nexus: 1) current STP scenario; 2) BNR technology; and 3) nutrient recovery system. The environmental impact assessment was done using IMPACT 2002+ methodology in terms of the following impact indicators: human health, ecosystem quality, climate change, resources, aquatic acidification, and aquatic eutrophication. Value judgments from relevant stakeholders were elicited to rank the relative importance of the impact indicators in the evaluation of the overall environmental performance score. The LCA-AHP results show that the integration of a nutrient recovery system is the most preferred scenario. Sensitivity analysis was also done to evaluate the effects of changes in diet and utilization of alternative energy.

Understanding the resources nexus such as food, energy, water, and land will play a crucial role in our progress towards sustainability and resilience. For example, food production is the main driver behind the excessive global use of mineral fertilisers. Though these fertilisers provide critical nutrients such as nitrogen and phosphorous, they also contribute significantly to the carbon footprint and embodied energy of the agri-food systems. In addition, these nutrients from agricultural runoff and sewage may also pollute and cause dead zones in our water bodies. On the one hand, phosphorous scarcity and food security could also pose an existential risk against the backdrop of feeding ten billion people by 2050. One emerging sustainability pathway is the green circular bioeconomy that encourages nutrient recycling from biowastes such as that agricultural waste, food waste, and domestic wastewater.

The present investigation is focused on development of aerobic biofilm on tire derived rubber (TDR) media and then evaluation of such system for bioremediation of Methylene blue (MB) dye for 9 weeks. After 9 weeks of operation, the COD, BOD, ammonia and color values have been declined by 89.2, 98.3, 99.61 and 99.81% respectively, While SEM-EDX results showed a variance in weight percent of various elements in TDR without biofilm i.e. raw TDR media, as well as in the 1st and 9th week samples. Moreover, fine and strong peaks were observed in both the MB simulated wastewater and 9th week TDR samples at 1190, 1300, 1400, 1450, 1500 and 1618 cm-1 respectively by Raman Spectroscopic analysis. Further, FTIR analysis was performed for the MB simulated wastewater, and absorbance peaks ranging from 1591 to 1363 cm-1 and 3410 cm-1 were observed in all the samples with different intensities. To assess the biodeterioration of the TDR media, ATR was performed for the raw, 1st, 2nd and 9th week TDR media samples and in the raw TDR, two important bands, 842 and 2962 cm-1 were noticed representing –CH=CH and –CH3. A clear variation of bands and peak intensities were observed in different support media samples. The results indicate that TDR media is a resilient, chemically resistant material and could be employed for the biofilm growth for biological treatment of textile dye wastewater.

This work reports the influence of ultrasound alone and combined with ozone for the treatment of real abattoir wastewater. Three different frequencies were studied (44, 300 and 1000 kHz) at an applied power of 40 W. The injected ozone dose was fixed at 71 mg/L and the treatment time varied from 1 to 60 min. Using ultrasound alone, 300 kHz was the only frequency showing a reduction in chemical oxygen demand (COD, 18% reduction) and biological oxygen demand (BOD, 50% reduction), while no diminution in microbial content was measured for any of the frequencies studied. Combining ultrasound with ozone, on the contrary, led to a significant decrease in COD (44%) and BOD (78%) removal for the three frequencies under study. A complete inactivation of total coliforms (TC) was obtained, as well as a final value of 99 CFU/mL in total viable counts (TVC, 5 log reduction). That is, the ozonation-sonication combined system was the only treatment method (compared to sonication and ozonation alone) reaching direct discharge limits, as well as meeting drinking water standards for microbial disinfection (TC and TVC).

There is a growing demand for an integrated assessment to identify and select asset management options based on sustainability in the wastewater industry. However, water companies are often not equipped with a rigorous methodology and sufficient resources to perform sustainability assessments. Although many frameworks and tools for sustainability assessment have been developed in academia, practical challenges such as feasibility and usability remain when implementing sustainability assessment methods to support corporate decision-making. This study developed a Multi-Criteria Analysis based framework to evaluate wastewater treatment processes from a sustainability perspective. This study firstly explored the decision and organizational context of a water company with preliminary interviews and then applied the Analytical Hierarchy Process (AHP) with composite scores to evaluate wastewater technologies at a sewage treatment works. The preliminary interviews with stakeholders highlighted that the existing investment decisions were primarily driven by financial cost and compliance whilst calling for a wider consideration of other criteria. A selection of assessment criteria and indicators were then proposed to compare seven treatment technologies at a sewage treatment works. The results of composite scores indicated that the baseline activated sludge process (ASP) was the best option for this study. Experience from the development process highlighted usability, stakeholder engagement and the organizational context should all be considered as part of the design and implementation of the sustainability assessment. The insights from this study provide a valuable practical foundation for applying a multi-criteria approach to perform sustainability assessments and inform asset management decisions in the water company.

Integration of high water-volume and nutrient-rich industrial wastewater into the existing water management plan for agriculture could be a viable option to protect freshwater resources, mitigate water scarcity problems and support the agriculture sector. Hydroponics were set-up to study the effects of treated mixed industrial and domestic wastewater on physiological traits of lettuce and silverbeet. A sustainable hybrid biological-ozonation process was employed for the wastewater treatment. The studied process showed high treatment capacity by removing 96% COD, 92% diesel and 97% methylene blue compounds. Reclaimed streams were analysed for metals using ICP-MS instrument and the concentrations of all elements tested, exception of Cu, Mn, and Mo, fall within the permissible range for crop irrigation. The crops were grown using the effluents (with/without external nutrient) and compared to a recommended nutrient culture and tap water controls. Compared to the control, plants that received external nutrient had a comparable aerial biomass and vegetative growth, higher photosynthetic pigments but exhibited some root development impairments, probably due to high activity of H+, which promoted metal toxicities on plant roots. Under pH-controlled irrigation, an improvement in root growth was observed. The biomass of plants watered with only the treated wastewater were more than 50% higher than the yield in tap water control and plants exhibited high degree of root foraging. The root concentrations of the studied metals, particularly Al, Mn, Cu and Zn were higher than the corresponding shoot concentrations. Pearson correlation analysis showed a significant positive interaction (p

The utilization of dyes in textile industries has enormously increased in recent years and has created several environmental problems. Currently, several methods are in practice to treat wastewaters. Effective and efficient treatment techniques before the discharge of used water in the environment are the need of the hour. This short review covers the research and recent developments in advanced wastewater treatment techniques such as nanophotocatalysis, ceramic nanofiltration membranes, and biofilms. The primary intent of this review article is to contribute the ready-made references for the active researchers and scientists working in the field of wastewater treatment. This review has mainly focused on advanced physicochemical and biological techniques for the treatment of textile dye wastewaters. Further, the influence of various operating factors on the treatment, advantages, and disadvantages of various techniques was also discussed. The recently developed materials for wastewater treatment are also summarized based on the latest available literature.

Resilience is a multi-faceted concept that traces its evolution based on the field of discipline wherein it was used. Various researchers have defined the term throughout the years according to their own expertise. This has impacted the development and evolution of the concept and how it was used in each specific discipline. One of the most recent and important use of the term is in the disaster paradigm. This paper traces the evolution of the definition of resilience and narrows it down to the disaster realm, eventually focusing on small islands as a socio-ecological system. It also discusses the relationship of resilience with vulnerability and enumerates the various tools and methods that have been used to measure both concepts. This review also presents an integration which identifies social, economic and ecological resilience as the different facets of disaster resilience of small islands. This paper reveals that there are gaps in defining disaster resilience of small islands through a socio-ecological systems approach. Moreover, there are few studies on using the participatory approach for determining indicators of disaster resilience which contributes to a research-policy gap in resilience studies. The paper recommends a strong future research direction on how to translate research findings into a tool that could help communities at the local level, especially those living in small islands. [Display omitted]

The unrestricted discharge of domestic and industrial wastewaters along with agricultural runoff water into the environment as mixed-wastewater pose serious threat to freshwater resources in many countries. Mixed-wastewater pollution is a common phenomenon in the developing countries as the technologies to treat the individual waste streams at source are lacking due to high operational and maintenance costs. Therefore, the need to explore the potential of the suspended growth process which is a well-established process technology for biological wastewater treatment is the focus of this paper. Different wastewater constituents: representing domestic, pharmaceutical, textile, petroleum, and agricultural runoff were synthesized as a representative of mixed-wastewater and treated in two semi-continuous bioreactors (R1 & R2) operated at constant operating conditions, namely MLSS (mg/L): 4640-R1, 4440-R2, SRT: 21-d, HRT: 48–72 h, and uncontrolled pH. The system attained stable condition in day 97, with average COD, BOD and TSS reduction as 84.5%, 86.2%, and 72.2% for R1; and 85.1%, 87.9%, and 75.1% for R2, respectively. Phosphate removal on average was by 74.3% in R1 and 76.6% in R2, while average nitrification achieved in systems 1 and 2 were 56.8% and 54.7%, respectively. The biological treatment system has shown potential for improving the quality of mixed-wastewater to the state where reuse may be considered and tertiary treatment can be employed to polish the effluent quality.

The present research is focused on the application of glass beads (GBs) in fixed biofilm reactor (FBR) for the treatment of simulated methylene blue (MB) wastewater for 9 weeks under aerobic conditions. The COD of MB wastewater showed a reduction of 86.48% from 2000 to 270.4 mg/L, and BOD was declined up to 97.7% from 1095.5 to 25.03 mg/L. A drastic increase in the pH was observed until the 3rd week (8.5 to 8.28), and later, marginal changes between 8.30 ± 0.02 were noticed. A dramatic fluctuation was observed in ammonia concentration which increased (74.25 mg/L) up till the 2nd week, and from the 3rd week it started declining. In the 9th week, the ammonia concentration dropped to 16.5 mg/L. The color intensity increased significantly up till the 2nd week (259,237.46 Pt/Co) of the experiment and started decreasing slowly thereafter. The SEM–EDX analysis has shown the maximum quantity of carbon content in the GBs without biofilm, and then in the GB samples of 1st, and 9th-week old aerobic biofilms. Furthermore, Raman spectroscopy results revealed that the 9th-week GBs has a fine and strong MB peak and matched with that of the MB stock solution. Overall, the results have shown that the GBs filter media were suitable for the development of active biofilm communities for the treatment of dye wastewater. Thus, GBs-FBR system can be used for wastewater treatment to solve the current problem of industrial pollution in many countries and to protect the aquatic environment from dye pollution caused by the textile industry.

In this work, the removal of Methylene Blue dye from the synthetic textile effluent has been investigated using a hybrid system (photocatalysis and nanofiltration). The Commercial ZnO powder was used as a catalyst in the photocatalytic operation. Response surface methodology (RSM) was employed to optimize the various operating parameters such as pH, catalyst loading and time duration and this optimization has enhanced the decolorization efficiencies. The results were compared and contrasted with the individual as well as the combined systems at optimized conditions. The results indicate that the photocatalysis process alone has resulted in 33% of dye decolorization and 26.5% of total organic carbon (TOC) removal, while the individual ceramic nanoflitration system has yielded 43% of decolorization and 35.03% TOC removal. About 94% of the dye were decolorized, and 70% of TOC was removed in 94.23 minutes of operation by the hybrid system at optimized initial operating conditions.

Pollution and increasing water demand, especially for agriculture, put severe stress on freshwater sources, and as a result, there is progressive deficit in the global water supply and severe water scarcity is projected in the coming decades. Discharges from domestic, industrial and agricultural activities are potential sources of water pollution, impacting human and environmental health. In the face of growing water scarcity and droughts, coupled with the increasing water demand for irrigation, integration of high water-volume and nutrient-rich industrial effluents, into the existing water management plans for agriculture, could play an important role in tackling the problem of water scarcity. However, there is a gap in knowledge about integration of industrial effluents to sewage treatments and the reuse potential of biologically treated mixed industrial and domestic wastewater in agriculture. This study, therefore, provides a critical review on biological treatment of industrial effluents, including petroleum, textile and pharmaceutical wastewater to better understand the capability of bioprocesses and conditions for efficient degradation of pollutants. The effectiveness of activated sludge-based processes, for the treatment of mixed industrial and domestic wastewater, was critically examined, and biomass acclimation plays a vital role in enhanced biodegradation performance. Finally, the reuse potential of mixed industrial and domestic wastewaters for crop irrigation was assessed by studying the reuse outcomes in different cases where industrial effluents were utilized for crop production. Management practices, such as cultivation of salt- and metal-tolerant crops, blending and dilution of industrial wastewater with freshwater and sewage, could make industrial effluents valuable for irrigation.

Insufficiency of phosphorus due to the limited availability of phosphate rocks is predicted within the next decades. Phosphorus recovery from wastewater sludge was found to be one of the possible alternative sources of phosphorus. Moreover, stringent effluent standards, including that of phosphorus levels, have been newly implemented in the Philippines. Due to these factors, phosphorus recovery from wastewater in Philippine settings was deemed as an important topic to be further studied. In this paper, the feasibility of recovering phosphorus from septage sludge in Metro Manila by the precipitation of struvite crystals was studied. Septage sludge is seen as one of the potential sources and was characterized in terms of the concentration of Mg2+, Ca2+, NH4+ and PO4-3 ions. In the lab-scale experiments conducted, alkaline hydrolysis using sodium hydroxide was performed as a sludge pretreatment before the precipitation proper. Alkaline hydrolysis was done to release the remaining PO4-3 ions from the solids present in the sludge, thereby promoting precipitation after hydrolysis without the need for additional phosphate source. Furthermore, alkaline hydrolysis can effectively release phosphorus without inducing the dissolution of interfering ions such as Ca2+ and other heavy metals. Results show that PO4-3 ions increased by 267.37 mg/L and the total amount of phosphate ions increased from 17.05% to 46.88%, showing the effectivity of the hydrolysis. For the precipitation of struvite, three parameters were controlled: pH, residence time, and Mg:P ratio. After precipitation, the phosphorus recovery efficiency for the runs were each evaluated and analyzed in order to determine the effects of the parameters on phosphorus recovery. The precipitate of the run with the highest phosphorus recovery obtained was then evaluated using XRD analysis. It was found that the sample with the highest phosphorus recovery is 53.12%, which was achieved at pH 9, a residence time of 1 hour, and an Mg:P ratio of 1.5:1. Therefore, it can be concluded that precipitation subjected at pH 9 has the highest potential for higher phosphorus recovery. Further, the residence time has a minimal effect on phosphorus recovery and higher phosphorus recovery can be achieved at a higher Mg:P ratio with increasing potential for struvite recovery.

Nutrient recovery technologies have been constantly developed and optimised to address challenges in water and wastewater management, sanitation, and agri-food systems, while promoting sustainable management of resources and circular phosphorous economy. However, these technologies have been rarely explored beyond the laboratory-scale in developing countries where it is mostly needed. In this study, a nutrient recovery batch reactor system was installed at a local farm in the Philippines to process raw septage from an onsite sanitation system, a septic tank, to recover a high-value fertiliser for local crop production. The batch reactor was used for two processes, namely acid hydrolysis for pre-treatment of septage and chemical precipitation for recovered phosphorous fertiliser (RPF). The recovered fertiliser was then applied to produce eggplants and tomatoes, which are the common crops grown in the farm. Results show that an average of 290 g of RPF was produced for every 100 L of raw septage processed. With hydrolysis, 77% of the phosphate concentration were released as phosphates from the solid component of the raw septage. About 98.5% of phosphates were recovered from the hydrolysed septage. The RPF when applied to the farm’s eggplants and tomatoes has yields comparable to that of the commercial fertilisers. This study was able to demonstrate the potential of a resource-oriented sanitation system that promotes nutrient recycling towards sustainable agriculture that further leads to meeting the United Nations sustainable development goals, particularly zero hunger (goal 2), clean water and sanitation (goal 6), sustainable cities and communities (goal 11), and responsible consumption and production (goal 12).

Despite the existence of a wide range of literature on indicators of disaster resilience in various geographical contexts that have been developed by different agencies and academia, not much has been done to include the insights of practitioners at the local level. This paper seeks to address the lack of practitioner insight and perspective by proposing a mixed methodology in developing composite indicators for the resilience of an island community to disasters. We used a combination of participatory approaches, such as semi-structured interviews with key informants, the web-based Delphi method, and expert interviews through a case study site in the Philippines— the Batanes island province. Principal Component Analysis (PCA) was utilized to analyse the data from web-Delphi, and the results from the content analysis of the interviews were used to support these findings. From a broad list of 144 indicators, the process identified 22 composite indicators for assessing the disaster resilience of an island community. We conclude that the development of new approaches for assessing disaster resilience of island communities is a positive step towards a better understanding and operationalization of the concept of resilience. The process followed in this paper is a significant milestone in developing new approaches to answer the question of what makes an island community resilient to disasters.

The current work explores the treatment of dye wastewater using the combination of photocatalysis and ceramic nanofiltration process. Commercial ceramic membrane and titanium dioxide (TiO2) photocatalyst were used in this study to investigate the removal of Brilliant Green (BG) dye from the synthetic dye wastewater solution. The effect of various operating parameters on dye decolorization and total organic carbon removal were investigated. The operating parameters (pH, catalyst loading and time duration) were optimized using an experimental design model namely Response Surface Methodology (RSM). The use of experimental design by RSM resulted in the improvement of dye decolorization at optimum conditions. In addition to these operating parameters, the trend of initial dye concentration and the influence of catalyst loading on permeate flux was also studied. Around 99% of decolorization was obtained by the hybrid system at 500 mg L− 1 of dye concentration, 1 g L− 1 of TiO2 dosage, pH of 4.2 and 90 min. The integrated system i.e. photocatalytic reactor with nanofiltration membrane has shown complete removal of BG dye compared to individual systems. From the present study, it can be concluded that this integrated system is one of the efficient methods for dye treatment.

Stripping is widely applied for the removal of ammonia from fresh waste leachate. However, the development of air stripping technology is restricted by the requirements for large-scale equipment and long operation periods. This paper describes a high-gravity technology that improves ammonia stripping from actual fresh waste leachate and a machine learning approach that predicts the stripping performance under different operational parameters. The high-gravity field is implemented in a co-current-flow rotating packed bed in multi-stage cycle series mode. The eXtreme Gradient Boosting algorithm is applied to the experimental data to predict the liquid volumetric mass transfer coefficient (KLa) and removal efficiency (η) for various rotation speeds, numbers of stripping stages, gas flow rates, and liquid flow rates. Ammonia stripping under a high-gravity field achieves η = 82.73% and KLa = 5.551 × 10−4 s−1 at a pH value of 10 and ambient temperature. The results suggest that the eXtreme Gradient Boosting model provides good accuracy and predictive performance, with R2 values of 0.9923 and 0.9783 for KLa and η, respectively. The machine learning models developed in this study are combined with experimental results to provide more comprehensive information on rotating packed bed operations and more accurate predictions of KLa and η. The information mining behind the model is an important reference for the rational design of high-gravity-field-coupled ammonia stripping projects.

The United Nations (UN) sustainable development goal (SDGs) # 6 is about “Clean Water and Sanitation”. The world is thriving towards the milestone that everyone accesses improved sanitation. Safely managed sanitation however goes beyond and is a matter of hygiene, health, dignity, and human rights. In 2010, the UN General Assembly explicitly recognized the human right to access improved sanitation. In 2020, 3.6 billion people lacked safely managed services. These include 1.9 billion people with access to basic services, 580 million with limited services, 616 million using unimproved sanitation facilities, and 494 million who still practice open defecation.Access to a toilet and primary treatment options septic tanks and soak-pits is the starting point of a healthy sanitation system. Countries like China and India have built millions of toilets in the past few years, especially in rural areas, to end open defecation and provide a healthy living environment. However, building a toilet is just the first step to establish a safely managed, environmentally-friendly sanitation system. A huge area of focus is the wastewater excretion from the sewage system. This wastewater needs to be appropriately managed, and valuable resources need to be recovered. Globally, more than 80 percent of wastewater returns to the environment without any treatment. In some countries of the Global South, the share is as high as 95%. This is a major issue that leads to unsanitary living conditions and the spread of damaging diseases.Infrastructure such as conventional centralized sewerage systems is assumed normality in the Global North. In the Global South where on-site sanitation systems are most prevalent, the management of fecal sludge and other non-sewered sanitation systems (NSSS) has started to emerge as considered optimal in view that the conventional solution is expensive and water-intensive. This Research Topic aims to identify and establish an alternative sanitation system that is affordable and accessible to the Global South, to mitigate the spread of disease and provide a healthier living environment.Further maintenance must never be neglected to sustain the functioning of the sanitation systems. Public awareness needs to be cultivated towards optimal sanitation behavior and move towards financial sustainability. Nowadays, the worldwide intention is to develop and establish non-conventional sanitation systems that could function well and meet the SDGs. For instance, Bill & Melinda Gates Foundation launched the Reinvent the Toilet Challenge to stimulate the development of new toilet technologies that safely and effectively manage human waste. In China and India, on the other hand, Faecal Sludge Management (FSM) is gaining traction and being rapidly deployed in many states.This collection hopes to highlight the sanitary issues in the current world and new methods and strategies to optimize sanitation systems efficiently. This collection seeks high-quality works and topics focusing on the following aspects of sanitation:• Economically viable methods to optimize conventional centralized sanitation systems in a low/mid-income setting as the major portion of public funding goes into establishing and managing centralized conventional sanitation systems.• Techno-financial and environmental viability of non-sewered sanitation system (NSSS)• Water-saving technologies and strategies in sanitation systems, including optimizing water management and saving water (examples include vacuum toilet, dry toilet, reclaimed flushing water toilet, as well as reinvented toilet challenge by Bill & Melinda Gates Foundation)• Energy- and resource recovery from sanitation systems, including nutrient recovery, blackwater/greywater/yellow water, fecal sludge, and urine source separating system.• Sustainable technological solutions in WASH (water, sanitation, and hygiene) where sustainability is understood in relation to social, economic, and environmental and political aspects. This may include a life cycle assessment of sanitation systems.• Sanitation technological and institutional solutions for low-income areas.• Engineering education and sustainability concerns in WASH.

Novel bio-magnetic membrane capsules (BMMCs) were prepared by a simple two-step titration-gel cross-linking method using a polyvinyl alcohol (PVA) and sodium alginate (SA) matrix to control the disintegration of phytogenic magnetic nanoparticles (PMNPs) in an aqueous environment, and their performance was investigated for adsorbing cationic malachite green (MG) dye from water. The prepared BMMCs were characterized by FTIR, powder XRD, SEM, EDX, XPS, VSM and TGA techniques. The findings revealed that the hysteresis loops had an excellent superparamagnetic nature with saturation magnetization values of 11.02 emu g−1. The prepared BMMCs not only controlled the oxidation of PMNPs but also improved the adsorptive performance with respect to MG dye (500 mg g−1 at 298.15 K and pH 6.5) due to the presence of a large amount of hydrophilic functional groups (hydroxyl/–OH and carboxyl/–COOH) on/in the BMMCs. The smooth encapsulation of PMNPs into the PVA–SA matrix established additional hydrogen bonding among polymer molecular chains, with improved stability, and adsorptive performance was maintained over a wide range of pH values (3–12). Importantly, the prepared BMMCs were easily regenerated just by washing with water, and they could be re-utilized for up to four (4) consecutive treatment cycles without observing any apparent dissolution of iron/Fe0 or damage to the morphology. According to the mass balance approach, an estimated amount of 100 mL of treated effluent can be obtained from 160 mL of MG dye solution (25 mg L−1) just by employing a 0.02 g L−1 adsorbent dosage. Finally, a model of BMMCs based on zero-effluent discharge was also proposed for commercial or industrial applications. The prepared BMMCs are greatly needed for improving the water/wastewater treatment process and they can be utilized as an excellent adsorbent to remove cationic pollutants for various environmental applications.

Dwindling supplies of fossil fuel along with detrimental release of greenhouse gases have led to the quest for renewable sources of fuel such as bioethanol from cellulosic materials. Conversion of biomass to bioethanol involves a set of “biotransformation” and “recovery/concentration” processes. With the help of membrane technology, several process steps that were conventionally separate can be integrated and the production of bioethanol simplified. In addition to efficient recovery of bioethanol, this can facilitate removal of inhibitory side products from the fermentation broth and recovery of the inhibitory but valuable side products. This chapter provides a critical review of the application of membrane technology in various steps of bioethanol production. The challenges to widespread deployment of full-scale bioethanol facilities equipped with membranes have also been outlined.

This study investigates the microbial community composition, in the biofilms grown on two different support media in fixed biofilm reactors for aerobic wastewater treatment, using next generation sequencing (NGS) technology.The chemical composition of the new type of support medium (TDR) was found to be quite different from the conventionally used support medium (Stone).The analysis of 16S rRNA gene fragments recovered from the laboratory scale biofilm system show that biofilm support media and temperature conditions influence bacterial community structure and composition. Greater bacterial diversity was observed under each condition, primarily due to the large number of sequences available and sustenance of rare species. There were 6 phyla found, with the highest relative abundance shown by the phylum Proteobacteria (52.71%) followed by Bacteroidetes (33.33%), Actinobacteria (4.65%), Firmicutes, Verrucomicrobia (3.1%) and Chloroflex (>1%). The dataset showed 17 genera of bacterial populations to be commonly shared under all conditions, suggesting the presence of a core microbial community in the biofilms for wastewater treatment. However, some genera in the biofilms on TDR were observed in high proportions, which may be attributed to its chemical composition, explaining the improved level of wastewater treatment. The findings show that the structure of microbial communities in biofilm systems for wastewater treatment is affected by the properties of support matrix.

The occurrence of emerging or newly identified contaminants in water resources is becoming a great concern for public health. The worldwide freshwater scarcity is also increasing. These have resulted in rapid growth in the demand for nonconventional water resources and sophisticated approaches to wastewater treatment. Existing conventional water treatment plants were not designed for these emerging contaminants. Therefore, new approaches to wastewater treatment are required. Among the most promising processes for various types of wastewater treatment and water reuse, membrane-assisted technologies have been accepted as suitable and reliable in different applications of water reuse. This chapter discusses the application of membrane processes and membrane-assisted technologies in wastewater treatment and water reuse. The chapter mainly focuses on membrane bioreactors (MBRs), including a comparison between conventional activated sludge processes and MBRs. Emerging membrane-assisted technologies are also discussed.

Graphene oxide (GO), as an emerging material, exhibits extraordinary performance in terms of water treatment. Adsorption is a process that is influenced by multiple factors and is difficult to simulate by traditional statistical models. Artificial neural networks (ANNs) can establish highly accurate nonlinear functional relationships between multiple variables; hence, we constructed a three-layered ANN model to predict the removal performance of Cu(II) metal ions by the prepared GO. In the present research work, GO was prepared and characterized by FT-IR spectroscopy, SEM, and XRD analysis techniques. In ANN modeling, the Levenberg–Marquardt learning algorithm (LMA) was applied by comparing 13 different back-propagation (BP) learning algorithms. The network structure and parameters were optimized according to various error indicators between the predicted and experimental data. The hidden layer neurons were set to be 12, and optimal network learning rate was 0.08. Contour and 3-D diagrams were used to illustrate the interactions of different influencing factors on the adsorption efficiency. Based on the results of batch adsorption experiments combined with the optimization of influencing factors by ANN, the optimum pH, initial Cu(II) ion concentration and temperature were anticipated to be 5.5, 15 mg L−1 and 318 K, respectively. Moreover, the adsorption experiments reached equilibrium at about 120 min. Combined with sensitivity analysis, the degree of influence of each factor could be ranked as: pH > initial concentration > temperature > contact time.

The health risk of organic micro pollutants in water is yet to be comprehensively established. However, the persistence of these pollutants in the environment as a result of continuous discharge even at trace concentrations is considered to pose major environmental concerns. Advance treatment methods such as membrane-assisted processes (MAPs) are potential technologies capable of removing a wide range of these organic micropollutants (OMPs) detected in water. Tight membranes as regards pore size are reported to be more efficient than loose membranes mainly because of the removal mechanism involved, which is mainly influenced by the properties of the membrane and the pollutants in relation to solute–solute and solute–membrane interaction. The study and application of membrane processes to water and wastewater treatment have grown significantly in the last decade. Membrane processes application is diverse and flexible enough to allow adaptation into other physicochemical processes. Integration and hybridization of membrane processes with other physicochemical processes and natural systems are becoming a more economical and sustainable option for removal of OMPs. Nevertheless, there are shortfalls in the industrial application of membrane-assisted technologies. This paper reviews and assesses the applicability of various MAPs applied for the removal of OMPs from water and wastewater streams.

Due to the increasing freshwater deterioration and demand for irrigation, there is pressing need to reclaim and reuse wastewater for agricultural operations. While this practice is gaining significant traction in developed world, it is quite rare in most developing countries with inadequate or no functional sewerage facilities and treatment systems at both municipal and industrial levels occasioned by high investment and operational costs. Consequently, wastewaters generated are in complex heterogenous mix of industrial, domestic, municipal and agricultural runoff wastewater. Biological technologies which utilize the expertise of microorganisms are considered robust, efficient and economically attractive for treatment of wide range of wastewaters and they have high suitability in developing countries. This work therefore assessed the potential of suspended growth biological process (SGBP) for reclamation and reuse of mixed wastewater composed a mixture of domestic effluent, pharmaceutical, textile, petroleum discharges and agricultural runoff for irrigation of edible crops (lettuce and beets) with plants phenological parameters as measuring indicators. The germination and phenological characteristics of crops were studied in a hydroponic unit under four irrigation regimes: tap water as control, mixed wastewater, SGBP treated wastewater, and tap water mixed with nutrient solution as upper control, for a duration of 45-d. The results proved that the SGBP treated wastewater had no negative impact on germination responses of the seed crops. However, residual recalcitrant compounds caused early stunted growth in plant root systems with resultant limited access to nutrients. Consequently, plant vegetative growth and phenological development as well as chlorophyll production were reduced. In comparison to nutrients supplemented solution, nutrients deficiency and imbalance in treated wastewater contributed to the poor development in irrigated plants. The outcomes of seed germination and plant growth experiments show a positive indication for reuse of mixed wastewater in agriculture. However, there is need for further research to explore the long-term benefits and limitations of reusing such treated wastewater.

P recovery from wastewater treatment plants (WWTPs) as struvite fertiliser is a recognised method of improving P use efficiency and reducing P losses into the environment. The main driver for P recovery from the water industry viewpoint is the reduction in the nuisance of struvite clogging inside pumps and pipes. Struvite recovery leads to an average P recovery rate of 72 ± 7% from centrifuge centrate, with 8.8 ± 0.7% total P and 20.5 ± 3.2% PO4-P removed from the WWTP influent as struvite. This reduces the potential for struvite precipitation, moderates P loads on biological nutrient removal processes and lowers P concentration in the final effluent. Totalling revenue from sale of struvite and operational site savings, P recovery becomes an attractive option for water companies. The implementation of P recovery technologies to produce struvite fertiliser in all UK WWTPs could produce a national P fertiliser source of 7.05 ± 2.01 kt P/year. In addition, sludge produced at WWTPs could be diverted to advanced energy recovery (AER) processes and P recovered from AER residues; up to 21.71 ± 0.95 kt P/year could be recovered in this way in the UK. Combining the two methods of P recovery, UK imports of P fertiliser could be reduced by 36.2 ± 1.1%. P recovery on a large scale has the further benefit of protecting against eutrophication by reducing P emissions to water bodies by 21.7 ± 1.9%. The protection of the environment and reduction in reliance on imported P are major national motivations to legislate P recovery from waste.

Membrane bioreactors (MBRs) have been increasingly employed for municipal and industrial wastewater treatment in the last decade. The efforts for modelling of such wastewater treatment systems have always targeted either the biological processes (treatment quality target) as well as the various aspects of engineering (cost effective design and operation). The development of Activated Sludge Models (ASM) was an important evolution in the modelling of Conventional Activated Sludge (CAS) processes and their use is now very well established. However, although they were initially developed to describe CAS processes, they have simply been transferred and applied to MBR processes. Recent studies on MBR biological processes have reported several crucial specificities: medium to very high sludge retention times, high mixed liquor concentration, accumulation of soluble microbial products (SMP) rejected by the membrane filtration step, and high aeration rates for scouring purposes. These aspects raise the question as to what extent the ASM framework is applicable to MBR processes. Several studies highlighting some of the aforementioned issues are scattered through the literature. Hence, through a concise and structured overview of the past developments and current state-of-the-art in biological modelling of MBR, this review explores ASM-based modelling applied to MBR processes. The work aims to synthesize previous studies and differentiates between unmodified and modified applications of ASM to MBR. Particular emphasis is placed on influent fractionation, biokinetics, and soluble microbial products (SMPs)/exo-polymeric substances (EPS) modelling, and suggestions are put forward as to good modelling practice with regard to MBR modelling both for end-users and academia. A last section highlights shortcomings and future needs for improved biological modelling of MBR processes.

Water scarcity, pertaining to many interrelated issues e.g. rapid urbanisation and increasing water pollution, has been acknowledged around the world. Water reuse has emerged as a viable water conservation measure to satisfy water demand in many communities. Among the diversity of wastewater treatment processes, membrane assisted treatment technologies have been employed for different water reuse scenarios. In this regard, one of the most critical problems is how to select an appropriate membrane technology for a water reuse scenario. This research therefore develops a decision making framework for selection of wastewater treatment technology. The framework is applied to different non-potable reuse scenarios in South African cities and suburban areas by employing a multi criteria analysis method. The results show that this approach is able to provide a systematic and rigorous analysis which can help in comparing and selecting wastewater technologies.

Current industrial livestock production has one of the highest consumptions of water, producing up to ten times more polluted (biological oxygen demand, BOD) wastewaters compared to domestic sewage. Additionally, livestock production grows yearly leading to an increase in the generation of wastewater that varies considerably in terms of organic content and microbial population. Therefore, suitable wastewater treatment methods are required to ensure the wastewater quality meets EU regulations before discharge. In the present study, a combined lab scale activated sludge-filtration-ozonation system was used to treat a pre-treated abattoir wastewater. A 24-h hydraulic retention time and a 13-day solid retention time were used for the activated sludge process, followed by filtration (4–7 μm) and using ozone as tertiary treatment. Average reductions of 93% and 98% were achieved for chemical oxygen demand (COD) and BOD, respectively, obtaining final values of 128 mg/L COD and 12 mg/L BOD. The total suspended solids (TSS) average reduction reached 99% in the same system, reducing the final value down to 3 mg/L. Furthermore, 98% reduction in phosphorus (P) and a complete inactivation of total coliforms (TC) was obtained after 17 min of ozonation. For total viable counts (TVC), a drastic reduction was observed after 30 min of ozonation (6 log inactivation) at an injected ozone dose of 71 mg/L. The reduction percentages reported in this study are higher than those previously reported in the literature. Overall, the combined process was sufficient to meet discharge requirements without further treatment for the measured parameters (COD, BOD, TSS, P, TC and TVC).

The present study evaluated the effectiveness and durability of TDR for biofilm development and related long term usage in fixed biofilm reactors for wastewater treatment. TDR incubated (30±2ºC) with activated sludge showed comparatively higher biofilm development (0.51g) under aerobic than under anaerobic (0. 42g) conditions after 7 weeks. During biofilm succession, a significant shift in bacterial community was observed from pathogenic to autotrophic after 4 weeks. The decreasing bacterial count (MPN index) ( 80%) (E .coli and feacal coliforms) and COD, and BOD (70% approx.) depicted diminishing organic load in sludge. While, changes in pH and nutrients like NO2-, NO3-, PO43-and SO32- indicated presence of other key-bacterial species with efficient nutrient consuming abilities in biofilm. Scanning Electron Microscopy showed few aberration and rich bacterial growth on treated TDR. Furthermore, detailed analysis through FTIR spectroscopy confirmed minor transformation in TDR under anaerobic conditions. TDR proved to be considerably durable and cost effective support material that can be used in aerobic fixed biofilm reactors for wastewater treatment. However, operational conditions of the reactor should be optimized to keep the biofilm structure intact and for achieving desired wastewater treatment efficiency.

The hydrolytic step is usually considered the rate limiting step in the biological conversion of ligno-cellulose material into biofuels. Current optimization approach attempts to understand the mechanism of hydrolysis in order to boost production. In this study, the development and testing of a surface-based and a water-based-diffusion kinetic model for modeling biogas production from cow manure was conducted using total solid (TS) loading ranging from 8 to 10% (TS) in batch reactors. Parameter estimation using solver function of the Microsoft Excel Tool Pak revealed that, the second order water diffusion model was superior in predicting biogas production with correlation coefficients ranging from 0.9977 to 0.9995. In addition, the initial surface permeability flux of water (Kspf0) into the organic biomass and fragmentation of particles were observed to be independent events elicited by the action C1 and Cx factors respectively. The initial surface permeability flux of water was observed to increase as solids concentration increased from 8 to 9%TS while, fragmentation constants decreased. Maximum initial surface permeability flux of water (1.78E-05 m3/m2/day) was observed at 9% (TS) with a simultaneous minimization in the fragmentation rate (0.13/day). For optimal production of biofuels, appropriate quantity of C1-factor, the degree of crystallinity and particle size may be critical for efficient conversion.

Nitrification is an integral part of biological nitrogen removal processes and usually the limiting step in wastewater treatment systems. Since nitrification is often considered not feasible at temperatures higher than 40 °C, warm industrial effluents (with operating temperatures higher than 40 °C) need to be cooled down prior to biological treatment, which increases the energy and operating costs of the plants for cooling purposes. This study describes the occurrence of thermophilic biological nitrogen removal activity (nitritation, nitratation, and denitrification) at a temperature as high as 50 °C in an activated sludge wastewater treatment plant treating wastewater from an oil refinery. Using a modified two-step nitrification-two-step denitrification mathematical model extended with the incorporation of double Arrhenius equations, the nitrification (nitrititation and nitratation) and denitrification activities were described including the cease in biomass activity at 55 °C. Fluorescence in situ hybridization (FISH) analyses revealed that Nitrosomonas halotolerant and obligatehalophilic and Nitrosomonas oligotropha (known ammonia-oxidizing organisms) and Nitrospira sublineage II (nitrite-oxidizing organism (NOB)) were observed using the FISH probes applied in this study. In particular, this is the first time that Nitrospira sublineage II, a moderatedly thermophilic NOB, is observed in an engineered full-scale (industrial) wastewater treatment system at temperatures as high as 50 °C. These observations suggest that thermophilic biological nitrogen removal can be attained in wastewater treatment systems, which may further contribute to the optimization of the biological nitrogen removal processes in wastewater treatment systems that treat warm wastewater streams.

The paper discusses the experimental optimisation of both chemical and mechanical cleaning procedures for a flat-sheet submerged membrane bioreactor fed with municipal wastewater. Fouling was evaluated by means of the critical flux concept, which was experimentally measured by short-term flux-stepping tests. By keeping constant most important parameters of the biological process (MLSS, sludge age), two different chemical cleaning protocols (2,000 mg L(-1) NaOCl and 200 mg L(-1) NaOCl) were applied with different frequency and, after approximately 9 months of operation, the criticality threshold was determined under different values of SAD(m) (specific aeration demand per unit of membrane surface area). The weaker and more frequent chemical cleaning regime (200 mg L(-1), monthly) proved much more effective than the stronger and less frequent strategy (2,000 mg L(-1), once every three months). The improvement of performances was quantified by two TMP-based parameters, the fouling rate and the DeltaTMP (difference between TMP values during the increasing and decreasing phase of hysteresis). The best performing configuration was then checked over a longer period by running four long-term trials showing an exponential trend of the sub-critical fouling rate with the imposed flux.

The major obstacle for membrane bioreactors (MBRs) to become a widely applicable technology is the membrane fouling. Despite the fact that the fouling is inevitable, understanding of the inherent mechanisms and subsequent integrated modeling of the process seems greatly helpful for optimization and control. Several researches have shown the importance of extra-cellular polymeric substances (EPS) their role in explaining the two-step with sudden jump in TMP vs. time. But, the crucial point remains about the prediction of the EPS concentration in the dynamic MBR sludge matrix and the research attention becomes bit more on biological behavior of the sludge matrix in order to have 'an integrated complete dynamic model' describing both filtration and biological behavior simultaneously. Moreover, on account of operational and fundamental difference from conventional wastewater treatment processes, MBRs possess distinct biological dynamics and hence the activated sludge models (ASMs: ASM1, ASM3, etc. [4]) in their original form are not expected to be workable. Therefore, the two-fold idea has been suggested and used for simulation herein are (i) improved version of ASM3 as suggested by Sin et al. [16] seems promising in order to explain the distinct MBR biological process dynamics, and (ii) EPS model which has a strong urge to be used as input to fouling model. The notion of 'complete model' provides a platform to infuse the researches from two different fields viz. biological process modeling and filtration modeling for MBRs application in a harmonized way and hence provokes interconnected investigations from both the fields

This review concentrates on the effect of activated carbon (AC) addition to membrane bioreactors (MBRs) treating wastewaters. Use of AC-assisted MBRs combines adsorption, biodegradation and membrane filtration. This can lead to advanced removal of recalcitrant pollutants and mitigation of membrane fouling. The relative contribution of adsorption and biodegradation to overall removal achieved by an AC-assisted MBR process can vary, and “biological AC” may not fully develop due to competition of target pollutants with bulk organics in wastewater. Thus periodic replenishment of spent AC is necessary. Sludge retention time (SRT) governs the frequency of spent AC withdrawal and addition of fresh AC, and is an important parameter that significantly influences the performance of AC-assisted MBRs. Of utmost importance is AC dosage because AC overdose may aggravate membrane fouling, increase sludge viscosity, impair mass transfer and reduce sludge dewaterability.

This research compares and contrasts the physical and chemical characteristics of incinerator sewage sludge ash (ISSA) and pyrolysis sewage sludge char (PSSC) for the purposes of recovering phosphorus as a P-rich fertiliser. Interest in P recovery from PSSC is likely to increase as pyrolysis is becoming viewed as a more economical method of sewage sludge thermal treatment compared to incineration. The P contents of ISSA and PSSC are 7.2–7.5% and 5.6%, respectively. Relative to the sludge, P concentrations are increased about 8-fold in ISSA, compared to roughly 3-fold in PSSC. Both PSSC and ISSA contain whitlockite, an unusual form of calcium phosphate, with PSSC containing more whitlockite than ISSA. Acid leaching experiments indicate that a liquid/solid ratio of 10 with 30 min contact time is optimal to release PO4-P into leachate for both ISSA and PSSC. The proportion of P extracted from PSSC is higher due to its higher whitlockite content. Heavy metals are less soluble from PSSC because they are more strongly incorporated in the particles. The results suggest there is potential for the development of a process to recover P from PSSC.

Wastewater Treatment (WWT) for water reuse applications has been accepted as a strategic solution in improving water supplies across the globe; however, there are still various challenges that should be overcome. Selection of practical solutions is then required whilst considering technical, environmental, socio-cultural, and financial factors. In this study, a multi expert decision support tool that considers a variety of evaluation criteria is proposed to provide a ranking system for competing advanced WWT technologies in terms of their performance. Two scenarios of water reuse in the contexts of Brazil and Greece are defined, and evaluation is undertaken based on opinions of water reuse experts. The results prove that the tool would successfully facilitate rigorous and methodical analysis in evaluation of WWT technologies for water reuse applications with potential for use under various sets of evaluation criteria, WWT technologies and contexts.

Brick-manufacturing is an intensive water-consuming industry that requires a sustainable and integrated water management strategy to reduce reliance on freshwater consumption. This study aims to develop a rigorous analytical tool based on water footprint principles and water pinch analysis techniques that can be used to manage and optimise water consumption. By performing thorough water audits, the water consumption footprint (the sum of blue and green water footprints) and the theoretical water pollution footprint (grey water footprint) were quantified. The total water consumption footprint of a brick is determined as 2.02 L, of which blue water is identified as 1.71 L (84.8%) and green water as 0.31 L (15.2%). The theoretical grey water footprint of a brick was found to be 1.3 L, a value that would have been higher if in-situ wastewater treatment had not been operated before effluent discharge. In order to reduce the water footprint of a brick, water pinch analysis techniques were applied for the brick-manufacturing processes. Two water recovery schemes were explored, i.e. direct re-use/recycle and water regeneration. For the former, water targeting was first carried out using the material recovery pinch diagram. Next, an algebraic technique was utilised for the targeting of water regeneration, where an interception unit is used to partially purify the water sources for further re-use/recycle. The network that fulfils the water flow rate targets was then designed using the nearest neighbour algorithm. The calculation indicates that direct re-use/recycle scheme reduces with the standard water consumption footprint reduced only by 15.6%. Water regeneration scheme, on the other hand improved the current value (which relies on an unsystematic water regeneration scheme) by 56.4%. The analysis clearly shows that the water consumption footprint of a brick is improved when the brick-manufacturing industry operates sustainable water management strategies. This study, a first of its kind, demonstrates that integration of water pinch analysis coupled with water footprint concepts, provides a robust and effective tool for the manufacturing industries that aim for sustainable water consumption.

This research investigates surface coated ultrafiltration (UF) polyvinylidene fluoride (PVDF) hollow fiber membrane for the removal of organic micropollutants (OMPs) in water. Coating of PVDF membranes with Poly (1-phenylethene-1,2-diyl) - Polystyrene solution through physical adsorption was carried out under two modes, ‘dipped’ and ‘sprayed’. The performance of the coated membrane in the rejection of model organic micropollutants, caffeine and carbamazepine spiked in deionised water (at 300 g/L and 500 g/L), correlated with the coating methods used. Dipped coated membrane showed a better removal of recalcitrant hydrophobic carbamazepine compared to the ‘sprayed’ coated membrane; while for both methods of coating, removal of caffeine was relatively insignificant. Inferably, hydrophobic interaction and size exclusion may be the major removal mechanism involved in the rejection by the coated membranes. The coating layer potentially enhanced reduction of pore size with resulting effect on membrane permeability and providing more sites for possible hydrophobic interaction.

This study is aimed at exploring strategies for mineralization of refractory compounds in distillery effluent by anaerobic biodegradation/ozonation/aerobic biodegradation. Treatment of distillery spent-wash used in this research by anaerobic-aerobic biodegradation resulted in overall COD removal of 70.8%. Ozonation of the anaerobically treated distillery spent-wash was carried out as-is (phase I experiments) and after pH reduction and removal of inorganic carbon (phase II experiments). Introduction of the ozonation step resulted in an increase in overall chemical oxygen demand (COD) removal, with the highest COD removals of greater than 95% obtained when an ozone dose of approximately 5.3 mg ozone absorbed/mg initial total organic carbon was used. The COD removal during phase II experiments was slightly superior compared with phase I experiments at similar ozone doses. Moreover, efficiency of ozone absorption from the gas phase into distillery spent-wash aliquots was considerably enhanced during phase II experiments.

Current research is based on an innovative approach of the fabrication of encapsulated sustainable, green, phytogenic magnetic nanoparticles (PMNPs), to inhibit the generation of secondary pollutants (Iron/Feo) during water treatment applications. These novel bio-magnetic membrane capsules (BMMCs) were prepared using two-step titration gel crosslink method, with polyvinyl alcohol and sodium alginate matrix as the model encapsulating materials to eliminate potentially toxic metals (Pb2+ and Cd2+) from water. The development of BMMCs was characterized by FTIR, XRD, XPS, SEM, VSM, TGA and EDX techniques. The effects of various operating parameters, adsorbent dose, contact time, solution pH, temperature, initial concentration of metals cations and co-existing ions were studied. The hysteresis loops have illustrated an excellent super-paramagnetic nature, demonstrating the smooth encapsulation of PMNPs without losing their magnetic properties. The maximum monolayer adsorptive capacities estimated at pH 6.5 by the Langmuir isotherm model were 548 and 610.67 mg/g for Pb2+ and Cd2+, respectively. The novel BMMCs did not only control oxidation of PMNPs but also sustained the adsorptive removal over a wide range of pH (3–8), and the electrostatic interaction and ion-exchange were the core adsorption mechanisms. The BMMCs could easily be regenerated using 25% HNO3 as an eluent for successful usage in seven repeated cycles. Therefore, the BMMCs as a material can be used as an excellent sorbent or composite material to remove toxic metals Pb2+ and Cd2+, showing strong potential for improving water and wastewater treatment technologies.

The anaerobic co-digestion of cow manure and waste paper at ambient temperature condition was observed to be optimized at a mix proportion of 75:25 respectively. The development and testing of a set of simplified anaerobic digestion models (SADM's) for this mixture revealed that the Hill's based biogas yield rate model was most appropriate in describing the kinetics of biogas production. Parameter estimation using non-linear regression revealed that the half saturation constants expressed as acidified substrate and volatile solids equivalents were 0.228. g/L and 5.340. g. VS/L respectively, and the maximum specific biogas yield rate and biodegradability were 2.2. mL/g. VS/day and 0.313 respectively. The coefficients ". n" and ". m" indicative of acidogenic bacterial adaptation for degradation and acetogenic/methanogenic bacterial cooperativity were estimated to be 1.360 and 2.738 respectively, while hydrolysis/acidogenesis was considered the rate limiting step. The need of bacterial adaptation may be an important factor to consider during anaerobic modelling of complex biomass. © 2013 Elsevier B.V.

This study investigates the simultaneous removal of Escherichia coli and metals (Pb, Cd and Zn) in a continuous flow system and provides an insight into the mechanisms involved during bacterial cells kill when in contact with silver-modified zeolite. Results showed complete disinfection and metal removal at 570 min contact time, thereafter E. coli breakthrough followed by Cd and Zn at 1080 min. Due to the zeolite’s high selectivity for Pb removal, no breakthrough was observed up to 7920 min run time. Column performance was influenced by changes in flow rate and bed height, as breakthrough occurred at 240 min when the flow rate was increased from 2 to 5 mL/min and the bed height decreased from 1 to 0.5 cm. Morphological characterization of treated cells revealed extensive damage and synthesis of nano- and micro-sized silver particles as a part of their defence mechanism. The treated effluent was passed through a non-modified zeolite column with 98% silver recovery achieved. This study showed the capability of this system to simultaneously handle bacterial and heavy metals contamination while providing an insight into the mechanism of disinfection via complex E. coli-silver ion interactions that occur during treatment and demonstrating the potential of silver recovery for reuse.

This research work evaluated the biofilm succession on stone media and compared the biochemical changes of sludge in attached and suspended biological reactors operated under aerobic and anaerobic conditions. Stones incubated (30 ± 2°C) with activated sludge showed a constant increase in biofilm weight up to the fifth and seventh week time under anaerobic and aerobic conditions, respectively, where after reduction (>80%) the most probable number index of pathogen indicators on ninth week was recorded. Reduction in parameters such as biological oxygen demand (BOD) (47.7%), chemical oxygen demand (COD, 41%), nitrites (60.2%), nitrates (105.5%) and phosphates (58.9%) and increase in dissolved oxygen (176.5%) of sludge were higher in aerobic attached growth reactors as compared with other settings. While, considerable reductions in these values were also observed (BOD, 53.8%; COD, 2.8%; nitrites, 28.6%; nitrates, 31.7%; phosphates, 41.4%) in the suspended growth system under anaerobic conditions. However, higher sulphate removal was observed in suspended (40.9% and 54.9%) as compared with biofilm reactors (28.2% and 29.3%). Six weeks biofilm on the stone media showed maximum physiological activities; thus, the operational conditions should be controlled to keep the biofilm structure similar to six-week-old biofilm, and can be used in fixed biofilm reactors for wastewater treatment.

BACKGROUND This research is focused on the effect of temperature on the growth of active biofilms on polypropylene (PP) filter media in aerobic fixed biofilm reactors (FBR) for wastewater treatment. RESULTS High‐throughput sequencing was used to explore the composition and diversity of the microbial community of 14‐days old (starting phase) biofilms grown at 10, 20 and 30°C. Members of the classes Proteobacteria, Bacteroidetes, and Firmicutes were predominant in all the biofilm samples retrieved from PP‐FBRs. A total of 108 genera of bacteria were identified, with some of them present in all three reactors, including Trichococcus, Zoogloea, Aeromonas, Acidovorax, and Malikias, among others. Besides these shared populations, certain genera were abundantlyfound in individual biofilm samples, like Brevundimonas (17.1%), Chitinimonas (10.3%) and Roseateles (39.3%), at 10, 20, and 30°C, respectively. The metabolic capabilities of active microbial communities in PP‐FBRs were estimated by assessing the changes in different variables (BOD, DO, and pH) in the influent and effluent during operation. A note worthy BOD removal (66.6%) was shown by PP‐FBRs operating at 30°C, as compared to 20°C (28.3%) and 10°C (28.8%),consistent with the DO levels recorded in the effluents, highest at 30°C (70.5%), and decreasing with the declining temperatures. Substantial wastewater treatment efficiencies were observed in the reactors at 30°C, attributable to the higher relative and diversity of microbial biofilms. CONCLUSIONS The development of physiologically active biofilms in PP at all prevailing temperatures strongly suggests that the material is suitable to be employed in FBRs for wastewater treatment at different operational temperatures.

Method, and plant thereof, for reducing the amount of surplus sludge produced in a wastewater treatment plant, the sludge comprises an organic matrix with a solid fraction and a cellular fraction; the method comprises : a) reducing the dimensions of the components of the solid and cellular fractions; and b) hydrolysis - at room temperature - of the components of the solid and cellular fractions having dimensions reduced in step a). L'invention porte sur un procédé et sur une installation pour la mise en oeuvre de celui-ci, pour réduire la quantité de boue en surplus produite dans une installation de traitement des eaux résiduaires, la boue comprenant une matrice organique avec une fraction solide et une fraction cellulaire. Le procédé comprend : a) la réduction des dimensions des composants des fractions solide et cellulaire ; et b) l'hydrolyse - à la température ambiante - des composants des fractions solide et cellulaire ayant des dimensions réduites à l'étape a).

The aim of the present study is to assess the wastewater treatment efficiency of a low-cost pilot-scale trickling filter (TF) system under a prevailing temperature range of 12 °C–38 °C. Operational data (both influent and effluent) for 330 days were collected from the pilot-scale TF for various physicochemical and biological parameters. Average percentage reductions were observed in the ranges of 52–72, 51–73, 61–81, and 74–89% for BOD5, COD, TDS, and TSS, respectively, for the whole year except the winter season, where a 74–88% reduction was observed only for TSS, whilst BOD5, COD, and TDS demonstrated reductions in the ranges of 13–50, 13–49, and 23–61%, respectively. Furthermore, reductions of about 43–55% and 57–86% in fecal coliform count were observed after the 1st and 6th day of treatment, respectively, throughout study period. Moreover, the pilot-scale TF model was based on zero-order kinetics calibrated at 20 °C using experimental BOD5 data obtained in the month of October to calculate the k20 value, which was further validated to determine the kt value for each BOD5 experimental setup. The model resulted in more accurate measurements of the pilot-scale TF and could help to improve its ability to handle different types of wastewater in the future.

The deposition of solid phosphorus-based mineral particles is a common problem in urine diversion systems, which occurs in transport systems, particularly in horizontal pipelines. In this work, particle deposition behaviour in turbulent flow in a 3D horizontal pipe was simulated by using the Euler–Lagrange method. The effects of particle diameter, particle density, particle shape factor and fluid flow velocity on particle deposition behaviour were investigated. The results showed that the deposition rate increased by 9.92%,6.88% and 6.88% with increasing particle diameter (10-90 μm), particle density (1400 kg/m3–2300 kg/m3), and particle shape factor (0.2–1), respectively. For particles with larger diameters (>90 μm) or larger density (>2300 kg/m3), the deposition rate of these particles was almost reached 100%. It was found that gravitational sedimentation was the dominant deposition mechanism in low fluid flow velocity range (0.1–0.5 m/s). As fluid flow velocity increased (>0.5 m/s), turbulent fluctuation became the dominant factor that affected particle motion behaviour, whereas the effect of gravitational sedimentation on particle deposition behaviour declined significantly, and the increase in fluid flow velocity no longer significantly affects deposition rate. It was found that the deposition rate decreased by 29.13% as the fluid flow velocity was increased from 0.1 m/s to 0.5 m/s, while the corresponding deposition rate only decreased by 14.24% when the fluid flow velocity was increased from 0.5 m/s to 2 m/s. The optimal flow velocity was found to range between 0.75 and 1.25 m/s, which may mitigate the deposition of mineral solids in urine diversion systems.

The urgent need to reduce the environmental burden of antibiotic resistance genes (ARGs) has become even more apparent as concerted efforts are made globally to tackle the dissemination of antimicrobial resistance. Concerning levels of ARGs abound in sewage sludge and animal manure, and their inadequate attenuation during conventional anaerobic digestion (AD) compromises the safety of the digestate, a nutrient-rich by-product of AD commonly recycled to agricultural land for improvement of soil quality. Exogenous ARGs introduced into the natural environment via the land application of digestate can be transferred from innocuous environmental bacteria to clinically relevant bacteria by horizontal gene transfer (HGT) and may eventually reach humans through food, water, and air. This review, therefore, discusses the prospects of using carbon- and iron-based conductive materials (CMs) as additives to mitigate the proliferation of ARGs during the AD of sewage sludge and animal manure. The review spotlights the core mechanisms underpinning the influence of CMs on the resistome profile, the steps to maximize ARG attenuation using CMs, and the current knowledge gaps. Data and information gathered indicate that CMs can profoundly reduce the abundance of ARGs in the digestate by easing selective pressure on ARGs, altering microbial community structure, and diminishing HGT.

The wastewater industry is under pressure to optimize performance of sewage treatment works (STW), while simultaneously reducing energy consumption. Using a process configuration selection matrix, this paper explores the practicability of placing a hypothetical cross flow structured plastic media (CFSP) trickling filter (TF) immediately ahead of an existing conventional trickling filter process (CTFP), without intermediate clarification. The viability of this configuration is subsequently demonstrated using an empirical multispecies TF model. This predicts the enhanced nitrification performance of the CTFP by simulating prior removals of biochemical oxygen demand (BOD). The model predictions propose that prior 50-80% BOD removals can allow for further reductions in effluent ammoniacal nitrogen (NH4-N) concentrations of 40-70%, respectively. This illustrates that adopting low energy TF technologies can eliminate the requirement for more energy intensive alternatives, such as submerged aerated filters (SAF). Moreover, this configuration maximizes the potential of existing assets, while simultaneously improving nitrification robustness when compared with tertiary nitrification processes.

This thesis addresses the major problem of high turbidity water in drinking water treatment to small rural and urban populations. This problem is attributed to polluted surface water sources and untreated piped water supply systems. In this research, the problem is addressed in the context of the Gilgit-Baltistan located in the extreme north of Pakistan, however, the solutions proposed may be applicable in other parts of the world with similar conditions of glacial melt water as a source for gravity fed drinking water delivery systems. Glaciers, lakes and seasonal snow deposits are the principal sources of all flowing water in the Gilgit-Baltistan (GB) region. High river water flows in summer, due to snow and glacial melt, which result in flooding and high turbidity water in almost all surface water sources in GB. Main surface drinking water sources in the region include rivers, lakes, springs and traditional drinking water channels and shallow water pits. Slow sand filter, due to the simple operational, maintenance requirements and high biological treatment efficiency is an attractive technology. However, due to its vulnerability to high suspended solids loadings this could not be applied in Gilgit-Baltistan, where more than 70% of the surface water sources has turbid water ranging from 500-3000 NTUs for 6 months (IUCN 2003). In order to cope with such water quality issues, dosing of a coagulant at upstream of the pre-filtration stage is commonly used worldwide. However, due to high costs and skilled personnel requirements, this is not suitable for small rural drinking water supply systems, such as in Gilgit-Baltistan. The successful use of gravel filters as pre-treatment have been investigated worldwide and in Gilgit-Baltistan, however, in few glacial water sources having finer particles conventional up-flow gravel filters failed to reduce turbidity levels up-to-the range suitable for slow sand filters. The objectives of this study were to: assess dirking water quality in rural and urban settlements, critically review of the physical characteristics of glacial water and to investigate efficiency as well as the effectiveness of up-flow gravel filters in series (UGFS) as pre-treatment in the context of Gilgit-Baltistan. In order to achieve the research aims an experimental plant was built at Mominabad, Hunza. The experimental plant was designed on the bases of the literature review, studies, past experience of up-flow roughing filters in GB and typical design guideline values for up-flow roughing filters. The experimental plant consisted of three series connected with the existing sedimentation tank. Each series was further divided into 3 sub-stages of up-flow filters, with different types, gradings, and depth of filter media. Different types of filter media used in the experimental plant consisted upon commercial charcoal, natural granite gravel, burnt bricks, natural limestone gravel and river bed gravel. The depth of filter media in each stage of the series was kept 0.9 m, with a different type of filter medium of 0.3 m depth. The filter compartment having burnt bricks, commercial charcoal, and limestone media were placed in different positions in each series. Water quality analysis was carried out for three months for turbidity levels revealed that 80 to 99 percent reduction in turbidity levels were achieved at the end of all URF-series in the experimental plant (p=0.000) Performance of burnt bricks, charcoal, and lime stone filter medium at first stage of the URF series coupled with granite filter medium in other sub-stages was found best in reducing turbidity levels of 340 NTUs and 939 NTUs in winter and summer seasons where 94 and 88 percent reduction was observed at outlet of the URF Stage-3 respectively A baseline water quality survey was carried out in the initial phase of the research to assess the bacteriological and physio-chemical quality of improved and traditional drinking water delivery systems, spring sources in rural and urban areas and proposed water source for the experimental plant in Mominabad Hunza. Grab samples were collected from selected representative points of the improved and traditional drinking water systems. Membrane filtration technique was used to assess bacteriological contamination in water samples. Conductivity, TDS, temperature, and pH was measured by a conductivity meter (Eutech Instruments, Cyberscan Con 11). Turbidity was measured by nephelometric turbidity tubes provided with Del-aqua water testing kit. Chemical analysis of urban drinking water supply systems and experimental plant site was analyzed on a spectrophotometer. The rural baseline results showed that with the exception of spring water, almost all the rural water supply systems and sources were biologically contaminated. Out of 284 samples, only 68 (24 %) samples had zero counts for E.coli in 100 mL sample and were fit for human consumption as per WHO Guideline Values (GVs) and National Standards Drinking Water Quality set by Government of Pakistan. (WHO, 2011; PEPA, 2008). Urban baseline water quality results showed that out of the 89 water samples, collected from different points of the urban water supply networks, 20 (22 %) samples were found to be fit for human consumption. However, chemical parameter in most of the cases were below the recommended guideline values of WHO (WHO, 2011) for drinking water in developing countries and National Drinking Water Quality Standards (PEPA, 2008), except in water samples taken from Gilgit town water supply networks, where the concentration of chromium, iron and nitrate was found on higher side as per the recommended values. The research revealed that almost all surface drinking water sources and piped water supply systems were not fit for human consumption with different degree of feacal contamination. High concentration of chromium, nitrite, and iron were observed in some urban drinking water sources. Experimental plant monitoring results indicated that up-flow multi-layer roughing filters in series was a suitable option for pretreatment under low flow rates for high turbidity glacier waters for community managed drinking water supply systems. Experimental plant results showed the effective removal of bacteriological (E.coli) and chemical (Nitrate, Nitrite, Phosphate, and Ammonia. Overall research results indicate that up-flow multi-layer roughing filter in series is a suitable option for pretreatment of highly turbidity glacial waters and is effective to remove bacterial and chemical contamination present in source water. URF-series-3, where burnt bricks, limestone and charcoal were placed in first stage of the series, reduced turbidity level higher than the other URF series. Research conclude that URF could be an appropriate and environment friendly option for rural water supply systems for glacial water sources, such as in Gilgit-Baltistan.

A large pilot-scale membrane bioreactor (MBR) with a conventional denitrification/nitrification scheme for municipal wastewater treatment has been modelled with an extended version of ASM3 available in the literature, according to which heterotrophic biomass growth occurs on both readily biodegradable COD and storage products. The model has been regularly calibrated by means of respirometric techniques and validated against experimental data of MLSS concentration in the biotank, effluent COD and nitrogen forms. The applied model was able to fairly predict the routinely monitored effluent quality (COD, NH4-N and NO3-N) and sludge production. The model appears to be suitable for improved biological process modelling of MBRs, leading to better process optimization of MBRs for municipal wastewater treatment.

The problem of fresh water scarcity is becoming a global issue, due to rapid urbanisation, population growth, water pollution, climate change and compounded effects. The incorporation of water reuse in upcoming urban water systems will not only satisfy a large part of water demand but also create a situation where wastewater treatment will be essential due to accountability towards the end users of water reuse. There are various technical and non-technical challenges towards the conceptualisation and materialisation of water reuse for a sustainable urban water system. The selection of appropriate technologies for a specific urban settlement is one of the key challenges. A plethora of existing technologies, such as membrane assisted technologies, for wastewater treatment and reuse may pose difficulty in decision making. Decision makers, such as water authorities and industries, often come across a lot of information and facts for a variety of technologies and reuse concepts. A systematic analysis of available technologies and options is necessary in order to increase the chances of success in wastewater reuse projects. Multi-criteria analysis (MCA) is a decision making method for systematic appraisal of wastewater reuse technologies. In this research the MCA has been carried out for the ranking of candidate technologies, after incorporating all the factors in terms of numerical values. Eight membrane assisted technologies have been short-listed due to their suitability under considered water reuse scenarios. Subsequently, most relevant technology selection criteria have been assessed. The MCA based ranking of candidate technologies provides a relative indication of the suitability of various membrane assisted water reuse technologies. It has been concluded that a systematic and rigorous analysis of candidate technologies can help decision makers to compare various available technological options and select the best available option for a sustainable water reuse concept.

Municipal wastewater is often treated at a centralized treatment facility based on Activated Sludge Process (ASP) where the production of (excess) activated sludge (bio-solids) is mostly not desired and further sludge handling often contributes to a large fraction of the total operational cost, depending upon the applicable legislation and/or sludge treatment and disposal practices. Further, the Biological Nutrient Removal (BNR) based on ASPs often pose extra cost due to the need for external carbon source (acetate, methanol etc.) for the optimal performance of denitrification and biological phosphorous removal. In this research, the excess sludge was ozonated and the filtrates were used in activity batch tests for anaerobic P-release, aerobic P-uptake and denitrification. Experimental results have shown that the ozone dose in the range of 0.1-0.2 g O3/g MLSS leads to a good degree of bio-solids destruction (sludge reduction) resulting in highly biodegradable organics. The use of ozonated sludge at those ozone doses as carbon source in the activity tests revealed that the soluble biodegradable organics can be successfully used for improved denitrification and biological P-uptake. Further, the process cost analysis showed the economic feasibility under complete sludge treatment scenario, where about 42% of sludge reduction is achieved and about 30% of the total operational cost reduction may be possible under assumed conditions.