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.
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.
Phosphorus (P) is an essential non-substitutable nutrient for all living organisms, but it is also a dwindling non-renewable resource. Approximately two-thirds of the world’s supply of phosphate rock is located in China, Morocco, and the USA. Phosphate rock is included in the EU list of ‘critical raw materials’ and is ranked 20th in an index of commodity price volatility. P recovery from waste water can help alleviate reliance on imported phosphate and reduce vulnerability to fluctuating prices. This project explored the options for P recovery from wastes produced across Thames Water’s waste water treatment plants (WWTPs), the main foci being sludge dewatering liquors and incineration/pyrolysis residues. The research focussed specifically on the Slough WWTP and the operation of a newly installed Ostara system for recovery of P as struvite from dewatering liquors. The Ostara process is designed to operate with centrate PO4-P concentrations above 100 mg/l; to obtain these concentrations chemical coagulant dosing in the enhanced biological nutrient removal process must be reduced. Centrate monitoring following this change showed that Fe concentrations must measure consistently below 1.5 mg/l for PO4-P concentrations to remain steadily above 100mg/l. Following these changes onsite, operational savings and revenue can be produced onsite. Significant operational and maintenance savings totalling to £113K can be made in the first year of operation of the P recovery system in Slough WWTP. Sale of P rich struvite fertiliser produces annual revenue of £20K. Moving beyond the local benefits of P recovery, national benefits of P recovery were quantified. In a national context, a total of 28±1 kt P/year can be recovered from all WWTP waste streams, reducing P fertiliser imports by 36±1%. P recovery from WWTP influent and incinerated sewage sludge ash would reduce P losses to water bodies by 22±2%. Sewage sludge may be incinerated, producing incinerated sewage sludge ash (ISSA), or alternatively pyrolysed to produce sewage sludge char (PSSC). The possibility of recovering P from these residual solids was also investigated. PSSC samples contained significantly more nitrogen and lower heavy metal concentrations than ISSA samples due to the process conditions. The % P extractions from both ISSA and PSSC plateaus at 0.6M and 0.8M H2SO4 acid concentrations, respectively, due to the formation of gypsum on the particles, so that further increase in acid concentrations does not increase P recovery. The knowledge gained through this research has been used to improve the understanding and efficiency of the P recovery system at Slough WWTP. The information learned about pyrolysis residues will be used by Thames Water to develop a novel P recovery process from PSSC. Combined, these findings can impact the industry by creating incentives and inform policies regarding P recovery.
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.
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.
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.
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).
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.
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).
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.
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.
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.
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.
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.
Seyed M.K. Sadr, Devendra Saroj, Jose Carlos Mierzwa, Scott J. McGrane, George Skouteris, Raziyeh Farmani, Xenofon Kazos, Benedikt Aumeier, Samaneh Kouchaki, Sabeha K. Ouki (2018)A multi expert decision support tool for the evaluation of advanced wastewater treatment trains: A novel approach to improve urban sustainability, In: Environmental Science and Policy90pp. 1-10
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.
George Skouteris, Sabeha Ouki, Dominic Foo, Devendra Saroj, Maria Altini, Paraschos Melidis, Brian Cowley, Geoff Ells, Stephanie Palmer, Sean O'Dell (2018)Water footprint and water pinch analysis techniques for sustainable water management in the brick-manufacturing industry, In: Journal of Cleaner Production172pp. 786-794
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.
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 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.
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 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.
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.
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.
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.
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.
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.
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.
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 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. ) 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.  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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Building works include construction and demolition activities, which are common in cities across the world. Building-related activities contribute a considerable amount of the construction and demolition waste material worldwide. These activities have the potential to produce particulate matter (PM), including PM10 (≤10 μm), PM2.5 (≤2.5 μm) and PM1 (≤1 μm), and airborne ultrafine particles (≤0.1 μm). Recent studies have indicated that the rate of building works undertaken each year is growing exponentially, to meet new urban design guidelines and respond to demand from the adoption of new building technologies, which highlights the importance of measuring the amounts of particle emissions from these sources. The principles of sustainable urban development are well established, but the extent of pollution due to construction and demolition activities is still unknown. Through laboratory and field studies, this thesis aims to comprehensively investigate the release of coarse (referred to as PM2.5–10 fraction), fine (PM2.5) and ultrafine particles from various building works, assess their physicochemical properties, and estimate the associated occupational exposure risk from them to on-site workers and individuals in the close vicinity. Experiments for this thesis were carried out to measure PM and airborne ultrafine particles in the size range of (0.005–10 µm) using a fast response differential mobility spectrometer (DMS50), a tapered element oscillating micro balance (TEOM 1400), a GRIMM particle spectrometer (1.107 E) and OSIRIS (2315). Measurements were made in various locations: a controlled laboratory environment (i.e. concrete mixing, drilling, cutting), indoor field sites (i.e. building refurbishment) and at outdoor field sites (i.e. construction and demolition). Moreover, dust samples were collected simultaneously for physiochemical analyses (e.g. SEM, EDS, XPS and IBA). Several important findings were then extrapolated during the analysis. These findings indicated that ultrafine particles dominated (74-97%) the total particle number concentrations (PNCs) while the coarse particles (PM2.5-10) contributed to the majority of the total particle mass concentrations (PMCs), during the laboratory, indoor and outdoor field experiments. The highest proportion of PNCs and PMCs was found during the concrete cutting, drilling and wall chasing activities. In addition, the highest proportion of PMCs was observed in the excavator cabin during a building demolition at an outdoor field measurement site. Moreover, combining the results of SEM, EDS, XPS and IBA analysis suggested the dominance of elements such as Si, Al and S in the collected samples. The data were also used to assess the horizontal decay of the PMC through a modified box model to determine the emission factors and the occupational exposure to on-site workers and nearby individuals. The results confirmed that building-related works produce significant levels of coarse, fine and ultrafine particles, and that there is a need to limit particle emissions and reduce the occupational exposure of individuals by enforcing effective engineering controls. These findings could also be useful for the building industry to develop mitigation strategies to limit exposure to particulate matter during building works, particularly for ultrafine particles, which are currently non-existent.
Over the last 18 years, different sludge pre-treatment processes have been used to improve the performance of sewage sludge anaerobic digestion efficiency. Some of these pre-treatment technologies, notably the Thermal Hydrolysis Process (THP), has significantly increased the sludge throughput and allowed more efficient utilisation of treatment assets without adversely impacting the biology of the anaerobic digestion process. However, the expected increase in Volatile Solid reduction (VSr) and the consequent increase of biogas production have not been fully realised. Specifically, to address this poor performance when the THP process is used and to overcome its limitations, its application as an Intermediate Thermal Hydrolysis Process (ITHP) was studied. The ITHP process configuration consists of a first stage conventional Mesophilic Anaerobic Digestion (MAD) followed by THP and then a second stage MAD (i.e. MAD+THP+MAD). The main aims of this research were therefore to evaluate the impact of the ITHP configuration on an already digested sludge constituents, namely, carbohydrates, proteins and lipids degradation and the extent of their conversion to biogas. The sludge constituents’ degradation as a result of thermal hydrolysis and Anaerobic Digestion (AD) followed a stepwise process where the initial faster degradation was followed by a second stage slower degradation process. The sludge constituents’ degradation kinetic rate constants showed that the use of ITHP can further enhance the already digested sludge degradation reducing the sludge mass and increasing its conversion to biogas. Furthermore, the ITHP configuration showed a significant impact on sludge Extracellular Polymeric Substance (EPS) content. The results obtained from laboratory scale experiments showed that the ITHP process configuration resulted in an overall average VSr of 62% in comparison with the THP configuration which provided a VSr of 47%. As a result, the overall biogas production from the ITHP process was found to be in excess of 478 m3/tonne dry solids (TDS) fed, compared with 345 m3/tds feed from the THP digestion configuration.
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. In this study, investigation of surface-coated ultrafiltration (UF) poly(vinylidene fluoride) (PVDF) hollow fibre membrane for the removal of organic micropollutants (OMPs) in water was performed. Coating of PVDF membranes with poly(1-phenylethene-1,2-diyl)/polystyrene and pluronics F68 solutions through physical adsorption was carried out in two modes: “dipping” and “spraying”. Surface characterization of coated membranes showed that the coating layer potentially influenced the surface properties suitable for improved solute-membrane interaction. Characterization of the pore size and distribution through Scanning electron microscopy (SEM) images analysis showed that polystyrene coating in sprayed and dipped coating procedure, exhibited more reduction in pore size (19−31%) and closer pore size distribution than the pluronics F68 dip coating (6%). The average roughness (Ra) and maximum peak-to-valley distance (Rmax) measured using the Atomic Force microscopy (AFM) recorded more roughness and irregularity in surface topography in the polystyrene coated membranes compared to the pluronics F68 coating with the dipped polystyrene coating method attaining more roughness (Ra – 0.393 µm). Contact Angle (CA) measurements showed that the dipped Polystyrene coated membrane achieved the highest increase in hydrophobicity (29%) while the dipped pluronics F68 coating achieved a 10% increase. Correlation between the changes in surface roughness and hydrophobicity was evident in the study. Generally, the polystyrene material impacted the membrane surface the most, and the dipped coating procedure recorded the highest surface modification impacts. The performances of the coated membranes in the rejection of the model organic micropollutants, caffeine (hydrophilic) and carbamazepine (hydrophobic) spiked (as single and mixed components) in various water matrices i.e. deionized water, surface water and synthetic wastewater (at concentration range of 300 -1000 μg/L) correlated with the coating materials and methods used. The dip-coated membranes using polystyrene material, achieved better removal of recalcitrant hydrophobic carbamazepine compared to the spray-coated membrane in deionised water, but not in other water matrices. Whereas for both methods of coating, removal of caffeine was relatively insignificant in deionised water but reasonably higher in surface water and synthetic wastewater. From these results, it is inferred that hydrophobic interactions and size exclusion might be the major removal mechanisms involved in rejection by the coated membranes and the colloidal and particulate matter in surface water and fouling in membrane bioreactor system facilitated sorption removal mechanism. The membrane coating enhanced reduction of the pore size, decreasing the membrane permeability and providing more sites for possible solute-membrane interactions. it is demonstrated that physical adsorption of functional polymers is a simple and efficient way to modify the surface properties of polymeric membranes for water filtration application.
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.
ABSTRACT The aim of this research is to evaluate the potential of low energy wastewater treatment processes to meet UK performance requirements, with respect to an increasingly strict regulatory framework This research proposes the implementation of double filtration trickling filters (TF) operating in series without the requirement for intermediate settlement. Performance data is analysed and presented to demonstrate how a 50-80% biological offload of organic carbon (BOD) using a primary plastic media TF can enhance nitrification of existing conventional TFs. This configuration is capable of providing 97.4%, ammoniacal nitrogen (NH4-N) removal with effluent concentrations as low as 1.2mg/L. Process performance data from 120 TF wastewater treatment works (WWTW) are analysed in order to evaluate the relative nitrification performance of TF WWTWs, both with and without aerated tertiary nitrifying processes. Multivariate regression analysis whilst considering flow, temperature and infiltration determines that tertiary nitrification contributes to a significantly higher risk of NH4-N consent being exceeded during colder winter periods. This directly challenges the current strategy of adopting tertiary processes for enhancing nitrification on TF WWTWs. A decentralised facultative aerated lagoon (FAL) system with novel mixing and point source aeration is investigated and evaluated to determine its suitability for offloading existing WWTWs. Computational fluid dynamics (CFD) modelling describes the systems complex hydrodynamics and is validated with an experimental tracer study. Overall, this study showed that low energy mixing is capable of preventing hydraulic short circuiting and thermal stratification, which are notorious for reduced performance in traditional waste stabilisation pond variants.