Dr Bing Guo

Redirecting wastewater organics from conventional energy-consuming aerobic biological removal to an energy-producing process can transform wastewater treatment plants into energy-neutral or energy-positive resource recovery facilities. This study explores the influence of solids retention times (SRTs) and the absence or presence of aeration in the contact phase on the reactor performance and the microbial community in high-rate contact stabilization (HiCS) reactors. Through high-throughput sequencing, we unveil the diversity and complexity of these microbial communities, pinpointing Aquabacterium and Acinetobacter as dominant species particularly susceptible to these parameters. The shifts in microbial communities had clear correlations with reactor performance, impacting carbon capture efficiency, total chemical oxygen demand removal, extracellular polymeric substances, and polyhydroxyalkanoate production. SRT of 1.3 days with aeration in the contact phase resulted in significantly higher carbon capture efficiency. This work elucidates the intricate interplay between HiCS reactor settings, microbial dynamics, and process performance, paving the road for future work optimizing operational conditions in scaled HiCS reactors.

Accumulation and transmission of antibiotic resistance genes (ARGs) in greywater treatment systems present risks for its reuse. In this study, a gravity flow self-supplying oxygen (O2) bio-enhanced granular activated carbon dynamic biofilm reactor (BhGAC-DBfR) was developed to treat greywater. Maximum removal efficiencies were achieved at saturated/unsaturated ratios (RSt/Ust) of 1:1.1 for chemical oxygen demand (97.6 ± 1.5%), linear alkylbenzene sulfonates (LAS) (99.2 ± 0.5%), NH4+-N (99.3 ± 0.7%) and total nitrogen (85.3 ± 3.2%). Microbial communities were significantly different at various RSt/Ust and reactor positions (P 

Microbial community composition has increasingly emerged as a key determinant of antibiotic resistance gene (ARG) content. However, in activated sludge wastewater treatment plants (AS-WWTPs), a comprehensive understanding of the microbial community assembly process and its impact on the persistence of antimicrobial resistance (AMR) remains elusive. An important part of this process is the immigration dynamics (or community coalescence) between the influent and activated sludge. While the influent wastewater contains a plethora of ARGs, the persistence of a given ARG depends initially on the immigration success of the carrying population, and the possible horizontal transfer to indigenously resident populations of the WWTP. The current study utilized controlled manipulative experiments that decoupled the influent wastewater composition from the influent microbial populations to reveal the fundamental mechanisms involved in ARG immigration between sewers and AS-WWTP. A novel multiplexed amplicon sequencing approach was used to track different ARG sequence variants across the immigration interface, and droplet digital PCR was used to quantify the impact of immigration on the abundance of the targeted ARGs. Immigration caused an increase in the abundance of over 70 % of the quantified ARGs. However, monitoring of ARG amplicon sequence variants (ARG-ASVs) at the immigration interface revealed various immigration patterns such as (i) suppression of the indigenous mixed liquor ARG-ASV by the immigrant, or conversely (ii) complete immigration failure of the influent ARG-ASV. These immigration profiles are reported for the first time here and highlight the crucial information that can be gained using our novel multiplex amplicon sequencing techniques. Future studies aiming to reduce AMR in WWTPs should consider the impact of influent immigration in process optimisation and design.

The wastewater treatment sector embraces mixed-culture biotechnologies for sanitation, environmental protection, and resource recovery. Bioprocess design, monitoring and control thrive on microbial processes selected in complex microbial communities. Microbial ecology and systems microbiology help access microbiomes and characterize microorganisms, metabolisms and interactions at increased resolution and throughput. Big datasets are generated from the sequencing of informational molecules extracted from biomasses sampled across process schemes. However, they mostly remain on science benches and computing clusters, without reaching the industry in a clear engineering objective function. A bilateral bridge should actionize this information. As systems microbiologists, we miss that engineering designs and operations rely on stoichiometry and kinetics. The added-value provided by microbial ecology and systems microbiology to improve capital (CAPEX) and operating expenditures (OPEX) needs to be addressed. As engineers, we miss that microbiology can be more powerful than physical-chemical measurements for quantitative process design (e.g., nutrient removal systems) with detailed scientific description of phenomena inside microbiomes. In this perspective article, we allied academia and industry to address the state of shared knowledge, successes and failures, and to establish joint investigation platforms. Our roadmap involves three milestones to (i) elaborate an essential list of microbiological information needed to implement methods at process line; (ii) characterize microbiomes from microorganisms to metabolisms, and shape conceptual ecosystem models as primer for process ecology understanding; (iii) bridge engineering and mathematical models with an analytical toolbox for fast- vs. high-throughput analyses to discover new microbial processes and engineer assemblies. We praise for a harmonized “language of love” (incorporating common vocabulary, units, protocols) across the water and environmental biotechnology sector to team up mindsets for a sewer- and plant-wide integration of systems microbiology and engineering.

Anaerobic digestion (AD) has been widely applied for the degradation of organic wastewater due to its advantages of high-load operation and energy recovery. However, some challenges, such as low treatment capacity and instability caused by the accumulation of volatile fatty acids, limit its further application. Here, S. wolfei and G. sulfurreducens were initially co-cultured in the anaerobic anode of bio-electrochemical system for degrading butyric acid. Butyrate degradation characteristics in different conditions were quantitatively described. Moreover, G. sulfurreducens simultaneously strengthened the consumption of H and acetic acid via direct interspecies electron transfer, thereby strengthening the degradation of butyric acid via a co-metabolic process. During butyrate degradation, the co-culture of S. wolfei and G. sulfurreducens showed more advantages than that of S. wolfei and methanogens. This present study provides a new perspective of butyrate metabolism, which was independent of methanogens in an AD process.

Linear alkylbenzene sulfonates (LAS) in greywater (GW) will simulate antibiotic resistance genes (ARGs) production in the biofilm-based system. Our study emphasizes the dissolved oxygen (DO)-dependent ARGs accumulation and microbial niches succession in an oxygen-based membrane biofilm reactor (O2-MBfR) treating GW, as well as revealing the key roles of EPS. Changing DO concentrations led to significant differences in ARGs production, EPS secretion and microbial communities, as well as the organics and nitrogen removal efficiency. Increasing DO concentration from 0.2 to 0.4 mg/L led to improved organics (> 90%) and nitrogen removal, as well as less EPS (especially for proteins and carbohydrates) and ARGs accumulation (e.g., intl-1, korB and sul-2) in the biofilm; the high-DO-concentration accumulated microbial niches, including Flavobacteriaceae and Cyanobacteria that revealed by LEfSe analysis, contributed to both nitrogen reduction and organics biodegradation. While, the inefficient electron acceptor at low DO conditions (0.2 mg/L) reduced the organics and nitrogen removal efficiency, as well as the improved accumulation of EPS in biofilm; high EPS enabled the capture of residual LAS from the liquid phase, which stimulated the production of ARGs by the distinct microbial community compositions. These findings suggested the DO-based ARGs reduction regulation strategy in the O2-MBfR treating GW.

As a widely used ampholytic surfactant, cocoamidopropyl betaine (CAPB) has been improved to enhance waste activated sludge (WAS) reduction in the short-time aerobic digestion (STAD) system, but how system pH value affects the synergetic combined process has not been discussed. This research evaluated how alkalinity affects soluble microbial products (SMP) dynamics and WAS reduction in the synergetic system. After adding CAPB, the biodegradation rate constant of VSS (kVSS), TCOD (kTCOD) and CAPB (kCAPB) were much higher than that of without adding CAPB; pH value at 7.0–8.0 showed the maximum specific oxygen uptake rate (SOUR) of WAS, leading to the highest WAS reduction efficiency. Further study indicated that CAPB can significantly improve the release of extracellular polymeric substances (EPS), leading to the increased SMP concentrations and low molecular weight fractions (MWF) proportions in SMP; more SMP with low MWF fraction led to the increased SOUR, thus further accelerate the WAS reduction; increasing pH could improve the foaminess and solubility of CAPB, thus further improve the organics release and SMP accumulation, which could be quickly removed in the system. This findings lay the foundation of the practical application of the synergetic combination system in WAS reduction.

Several technologies have been employed to treat greywater (GW) for domestic use. Aerobic biological treatment has achieved high efficiency, the main cost being the necessary source of oxygen (O2). This study explores the effects of lumen air pressure (LAP) on reactor performance and microbial community succession in an O2-based membrane biofilm reactor (O2-MBfR) treating GW. At high LAP (≥0.8 psi), the dissolved oxygen (DO) concentration inside the reactor was higher than 0.38 ± 0.02 mg/L, leading to removal efficiencies of 90%, 98%, and 80%, of total chemical oxygen demand, total linear alkylbenzene sulfonate (LAS), and total nitrogen, respectively. Lower LAP (0.38 mg/L), but led to the reduction of the relative abundance of heterotrophs (Acidovorax, Thermomonas, Brevundimonas and Enterobacter) that are more sensitive towards high DO conditions.

Constructed wetlands have been widely used for organic wastewater treatment owing to low operating costs and simple maintenance. However, there are some disadvantages such as unstable efficiency in winter. In this study, a microalgal electroactive biofilm-constructed wetland was coupled with anaerobic digestion for full-scale treatment of swine wastewater. In a 12-month outdoor trial, the overall removal efficiencies of chemical oxygen demand, ammonium, nitrate, total nitrogen, total phosphorus, and nitrite reached 98.26%/95.14%, 97.96%/92.07%, 85.45%/66.04%, 95.07%/91.48%, 91.44%/91.52%, and 85.45%/84.67% in summer/winter, respectively. Hydrolytic bacteria were dominant in the anaerobic digestion part, and Cyanobium, Shewanella, and Azoarcus were enriched in the microalgal electroactive biofilm. The operating cost of the entire system was approximately 0.118 $/m3 of wastewater. These results confirm that the microalgal electroactive biofilm significantly enhances the efficiency and stability of constructed wetlands. In conclusion, the anaerobic digestion-microalgal electroactive biofilm-constructed wetland is technically and economically feasible for the treatment of swine wastewater. [Display omitted] •Constructed wetlands are widely used for aquaculture wastewater treatment.•Microalgal electroactive biofilm-constructed wetland coupled with anaerobic digestion was tested.•COD, NH4+-N, NO3−-N, TN, TP, & NO2−-N treatment were enhanced, even in winter.•Cyanobium, Shewanella &Azoarcus dominated microalgal electroactive biofilm.•The operating cost of the entire system was approximately 0.118 $/m3 of wastewater.

The treatment of micro-polluted water via a constructed wetland (CW), such as fishpond aquaculture wastewater, encounters problems such as low effectiveness and poor stability. In this study, an emerging algae-bacteria microbial fuel cell (AB-MFC) was coupled with CW to strengthen the treatment of fishpond aquaculture wastewater. Compared with those in the control group (without AB-MFC), the average removal efficiencies of chemical oxygen demand, total phosphorus, total nitrogen, NH4+-N, NO3—N, and NO2—N in AB-MFC-CW were enhanced by 23.84%, 21.44%, 15.07%, 16.91%, 15.02%, and 9.83%, respectively. High-throughput sequencing revealed that Acinetobacter, Cyanobium, Pseudomonas, and Ottowia were relatively abundant on the electroactive AB biofilm. Geobacter, Aminicenantales and Clostridium grew well in the MFC Anode. The economic evaluation indicated that energy consumption per ton of sewage treatment was 0.0045 kWh/m3. These results confirm that the AB-MFC-CW is feasible for enhancing the treatment of aquaculture wastewater at both technical and economic levels through pilot-scale verification. [Display omitted] •Electroactive bacteria-algae biofilm was combined with constructed wetland system.•Electroactive microbes improved treatment efficacy of aquaculture wastewater.•Cathode improved C, N, and P removal by enriching microalgae and exoelectrogens.•Pilot-scale system required low daily energy consumption.•Designed system can be used to treat aquaculture wastewater.

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 feasibility of municipal sewage treatment in laboratory-scale up-flow anaerobic sludge blankets was investigated in this work. Unlike previous studies, granular activated carbon (conductive) or sponge (non-conductive) was introduced to hollow plastic balls as carriers and suspended in the middle and upper layers of the reactors. The two bioreactors were operated at four different hydraulic retention times (stepwise reduced from 24 h to 8 h) for 100 days at ∼18 °C. The conductive-amended treatment was more effective than the non-conductive treatment in enhancing reactor performance. Interestingly, in the reactor containing conductive carriers, microorganisms enriched in the conductive biofilm were also dominant in the suspended sludge. In the reactor containing sponge carriers, the dominant microorganisms differed between the non-conductive biofilm and the suspended sludge. This study underlines that the enrichment of functional microbial communities and the positive impacts of biofilm on suspended sludge are the keys to improving biomethane recovery.

In this study, two Cr(VI)-reducing functional bacterial strains (TJ-1 and TJ-5) were successfully isolated and screened from the chromium-contaminated soil from a real site. The 16S rRNA gene sequences were analysed, which showed high similarity (>99%) with Stenotrophomonas maltophilia (TJ-1) and Brucella intermedius (TJ-5) species. The optimum growth for the two bacteria to reduce Cr(VI) were achieved at pH 7.0 and initial inoculation amount of 5%. The two strains were applied to real contaminated soil samples and showed better Cr removal when external carbon sources were added. Using sawdust as a solid-phase carbon source supplement, both TJ-1 and TJ-5 showed higher remediation efficiency (99.77% and 93.86%) than using glucose as the carbon source (68.56% and 70.87%). Results of the stability of soil Cr(VI) bioremediation revealed that the water-soluble Cr(VI) content of bioremediated sample remained unchanged, indicating that Cr(VI) is not easily released after death of the strains. Solid-phase carbon source supplements may help the cells to attach and grow into biofilms, creating a better growth condition which improved the remediation efficiency. Column experiments showed that the total remediation efficiencies by the two strains were 34.23% and 20.63%, respectively, within a short time period (76 h). Therefore, the two strains showed great bioremediation potentials for chromium-contaminated sites and can be used in future application of in-situ bioremediation.

Driven by rainfall and agricultural irrigation, chromium slag causes serious pollution to the subsurface environment and damages the indigenous soil bacterial community. The study of the ecological responses of bacterial community to chromium pollution can provide support for bioremediation of chromium pollution. In this study, soil samples at different depths (0, 2, 5, 7 m) in a long-term chromium contaminated site were selected to analyze the vertical changes and responses of bacterial community structure using high-throughput 16S rRNA gene sequencing. Total Cr and soluble Cr(VI) concentrations were highest in topsoil and decreased with depth. Compared with the topsoil of uncontaminated land, the alpha-diversity in the contaminated topsoil was significantly reduced, and the bacterial community composition was altered. With increasing soil depth, the alpha-diversity decreased, and the species distribution became more uneven. Topsoil and subsurface soil showed different bacterial community structures, associated with the Cr concentration and physicochemical properties. Proteobacteria in all samples were dominant, and their relative abundances increased with depth. Bacterial community alpha-diversity and dominant taxa can be used as indicators of response to chromium pollution. The predicted metagenomic functional annotation (using Tax4Fun) showed that the relative abundance of chromate transporters (chrA, K07240) in the topsoil is 20–30 times of that in deeper soil, indicating potential bioremediation capability by topsoil bacterial community. The bioremediation feasibility of reducing Cr(VI) using indigenous bacterial community showed that Cr-polluted topsoil bacterial community has ability to reduce Cr(VI). [Display omitted] •Alpha diversity of Cr-contaminated site bacterial community decreased with depth.•Proteobacteria were dominant and increased with depth.•Chromate transporter chrA in the surface soil is 20–30 times of that in deeper soil.•Deeper soil showed anaerobic Cr(VI) removal potential.

Low-strength wastewater was treated using two laboratory-scale up-flow anaerobic sludge blankets (UASB) for 130 days under sulfate-reducing conditions. Granular activated carbon (GAC) was added to one of the reactors. The GAC addition increased the total chemical oxygen demand removal by 21% - 28% and total methane production by 32% - 78%. The sludge from the GAC-amended UASB showed higher specific methanogenic activities (SMA) and higher activities in the presence of H2S, indicating that the GAC addition enhanced the resistance of methanogens to H2S toxicity. Further, the microbial communities showed that the GAC addition shifted microbial communities. A robust syntrophic partnership between bacteria (i.e., Bacteroidetes_vadinHA17 and Trichococcus) and methanogens was established in the GAC-amended UASB. Sulfate-reducing bacteria (SRB) were enriched in the GAC biofilm, indicating the coexistence of competition and cooperation between SRB and methanogens. These findings provide significant insights regarding microbial community dynamics, especially SRB and methanogens, in a GAC-amended anaerobic digestion process under sulfate-reducing conditions.

Carbon/nitrogen ratio is an important parameter during the biological wastewater treatment. Our study emphasizes revealing the mechanisms of chemical oxygen demand/total nitrogen (COD/TN) ratio dependent improved greywater (GW) treatment in an oxygen based membrane biofilm reactor (O2-MBfR). Results showed that reducing COD/TN ratio from 40 to 20 g COD/g N by supplementing NH4Cl to GW improved the relative abundance of genera related to LAS-biodegradation (from 8.39% to 35.7%), nitrification (from 0.20% to 0.62%) and denitrification (from 3.01% to 7.59%). Reducing COD/TN ratio also led to an increase in the ammonia monooxygenase (AMO) activity (from 7.56 to 10.2 mg N/g VSS-h), as well as improved ammoxidation and linear alkylbenzene sulfonate (LAS) mineralization although the dissolved oxygen (DO) concentration and pH decreased. Much higher NH4+ − N at lower COD/TN ratio (10 units) led to lower DO (0.13 ± 0.01 mg/L) and pH (6.72 ± 0.02), but the continuously increased AMO activity (up to 12.9 mg N/g VSS-h) enabled the cometabolism of ammoxidation and LAS mineralization, leading to the efficient removal of organics and nitrogen under the low DO condition.

A heterotrophic-specialist model was proposed previously to divide wastewater treatment plant (WWTP) heterotrophs into sub-guilds of consumers of readily or slowly degradable substrates (RDS or SDS, respectively). The substrate degradation rate model coupled to metabolic considerations predicted that RNA and polyhydroxyalkanoate (PHA) levels would be positively correlated in the activated sludge communities with high RNA and PHA occurring in RDS-consumers, and low RNA with no PHA accumulation occurring in SDS-consumers because their external substrates are always present. This prediction was verified in previous studies and in the current one. Thus, RNA and PHA levels were used as biomarkers of the RDS- and SDS-consumer sub-guilds for cell sorting using flow cytometry of samples from three WWTPs. Subsequently, 16S rRNA gene amplicon sequencing revealed that the sorted groups were highly similar over time and among WWTPs, and demonstrated a clear segregation by RNA levels. Predicted ecophysiological traits based on 16S rRNA phylogeny suggested that the high-RNA population showed RDS-consumer traits such as higher rrn copy numbers per genome. Using a mass-flow immigration model, it appeared that the high-RNA populations exhibited high immigration rates more frequently than low-RNA populations, but the differences in frequencies were less with increasing solids residence times.

Biofilm bioreactors are attracting growing interest in the wastewater industry, as they allow higher cell densities and thus higher reaction rates compared to conventional bioreactors. However, some commonly used nitrifying bacteria, such as Nitrosomonas europaea, are slow-growing and need a prolonged period of time to develop a mature biofilm. Here, a biocoating or "living paint" is introduced, which is a synthetic biofilm made from a colloidal polymer (synthetic latex) binder encapsulating viable nitrifying bacteria at high density. Conventionally, the film formation of biocoatings is achieved by drying a bacteria/latex mixture. However, this fabrication is detrimental to the viability of the encapsulated bacteria because of the osmotic stress induced by desiccation. A nondesiccating film formation process is presented for biocoatings, which exploits two colloid science phenomena: coagulation and wet sintering. Desiccation-sensitive, nitrifying bacteria are employed in the biocoatings to convert NH4+ to NO2- and then NO3-. These biocoatings have a conversion rate (NO2- and NO3- production) of 3 mg N g(-1) d(-1) that is five times higher than in conventionally desiccated biocoatings. The reactivity continues over a period of 1 month. The processing method for these living paints is transformative for wastewater treatment and other applications using delicate, desiccation-sensitive microorganisms.

The aerobic granular sludge wastewater treatment technology has numerous advantages as compared to the conventional flocculent sludge technologies. However, the filamentous fungi overgrowth (FFO) is a major operational problem that is hindering its widespread application. This study evaluated the behaviour and mechanisms of the FFO, and its impact on granulation, treatment performance and microbial community structure. The overgrown filamentous organisms were developed in an aerobic granular sludge reactor operated for 274 days. The filamentous organisms were identified to be yeast-like fungi belonging to the moulds Geotrichum of the phylum Ascomycota. The removal of carbon and nitrogen were slightly affected, while phosphorus removal was largely impacted. The FFO development was found to disrupt the structural integrity of granules, cause their disintegration and washout, and lead to a microbial community shift towards a structure lacking bacteria genus that are essential for efficient granulation. Limitations of the currently used routine measurements were discussed.

This review covers research articles published in 2017 on topics relating to physico-chemical processes for water and wastewater treatment. The paper divides into nine sections, i. e., membrane technology, ion exchange, capacitive deionization, granular filtration, coagulation/flocculation, sedimentation, flotation, oxidation and adsorption. The membrane technology part includes six parts, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD).

A review of the literatures published in 2017 on topics relating to analytical methods for pesticides and herbicides is presented in this paper. Based on different techniques, this review is divided into seven parts, i. e., extraction methods, chromatographic or mass spectrometric techniques, electrochemical techniques, spectrophotometric techniques, chemiluminescence and fluorescence methods, biochemical assays and immunoassays, and miscellaneous techniques.

[Display omitted] •Potassium ferrate promoted both methane production potential and rate of sludge.•Potassium ferrate accelerated sludge disintegration.•The biodegradability of organics liberated from sludge flocs was improved.•Potassium ferrate enhanced the digestion of humus and lignocellulose. This study investigated the issue of potassium ferrate (PF) affecting anaerobic methane generation from sludge by a set of experimental and model analyses. Experimental results indicated that the methane production was significantly promoted from 164.7 to 204.1 mL/g VSS (volatile suspended solids) with PF dosage enhanced from 0 to 0.05 g/g TSS (total suspended solids). Further enhancement of PF dosage reduced methane production, which even decreased to 135.4 mL/g VSS when PF dosage increased to 0.1 g/g TSS. Model-based analysis showed that except for methane production potential, the methane production rate was also promoted by PF treatment, which was sufficiently enhanced from 8.80 to 11.88 mL/g VSS/d when PF dosage was 0.05 g/g TSS. Mechanism studies indicated that PF not only promoted sludge disintegration, but also enhanced the proportion of biodegradable organics in sludge liquor, and the digestion potential of the non-biodegradable humus and lignocellulose were promoted.

The addition of granular activated carbon (GAC) to up-flow anaerobic sludge blanket (UASB) reactors treating synthetic wastewater enhanced methane production by stimulating direct interspecies electron transfer (DIET). A modified UASB reactor with GAC packed in plastic carriers that allowed the GAC to float in the upper reactor zone achieved enhanced performance compared to a UASB reactor with GAC settled at the bottom of the reactor. Microbial communities in the biofilms developed on settled or floated GAC were compared. Methanosarcina (56.3-73.3%) dominated the floated-GAC biofilm whereas Methanobacterium (84.9-85.1%) was greatly enriched in the settled-GAC biofilm. Methanospirillum and Methanocorpusculum were enriched in the floated-GAC biofilm (8.8-19.8% and 5.1-9.5%, respectively), but only existed in low abundances in the settled-GAC biofilm (3.4-3.6% and 0-0.4%, respectively). The floated GAC developed bacterial communities with higher diversity and more syntrophic bacteria enrichments on its surface, including Geobacter, Smithella, and Syntrophomonas, than the settled-GAC biofilm. Common hydrogen-donating syntrophs and hydrogenotrophic archaea, Methanospirillum and Methanoregula, were identified as potential electro-active microorganisms related to DIET.

Operational factors and microbial interactions affect the ecology in anaerobic digestion systems. From 12 lab-scale reactors operated under distinct engineering conditions, bacterial communities were found driven by temperature, while archaeal communities by both temperature and substrate properties. Combining the bacterial and archaeal community clustering patterns led to five sample groups (ambient, mesophilic low-solid-substrate, mesophilic, mesophilic co-digestion and thermophilic) for co-occurrence network analysis. Network topological properties were associated with substrate characteristics and hydrolysis-methanogenesis balance. The hydrolysis efficiency correlated (p 

Developments in energy recovery from decentralized wastewater streams provide a critical contribution to reducing greenhouse gases (GHGs) and promoting resource recovery. Source-diverted blackwater collected from vacuum toilets contains high solids organic content and is ideal for wastewater resource recovery. In the present study, an upflow anaerobic sludge blanket (UASB) reactor was operated under the mesophilic temperature condition (35 °C) to investigate methanogenic pathways and microbial development under high-loading conditions. We achieved the highest maximum organic loading rate (OLR) reported to date, at 4.1 kg chemical oxygen demand (COD)/m3/day (hydraulic retention time [HRT] 2.6 days), with a CODt removal efficiency of 84% (±5%), and methane production of 0.68 (±0.08) m3 CH4/ m3 reactor/day. This high efficiency resulted from domination of the H2/CO2 methanogenic pathway. Hydrogenotrophic methanogens with the genus Methanogenium were specifically enriched with the continuous treatment of blackwater.

The current study was conducted to investigate the effects of mixing ratios on anaerobic co-digestion of blackwater and kitchen organic waste. The biological methane potential (BMP) of co-digested blackwater and kitchen waste were 0.85 ± 0.07 and 0.83 ± 0.06 at volatile solids (VS) ratios of 1:2 and 1:3 whereas the BMP of blackwater alone was 0.34 ± 0.01. The hydrolysis efficiency improved from 57 ± 8% in anaerobic digestion of blackwater alone to 87 ± 8% in the blackwater/kitchen waste co-digestion condition. The methane production yield increased from 449 ± 32 Nml CH4/gVS for blackwater only to 680 ± 58 and 630 ± 52 Nml CH4/gVS at blackwater/kitchen waste VS ratios of 1:2 to 1:3. Hydrogenotrophic methanogens dominated the methanogen community under a blackwater/kitchen waste VS ratio of 1:2 condition. The results suggest that blackwater energy recovery can be improved by co-digesting blackwater with kitchen waste. [Display omitted]

Two laboratory-scale up-flow anaerobic sludge blankets (UASB) reactors treating municipal sewage were operated to test the effects of granular activated carbon (GAC) addition under sulfate-reducing and psychrophilic conditions. As compared to the non-GAC reactor, the GAC-amended reactor simultaneously enhanced chemical oxygen demand (COD) removal (from 61% to 69%) and methane production (from 11% to 20%) (all with P 

Two laboratory-scale up-flow anaerobic sludge blankets (UASB) reactors, one with and one without granular activated carbon (GAC), were operated for municipal sewage treatment at low temperatures (16.5 ± 2.0 °C). During the 120-day operation, the GAC-amended reactor significantly enhanced COD removal (from 62% to 75%, P < 0.05) and methane production (from 87 to 218 mg CH4-COD/reactor/d) than the non-GAC reactor. Bacterial communities were significantly different between the two reactors (P < 0.05). Geobacter, a key indicator for direct interspecies electron transfer (DIET), had the highest differential score (LEfSe analysis), showing significantly higher abundances in the GAC-amended reactor (3.7–8.8%) than the non-GAC reactor (0.9–4.0%). GAC also enriched syntrophic bacteria, Syntrophomonas, Syntrophus and sulfate reducing bacteria. Methanobacterium dominated the archaeal community in the GAC-amended reactor sludge (35.7%) and GAC-biofilm (75.3%), and was less abundant in the non-GAC reactor (9.9%). It indicates that GAC enriched microbial syntrophic partners with potential electro-activities in the anaerobic digestion process.

Granular activated carbon (GAC) has been shown to mediate direct interspecies electron transfer (DIET) in anaerobic digestion. Adding GAC to up-flow anaerobic sludge bed reactor increased the total biomass slightly from 20.0 to 26.6 gVSS/reactor, and maximum organic removal capacity remarkably from 285 to 1660 mgCOD/L/d. Since GAC occupied 7% of reactor volume (denser than suspended sludge, settled to the reactor bottom), we used a spatial sampling strategy (sludge bed top/mid/bottom layers, and tightly attached GAC-biofilm) and DNA- and RNA-based community analyses. RNA-based analysis demonstrated significant community differences between the non-GAC and GAC-amended reactors (p  0.05). RNA-based analysis revealed active enrichments in GAC-biofilm, including bacteria Geobacter, Syntrophus, Desulfovibrio and Blvii28, and archaea Methanosaeta and Methanospirillum. These are potential electro-active syntrophic microorganisms related with DIET, which expand the previously defined list of DIET microorganisms.

Anaerobic digestion (AD) of source-diverted blackwater (toilet flush) at ambient room temperature presents challenges for fast hydrolysis of particulate matters. This study investigated the effect of different micro-aeration dosages for blackwater AD. Sequencing batch reactors were operated at ambient room temperature (22 ± 1°C) with micro-aeration (0, 5, 10, 50, and 150 mg O2 g−1 CODfeed per cycle) and gradually reduced hydraulic retention times from 5 d to 2 d. The methanogenesis efficiencies were greater at low oxygen dosages (i.e., 0, 5, 10) while the volatile fatty acids (VFAs) accumulated more at high oxygen dosages (i.e., 50, 150). Microbial communities were significantly different under different oxygen dosages (p

Microbial heterotrophic guilds in activated sludge wastewater treatment systems have complex population structures and functions. A previously proposed heterotrophic-specialist model states that heterotrophs consist of sub-guilds specialized in consuming specific classes of compounds, either readily degradable substrate (RDS) or slowly degradable substrate (SDS) according to current mathematical modeling practices for wastewater treatment processes. It follows from metabolic considerations that the levels of RNA and polyhydroxyalkanoate (PHA) are correlated for strains of the same species growing in different environments; a conjecture previously tested. The proposed classification of heterotrophs into RDS or SDS consumers predicts that the same correlation would also be found across heterotrophic species in conventional activated sludge systems; this prediction was tested in the current study. The positive correlation between the RNA and PHA levels was observed in 9 conventional activated sludge plants in two independent sampling times and it was also found stable over a 6-month regular sampling period at one of these plants. Together, these results imply that the levels of RNA and PHA can be used to define heterotrophic-specialist sub-guilds. In order to gain insight in the species composition of the defined sub-guilds, flow cytometry cell sorting was used to further analyze one of the activated sludge samples. Four sorted sub-samples were obtained (high-RNA/high-PHA, low-RNA/high-PHA, high-RNA/low-PHA, and low-RNA/low-PHA), and the phylogenetic composition of each was determined using 16S rRNA gene amplicon pyrosequencing. Heterotrophic genera were identified across 12 phyla, and their representation in each sorted sub-sample showed that the high-RNA/high-PHA and low-RNA/low-PHA groups were most dissimilar. The enriched genera in these sorted sub-samples are suggested to represent the composition of heterotrophic-specialized sub-guilds defined by the kinetics of substrate consumption.

Residual biosolids can be land applied if they meet microbiological requirements at the time of application. Electro-dewatering technology is shown to reduce biosolids bacterial counts to detection limits with little potential for bacterial regrowth during incubations. Here, we investigated the impacts on Escherichia coli regrowth and microbial communities of biosolids pH, removed nutrients via the filtrate, and inhibitory compounds produced in electro-dewatered biosolids. Findings suggest pH as the primary mechanism impacting E. coli regrowth in electro-dewatered biosolids. Propidium monoazide treatments were effective at removing DNA from dead cells, based on the removal of obligate anaerobes observed after anaerobic incubation. Analyses of high throughput sequenced data showed lower alpha-diversities associated with electro-dewatering treatment and incubation time. Moreover, biosolids pH and incubation period were the main factors contributing to the variations in microbial community compositions after incubation. Results highlight the role of electro-dewatered biosolids' low pH on inhibiting the regrowth of culturable bacteria as well as reducing the microbial community variance. [Display omitted] •pH was the main parameter impacting E. coli regrowth in electro-dewatered biosolids.•Alpha diversity was impacted by biosolids treatment, pH, and incubation period.•Microbial community compositions after PMA treatment comprise the regrowing species.•pH and incubation time were main factors shaping overall microbial communities.

This work evaluated the fates of linear alkylbenzene sulfonate (LAS), chemical oxygen demand (COD), ammonia nitrogen (NH4+−N), and total nitrogen (TN) when treating greywater (GW) in an oxygen-based membrane biofilm reactor (O2-MBfR). An influent ratio of chemical oxygen demand to total nitrogen (COD/TN) of 20 g COD/g N gave the best removals of LAS, COD, NH4+−N and TN, and it also had the greatest EPS accumulation in the biofilm. Higher EPS and improved performance were linked to increases in the relative abundances of bacteria able to biodegrade LAS (Zoogloea, Pseudomonas, Parvibaculum, Magnetospirillum and Mycobacterium) and to nitrify (Nitrosomonas and Nitrospira), as well as to ammonia oxidation related enzyme (ammonia monooxygenase). The EPS was dominated by protein, which played a key role in adsorbing LAS, achieving short-time protection from LAS toxicity and allowed LAS biodegradation. Continuous high-efficiency removal of LAS alleviated LAS toxicity to microbial physiological functions, including nitrification, nitrate respiration, the tricarboxylic acid (TCA) cycle, and adenosine triphosphate (ATP) production, achieving the stable high-efficient simultaneous removal of organics and nitrogen in the O2-MBfR.

Biogas (methane) as a source of renewable energy, was produced in the anaerobic co-digestion of blackwater (BW, municipal toilet wastewater) and organic kitchen waste (KW). The impact on methane production of various BW to KW mixing ratios, with and without the addition of granular activated carbon (GAC), were studied under thermophilic (55 °C) temperatures. GAC is reported to enhance methane production in such digestions through direct interspecies electron transfer. The results showed that the co-digestion of BW and KW under the 1:2 VS ratio significantly improved the biomethane potential (BMP). In the absence of GAC, an optimal BW:KW ratio was found to be 1:2, achieving a BMP of 0.76 g CH4-COD/g feed-COD. With GAC addition, the BMP increased to 0.81 g CH4-COD/g feed-COD, the lag phase in the digestion was significantly reduced, and the methane production rate increased. Microbial communities in the BW-KW anaerobic digestion were analyzed with and without the addition of GAC. Methanothermobacter and Methanosarcina were predominant archaea in BW-KW digests, with and without GAC amendment, while a third methanogen, Methanomassiliicoccus, was enriched with the addition of GAC to the digest. Further, through SEM image, the enrichment of pili-like stucture was observed in GAC surface.

The present work studied the application of a thermophilic upflow anaerobic sludge blanket (UASB) reactor treating source-diverted blackwater for simultaneous energy (in the form of methane production) and nutrient (phosphorus) recovery. Our results showed that a methane production rate of 2.4 ± 0.1 NL CH4/(L d) can be achieved with an organic loading rate of 12.9 kg COD/(m3d) and a methane yield of 55.9 ± 6.2%; far exceeding previous yields reported for blackwater treatment. Most significant was the removal of phosphorus (77.7 ±8.5% PO4-P) in the form of Ca3(PO4)2 precipitates in the anaerobic granular sludge. Key factors thought to promote the observed performance included rapid protein and urea hydrolysis along with hydrogenotrophic methanogenesis (by Methanosarcina spp.), and localized pH increase enhancing granulation and phosphorous sequestration. The granule sludge rich-in phosphorus contained negligible heavy metal contamination, and could provide an alternative source for phosphorus refinery or direct agricultural use.

Anaerobic digestion (AD) at low temperature (20 °C) for low-strength municipal sewage (COD of 500 mg/L) treatment was evaluated in two laboratory-scale up-flow anaerobic sludge blankets (UASBs), one with and one without granular activated carbon (GAC). During the 120-day operation, the addition of GAC significantly improved average COD removal (from 56% to 82%) and methane production (from 132 to 264 mL CH4/g feed-COD), allowing for a reduced hydraulic retention time (from 1 d to 0.25 d) and an increased organic loading rate (from 500 to 2000 mg COD/L/d). There was a significant (p < 0.01) improvement in specific methanogenic activity (SMA) from 20 mL CH4/g VSS/d in non-GAC UASB sludge to 58 mL CH4/g VSS/d in GAC-amended UASB sludge, which may explain the enhanced performance with GAC. Direct interspecies electron transfer (DIET) was proposed as the mechanism and sludge properties were compared. Surprisingly, the archaeal and bacterial communities were similar between the two reactors. Further studies revealed significant sludge physiological changes in the GAC-amended reactor, including enhanced electric conductivity (from 1.52 to 8.37 μS/cm), increased functional gene pilA expression as confirmed through RT-qPCR (36-fold increase), as well as reduced inhibition by high H2 partial pressure (0.17 atm), all implying the development of DIET through the cellular electro-conductive structure e-pili.

Co-digestion of blackwater (BW) and organic kitchen waste (KW) is a promising and effective resource-recovery based approach for municipal waste and wastewater treatment. In this study, anaerobic co-digestion treatments of BW and KW using anaerobic sequencing batch reactors under mesophilic and thermophilic conditions were compared. Our results showed that although higher sludge specific methanogenesis activities were observed in the thermophilic reactor, mesophilic treatment achieved significantly higher treatment capacity and methane production. It was concluded that thermophilic conditions introduced H inhibition and reduced activities of syntrophic acetogenic bacteria and syntrophic acetate oxidizing bacteria in the reactor. Further investigation on microbial communities showed significantly different microbial communities between reactors, where Thermotogaceae and Methanothermobacter were the most prevalent bacteria and archaea in the thermophilic reactor, and Cloacamonaceae and Methanosarcina were the most prevalent ones in the mesophilic reactor.

Ammonia-rich lagoon supernatant was treated using anammox process in an integrated fixed-film activated sludge (IFAS) laboratory reactor. Effective anammox activities were demonstrated over 259 days of operation. The ammonium removal efficiency reached 94% in Phase I with influent concentrations of NH4+, NO2− and chemical oxygen demand (COD) at 250 mg-N/L, 325 mg-N/L, and 145 mg-COD/L, and reached 88% in Phase II at 420 mg-N/L, 525 mg-N/L, and 305 mg-COD/L. When supplemented with nitritation effluent for nitrite sources in Phase III, the influent COD concentration increased to 583 mg-COD/L without loss of ammonia removal efficiency (87%). The specific anammox activity was higher in biofilm than in the suspended flocs (P 

A laboratory-scale anammox integrated fixed-biofilm activated sludge sequencing batch reactor (IFAS-SBR) was operated for 339 days as the post treatment of a nitritation reactor treating ammonium rich digestate lagoon supernatant. By shortening the hydraulic retention time (HRT) from 2.5 d to 1.7 d, the inorganic nitrogen (N) loading rate increased from 0.38 ± 0.00 kg m3 d−1 to 0.61 ± 0.02 kg m−3 d−1; this led to a slight enhancement in the anammox activity. While the activity of anammox bacteria was inhibited by the interim accumulation of NO2−-N (141.2 – 219.2 mg L−1) in the reactor when the HRT was further reduced to 1.2 d, changing the reactor feeding strategy mitigated the nitrite inhibition and restored anammox activity. The presence of organic carbon in lagoon supernatant facilitated the growth of heterotrophic denitrifiers in the reactor; however, this had little impact on N reduction (93.2 ± 3.8% by anammox). Additional batch experiments and sequencing batch reactor cycle tests compared anammox bacterial specific activities under different operating strategies. The dynamics of anammox bacteria and heterotrophic denitrifiers along with the operating strategy changes were documented by qPCR analyses. Our study underlines the importance of optimizing operating strategies within anammox reactor operation for treating ammonia rich digestate lagoon supernatant.

Propionate is one of the most important intermediates in anaerobic digestion, and its degradation requires a syntrophic partnership between propionate-oxidizing bacteria and hydrogenotrophic methanogens. Anaerobic digestion efficiency can be improved by direct interspecies electron transfer (DIET) through conductive materials. This study aimed to investigate the effects of DIET on syntrophic propionate oxidization under room temperature (20°C) and reveal the syntrophic partners. Firstly, conventional anaerobic consortium and conductive material-enriched consortium were tested for DIET under high H partial pressure. The latter supplemented with granular activated carbon (GAC) can mitigate H inhibition through DIET. Secondly, a DIET consortium was enriched for testing GAC and magnetite, both showed DIET facilitation. Microbial communities in GAC- and magnetite-supplemented reactors were similar. Syntrophic propionate-oxidizing bacteria, for example, Smithella (3.9%-9.9%) and a genus from the family Syntrophaceae (1.9%-3.6%) and methanogens Methanobacterium (30.3%-75.2%), Methanolinea (8.5%-25.2%), Methanosaeta (11.4%-36.7%), and Candidatus Methanofastidiosum (3.6%-6.6%), were predominant. Functional genes for cell mobility and membrane transport (3.3% and 9.5% in control reactor) increased with GAC (3.7% and 11.1%, respectively) and magnetite (3.7% and 10.9%, respectively) addition. Syntrophic propionate-oxidizing bacteria and methanogenesis partners were revealed by co-occurrence network, for example, Methanobacterium with Smithella, Syntrophobacter, Dechloromonas, and Trichococcus, signifying the importance of the syntrophic partnership in DIET environment. PRACTITIONER POINTS: DIET improved syntrophic propionate oxidization under room temperature condition (20°C). Microbial communities were similar for GAC- and magnetite-supplemented reactors, different with control reactor. Syntrophic propionate-oxidizing bacteria and methanogenesis partners were revealed by co-occurrence network. Methanobacterium and Smithella, Syntrophobacter, Dechloromonas, and Trichococcus were correlated.

Compared with conventionally collected sewage, source-diverted greywater has a higher potential for on-site treatment and reuse due to its lower contaminant levels and large volume. A new design of granular activated carbon (GAC) biofilters was developed by incorporating unsaturated and saturated zones in a single stage to introduce an efficient, passive, and easy-to-operate technology for greywater on-site treatment at the household scale. The design was customized for its intended application considering various aspects including the reactor’s configuration, packing media, and feeding strategy. With the highest hydraulic and organic loadings of 1.2 m3 m−2 d−1 and 3.5 kg COD m−2 d−1, respectively, and the shortest retention time of 2.4 h, the system maintained an average total chemical oxygen demand removal rate of 94% with almost complete removal of nutrients throughout its 253 days of operation. The system showed a range of reduction efficacy towards five surrogates representing viruses, bacteria, and Cryptosporidium and Giardia (oo)cysts. A well-functioning biofilm was successfully developed, and its mass and activity increased over time with the highest values observed at the top layers. The key microbes within the biofilter were revealed. Feasibility of the proposed technology was investigated, and implications for design and operation were discussed.

Ammonia-rich lagoon supernatant has a low alkalinity/nitrogen ratio, which is ideal for single reactor nitritation-denitritation operation. In the present study, an integrated fixed film and activated sludge system in sequencing batch mode (IFAS-SBR) was operated at 21 °C for 140 days. The stability and feasibility of nitritation-denitritation performance was evaluated, and the microbial activities and microbial community dynamics were investigated. With a hydraulic retention time (HRT) of 2 days, the IFAS-SBR achieved a stable inorganic nitrogen removal rate of 98 %. Nitritation and denitritation activities were both higher in suspended flocs as compared to biofilm. The dominant nitrifying and primary denitrifying genera were Nitrosomonas and Thauera, respectively. During long-term operation, the relative richness of Nitrosomonas and Thauera increased in both biofilm (from 0.27 % to 1.12 % and from

A bench-scale oxygen-based membrane biofilm reactor (O2-MBfR) was used to treat greywater for organics and nitrogen removal. Highly dynamic multifunctional biofilm formed on fiber surfaces of the O2-MBfR. With an organics loading up to 4.26 g COD/m2-day, the MBfR successfully achieved simultaneous organics and nitrogen reduction, with average removal ratios of 95% for total chemical oxygen demand (TCOD), 98% for linear alkylbenzene sulfonates (LAS), and 99% for inorganic nitrogen (InON). Increasing feed loading rates led to the gradually decrease of dissolved oxygen (DO) concentration from 1.67 to 0.37 mg/L in the reactor, inducing the formation of complex biofilm containing distinct aerobic, aerobic-anoxic, and aerobic-anoxic-anaerobic layers; these all contributed to the simultaneous removal of both organics and nitrogen in MBfR. Mechanisms of organics and nitrogen removal included nitrification and aerobic denitrification in aerobic biofilm, partial nitrification in the aerobic-anoxic biofilm, and partial nitrification and anaerobic denitrification in the aerobic-anoxic-anaerobic biofilm due to the co-existence of multifarious functional microorganisms in the O2-MBfR. This study lays the foundation of process optimization and cost-cutting for the practical application of O2-MBfR for greywater treatment.

Grey water (GW) containing high levels of linear alkylbenzene sulfonates (LAS) can be a threat to human health and organisms in the environment if not treated properly. Although aerobic treatment could achieve high organics removal efficiency, conventional aeration can lead to serious foaming and energy waste. Here, we systematically evaluated an oxygen based membrane biofilm reactor (O2-MBfR) for its capacity to simultaneously remove organics and nitrogen from GW. The dissolved oxygen (DO) concentration inside the reactor was maintained at 0.4 mg/L by gradually controlling the lumen air pressure. Results showed that the O2-MBfR achieved high removal efficiency of total chemical oxygen demand (TCOD), total linear alkylbenzene sulfonates (LAS) and total nitrogen (TN) of 89.7%, 99.1% and 78.1%, respectively, with a hydraulic retention time (HRT) of 7.5 h. Lower HRT (7.0 h) led to the accumulation of LAS in the biofilm, which caused cell lysis and damaged the O2-MBfR system, leading to a discernible and continuous decline of the reactor performance. The O2-MBfR design completely eliminated foaming formation and the three-dimension oxygen gradient design led to low air pressure inside the membrane fiber, which enabled the high removal efficiency for both organics and nitrogen with low energy input and GW treatment cost, providing the fundamental knowledge for practical application of O2-MBfR in wastewater treatment.

Biomethane recovery from source-diverted blackwater through anaerobic digestion (AD) offers a sustainable alternative for modern wastewater treatment. Water-wasting conventional toilets consume great amounts of flushing water (9 L per flush), which results in blackwater with chemical oxygen demand (COD) of 1006 (±61) mg/L and COD/sulfate ratio of 12.2 (±0.9). In this study, the conventional toilets collected blackwater was treated through an up-flow anaerobic sludge blanket (UASB) reactor at 35 °C with a hydraulic retention time (HRT) of 2.2 days, which achieved a COD removal efficiency >80 %. Inhibition in blackwater methanogenesis was observed, which was found associated with the growth of hydrogen utilizing sulfate reducing bacteria (SRB) that competed with hydrogenotrophic methanogens and suppressed the biomethane recovery efficiency. The sludge specific hydrogenotrophic methanogenic activity (SMA [H2&CO2]) increased from 0.37 (±0.02) g CH4-COD/g volatile suspended solids (VSS)/d (treating high sulfate blackwater) to 0.52 (±0.00) g CH4-COD/g VSS/d (treating low sulfate blackwater) when sulfate-free toilet flushing water was adopted (resulting COD/sulfate ratio of 42.9 [±5.0]). This study underlines the importance of considering the impact of sulfate on blackwater methane production when designing future blackwater treatment processes.

Attached-growth wastewater processes are currently used in water resource recovery facilities (WRRFs) for required upgrades due to an increase in influent loading or to reach more stringent discharge criteria. Yet, the distribution and long-term inhibitory effects of silver nanoparticles (AgNPs) in attached-growth biological wastewater processes and their impact on involved microbial communities are poorly understood at relevant, low concentrations. Retention, distribution, and long-term inhibitory effect of polyvinylpyrrolidone (PVP)-coated AgNPs were evaluated in bench-scale moving bed biofilm reactors (MBBRs), achieving soluble organic matter removal, over a 64 day exposure to nominal concentrations of 10 and 100 μg/L. Distributions of continuously added AgNPs were characterized in the influent, bioreactor, and effluent of MBBRs using single particle inductively coupled plasma mass spectroscopy (spICP-MS). Aerobic heterotrophic biofilms in MBBRs demonstrated limited retention capacity for AgNPs over long-term exposure, with release of AgNPs, and Ag-rich biofilm sloughed from the carriers. Continuous exposure to both influent AgNP concentrations significantly decreased soluble chemical oxygen demand (SCOD) removal efficiency (11% to 31%) and reduced biofilm viability (8% to 30%). Specific activities of both intracellular dehydrogenase (DHA) and extracellular α-glucosidase (α-Glu) and protease (PRO) enzymes were significantly inhibited (8% to 39%) with an observed NP dose-dependent intracellular reactive oxygen species (ROS) production and shift in biofilm microbial community composition by day 64. Our results indicated that long-term exposure to AgNPs in biofilm processes at environmentally relevant concentrations can impact the treatment process stability and the quality of the discharged effluent.

Grey water (GW) containing high levels of linear alkylbenzene sulfonates (LAS) can be a threat to the human health and organisms in the environment if not treated properly. Although aerobic treatment may achieve high GW treatment efficacy, conventional aeration can lead to serious foaming. Here, we firstly and systematically evaluated an oxygen-based membrane biofilm reactor (O2-MBfR) for its capacity to simultaneous remove organics and nitrogen from greywater with high LAS levels and carbon/nitrogen (C/N) ratios. After a five-day startup period, multifarious microorganisms formed multifunctional biofilms and the MBfR achieved high removal rates of chemical oxygen demand (COD), LAS, and total nitrogen (TN) of 88.4%, 95.6%, and 80%, respectively, with a hydraulic retention time of 7.86 h. Higher organics loading (5.53 g TCOD/m2-day) caused cell lysis and damaged the O2-MBfR system, leading to a discernible and continuous decline of the reactor performance. The O2-MBfR design completely eliminated foaming formation. LAS -biodegrading-rich genus containing Clostridium, Parvibaculum, Dechloromonas, Desulfovibrio, Mycobacterium, Pseudomonas, and Zoogloea enable the nearly complete removal of LAS even under high C/N conditions. Results demonstrated that the O2-MBfR technology is feasible for treating GW containing high LAS and C/N ratio, while remaining free of foaming formation, and at a low cost due to high O2 utilization rates.

Blackwater collected from toilets represents a type of sustainable bioenergy resource in the modern sanitation system, while its biomethane recovery efficiencies through anaerobic digestion were limited by slow hydrolysis and inhibited methanogenesis due to a large fraction of solid organics and high free ammonia concentrations. In the current study, food waste and blackwater co-digestion was performed in an up-flow anaerobic sludge blanket (UASB) reactor (35 °C). Co-substrates with increasing food waste proportions were stepwise applied to demonstrate the threshold organic loading rate (OLR). Co-digestion effectively enhanced substrate hydrolysis efficiency by up to 86.1% and methanisation rate by up to 39.7% compared to blackwater mono-digestion. Hydrogenotrophic methanogens showed predominance in both feeding conditions. The dominant bacterial groups shifted from genus Bacteroides to T78, and methanogenic groups shifted from genus Methanogenium to Methanoculleus and Methanospirillum when the operation system shifted from blackwater mono-digestion to food waste co-digestion. The microbial community structures and the isotopic carbon analysis for CH4 and CO2 in the produced biogas indicated that a combined syntrophic acetate oxidation (SAO) and hydrogenotrophic methanogenesis (HM) pathway was established throughout the operation. The enhanced substrates’ properties including higher carbon/nitrogen (C/N) ratios and more readily biodegradable organics in food waste and blackwater co-digestion system contributed to the enhancements in biomethane recovery and microbial development compared to blackwater mono-digestion. The OLR stress under the overloaded condition negatively affected the microbial community structure and resulted in process deterioration.

Thermophilic anaerobic digestion is a promising process for high-solid blackwater (BW) treatment due to improved hydrolysis rates, high methanogenesis efficiency, and pathogen removal, when compared with mesophilic treatment. In the present work, the effects of effluent recirculation (i.e., mixing) on thermophilic blackwater treatment were studied. A laboratory-scale thermophilic upflow anaerobic sludge blanket reactor was operated with and without effluent recirculation. The methanogenesis efficiency of the BW treatment increased from 45.0 ± 2.9% when effluent recirculation was applied to 56.7 ± 5.5% without effluent recirculation. Without effluent recirculation, the COD accumulation in the bioreactor was reduced from 17.2 to 3.8% and the effluent volatile fatty acids (VFA) concentration was reduced from 0.64 ± 0.18 to 0.15 ± 0.10 g/L. Further, both acetoclastic and hydrogenotrophic methanogenic activity increased from 101.3 ± 10.8 and 93.9 ± 6.1 to 120.4 ± 9.4 and 118.2 ± 13.2 mg CH4-COD/(gVSS⋅d), respectively, after effluent recirculation was discontinued. The predominant methanogens changed from Methanothermobacter (67%) with effluent recirculation to Methanosarcina (62%) without effluent recirculation. As compared to the effluent recirculation conditions, the enhanced biomethane recovery and treatment performance without effluent recirculation can be attributed to the close proximity of bacteria and archaea groups and the reduced VFA accumulation. Predicted functional gene comparison showed higher prevalence of function for intermediate metabolite transportation (transporters, ATP-binding cassette (ABC) transporters, and two-component system) after discontinuing effluent circulation, which contributed to improved syntrophic propionate oxidation and syntrophic acetate oxidization and enhanced hydrogenotrophic methanogenesis.

Granular activated carbon (GAC) has been reported to benefit anaerobic digestion systems by stimulating direct interspecies electron transfer (DIET) as an alternative to interspecies hydrogen transfer (IHT). Conventional up-flow anaerobic sludge blanket (UASB) reactors typically have GAC settled at the bottom of the reactor, limiting the contact between biomass and GAC. This study demonstrated a modified UASB reactor that fluidizes GAC by encaging GAC in plastic carriers. Enhanced performance was achieved with respect to methane production and COD removal at an organic loading rate of 1500 g COD/m3/d under the temperature of 20 °C using the self-fluidized GAC configuration; with the methanation rate increased from 0.33 ± 0.08 g CH4-COD/g influent COD in the non-GAC reactor, to 0.66 ± 0.02 g CH4-COD/g influent COD in the GAC-only reactor, and further increased to 0.77 ± 0.02 g CH4-COD/g influent COD in the self-fluidized GAC reactor. The concentrations of medium-chain acyl-homoserine lactones increased in the GAC-amended reactors, potentially associated with the promotion of syntrophic interactions between bacteria and archaea. Batch tests were performed for syntrophic propionate degradation under hydrogen-inhibition conditions, and showed that microbial consortium enriched in both GAC amended reactors can overcome hydrogen inhibition. Further microbial community analysis unveiled a variation in spatial distribution in the GAC enriched microbial consortium (including DIET indicator microorganisms such as Geobacter and Methanosarcina) based on the location of GAC in the reactors. This study demonstrated an improved GAC amendment strategy in UASB reactors to facilitate biomethane recovery from wastewater anaerobic digestion.

Activated sludge (AS) microbial communities were analyzed for seasonal variation, a disturbance-recovery event, and separated small aggregates (SAG) to study the influent immigration effect using both neutral immigration model and mass-balance model with operational parameters. SAG differed with AS, and higher immigration impact on SAG was confirmed by both models. Adding the SAG community segregation in the latter model to evaluate the contribution of influent immigration to community disturbance-recovery showed increased impact of immigration.

Short-time aerobic digestion (STAD) was proved to promote the reduction of waste activated sludge (WAS). This study systematically disclosed the influential characteristics and mechanisms of linear alkylbenzene sulfonates (LAS) dosage on the reduction of WAS in STAD system. Flow cytometer (FC) combined with SYTOX Green (SG) dye was used to differentiate extracellular polymeric substances (EPS) release and cell lysis of WAS during STAD process. LAS lower than 0.10 g/g total suspended solids (TSS) brought about EPS solubilization and the decrease of sludge floc size, and the accumulated soluble microbial products (SMP) could be biodegraded by heterotrophs. Moreover, the activity of microorganisms (denoted as specific oxygen uptake rate (SOUR)) and proportion of bacteria functional for LAS and SMP biodegradation dramatically increased, leading to a high LAS biodegradation rate (kLAS) and increased WAS biodegradation rate (kCOD, WAS). Even more LAS (> 0.10 g/g TSS) caused cell lysis, leading to the decreased kTCOD and kLAS, and therefore inhibit the reduction of WAS. High WAS reduction and LAS biodegradation rate were achieved at the LAS dosage of 0.10 g/g TSS in STAD system. This study lays the foundation for improving WAS reduction by optimizing surfactant dose in STAD system.

Herein we proposed an ecology model, based on a non-steady-state mass balance (16S rRNA MiSeq reads normalized by volatile suspended solids), to quantify microbiome responses to disturbances in wastewater bioreactors. Rather than focusing on the most abundant microbial groups commonly used in the literature, the goal of the model was to identify active species within the community. The model incorporated the temporal changes of operational taxonomic units following a disturbance, through considering the density and type of genotypes in the influent entering the bioreactor, in the effluent leaving the bioreactor, growing in the bioreactor, and in the waste sludge discharged from the bioreactor continuously or instantaneously, as well as the prior microbial community and the sludge characteristics. One application of this model demonstrated that significant differences existed between the key populations responding to an increasing organic loading rate and the dominant species in a high-rate thermophilic upflow anaerobic sludge blanket reactor.

Wastewater contains microorganisms coming from various sources, e.g. feces discharges, soil infiltrations and sewer biofilms and sediments. The primary objective of this work was to determine if end-of-pipe wastewater microbial community structures exhibits short-timescale variation, and assess possible microbial origins. To this end, we measured hourly physicochemical characteristics of wastewater influent for 2 days and analyzed the microbial community at 4-h intervals using 16S rRNA gene amplicon sequencing. Results showed large variations in the microbial community composition at phylum and genus levels, i.e. Proteobacteria ranged from 44 to 63% of the total relative abundance and Arcobacter ranged from 11 to 22%. Diurnal patterns were observed in the alpha-diversity, beta-diversity and the prevalence of several taxa. Wastewater physicochemical characteristics explained 61% of the total microbial community variance by Canonical Correspondence Analysis (CCA), with flow rate being the main explanatory variable exhibiting a clear diurnal profile. Comparison with public databases using closed reference OTUs revealed that only 7.3% of the sequences were shared with human gut microbiota and 21.7% with soil microbiota, the majority being from the sewer biofilms and sediments. The functional trait, weighted average ribosomal RNA operon (rrn) copy number per genome, was found to be relatively high in the wastewater microbiota (average 3.6, soil 2.1, and human gut 2.6) and significantly correlated with flow, inferring active microbial enrichments in the sewer. The prevalence of Methylophilaceae, methanol oxidation genes and denitrification genes were related to high influent methanol and NO concentration in the influent wastewater. These functional organisms and genes indicate important carbon and nutrient removal related functions in the sewer. Together, the observed temporal patterns of the microbial community and functional traits suggest that high wastewater flow causes greater transport of active sewer microorganisms which are functionally important.

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.

Source diverted blackwater collected from toilets can be anaerobically digested to recover energy. The anaerobically digested blackwater (ADB) contains high levels of ammonium and low carbon to nitrogen (C/N) ratio. In the present study, ADB was treated by a two-stage nitritation-denitrification/anammox process in an integrated fixed film activated sludge-continuous flow reactor (IFAS-CFR). NH4+-N, NO2--N, total nitrogen (TN), and chemical oxygen demand (COD) removal efficiencies were 80%, 82%, 76%, and 78%, respectively. Anaerobic ammonium oxidation (anammox) and denitrification contributed to 44–48%, and 52–56% of total nitrogen removal, respectively. Both of the protein- and humic acid-like matters were removed during the process. An increase in feed load promoted the sustained growth of anammox bacteria—Candidatus Brocadia in the biofilm, as well as an increase of denitrifiers (Pseudomonas, Thermotonus, Phodanobacter, Caulobacter) in both biofilm and suspended biomass, which remained higher in the suspended biomass than in biofilm. Overall, biofilm had higher nitrogen removal efficiency than suspended biomass, while suspended biomass had a higher COD removal efficiency than biofilm.

Decentralized wastewater treatment represents a promising sustainable option for future wastewater management. Blackwater collected from toilets contains high concentrations of organic matter, ideal for energy recovery using anaerobic digestion. Up-flow anaerobic sludge blanket (UASB) reactors treating conventional toilet (CT, 9 L water per flush) and vacuum toilet (VT, 1 L water per flush) blackwater with increments of loadings were successfully operated to steady state in three phases. The organic loading rates were maintained at comparable levels between the two reactors. The methanisation rates were 0.23-0.29 and 0.41-0.48 gCH -COD/gfeedCOD in the CT and VT reactors, and the COD removal rates were 72% and 89%, respectively. The enriched microbial consortia and the community dynamics under different loading phases were compared. The rank abundance distributions and alpha-diversity showed that archaeal communities were predominated by mono-enrichments in both CT and VT reactors, while bacterial communities showed lower diversity in the VT reactor. Through principal coordinates analysis (beta-diversity), clear divergences of archaeal and bacterial communities between the CT and VT reactors were revealed, and the archaeal community developed at a slower rate than the bacterial community. The enriched archaea were hydrogenotrophic methanogens, Methanolinea in the CT reactor (56.6%), and Methanogenium in the VT reactor (62.3%). The enriched bacteria were Porphyromonadaceae in both CT (15.9%) and VT (13.4%) reactors, sulfate-reducing bacteria in the CT reactor, and Fibrobacteraceae in the VT reactor (13.8%). Links between enriched consortia and ammonia stress were discussed. Isotope fraction analysis of the biogas showed a slight shift from acetoclastic methanogenesis to hydrogenotrophic methanogenesis. A closer look into the predicted metagenomic functional profiles showed agreeing results, where hydrogenotrophic methanogenesis and fhs gene abundances were higher in the VT reactor. We demonstrated that different blackwater types enriched different microbial consortia, probably due to ammonia concentrations and sulfate loadings, which should be taken into consideration for practical applications.

The effects of micro-aeration on the performance of anaerobic sequencing batch reactors (ASBR) for blackwater treatment were investigated in this study. Different micro-aeration rates, 0, 5, 10, 50, and 150 mg O2/L-reactor/cycle, and their effect on the hydrolysis, acidogenesis, and methanogenesis of blackwater were evaluated and compared at ambient temperature. Source-diverted blackwater (toilet water) contains high organic contents which can be recovered as biogas. Previous studies have found that anaerobic digestion of blackwater without micro-aeration can only recover upwards of less than 40% of chemical oxygen demand (COD) to methane at room temperature due to the low hydrolysis rate of biomass content in blackwater. This study achieved increases in blackwater hydrolysis (from 34.7% to 48.7%) and methane production (from 39.6% to 50.7%) with controlled micro-aeration (5 mg O2/L-reactor/cycle). The microbial analysis results showed that hydrolytic/fermentative bacteria and acetoclastic methanogens (e.g. Methanosaeta) were in higher abundances in low-dose micro-aeration reactors (5 and 10 mg O2/L-reactor/cycle), which facilitated syntrophic interactions between microorganisms. The relative abundance of oxygen-tolerant methanogen such as Methanosarcina greatly increased (from 1.5% to 11.4%) after oxygen injection. High oxygen dosages (50 and 150 mg O2/L-reactor/cycle) led to reduced methane production and higher accumulation of volatile fatty acids, largely due to the oxygen inhibition on methanogens and degradation of organic matters by aerobic growth and respiration, as indicated by the predicted metagenome functions. By combining reactor performance results and microbial community analyses, this study demonstrated that low-dose micro-aeration improves blackwater biomethane recovery by enhancing hydrolysis efficiency and promoting the development of a functional microbial population, while medium to high-dose micro-aeration reduced the activities of certain anaerobes. It was also observed that medium-dose micro-aeration maximizes VFA accumulation, which may be used in two-stage anaerobic digesters.

The addition of granular activated carbon (GAC) enhanced the performance of up-flow anaerobic sludge blanket (UASB) reactor treating blackwater at 35 °C. DNA were extracted from the sludge and biofilms attached to GAC and submitted for shotgun sequencing. In addition, the acyl-homoserine lactones (AHLs) were quantified. Diverse partners for direct interspecies electron transfer (DIET) were enriched in the sludge or biofilm (GAC-biofilm) of GAC amended UASB. Pedosphaera parvula, Syntrophus aciditrophicus and Syntrophorhabus aromaticivorans were dominant syntrophs. The analysis for type IV pilus assembly genes further suggested DIET may be functioned through GAC for GAC-biofilm, while through conductive pili for sludge aggregates. AHLs quantification and the analysis for quorum sensing (QS) related genes indicated higher QS activity at the population level was induced by GAC. Overall, the work illustrated the different DIET patterns, and suggested that QS played an important role in controlling the performance in GAC amended USAB.