The fate of severe acute respiratory syndrome coronavirus-2 and pepper mild mottle virus at various stages of wastewater treatment process.

This study investigated the efficiency of the treatment processes of wastewater treatment plants (WWTPs) to remove severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and pepper mild mottle virus (PMMoV) from the wastewater and sewage sludge, as well as the influence of the mode of operation on the quality of the treated wastewater. SARS-CoV-2 and PMMoV were detected and quantified at different stages of the wastewater and sludge treatment process of three major WWTPs in Stockholm, Sweden. The results showed that primary, biological, and advanced membrane treatment processes are effective in removing SARS-CoV-2 from the wastewater with removal efficiencies of 99-100 % for all WWTPs, while the virus was accumulated in the primary and waste-activated sludges due to higher affinity to biosolids. Operation strategies such as bypass reintroduced the virus into the treated wastewater. The WWTPs achieved relatively low PMMoV removal efficiencies (63-87 %) most probably due to the robust capsid structure of the virus. Anaerobic digestion could not completely remove SARS-CoV-2 and PMMoV from the sludge leading to increased levels of SARS-CoV-2 and PMMoV in dewatered sludge. The study gives an overview of WWTPs' role in tackling pathogen spread in society in the event of a pandemic and disease breakout.

Pre-concentration of ammonium to enhance treatment of wastewater using the partial nitritation/anammox process.

The anaerobic ammonium oxidation (anammox) process is one of the most cost-effective technologies for removing excessive nitrogen compounds from effluents of wastewater treatment plants. The study was conducted to assess the feasibility of using ion exchange (IE) and reverse osmosis (RO) methods to concentrate ammonium to support partial nitritation/anammox process, which so far has been used for treating only wastewater with high concentrations of ammonium. Upflow anaerobic sludge blanket (UASB) reactor effluents with 40.40, 37.90 and 21.80 mg NH4─N/L levels were concentrated with IE method to 367.20, 329.50 and 187.50 mg NH4─N/L, respectively, which were about nine times the initial concentrations. RO method was also used to concentrate 41.0 mg NH4─N/L of UASB effluent to 163 mg NH4─N/L at volume reduction factor 5. The rates of nitrogen removal from respective RO pretreated concentrates by partial nitritation/anammox technology were 0.60, 1.10 and 0.50 g N/m2 day. The rates were largely influenced by initial nitrogen concentration. However, rates of RO concentrates were 0.74, 0.92 and 0.81 g N/m2 day even at lower initial NH4─N concentration. It was found out from the study that higher salinity decreased the rate of nitrogen removal when using partial nitritation/anammox process. Dissolved oxygen concentration of ∼1 mg/L was optimal for the operation of the partial nitritation/anammox process when treating IE and RO concentrates. The result shows that IE and RO methods can precede a partial nitritation/anammox process to enhance the treatment of wastewater with low ammonium loads.

Discovery of sulfonamide resistance genes in deep groundwater below Patna, India.

Global usage of pharmaceuticals has led to the proliferation of bacteria that are resistant to antimicrobial treatments, creating a substantial public health challenge. Here, we investigate the emergence of sulfonamide resistance genes in groundwater and surface water in Patna, a rapidly developing city in Bihar, India. We report the first quantification of three sulfonamide resistance genes (sulI, sulII and sulIII) in groundwater (12-107 m in depth) in India. The mean relative abundance of gene copies was found to be sulI (2.4 × 10-2 copies/16S rRNA gene) > sulII (5.4 × 10-3 copies/16S rRNA gene) > sulIII (2.4 × 10-3 copies/16S rRNA gene) in groundwater (n = 15) and surface water (n = 3). A comparison between antimicrobial resistance (AMR) genes and wastewater indicators, particularly tryptophan:fulvic-like fluorescence, suggests that wastewater was associated with AMR gene prevalence. Urban drainage channels, containing hospital and domestic wastes, are likely a substantial source of antimicrobial resistance in groundwater and surface water, including the Ganges (Ganga) River. This study is a reference point for decision-makers in the fight against antimicrobial resistance because it quantifies and determines potential sources of AMR genes in Indian groundwater.

Conceptual system for sustainable and next-generation wastewater resource recovery facilities.

Shifting the concept of municipal wastewater treatment to recover resources is one of the key factors contributing to a sustainable society. A novel concept based on research is proposed to recover four main bio-based products from municipal wastewater while reaching the necessary regulatory standards. The main resource recovery units of the proposed system include upflow anaerobic sludge blanket reactor for the recovery of biogas (as product 1) from mainstream municipal wastewater after primary sedimentation. Sewage sludge is co-fermented with external organic waste such as food waste for volatile fatty acids (VFAs) production as precursors for other bio-based production. A portion of the VFA mixture (product 2) is used as carbon sources in the denitrification step of the nitrification/denitrification process as an alternative for nitrogen removal. The other alternative for nitrogen removal is the partial nitrification/anammx process. The VFA mixture is separated with nanofiltration/reverse osmosis membrane technology into low-carbon VFAs and high-carbon VFAs. Polyhydroxyalkanoate (as product 3) is produced from the low-carbon VFAs. Using membrane contactor-based processes and ion-exchange techniques, high-carbon VFAs are recovered as one-type VFA (pure VFA) and in ester forms (product 4). The nutrient-rich fermented and dewatered biosolid is applied as a fertilizer. The proposed units are seen as individual resource recovery systems as well as a concept of an integrated system. A qualitative environmental assessment of the proposed resource recovery units confirms the positive environmental impacts of the proposed system.

Long-term alkaline volatile fatty acids production from waste streams: Impact of pH and dominance of Dysgonomonadaceae.

Alkaline co-fermentation of primary sludge and external organic waste (OW) was studied to elucidate the influence of substrate ratios and long-term system robustness and microbial community dynamics using batch and semi-continuous reactors. Volatile fatty acid (VFA) production increased with increasing OW fraction in the substrate due to synergistic effects of co-degradation. VFA production at pH 10 increased up to 30,300 mgCOD/L (yield of 630 mg COD/gVSfed) but reduced over time to ≈10,000 mgCOD/L. Lowering pH to 9 led to the restoration of VFA production with a maximum of 32,000 mg COD/L (676 mg COD/g VSfed) due to changes in microbial structure. VFA was composed mainly of acetic acid, but propionic acid increased at pH 9. The microbial community was dominated by Bacillaceae (34 ± 10%) and Proteinivoracales_uncultured (16 ± 11%) at pH 10, while Dysgonomonadaceae (52 ± 8%) was enriched at pH 9. The study demonstrated a zero-waste strategy that turns organic wastes into bio-based products.

A pilot-scale study of granule-based anaerobic reactors for biogas recovery from municipal wastewater under sub-mesophilic conditions.

The influence of hydraulic retention time (HRT of 3-5 h) and temperature (20-25 °C) on performance and microbial dynamics of two pilot-scale upflow anaerobic sludge blanket (UASB) reactors with different granule size distribution (UASB1 = 3-4 mm and UASB2 = 1-2 mm) were investigated for 217 days. Increasing the HRT to 5 h even at a lower temperature of 20 °C enhanced COD removal and biogas production with average of 59 ± 16% (up to 85%) and 73 ± 9 L/(m3·d) (up to 102 L/(m3·d)) for UASB1; 63 ± 16% (up to 85%) and 75 ± 9 L/(m3·d) (up to 90 L/(m3·d)) for UASB2, respectively. This is explained by sufficient contact time between microorganisms and substrate. Acetoclastic methanogenic activity was higher in UASB1 because Methanosaetaceae (produces methane from acetate) dominated (64 ± 4%). However, Methanoregulaceae (29 ± 3%) and Methanomicrobiales_unassigned (20 ± 6%) which produce methane from H2/CO2 and formate were significant in UASB2. The extent of change in the microbial dynamics with HRT and temperature was more obvious in the smaller granule reactor.

Waste to bioplastics: How close are we to sustainable polyhydroxyalkanoates production?

Increased awareness of environmental sustainability with associated strict environmental regulations has incentivized the pursuit of novel materials to replace conventional petroleum-derived plastics. Polyhydroxyalkanoates (PHAs) are appealing intracellular biopolymers and have drawn significant attention as a viable alternative to petrochemical based plastics not only due to their comparable physiochemical properties but also, their outstanding characteristics such as biodegradability and biocompatibility. This review provides a comprehensive overview of the recent developments on the involved PHA producer microorganisms, production process from different waste streams by both pure and mixed microbial cultures (MMCs). Bio-based PHA production, particularly using cheap carbon sources with MMCs, is getting more attention. The main bottlenecks are the low production yield and the inconsistency of the biopolymers. Bioaugmentation and metabolic engineering together with cost effective downstream processing are promising approaches to overcome the hurdles of commercial PHA production from waste streams.

Production of volatile fatty acids through co-digestion of sewage sludge and external organic waste: Effect of substrate proportions and long-term operation.

Volatile fatty acids (VFAs) are intermediates of anaerobic digestion with high value and wide range of usage. Co-digestion of sewage sludge and external organic waste (OW) for VFA production can help achieve both resource recovery and ensure sustainable and innovative waste management. In view of this, the effect of substrate proportions on VFA production from co-digestion of primary sewage sludge and OW is studied. Long-term operation in a semi-continuous reactor was performed to assess the resilience of such a system and the VFA-rich effluent was tested for its ability to be used as carbon source for denitrification. Co-digestion was initially carried out in batch reactors with OW proportion of 0%, 25%, 50%, 75%, 100% in terms of COD and scaled up in a semi-continuous reactor operation with 50% OW. In the short-term operation in the batch mode, acetic acid dominated, however, increasing OW fraction resulted in increased valeric and caproic acid production. Moreover, in the long-term semi-continuous operation, caproic acid dominated, accounting for ≈55% of VFAs. The VFA-rich effluent from the semi-continuous reactor achieved the highest denitrification rate as a carbon source when compared with acetic acid and methanol. The results demonstrate that co-fermentation can increase VFA yield and shift products from acetic acid to caproic acid in long-term operation and the VFAs can be used within wastewater treatment plants to close the loop.

The study of structure of anaerobic granules and methane producing pathways of pilot-scale UASB reactors treating municipal wastewater under sub-mesophilic conditions.

This study was carried out to investigate the relationship between the methane producing pathways and the characteristics of anaerobic granules treating municipal wastewater. For this purpose, two pilot scale upflow anaerobic sludge blanket reactors with different granule size distribution (1-2 mm and 3-4 mm) were investigated at operating temperatures of 20 °C and 28 °C for 239 days. There was an increased and stable biogas production when temperature was elevated to 28 °C likely due to reduction in methane solubility. Larger granules had multi-layered internal microstructures with higher acetoclastic methanogenic activities (250-437 mL CH4 g-1 VS d-1) than smaller granules (150-260 mL CH4 g-1 VS d-1). The relative abundance of acetoclastic methanogens of larger granules was higher, confirming acetoclastic methane producing pathway was more prominent. However, there was no significant difference in the performance of the two reactors because they were operating below their capacities in terms of organic loading rate to volatile solids ratio.

Removal of fluoride and natural organic matter from natural tropical brackish waters by nanofiltration/reverse osmosis with varying water chemistry.

In the context of decentralised brackish water treatment in development applications, the influence of water quality on membrane separation was investigated with real waters. High ionic strength (low net driving pressure) on fluoride (F) retention by nanofiltration (NF) and reverse osmosis (RO) was investigated over a wide pH range (2-12). Further, the influence of pH on the permeation of natural organic matter (NOM) fractions, in particular low molecular weight (LMW) neutrals, was elucidated. Natural and semi-natural waters from Tanzania with similar F concentrations of about 50 mg L-1 but varying NOM and inorganic carbon (IC) concentration were filtered with an NF and RO, namely NF270 and BW30. F retention by NF270 for the feed water with highest ionic strength and IC concentration was lower and attributed to charge screening. This parameter further reduced at high pH due to co-ions (F- and CO32-) interactions and combined (synergistic) effect of high salt concentration and pH on F. High NOM resulted in higher membrane zeta potential in comparison with low NOM natural water. However, there was no significant difference in F retention due to the fact that F retention enhancement was annulled by deposit formation on the membrane. The fraction of NOM found in NF/RO permeates was dominated by LMW neutrals. This was attributed to their size and uncharged nature, while their higher concentration at low pH remains unexplained. More humic substances (HS) of higher molecularity and aromaticity permeated the NF270 when compared with BW30, which can be explained with the different membrane molecular weight cut off (MWCO). The study highlights the complexity of treating tropical natural waters with elevated F and NOM concentrations. In order to develop appropriate membrane systems that will achieve optimal F and NOM removal, the influence of water quality parameters such as pH, NOM content, ionic strength and IC concentration requires understanding. Seasonal variation of water quality as well as operational fluctuations, which occur in particular when such treatment processes are operated with renewable energy, will require such challenges to be addressed. Further, given the high permeability of low molecular weight (LMW) organics significant permeate side fouling may be expected.

Bio-based volatile fatty acid production and recovery from waste streams: Current status and future challenges.

Bio-based volatile fatty acid (VFA) production from waste-stream is getting attention due to increasing market demand and wide range usage area as well as its cost-effective and environmentally friendly approach. The aim of this paper is to give a comprehensive review of bio-based VFA production and recovery methods and to give an opinion on future research outlook. Effects of operation conditions including pH, temperature, retention time, type of substrate and mixed microbial cultures on VFA production and composition were reviewed. The recovery methods in terms of gas stripping with absorption, adsorption, solvent extraction, electrodialysis, reverse osmosis, nanofiltration, and membrane contractor of VFA were evaluated. Furthermore, strategies to enhance bio-based VFA production and recovery from waste streams, specifically, in-line VFA recovery and bioaugmentation, which are currently not used in common practice, are seen as some of the approaches to enhance bio-based VFA production.

Renewable energy powered membrane technology: Impact of pH and ionic strength on fluoride and natural organic matter removal.

Real water pH and ionic strength vary greatly, which influences the performance of membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Systematic variation of pH (3-12) and ionic strength (2-10g/L as total dissolved solids (TDS)) was undertaken with a real Tanzanian water to investigate how water quality affects retention mechanisms of fluoride (F) and natural organic matter (NOM). An autonomous solar powered NF/RO system driven by a solar array simulator was supplied with constant power from a generator. An open NF (NF270) and a brackish water RO (BW30) membrane were used. A surface water with a very high F (59.7mg/L) and NOM (110mgC/L) was used. Retention of F by NF270 was <20% at pH <6, increased to 40% at pH6, and 60-70% at pH7-12, indicating a dominance of charge repulsion while being ineffective in meeting the guideline of 1.5mg/L. Increase in ionic strength led to a significant decline in retention of F (from 70 to 50%) and electrical conductivity (from 60 to 10%) by NF270, presumably due to charge screening. In contrast, BW30 retained about 50% of F at pH3, >80% at pH4, and about 99% at pH >5, due to the smaller pore size and hence a more dominant size exclusion. In consequence, only little impact of ionic strength increase was observed for BW30. The concentration of NOM in permeates of both NF270 and BW30 were typically <2mg/L. This was not affected by pH or ionic strength due to the fact that the bulk of NOM was rejected by both membranes through size exclusion. The research is carried out in the context of providing safe drinking water for rural and remote communities where infrastructure is lacking, and water quality varies significantly. While other studies focus on energy fluctuations, this research emphasises on feed water quality that affects system performance and may alter due to a number of environmental factors.