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Mixed community microalgal wastewater treatment technologies have the potential to advance the limits of technology for biological nutrient recovery while producing a renewable carbon feedstock, but a deeper understanding of their performance is required for system optimization and control. In this study, we characterized the performance of a 568 m 3 ·day -1 Clearas EcoRecover system for tertiary phosphorus removal (and recovery as biomass) at an operating water resource recovery facility (WRRF). The process consists of a (dark) mix tank, photobioreactors (PBRs), and a membrane tank with ultrafiltration membranes for the separation of hydraulic and solids residence times. Through continuous online monitoring, long-term on-site monitoring, and on-site batch experiments, we demonstrate (i) the importance of carbohydrate storage in PBRs to support phosphorus uptake under dark conditions in the mix tank and (ii) the potential for polyphosphate accumulation in the mixed algal communities. Over a 3-month winter period with limited outside influences (e.g., no major upstream process changes), the effluent total phosphorus (TP) concentration was 0.03 ± 0.03 mg-P·L -1 (0.01 ± 0.02 mg-P·L -1 orthophosphate). Core microbial community taxa included Chlorella spp. , Scenedesmus spp. , and Monoraphidium spp. , and key indicators of stable performance included near-neutral pH, sufficient alkalinity, and a diel rhythm in dissolved oxygen.

Per and polyfluoroalkyl substances (PFAS) present a unique challenge to remediation techniques because their strong carbon-fluorine bonds make them difficult to degrade. This review explores the use of in silico enzymatic design as a potential PFAS degradation technique. The scope of the enzymes included is based on currently known PFAS degradation techniques, including chemical redox systems that have been studied for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) defluorination, such as those that incorporate hydrated electrons, sulfate, peroxide, and metal catalysts. Bioremediation techniques are also discussed, namely the laccase and horseradish peroxidase systems. The redox potential of known reactants and enzymatic radicals/metal-complexes are then considered and compared to potential enzymes for degrading PFAS. The molecular structure and reaction cycle of prospective enzymes are explored. Current knowledge and techniques of enzyme design, particularly radical-generating enzymes, and application are also discussed. Finally, potential routes for bioengineering enzymes to enable or enhance PFAS remediation are considered as well as the future outlook for computational exploration of enzymatic in situ bioremediation routes for these highly persistent and globally distributed contaminants.

The sequencing of human virus genomes from wastewater samples is an efficient method for tracking viral transmission and evolution at the community level. However, this requires the recovery of viral nucleic acids of high quality. We developed a reusable tangential-flow filtration system to concentrate and purify viruses from wastewater for genome sequencing. A pilot study was conducted with 94 wastewater samples from four local sewersheds, from which viral nucleic acids were extracted, and the whole genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was sequenced using the ARTIC V4.0 primers. Our method yielded a high probability (0.9) of recovering complete or near-complete SARS-CoV-2 genomes (>90% coverage at 10× depth) from wastewater when the COVID-19 incidence rate exceeded 33 cases per 100 000 people. The relative abundances of sequenced SARS-CoV-2 variants followed the trends observed from patient-derived samples. We also identified SARS-CoV-2 lineages in wastewater that were underrepresented or not present in the clinical whole-genome sequencing data. The developed tangential-flow filtration system can be easily adopted for the sequencing of other viruses in wastewater, particularly those at low concentrations., Competing Interests: The authors declare no competing financial interest.

The use of wastewater-grown microalgae has the potential to reduce the cost of algae-derived biofuels while simultaneously advancing nutrient recovery at water resource recovery facilities (WRRFs). However, a significant barrier has been the low yield and high protein content of phototrophic biomass. Here, we examine the use of solids residence time (SRT) as a selective pressure in driving biochemical composition, yield, biofuel production, and WRRF nutrient management cost. We cultivated mixed phototrophic communities in controlled, laboratory-scale photobioreactors on the local WRRF secondary effluent to link SRT with biochemical composition and techno-economic analysis to yield insights into biomass composition and downstream processing effects on minimum fuel selling price. SRT significantly impacted biochemical composition, with total and dynamic carbohydrates the highest at low SRT (total carbohydrates being 0.60 and 0.32 mg-carbohydrate·mg-protein -1 at SRT 5 and 15 days, respectively). However, there were distinct differences between extant, steady-state performance and intrinsic potential, and longer SRT communities were able to accumulate significant fractions (51% on an ash-free dry weight basis, AFDW %) of carbohydrate reserves under nutrient starvation. Overall, hydrothermal liquefaction (HTL) was found to be more suitable than lipid extraction for hydrotreating (LEH) and combined algal processing (CAP) for conversion of biomass to fuels, but LEH and CAP became more competitive when intrinsic carbon storage potential was realized. The results suggest that the use of algae for nutrient recovery could reduce the nutrient management cost at WRRFs through revenue from algal biofuels, with HTL resulting in a net revenue.

The capacity of microalgae to advance the limit of technology of nutrient recovery and accumulate storage carbon make them promising candidates for wastewater treatment. However, the extent to which these capabilities are influenced by microbial community composition remains poorly understood. To address this knowledge gap, 3 mixed phototrophic communities sourced from distinct latitudes within the continental United States (28° N, Tampa, FL; 36° N, Durham, NC; and 40° N, Urbana, IL) were operated in sequencing batch reactors (8 day solids residence time, SRT) subjected to identical diel light cycles with media addition at the start of the nighttime period. Despite persistent differences in community structure as determined via 18S rRNA (V4 and V8-V9 hypervariable regions) and 16S rRNA (V1-V3) gene amplicon sequencing, reactors achieved similar and stable nutrient recovery after 2 months (8 SRTs) of operation. Intrinsic carbohydrate and lipid storage capacity and maximum specific carbon storage rates differed significantly across communities despite consistent levels of observed carbon storage across reactors. This work supports the assertion that distinct algal communities cultivated under a common selective environment can achieve consistent performance while maintaining independent community structures and intrinsic carbon storage capabilities, providing further motivation for the development of engineered phototrophic processes for wastewater management.

This study evaluated the role of physical and biological filter characteristics on the reduction of MS2 bacteriophage in biosand filters (BSFs). Three full-scale concrete Version 10 BSFs, each with a 55 cm sand media depth and a 12 L charge volume, reached 4 log10 reduction of MS2 within 43 days of operation. A consistently high reduction of MS2 between 4 log10 and 7 log10 was demonstrated for up to 294 days. Further examining one of the filters revealed that an average of 2.8 log10 reduction of MS2 was achieved within the first 5 cm of the filter, and cumulative virus reduction reached an average of 5.6 log10 after 240 days. Core sand samples from this filter were taken for protein, carbohydrate, and genomic extraction. Higher reduction of MS2 in the top 5 cm of the sand media (0.56 log10 reduction per cm vs 0.06 log10 reduction per cm for the rest of the filter depth) coincided with greater diversity of microbial communities and increased concentrations of carbohydrates. In the upper layers, "Candidatus Nitrosopumilus maritimus" and "Ca. Nitrospira defluvii" were found as dominant populations, while significant amounts of Thiobacillus-related OTUs were detected in the lower layers. Proteolytic bacterial populations such as the classes Sphingobacteria and Clostridia were observed over the entire filter depth. Thus, this study provides the first insight into microbial community structures that may play a role in MS2 reduction in BSF ecosystems. Overall, besides media ripening and physical reduction mechanisms such as filter depth and long residence time (45 min vs 24 ± 8.5 h), the establishment of chemolithotrophs and proteolytic bacteria could greatly enhance the reduction of MS2.