Wastewater Treatment Works Research Articles

Per- and poly-fluoroalkyl substances in aquatic ecosystems and wastewater treatment works in Africa: Occurrence, ecological implications, and future perspectives

The increasing levels of industrialization and urbanization have led to the generation of significant amounts of wastewater and waste products, often containing chemicals like per- and poly-fluoroalkyl substances (PFASs) commonly found in consumer products. PFASs are known for their persistence, ubiquity, and ecotoxicological impacts, raising concerns about potential harm to ecosystems. This paper reports the occurrence and evaluates the ecological risks of PFASs in aquatic ecosystems and wastewater treatment works (WWTWs) across Africa. We reviewed 32 papers published in the period 2009–2024 and identified a total of 35 PFAS compounds in surface waters, wastewater, sediments, fish, crocodiles, and invertebrates. Much of the reported studies came from South Africa, followed by Kenya and Nigeria. PFAS concentrations in Africa were <0.7–390.0 ng L−1 in surface waters, 0.05–772 ng g−1 dw in sediments, and <0.2–832 ng L−1 in wastewater, while the highest levels in fish and invertebrates were 460.7 and 35.5 ng g−1 ww, respectively. The PFAS levels were in the same range of data as those reported globally. However, the high concentrations of PFASs in sediments and wastewater suggest areas of point contamination and a growing risk to aquatic ecosystems from effluent discharges. Calculated risk quotients suggested that, in Africa, organisms in river systems face greater risks due to exposure to PFASs compared to those in lakes, while marine organisms might face higher risks compared to freshwater organisms. Future studies should focus on PFAS contamination sources, especially WWTWs, as emerging sources of PFASs in aquatic systems.

Wastewater monitoring of human and avian influenza A viruses in Northern Ireland: a genomic surveillance study

Influenza Aviruses (IAVs) are significant pathogens of humans and other animals. Although endemic in humans and birds, novel IAV strains can emerge, jump species, and cause epidemics, like the latest variant of H5N1. Wastewater-based epidemiology (WBE) has been shown capable of detecting human IAVs. We aimed to assess whether whole-genome sequencing (WGS) of IAVs from wastewater is possible and can be used to discriminate between circulating strains of human and any non-human IAVs, such as those of avian origin. Using a pan-IAV RT-quantitative PCR assay, six wastewater treatment works (WWTWs) across Northern Ireland were screened from Aug 1to Dec 5, 2022. Ananopore WGS approach was used to sequence RT-qPCR-positive samples. Phylogenetic analysis of sequences relative to currently circulating human and non-human IAVs was performed. Forcomparative purposes, clinical data (PCR test results) were supplied by The Regional Virus Laboratory, Belfast Health and Social Care Trust (Belfast, Northern Ireland, UK). We detected a dynamic IAV signal in wastewater from Sept 5, 2022, onwards across Northern Ireland, which did not show a clear positive relationship with the clinical data obtained for the region. Meta (mixed strain) whole-genome sequences were generated from wastewater samples displaying homology to only human and avian IAVstrains. The relative proportion of IAV reads of human versus avian origin differed across time and sample site. Adiversity in subtypes and lineages was detected (eg, H1N1, H3N2, and several avian). Avian segment 8related to those found in recent H5N1 clade 2.3.4.4b was identified. WBE affords a means to monitor circulating human and avian IAV strains and provide crucial genetic information. As such, WBE can provide rapid, cost-effective, year-round One Health surveillance to help control IAV epidemic and pandemic-related threats. However, optimisation of WBE protocols are necessary to ensure observed wastewater signals not only correlate with clinical case data, but yield information on the wider environmental pan-influenz-ome. Department of Health for Northern Ireland.

Quantifying the relative importance of agricultural land use as a predictor of catchment nitrogen and phosphorus concentrations

Agriculture is a major source of nitrogen (N) and phosphorus (P) in freshwater ecosystems, and different management strategies exist to reduce farmland nutrient losses and thus mitigate freshwater eutrophication. The importance of agricultural sources of N and P as drivers of water quality is known to vary spatially, but quantification of the relative importance of the nutrient sources shaping this variability remains challenging, especially with reference to inputs from waste water treatment works. Addressing this knowledge gap is key for targeting management strategies to where they are likely to have the greatest effect. To advance our understanding in this area, this study assesses the impact of population density as a driver of the relative importance of agricultural land use for predicting mean Total Oxidised Nitrogen (TON) and Reactive Phosphorus (RP) concentrations in rivers in England, using two different data-driven, statistical approaches: a generalised linear model and random forest. Our results show that agricultural N and P sources dominate in catchments with low population density, where stream water concentrations are lower and waste water treatment works are numerous, but smaller in terms of the population equivalent served. Agricultural N and P sources are not important predictors of N and P in catchments with high population density, where contributions from waste water treatment works dominate. These results require cautious interpretation, as model validation outcomes show that high TON and RP concentrations are consistently underpredicted. Altogether, our results suggest that the relative contribution of agricultural sources may be overestimated in densely populated catchments, relative to point sources from waste water treatment works, and that management strategies to reduce the contribution of agriculture to N and P in rivers may be better targeted towards catchments with lower population density, as this is where agricultural land use is the primary source of N and P.

Identifying and testing adaptive management options to increase river catchment system resilience using a Bayesian Network model

AbstractThe cumulative impacts of future climatic and socioeconomic change threaten the ability of freshwater catchments to provide essential ecosystem services. Stakeholders who manage freshwaters require decision-support tools that increase their understanding of catchment system resilience and support the appraisal of adaptive management options to inform decision-making. Our research aims to test the ability of a Bayesian Network model to identify adaptive management scenarios and test their effectiveness across future pathways to 2050. Using the predominantly arable river Eden catchment (320 km2) in eastern Scotland as a case study, we invited stakeholders from multiple sectors to participate in a series of workshops aimed at addressing water quality issues and achieving good ecological status in the catchment both now and in the future. Our participatory methods helped stakeholders overcome multiple layers of complexity and uncertainty associated with future-focused water management. Outputs of a Bayesian Network model simulated both current and future catchment resilience to inform the identification of six management scenarios. The effectiveness of each management scenario was tested using the Bayesian Network model. Two adaptive management scenarios increased catchment resilience and helped achieve good ecological status; a ‘Best Available Technology’ scenario, including aerobic granular sludge treatment, and a management scenario focused on ‘Resource Centre’, including phosphorus recovery from wastewater treatment works and constructed lagoons for crop irrigation. Stakeholders were interested in a 'Nature Based' management scenario including options such as wetland wastewater treatment methods and rural sustainable drainage systems, which improved water quality in the catchment, but had lower certainty in achieving desired outcome. Findings led to a recognition that innovative and collaborative action was required to improve current and future freshwater conditions.

Septic tanks as a pathway for emerging contaminants to the aquatic environment–Need for alternative rural wastewater treatment?

Septic tanks (STs) as a decentralised approach to community wastewater treatment were investigated as a pathway for emerging contaminants (ECs) entering the aquatic environment. A broad range of ECs were examined in five community STs (population equivalents 217–475) and receiving rivers in Scotland over 12 months. All 68 studied ECs were detected at least once in ST influent or effluent at a broad concentration range from ng L−1 – μg L−1 which can surpass freshwater predicted no-effect concentrations. Pharmaceuticals with acute use, such as antibiotics and antifungals, had high monthly variability and concentrations can exceed those previously found in centralised wastewater treatment works. Differences between the STs demonstrate the impact of localised prescription and population behaviour on EC concentrations. The similarities in concentrations between influent and effluent, suggest limited or no removal of ECs in STs. Hence, dilution of the discharges is required to mitigate environmental risk. Although the contribution of ECs sorbed to suspended solids to the total EC concentration was generally small (<10%), higher contributions (>30%) were observed for fluoroquinolone antibiotics (ofloxacin and ciprofloxacin), antidepressants (fluoxetine), and antifungals (clotrimazole). A wide range of ECs were also detected in rivers upstream and downstream of the ST discharge points, and concentrations increased by up to 95% downstream. In general, risk quotients (RQs) in the rivers were low, indicating small risk for the environment. However, higher RQs (>1) were found for ibuprofen, diclofenac and ciprofloxacin in a few samples. Therefore, reducing their concentration by improving ST performance or through sustainable medicines use may be needed at low dilution locations to mitigate any risk.

Metagenomics analysis of sewage for surveillance of antimicrobial resistance in South Africa.

Our 24-month study used metagenomics to investigate antimicrobial resistance (AMR) abundance in raw sewage from wastewater treatment works (WWTWs) in two municipalities in Gauteng Province, South Africa. At the AMR class level, data showed similar trends at all WWTWs, showing that aminoglycoside, beta-lactam, sulfonamide and tetracycline resistance was most abundant. AMR abundance differences were shown between municipalities, where Tshwane Metropolitan Municipality (TMM) WWTWs showed overall higher abundance of AMR compared to Ekurhuleni Metropolitan Municipality (EMM) WWTWs. Also, within each municipality, there were differing trends in AMR abundance. Notably, within TMM, certain AMR classes (macrolides and macrolides_streptogramin B) were in higher abundance at a WWTW serving an urban high-income area, while other AMR classes (aminoglycosides) were in higher abundance at a WWTW serving a semi-urban low income area. At the AMR gene level, all WWTWs samples showed the most abundance for the sul1 gene (encoding sulfonamide resistance). Following this, the next 14 most abundant genes encoded resistance to sulfonamides, aminoglycosides, macrolides, tetracyclines and beta-lactams. Notably, within TMM, some macrolide-encoding resistance genes (mefC, msrE, mphG and mphE) were in highest abundance at a WWTW serving an urban high-income area; while sul1, sul2 and tetC genes were in highest abundance at a WWTW serving a semi-urban low income area. Differential abundance analysis of AMR genes at WWTWs, following stratification of data by season, showed some notable variance in six AMR genes, of which blaKPC-2 and blaKPC-34 genes showed the highest prevalence of seasonal abundance differences when comparing data within a WWTW. The general trend was to see higher abundances of AMR genes in colder seasons, when comparing seasonal data within a WWTW. Our study investigated wastewater samples in only one province of South Africa, from WWTWs located within close proximity to one another. We would require a more widespread investigation at WWTWs distributed across all regions/provinces of South Africa, in order to describe a more comprehensive profile of AMR abundance across the country.

Dissemination and persistence of antimicrobial resistance (AMR) along the wastewater-river continuum

Antimicrobial resistance (AMR) is a global health hazard. Although clinical and agricultural environments are well-established contributors to the evolution and dissemination of AMR, research on wastewater treatment works (WwTWs) has highlighted their potential role as disseminators of AMR in freshwater environments. Using metagenomic sequencing and analysis, we investigated the changes in resistomes and associated mobile genetic elements within untreated wastewater influents and treated effluents of five WwTWs, and sediments collected from corresponding river environments in Oxfordshire, UK, across three seasonal periods within a year. Our analysis demonstrated a high diversity and abundance of antimicrobial resistance genes (ARGs) in untreated wastewater influents, reflecting the varied anthropogenic and environmental origins of wastewater. WwTWs effectively reduced AMR in the final effluent, with an average 87 % reduction in normalised ARG abundance and an average 63 % reduction in richness. However, wastewater effluents significantly impacted the antimicrobial resistome of the receiving rivers, with an average 543 % increase in ARG abundance and a 164 % increase in richness from upstream sediments to downstream sediments. The normalised abundance of the human gut-associated bacteriophage crAssphage was highly associated with both ARG abundance and richness. We observed seasonal variation in the resistome of raw influent which was not found in the effluent-receiving sediments. We illustrate the potential of WwTWs as focal points for disseminating ARGs and resistance-selecting chemicals, contributing to the elevation of environmental AMR. Our study emphasises the need for a comprehensive understanding of the anthropogenic impacts on AMR evolution and dissemination in wastewater and river environments, informing efforts to mitigate this growing public health crisis.

Drivers of seasonal water hyacinth dynamics in permanently eutrophic estuarine waters

Anthropogenic nutrient enrichment is one of the key global change pressures threatening the health of estuaries. This is evident at the persistently eutrophic Swartkops Estuary located along the warm temperate coast of South Africa. Augmented nutrient-rich baseflows (e.g., stormwater runoff, wastewater treatment work discharges) have resulted in the persistent growth of invasive alien aquatic plants (IAAPs), particularly water hyacinth (Pontederia crassipes), in the upper estuarine reaches. As such, the objective of this study was to investigate the temporal population dynamics of water hyacinth in the Swartkops Estuary to inform management options. Methods included five-weekly sampling campaigns in winter, spring, and summer, interspersed with monthly sampling over a year-long period. Physico-chemical variables and river inflow were measured in situ, while samples were collected for inorganic nutrients, phytoplankton biomass, and IAAP measurements (cover, biomass, and tissue nutrients). Model results indicated that increased water temperature and inorganic nitrogen (ammonium and NOx) levels promoted increased coverage of water hyacinth, while seasonal analysis highlighted reduced (p < 0.05) dissolved oxygen levels during the peak summer IAAP accumulation period. Notably, model results indicated declining IAAP tissue TN and TP concentrations with increasing water temperature, yet overall TN and TP storage was highest in summer due to the extensive water hyacinth cover observed during this period. Overall, the proportionally low and transient nature of nutrient storage by water hyacinth populations, together with the detrimental consequences they facilitate, highlights the need to integrate short-term control measures with catchment-scale management interventions geared towards mitigating the causative drivers.

Clarity tubes as effective citizen science tools for monitoring wastewater treatment works and rivers.

Improved freshwater resource management requires the implementation of widespread, effective, and timely water quality monitoring. Conventional monitoring methods are often inhibited by financial, infrastructural, and human capacity limitations, especially in developing regions. This study aimed to validate the citizen-scientist-operated transparency or clarity tube (hereafter "clarity tube") for measuring water clarity as a proxy for total suspended solids (TSS) concentration, a critical quality metric in river systems and wastewater treatment works (WWTW) effluent in Southern Africa. Clarity tubes provided a relatively accurate and precise proxy for TSS in riverine lotic systems and WWTW effluent, revealing significant inverse log-linear relationships between clarity and TSS with r2 = 0.715 and 0.503, respectively. We demonstrate that clarity-derived estimates of TSS concentration (TSScde) can be used to estimate WWTW compliance with WWTW effluent TSS concentration regulations. The measurements can then be used to engage with WWTW management, potentially affecting WWTW performance. Overall, these findings demonstrate the usefulness of clarity tubes as low-cost, accessible, and easy-to-use citizen science tools for high spatial and temporal resolution water quality monitoring, not only in rivers in Southern Africa but also in WWTW effluent for estimating compliance, with strong global relevance to the sustainable development goals (SDGs). Integr Environ Assess Manag 2024;20:1463-1472. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Magnetization and ZIF-67 modification of Aspergillus flavus biomass for tetracycline removal from aqueous solutions: A stable and efficient composite

In the present work, the biomass of Aspergillus flavus (AF) was modified using magnetic nanoparticles MnFe2O4 and metal-organic framework of ZIF-67, and its ability to remove tetracycline antibiotic (TCH) was investigated. With the help of physicochemical tests, AF biomass modification with ZIF-67 and MnFe2O4 magnetic nanoparticles was confirmed. Based on the BET value, AF-MnFe2O4-ZIF-67 (139.83 m2/g) has a higher surface value than AF (0.786 m2/g) and AF/MnFe2O4 (17.504 m2/g). Also, the magnetic saturation value revealed that the modified biomass can be isolated from the treated solution using a simple magnetic field. Maximum TCH elimination (99.04%) using AF-MnFe2O4-ZIF-67 was obtained at pH 7, adsorber mass of 1 g/L, adsorption time of 40 min, and TCH content of 10 mg/L. The thermodynamic study indicated that the TCH abatement using the desired composite is spontaneous and exothermic. The experimental results showed that the adsorption process is compatible with the pseudo-second-order kinetic and Freundlich model. The maximum adsorption capacity for AF, AF-MnFe2O4, and AF-MnFe2O4-ZIF-67 was quantified to be 9.75 mg/g, 25.59 mg/g, and 43.87 mg/g, respectively. The reusability of the desired adsorbers was examined in up to 8 steps. The outcomes showed that the adsorbers can be used several times in TCH elimination. The provided composite can remove TCH from hospital wastewater, so it can be suggested for use in water and wastewater treatment works.

Quantification and Potential Viability of Human Noroviruses in Final Effluent from Wastewater Treatment Works in Pretoria, South Africa

Growing global concerns over water scarcity, worsened by climate change, drive wastewater reclamation efforts. Inadequately treated wastewater presents significant public health risks. Previous studies in South Africa (SA) have reported high norovirus levels in final effluent and sewage-polluted surface water, indicating pathogen removal inefficiency. However, the viability of these virions was not explored. This study assessed human norovirus viability in final effluent from wastewater treatment works (WWTWs) in Pretoria, SA. Between June 2018 and August 2020, 200 samples were collected from two WWTWs, including raw sewage and final effluent. Norovirus concentrations were determined using in-house RNA standards. Viability of noroviruses in final effluent was assessed using viability RT-qPCR (vPCR) with PMAxx™-Triton X-100. There was no significant difference in GI concentrations between raw sewage (p = 0.5663) and final effluent (p = 0.4035) samples at WWTW1 and WWTW2. WWTW1 had significantly higher GII concentrations in raw sewage (p < 0.001) compared to WWTW2. No clear seasonal pattern was observed in norovirus concentrations. At WWTW1, 50% (7/14) of GI- and 64.9% (24/37) of GII-positive final effluent samples had no quantifiable RNA after vPCR. At WWTW2, the majority (92.6%, 25/27) of GII-positive final effluent samples showed a 100% RNA reduction post vPCR. PMAxx™-Triton X-100 vPCR provides a more accurate reflection of discharge of potentially viable noroviruses in the environment than standard RT-qPCR. Despite significant reductions in potentially viable noroviruses after wastewater treatment, the levels of potentially viable viruses in final effluent are still of concern due to the high initial load and low infectious dose of noroviruses.

Carbon footprint assessment of water and wastewater treatment works in Scottish islands

Quantifying the global warming potential of existing water infrastructure is an important step in realising the water industry's commitment to net-zero carbon. Whilst there has been an improved understanding of the global warming potential of centralized urban water infrastructure, rigorous analyses of smaller-scale rural systems are rare. This work adopts a life cycle assessment to ascertain the global warming potential of existing drinking water treatment works and wastewater treatment works associated with five Scottish islands: Arran, Iona, Jura, Barra, and Vatersay. The water systems, from source to sink, along with the use of chemicals, transportation, energy, and the reuse of waste products from water infrastructure are considered. The global warming potentials of the island's drinking water treatment works ranged from 0.18 to 0.79 kgCO2-eq/m3 of drinking water, while that for wastewater treatment works were 0.51 to 1.14 kgCO2-eq/m3 of wastewater. The global warming potential for water services on the islands can be as much as 7-times of that water services across Scotland as previously reported. Major global warming potential contributor in drinking water treatment works was the electricity consumed by the membrane bioreactors. The modelled direct emission of methane from sludge in septic tanks and for land reclamation made the largest contribution to global warming potential. It was also highly sensitive to model parameters, which highlights the need for a comprehensive exploration of process emissions from septic tanks and sludge handling. This analysis of existing rural water infrastructure is a baseline against which potential alternative low-carbon technology configurations can be compared.

Campus source to sink wastewater surveillance of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)

Wastewater-based surveillance (WBS) offers an aggregate, and cost-effective approach for tracking infectious disease outbreak prevalence within communities, that provides data on community health complementary to individual clinical testing. This study reports on a 16-month WBS initiative on a university campus in England, UK, assessing the presence of SARS-CoV-2 in sewers from large buildings, downstream sewer locations, raw wastewater, partially treated and treated effluents. Key findings include the detection of the Alpha (B.1.1.7) variant in wastewater, with 70 % of confirmed campus cases correlating with positive wastewater samples. Notably, ammonium nitrogen (NH4-N) levels showed a positive correlation (ρ = 0.543, p < 0.01) with virus levels at the large building scale, a relationship not observed at the sewer or wastewater treatment works (WWTW) levels due to dilution. The WWTW was compliant to wastewater standards, but the secondary treatment processes were not efficient for virus removal as SARS-CoV-2 was consistently detected in treated discharges. Tools developed through WBS can also be used to enhance traditional environmental monitoring of aquatic systems. This study provides a detailed source-to-sink evaluation, emphasizing the critical need for the widespread application and improvement of WBS. It showcases WBS utility and reinforces the ongoing challenges posed by viruses to receiving water quality.

Water and Sediment Chemistry as Drivers of Macroinvertebrates and Fish Assemblages in Littoral Zones of Subtropical Reservoirs

Reservoirs are human-made ecosystems with diverse purposes that benefit humans both directly and indirectly. They however cause changes in geomorphological processes such as sediment cycling and influence the composition and structure of aquatic biota. This study aimed to identify water and sediment quality parameters as drivers of macroinvertebrates and fish communities during the cool-dry and hot-wet seasons in the littoral zones of three subtropical reservoirs (Albasini, Thathe and Nandoni). Macroinvertebrates and fish were collected from three sites (n = 3 from each site) in each reservoir. A total of 501 and 359 macroinvertebrates and fish individuals were collected throughout the sampling period, respectively. The present study employed a two-way ANOVA in conjunction with redundancy analysis (RDA) to assess the relationships that exist between water and sediment variables, macroinvertebrates diversity and species abundances across seasons. Based on the two-way ANOVA model, significant differences were observed across reservoirs for evenness, Simpson’s diversity, and total abundance, while seasonal differences were observed for most metrics, with exception for evenness. The RDA results identified four water variables (i.e., water temperature, oxidation–reduction potential, pH and conductivity) and one sediment metal (Mg) as the most important parameters in driving the fish community structure. Field observations and metal results attest that the Nandoni reservoir shows high concentrations of metals in sediments as compared to other reservoirs, suggesting that anthropogenic activities such as car washing, brick making, recreation, fishing, wastewater treatment work and landfill site may be the major contributor of metals to the Nandoni reservoir, which accumulate in the littoral zones. Findings of this study highlight the need to analyze reservoir ecological conditions at several scales. The study of macroinvertebrates and fish, water, and sediment chemistry in the littoral zone laid the groundwork for proposing measures for conserving aquatic ecosystems.

Identification and quantification of microplastics in wastewater treatment plants by spectroscopic and microscopic techniques in Johannesburg East, South Africa

Abstract The occurrence of microplastics in water, their chemistry, physical characteristics, and the efficiency of public wastewater treatment work (WWTW) processes in the removal of microplastics are investigated. Samples were collected from the period 2021 December to 2022 September from two WWTWs in Johannesburg East using 24-h autosamplers. The microplastics were imaged using polarised optical microscopy (POM) and the images were processed using image J 1.53 K to determine the particle counts. The total concentration of microplastics at WWTW A was 3,098 MP/L while WWTW B had 3,561 MP/L. The microplastics identified across the seasons were dominated by angular, fibres, fragments, and films. Fourier transforms infrared (FTIR) spectroscopy identified the polymers such as polyethylene, acrylic, polyethylene terephthalate, and polystyrene in WWTW A and B influent while identifying the polymers such as polystyrene, polyacrylamide, polypropylene, polycarbonate, acrylonitrile butadiene styrene, poly(ethyl cyanoacrylate), carboxyl, poly(ethylene terephthalate), polyethylene, poly(methyl methacrylate), and cellulose in the final effluent. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) identified Cr, Ca, Fe, Al, Na, Mg, Zn, Cl, P, S, and silicon as additives to microplastics with high-intensity peaks of oxygen and carbon. It is recommended to monitor and regulate microplastics in discharged effluents from WWTWs to minimise environmental pollution.

High throughput qPCR unveils shared antibiotic resistance genes in tropical wastewater and river water

The global challenge posed by rising antimicrobial resistance, and the adoption of a One Health approach, has led to the prioritisation of surveillance for antibiotic resistance genes (ARGs) in various environments. Herein lies an information gap, particularly in the context of Thailand, where there is scarce data on ARG prevalence across diverse environmental matrices and throughout different seasons. This study aimed to fill this void, analysing ARG prevalence by high-throughput qPCR in influent (n = 12) and effluent wastewater (n = 12) and river water (n = 12). The study reveals a substantial and largely uniform presence of ARGs across all water sample types (87 % similarity). Intriguingly, no ARGs were exclusive to specific water types, indicating an extensive circulation of resistance determinants across the aquatic environment. The genes intI1, tnpA, and intI3, part of the integrons and mobile genetic elements group, were detected in high relative abundance in both wastewater and river water samples, suggesting widespread pollution of rivers with wastewater. Additional high-prevalence ARGs across all water types included qepA, aadA2, merA, sul1, qacF/H, sul2, aadB, and ereA. More alarmingly, several ARGs (e.g., blaVIM, intI3, mcr-1, mexB, qepA, vanA, and vanB) showed higher relative abundance in effluent and river water than in influents, which suggests malfunctioning or inadequate wastewater treatment works and implicates this as a possible mechanism for environmental contamination. Nine genes (i.e., blaCTX-M, blaVIM, emrD, ermX, intI1, mphA, qepA, vanA, and vanB) were recovered in greater relative abundance during the dry season in river water samples as compared to the wet season, suggesting there are seasonal impacts on the efficacy of wastewater treatment practices and pollution patterns into receiving waters. This study highlights the urgency for more effective measures to reduce antibiotic resistance dissemination in water systems.

Effect of macronutrients (carbon, nitrogen, and phosphorus) on the growth of Chlamydomonas reinhardtii and nutrient recovery under different trophic conditions.

More stringent discharge standards have led to the development of an alternative nutrient recovery system from wastewater. Microalgae cultivation in wastewater treatment works has presented considerable promise from the perspective of sustainable resource management. Growth kinetics models are useful tools to optimize nutrient recovery from wastewater by algal uptake. Therefore, this research aims to identify the growth kinetics of Chlamydomonas reinhardtii under both heterotrophic and phototrophic conditions with different nutrient concentrations that typify those found in wastewater treatment works. In addition, the effects of macronutrients (C, N, and P) on heterotrophic and phototrophic microalgae growth and nutrient recovery were studied. Greater specific growth rates were achieved under heterotrophic conditions than in phototrophic cultivation. The maximum specific growth rates and nutrient recovery efficiencies were achieved at 5 mg P L-1 under both heterotrophic and phototrophic growth conditions. Nitrate was the preferred form of nitrogen source under heterotrophic conditions, while nitrogen sources did not present any significant influences in the phototrophic cultivation. Specific growth rates reported for both heterotrophic and phototrophic microalgae at lower carbon concentrations (3.10 d-1 and 0.46 d-1, sequentially) were higher than those at higher carbon concentrations (1.95 d-1 and 0.22 d-1, respectively). C. reinhardtii presented an extreme capacity to adapt and grow at all experimental conditions tested in heterotrophic and phototrophic cultivations.

Export Coefficient Modelling of Nutrient Neutrality to Protect Aquatic Habitats in the River Wensum Catchment, UK

The pressure of nutrient pollution derived from wastewater treatment works and agricultural runoff is a reason for the decline in the ecological health of aquatic habitats. Projected residential development in catchments creates further nutrient loading that can be offset by nutrient management solutions that maintain ‘nutrient neutrality’ either onsite or elsewhere within the same catchment. This study developed an export coefficient model in conjunction with detailed farm business data to explore a nature-based solution to nutrient neutrality involving seven scenarios of crop conversion to mixed woodland or grazing grass in an area of intensive arable cultivation in the groundwater-fed Blackwater sub-catchment of the River Wensum, UK. When compared with the monitored riverine export of nutrients, the calculated nitrogen (N) and phosphorus (P) inputs under current land use showed that subsurface denitrification is removing 48–78% of the leached N and that P is accumulating in the field soils. The addition of 235 residential homes planned for 2018–2038 in the Blackwater will generate an additional nutrient load of 190 kg N a−1 and 4.9 kg P a−1. In six of the seven scenarios, the modelled fractions of crop conversion (0.02–0.21) resulted in the required reduction in P loading and more than sufficient reduction in N loading (196–1874 kg a−1 for mixed woodland and 287–2103 kg a−1 for grazing grass), with the additional reduction in N load above the requirement for nutrient neutrality potentially contributing to further improvement in water quality. The cost of land conversion is modelled in terms of crop gross margins and nutrient credits generated in the form of 0.1 kg units of N or P. For the range of scenarios considered, the annual cost per credit ranged from GBP 0.78–11.50 for N for mixed woodland (GBP 0.74–7.85 for N for grazing grass) and from GBP 160–782 for P for both scenarios. It is concluded that crop conversion is a viable option to achieve nutrient neutrality in arable catchments in eastern England when considered together with other nutrient management solutions.

Endocrine Disruption Is Reduced but Still Widespread in Wild Roach (Rutilus rutilus) Living in English Rivers.

Endocrine disruption of wild fish, primarily resulting in the feminization of males, has been reported in English river sites for several decades. Estrogenic activity emanating from wastewater treatment works (WwTW) has been conclusively demonstrated to be the main driver of these feminized phenotypes. Here, we revisit 10 English river sites previously surveyed in the late 1990s and early 2000s to assess how the frequency and severity of feminization now compare with the historical surveys. In the contemporary assessment, 60% of the sites revisited still showed endocrine disruption at the tissue organization level (oocytes present in otherwise male gonads; intersex) and 90% of sites had average male plasma vitellogenin concentrations (female-specific yolk protein; a sensitive biomarker of estrogen exposure) above natural baseline levels. In contrast to the historic surveys, none of the males sampled in the contemporary survey had ovarian cavities. At one of the larger WwTW, improvements to treatment technology may have driven a significant reduction in intersex induction, whereas at several of the smaller WwTW sites, the frequencies of feminization did not differ from those observed in the late 1990s. In conclusion, we show that although the severity of feminization is now reduced at many of the revisited sites, endocrine-disrupting chemicals are still impacting wild fish living downstream of WwTW in England.

Nowhere to go! Microplastic abundances in freshwater fishes living near wastewater plants

Microplastic presence in aquatic environments is a major problem globally. This study quantified microplastic abundances in fish species across two systems in South Africa around wastewater treatment works. Fish (n = 163) were examined for microplastic in gills and gastrointestinal tracts. Microplastic levels were generally low during the cool–dry season (mean 11.0 – 34.0 particles per fish taxon), and high during the hot–wet season (mean 10.0 – 119.0 particles per fish taxon). The microplastic concentrations per fish were similar between these systems, with downstream of wastewater treatment plants having high microplastic abundances. Although benthopelagic feeders were dominant, pelagic feeders had high microplastic abundances (range 20–119 particles), followed by benthopelagic (range 10–110 particles) and demersal (22 particles) feeders. Multiple regression analysis revealed a significant positive relationship between fish standard length and total microplastic levels, which suggests fish consume more microplastics due to increased food demand as a result of growth.