Secondary Wastewater Treatment Plant Research Articles

Cultivation of Chlorella vulgaris in wastewater: biodiesel potential and wastewater remediation.

The present investigation has evaluated the use of effluents from a secondary municipal wastewater treatment plant for biomass production and potential of the biomass for biodiesel production. Cultivations of Chlorella vulgaris using wastewater, wastewater with supplementation, and WC medium were carried out. Effect of wastewater collected in different months on biomass productivity (BP) and lipid composition was studied. Methods based on NMR and GC-MS techniques were applied for determining the composition of the lipids and their fatty acid profile including poly unsaturated fatty acids (PUFAs). Lipids extracted are comprised of both neutral (tri acyl glycerides, TAG; free fatty acids, FFA) and polar (glyco glycero/phospho) lipids. The TAG content of the extracted lipids was determined in the range of 22.5-41.3% w/w. The NMR and GC-MS compositional results of microalgal lipids of biomasses cultivated in wastewater without nutrient supplementation, collected in different months, showed potential for biodiesel production. The fatty acid profiles of neutral and polar lipids, which are mainly comprised of saturated and unsaturated long alkyl chain (C16-C22) fatty acids, are potential sources for the biodiesel and food industry. The concentration of nitrates (45-78mg L-1) in wastewater without supplementation, collected in different months, was found to be optimum to enable cultivation of biomasses with reasonably good BP of 21.5-28.1mg L-1day-1. Similar results have been obtained in the present work as well as reported in the literature in the case of WC medium (nitrate, 69mg L-1) with BP of 25.5-28.2mg L-1day-1, thus highlighted the significance of the presented work.

Integrated toxicity of secondary, tertiary, wetland effluents on human stem cells triggered by ERα and PPARγ agonists

Residual pollutants in discharged and reused water pose both direct and indirect human exposure. However, health effects caused by whole effluent remain largely unknown due to the lack of human relevant model for toxicity test. Effluents from four secondary wastewater treatment plants (SWTPs), a tertiary wastewater treatment plant (TWTP) and a constructed wetland (CW) were evaluated for the integrated toxicity of the organic extractions. Multiple-endpoint human mesenchymal stem cells (MSCs) assay was used as an in vitro model relevant to human health. The effluents caused cytotoxicity, oxidative stress and genotoxicity in MSCs. The osteogenic and neurogenic differentiation were inhibited and the adipogenic differentiation were stimulated by some of the effluent extractions. The SWTP, TWTP and CW treatments reduced integrated biomarker response (IBR) by 26.3 %, 17.5 % and 33.3 % respectively, where the IBR values of final CW (8.3) and TWTP (8.2) effluents were relatively lower than SWTPs (9.1). Among multiple biomarkers, the inhibition of osteogenesis was the least reduced by wastewater treatment. Besides, ozone disinfection in tertiary treatment increased cytotoxicity and differentiation effects suggesting the generation of toxic products. The mRNA expressions of estrogen receptor alpha (ERα) and peroxisome proliferator-activated receptor gamma (PPARγ) were significantly upregulated by effluents. The inhibitory effects of effluents on neural differentiation were mitigated after antagonizing ERα and PPARγ in the cells. It is suggested that ERα and PPARγ agonists in effluents were largely accountable for the impairment of stem cell differentiation. Besides, the concentrations of n-C29H60, o-cresol, fluorene and phenanthrene in the effluents were significantly correlated with the intergrated stem cell toxicity. The present study provided toxicological evidence for the relation between water contamination and human health, with an insight into the key toxicity drivers. The necessity for deep water treatment and the potential means were suggested for improving water quality.

Lessons in Legacies: Treatment Plant Expansion Under the Clean Water Act

The US Clean Water Act of 1972 required cities to build secondary wastewater treatment plant capacity to improve the environment and protect public health. The expansion of the Southeast Pollution Control Plant in San Francisco’s Bayview-Hunters Point, a historically Black neighborhood, illustrates how planners employed rational-comprehensive approaches as the bases for their decision-making, worsening the community’s environmental burdens. This occurred even as the community used recently adopted environmental policy frameworks to mitigate the plant’s consequences. The Clean Water Act should be evaluated on clean water objectives and in terms of how communities were harmed to achieve these environmental goals.

Characteristics and removal efficiency of microplastics at secondary wastewater treatment plant in Lithuania.

Wastewater treatment plants (WWTPs) are the most significant barrier between anthropogenic microplastics and environmental ecosystems. The distribution and characteristics of microplastics in WWTPs remain uncertain and incompletely understood, particularly in northeastern Europe (Baltic States), where there is a lack of data on microplastic pollution and distribution. This study presents the removal efficiency and variation in characteristics of microplastics in different stages of the secondary WWTP during a 3-month sampling campaign in Lithuania. The abundance, size, shape, color, and chemical composition of microplastics in the wastewater at different treatment stages were thoroughly examined, in a size range from 20 to 1000 μm. On average, 2962 ± 25 particles/L of microplastic enter the studied WWTP. The obtained microplastic removal efficiency was 55.4% ± 3.9%, highlighting the necessity to enhance wastewater treatment strategies focusing on microplastic removal. Fragment-type microplastics smaller than 100 μm were removed from wastewater samples with the highest removal efficiency. Furthermore, our study includes recommendations to improve microplastic removal efficiency and contribute to mitigating microplastic pollution. PRACTITIONER POINTS: A large number of MPs in the size range of 20-1000 μm enter Lithuanian WWTP. Small-sized MPs within a range of 20-50 μm and 50-100 μm were removed with the highest efficiency of 54.07 ± 1.68% and 56.4 ± 2.43%, respectively. The shape and size of MPs have a major impact on the efficiency of their removal. Future research should prioritize the development of economical and energy-efficient systems, specifically designed for the removal of MPs in WWTPs.

First evidence of environmental bioaccumulation of pharmaceuticals on adult native anurans (Rhinella arenarum) from Argentina

The presence of pharmaceutically active compounds (PhACs) in surface water is well known, whereas their natural occurrence in biota is much less explored. The aim of this work was to evaluate the bioaccumulation of PhACs in adult toads of the neotropical species Rhinella arenarum. Three sites were selected in Buenos Aires (Argentina): a reference site (Site 1), a site with direct discharge from a secondary wastewater treatment plant (WWTP) (Site 2) and a site 300 m downstream of the WWTP discharge (Site 3). Surface water samples, as well as muscle, liver and fat bodies of toads were collected, extracted and analyzed by LC-MS/MS. Highly significant differences in total PhACs concentration in surface water (p < 0.005) were detected between Site 2 and the other sites. These concentrations ranged from 0.37 to 52.46 ng/L at Site 1, 0.71–6950.37 ng/L at Site 2, and 0.12–75.45 ng/L at Site 3. In general, bioaccumulation of PhACs in toad tissues was similar between sites and tissues of each site. The highest concentrations were detected in the muscle of toads from Site 3 (1.06–87.24 ng/g dw), followed by liver (1.77–38.10 ng/g dw) and fat bodies (0.68–20.59 ng/g dw) from Site 1. Ibuprofen (6950 ng/L), acetaminophen (3277 ng/L) and valsartan (2504 ng/L) were the compounds with the highest concentrations in surface water from Site 2, whereas acetaminophen (87.2 ng/g dw, muscle from Site 3), desloratadine (38.1 ng/g dw, liver from Site 1), and phenazone (25.9 ng/g dw, liver from Site 1) were the ones that showed the highest concentrations in biota. This is the first time a field study has examined the environmental bioaccumulation of PhACs in anurans, demonstrating their potential for monitoring the status of natural ecosystems.

Microplastic emission trends in Turkish primary and secondary municipal wastewater treatment plant effluents discharged into the Sea of Marmara and Black Sea

Wastewater Treatment Plants (WWTPs) are recognized as one of the primary sources of microplastics, a class of contaminants that has lately gained attention. The quantity of MP that WWTPs release into the environment depends on several factors, including the treatment type, season, and population serviced. MP abundance and characterization were explored in 15 WWTP effluent waters, 9 discharged to the Black Sea from Türkiye and 6 to the Marmara Sea, with varying population densities and treatment methods. The mean MP abundance in primary treatment WWTPs (76.25 ± 49.20 MP L−1) was found to be substantially greater than that in secondary treatment WWTPs (20.57 ± 21.56 MP L−1) (p<0.05). MPs in WWTP effluent waters showed significant seasonal and spatial differences (Two Way ANOVA, Tukey, p<0.05). However, no positive correlation was detected between the population serviced and MP abundance in effluent waters. While the fiber was the dominant shape (49.5%) among MPs in effluent waters, ≈80% of the length was <1000 μm. MPs are classified into polymer types as follows: polyethylene terephthalate (34.9%) > polypropylene (32.4%) > polyethylene (19.9%) > polyamide (11%) > polystyrene (1.2%) > polyvinyl chloride (0.6%). With effluent waters from the WWTPs tested, we calculated that 1.24x1010 daily MPs are discharged into the Black Sea while 4.95x1010 MPs are into the Marmara Sea, for a combined annual discharge of 2.26x1013 MPs highlighting that WWTPs are key contributors of MP in Turkish coastal waters.

Water Availability and Status of Wastewater Treatment and Agriculture Reuse in China: A Review

Due to climate change, 2/3 of the world’s population will face water shortage problems by 2025, while a 50% increase in food production is required in 2050 to feed nine billion people. In addition, the intensified anthropogenic activities have significantly increased water resource pollution. In this condition, wastewater reuse for crop irrigation to reduce water scarcity is currently becoming global, while it often causes soil pollution and heavy metal accumulation in agricultural areas. This situation has increased public concern over its environmental impact. Thus, an integrated framework was conducted to discuss the status of water availability in China, wastewater treatment and reuse in irrigation systems, and the potential health risks. Avenues for new research toward sustainable agriculture were discussed. We emphasize that wastewater reuse reduces the freshwater deficit and increases food productivity. However, adequate treatment should be applied before use to reduce its adverse impacts on human health risks and environmental pollution. Facilities and policies should support more accessible access to reclaimed water used in industries and urban facilities from secondary municipal wastewater treatment plants. This could be a long-term solution to eradicate water scarcity and inefficient water resources in agricultural systems.

Integrated genotoxicity of secondary and tertiary treatment effluents in North China

Genotoxic effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to reduce effluent genotoxicity was not well known. Genotoxic effects of effluents from four secondary wastewater treatment plants (SWTPs) and a tertiary wastewater treatment plant (TTP) in north China on Chinese rare minnows (Gobiocypris rarus) were evaluated and the toxicity reduction efficiency of various treatment techniques was compared. SWTPs and TTP final effluents disturbed the antioxidant system and lipid peroxidation, with malondialdehyde (MDA) contents in the fish livers and gills increasing to 1.4–2.4 folds and 1.6–3.1 folds of control, respectively. Significant increases in erythrocytes micronucleus (MN) frequency were induced by effluent, and liver DNA damage caused by final SWTPs effluent was 29–54 % lower than TTP effluent. Further, DNA repair gene atm and growth arrest gene gadd45a were remarkably upregulated by SWTP and TTP final effluents to 1.8–12 folds and 4.1–15 folds, respectively, being consistent with the chromosomal aberration and DNA damage in liver tissue. Integrated biomarker response (IBR) of the tertiary effluent was 49 %–69 % lower than the secondary effluents. However, the final ozone disinfection at TTP caused an increase in the DNA damage, suggesting the generation of genotoxic by-products. UV disinfection at secondary treatment removed part of genotoxicity, with a reduction in IBR of 0 %–47 %. The total semi-volatile organic compounds (SVOCs) detected in the final effluent contained 5 %–56 % potential genotoxic substances, removal of which was 9 %–51 % lower than non-genotoxic compounds. Microfiltration and reverse osmosis process exhibited good performance in removing both the integrated genotoxicity and the potential genotoxic SVOCs. Our finding shows that TTP is superior than SWTP for wastewater treatment due to higher genotoxicity removal, but ozone disinfection needs improvement by optimizing performance parameters or adding post-treatment processes, to achieve better protection for aquatic organisms against genotoxic contaminants.

Thiabendazole degradation by photo-NaOCl/Fe and photo-Fenton like processes, using copper slag as an iron catalyst, in spiked synthetic and real secondary wastewater treatment plant effluents.

Thiabendazole degradation (TBZD) in diferent types of water matrices was assessed by applying two Advanced Oxidation Processes, both using simulated solar light (SSL), copper slag (CS) as an iron based catalyst, and separately H2O2 or NaOCl as oxidants. First, optimum conditions for TBZD were evaluated in distilled water, TBZD = 90% at 60 min for CS-H2O2-SSL, and 92% of TBZD in a twelfth of the time by the system CS-NaOCl-SSL; minimum TBZ depletion variations were observed between the first and the fifth reuse test: 88 ± 2% for CS-H2O2-SSL (60 min) and 90 ± 1% for CS-NaOCl-SSL (5 min). Those conditions were tested using a synthetic (SE) and a real secondary effluent (RE) from a wastewater treatment plant. The CS-H2O2-SSL system achieved TBZD of 88 and 77% after 90 min for SE and RE, with kinetic constants of 0.024 and 0.016 min-1, respectively, whereas photo-NaOCl/Fe showed values of 0.365 and 0.385 min-1 for SE and RE, achieving a 94% TBZD removal in both types of water at 10 min. That might be related to the formation of Cl· and HO• during the photo-NaOCl/Fe process, highlighting that the CS-NaOCl-SSL is an attractive option that has great possibilities for scaling up by a better knowledge in real aqueous matrices.

Spatiotemporal characteristics of microplastics in a university wastewater treatment plant: Influence of sudden on-campus population swings

We studied the occurrence and characteristics (sizes, shapes, and polymer compositions) of microplastics (MPs) in a secondary wastewater treatment plant (WWTP) at the University of Mississippi both spatially and temporally. Putative MPs were isolated by sieving, matrix digestion, and density separation, and quantified using stereomicroscopy, with a subset of samples analyzed by Focal Plane Array (FPA) µ-FTIR imaging. In the influent, the highest MP concentration (particles/L ± 1 SD, n = 3) occurred after a football game on campus (62.3 ± 7.6) and the lowest (19.7 ± 2.1) during the summer with little activity on campus. Over 90% of the MPs were removed in the primary treatment. Downstream, MPs were most abundant in the closed loop reactor with concentrations as high as 1962 particles/L. Concentrations in secondary clarifier and final treated effluent were both < 4 particles/L during both normal flow (∼2000 m3/d) and high-flow (>2500 m3/d) periods, and between 16 and 39 particles/L during a low-flow (<1500 m3/d) period. This difference likely stems from changes in plant operations during the low-flow period to support the activated sludge, including longer process times. MPs were mainly composed of polyester, polyethylene, acrylates, polypropylene, polyurethane, polyvinyl chloride, and polystyrene. Fibers were most abundant throughout the system, averaging 61%, followed by fragments (21%), films (13%), and beads and foams (∼5%). Overall, we show that flow rates and treatment times can profoundly influence MPs concentrations in the treated effluent, and that the optimal wastewater treatment conditions also yield the best MP removal efficiency.

Novel electro-oxidation unit for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: batch and continuous experiments

The prime objective of the current investigation is to evaluate a promising alternative method for disinfection wastewater using a novel electro-oxidation unit. The study focused on determining the best-operating conditions from a techno-economic point of view to be applied to continuous flow simulating actual disinfection modules. The treatment unit consisted of a Plexiglas container with a 3 L volume containing nine cylindrical shape electrodes (6 graphite as anode and 3 stainless steel as a cathode) connected to a variable DC power supply. Determination of the best operating parameters was investigated in batch mode on synthetic wastewater by studying the effect of contact time, current density (CD), total dissolved solids concentration (TDS), and bacterial density. Moreover, the continuous mode experiment was considered on real wastewater from an agricultural drain and the secondary wastewater treatment plant effluent before chlorination. The batch mode results revealed that the best applicable operational conditions that achieved the complete removal of E. coli were at a contact time of less than 5 min, TDS of 2000 mg/L, and CD of 4 mA/cm2. Application of these conditions on the continuous mode experiment indicated the complete removal of all bacterial indicators after 5 min in the drainage wastewater and after 3 min in the secondary treated wastewater. Physico-chemical characterization also suggested that no chlorine by-products displaying the hydroxide ion formed due to water electrolysis is the main reason for prohibiting the growth of pathogenic microbes. The electrical consumption was calculated in the continuous mode and found to be 0.5 kWh/m3 with an operational cost of about 0.06 $/m3, including the cost of adding chemicals to increase the TDS. The results proved that this novel electro-oxidation unit is a robust and affordable disinfection method for complete bacterial removal from wastewater and is more environmentally benign than other conventional disinfection methods.

Microbial communities and biosynthetic pathways for the production of sulfated polysaccharides in the activated sludge system

Sulfated polysaccharides (SP) are widely used as industrial additives and pharmaceutical intermediates. As SP can only be extracted from sea algae, making them scarce raw materials. Recently, SP have been detected and extracted from the waste activated sludge of a saline secondary wastewater treatment plant, suggesting that there are alternative primary producers and synthesis pathways of the SP within the biological activated sludge. This study aimed to identify the primary SP producers, the SP biosynthesis pathways as well as the SP production rates in different types of activated sludges cultivated anoxically and/or anaerobically, with and without the presence of sufficient sulfate. The results showed that alternating anaerobic/anoxic conditions in sludge effectively produced the SP by the ordinary heterotrophic organisms (OHOs). The synthesis pathways for the three most common bioactive SP viz. fucoidan, carrageen, and heparin, were identified and elucidated at both the substrate and enzymatic levels. The Western Blot analyses revealed key enzymes for the SP synthesis (e.g., GDP-L-fucose-synthetase, GDP-fucose-pyrophosphorylase, β-1,4-galactosyltransferase), when sulfate was sufficient (>170 mg S/L) under an alternating anaerobic/anoxic conditions. In contrast, the absence of sulfate suppressed the SP production during the initial step of the SP generation. The synthesis of the SP in the sulfate-reducing (anaerobic) sludge was suppressed by the enzymatic inhibition, when sulfide exceeded 160 mg S/L, due to the competition for energy between the SP synthesis and sulfide detoxification. However, in the case of the sulfide-oxidizing sludge both the organic carbon and metabolism energy deficiencies inhibited the SP production. The findings of this study expand the understandings of the SP synthesis in the activated sludge under different operating conditions, including different sulfate levels.

Integrated estrogenic effects and semi-volatile organic pollutants profile in secondary and tertiary wastewater treatment effluents in North China

Endocrine-disrupting effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to remove estrogenic activity in effluents and the association with organic micropollutants was not well known. We evaluated the estrogenic activity using a well-characterized in vivo bioassay featuring the Chinese rare minnows (Gobiocypris rarus) and analyzed 886 semi-volatile organic compounds (SVOCs) in effluents from four secondary wastewater treatment plants (SWTP A-D) and a tertiary wastewater treatment plant (TTP E) that utilized various common treatment processes in northern China. The final effluents from SWTPs and TTP E all exhibited estrogenic effects, increasing male fish plasma vitellogenin (VTG) contents and estradiol/testosterone (E2/T) ratios. Key regulating genes in the male fish liver including vtg1, vtg3, era, erβ, and cyp19a were upregulated. TTP E demonstrated high performance in reducing estrogenic activity in the effluents, with a reduction of 64% in integrative biomarkers of estrogenic response (IBR). UV disinfection at SWTPs removed IBR by 14%− 33%, while ozone disinfection at TTP E did not reduce IBR. Several SVOCs including alkanes, chlorobenzenes, and phthalates, detected at ng/L to µg/L level, significantly correlated with effluent estrogenic activity. Our findings suggest the necessity and the potential means to improve the efficiency of current wastewater treatment approaches to achieve better protection for aquatic organisms against the joint effects of mixtures of various categories of micropollutants in effluents.

Cost Analysis and Health Risk Assessment of Wastewater Reuse from Secondary and Tertiary Wastewater Treatment Plants

Irrigation with reclaimed water is a widespread solution to coping with water scarcity, especially in the Middle East and North Africa (MENA) region. This paper presents a systematic evaluation approach of six treatment alternatives proposed for Alexandria WWTP in Egypt as an applied example. This approach evaluates the effluent quality and cubic meter price from the proposed treatment alternatives while managing the health risks associated with reclaimed water irrigation. Rotavirus, Salmonella, Giardia duodenalis, and Ascaris were studied as waterborne pathogens. A quantitative microbial risk assessment model was used for the estimation of annual infection risks. The exposure scenarios include farmers and vegetable consumers. Activated sludge provided the lowest costs; however, it gave the lowest efficiencies and highest health risks. On the other hand, the highest efficiency and lowest health risks were obtained by the membrane bioreactor. The resulting price of a cubic meter of treated wastewater, used in irrigation, ranged from 0.082 to 0.133 USD. Irrigation using tertiary-treated wastewater achieved the target infection risk for unrestricted irrigation without using advanced treatment facilities. The results of this study could give a comprehensive view of reusing wastewater to decision-makers to address both water and food poverty not only in Egypt but also in other countries in MENA with similar economic and agro-ecological conditions.

Identification and removal of sulfhydryl groups from wastewaters

Thiols represent a source of environmental pollution especially wastewater. This work proposed to study the elaboration of cellulose acetate polymer-based membranes for their application in the removal of a sulfhydryl groups of real biological treated wastewaters. The addition of nanoparticles to membranes improves the water purification capacity by promoting a good separation of sulfur, more particularly by ZnO-NPs. We used ultrafiltration membrane-assisted ZnO and TiO2 NPs application on real effluents from different biological treatment plants. We identified the hydrosulfite (thiol) group in wastewater and we used membrane processes ultrafiltration technique for sulfur removal. We evaluated the degradation of sulfur in biological treatment plants in Tunisia: The urban wastewater treatment plant or the conventional plant of Rades Malienne is a secondary biological wastewater treatment plant noted STEP1. The rural wastewater treatment plant based vertical flow planted with Phragmites australis from the Grombalia region noted STEP2 and rural wastewater treatment plant based horizontal flow planted with Phragmites australis from the Grombalia region noted STEP3. STEP1 is found to be more loaded with sulfur. Application of AC-ZnO membrane gives 99.07% and 99.55% of sulfur removal from wastewater of STEP1 and STEP3. STEP3 is 50 times less charged on sulfur than STEP1. We suggested that when the sulfur content is high, this leads to an increase in mineral elements. This could be explained by the interactions between thiols and the major elements that cause mineral pollution.

Evaluation of microplastics removal efficiency at a wastewater treatment plant discharging to the Sea of Marmara

Levels, composition and fate of microplastics (MPs) were investigated along different compartments of a secondary wastewater treatment plant (WWTP) with nutrient removal on the northern Sea of Marmara coast (Istanbul, Turkey). When all samples were combined, fibers were found to be the most dominant particles, followed by hard fragments. 500–1000 μm and 1000–2000 μm were the most common size ranges for wastewater and sludge, respectively. Rate of removal differed for sizes and shapes of the particles combined. Hard fragments of <500 μm and fibers of size ranges 250–500 μm and 1000–2000 μm were more successfully removed within the WWTP. Size averages increased throughout the WWTP units. 84.6–93.0% removal was achieved for grab and 3-hr composite samples. Despite the high removal rates of the WWTP, 2,934 × 106 microplastic particles/d were released in the effluent to the Sea of Marmara. Our results show that the Ambarlı WWTP considerably contributes to microplastics contamination in the Sea of Marmara since the plant has a high operating capacity.

Water quality index including periphyton chlorophyll-a in forested urban watersheds from Tierra del Fuego (Argentina)

The city of Ushuaia, Argentina, has experienced a rapid and unorganized population growth with possible consequences on the dynamics and functioning of urban lotic ecosystems. Urban expansion was not largely accompanied by the development of infrastructure for the provision of services such as drinking water and sewers to all the population. Currently, only 65% of the population is connected to the main sewage system (pre-treatment) and the city does not have a secondary wastewater treatment plant yet. We evaluated the impact of wastewater discharges and non-point contamination on the water quality of the three main water courses that cross the city of Ushuaia: Pipo river (PR), Buena Esperanza stream (BES) and Arroyo Grande river (AGR). We sampled four sites per watershed from spring to autumn in two consecutive years (2018 and 2019): S1 (not urbanized at the upper section), S2 (transitional section), S3 (urbanized at the middle-low section), and S4 (urbanized, close to the outlet). We developed the Fuegian Water Quality Index (F_WQI) as a tool for environmental monitoring in forest streams which includes several indicators of organic inputs (dissolved oxygen, nitrogen-ammonium, total phosphorus, fecal coliform bacteria) and periphyton chlorophyll-a (Peri Chl-a). The variables were ranked and weighed, and the index was constructed using a mathematical formula. Urbanization negatively impacted the water quality of these ecosystems; the F_WQI showed “very bad” and “bad” water quality categories at S4 in BES and AGR, both sites impacted by wastewater discharges and large percentage of urbanized area. Likewise, in the PR watershed, with less urbanization and sewage discharges, the F_WQI indicated “very good” water quality. The F_WQI summarizes the water quality of forested watersheds in a simple numerical scale, resulting in a useful tool for monitoring studies in temperate rivers and streams. We encourage the inclusion of Peri Chl-a in water quality indices, due to its ubiquity in these ecosystems and the fact that it increased the sensitivity of the index.

Solar photon-Fenton process eliminates free plasmid DNA harboring antimicrobial resistance genes from wastewater

This work aimed to assess the elimination and inactivation of resistance-conferring plasmids (RCPs) present in suspension in secondary wastewater by solar photo-Fenton as these are important vectors for the dissemination of antimicrobial resistance. Experiments were performed in synthetic secondary wastewater (SWW) and municipal wastewater treatment plant effluent (MWWTPE). Solar photo-Fenton (50 mg L−1 of H2O2 and 30 mg L−1 of Fe2+) was carried out for 60 min at neutral pH by applying the intermittent iron addition strategy. The removal of RCPs was assessed by Real-Time Polymerase Chain Reaction (qPCR). The transformation of competent non-resistant E. coli was used to evaluate the inactivation of target RCPs harboring antibiotic resistance genes (ARGs) to ampicillin (pSB1A2) or kanamycin (pSB1K3) after treatment and controls. Solar photo-Fenton completely removed RCPs initially present in both matrixes (SWW and MWWTPE), showing enhanced performance compared to the dark Fenton process. Both RCPs were inactivated after 30 min of solar photo-Fenton treatment, while 60 min were necessary to achieve the same effect for the dark Fenton reaction under similar conditions. These results indicate the potential of solar photo-Fenton to improve wastewater quality and reduce the spread of antimicrobial resistance in the environment by hampering the discharge of cell-free RCPs present in suspension in MWWTP onto environmental waters.

Fate and persistence of antibiotic-resistant bacteria and genes through a multi-barrier treatment facility for direct potable reuse

Abstract Given the availability of technological solutions and guidelines for safe drinking water, direct potable reuse of reclaimed water has become a promising option to overcome severe lack of potable water in arid regions. However, the growing awareness of the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) in corresponding raw wastes has led to new safety concerns. This study investigated the fate of ARB and intracellular and extracellular ARG after each treatment step of an advanced water treatment facility in Windhoek, Namibia. The New Goreangab Water Reclamation Plant (NGWRP) produces drinking water from domestic secondary wastewater treatment plant effluent and directly provides for roughly a quarter of Windhoek's potable water demand. Procedures to study resistance determinants were based on both molecular biology and culture-based microbiological methods. TaqMan real-time PCR was employed to detect and quantify intracellular resistance genes sul1, ermB, vanA, nptII and nptIII as well as extracellular resistance gene sul1. The NGWRP reduced the amount of both culturable bacterial indicators as well as the resistance genes to levels below the limit of detection in the final product. The main ozonation and the ultrafiltration had the highest removal efficiencies on both resistance determinants.

Irrigation with reclaimed water in an urban watershed and nutrient levels in adjacent streams.

Reclaimed water, used commonly for lawn irrigation, can be a complicating factor for watershed managers addressing sources of nonpoint source pollution. This research examined concentrations of total nitrogen (TN) and total phosphorus (TP) in the reclaimed water effluent from the City of St. Petersburg wastewater treatment plant (WWTP) (secondary treatment), the Pinellas County WWTP (tertiary treatment), and four tributary sites in the highly urbanized Joe's Creek watershed in Pinellas County, Florida. Two of the four tributary sites are control sites (35-10 and 35-11). The Bonn Creek tributary is within the tertiary treatment service area, and Miles Creek tributary is within the secondary treatment service area. For the 6-year study period, results show that Bonn Creek's mean TN concentration of 0.92mg/L was lower than Miles Creek's (1.077mg/L), and both control sites were the lowest (0.66mg/L and 0.71mg/L, respectively). Similar results were found for TP concentrations. Bonn Creek's TP concentration was 0.084mg/L slightly lower than Miles Creek's (0.096mg/L), and both control sites were the lowest (0.064mg/L and 0.07mg/L, respectively). Potential TN and TP loadings from each WWTP to their service areas were calculated, as well as potential TN loadings to each landscape. PRACTITIONER POINTS: We investigated TN and TP concentrations from secondary and tertiary WWTPs and streams that receive runoff from two neighborhoods using reclaimed water from these plants for landscape irrigation. As expected, reclaimed water from the secondary WWTP had higher TN and TP concentrations. The surface water concentrations of TN and TP in the adjacent streams within the reclaimed service areas were higher than the concentrations at the control sites outside of the reclaimed service areas. The nitrogen applied to landscapes in the secondary WWTP reclaimed service area was ten times higher than the nitrogen applied to landscapes in the tertiary WWTP reclaimed service area.