Profiling wastewater characteristics in intra-urban catchments using online monitoring stations.

This study aims to investigate the differences in intra-urban catchments with different characteristics through real-time wastewater monitoring. Monitoring stations were installed in three neighbourhoods of Barcelona to measure flow, total chemical oxygen demand (COD), pH, conductivity, temperature, and bisulfide (HS-) for 1 year. Typical wastewater profiles were obtained for weekdays, weekends, and holidays in the summer and winter seasons. The results reveal differences in waking up times and evening routines, commuting behaviour during weekends and holidays, and water consumption. The pollutant profiles contribute to a better understanding of pollution generation in households and catchment activities. Flows and COD correlate well at all stations, but there are differences in conductivity and HS- at the station level. The article concludes by discussing the operational experience of the monitoring stations.

Seasonal patterns, fate and ecological risk assessment of pharmaceutical compounds in a wastewater treatment plant with Bacillus bio-reactor treatment.

Pharmaceutical compounds (PhCs) pose a growing concern with potential environmental impacts, commonly introduced into the environment via wastewater treatment plants (WWTPs). The occurrence, removal, and season variations of 60 different classes of PhCs were investigated in the baffled bioreactor (BBR) wastewater treatment process during summer and winter. The concentrations of 60 PhCs were 3400 ± 1600 ng/L in the influent, 2700 ± 930 ng/L in the effluent, and 2400 ± 120 ng/g dw in sludge. Valsartan (Val, 1800 ng/L) was the main contaminant found in the influent, declining to 520 ng/L in the effluent. The grit chamber and BBR tank were substantially conducive to the removal of VAL. Nonetheless, the BBR process showcased variable removal efficiencies across different PhC classes. Sulfadimidine had the highest removal efficiency of 87 ± 17% in the final effluent (water plus solid phase). Contrasting seasonal patterns were observed among PhC classes within BBR process units. The concentrations of many PhCs were higher in summer than in winter, while some macrolide antibiotics exhibited opposing seasonal fluctuations. A thorough mass balance analysis revealed quinolone and sulfonamide antibiotics were primarily eliminated through degradation and transformation in the BBR process. Conversely, 40.2 g/d of macrolide antibiotics was released to the natural aquatic environment via effluent discharge. Gastric acid and anticoagulants, as well as cardiovascular PhCs, primarily experienced removal through sludge adsorption. This study provides valuable insights into the intricate dynamics of PhCs in wastewater treatment, emphasizing the need for tailored strategies to effectively mitigate their release and potential environmental risks.

Legacy Mercury Re-emission and Subsurface Migration at Contaminated Sites Constrained by Hg Isotopes and Chemical Speciation.

The re-emission and subsurface migration of legacy mercury (Hg) are not well understood due to limited knowledge of the driving processes. To investigate these processes at a decommissioned chlor-alkali plant, we used mercury stable isotopes and chemical speciation analysis. The isotopic composition of volatilized Hg(0) was lighter compared to the bulk total Hg (THg) pool in salt-sludge and adjacent surface soil with mean ε202HgHg(0)-THg values of -3.29 and -2.35‰, respectively. Hg(0) exhibited dichotomous directions (E199HgHg(0)-THg = 0.17 and -0.16‰) of mass-independent fractionation (MIF) depending on the substrate from which it was emitted. We suggest that the positive MIF enrichment during Hg(0) re-emission from salt-sludge was overall controlled by the photoreduction of Hg(II) primarily ligated by Cl- and/or the evaporation of liquid Hg(0). In contrast, O-bonded Hg(II) species were more important in the adjacent surface soils. The migration of Hg from salt-sludge to subsurface soil associated with selective Hg(II) partitioning and speciation transformation resulted in deep soils depleted in heavy isotopes (δ202Hg = -2.5‰) and slightly enriched in odd isotopes (Δ199Hg = 0.1‰). When tracing sources using Hg isotopes, it is important to exercise caution, particularly when dealing with mobilized Hg, as this fraction represents only a small portion of the sources.

New multi-source waste co-incineration and clustering park operating model for small- and medium-sized city: A case study in China.

With improvements in urban waste management to promote sustainable development, an increasing number of waste types need to be sorted and treated separately. Due to the relatively low amount of waste generated in small- and medium-sized cities, separate treatment facilities for each waste type lack scale, waste is treated at a high cost and low efficiency. Therefore, industrial symbiosis principles are suggested to be used to guide collaborative waste treatment system of multi-source solid wastes, and co-incineration is the most commonly used technology. Most existing studies have focused on co-incineration of one certain waste type (such as sludge or medical waste) with municipal solid waste (MSW), but the systematic design and the comprehensive benefits on a whole city and park level have not been widely studied. Taking the actual operation of a multi-source waste co-incineration park in south-central China as an example, this study conducted a detailed analysis of the waste-energy-water metabolism process of MSW, sludge, food waste, and medical waste co-incineration. The environmental and economic benefits were evaluated and compared with the single decentralized waste treatment mode. The results showed that the multi-source waste co-incineration and clustering park operating model was comprehensively superior to the single treatment mode, greenhouse gases and human toxicity indicators were decreased by 11.87% and 295.74%, respectively, and the internal rate of return of the project was increased by 29.35%. This mainly benefits from the synergy of technical system and the economies of scale. Finally, this research proposed policy suggestions from systematic planning and design, technical route selection, and an innovative management mode in view of the potential challenges.

[Contamination Characteristics and Ecological Risk Assessment of Pharmaceuticals and Personal Care Products in Drains Flowing into the Yellow River of Ningxia].

Pharmaceuticals and personal care products (PPCPs) are a group of emerging contaminants causing detrimental effects on aquatic living organisms even at low doses. To investigate the contamination characteristics and ecological risks of PPCPs in drains flowing into the Yellow River of Ningxia, 21 PPCPs were detected and analyzed using solid phase extraction and ultra-high performance liquid chromatography-mass spectrometry in this study. All 21 targeted compounds were detected in the drains, with total concentrations ranging from 47.52 to 1 700.96 ng·L-1. Ciprofloxacin, acetaminophen, benzophenone-3, and diethyltoluamide were the more commonly detected compounds, with detection frequencies exceeding 80%. The five highest-concentration PPCPs were acetaminophen, diethyltoluamide, caffeine, benzophenone-3, and levofloxacin, with the maximum concentrations of 597.21, 563.23, 559.00, 477.28, and 473.07 ng·L-1, respectively. Spatial analysis showed that the pollution levels of PPCPs in the drains of the four cities were different, with average concentrations of ∑PPCPs in the order of Yinchuan>Shizuishan>Wuzhong>Zhongwei. The total concentration of PPCPs before flowing into the Yellow River ranged from 124.82 to 1 046.61 ng·L-1. Source analysis showed that livestock and poultry breeding wastewater was the primary source for sulfadiazine and oxytetracycline, whereas medical wastewater was the primary source for levofloxacin and ciprofloxacin. The primary sources of triclocarban and triclosan were domestic sewage and industrial wastewater, whereas the primary source of caffeine and diethyltoluamide was domestic sewage. The pollution of diciofenac, cimetidine, triclocarban, and triclosan in the drains was positively correlated with the regional population and economic development level. The ecological risk assessment indicated that levofloxacin, diclofenac, gemfibrozil, benzophenone-3, and triclocarban posed high risks to aquatic organisms in drains flowing into the Yellow River. It is worthwhile to consider the mixture risk of the PPCPs that exhibited high risk at most sampling sites.

Biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793): Tools to evaluate the environmental quality of aquaculture areas.

The discharge of sanitary sewage into the bays of the Florianópolis Metropolitan Area (Southern Brazil), has led to the contamination of oyster farms. Consequently, linear alkylbenzenes (LABs) were quantified in the sediment, and the biochemical responses in gills and digestive gland of oysters from six farms were assessed. Our findings revealed elevated levels of LABs in the sediment of the Imaruim and Serraria farms. Additionally, alterations were observed in the antioxidant enzymes: catalase, glutathione peroxidase and superoxide dismutase in both oyster tissue from the Serraria, Santo Antonio de Lisboa and Sambaqui farms. Furthermore, correlation analyses indicated strong and moderate associations between biochemical responses, organic contaminants, and certain physicochemical parameters. Consequently, our results demonstrated the activation of the antioxidant system in oysters, representing a protective response to the presence of sanitary sewage and other contaminants. Therefore, we propose the utilization of biochemical biomarkers for monitoring the environmental quality of farms.

Evaluating the environmental and economic performance of biological and advanced biological wastewater treatment plants by life cycle assessment and life cycle costing.

The primary objective of this study is to assess and establish benchmarks for environmental and economic sustainability of biological and advanced biological wastewater treatment plants (WWTPs) with different treatment technologies and characteristics. Furthermore, the study aims to determine the beneficial role of WWTPs to reduction of eutrophication potential. Environmental and economic sustainability of ten municipal WWTPs was assessed using life cycle assessment (LCA) and life cycle costing (LCC). In the first section of the study, LCA was performed to determine the environmental performance of the WWTPs. Furthermore, net environmental benefit (NEB) approach was implemented to reveal the beneficial role of WWTPs to eutrophication potential. In the subsequent section, LCA-based LCC was conducted by integrating the results of LCA. The most significant environmental impact was determined as marine aquatic ecotoxicity, which is highly affected from the generation and transmission of electricity consumed in the WWTPs. Wastewater recovery and co-incineration of sewage sludge in cement kiln ensure significant environmental savings on ozone layer depletion, human toxicity, acidification, photochemical oxidation, and abiotic depletion (fossil fuel) potential. Considering NEB approach, the highest NEB values were found for the WWTPs with the higher organic load and nutrient concentration in the influent. The results of LCC in WWTPs varied between 0.21 and 0.53 €/m3. External (environmental) costs were evaluated higher than internal (operational) costs for all selected WWTPs. While eutrophication was the highest among environmental costs, electricity cost was the highest among operational costs for almost all WWTPs.

A Unique Monitoring Method for Fecal and Sewage-Derived Chemical Pollution Utilizing International Pellet Watch Approach.

This study established a unique approach to assess fecal contamination by measuring fecal sterols, especially coprostanol (5ß-cholestanol-3ß-ol, 5ß) and cholestanol (5α-cholestan-3ß-ol, 5α) and their ratio 5ß/(5ß + 5α) alongside triclosan (TCS) and methyl-triclosan (MTC) in beached plastic pellets across 40 countries. Coprostanol concentrations ranged from 3.6 to 8190 ng/g pellet with extremely high levels in densely populated areas in African countries. The 5ß/(5ß + 5α) ratio was not affected by the difference in residence time of pellets in aquatic environments, and their spatial pattern showed a positive correlation with that of sedimentary sterols, demonstrating its reliability as an indicator of fecal contamination. Pellets from populated areas of economically developing countries, i.e., Africa and Asia, with lower coverage of wastewater treatment exhibited higher 5ß/(5ß + 5α) ratios (∼0.7) corresponding to ∼1% sewage in seawater, while pellets from developed countries, i.e., the USA, Canada, Japan, and Europe, with higher coverage of modern wastewater treatment displayed lower ratios (∼0.5), corresponding to the first contact limit. Triclosan levels were higher in developing countries (0.4-1298 ng/g pellet), whereas developed countries showed higher methyl-triclosan levels (0.5-70 ng/g pellet) due to TCS conversion during secondary treatment. However, some samples from Japan and Europe displayed higher TCS levels, suggesting contributions from combined sewage overflow (CSO). Combination of 5ß/(5ß + 5α) and MTC/TCS ratios revealed extreme fecal contamination from direct input of raw sewage due to inadequate treatment facilities in some African and South and Southeast Asian countries.

Foam control in lakes and sewage receiving water bodies: A pre-emptive approach using decentralized inline water treatment design.

Hideous and persistent foams on surface water bodies are global issues with far-reaching environmental consequences. This study examines Bellandur Lake (Bengaluru, India) plagued by foam since 2005 due to surfactant-laden untreated sewage ingress. Bellandur Lake receives 258 million liters of inadequately treated sewage daily, constituting 47% of its total volume. Yearlong water quality monitoring reveals that a) high surfactant levels (up to 17.8 ± 1 ppm) and b) prevalent anoxic conditions at lake inlets. Laboratory experiments show that controlled aeration achieved >90% surfactant degradation within 30 h at 3.5 ppm of dissolved oxygen conditions, indicating the need for an aeration chamber design based on the required residence time for inline water treatment. Based on these findings, a design of an inline wastewater treatment system to be installed at sewage entry points into the lake is presented in this work. The inline system was based on experimentally validated BioWin software. Simulations show that recirculating sludge enhances treatment efficiency, achieving effective surfactant degradation in 20 h (2/3rd original time) of residence time. Predictions suggest <1 ppm surfactant levels in the receiving water body, meeting local discharge norms to prevent frothing. This holistic approach, proposed for the first time, could serve as a blueprint for managing foam-related challenges in other waterbodies, offering insights into design, stakeholder engagement, and process optimization.

Occurrence, removal efficiency, and emission of antibiotics in the sewage treatment plants of a low-urbanized basin in China and their impact on the receiving water.

Sewage treatment plants (STPs) are primary sources of antibiotics in aquatic environments. However, limited research has been conducted on antibiotic attenuation in STPs and their downstream waters in low-urbanized areas. This study analyzed 15 antibiotics in the STP sewage and river water in the Zijiang River basin to quantify antibiotic transport and attenuation in the STPs and downstream. The results showed that 14 target antibiotics, except leucomycin, were detected in the STP sewage, dominated by amoxicillin (AMOX), ofloxacin, and roxithromycin. The total antibiotic concentration in the influent and effluent ranged from 158 to 1025 ng/L and 99.9 to 411 ng/L, respectively. The removal efficiency of total antibiotics ranged from 54.7 % to 75.7 % and was significantly correlated with total antibiotic concentration in the influent. The antibiotic emission from STPs into rivers was 78 kg/yr and 4.6 g/km2yr in the Zijiang River basin. The total antibiotic concentration downstream of the STP downstream was 23.6 to 213 ng/L and was significantly negatively correlated with the transport distance away from the STP outlets. Antibiotics may pose a high ecological risk to algae and low ecological risk to fish in the basin. The risk of AMOX and ciprofloxacin resistance for organisms in the basin was estimated to be moderate. This study established antibiotic removal and attenuation models in STPs and their downstream regions in a low-urbanized basin, which is important for simulating antibiotic transport in STPs and rivers worldwide.

Effect of tourist activity on wastewater quality in selected wastewater treatment plants in the Balearic Islands (Spain).

Unregulated sewage discharge into the sea poses a considerable danger to marine ecosystems, with coastal regions being particularly vulnerable to this because of the impact of tourism. This issue is amplified during the summer season, as the Balearic Islands are a heavily frequented destination. This study aims to determine the water quality in five different wastewater treatment plants (WWTPs) representative on the islands. For this purpose, we analysed several parameters, including biochemical oxygen demand (BOD), chemical oxygen demand (COD), treated water flow, suspended solids (SS), nitrates (N) and phosphorus (P), at the inlet and outlet of the WWTPs for 5 years. We set particular thresholds for each parameter and documented any breach by comparing the findings with the existing regulations. The least favourable results indicate non-compliance regarding N and P levels throughout the entire study period, as well as a lack of reduction percentage. Furthermore, flow analysis reflects the significant influence of tourism on water quality, with notable increases in both population and treated water volume during the peak tourist season. Overall, the investigation offers a robust foundation for comprehending water quality in relation to coastal landscape in the Balearic Islands. It pinpoints significant worry spots and underscores tourism's immediate impact on this ecological feature.

Comprehensive assessment of microplastics in Australian biosolids: Abundance, seasonal variation and potential transport to agroecosystems.

Striving towards a circular economy, the application of treated sewage sludge (biosolids) to land is an opportunity to improve the condition of the soil and add essential nutrients, in turn reducing the need for fertilisers. However, there is an increasing concern about microplastic (MP) contamination of biosolids and their transport to terrestrial ecosystems. In Australia, agriculture is the largest biosolids end-user, however, there is limited understanding of MPs in Australian biosolids. Also, while the method to isolate MPs from biosolid is established, a need to extract and analyse MPs more efficiently is still pressing. In this study, we comprehensively quantified and characterised MPs in 146 biosolids samples collected from thirteen wastewater treatment plants (WWTPs) including different seasons. We have optimised an oxidative-enzymatic purification method to overcome current limitations for MP identification in complex samples and accurately report MPs in biosolids. This method enabled removal of >93 % of dry weight of organic material and greatly facilitated the MPs instrumental analysis. The concentration of MPs (>20 µm) in all biosolids samples ranged from 11 to 150 MPs/g dry weight. Abundance of MPs was affected by seasons with higher abundance of MPs usually found during cold and wet seasons. Despite seasonal variations, polyethylene terephthalate, polyurethane and polymethyl methacrylate were the most abundant polymers. Smaller MPs (20 to 200 µm) comprised >70 % of all detected MPs with a clear negative linear relationship observed between MP size and abundance. Per capita concentration of MPs in biosolids across all studied WWTPs was 0.7 to 21 g MPs per person per year. Therefore, biosolids are an important sink and source of MPs to agroecosystems, emphasising the need to more comprehensively understand the fate, impact and risks associated with MPs on agricultural soils.

Stereoselective analysis of chiral pesticides: a review.

Chiral organic pollutants, including pesticides, herbicides, medicines, flame retardants, and polycyclic musk, represent a significant threat to both the environment and human health. The presence of asymmetric centers in the structure of chiral pesticides introduces stereoisomers with distinct distributions, fates, biomagnification capacities, and cytotoxicities. In aquatic environments, pesticides, as persistent/pseudo-persistent compounds, have been detected in substantial quantities, posing severe risks to non-target species and, ultimately, public health through water supply and food exposures. In response to this environmental challenge, stereoselective analytical methods have gained prominence for the identification of pesticide/drug enantiomers in recent years. This review examines the environmental impact of chiral pesticides, emphasizing the distinct biological activities and distribution patterns of their stereoisomers. By highlighting the advancements in liquid chromatography for enantiomeric analysis, the review aims to underscore the urgent need for a comprehensive understanding of these pollutants to facilitate informed remediation strategies and ensure the safer dispersal of chiral organic pollutants in the environment, thereby addressing the potential risks they pose to ecosystems and human health. Future research should focus on developing sustainable and efficient methodologies for the precise analysis of stereoisomers in complex matrices, particularly in sewage water, emphasizing the importance of sewage processing plants in ensuring water quality.

Quantifying the removal of polybrominated diphenyl ethers (PBDEs) in physical, chemical, and biological sludge treatment systems.

Polybrominated diphenyl ethers (PBDE) are priority contaminants historically used as flame retardants. PBDEs are known to occur in wastewater biosolids posing potential concerns with the beneficial land application of the biosolids. This study evaluated the removal of 21 congeners in nine full-scale sludge treatment systems including pelletization (P), alkaline stabilization (AS), and aerobic (AE) and anaerobic (AN) digestion. It is the first study to conduct a mass balance analysis of a broad spectrum of PBDEs during physical, chemical, and biological sludge treatment. The PBDE congener pattern in raw sludge and biosolids samples was consistent with commercial formulations. The fully brominated congener BDE-209 dominated biosolids from all sites with an average concentration of 620 ng/g dry weight (dw), followed by BDE-99 (173 ng/g dw) and BDE-47 (162 ng/g dw). Mass balance analysis on the P and AS processes showed no change in PBDE mass flows with treatment. However, aerobic and anaerobic digestion processes reported significant levels of removal and formation of individual congeners, though the results were not consistent between facilities. One aerobic digestion process (AE2) reported an overall average removal of 48%, whereas the other (AE1) reported very high levels of accumulation of tri- and tetraBDE congeners. Similarly, there were significant variations in PBDE behavior across the five anaerobic digestion plants studied. The plant with the longest solids retention time (SRT) (AN1) reported a moderate removal (50%) of overall PBDE loading and lower congeners, whereas other plants (AN2-AN5) showed significant low (-19%) to high (-166%) levels of formation of lower congeners. The results suggest that reduced SRTs result in formation of lower congeners while extended SRTs can lead to moderate removal of some PBDEs. Conventional sludge treatment result in low to moderate PBDE removal and advanced thermal conversion technologies may be needed to improve the contaminant removal during sludge treatment.

Comparison of benzotriazole ultraviolet stabilizers (BUVs) removal from wastewater after subsequent stages of sequencing batch reactor (SBR) treatment process.

The research focused on benzotriazole ultraviolet stabilizers (BUVs) which are commonly used compounds despite being found dangerous, e.g. promoting breast cancer cell proliferation, damaging vital organs such as hearts, brains livers and kidneys. The aim of the study was to analyse the efficiency and removal rate of BUVs from wastewater depending on the quantity of tested compounds and SBR anaerobic-aerobic conditions. The study was conducted in sequencing batch reactors (SBRs - 17 L) with real flocculent activated sludge (8 L) and model wastewater (5 L) containing UV-326, UV-327, UV-328, UV-329 and UV-P from 50 to 600 µg∙L-1. The SBR were operated in 390 cycles of 7 h and 10 min over 130 days. The similarity of the technological parameters of the treatment process to those used in a real wastewater treatment plant was maintained. Efficiency removal of individual BUVs was strictly dependent on the dose of compounds introduced into wastewater and ranged from 68.2 to 97 %. Removal of UV-329 occurred with lowest efficiency (from 68.2 to 85.2 %) while UV-326 was most efficiently removed from the wastewater (from 94.1 to 97 %). UV-329 was removed from wastewater with the lowest (0.0968-0.9524 µg∙L-1∙min-1) average removal rate while UV-327 with the highest (0.16-1.3357 µg∙L-1∙min-1), irrespective of BUVs dose in the influent. Secondary release of BUVs into the wastewater occurred in SBR during the settling phase and was dependent on the type and concentration of the BUVs in the raw wastewater. This occurrence was noted for UV-326 ≥ 100; UV-327 = 600; UV-328 ≥ 200; UV-329 ≥ 50 and UV-P ≥ 100 µg∙L-1. The settling phase needs to be shortened to the required minimum. This is an important conclusion for WWTPs in regards to SBR cycle duration and technological parameters of the treatment process.

Analysis of biogas production from sewage sludge combining BMP experimental assays and the ADM1 model.

The Anaerobic Digestion Model No. 1 (ADM1) was employed to simulate methane (CH4) production in an anaerobic reactor (AR), and the associated bench-scale biochemical methane potential (BMP) assay, having sewage sludge (SWS) from a municipal wastewater treatment plant (WWTP) as feedstock. The SWS presented the following physical-chemical characteristics: pH (7.4-7.6), alkalinity (2,382 ± 100 mg CaCO3 L-1), tCOD (21,903 ± 1,000 mg L-1), TOC (895 ± 100 mg L-1), TS, TVS, and VSS (2.0%, 1.1%, and 0.8%, respectively). The BMP assay was conducted in six replicates under anaerobic mesophilic conditions (37 ± 0.1°C) for 11 days with a CH4 yield registered of 137.6 ± 6.39 NmL CH4 or 124 ± 6.72 CH4 g-1 VS-1. When the results obtained with the BMP bench-scale reactors were compared to the output generated with computational data by the ADM1 model having as input data the same initial sewage tCOD, similar cumulative CH4 production curves were obtained, indicating the accuracy of the ADM1 model. This approach allowed the characterization of the sludge and estimation of its biogas production potential. The combination of BMP assays, experimental data, and ADM1 model simulations provided a framework for studying anaerobic digestion (AD) processes.

The occurrence of heavy metals and antimicrobials in sewage sludge and their predicted risk to soil - Is there anything to fear?

The study assessed the occurrence of legally-monitored heavy metals and unmonitored antimicrobials in sludge from small, medium, large and very large municipal wastewater treatment plants (WWTPs), and the predicted environmental risk and risk of resistance selection associated with sludge administration to soil. The temporal variations of the studied compounds in sludge and associated risks to soil were determined by sampling over a year. Although the highest concentrations of heavy metals were noted in sludge from the largest WWTP, i.e. from 1.50 mg/kg (mean 1.61 mg/kg) for Cd to 2188 mg/kg (mean 1332 mg/kg) for Zn, the obtained values only reached a few percent of the legal limits. The same WWTP also demonstrated lower concentrations of antimicrobials compared to the smaller ones. The highest concentrations of antimicrobials, ranging from 24.04 µg/kg for trimethoprim to 900.24 µg/kg for tetracycline, were found in the small and medium WWTPs. However, due to lack of regulations at the national and EU levels, the results cannot be compared with legal limits. Principal Component Analysis (PCA), cluster and heatmap analysis separated samples according to WWTP size. Small WWTP demonstrated correlation with antimicrobials (tetracycline, trimethoprim, clindamycin, ciprofloxacin and ofloxacin), while the large and very large WWTP revealed correlations with heavy metals (Cu and Cr). The obtained environmental risk quotients confirmed that the heavy metals did not present a threat, measured either as individual risk quotients (RQenv), cumulative risk (RQcumulative) or risk of mixture of heavy metals (RQmix-metals). In the case of antimicrobials, only tetracycline demonstrated moderate RQenv, RQcumulative and RQmix-antimicrobials in the small WWTP sludge, with values of 0.1 to 1. Our findings highlight the importance of monitoring sewage sludge before soil application, especially from small WWTPs, to reduce the potential environmental impact of antimicrobials. They also confirm our previous data regarding the environmental risk associated with various toxic compounds, including emerging contaminants, in the sludge from small WWTPs.

Evolution of chlorinated paraffin and olefin fingerprints in sewage sludge from 1993 to 2020 of a Swiss municipal wastewater treatment plant.

Exposure of humans to chlorinated paraffins (CPs) and chlorinated olefins (COs) can occur via contact with CP-containing plastic materials. Such plastic materials can contain short-chain CPs (SCCPs), which are regulated as persistent organic pollutants (POPs) under the Stockholm Convention since 2017. Municipal wastewater treatment plants (WWTP) collect effluents of thousands of households and their sludge is a marker for CP exposure. We investigated digested sewage sludge collected in the years 1993, 2002, 2007, 2012, and 2020 from a Swiss WWTP serving between 20000 and 23000 inhabitants. A liquid chromatography mass spectrometry (R > 100000) method, in combination with an atmospheric pressure chemical ionization source (LC-APCI-MS), was used to detect mass spectra of CPs and olefinic side products. A R-based automated spectra evaluation routine (RASER) was applied to search for ∼23000 ions whereof ∼6000 ions could be assigned to CPs, chlorinated mono- (COs), di- (CdiOs) and tri-olefins (CtriOs). Up to 230 CP-, 120 CO-, 50 CdiO- and 20 CtriO-homologues could be identified in sludge. Characteristic fingerprints were deduced describing C- and Cl-homologue distributions, chlorine- (nCl) and carbon- (nC) numbers of CPs and COs. In addition, proportions of saturated and unsaturated material were determined together with proportions of different chain length classes including short- (SC), medium- (MC), long- (LC) and very long-chain (vLC) material. A substantial reduction of SCCPs of 84% was observed from 1993 to 2020. Respective levels of MCCPs, LCCPs and vLCCPs decreased by 61, 69 and 58%. These trends confirm that banned SCCPs and non-regulated CPs are present in WWTP sludge and higher-chlorinated SCCPs were replaced by lower chlorinated MCCPs. Combining high-resolution mass spectrometry with a selective and fast data evaluation method can produce characteristic fingerprints of sewage sludge describing the long-term trends in a WWTP catchment area.

Modeling spatiotemporal domestic wastewater variability: Implications for measuring treatment efficiency.

Continuously measuring the efficiency of wastewater treatment plants is crucial to progress in sanitation management. Regulations for decentralized wastewater treatment plants (WWTP) can include rudimentary specifications for sporadic sampling, unencouraging continuous monitoring, and missing crucial domestic wastewater (DW) variability, especially in low- and middle-income countries. However, few studies have focused on modeling and understanding spatiotemporal DW variability. We developed and calibrated an agent-based model (ABM) to understand spatial and temporal DW variability, its role in estimated WWTP efficiency, and provide recommendations to improve sampling regulations. We simulated DW variability at various spatial and temporal resolutions in Santa Ana Atzcapotzaltongo, Mexico, focusing on chemical oxygen demand (COD) and total suspended solids (TSS). The model results show that DW variability increases at higher spatiotemporal resolutions. Without a proper understanding of DW variability, treatment efficiency can be overestimated or underestimated by as much as 25% from sporadic sampling. Sensor measurements at 6-min intervals over 3 hours are recommended to overcome uncertainty resulting from temporal variability during heavy drinking water demand in the morning. Reporting of sewage catchment areas, population sizes, and sampling times and intervals is recommended to compare WWTP efficiencies to overcome uncertainty resulting from spatiotemporal variability. The proposed model is a useful tool for understanding DW variability. It can be used to estimate the impact of spatiotemporal variability when measuring WWTP efficiencies, support improvements to sampling regulations for decentralized sanitation, and alternatively for designing and operating WWTPs.

A 20-year shift in China's sewage sludge heavy metals and its feasibility of nutrient recovery in land use.

Recycling resources from wastewater is even more important for developing a more sustainable society. Disposing sewage sludge, which accumulates most pollutants and resources in sewage, is the main challenge in wastewater pollution control and resource utilization. Heavy metals (HMs) are the greatest constraint limiting the application of sewage sludge to land as a sustainable use of this material. We conducted a meta-analysis of the concentrations of HMs in Chinese sewage sludge by combining data from studies published from 2000 to 2019 (N = 8477). Over this period, the reported concentrations of HMs in sewage sludge declined in three stages (a fluctuating stage, a slight decrease stage, and a rapid and stable decrease stage). The results revealed that economic development and environmental policy implementation were the main factors mitigating HM pollution in sewage sludge in China. Moreover, if environmental regulations were strengthened and HM pollution-mitigation strategies were made consistent, such that the proportion of sewage sludge applied to land in China could be increased from 18.6% to 48.0% (the proportion applied to land in the United States), the ecosystem services analysis showed that huge ecological-economic benefits could be realized (3.1 billion Chinese Yuan) and the use of fertilizers could be substantially reduced (the use of nitrogen fertilizers by 8.5% and the use of phosphate fertilizers by 18.1%). This review shows that China should formulate a unified policy and interdepartmental committee for sustainable application of sewage sludge to land and wastewater resource recycling management.