Health risk assessment of organic micropollutants in greywater for potable reuse

Intra-event variations of organic micropollutants in highway runoff and a presedimentation-biofilter treatment facility

The study assessed the quality of highway runoff and a stormwater treatment system, focusing on intra-event variations (IEVs: variations within a runoff/effluent event) of the concentration of organic micropollutants (OMPs) including bisphenol-A, alkylphenols, polycyclic aromatic hydrocarbons (PAHs), and petroleum hydrocarbons (PHCs). IEVs of OMPs varied considerably with no particular recurring pattern in highway runoff and presedimentation effluent, displaying sporadic strong first flushes. IEVs are significantly associated with rainfall intensity variations, especially for particle-bound substances such as PAHs and PHCs. However, phenolic substances showed distinct IEV patterns compared to total suspended solids, PAHs, and PHCs, likely due to their higher solubility and mobility. Downstream sand filter (SF) and vegetated biofilter (BFC) mitigated IEVs, leading to more uniform discharge during outflow events. Although BFC's IEVs were indiscernible due to low effluent concentrations, SF's IEVs often peaked at the beginning of events (within the first 100 of ⁓600 m3), exceeding the lowest predicted non-effect concentrations for five PAHs, bisphenol-A, and octylphenol. This study highlights the advantage of IEV analysis over conventional event mean concentration analysis for identifying critical effluent stages, crucial for developing control strategies to protect sensitive water recipients or for reuse applications.

Biotransformation of micropollutants in moving bed biofilm reactors under heterotrophic and autotrophic conditions

We investigated the transformation of four pharmaceuticals (Diclofenac, Naproxen, Ibuprofen and Carbamazepine) in a moving bed biofilm reactor subjected to different COD/N ratios in four experimental phases. The shift from medium to high range COD/N ratio (i.e., 5:1 to 100:1) intensified the competition between heterotrophs and nitrifying communities, leading to a transition from co-existence of heterotrophic and autotrophic conditions with high COD removal and nitrification rate in phase I to dominant heterotrophic conditions in phase II. At lower range COD/N ratios (i.e., 1:2 and 1:8) in phase III and IV, autotrophic conditions prevailed, resulting in increased nitrification rates and high abundance of amoA gene in the biofilm. Such shifts in the operating condition were accompanied by notable changes in the biofilm concentrations, composition and abundance of microbial populations as well as biodiversity in the biofilms, which collectively affected the degradation rates of the pharmaceuticals. We observed higher kinetic rates per unit of biofilm concentration under autotrophic conditions compared to heterotrophic conditions for all compounds except Naproxen, indicating the importance of nitrification in the transformation of such compounds. The results also revealed a positive relationship between biodiversity and biomass-normalized kinetic rates of most compounds.

Greywater reuse as a key enabler for improving urban wastewater management

Sustainable water management is essential to guaranteeing access to safe water and addressing the challenges posed by climate change, urbanization, and population growth. In a typical household, greywater, which includes everything but toilet waste, constitutes 50-80% of daily wastewater generation and is characterized by low organic strength and high volume. This can be an issue for large urban wastewater treatment plants designed for high-strength operations. Segregation of greywater at the source for decentralized wastewater treatment is therefore necessary for its proper management using separate treatment strategies. Greywater reuse may thus lead to increased resilience and adaptability of local water systems, reduction in transport costs, and achievement of fit-for-purpose reuse. After covering greywater characteristics, we present an overview of existing and upcoming technologies for greywater treatment. Biological treatment technologies, such as nature-based technologies, biofilm technologies, and membrane bioreactors (MBR), conjugate with physicochemical treatment methods, such as membrane filtration, sorption and ion exchange technologies, and ultraviolet (UV) disinfection, may be able to produce treated water within the allowable parameters for reuse. We also provide a novel way to tackle challenges like the demographic variance of greywater quality, lack of a legal framework for greywater management, monitoring and control systems, and the consumer perspective on greywater reuse. Finally, benefits, such as the potential water and energy savings and sustainable future of greywater reuse in an urban context, are discussed.

Recognition, possible source, and risk assessment of organic pollutants in surface water from the Yongding River Basin by non-target and target screening

Organic pollutants in aquatic environment could have important implications on pollution stress on aquatic organisms and even on the risk of human exposure. Thus, revealing their occurrence in aquatic environment is essential for water quality monitoring and ecological risk purposes. In this study, a comprehensive two-dimensional gas chromatography connected with time-of-flight mass spectrometry (GC × GC-TOF-MS) was applied, to enable non-target and target analysis of pollutants in the Yongding River Basin. Based on the isotopic patterns, accurate masses and standard substances, certain environmental contaminants were tentatively identified which including polycyclic aromatic hydrocarbon (PAHs), organochlorine pesticides (OCPs), phenols, amines, etc. The compounds with the highest concentration were naphthalene (109.0 ng/L), 2,3-benzofuran (51.5 ng/L) and 1,4-dichlorobenzene (35.9 ng/L) in Guishui River. Wastewater treatment plants (WWTPs) discharges were a main source of pollutants in Yongding River Basin, as the types of compounds screened in the downstream river were relatively similar to those from WWTPs. According to the target analysis, a number of pollutants were selected due to the acute toxicity and cumulative discharge from WWTPs and downstream rivers. Three PAHs (naphthalene, Benzo(b)fluoranthene and pyrene) homologues showed moderate risk to fish and H. Azteca in Yongding River Basin, while the rest of the measured chemicals showed low ecological impact across the entire study area based on the risk assessment. The results are helpful for understanding the necessity of high-throughput screening analysis for assessing water quality of rivers and the discharge emissions of pollutants from WWTPs to the river environment.

New insight into fate and transport of organic compounds from pollution sources to aquatic environment using non-targeted screening: A wastewater treatment plant case study

A variety of chemicals discharged into the aquatic environment by the wastewater treatment plant (WWTP), which is a potential source of hazard to the ecological environment and human health. This study established a novel analytical method for all compounds using non-targeted screening to comprehensively explore the fate and transport of organic compounds from WWTP to aquatic environment. 3967 and 3636 features were detected in WWTP samples and river samples, respectively. Multi-level classification was applied to all identified compounds, and results showed that aliphatics were dominant in both abundance and response, accounting for an average of 35.49 % and 74.10 %, respectively. A total of 88 Emerging Contaminants (ECs), including 22 endocrine disrupting chemicals (EDCs), 12 pharmaceuticals and personal care products (PPCPs), 12 pesticides, 10 volatile organic compounds (VOCs), 5 persistent organic pollutants (POPs) and 27 chemicals with other uses, were identified from all compounds, and their traceability analysis was performed. Furthermore, the contribution rate of organic compounds from WWTP effluent to river was calculated to be 33.60 % by the analysis of source-sink relationship. An in-depth and comprehensive exploration of the fate and transport of all organic compounds will help to provide guidelines for the treatment technologies and achieve the traceability of pollutants.

Removal of microorganic pollutants in aquatic environment: The utilization of Fe(VI)

Microorganic pollutants (MOPs) in aquatic environment with low levels but high toxicity are harmful to ecosystem and human health. Fe(VI) has a dual-functional role in oxidation and coagulation, and can effectively remove MOPs, heavy metal, phosphate, particulates and colloids. Moreover, Fe(VI) can combine with traditional coagulants, or use as a pretreatment for membrane treatment because of its characters to generate nanoparticles by degradation in water. Based on the relevant toxicity experiments, Fe(VI) had been proved to be safe for the efficient treatment of MOPs. For better utilization of Fe(VI), its oxidation and coagulation mechanisms are summarized, and the knowledge about the control parameters, utilization methods, and toxicity effect for Fe(VI) application are reviewed in this paper. pH, different valences of iron, environmental substances, and other parameters are summarized in this study to clarify the important factors in the treatment of MOPs with Fe(VI). In the future study, aiming at cost reduction in Fe(VI) preparation, transportation and storage, enhancement of oxidation in the intermediate state, and better understanding the mechanism between interface and Fe(VI) oxidation will help promote the application of Fe(VI) in the removal of MOPs. This study offers guidelines for the application and development of Fe(VI) for the treatment of MOPs in aquatic environment.

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants.

Occurrence characteristics and health risk assessment of per- and polyfluoroalkyl substances from water in residential areas around fluorine chemical industrial areas, China

Recently, identifying the contamination status and assessing the health risk of per- and polyfluoroalkyl substances (PFASs) in surface water and groundwater have been of great significance. Eighteen individual PFASs were analyzed in thirty-three surface/groundwater samples during one period in a fluorine chemical park (Park A) and during two periods in Park B. The mean total concentration of 18 PFASs (∑PFASs) in Park A (9104.63 ng·L^-1) was significantly higher than that in the wet season (WS) (801.68 ng·L^-1) or DS (714.64 ng·L^-1) in Park B. The perfluorobutane sulfonate (PFBS) was the predominant substance in the two parks, and the maximum concentration in groundwater exceeded 10,000 ng·L^-1. The contamination status in the wet season (WS) was higher than that in the dry season (DS) in Park B. The ∑PFASs in Park A presented an increasing tendency following the groundwater flow direction, whereas this rule was limited to all periods in Park B. Two relative source contributions (RSCs) of 20% or 100% allowed assessing the PFASs risk to different age groups, and the results revealed that some PFASs (4 ≤ C ≤ 7 or 9 ≤ C ≤ 12) were identified as having a low risk quotient (RQ), except for perfluorooctane sulfonate (PFOS) and PFOA (C = 8). The RQ_mix value mainly relies on PFOA and PFOS, with a larger contribution rate of 80-90%. All assessed cases (case 1, case 2, case 3, and case 4) in all age groups revealed that infants were vulnerable to PFASs influence, followed by children, teenagers, and adults.

Human health and ecological risk assessment of 98 pharmaceuticals and personal care products (PPCPs) detected in Indian surface and wastewaters

The release of pharmaceuticals and personal care products (PPCPs) in environmental waters has become an urgent issue due to their pseudo-persistent traits. The present study was undertaken to conduct a screening-level risk assessment of 98 PPCPs, detected in different water matrices (treated wastewater, surface water, and groundwater) of India, for evaluating ecological risk (risk to fish, daphnia, and algae), human health risk, and antimicrobial resistance (AMR) selection risk by following risk quotient (RQ) based methodology. In the present study, 47% of the detected PPCPs in Indian waters were found to exert a possible risk (RQ > 1) to either aquatic species and human health, or cause AMR selection risk. 17 out of 25 antibiotics detected in the environmental waters were found to pose a threat of AMR selection. 11 out of 49 pharmaceuticals were found to exert human health risk from ingesting contaminated surface water, whereas only 2 pharmaceuticals out of 25 were found to exert risk from the intake of groundwater. Very high RQs (>1000) for few pharmaceuticals were obtained, signifying a great potential of the detected PPCPs in causing severe health concern, aquatic toxicity, and AMR spread. Within India, special attention needs to be given to the pharmaceutical hubs, as the environmental waters in these regions were found to be severely contaminated with drug residues resulting in extremely high RQs. The present study will be helpful in prioritizing the detected PPCPs in the environmental waters of India, for which immediate attention and enforceable guidelines are required.

A synthetical methodology for identifying priority pollutants in reclaimed water based on meta-analysis

Wastewater reclamation and reuse is an increasing global project, while the reclamation treatment on wastewater does not completely remove all pollutants in water. The residual pollutants in reclaimed water would cause potential risk on human health and ecosystem safety during the long-term use. It is impossible to analyze and control all pollutants one by one in practice, therefore, identification and control of priority pollutants will be efficient strategy to ensure the safe use of reclaimed water. An integrated three-step methodology for identifying priority pollutants in reclaimed water was proposed in this study. First, a comprehensive literature survey on the occurrence of pollutants in reclaimed water was conducted, and a dataset D_PR for pollutants occurrence in reclaimed water was established, containing 1,113 pollutants. Second, 611 chemicals that had been recommended as hazardous pollutants for various water bodies in previous literatures were summarized, and a dataset D_HP for hazardous pollutants in water was obtained. Third, meta-analysis on these two datasets (D_PR and D_HP) was performed, a new dataset D_HPR for hazardous pollutants in reclaimed water was established, including 265 candidates. Finally, 59 substances out of dataset D_HPR were identified as priority pollutants for reclaimed water based on their recommendation frequency. It is expected that this synthetical methodology will provide powerful support for scientific evaluating and managing water pollution and ensuring safe use of reclaimed water.

Which Micropollutants in Water Environments Deserve More Attention Globally?

Increasing chemical pollution of aquatic environments is a growing concern with global relevance. A large number of organic chemicals are termed as "micropollutants" due to their low concentrations, and long-term exposure to micropollutants may pose considerable risks to aquatic organisms and human health. In recent decades, numerous treatment methods and technologies have been proposed to remove micropollutants in water, and typically several micropollutants were chosen as target pollutants to evaluate removal efficiencies. However, it is often unclear whether their toxicity and occurrence levels and frequencies enable them to contribute significantly to the overall chemical pollution in global aquatic environments. This review intends to answer an important lingering question: Which micropollutants or class of micropollutants deserve more attention globally and should be removed with higher priority? Different risk-based prioritization approaches were used to address this question. The risk quotient (RQ) method was found to be a feasible approach to prioritize micropollutants in a large scale due to its relatively simple assessment procedure and extensive use. A total of 83 prioritization case studies using the RQ method in the past decade were compiled, and 473 compounds that were selected by screening 3466 compounds of three broad classes (pharmaceuticals and personal care products (PPCPs), pesticides, and industrial chemicals) were found to have risks (RQ > 0.01). To determine the micropollutants of global importance, we propose an overall risk surrogate, that is, the weighted average risk quotient (WARQ). The WARQ integrates the risk intensity and frequency of micropollutants in global aquatic environments to achieve a more comprehensive priority determination. Through metadata analysis, we recommend a ranked list of 53 micropollutants, including 36 PPCPs (e.g., sulfamethoxazole and ibuprofen), seven pesticides (e.g., heptachlor and diazinon), and 10 industrial chemicals (e.g., perfluorooctanesulfonic acid and 4-nonylphenol) for risk management and remediation efforts. One caveat is that the ranked list of global importance does not consider transformation products of micropollutants (including disinfection byproducts) and new forms of pollutants (including antibiotic resistance genes and microplastics), and this list of global importance may not be directly applicable to a specific region or country. Also, it needs mentioning that there might be no best answer toward this question, and hopefully this review can act as a small step toward a better answer.

Trends in global greywater reuse: a bibliometric analysis

The increase in water demand in recent years led to the expansion of research and public policies on the reuse of water, especially greywater (GW). Given the diversity of research in the area, this paper proposes an analysis of the evolution of the area through an objectivity metric. Metadata of 1,524 publications indexed in the Scopus database between 1974 and 2021 were analyzed using the VOSviewer tool, and showed exponential growth in publications from 2013. Six different spelling variations were found for GW in the database. Despite the highly geographical scattering of academic production, developed countries, who began researching greywater earlier, had more connections and published more papers; except for Israel, which had the highest average of citations per article. While developed countries lead the research area, developing countries are emerging in GW reuse research. These aspects reveal both the dispersion of the research structure development and a trend of intellectual production in GW from developed to developing countries. Also, we noted that countries suffering from water scarcity stood out with the highest activity in paper publishing. Thus, we expect that future research on GW reuse will take place in developing countries that face water scarcity.

Assessing the risk from trace organic contaminants released via greywater irrigation to the aquatic environment

Onsite non-potable reuse of greywater reduces the energy costs associated with the transport of wastewater and the stress on traditional source waters. However, greywater contains trace organic contaminants (TOrCs) that can be harmful to the aquatic environment when released via irrigation. In this work, the risk associated with TOrCs was evaluated for two potential irrigation scenarios, the use of untreated greywater and the use of greywater treated via conventional activated sludge. Risk quotient (RQ) ratios were calculated using the maximum concentration of each compound in the untreated or treated greywater divided by the relevant aquatic predicted no effect concentration. The TOrCs with RQs > 0.1 or 1 were classified as moderate and high priority, respectively. A review of greywater literature showed that a total of 350 compounds have been detected, with 132 classified as moderate or high priority in untreated greywater. Post-treatment 44 TOrCs remained as high priority due to high concentrations in greywater and/or poor removal during treatment, but only 14 of them were detected in multiple geographic locations. The final list of 14 TOrCs includes plasticizers/flame retardants (di-(2-ethylhexyl) phthalate, bisphenol A, and triphenyl phosphate), surfactants/preservatives/fragrances (4-nonylphenol, benzyldimethyl dodecylammonium chloride, tonalide, methylparaben, and 2-6-di-tert-butyl-4-methylphenol), UV-filters (benzophenone-3 and octocrylene), and pharmaceuticals/antibiotics (acetaminophen, trimethoprim, caffeine, and triclosan). This subset of TOrCs would be useful surrogates to monitor during greywater treatment for irrigation as potential hazards for nearby aquatic environments.

Photocatalytic Removal of Pharmaceuticals from Greywater

High concentrations of pharmaceuticals have been detected in greywater effluents treated using up-to-date technologies. Finding a suitable additional treatment before this effluent is reused is urgently needed to ensure the reused water meets quality standards. This paper reports the use of heterogeneous photocatalysis on anatase and rutile nanopowders to remove naproxen, metformin and sulfamethoxazole, at practically relevant concentrations found in membrane bioreactor (MBR)-treated greywater. A low anatase concentration of 400 mg L−1 was sufficient to efficiently degrade the pharmaceuticals listed above, with complete degradation observed in 5 h. The effect of background species presented in greywater was, to some extent, comparable to that of the OH-radical scavenger. These results prove that photocatalysis using anatase TiO2 is a feasible additional treatment for greywater recycling.

Mitigation of emerging pollutants and pathogens in decentralized wastewater treatment processes: A review

Emerging pollutants (such as micropollutants, microplastics) and pathogens present in wastewater are of rising concern because their release can affect the natural environment and drinking water resources. In this decade, with increasing numbers of small-scale decentralized wastewater systems globally, the status of emerging pollutant and pathogen mitigation in the decentralized wastewater treatment processes has received more attention. This state-of-the-art review aims to discuss the mitigation efficiencies and mechanisms of micropollutants, microplastics, and pathogens in single-stage and hybrid decentralized wastewater treatment processes. The reviewed results revealed that hybrid wastewater treatment facilities could display better performance compared to stand-alone facilities. This is because the multiple treatment steps could offer various microenvironments, allowing incorporating several mitigation mechanisms (such as sorption, degradation, filtration, etc.) to remove complicated emerging pollutants and pathogens. The factors (such as system operation conditions, environmental conditions, wastewater matrix) influencing the removals of emerging pollutants from wastewater in these systems have been further identified. Nevertheless, it was found that very limited research work focused on synergised or conflicted effects of operation conditions on various emerging pollutants naturally present in the wastewater. Meanwhile, effective, reliable, and rapid analysis of the emerging pollutants and pathogens in the complicated wastewater matrix is still a major challenge.

Machine learning approaches for predicting the performance of stormwater biofilters in heavy metal removal and risk mitigation

The increasing amount of data on biofilter treatment performance over the past decade has made it possible to use data-driven approaches to explore the relationships between biofilter performance and a range of input variables. The knowledge gap lies in lack of models to predict the biofilter performance considering both design and operational variables, especially for heavy metals. In this study, we tested three machine learning (ML) approaches, namely multilinear regression (MLR), artificial neural network (NN), and random forest (RF), to predict biofilter outflow concentrations of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb and Zn) using a range of design and operational factors as input variables. The results show that RF performed relatively better than other two models, with median Nash-Sutcliffe Efficiency (NSE) values of 0.995, 0.317, 0.762, 0.636, 0.726, 0.896 and 0.656 for Cd, Cr, Cu, Fe, Ni, Pb and Zn, respectively during model training. However, all the models were less accurate during model validation, with the better performance found for Cd (average NSE=0.964), Zn (0.530) and Ni (0.393) and poorer performance observed for Cu (0.219), Pb (0.058), Fe (-0.054) and Cr (-0.062). Infiltration rate (IR) and inflow concentration (C_in) were sensitive to all pollutants' removal in biofilters. The ratio of system size to catchment size was also found to be important for Zn, Ni and Cd, while ponding depth was an important variable for Cd. Based on thousands of hypothetical design and operational scenarios (generated using raw data), the best ML models were used to predict the biofilter outflow concentrations and estimate the risk quotient (RQ) values with regards to reuse of treated stormwater for various purposes. Results suggest that biofilters were able to reduce health risks associated with heavy metals in stormwater and therefore produce reliable water fit for reuses such as irrigation, swimming, and toilet flushing. Modelling results showed that biofiltration did not meet the requirements for drinking when Cd contamination exists. Explorative analysis also demonstrated how the key operational and design variables can be optimised to further reduce the health risks that can be fit for drinking purposes (i.e., RQ value <1).

Emission of (chlorinated) reclaimed water into a Mediterranean River and its related effects to the dissolved organic matter fingerprint

High resolution mass spectrometry (HRMS) was used to investigate the dissolved organic matter (DOM) profile of a reclamation water trial performed in the Llobregat River (Spain) during summer 2019. 23 water samples (including tertiary effluents, surface river and drinking water), taken during five sampling campaigns, were analyzed and their van Krevelen diagrams were compared. The reclaimed water fingerprint was substantially different from the natural profile of the river, showing a higher number of heteroatomic signals (i.e. CHON, CHOS and CHONS) and the presence of high-intensity S-containing features. As a result, reclaimed water discharge introduced substantial changes in the signature of the lignin-like and soot-like compositional-spaces of the river DOM fingerprint. However, the effect on the drinking water fingerprint was, ultimately, very limited. Only a limited number of features (up to 34) were detected as exclusively emitted with the reclaimed water. During the second phase of the trial, the tertiary effluent was chlorinated for disinfection purposes. This process triggered the unexpected formation of a myriad of new features along the Llobregat River. Notably, 109 brominated/chlorinated features were detected, probably generated as a consequence of the photochemical decay of the emitted chloramines and their free-radical reaction with DOM, and three of them persisted in the final drinking water. The formation of halogenated species in situ in the Llobregat River entails uncertainty at ecological and water treatment levels and should be studied carefully to fully disclose the risks associated to wastewater effluent disinfection.

Microbiological Health Risk Assessment of Water Conservation Strategies: A Case Study in Amsterdam

The aim of this study was to assess the health risks that may arise from the implementation of greywater reuse and rainwater harvesting for household use, especially for toilet flushing. In addition, the risk of cross connections between these systems and the drinking water system was considered. Quantitative microbial risk assessment (QMRA) is a method that uses mathematical modelling to estimate the risk of infection when exposure to pathogens happens and was used in this study to assess the health risks. The results showed that using rainwater without prior treatment for toilet flushing poses an annual infection risk from L. pneumophila at 0.64 per-person-per-year (pppy) which exceeds the Dutch standard of 10-4 pppy. The use of untreated greywater showed a risk that is below the standard. However, treatment is recommended due to the ability of P. aeruginosa to grow in the reuse system. Moreover, showering and drinking with cross-connected water has a high annual infection risk that exceeds the standard due to contact with Staphylococcus aureus and E. coli O157:H7. Several measures can be implemented to mitigate the risks such as treating the greywater and rainwater with a minimum of 5-log removal, closing the toilet lid while flushing, good design of greywater and rainwater collection systems, and rigorous plumbing installation procedures.

17β-Estradiol removal routes by moving bed biofilm reactors (MBBRs) under various C/N ratios

This study evaluated the contribution of biotic and abiotic routes to the 17β-estradiol (E2) removal in moving bed biofilm reactors (MBBRs), and uncovered the interrelation between the E2 removal routes and biofilm characteristics, which was not researched in previous literature. Three MBBRs with different C/N ratios (0 for C/N₀; 2 for C/N₂; and 5 for C/N₅) were operated in continuous mode. A 65-day degradation demonstrated that the MBBRs had high potential to remove E2 regardless of the C/N (E2 removal greater than 99% for all MBBRs; P > 0.05). Further batch tests showed that the E2 removal mainly resulted from heterotrophic activities for all MBBRs, accounting for approximately 85% for all MBBRs (P > 0.05), followed by nitrification (10-11%) and adsorption (4-5%). Importantly, lower adhesive force likely led to higher E2 adsorption onto biofilms. Besides, enhanced ammonia oxidizing rate (AOR) was consistent with the high contribution of nitrification to the E2 attenuation. Importantly, heterotrophic activity was positively correlated with its contribution to E2 removal (r = 0.99, P < 0.05). To sum, the results obtained in this study helped to understand the E2 removal routes in nitrifying biofilm systems.

Optimization and economical study of electro-coagulation unit using CCD to treat real graywater and its reuse potential

The reclamation of graywater for non-potable purposes has attained utmost importance, particularly in developing nations. The present research aimed to evaluate the optimal condition of electro-coagulation system in treatment of graywater and its reuse. Moreover, the study also evaluates the impact of major operating parameters on pollutant removal and anode dissolution. To achieve this, two-factor (voltage potential and time) and 5-level (- 1, - 0.5, 0, + 0.5, and + 1) full factorial design, based on response surface methodology (RSM) has been executed for the actual design. The data were acquired after conducting 20 experiments, as suggested by RSM (response surface methodology). Design Expert 12.0.8.0 software has been used to design mathematical model to obtain optimum condition (14 V and 47 min) at pH of 7.35, which provides experimental removal efficiency (75.6% chemical oxygen demand, 78.7% total dissolved solids, 93.4% turbidity, and 63.2% chloride) with minimal electrode consumption of 1.38 mg L^-1. Adequacy of the model developed has been verified by ANOVA. The operating cost of treating graywater at the optimized condition obtained as 0.7 US$/kg COD.

Characterization of segregated greywater from Indian households-part B: emerging contaminants

Emerging contaminants (ECs) have become an increasing area of concern due to the likely impacts of these compounds on human health and the environment. Generally, products which are used for households and personal care activities contribute to major percentage of ECs in household greywater. Not much information on the presence of xenobiotic organic compounds in greywater is currently available. Therefore, the present study focused on the qualitative and quantitative analyses of emerging contaminants from different classifications of Indian households. The qualitative screening of emerging pollutants by solid-phase extraction-gas chromatography and mass spectroscopy (SPE-GC-MS) showed the presence of 78 different emerging contaminants from three different sources, which are categorized into ten different groups based on their chemical properties. The quantitative analysis of few selected target pollutants such as phthalic esters, namely diethyl hexyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, triclosan, bisphenol A, caffeine, acetaminophen, 3-methyl salicylic acid, 4-octylphenol, and 4-nonylphenol were found to be 0.38 ± 0.39 μg/L, 1.57 ± 1.54 μg/L, 4.77 ± 2.57 μg/L, 0.712 ± 0.17 μg/L, 5.82 ± 1.85 μg/L, 11.08 ± 2.64 μg/L, 2.30 ± 1.19 μg/L 13.18 ± 4.48 μg/L, 3.75 ± 1.90 μg/L, 4.95 ± 2.21 μg/L, and 5.96 μg/L, respectively. Risk assessment indicated that 63 compounds identified in the greywater can be considered priority pollutants. Based on the results obtained in the present study, effective zero-discharge liquid system can be designed for different sources of greywater and it can be recycled and reused without much risk. Graphical abstract .

Risk assessment of PFASs in drinking water using a probabilistic risk quotient methodology

We evaluated health risks associated with perfluorinated and polyfluorinated alkyl substances (PFASs) found in drinking water applying human risk assessment (HRA) methodology. Using data on worldwide occurrence of PFASs in drinking water and recent guidelines for PFASs in drinking water, we applied four scenarios based on different toxicological threshold values to calculate age-dependent risk quotients (RQ) for different PFASs. The mean concentrations of the most frequently detected compounds (PFOS and PFOA) were highest in North America (99.2 and 30.7 ng L^-1, respectively), and lowest in Asia (PFOS: 3.0 ng L^-1) and Europe (PFOA: 4.87 ng L^-1). Using HRA methodology and maximum reported concentrations, only PFOS and PFOA, examined individually, showed any threat to human health. Specifically, calculations with the average and maximum concentrations of PFOS showed RQ values higher than 0.2 or 1, respectively, for some age groups under specific scenarios. Similarly, using maximum PFOA concentrations, a RQ equal to 0.2 for infants up to 3 months was calculated under scenario 4. Regional differences on RQ values were observed when PFOS concentrations from Europe, North America and Asia were used. Estimation of the human health risk due to mixtures of PFASs using average concentrations showed that the RQ_mix was higher than 0.2 for infants up to 3 months (scenario 3) and infants and children up to 6 years old (scenario 4). More importantly, evaluation of the guideline values set by the EU and the Health Advisory Levels issued by the USEPA resulted (under some scenarios) in RQ values higher than 0.2 for PFOS and PFOA for specific age groups, indicating that further discussion is needed for the monitoring and prioritization of these compounds.

A review of nature-based solutions for greywater treatment: Applications, hydraulic design, and environmental benefits

Recognizing greywater as a relevant secondary source of water and nutrients represents an important chance for the sustainable management of water resource. In the last two decades, many studies analysed the environmental, economic, and energetic benefits of the reuse of greywater treated by nature-based solutions (NBS). This work reviews existing case studies of traditional constructed wetlands and new integrated technologies (e.g., green roofs and green walls) for greywater treatment and reuse, with a specific focus on their treatment performance as a function of hydraulic operating parameters. The aim of this work is to understand if the application of NBS can represent a valid alternative to conventional treatment technologies, providing quantitative indications for their design. Specifically, indications concerning threshold values of hydraulic design parameters to guarantee high removal performance are suggested. Finally, the existing literature on life cycle analysis of NBS for greywater treatment has been examined, confirming the provided environmental benefits.

Experimental and in silico assessment of fate and effects of the UV filter 2-phenylbenzimidazole 5-sulfonic acid and its phototransformation products in aquatic solutions

Often ingredients of personal care products are present in treated wastewaters, e. g grey water (GW), and are discharged into aquatic systems. Conventional treatment of GW does not fully eliminate micropollutants such as the UV filter substance 2-phenylbenzimidazole-5-sulfonic acid (PBSA). Photolysis has been proposed as an alternative treatment method for other micropollutants, but it is not clear yet whether it can also be used to eliminate PBSA. One goal of this study was to better understand the basic pathways involved in this process. It aimed to identify photo-transformation products (PTPs) by using, in the test conditions, an initial concentration of PBSA higher than those expected in the environment. The photolysis experiments were carried out using Xenon and UV lamps. Under Xenon irradiation only slight primary elimination was found. UV irradiation resulted in almost complete primary elimination of PBSA but not in full mineralization. Four isomeric mono-hydroxylated PTPs were identified by high resolution mass spectrometry (HRMS) which could be confirmed by other studies. A modified luminescent bacteria test (LBT) with Vibrio fischeri was employed to assess acute and chronic toxic effects of the irradiated photolytic mixtures. A strong correlation was found between the kinetics of two of the PTPs and luminescence inhibition indicating bacterial toxicity. Using a set of in silico quantitative structure-activity relationship (QSAR) models, this study also offered new insights concerning the environmental fate and toxicity of the TPs of PBSA as the TPs generated by UV-treatment are more persistent and partly more toxic than PBSA.

Interaction between 17β-estradiol degradation and nitrification in mariculture wastewater by Nitrosomonas europaea and MBBR

This study investigated the relation between 17β-estradiol (E2) degradation and nitrification in synthetic mariculture wastewater by ammonia oxidizing bacterium Nitrosomonas europaea and moving bed biofilm reactor (MBBR). Batch experiments showed that E2 degradation by N. europaea in wastewater followed zero-order reaction kinetics (r² = 0.944, 4.07 μg/ L h^-1) when ammonia presented. Nitrite yield in N. europaea inoculation decreased by 77.8% exposed to 1 mg/L E2. The inhibitory impact on ammonia oxidation was enhanced with increasing E2 dosage from 50 ng/L to 1 mg/L. Notably, E2 as low as 50 ng/L still had significant interference with nitrite production, bacterial density and ammonia monooxygenase (AMO) activity of N. europaea. Still, the following continuous 68-day degradation test revealed that 84.5%-98.7% E2 could be removed by a bench-scale MBBR. Whereas, ammonia removal remarkably decreased from 94.7% ± 2.1% to 85.6% ± 2.1% (p < .05) along with the enhanced E2 removal (from 84.5% ± 2.0% to 98.7% ± 0.4%, p < .05) when inlet E2 increased from 10 μg/L to 1 mg/L, indicating the great role of heterotrophs in E2 degradation. In contrast, nitrite oxidation was not affected upon E2 exposure irrespective of E2 concentrations. In summary, nitrification was effective in removing E2, while E2 interfered with ammoxidation process, but this interference was negligible at the reactor level given the low level of E2 in practical field conditions.

Thermal baths as sources of pharmaceutical and illicit drug contamination

Despite the fact that there are tens of thousands of thermal baths in existence, knowledge about the occurrence of pharmaceutically active compounds (PhACs) in untreated thermal wastewater is very limited. Because used thermal water is typically legally discharged into surface waters without any treatment, the effluent poses environmental risks for the receiving water bodies. The aim of this study was to show the occurrence patterns and spatiotemporal characteristics of 111 PhACs in thermal wastewater. Six thermal water outflows of different thermal baths were tested in different seasons in the Budapest metropolitan region (Hungary), and diurnal analysis was performed. After solid-phase extraction, the samples were analysed and quantified by coupling supercritical fluid chromatography and mass spectrometry to perform simultaneous multi-residue drug analysis. The results confirm that water discharge pipes directly transport pharmaceuticals into surface water bodies; 34 PhACs were measured to be over the limit of quantification at least once, and 21 of them were found in more than one water sample. The local anaesthetic drug lidocaine, antiepileptic carbamazepine, analgesic derivative tramadol and illicit drug cocaine were detected in more than half of the samples. Caffeine, metoprolol and bisoprolol (cardiovascular drugs), benzoylecgonine (cocaine metabolite), diclofenac (NSAID), citalopram (antidepressant) and certain types of hormones also have a significant frequency of 30-50%. However, the occurrence and concentrations of PhACs vary according to the season and number/types of visitors. As demonstrated by the diurnal fluctuation, drug contamination of thermal waters can significantly vary, even for similar types of baths; furthermore, the quantity and types of some pollutants rapidly change in the discharged thermal wastewater.

Suspect screening analysis of the occurrence and removal of micropollutants by GC-QTOF MS during wastewater treatment processes

The presence of micropollutants in wastewater treatment plant (WWTP) poses potential risks to the aquatic system and human health. This study comprehensively characterized the presence, elimination, and transformation of micropollutants in the WWTP using the suspect screening approaches by employing the gas chromatography coupled with quadrupole time-of-flight mass spectrometry. Overall, 5724 features were identified in influent, while only 3418 features existed in effluents. Hierarchical cluster analysis (HCA) was used to group features based on intensity profiles to investigate the behavior and fate of detected features. Four representative trends were defined with the corresponding features. Among 117 compounds identified during the treatment process, there were 99 compounds in influent, 10 biological transformation products (TPs), 3 ozone TPs, and 5 ultraviolet TPs. Furthermore, the removal efficiencies for the detected compounds were determined. The study findings highlight the importance of the removal of emerging pollutants and TPs such as fipronil, fipronil sulfide, and fipronil sulfone.

Membrane-based technology in greywater reclamation: A review

Greywater reclamation has been well recognized as an alternative water resource for non-potable or potable use. To meet greywater reuse standards, various membrane-based techniques have been widely adopted to treat greywater for producing water with superior quality. This paper aims to present a comprehensive review on membrane-based techniques in greywater treatment, including direct pressure-driven and osmotic-driven membrane processes, hybrid membrane processes (such as membrane bioreactors and integrating membrane separation with other processes), and resource recovery oriented membrane-based processes. Membrane performance and treatment efficiency in the reported membrane-based greywater treatment systems are evaluated and membrane fouling mechanisms and control strategies are illustrated. The advantages, limitations, and influencing factors on membrane-based greywater treatment processes are highlighted. Towards long-term sustainability of greywater reclamation, the challenges and prospects of membrane-based greywater treatment are discussed.

Greywater recycling in buildings using living walls and green roofs: A review of the applicability and challenges

Living walls and green roofs offer numerous benefits to densely populated urban areas such as cooling, air filtering and improved aesthetics. However, plants in these two systems are high water consumers making such systems particularly unsuitable for water-scarce arid environments most at need of passive cooling and urban greening. Integrated greywater treatment in these structures provides a possible solution, providing plants not only with water but other required nutrients and organics. However, greywater treatment by living wall and green roof systems is still lacking. This review summarizes the few studies exploring this new integrated technology and provides an in-depth analysis of existing literature on vegetated building structures and greywater treatment to reveal benefits and potential pitfalls of this technology. Appropriate selection of plants and media are essential to successful system design and must meet competing demands compared to those used in existing vegetated building structures for cooling/greening and constructed wetlands for greywater treatment. A variety of operational and user-interaction issues are also explored and will be key areas of future research to enable full-scale implementation. Integrated greywater treatment using green building vegetated structures appears a promising method for dual purpose water recycling and urban cooling, and various future research needs are emphasized to realize this.

Toxicological risk assessment and prioritization of drinking water relevant contaminants of emerging concern

Toxicological risk assessment of contaminants of emerging concern (CEC) in (sources of) drinking water is required to identify potential health risks and prioritize chemicals for abatement or monitoring. In such assessments, concentrations of chemicals in drinking water or sources are compared to either (i) health-based (statutory) drinking water guideline values, (ii) provisional guideline values based on recent toxicity data in absence of drinking water guidelines, or (iii) generic drinking water target values in absence of toxicity data. Here, we performed a toxicological risk assessment for 163 CEC that were selected as relevant for drinking water. This relevance was based on their presence in drinking water and/or groundwater and surface water sources in downstream parts of the Rhine and Meuse, in combination with concentration levels and physicochemical properties. Statutory and provisional drinking water guideline values could be derived from publically available toxicological information for 142 of the CEC. Based on measured concentrations it was concluded that the majority of substances do not occur in concentrations which individually pose an appreciable human health risk. A health concern could however not be excluded for vinylchloride, trichloroethene, bromodichloromethane, aniline, phenol, 2-chlorobenzenamine, mevinphos, 1,4-dioxane, and nitrolotriacetic acid. For part of the selected substances, toxicological risk assessment for drinking water could not be performed since either toxicity data (hazard) or drinking water concentrations (exposure) were lacking. In absence of toxicity data, the Threshold of Toxicological Concern (TTC) approach can be applied for screening level risk assessment. The toxicological information on the selected substances was used to evaluate whether drinking water target values based on existing TTC levels are sufficiently protective for drinking water relevant CEC. Generic drinking water target levels of 37 μg/L for Cramer class I substances and 4 μg/L for Cramer class III substances in drinking water were derived based on these CEC. These levels are in line with previously reported generic drinking water target levels based on original TTC values and are shown to be protective for health effects of the majority of contaminants of emerging concern evaluated in the present study. Since the human health impact of many chemicals appearing in the water cycle has been studied insufficiently, generic drinking water target levels are useful for early warning and prioritization of CEC with unknown toxicity in drinking water and its sources for future monitoring.

Quantitative microbial risk assessment of Greywater on-site reuse

Recycle domestic greywater for on-site non-potable uses can lessen the demand on potable water and the burden on wastewater treatment plants. However, lack of studies to assess health risk associated with such practices has hindered their popularity. A Quantitative Microbial Risk Assessment was conducted to estimate the public health risks for two greywater reuse scenarios: toilet flushing and food-crop irrigation. Household greywater quality from three sources (bathroom, laundry and kitchen) was analyzed. Mathematical exposure rates of different scenarios were established based on human behavior using Monte-Carlo simulation. The results showed that, greywater from all three household sources could be safely used for toilet flushing after a simple treatment of microfiltration. The median range of annual infection risk was 8.8 × 10-15-8.3 × 10-11 per-person-per-year (pppy); and the median range of disease burden was 7.6 × 10-19-7.3 × 10-15 disability-adjusted life years (DALYs) pppy. In food-crop irrigation scenario, the annual infection risks and disease burdens of treated greywater from bathroom and laundry (2.8 × 10-8, 4.9 × 10-8 pppy; 2.3 × 10-12-4.2 × 10-12 DALYs pppy) were within the acceptable levels of U.S. EPA annual infection risk (≤10-4 pppy) and WHO disease burden (≤10-6 DALYs pppy) benchmarks, while kitchen greywater was not suitable for food-crop irrigation (4.9 × 10-6 pppy; 4.3 × 10-10 DALYs pppy) based on these benchmarks. The model uncertainties were discussed, which suggests that a more accurate risk estimation requires improvements on data collection and model refinement.

Design and evaluation of a compact photocatalytic reactor for water treatment

A compact reactor for photocatalytic oxidation and photocatalytic ozonation water treatment was developed and evaluated by using four model pollutants. Additionally, combinations of pollutants were evaluated. Specially produced Al₂O₃ porous reticulated monolith foams served as TiO₂ carriers, offering a high surface area support. UV lamps were placed in the interior to achieve reduced dimensions of the reactor (12 cm in diameter × 20 cm in height). Despite its small size, the overall photocatalytic cleaning capacity was substantial. It was evaluated by measuring the degradation of LAS + PBIS and RB19 as representatives of surfactants and textile dyes, respectively. These contaminants are commonly found in household grey wastewater with phenol as a trace contaminant. Three different commercial photocatalysts and one mixture of photocatalysts (P25, P90, PC500 and P25 + PC500) were introduced in the sol-gel processing and immobilized on foamed Al₂O₃ monoliths. RB19 and phenol were easily degradable, while LAS and PBIS were more resistant. The experiments were conducted at neutral-acidic pH because alkaline pH negatively influences both photocatalyic ozonation (PCOZ) and photocatalysis. The synergistic effect of PCOZ was generally much more expressed in mineralization reactions. Total organic carbon TOC half lives were in the range of between 13 and 43 min in the case of individual pollutants in double-deionized water. However, for the mixed pollutants in tap water, the TOC half-life only increased to 53 min with the most efficient catalyst (P90). In comparison to photocatalysis, the PCOZ process is more suitable for treating wastewater with a high loading of organic pollutants due to its higher cleaning capacity. Therefore, PCOZ may prove more effective in industrial applications.

Advanced oxidation and disinfection processes for onsite net-zero greywater reuse: A review

Net-zero greywater (NZGW) reuse, or nearly closed-loop recycle of greywater for all original uses, can recover both water and its attendant hot-water thermal energy, while avoiding the installation and maintenance of a separate greywater sewer in residential areas. Such a system, if portable, could also provide wash water for remote emergency health care units. However, such greywater reuse engenders human contact with the recycled water, and hence superior treatment. The purpose of this paper is to review processes applicable to the mineralization of organics, including control of oxidative byproducts such as bromate, and maintenance of disinfection consistent with potable reuse guidelines, in NZGW systems. Specifically, TiO₂-UV, UV-hydrogen peroxide, hydrogen peroxide-ozone, ozone-UV advanced oxidation processes, and UV, ozone, hydrogen peroxide, filtration, and chlorine disinfection processes were reviewed for performance, energy demand, environmental impact, and operational simplicity. Based on the literature reviewed, peroxone is the most energy-efficient process for organics mineralization. However, in portable applications where delivery of chemicals to the site is a concern, the UV-ozone process appears promising, at higher energy demand. In either case, reverse osmosis, nanofiltration, or ED may be useful in controlling the bromide precursor in make-up water, and a minor side-stream of ozone may be used to prevent microbial regrowth in the treated water. Where energy is not paramount, UV-hydrogen peroxide and UV-TiO₂ can be used to mineralize organics while avoiding bromate formation, but may require a secondary process to prevent microbial regrowth. Chlorine and ozone may be useful for maintenance of disinfection residual.

Sorption and biodegradation of propylparaben in greywater by aerobic attached-growth biomass

Greywater (GW) is becoming an important alternative water source for non-potable purposes, but requires treatment to remove contaminants, including micropollutants that in GW mainly originate from personal care products. Biofilters are commonly used for onsite GW treatment, but there are still significant knowledge gaps regarding their ability and mechanism of micropollutants removal. This study investigates the removal of propylparaben (PPB) by aerobic attached-growth biomass, quantifying the kinetics and the interplay between sorption and biodegradation. The ability of biomass, collected from a pilot scale biofilter treating real GW, to eliminate PPB from both synthetic greywater (SGW) and deionized (DI) water was studied in laboratory batch experiments. Elimination of PPB was found to proceed via sorption to biomass followed by biodegradation. Sorption of PPB by biomass in SGW and in DI water exhibited similar kinetics, fitting Langmuir isotherm with the maximum adsorbed amount of 9.8mg_PPB g_biomass^-1. PPB biodegradation exhibited first-order kinetics in both SGW and DI water, with a 30h lag-phase in SGW and no lag-phase in DI water. This difference is attributed to presence of readily-biodegradable organic matter in the SGW. Actual PPB degradation rate in both cases (excluding the lag phase in SGW) was very similar, 62mg_PPB g_biomass^-1d^-1, yielding almost full mineralization. These findings show the relative contribution of the major processes involved in PPB elimination by biofilters and can be applied for designing GW treatment units.

Greywater characterization and handling practices among urban households in Ghana: the case of three communities in Kumasi Metropolis

Greywater management in Ghana receives little or no attention although untreated greywater is associated with environmental and public health risks. This paper assesses greywater characteristics and handling practices among urban households in three selected communities in Kumasi, the second largest city of Ghana. The study involved in-depth surveys (interviews and observations) with 90 households, and collection of 18 greywater samples from nine greywater sources for laboratory analysis. Average greywater generation is 43.36 ± 17 litres per capita per day, equivalent to 36% of average water consumption. Greywater is untreated before disposal (≈99%), and disposal is mainly (89%) into drains and onto streets. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) levels are high but give very low BOD/COD ratios (0.20 ± 0.07) indicating a very low biodegradability potential. Nutrient levels are high: 12 times (P) and 30 times (N) in excess of standard discharge limits. Other contaminants detected are heavy metals (Fe, Pb, Zn and Cd), microbes (total coliforms, Escherichia coli and Salmonella spp.), and organic micropollutants - benzalkonium chloride, parabens (methyl and propyl), sodium benzoate and hypochlorite - and details of the levels are discussed in the paper. Greywater reuse could be useful for biomass production, but it also presents a challenge and threat to natural biological processes and water sources.

Greywater treatment by granular filtration system using volcanic tuff and gravel media

The main objective of this study was to evaluate the efficiency of a granular filtration system (GFS) in greywater treatment under arid and semi-arid conditions. Six GFSs were designed, constructed, and monitored for approximately 13 months. Each GFS served a single rural Jordanian home by treating their greywater. Volcanic tuff media were used as the filtration media in three of the GFSs while the remaining three GFSs used gravel media. Results show that the biological oxygen demand, chemical oxygen demand, and total suspended solids of the effluent were significantly lower as compared to the influent and demonstrated a removal efficiency of 73%, 65%, and 85%, respectively, when using volcanic tuff media. The removal efficiency was 49%, 51%, and 76%, respectively, when using gravel media. There was a significant increase in the electrical conductivity, pH, potassium (K⁺), magnesium (Mg²⁺), chloride (Cl^-), sodium (Na⁺), sulfate (SO₄^2-), bicarbonates (HCO₃^-), sodium adsorption ratio, and exchangeable sodium percentage in the effluents of the GFS that used volcanic tuff media. The study suggests that GFSs can adequately treat greywater under arid conditions. However, gravel media produce less concentrated effluent compared to the volcanic tuff media.

Irrigated greywater in an urban sub-division as a potential source of metals to soil, groundwater and surface water

Increased water demands in dry countries such as Australia, have led to increased adoption of various water reuse practices. Irrigation of greywater (all water discharged from the bathrooms, laundry and kitchen apart from toilet waste) is seen as a potential means of easing water demands; however, there is limited knowledge of how greywater irrigation impacts terrestrial and aquatic environments. This study compared four greywater irrigated residential lots to adjacent non-irrigated lots that acted as controls. Accumulation and potential impacts of metals in soil, groundwater and surface water, as a result of greywater irrigation, were assessed by comparing measured concentrations to national and international guidelines. Greywater increased concentrations of some metals in irrigated soil and resulted in As, B, Cr and Cu exceeding guidelines after only four years of irrigation. Movement of metals from the irrigation areas resulted in metal concentrations in groundwater (Al, As, Cr, Cu, Fe, Mn, Ni and Zn) and surface water (Cu, Fe and Zn) exceeding environmental quality guidelines again within four years. These results are unlikely to be universally applicable but indicate the need to consider metals in greywater in order to minimize potential adverse environmental effects from greywater irrigation.

Screening and health risk of organic micropollutants in rural groundwater of Liaodong Peninsula, China

Groundwater serves as a main drinking water source for rural residents in China. However, little is known regarding the pollution of organic micropollutants in groundwater that may pose health risks. In this study, more than 1300 organic micropollutants were screened in the groundwater samples collected from 13 drinking water wells distributed across five rural regions of Liaodong Peninsula in China. A total of 80 organic micropollutants including 12 polycyclic aromatic hydrocarbons, 11 alkanes, 9 pesticides, 7 substituted phenols, 7 perfluoroalkyl acids, 6 heterocyclic compounds, 5 alcohols, 5 phthalic acid esters, 5 pharmaceutical and personal care products, 3 ketones, 2 polychlorinated biphenyls (PCBs), 2 alkylbenzenes and 2 chlorinated benzenes were detected, with their total concentration of 32-1.5 × 10⁴ ng/L. Noncarcinogenic and carcinogenic risks of a part of pollutants were assessed. Exposure through skin absorption and oral ingestion was considered in the assessment. Generally the risks are within the acceptable limits, except for that the carcinogenic risk at two sites in Jinzhou is higher than 10^-6. To the best of our knowledge, this is the first report on health risks of groundwater micropollutants in China.

UV254 absorbance as real-time monitoring and control parameter for micropollutant removal in advanced wastewater treatment with powdered activated carbon

This study investigates the applicability of UV absorbance measurements at 254 nm (UVA254) to serve as a simple and reliable surrogate parameter to monitor and control the removal of organic micropollutants (OMPs) in advanced wastewater treatment applying powdered activated carbon (PAC). Correlations between OMP removal and corresponding UVA254 reduction were determined in lab-scale adsorption batch tests and successfully applied to a pilot-scale PAC treatment stage to predict OMP removals in aggregate samples with good accuracy. Real-time UVA254 measurements were utilized to evaluate adapted PAC dosing strategies and proved to be effective for online monitoring of OMP removal. Furthermore, active PAC dosing control according to differential UVA254 measurements was implemented and tested. While precise removal predictions based on real-time measurements were not accurate for all OMPs, UVA254-controlled dynamic PAC dosing was capable of achieving stable OMP removals. UVA254 can serve as an effective surrogate parameter for OMP removal in technical PAC applications. Even though the applicability as control parameter to adjust PAC dosing to water quality changes might be limited to applications with fast response between PAC adjustment and adsorptive removal (e.g. direct filtration), UVA254 measurements can also be used to monitor the adsorption efficiency in more complex PAC applications.