Amendment of water quality standards in China: viewpoint on strategic considerations

'Environmental standard limit concentration' arsenic exposure is associated with anxiety, depression, and autism-like changes in early-life stage zebrafish

Arsenic is a worldwide environmental pollutant that can impair human health. Previous studies have identified mental disorders induced by arsenic, but the environmental exposure concentrations in the early life stages associated with these disorders are poorly understood. In the present study, early-life stage zebrafish were used to explore the effects on mental disorders under 'environmental standard limit concentrations' arsenic exposures of 5, 10, 50, 150, and 500 μg/L. The results showed that arsenic exposure at these concentrations changed the locomotor behavior in larval zebrafish and was further associated with anxiety, depression, and autism-like behavior in both larval and juvenile zebrafish. Changes were noted at benchmark dose limit (BMDL) concentrations as low as 0.81 μg/L. Transcriptomics showed that immediate early genes (IEGs) fosab, egr1, egr2a, ier2b, egr3, and jund were decreased after arsenic exposure in larval and juvenile zebrafish. Nervous system impairment and anxiety, depression, and autism-like behaviors in early-life stage zebrafish at 'environmental standard limit concentrations' may be attributed to the downregulation of IEGs. These findings in zebrafish provided new experimental support for an arsenic toxicity threshold for mental disorders, and they suggest that low levels of environmental chemicals may be causative developmental factors for mental disorders.

The organism fate of inland freshwater system under micro-/nano-plastic pollution: A review of past decade

Micro- and nano-plastics (MPs/NPs) are characterized by their small size and extensive surface area, making them global environmental pollutants with adverse effects on organisms at various levels, including organs, cells, and molecules. Freshwater organisms, such as microalgae, emerging plants, zooplankton, benthic species, and fish, experience varying impacts from MPs/NPs, which are prevalent in both terrestrial and aquatic inland environments. MPs/NPs significantly impact plant physiological processes, including photosynthesis, antioxidant response, energy metabolism, and nitrogen removal. Extended exposure and ingestion to MPs/NPs might cause metabolic and behavioral deviations in zooplankton, posing an extinction risk. Upon exposure to MPs/NPs, both benthic organisms and fish display behavioral and metabolic disturbances, due to oxidative stress, neural toxicity, intestinal damage, and metabolic changes. Results from laboratory and field investigations have confirmed that MPs/NPs can be transported across multiple trophic levels. Moreover, MPs/NPs-induced alterations in zooplankton populations can impede energy transfer, leading to food scarcity for filter-feeding fish, larvae of benthic organism and fish, thus jeopardizing aquatic ecosystems. Furthermore, MPs/NPs can harm the nervous systems of aquatic organisms, influencing their feeding patterns, circadian rhythms, and mobility. Such behavioral alterations might also introduce unforeseen ecological risks. This comprehensive review aims to explore the consequences of MPs/NPs on freshwater organisms and their interconnected food webs. The investigation encompasses various aspects, including behavioral changes, alterations in physiology, impacts on metabolism, transgenerational effects, and the disruption of energy transfer within the ecosystem. This review elucidated the physiological and biochemical toxicity of MPs/NPs on freshwater organisms, and the ensuing risks to inland aquatic ecosystems.

Bibliometric analysis of the association between drinking water pollution and bladder cancer

Background

Bladder cancer has become an increasingly intractable health problem worldwide. Long-term drinking water pollution is known to promote its occurrence. This study aimed to analyze the research status, hot spots, and future trends of drinking water pollution and bladder cancer through extensive bibliometric examination to provide reference data for better prevention and management of bladder cancer.

Methods

The Scopus database developed by Elsevier was browsed for articles that met the predefined criteria using the search terms related to drinking water and bladder cancer. Included articles were further evaluated by year of publication, subject category, institution, article type, source journal, authors, co-authorship networks, and text mining of titles by R software packages tm, ggplot2 and VOSviewer software.

Results

In total, 687 articles were selected after a comprehensive literature search by the Scopus database, including 491 research articles, 98 review articles, 26 conference papers, 23 letters and 49 other documents. The total number of articles published showed an upward trend. The United States has the largest number of published articles (345 articles), institutions (7/10) and funding sponsors (top 5). The journal with the most publications was Environmental Health Perspectives, with 46 published. The highest number of citations up to 2330 times for a single article published in 2007 on the journal of Mutation Research. Professor Cantor K.P. was the highest number of publications with 35 articles and Smith A.H. was the most cited author with the number of citations reaching 6987 times overall and 225 times per article. The most frequent keywords excluding the search subject were "arsenic", "chlorination", "trihalomethane", and "disease agents".

Conclusion

This study is the first systematic bibliometric study of the literature publications on drinking water pollution and bladder cancer. It offers an overall and intuitive understanding of this topic in the past few years, and points out a clear direction research hotspots and reveals the trends for further in-depth study in future.

Ecological risk characteristics of sediment-bound heavy metals in large shallow lakes for aquatic organisms: The case of Taihu Lake, China

Heavy metal contamination in the surface sediments of large shallow lakes in China is becoming increasingly serious. However, more attention has been paid to the human health risk of heavy metals in the past, while little consideration has been given to aquatic organisms. Taking Taihu Lake as an example, we explored the spatial and temporal heterogeneity of the potential ecological risks of seven heavy metals (Cd, As, Cu, Pb, Cr, Ni, and Zn) to species at different taxonomic scales using an improved species sensitivity distribution (SSD) method. The results showed that all six heavy metals, except Cr, were exceeded to some extent compared to background levels, with Cd being the most severe exceedance. Based on the hazardous concentration for 5% of the species (HC₅), Cd had the lowest HC₅ value, implying the highest ecological risk of toxicity. Ni and Pb had the highest HC₅ values and the lowest risk. Cu, Cr, As and Zn were at a relatively moderate levels. For the different groups of aquatic organisms, the ecological risk of most heavy metals was generally lower for vertebrates than for the whole species. The risk for invertebrates and algae was higher than that for all species. Zn and Cu had the highest potentially affected fractions (PAFs) for all classification cases, with mean PAFs of 30.25% and 47.2%, respectively. Spatially, the high ecological risk of sediment heavy metals was significantly related to the spatial characteristics of the type and intensity of human activities in the catchment. Administratively, the environmental quality standards for freshwater sediments proposed by America and Canada are insufficient to protected against the ecological risks of heavy metals in Taihu Lake. In the absence of such standards, China urgently needs to establish an approptiate system of environmental quality standards for heavy metals in lake sediments.

Elemental composition and microbial community differences between wastewater treatment plant effluent and local natural surface water: A Zhengzhou city study

Wastewater treatment plant (WWTP) effluent is discharged into rivers as supplemental water, which may result in ecological risk. This study compares the element composition and microbial community of WWTP effluent and natural surface water (NSW) and reveals the potential ecological risk of WWTP effluent discharge. Twenty recently upgraded WWTPs and three relatively large reservoirs in Zhengzhou city, China, were selected. The contents of N, P, S, K, Ca, Mg, B, Si, Na, Fe, Mn, Co, Ni and Sn were significantly higher in WWTP effluent than in NSW, while those of Mo, V, Pb and Cd were significantly lower. There was no significant difference between WWTP effluent and NSW in terms of the element imbalance index (IMI) (representing the extent of imbalance of element proportions) relative to the class IV surface water quality standard (the control standard for most Chinese rivers). The macronutrient IMI relative to the Hoagland formula was significantly lower in WWTP effluent than in NSW, and WWTP effluent discharge could significantly lower this index in NSW; this may be an important cause of primary productivity explosion. The microbial diversity was significantly higher in WWTP effluent than in NSW. The predicted relative abundances of mobile genetic elements and oxidative-stress-tolerant phenotypes were significantly higher in WWTP effluent than in NSW, whereas the abundance of gram-negative phenotypes was significantly lower, and that of potential pathogenic phenotypes was slightly lower. The effluent from upgraded WWTPs exhibited a low risk of pathogen diffusion but a high risk of antibiotic resistance gene diffusion. The element composition and microbial community should be considered when evaluating the ecological risk of WWTP effluent discharge.

Copula-based framework for integrated evaluation of water quality and quantity: A case study of Yihe River, China

Water quantity and quality are two key factors affecting the performance of integrated watershed management. Conventional water resources assessment of rivers often deals with water quantity and quality separately. However, how to make an objective and impartial assessment of water resources by incorporating both water quantity and quality remains unclear, especially in watersheds with significant human activity impacts and high spatiotemporal variations in flows. In such areas, the nonmonotonic relationship between the water quality and discharge rate of a river, in contrast to near-natural conditions, is often ignored. To resolve this problem, this paper develops a new framework for the integrated evaluation of water quantity and quality by incorporating a new index, namely, the water quality improvement degree (WQID). The WQID is proposed to quantify the disturbance degree of human activities to the near-natural relationship between the water quality and discharge rate of a river. The Yihe River in Northern China is selected as a case study to apply the proposed framework. The results show that the observed flow discharge rates of some abnormal months after a specific time of change-point are greater than the estimated discharges under the river's near-natural condition. The WQID values in these abnormal months are less than 1, resulting in a decrease in the modified water resources surplus (WRS*) or an increase in the modified water resources deficit (WRD*). This indicates that the WQID can take into account the near-natural law between water quantity and quality to make a more objective evaluation of integrated water resources management for the months of interest. The proposed framework can serve as a useful and reliable tool for a comprehensive assessment of the watershed management performance of a river system.

Water quality criteria for the protection of human health of 15 toxic metals and their human risk in surface water, China

In the absence of water quality criteria (WQC) support for the current water quality standard (WQS), systematic WQC studies have been carried out in recent years in China. WQC for the protection of human health is established to reflect long-term consumption safety of aquatic products and water. Human health WQC for 15 toxic metals and metalloids based on exposure factors of the Chinese population and 40 field bioaccumulation factors (BAFs) were developed and analyzed in this study. Moreover, age-specific (age 2-5, 6-8, 9-11, 12-14, 15-17, and adult) and region-specific (east, central and west China) WQC were analyzed to better understanding of the impact of specific parameter values on WQC. Human health WQC with consumption of fishes and water, consumption of fishes only, and consumption of water only were derived separately. WQC with consumption of water and organism for Hg, Cd, As, Sb, Se, Zn, Co, Cu, Ni, Pb, Mn, Sn, Ba, and Sr were 0.0264, 0.710, 0.827, 3.48, 22.1, 25.7, 32.2, 32.9, 35.5, 41.8, 72.1, 97.1, 206 and 2.20 × 10³ μg/L, and were 13.3 and 6.67 × 10³ μg/L for Cr(VI) and Cr(III) with consumption of water only. Comparison of age-specific and region-specific WQC showed that the protection for a specific population should be considered in the development of WQC and WQS, as well as cancer effect for carcinogenic metals. Health risk analysis showed that Cd, Cu, Zn, As, Hg and Mn average concentrations in 7, 5, 9, 22, 11 and 5 provinces exceeded the WQC values with consumption of water and aquatic product, showing potential long-term health risk (HQ ≥ 1) to the local population. Therefore, health risks posed by these metals from dietary intake related to surface water should be paying more attention.

Risk prediction of microcystins based on water quality surrogates: A case study in a eutrophicated urban river network

Microcystins (MCs), the toxic by-products from harmful algal bloom (HAB), have caused world-wide concern due to their acute toxicity in freshwater ecosystems. Most studies on HAB have been conducted for shallow freshwater lakes, such as Taihu Lake in China. However, algal blooms in urban rivers located downstream of eutrophicated lakes are also a serious problem for local administrators. It is important for them to know the current and potential risk level of MCs. This environmental issue is rarely reported or discussed. Within this context, we monitored MC concentrations in the Binhu River Network (BRN) in the algal bloom season (Aug, Sep, and Oct) in 2019. To note if the MC concentrations were dangerous, we used 1.0 μg/L suggested by the World Health Organization as the standard value. The proportions of MC samples violating the standard value were 31.78% (Aug), 21.14% (Sep) and 30.77% (Oct). We also designed two statistical models to predict MC concentrations and the possibility to exceed the standard level based on 10 water quality surrogates: Artificial Neural Network (ANN) and Logistic Regression (LR) models. These two models were trained and validated by the monitoring dataset (n = 224). Both models had good performances during training and testing. Although the water quality varied diversely both in spatial and temporal scale, Cluster Analysis (CA) could detect similarities among the samples and separated them into 3 classes, with each class denoting different types of rivers based on the 10 water quality surrogates. Then the ANN and LR were applied as a function of chl-a in each class; by gradually increasing chl-a concentration, we detected chl-a thresholds in class 1, 2, 3 were 25.5, 224, and 109.5 μg/L, respectively, when MCs have a 50% possibility to exceed standard level. The threshold values provided important implications for MC management in the BRN.

Improving the Water Quality Monitoring System in the Yangtze River Basin—Legal Suggestions to the Implementation of the Yangtze River Protection Law

The Yangtze River Basin is the largest river basin in China and has the most complex trans-boundary problems. The water quality monitoring system of the provincial boundary sections in the basin is the typical go-to system to show the interaction between administrative regions and basins. In this article, we discuss the water quality monitoring system in the basin from a legal perspective, explore the achievements and deficiencies of the system, and identify the main elements that constrain the effective operation of the system in the basin, including the fragmented competencies of monitoring institutions, the different monitoring techniques, the overlapping monitoring contents and scopes, the different data releasing channels, and the different applications of the data. We provide legislative suggestions to implement the newly enacted Yangtze River Protection Law and valuable lessons for the design of monitoring systems in other countries or (trans-boundary) basins that face a similar situation.

Comparison of in situ sediment remediation amendments: Risk perspectives from species sensitivity distribution

Contaminated sediment is a major issue for aquatic environments, but attention must be kept even during remediation activities that can negatively affect resident biota especially when applied in situ. For the first time, the species sensitivity distribution (SSD) approach was applied to amendments used for in situ sediment remediation considering 39 papers including both freshwater (F) and saltwater (S) effect data (i.e. n = 17 only F, n = 19 only S, and n = 3 both F and S). Toxicity data related to the application of activated carbon (AC), nano-Zero-Valent-Iron (nZVI), apatite (A), organoclay (OC) and zeolite (Z) were collected and analyzed. SSD curves were constructed by lognormal model providing comprehensive comparisons of the sensitivities of different species to the relative testing methods. Results indicated that Bacteria were the most sensitive group of testing organisms, while Crustaceans were the less sensitive. The hazardous concentration for 5% of the affected species (HC5) were derived to determine the concentration protecting 95% of the species. OC, A and Z presented both acute and chronic toxicity. The HC5 values in descending order are: AC (4.79 g/L) > nZVI (0.02 g/L) > OC, A and Z (1.77E-04 g/L). AC and nZVI can be considered safer than OC, A and Z in sediment remediation activities, even if in situ long-term effects remained still underexplored.

Benchmarking inference methods for water quality monitoring and status classification

River water quality monitoring at limited temporal resolution can lead to imprecise and inaccurate classification of physicochemical status due to sampling error. Bayesian inference allows for the quantification of this uncertainty, which can assist decision-making. However, implicit assumptions of Bayesian methods can cause further uncertainty in the uncertainty quantification, so-called second-order uncertainty. In this study, and for the first time, we rigorously assessed this second-order uncertainty for inference of common water quality statistics (mean and 95th percentile) based on sub-sampling high-frequency (hourly) total reactive phosphorus (TRP) concentration data from three watersheds. The statistics were inferred with the low-resolution sub-samples using the Bayesian lognormal distribution and bootstrap, frequentist t test, and face-value approach and were compared with those of the high-frequency data as benchmarks. The t test exhibited a high risk of bias in estimating the water quality statistics of interest and corresponding physicochemical status (up to 99% of sub-samples). The Bayesian lognormal model provided a good fit to the high-frequency TRP concentration data and the least biased classification of physicochemical status (< 5% of sub-samples). Our results suggest wide applicability of Bayesian inference for water quality status classification, a new approach for regulatory practice that provides uncertainty information about water quality monitoring and regulatory classification with reduced bias compared to frequentist approaches. Furthermore, the study elucidates sizeable second-order uncertainty due to the choice of statistical model, which could be quantified based on the high-frequency data.

Green approach for simultaneous determination of multi-pesticide residue in environmental water samples using excitation-emission matrix fluorescence and multivariate calibration

Pesticides are among the most widespread organic contaminants in aquatic environments. In this work, a new green fluorescence application was proposed for the simultaneous determination of four widely employed pesticides in environmental water samples. To overcome the highly overlapped spectra within the analytes, and with the tissue matrix interferences in complex solutions, we have used the multivariate calibration methods such as parallel factor analysis (PARAFAC) and unfolded partial least squares coupled to residual bilinearization (U-PLS/RBL). These four pesticides can be identified simultaneously, and the correlation coefficients between resolved and actual spectra are all above 0.95. The second-order advantage allowed the determination of four pesticides at the ng mL^-1 level, even in the presence of humic acid (HA). The best results were obtained with the limits of detection of 1.72-18.69 for Carbendazim (CBZ), 0.30-5.19 for carbaryl (CAR), 0.35-6.32 for chlorothalonil (CHL), and 4.92-29.96 for tsumacide (TSU) (ng mL^-1), which can fully meet the quantitative detection and analysis requirements of trace pesticides in water samples. The real water sample of Bohai Seawater was used to check the performance of this approach in practical applications, which have achieved good prediction results of U-PLS/RBL. This study demonstrated the proposed method is rapid, accurate, sensitive, low detection limit, and environmentally friendly to determinate multi-pesticide residues in environmental water samples.

Technical study on national mandatory guideline for deriving water quality criteria for the protection of freshwater aquatic organisms in China

Water quality criteria are the basis for formulating environmental water quality standards, and are also an important part of environmental water protection and environmental management programs. The current study focused on a systematic discussion of the current research progress of water quality criteria theories and methodology for aquatic organisms both in China and internationally. This study also successfully pointed out key scientific issues which should be considered in the determination of water quality criteria guidelines from the following perspectives for a national strategy: the selection of pollutants; data collection and screening; species selection; water quality criteria derivation methods, and so on. For the first time, this study systematically introduced technology for the determination of water quality criteria guidelines for protecting aquatic organisms which was suitable for China's regional characteristics and national conditions. Furthermore, this study pointed out the key research directions which should be considered in the future construction of China's environmental criteria and management systems, in order to provide technical support for environmental protection and management projects.

Screening and prioritization of chemical hazards for deriving human health ambient water quality criteria in China

A two-step screening and prioritization approach of the chemical hazard to derive water quality criteria for the protection of human health in China was developed. Seventy-five potential candidate chemicals were identified in Step 1, and then were screened and scored in Step 2, based on three characteristics: detection frequency, toxicity, and human exposure. Substances with a score above 900 were considered the proposed candidates. Using this approach, 18 chemicals were successfully identified, and ranked in the following order: zinc, di(2-ethylhexyl) phthalate, dibutyl phthalate, trichloromethane, arsenic, cadmium, gamma-hexachlorocyclohexane (HCH), copper, benzo[a]pyrene, lead, benzene, fluoranthene, mercury, beta-HCH, anthracene, p,p'-DDT, and alpha-HCH. Additional chemical contaminants, including thallium, antimony, chromium (VI), and nitrobenzene, suggested by the Ministry of Environmental Protection for consideration during the development of the water quality criteria, brought the final number of proposed candidates to 22. These candidates belong to different groups: nine metals, four polycyclic aromatic hydrocarbons (PAHs), four pesticides, two phthalic acid esters, one halogenated hydrocarbon, and two monocyclic aromatic hydrocarbons. This list of pollutants will provide guidance when selecting the substances to be considered during the development of water quality criteria for the protection of human health in China.

How Specific Is Site-Specific? A Review and Guidance for Selecting and Evaluating Approaches for Deriving Local Water Quality Benchmarks

Existing prescriptive guidance on the derivation of local water quality benchmarks (WQBs; e.g., guideline values, criteria, standards) for protecting aquatic ecosystems is limited to only 3 to 4 specific approaches. These approaches do not represent the full suite available for deriving local WQBs for multiple types of water quality-related issues. The general lack of guidance is inconsistent with the need for, and benefits of, local WQBs, and can constrain the appropriate selection and subsequent evaluation of derivation approaches. Consequently, the defensibility of local WQBs may not be commensurate with the nature of the issues for which they are derived. Moreover, where local WQBs are incorporated into regulatory requirements, the lack of guidance presents a potential risk to the derivation of appropriate WQBs and the achievement of desired environmental outcomes. This review addresses the deficiency in guidance by 1) defining local WQBs and outlining initial considerations for deciding if one is required; 2) summarizing the existing regulatory context; 3) summarizing existing guidance and identifying gaps; 4) describing strengths, weaknesses, and potential applications of a range of derivation approaches based on laboratory and/or field data; and 5) presenting a conceptual framework for appropriately selecting and evaluating a derivation approach to best suit the need. The guidance incorporates an existing set of guiding principles for deriving local WQBs and reinforces an existing categorization of site-adapted and site-specific WQBs. The conceptual framework recognizes the need to strike an appropriate balance between effort and ecological risk and, thus, embeds the concept of fit-for-purpose by considering both the significance of the issue being assessed and the extent to which the approach provides confidence that the ecosystem will be appropriately protected. The guidance can be used by industry, regulators, and others for both the a priori selection and the post hoc evaluation of appropriate approaches for deriving local WQBs. Integr Environ Assess Manag 2019;15:683-702. © 2019 The Authors.

Progress in rapid optical assays for heavy metal ions based on the use of nanoparticles and receptor molecules

This review (with 230 refs.) covers recent progress in rapid optical assays for heavy metals (primarily lead and mercury as the most relevant) based on the use of nanoparticles and receptor molecules. An introduction surveys the importance, regulatory demands (such as maximum permissible concentrations) and potential and limitations of various existing methods. This is followed by a general discussion on the use of nanoparticles in optical assays of heavy metals (including properties, basic mechanisms of signal generation). The next sections cover methods for the functionalization of nanoparticles with (a) sulfur-containing compounds (used for modification of nanoparticles or added to the reaction medium), (b) nitrogen-containing compounds (such as amino acids, polypeptides, and heterocyclic molecules), and (c) oxygen-containing species (such as hydroxy and carbonyl compounds). This is continued by a specific description of specific assays based on the use of aptamers as receptors, on the use of deoxyribozymes as synthetic reaction catalysts, of G-quadruplex aptamers, of aptamers in logic gate-type of assays of linear (unstructured) aptamers ("hairpins"), and on the use of aptamers in lateral flow assays. A next section covers assays based on the employment of antibodies as receptors (used in the immunoassay development). The properties of various nanoparticles and their applicability in optical assays are also discussed in some detail. Final sections discuss the selectivity of assays, potential interferences by other cations, methods for their elimination, and also matrix effects and approaches for sample pretreatment. A concluding section discusses current challenges and future trends. Analysis based on enzyme inhibition assay is not treated here but enzyme-like action of some receptor molecules such as DNAzymes is discussed. Graphical abstract Schematic presentation of main principles of application of various nanoparticles with receptor molecules (S-, N-, O-containing, heterocyclic compounds, proteins, antibody, aptamers) for heavy metals ions detection. The included methods cover optical assays with description of mechanisms of interactions and signal generation.

How can we improve understanding of faecal indicator dynamics in karst systems under changing climatic, population, and land use stressors? - Research opportunities in SW China

Human exposure to water contaminated with faeces is a leading cause of worldwide ill-health. Contaminated water can be transmitted rapidly in karst terrain as a result of the connectivity of surface and groundwater systems, high transmissivity of aquifers over large areas, and well-developed underground conduit systems. Faecal indicator organisms (FIOs) are the most widely-used indicator of faecal contamination and microbial water quality; however, the conceptualisation of FIO risk and associated sources, pathways, and survival dynamics of FIOs in karst landscapes requires a degree of modification from traditional conceptual models of FIO fate and transfer in non-karst systems. While a number of reviews have provided detailed accounts of the state-of-the-science concerning FIO dynamics in catchments, specific reference to the uniqueness of karst and its influence on FIO fate and transfer is a common omission. In response, we use a mixed methods approach of critical review combined with a quantitative survey of 372 residents of a typical karst catchment in the southwest China karst region (SWCKR) to identify emerging research needs in an area where much of the population lives in poverty and is groundwater dependent. We found that the key research needs are to understand: 1) overland and subsurface FIO export pathways in karst hydrology under varying flow conditions; 2) urban and agricultural sources and loading in mixed land-use paddy farming catchments; 3) FIO survival in paddy farming systems and environmental matrices in karst terrain; 4) sediment-FIO interactions and legacy risk in karst terrain; and 5) key needs for improved hydrological modelling and risk assessment in karst landscapes. Improved knowledge of these research themes will enable the development of evidence-based faecal contamination mitigation strategies for managing land and water resources in the SWCKR, which is highly vulnerable to climate change impacts on water supply and quality of water resources.

Bioelectrochemical Systems for Removal of Selected Metals and Perchlorate from Groundwater: A Review

Groundwater contamination is a major issue for human health, due to its largely diffused exploitation for water supply. Several pollutants have been detected in groundwater; amongst them arsenic, cadmium, chromium, vanadium, and perchlorate. Various technologies have been applied for groundwater remediation, involving physical, chemical, and biological processes. Bioelectrochemical systems (BES) have emerged over the last 15 years as an alternative to conventional treatments for a wide variety of wastewater, and have been proposed as a feasible option for groundwater remediation due to the nature of the technology: the presence of two different redox environments, the use of electrodes as virtually inexhaustible electron acceptor/donor (anode and cathode, respectively), and the possibility of microbial catalysis enhance their possibility to achieve complete remediation of contaminants, even in combination. Arsenic and organic matter can be oxidized at the bioanode, while vanadium, perchlorate, chromium, and cadmium can be reduced at the cathode, which can be biotic or abiotic. Additionally, BES has been shown to produce bioenergy while performing organic contaminants removal, lowering the overall energy balance. This review examines the application of BES for groundwater remediation of arsenic, cadmium, chromium, vanadium, and perchlorate, focusing also on the perspectives of the technology in the groundwater treatment field.