Advanced Treatment and Disinfection of Hospital Wastewater: Progress, Monitoring Gaps, and Trends

Disinfection By-Products: Formation and Occurrence in Drinking Water⋆⋆This article has been reviewed in accordance with the US EPA's peer and administrative review policies and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the US EPA.

Comprehensive assessment of electrochemical disinfection for real secondary effluent: more efficient with reduced secondary chemical risk?

The use of oxidants (chlorine, chlorine dioxide and ozone) is a priority way of safe water supply. However, their use involves control of the formation, determination and normalization of chlorites and chlorates as by-products of disinfection. The aim of the work was to characterize the topical issues of monitoring the content of chlorites and chlorates in drinking water after disinfection with oxidants. Research methods included bibliometric and analytical. The results are as follows. The analysis of foreign and domestic normative documents testifies to the need to harmonize the current DSanPiN 2.2.4-171-10 “Hygienic requirements for drinking water suitable for human consumption” regarding the standardization of chlorites and chlorates in accordance with international requirements. It should be noted that these values, namely the normative values ​​for chlorites and chlorates at the level of 0.7 and 0.7 mg / l, respectively, were included in the latest version of the above-mentioned normative document DSanPiN 2.2.4-171-20. An analysis of the experience gained in Europe (European federation of national associations of water services) shows that the main source of chlorite and chlorate formation is not chlorine dioxide, as previously thought, but sodium hypochlorite. According to the WHO, chlorate is a typical by-product of disinfection in the treatment of water with oxidants (sodium hypochlorite, chloramines, chlorine dioxide, ozone). Currently, research on the development of technological principles for minimizing the content of chlorites and chlorates as by-products of water disinfection by oxidants in Ukraine has not been conducted. The above necessitates the implementation of the following tasks: generalization of research results of chlorite content in drinking water from centralized drinking water supply systems, where chlorine dioxide is used; development, testing and implementation of the method of determination of chlorates in drinking water; determination of the content of chlorites and chlorates in the finished sodium hypochlorite, which is supplied to water utilities, depending on the shelf life; monitoring the content of chlorites and chlorates in drinking water of settlements where sodium hypochlorite is used in the process of water treatment; determination of chlorate content in chlorinated tap water after its treatment with ozone; substantiation of optimal modes of water treatment with oxidants to minimize the content of chlorites and chlorates in drinking water from the water distribution network; development of technological principles for minimizing the content of chlorites and chlorates in drinking water after disinfection with oxidants.

Separate treatment of hospital and urban wastewaters: A real scale comparison of effluents and their effect on microbial communities

Inactivation of antibiotic-resistant bacteria in hospital wastewater by ozone-based advanced water treatment processes

Disinfectants and preservatives used as biocides may contain or release active substances (a.s.) that can form by-products with the surrounding matrices during their application which may be released into the environment. Over the past 40 years, several hundred of these so-called disinfection by-products (DBPs) have been detected after applications of biocides used for disinfection. Due to intensive research and further development of analytical capabilities, many new DBP classes, such as iodinated DBPs (I-DBPs), halonitromethanes (HNMs), haloacetamides (HaAms), or halomethanesulfonic acids were detected worldwide in various matrices and applications. Due to the possible hazards and risks for humans and the environment, frequently occurring DBP classes, such as trihalomethanes (THM), haloacetic acids (HAA) and nitrosamines (NDMA), have already been included in many legislations and given limit values. In the European Union, biocides are assessed under the Biocidal Products Regulation 528/2012 (BPR) regarding their efficacy, potential hazards, and risks to human health and the environment. However, the available guidance for the environmental risk assessment (ERA) of DBPs remains vague. To identify knowledge gaps and to further develop the assessment scheme for the ERA of DBPs, a literature search on the multiple uses of biocides and their formation potential of DBPs was performed and the existing process for ERA was evaluated. The results show knowledge gaps on the formation of DBP in non-aqueous systems and DBP formation by non-halogen-based biocidal active substances. Based on the literature research on biocides, a possible proposal of grouping a.s. to consider their DBP formation potential is presented to simplify future ERAs. However, this also requires further research. Until then, a pragmatic approach considering the DBPs formation potential of the active substances and the identified knowledge gaps need to be established for the environmental risk assessment of DBPs in the EU.Graphical

Disinfection byproducts (DBPs) are formed during drinking water treatment from the reaction of chemical disinfectants with natural organic matter (NOM), anthropogenic contaminants, and inorganic bromide and iodide. DBPs are of public concern due to their carcinogenic and genotoxic effects and adverse effects observed in many epidemiologic studies. Formation mechanisms have been studied in order to identify precursors, reaction intermediates, and reaction kinetics and to predict new classes of DBPs. By understanding formation mechanisms, steps can be taken to remove DBP precursors and adjust treatment conditions to minimize DBP formation. This paper presents a critical review of formation mechanisms for eight classes of DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs), haloacetaldehydes (HALs), haloacetonitriles (HANs), haloacetamides (HAMs), halonitromethanes (HNMs), and nitrosamines (NAs) from the popular disinfectants chlorine, chloramine, and ozone. Important precursors in the formation of many of these DBPs include phenolic, β-dicarbonyl, and oxopentadioic acid groups found in humic NOM species. Likewise, amino acids are also precursors for several classes of DBPs. HANs can form by chloramination of aldehydes, and HAMs can form from the hydrolysis of HANs. HNMs can form by the oxidation/halogenation of amines as well as by nitration and halogenation of humic substances in the presence of nitrite. Preozonation followed by chlorine or chloramine can significantly increase HNM formation. Finally, dichloramine and aqueous oxygen are important reactants in the formation of nitrosamines from chloramine. Nitrosamines can also be formed by N,N-dimethylsulfamide. Detailed formation mechanisms for 8 classes of drinking water DBPs formed by chlorine, chloramine, and ozone are presented.

Antimicrobial resistance: A new threat from disinfection byproducts and disinfection of drinking water?

Hospital and urban wastewaters shape the matrix and active resistome of environmental biofilms

Due to their elevated concentrations in drinking water, compared to other emerging environmental contaminants, disinfection byproducts (DBPs) have become a global concern. To address this, we have created a simple and sensitive method for simultaneously measuring 9 classes of DBPs. Haloacetic acids (HAAs) and iodo-acetic acids (IAAs) are determined using silylation derivatization, replacing diazomethane or acidic methanol derivatization with a more environmentally friendly and simpler treatment process that also offers greater sensitivity. Mono-/di-haloacetaldehydes (mono-/di-HALs) are directly analyzed without derivatization, along with trihalomethanes (THMs), iodo-THMs, haloketones, haloacetonitriles, haloacetamides, and halonitromethanes. Of the 50 DBPs studied, recoveries for most were 70-130%, LOQs for most were 0.01-0.05 μg/L, and relative standard deviations were <30%. We subsequently applied this method to 13 home tap water samples. Total concentrations of 9 classes of DBPs were 39.6-79.2 μg/L, in which unregulated priority DBPs contributed 42% of total DBP concentrations and 97% of total calculated cytotoxicity, highlighting the importance of monitoring their presence in drinking water. Br-DBPs were the dominant contributors to total DBPs (54%) and total calculated cytotoxicity (92%). Nitrogenous DBPs contributed 25% of total DBPs while inducing 57% of total calculated cytotoxicity. HALs were the most important toxicity drivers (40%), particularly four mono-/di-HALs, which induced 28% of total calculated cytotoxicity. This simple and sensitive method allows the synchronous analysis of 9 classes of regulated and unregulated priority DBPs and overcomes the weaknesses of some other methods especially for HAAs/IAAs and mono-/di-HALs, providing a useful tool for research on regulated and unregulated priority DBPs.

A review on hospital wastewater treatment: A special emphasis on occurrence and removal of pharmaceutically active compounds, resistant microorganisms, and SARS-CoV-2

Effluents from wastewater treatment plants (WWTPs) contain disinfection byproducts (DBPs) of health concern when the water is utilized downstream as a potable water supply. The pattern of DBP formation was strongly affected by whether or not the WWTP achieved good nitrification. Chlorine addition to poorly nitrified effluents formed low levels of halogenated DBPs, except for (in some cases) dihalogenated acetic acids, but often substantial amounts of N-nitrosodimethyamine (NDMA). Chlorination of well-nitrified effluent typically resulted in substantial formation of halogenated DBPs but much less NDMA. For example, on a median basis after chlorine addition, the well-nitrified effluents had 57 microg/L of trihalomethanes [THMs] and 3 ng/L of NDMA, while the poorly nitrified effluents had 2 microg/L of THMs and 11 ng/L of NDMA. DBPs with amino acid precursors (haloacetonitriles, haloacetaldehydes) formed at substantial levels after chlorination of well-nitrified effluent. The formation of halogenated DBPs but not that of NDMA correlated with the formation of THMs in WWTP effluents disinfected with free chlorine. However, THM formation did not correlate with the formation of other DBPs in effluents disinfected with chloramines. Because of the relatively high levels of bromide in treated wastewater, bromine incorporation was observed in various classes of DBPs.

Disinfection by-products formation and acute toxicity variation of hospital wastewater under different disinfection processes

This study quantified antibiotic and antibiotic resistance gene (ARG) concentrations in hospital and communal wastewaters as well as the influents and effluents of the receiving urban wastewater treatment plants (UWWTP) in two Dutch cities. In only one city, hospital wastewater was treated on-site using advanced technologies, including membrane bioreactor treatment (MBR), ozonation, granulated activated carbon (GAC) and UV-treatment. On-site hospital wastewater (HWW) treatment reduced gene presence of hospital-related antibiotic resistance genes and antibiotic concentrations in the receiving urban wastewater treatment plant. These findings support the need for on-site treatment of high-risk point sources of antibiotic resistance genes. 13 antibiotic resistance genes, Integrase Class 1 and 16S rRNA concentrations were quantified using multiplex quantitative real-time PCR (qPCR) assays and the presence and/or concentration of 711 antibiotics were analyzed. Hospital wastewater contained approximately 25% more antibiotics and gene concentrations between 0.4 log to 1.8-fold higher than communal wastewater (CWW). blaKPC and vanA could be identified as hospital-related genes and were reduced to under the limit of detection (LOD) during on-site treatment. Advanced on-site treatment removed between 0.5 and 3.6-fold more genes than conventional biological urban wastewater treatment (activated sludge). Advanced on-site treatment was able to eliminate 12 out of 19 detected antibiotics, while urban waste water treatment eliminated up to 1 (out of 21 detected). Different advanced treatment technologies were able to target different pollutants to varying extents, making sequential alignment more effective. MBR treatment was most efficient in antibiotic resistance gene reduction and ozonation in antibiotic reduction. blaKPC could only be detected in the influent of the urban wastewater treatment plant receiving untreated hospital wastewater. Similarly, vanA was only consistently detected in this treatment plant. These results indicate a positive effect of on-site treatment of hospital wastewater on the communal sewage system.

Treatment of hospital wastewater through the CWPO-Photoassisted process catalyzed by ilmenite