Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

Formation potentials of typical disinfection byproducts and changes of genotoxicity for chlorinated tertiary effluent pretreated by ozone

The effects of ozonation on the formation potential of typical disinfection byproducts （DBPs） and the changes of genotoxicity during post chlorination of tertiary effluent from a sewage treatment plant were investigated. Ozonation enhanced the yields of all detected chlorine DBPs except CHCI3. At a chlorine dose of 5 mg/L, the three brominated THMs and five HAAs increased, while chloroform decreased with the increase of ozone dose from 0 to 10 mg/L （ozone dose in consumption base）. At a chlorine dose of 10 mg/L, the two mixed bromochloro species THMs and two dominant HAAs （DCAA and TCAA） increased firstly and then decreased with the increase of ozone dose, with the turning point approximately occurring at an ozone dose of 5 mg/L. The genotoxicity detected using umu test, on the other hand, was removed from 7 Ixg 4-NQO/L to a negligible level by ozonation under an ozone dose of 5 mg/L. Chlorination could further remove the genotoxicity to some extent. It was found that SUVA （UV absorbance divided by DOC concentration） might be used as an indicative parameter for monitoring the removal of genotoxicity during the oxidation.

pH effect on the formation of THM and HAA disinfection byproducts and potential control strategies for food processing

Chlorine-based sanitizers have seen wide spread use in food sanitation. The reaction of chlorine species with organic matter is a concern for two reasons. Available chlorine can be “used up” by organic compounds resulting in a lower amount of chlorine available for disinfection. Another concern is that some forms of chlorine can react with some organic compounds to form toxic halogenated disinfection byproducts（DBPs）. Many studies have been conducted to evaluate the role of hypochlorous acid（HOCl） and hypochlorite ion（OCl–） in the production of DBPs with a particular interest in the production of trihalomethanes（THMs） and haloacetic acids（HAAs）. Since most of the chlorine reactions are pH dependent, pH is found to have a significant effect on the formation of chlorine DBPs. In many cases, the concentration of THMs decreases and HAAs increases as pH decreases. pH also plays an important role in the determination of the type and amount of DBPs formed, with lower, more acidic, pHs resulting in the formation of less chloroform. This review summarizes the information from the literature on the role of chlorine-based sanitizers as affected by pH in the formation of different types of DBPs. Alternative novel strategies to minimize the formation of DBPs are also discussed.

Extraction of Total Phenolic Compounds, Flavonoids, Anthocyanins and Tannins from Grape Byproducts by Response Surface Methodology. Influence of Solid-Liquid Ratio, Particle Size, Time, Temperature and Solvent Mixtures on the Optimization Process

The current work concerns the optimization process of phenolic compounds solid liquid extraction from grape byproducts at high temperatures and short incubation times. The effect of five experimental parameters (solidliquid ratio, particle size, time, temperature and solvent mixture) mostly believed to affect the extraction process was undertaken. A first response surface methodology experimental design was used to optimize the solid-liquid ratio and milling time parameters. A second design was used for the optimization of the quantitative and qualitative parameters. The quantitative parameters studied are: total phenolic compounds, flavonoid content, total monomeric anthocyanin composition and tannin concentration. The qualitative parameters analyzed are: antiradical activity and antioxidant capacity. The second design was based on the use of time, temperature and solvent mixture as optimization parameters. The assays were first conducted separately revealing the best experimental conditions for the maximization of each response variable alone. A simultaneous response surface methodology of all the responses taken together was then conducted, showing the optimal extraction conditions to be: 93 minutes at 94?C and in 66% ethanol/water solvent. The maximal response values obtained for each parameter are: Total Phenolic Compounds yield (5.5 g GAE/100g DM), Flavonoid Content (5.4 g GAE/100g DM), Total Monomeric Anthocyanin yield (70.3 mg/100g DM), Tannin Concentration (12.3 g/L), Antiradical Activity (67.3%) and Total Antioxidant Capacity (393 mgAAE/L). All of the optimal values were acquired at 3 mL/g solid-liquid ratio and 6.8 min milling time. The obtained extracts could be used as natural bioactive compounds in several industrial applications.

Multiple Response Optimization of High Temperature, Low Time Aqueous Extraction Process of Phenolic Compounds from Grape Byproducts

In this study phenolic compounds extraction from grape byproducts was conducted using pure water as a solvent. High temperatures and low time incubation periods were used in the aim of reducing the cost of the process and heightening the phenolic compounds yield. Response surface methodology (RSM) was realized to study the effect of time and temperature on crushed and uncrushed grape pomace. The phenolic content was evaluated considering the quantity (total phenolics (TPC), flavonoids (FC), total monomeric anthocyanins (TMA) and tannins (TC)), and quality (antiradical activity (AA) and antioxidant capacity (AC)) of the extracts. High temperature low time extraction design used in this study was compared to the extraction process at moderate temperatures with relatively long periods of time. This was proved to ameliorate the quantitative extraction of phenolic compounds from grape pomace without affecting their bioactivity. Moreover, multiple response optimization showed the optimal extraction parameters to be 81?C and 140 minutes for the unmilled pomace samples, and 88?C and 5 minutes for the milled. TPC, FC, TMA, TC, AA and AC are almost the same for both optimums. Thus the possibility of replacing the milling process by the extraction time prolongation (for the unmilled pomace) of 135 minutes seems to be very plausible. HPLC analysis showed different quantity and diversity of extracted phenolics for the optimums. However this difference did not significantly affect the overall activity, showing that PC in the different extracts act in complete synergy all together leading to important biological properties. The obtained results using the extraction strategy adopted in this work could lead to several industrial applications.

Advances in xylooligosaccharides from grain byproducts:Extraction and prebiotic effects

Xylooligosaccharides(XOS)are mainly derived from lignocellulosic materials,such as rice husk,corn cobs,straw,wheat bran,wheat straw and other grain by-products.XOS have become one of the functional oligosaccharides of great concern at home and abroad due to their beneficial functional properties,such as low calorie,high stability,poor digestibility and high performance in proliferating probiotics.At present,the XOS extraction methods from grain byproducts mainly include autohydrolysis,acidolysis and enzymolysis.Among them,autohydrolysis has high requirements for equipment for achieving higher extraction rate and higher purity of products;and acidolysis can cause environmental pollution due to the usage of harmful reagents.Enzymolysis is the most common method for the production of XOS because of its high convenience,high efficiency and no pollution;and the widely used enzyme is the xylanase from Aspergillus niger.Current researches have showed that XOS can be utilized by probiotics such as Bifidobacteria and Lactobacillus to exert prebiotic effects,such as optimizing intestinal flora,promoting intestinal health,improving intestinal barrier,enhancing immune function,improving antioxidant capacity and so on.However,XOS extracted from the grain byproducts contain a large amount of impurities,which limits their industrial application and makes it dif-ficult to control the product quality.Therefore,XOS refining,separation and purification has become the key to their subsequent industrial application.This paper reviewed the current status of XOS extraction technologies from various grain by-products,and also summarized the prebiotic effect of XOS to provide reference for industrial production of XOS and its wide application in prebiotics market,thereby facilitating utilization and development of grain byproducts.

SF₆Byproducts in High-Humidity Environment: an Experimental Evaluation between 200^oC and 500^oC

Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing these byproducts is an effective method to judge the internal operation condition of electric equipment. In order to study characters of SF6byproducts at different temperature of overheated faults in the electric equipment, a series of overheated faults of electric equipment were simulated. SF6is very stable and not significantly decomposed at 200oC, 250oC and 300oC. SF6is significantly decomposed to SO2, H2S and HF at 350oC. The concentration of SO2, H2S and HF was 7.2, 1.6 and 1.9 μL/L after heating for 5 hours in environment of SF6with 3616 μL/L water, and it was increased to 23.0, 3.0 and 1.2 μL/L 3 hours later. SF6is more easily to be decomposed and decomposed more rapidly at higher temperature. The concentration of SO2, H2S and HF was 62.2, 15.6 and 3.6 μL/L after heating for 5 hours in environment of SF6with 4064 μL/L water, and it was increased to 91.4, 25.2 and 2.3 μL/L 3 hours later. SF6will be decomposed to format HF, which is strongly corrosive and whose concentration is likely to decrease when it is above a certain concentration.

An Environment Friendly, Low-Cost Extraction Process of Phenolic Compounds from Grape Byproducts. Optimization by Multi-Response Surface Methodology

Due to their beneficial effects on human health, phenolic compounds are increasingly attracting the attention of scientists and researchers all over the world. The main interest is in the extraction process of those natural plant-originated compounds from fruits, vegetables and plant wastes, namely grape wastes, in which phenolic compounds are the most abundant secondary metabolites. This waste exploitation not only re-assimilates those byproducts into the food cycle, but also avoids major environmental problems. Herein, the optimization of the phenolic compounds concentration and free radical scavenging activity from Cabernet Sauvignon grape byproducts was conducted, using multi-response surface methodology. A conventional solid-liquid extraction process was performed with pure water as a solvent to study the effects of both time and temperature on the procedure. The maximal phenolic compounds concentration (878.9 mg/L) was reached at 47℃ after 30 hours while the optimal free radical scavenging activity (41.15%) was obtained at 30℃ after 20 hours. A multi-response surface methodology compromised between the quantity and the quality of the extracted phenolics, and the parameters maximizing both responses were obtained at 37℃ and 28 hours. This low-cost and energy saving process provides an excellent tool for further industrial applications.

Evaluation of Physicochemical and Functional Properties of Protein Recovered Obtaining from Whitemouth Croaker (<i>Micropogonias furnieri</i>) Byproducts

Proteins recovered were obtained from Whitemouth Croaker (Micropogonias furnieri) byproducts and their physico-chemical and functional properties were evaluated. The proximate composition, presented 8.64% ± 0.10% of moisture, 85.33% ± 0.12% of protein, 2.69% ± 0.09% of ashes and 2.16% ± 0.12% of lipids, in dry basis. The highest solubility was obtained in pH 11 (93.24%), the maximum water holding capacity was presented at pH 11 (25.71 mL H2O/gprotein), the oil holding capacity was 13.71 mL/gprotein and the digestibility in vitro was 91.32% ± 0.15%. The electro-phoretic profile was observed typical of the myofibrillar proteins, with the appearance of the heavy chain of myosin (220 kDa) and actin (50 kDa). The results show that the products of low commercial value of fish that are usually used for the production of animal feed or simply discarded, contributing to environmental pollution, may be used to produce products with a greater added value.

Exploring the cooperation effect of DBD byproducts and Ag/TiO_2 catalyst for water treatment in an APPJ system

In this paper,the collective effects of combining heterogeneous Ag/TiO2 nanocomposite catalyst with the byproducts（primarily the irradiation and the O3 species） of an atmospheric pressure plasma jet（APPJ） system on the degradation of methyl orange（MO） were explored.The heterostructured Ag/TiO2 nanocomposite was achieved via decorating the Ag quantum dots（QDs） on the commercially available TiO_2catalyst（P25） through a hydrothermal method.The x-ray diffraction analysis of the nanocomposite catalyst showed the diffraction peaks at 44.3°,64.4°,and 77.5°,corresponding to the Ag planes of（200）,（220） and（311）,respectively.The high resolution transmission electron microscope characterization of the nanocomposite catalyst indicated that the Ag QDs with an average diameter of 5 nm were homogeneously distributed on the P25 surface.The experimental results on the MO photodegradation showed that the APPJ irradiation had a marginal effect on the cleavage of the MO molecules.When the Ag/TiO2 nanocomposite catalyst was used,the photodegradation rate of MO increased about 5 times.When both the APPJ byproducts and the Ag/TiO2 nanocomposite catalyst were used,however,over 90% of the MO in the tested solution was cleaved within 15 min,and the energy efficiency was about 0.6 g/k W h.Moreover,an optimal Ag dosage value was determined（6 wt%）.The catalytic results indicated that combining the DBD plasma byproducts with heterogeneous nanocomposite catalysts may be an effect protocol for decreasing the application cost of the DBD system and mitigating the environment pollution by organic dyes in the textile industry.

Use of Asian selected agricultural byproducts to modulate rumen microbes and fermentation

In the last five decades, attempts have been made to improve rumen fermentation and host animal nutrition through modulation of rumen microbiota. The goals have been decreasing methane production, partially inhibiting protein degradation to avoid excess release of ammonia, and activation of fiber digestion. The main approach has been the use of dietary supplements. Since growth-promoting antibiotics were banned in European countries in2006, safer alternatives including plant-derived materials have been explored. Plant oils, their component fatty acids,plant secondary metabolites and other compounds have been studied, and many originate or are abundantly available in Asia as agricultural byproducts. In this review, the potency of selected byproducts in inhibition of methane production and protein degradation, and in stimulation of fiber degradation was described in relation to their modes of action. In particular, cashew and ginkgo byproducts containing alkylphenols to mitigate methane emission and bean husks as a source of functional fiber to boost the number of fiber-degrading bacteria were highlighted. Other byproducts influencing rumen microbiota and fermentation profile were also described. Future application of these feed and additive candidates is very dependent on a sufficient, cost-effective supply and optimal usage in feeding practice.

Synthesis of Carbon Nanotubes from Byproducts of Oil Refiner

Carbon nanotubes have been synthesized by using petroleum coke (PC) as carbon source. Different position of the PC in the reactor chamber and some other reaction parameters is strongly influenced to quantity of the obtained CNTs and their characteristics such as crystallinity, diameter (number of shels), and etc., which is analysed by scanning and tranmission electron microscopes (SEM and TEM). The thickness of the Fe catalyst deposited on Si and SiO2 substrates supported improves the quality, quantity and uniformity of CNTs. Wet-coated thin films of FeCl2 work well as catalyst, which can be profitable for mass production of CNTs.

Control strategies for disinfection byproducts by ion exchange resin,nanofiltration and their sequential combination

Disinfection byproducts (DBPs) are emerging pollutants in drinking water with high health risks. Precursor reduction before disinfection is an effective strategy to control the formation of DBPs. In this study, three types of anion exchange resins (AERs) and two types of nanofiltration (NF) membranes were tested for their control effects on DBP precursors, DBPs, and total organic halogen (TOX). The results showed that, for AER adsorption, the removal efficiencies of DBP precursors, DBPs, and TOX increased with the increase of resin dose, and the strong basic macroporous anion exchange resin (M500MB) had the highest removal efficiencies. For NF, the highest removal efficiencies were achieved at an operating pressure of 4 bar, and the membrane (NF90) with a smaller molecular weight cut-off, had a better control efficiency. However, AER adsorption was inefficient in removing dissolved organic carbon (DOC);NF was inefficient in removing Br− resulting in insufficient control of Br-DBPs. Accordingly, a sequential approach of AER (M500MB) adsorption followed by NF (NF90) was developed to enhance the control efficiency of DBPs. Compared with single AER adsorption and single NF, the sequential approach further increased the removal efficiencies of DOC by 19.4%–101.9%, coupled with the high Br− removal efficiency of 92%, and thus improved the reduction of cyclic DBPs and TOX by 3.5%–4.9%, and 2.4%–8.4%, respectively;the sequential approach also reduced the cytotoxicity of the water sample by 66.4%.

Enhancement of fruit byproducts through bioconversion by Hermetia llucens(Diptera:Stratiomyidae)

Bioconversion is a biological process by which organic materials are converted into products with higher biological and commercial value.During its larval stage the black soldier fly Hermetia illucens is extremely voracious and can feed on a wide vari-ety of organic materials.To study the impact of different fruit byproducts on the insect's growth,final larval biomass,substrate reduction,bioconversion parameters,and larval nu-tritional composition,10000 black soldier fly larvae(BSFL)were reared on 7.0 kg of one of three substrates(strawberry,tangerine,or orange)or on a standard diet as a control.The results highlight that BSFL can successfully feed and grow on each of these diets,though their development time,growth rate,and final biomass were differently impacted by the substrates,with strawberry being the most suitable.The lipid and protein contents of BSFL were similar among larvae fed on different substrates;however,major differences were detected in ash,micronutrient,fiber,fatty acid,and amino acid contents.Overall,the results indicate that fruit waste management through the BSFL bioconversion process rep-resents a commercially promising resource for regional and national agrifood companies.Our study offers new perspectives for sustainable and environmentally friendly industrial development by which fruit byproducts or waste might be disposed of or unconventionally enhanced to create secondary products of high biological and economic value,including BSFL biomass as animal feed or,in perspective,as alternative protein source for human nutrition.

Disinfection byproducts in indoor swimming pool water: Detection and human lifetime health risk assessment

Quantification of regulated and emerging disinfection byproducts (DBPs) in swimming pool water,as well as the assessment of their lifetime health risk are limited in China.In this study,the occurrence of regulated DBPs (e.g.,trihalomethanes,haloacetic acids) and emerging DBPs (e.g.,haloacetonitriles,haloacetaldehydes) in indoor swimming pool water and the corresponding source water at a city in Eastern China were determined.The concentrations of DBPs in swimming pool water were 1-2 orders of magnitude higher than that in source water.Lifetime cancer and non-cancer risks of DBPs stemming from swimming pool water were also estimated.Inhalation and dermal exposure were the most significant exposure routes related to swimming pool DBP cancer and non-cancer risks.For the first time,buccal and aural exposure were considered,and were proven to be important routes of DBP exposure (accounting for 17.9%-38.9%of total risk).The cancer risks of DBPs for all swimmers were higher than 10^(-6)of lifetime exposure risk recommended by United States Environmental Protection Agency,and the competitive adult swimmers experienced the highest cancer risk (7.82×10^(-5)).These findings provide important information and perspectives for future efforts to lower the health risks associated with exposure to DBPs in swimming pool water.

Development and characterization of mycelium bio-composites by utilization of different agricultural residual byproducts

Mycelium bio-composites was developed by incubating Pleurotus ostreatus fungi on different sub-strates from agricultural residual byproducts,including rice straw,bagasse,coir-pith,sawdust,and corn straw.The scanning electron microscope(SEM)results showed that the hypha of com-posite derived from bagasse was the densest,and the diameter of hypha was the biggest(0.77μm),which was presumably due to the existence of cellulose in bagasse in the form of dextran and xylan.The maximum and minimum compression strength for sawdust substrate and corn straw substrate were 456.70 and 270.31 kPa,respectively.The flexural strength for bagasse sub-strate and rice straw substrate were 0.54 and 0.16 MPa,respectively.The two composites derived from rice straw and bagasse exhibited higher hydrophobic properties than others.In comparison,mycelium bio-composite derived from bagasse showed the best comprehensive properties.Except for a little worse anti-creep ability and waterproof performance,other properties of mycelium bio-composites could be comparable to commercially expanded polystyrene(EPS)packaging mate-rial.Derived from this study,mycelium material provided a good way to use agricultural residual byproducts and could be a good alternative to non-biodegradable materials for packaging appli-cations.

Identification of unknown disinfection byproducts in drinking water produced from Taihu Lake source water

Although disinfection byproducts(DBPs) in drinking water have been suggested as a cancer causing factor, the causative compounds have not yet been clarified. In this study, we used liquid chromatography quadrupole-time-of-flight spectrometry(LC-QTOF MS) to identify the unknown disinfection byproducts(DBPs) in drinking water produced from Taihu Lake source water, which is known as a convergence point for the anthropogenic pollutants discharged from intensive industrial activities in the surrounding regions. In total, 91 formulas of DBPs were discovered through LC-QTOF MS nontarget screen, 81 of which have not yet been reported. Among the 91 molecules, 56 only contain bromine, 15 only contain chlorine and 20 DBPs have both bromine and chlorine atoms. Finally, five DBPs including 2,4,6-tribromophenol, 2,6-dibromo-4-chlorophenol, 2,6-dichloro-4-bromophenol, 4-bromo-2,6-di-tert-butylphenol and 3,6-dibromocarbazole were confirmed using standards. The former three compounds mainly formed in the predisinfection step(maximum concentration, 0.2-2.6 μg/L), while the latter two formed in the disinfection step(maximum concentration, 18.2-33.6 ng/L). In addition, 19 possible precursors of the discovered DBPs were detected, with the aromatic compounds being a major group. 2,6-di-tert-butylphenol as the precursor of 4-bromo-2,6-di-tert-butylphenol was confirmed with standard, with a concentration of 20.3 μg/L in raw water. The results of this study show that brominated DBPs which are possibly formed from industrial pollutants are relevant DBP species in drinking water produced form Taihu source water, suggesting protection of Taihu Lake source water is important to control the DBP risks.

Enhanced photocatalytic hydrogen evolution along with byproducts suppressing over Z-scheme CdxZn1-xS/Au/g-C3N4 photocatalysts under visible light

Inspired by natural photosynthesis, a new series of Z-scheme Cd_xZn_(1-x)S/Au/g-C_3N_4 photocatalysts were synthesized via depositing Au particles on g-C_3N_4, followed by anchoring CdxZn_(1-x)S solid solution on the pre-formed Au/g-C_3N_4 for photocatalytic hydrogen evolution. Their structure, morphology and optical property were investigated in detail. Photocatalytic activities of the developed photocatalysts for water splitting were evaluated under visible-light irradiation(k > 420 nm) using glucose as electron donor.The highest hydrogen evolution rate of 123 lmol g^(-1)h^(-1)is achieved by Cd_(0.8Z)n_(0.2)S/Au/g-C_3N_4, which is 52.2 and 8.63 times higher than that of Au/g-C_3N_4 and Cd S/Au/g-C_3N_4, respectively. The results of photoluminescence spectra, photoelectrochemical and time-resolved photoluminescence spectra indicate that the improved photocatalytic activities for Cd_xZn_(1-x)S/Au/g-C_3N_4 are due to the efficient separation of photogenerated carriers. In addition, it is noteworthy that the undesired byproducts CO and CO_2 are greatly reduced by introducing CdxZn_(1-x)S over Au/g-C_3N_4 surface. In the photocatalytic process, gluconic acid originated from the reaction of photogenerated hydroxyl radical with glucose plays a vital role on suppressing the formation of the gas byproducts. The present work will provide a new strategy to design Z-scheme photocatalysts with enhanced efficiency for water splitting along with suppressing the byproducts.

Effect of ferric and bromide ions on the formation and speciation of disinfection byproducts during chlorination

The effects of ferric ion, pH, and bromide on the formation and distribution of disinfection byproducts （DBPs） during chlorination were studied. Two raw water samples from Huangpu River and Yangtze River, two typical drinking water sources of Shanghai, were used for the investigation. Compared with the samples from Huangpu River, the raw water samples from Yangtze River had lower content of total organic carbon （TOC） and ferric ions, but higher bromide concentrations. Under controlled chlorination conditions, four trihalomethanes （THMs）, nine haloacetic acids （HAAs）, total organic halogen （TOX） and its halogen species fractions, including total organic chlorine （TOC1） and total organic bromide （TOBr）, were determined. The results showed that co-existent ferric and bromide ions significantly promoted the formation of total THMs and HAAs for both raw water samples. Higher concentration of bromide ions significantly changed the speciation of the formed THMs and HAAs. There was an obvious shift to brominated species, which might result in a more adverse influence on the safety of drinking water. The results also indicated that high levels of bromide ions in raw water samples produced higher percentages of unknown TOBr.

Disinfection byproducts in drinking water and regulatory compliance： A critical review

Disinfection by-products （DBPs） are regulated in drinking water in a number of countries. This critical review focuses on the issues associated with DBP regulatory compliance, including methods for DBP analysis, occurrence levels, the regulation comparison among various countries, DBP compliance strategies, and emerging DBPs. The regulation comparison between China and the United States （US） indicated that the DBP regulations in China are more stringent based on the number of regulated compounds and maximum levels. The comparison assessment using the Information Collection Rule （ICR） database indicated that the compliance rate of 500 large US water plants under the China regulations is much lower than that under the US regulations （e.g. 62.2% versus 89.6% for total trihalomethanes）. Precursor removal and alternative disinfectants are common practices for DBP regulatory compliance. DBP removal after formation, including air stripping for trihalomethane removal and biodegradation for haloacetic acid removal, have gained more acceptance in DBP control. Formation of emerging DBPs, including iodinated DBPs and nitrogenous DBPs, is one of unintended consequences of precursor removal and alternative disinfection. At much lower levels than carbonaceous DBPs, however, emerging DBPs have posed higher health risks.