Formation Of Disinfection By-products Research Articles

Laboratory tests of the stability of disinfectants for different quality of water

The last water treatment process is disinfection and it has two purposes. The main purpose of disinfection is to kill or inactivate pathogens. A secondary purpose is to provide a residual disinfectant concentration in drinking water and to prevent microbial growth in water distribution systems. Although most pathogens (99 to 99.9%) are removed by coagulation, flocculation, sedimentation, and filtration, disinfection is a critical process for protecting the public from waterborne infections. Common disinfectants include chlorine gas, sodium hypochlorite, chloramines, chlorine dioxide, ozone and ultraviolet radiation. Each disinfection method has its advantages and disadvantages. Among the disadvantages of using sodium hypochlorite, in addition to the formation of disinfection by-products, the stability of the used agent is also important. Laboratory tests of the stability of disinfectants were carried out in drinking water of different quality depending on the pH value, water temperature and total water mineralization at different contact time in water (from 0 to 48 hours). To monitor the stability of disinfectants, chlorine-based disinfectants were selected, namely sodium hypochlorite prepared in the classic way and by electrolysis of brine. The stability of these disinfectants was verified in low-mineralized surface water from the Turček water reservoir, medium mineralized groundwater from the Sihot’ water source and groundwater from a private well in village of Ol’dza with highly mineralized water. Active chlorine doses in the range of 0.28-0.35 mg/L were used to verify the stability of sodium hypochlorite prepared in the classic way in selected drinking waters. When verifying the stability of sodium hypochlorite prepared by electrolysis of brine, doses of active chlorine in the range of 0.25-0.30 mg/L were applied. When verifying the stability of sodium hypochlorite produced by two different methods (chemical process, brine electrolysis), the dependence of the increasing stability of these disinfectants with a decrease in pH value and water temperature was demonstrated. The dependence of chlorine stability is significantly influenced by the water temperature, less so by the pH value of the water. Reaction kinetics of 0th, 1st and 2nd order was studied for better understanding of this process.

Comparison of three sorbents for thin film solid phase microextraction of haloacetic acids from water.

Water disinfection inevitably leads to disinfection byproduct formation, such as haloacetic acids. Many disinfection byproducts reportedly have adverse health effects and, in many instances, including four haloacetic acids, are classified as potential carcinogens. As the global awareness of these compounds increases, more regulatory bodies include certain disinfection byproduct groups in their regulations. Rugged, fast, and cheap analytical quantification methods are therefore crucial. In this paper, a thin film extraction method for haloacetic acids is outlined. Thin films were synthesized in-house using a spin coating procedure, which allowed for easy adjustment of the sorbent choice and film geometry. PDMS, Carboxen®, and HLB were of interest and their extraction potential for HAAs from spiked water was tested in three film variations. PDMS films impregnated with HLB or Carboxen® improved the extraction drastically compared to PDMS films. Specifically, HLB impregnated films achieved excellent extraction efficiencies for tri-substituted analytes (51% for BDCAA, 77% for CDBAA, and 92% TBAA), which are often present at extremely low concentrations in water. In addition to the extraction experiment, a computational model was applied to compare PDMS and HLB. Trends observed in the computational data reflected in the experimental results, showing the validity of the model and confirming that physisorption through hydrogen bonding was mainly responsible for successful extraction.

Peracetic acid to reduce disinfection by-product formation in drinking water

A 5 mg L−1 PAA/H2O2 (mixture) pre-oxidation decreased the DBP formation potential by up to 40%.

Suların Klorla Dezenfeksiyonunda Trihalometan Oluşumuna Hümik Asit ve Bromürün Etkisi

Chlorination is one of the most important methods used in water disinfection. Chlorine reacts with natural organic substances in water and causes the formation of disinfection byproducts that might cause health problems. The predominant by-product of chlorination is trihalomethanes. Humic substances, which make up the majority of natural organic substances, are the primary precursors of trihalomethanes. In this study, the effect of different doses of chlorine on the formation of chloroform, bromodichloromethane, dibromochloromethane and bromoform in the presence of natural organic matter and bromide in drinking water was evaluated. Artificial raw water samples prepared with the addition of 2, 3 and 5 mg/L humic acid representing natural organic matter were subjected to chlorination at doses of 1, 2 and 3 mg/L and analysed on the 0th, 3rd and 7th day. The only trihalomethane formed was chloroform with a concentration of 20.52-131.13 μg/L. Increased humic acid and chlorine levels resulted in increased chloroform content. Free chlorine in the water caused chloroform formation to continue even on the 7th day. Accordingly, the amount of chloroform formed increased with the contact time. While the chlorine dose was constant, increased humic acid resulted in decreased free chlorine. To evaluate the effect of bromide on trihalomethane formation, 200 μg/L bromide was added to 2 mg/L humic acid containing water, and 1 mg/L and 2 mg/L chlorination was applied. At the end of the chlorination process in bromide-free waters, only 23.46-41.90 μg/L of chloroform was formed. In the presence of bromide, chloroform, bromodichloromethane, dibromochloromethane and bromoform were formed and the total trihalomethane level increased to 50.03-85.59 μg/L. While the ratio of brominated trihalomethane increased, the amount of chlorinated species decreased.

Degradation kinetics and disinfection by-products formation of benzophenone-4 during UV/persulfate process

ABSTRACT The degradation kinetics, reaction pathways, and disinfection by-products formation of an organic UV filter, benzophenone-4 (BP4) during UV/persulfate oxidation were investigated. BP4 can hardly be degraded by UV alone, but can be effectively decomposed by UV/persulfate following pseudo-first order kinetics. BP4 degradation rate was enhanced with increasing persulfate dosage and decreasing pH from 8 to 5. However, the degradation rate of BP4 at pH 9 was higher than that at pH 8 because of the presence of phenolic group in BP4 structure. and were confirmed as the major contributors to BP4 decomposition in radical scavenging experiments, and the second-order rate constants between and BP4 as well as those between and BP4 were estimated by establishing and solving a kinetic model. The presence of and humic acid inhibited the decomposition of BP4, while promoted it. The mineralisation of BP4 was only 9.1% at the persulfate concentration of 50 μM. Six degradation intermediates were identified for the promulgation of the reaction pathways of BP4 during UV/persulfate oxidation were proposed as a result. In addition, the formation of DBP in the sequential chlorination was evaluated at different persulfate dosages, pH values, and water matrix. The results of this study can provide essential knowledge for the effective control of DBP formation with reducing potential hazard to provide safe drinking water to the public.

Risk assessment when consuming drinking water treated with chlorine dioxide and risk management in EU countries and Ukraine to protect public health

The purpose of the work was to conduct a comparative scientific analysis of the main approaches to risk assessment and risk management to prevent the negative impact of drinking water on public health when treating it with chlorine dioxide in EU countries and Ukraine. The main risk to the population's health arising when consuming drinking water, is the risk of its microbiologicall contamination. Microbiological contamination of drinking water corresponds to a high risk, while the formation of disinfection byproducts in drinking water is an average risk. The regulatory documents of all EU countries take into account the requirements of Directive 2020/2184/EU regarding the content of chlorites and chlorates in drinking water when treating it with chlorine dioxide, while in Denmark, Slovakia, Hungary, Spain, and France, a risk-oriented approach to the safety of drinking water forced to introduce stricter standards to these indicators (as mandatory, recommended or those, which can be temporarily raised).The scientific analysis of the regulation of drinking water quality in the EU countries and Ukraine, as well as field studies on the safety and quality of drinking water at the Dnipro water station in the city of Kyiv, allowed to assess the risks of drinking water hazards and became the basis for raising the issue of revising or canceling the unscientific standard for chlorine dioxide in drinking water of the distribution network (≥0.1 mg/l), revising the strict standard for chlorites (≤0.2 mg/l), as well as control of drinking water quality by the content of chlorates following the requirements of European legislation. When appointing the organizers, executors, and decision-makers regarding risk assessment, similar approaches were implemented in various EU countries; in the documents of many countries, there are references to the relevant scientific institutions and the functions assigned to them. Under such conditions, the working programs of production control over drinking water quality and modernization plans can be adapted to the relevant water supply system and modern realities.

Direct conversion of cyano group to cyanogen chloride and dichloroacetonitrile in the UV/chlorine process

The combined application of chlorination and UV irradiation has the potential to yield important benefits in water treatment. However, much of the fundamental chemistry that governs the behavior of UV/chlorine systems have not been well defined. Cyano-containing pesticides (CNPs) are widely used in agriculture and inevitably enter surface waters and other aquatic environments. In this study, twenty CNPs and their intermediates were investigated to evaluate the formation of disinfection byproducts under chlorination and UV/chlorine systems. It was found that UV/chlorine can significantly enhance the generation of cyanogen chloride (CNCl) and dichloroacetonitrile (DCAN) compared to chlorination alone. The CNCl and DCAN concentrations increased from an average of 0.13 and 0.12 μM during the chlorination alone to 0.85 and 0.41 μM, respectively, when UV254 light was introduced. The maximum yields of CNCl and DCAN could reach 31.8 % and 7.7 %, respectively. Both the photo-induced •OH and •Cl played a key role in the generation of CNCl and DCAN. Additionally, higher yields of total CNX were observed in the UV/chlorine system in the presence of bromide. Similar results were obtained in the treatment of actual water samples, in which the concentrations of CNCl and DCAN increased by orders of magnitude under UV/chlorine treatment compared to the chlorination alone. The results showed that the cyano group of organic pollutants has a higher potential to be directly converted to toxic CNCl and DCAN under UV/chlorine treatment. The inclusion of this basic chemistry will deepen our understanding of UV/chorine water treatment technologies.

Characterization of dissolved organic matter and disinfection by-product formation potentials during the metalimnetic oxygen minimum in deep reservoirs

Abstract Dissolved oxygen (DO) is strongly linked to the origin and transformation of dissolved organic matter (DOM) in reservoirs. During metalimnetic oxygen minimum (MOM), the reservoir is divided into four regions: surface oxygen-rich (SOR), middle anoxic (MA), middle oxygen (MO), and bottom anoxic (BA). This article focuses on the link between DOM and disinfection by-product (DBP) precursors and DO in reservoirs. The DOM in SOR was characterized by the highest proportion of protein-like components, lowest humification and aromaticity, which was indicated mainly affected by algae blooms. The DOM in MO was affected by terrestrial, with the highest ratio of humic and fulvic-like fluorescent and the highest extent of humification and aromaticity. The humification and aromaticity in MA and BA were between MO and SOR water. Moreover, according to redundancy analysis, the dominant DBPs, including trichloromethane and haloacetic acid precursors, mainly originate from a high degree of humification and aromaticity in DOM, suggesting that the terrestrial-derived DOM was a dominant source of DBP precursors. This study provides the distribution in DOM characteristics and its driven DBPs in the Sanhekou Reservoir during the MOM, which is of great significance for selecting appropriate water intake regions for subsequent water treatment.

Comparative effectiveness of sequential and synergistic (VUV/)UV and chlorine disinfection on DBPs and humic acid reduction

The widespread use of chlorine during disinfection has led to the problems of disinfection by-products (DBPs). Recently, the combination of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm) with chlorine has been considered a promising strategy to mitigate the formation of DBPs. This study systematically evaluated the efficacy of six different disinfection methods in abating humic acid (HA), a common precursor of DBPs (UV-Chlorine, VUV/UV-Chlorine, Chlorine-UV, Chlorine-VUV/UV, UV/Chlorine, and VUV/UV/Chlorine). Under 40 mJ/cm2 UV fluence and 3 mg/L chlorine dose, the synergistic processes yielded DBP levels below 20 μg/L, whereas sequential disinfection resulted in DBP levels exceeding 100 μg/L. Additionally, there was no significant difference in the formation of DBPs between the two methods of chlorination followed by irradiation. However, for irradiation followed by chlorination, the addition of VUV led to an increase of 50 μg/L in trihalomethanes (THMs). As the irradiation time increased, the inclusion of VUV demonstrated enhanced control of DBP levels in the sequential disinfection process. Moreover, compared to UV/Chlorine, at 13 mg/L chlorine dose in VUV/UV/Chlorine process, the inclusion of VUV expedited the appearance of peak DBPs by two minutes and reduced the peak value by 25.6 %, but the DBP yield was 12.9 times higher than that at a chlorine dose of 3 mg/L. This study, comparing six combination disinfection methods, will provide deeper insights into precursor abatement and DBP control during drinking water disinfection.

Effects of ozone dose on brominated DBPs in subsequent chlor(am)ination: A comprehensive study of aliphatic, alicyclic and aromatic DBPs

Ozone‒chlor(am)ine is a commonly used combination of disinfectants in drinking water treatment. Although there are quite a few studies on the formation of some individual DBPs in the ozone‒chlor(am)ine disinfection, an overall picture of the DBP formation in the combined disinfection is largely unavailable. In this study, the effects of ozone dose on the formation and speciation of organic brominated disinfection byproducts (DBPs) in subsequent chlorination, chloramination, or chlorination‒chloramination of simulated drinking water were investigated. High-molecular-weight, aliphatic, alicyclic and aromatic brominated DBPs were selectively detected and studied using a powerful precursor ion scan method with ultra performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (UPLC/ESI-tqMS). Two groups of unregulated yet relatively toxic DBPs, dihalonitromethanes and dihaloacetaldehydes, were detected by the UPLC/ESI-tqMS for the first time. With increasing ozone dose, the levels of high-molecular-weight (m/z 300–500) and alicyclic and aromatic brominated DBPs generally decreased, the levels of brominated aliphatic acids were slightly affected, and the levels of dihalonitromethanes and dihaloacetaldehydes generally increased in the subsequent disinfection processes. Despite different molecular compositions of the detected DBPs, increasing ozone dose generally shifted the formation of DBPs from chlorinated ones to brominated analogues in the subsequent disinfection processes. This study provided a comprehensive analysis of the impact of ozone dose on the DBP formation and speciation in subsequent chlor(am)ine disinfection.

Chlorination of Emerging Contaminants for Application in Potable Wastewater Reuse: Disinfection Byproduct Formation, Estrogen Activity, and Cytotoxicity.

With increasing water scarcity, many utilities are considering the potable reuse of wastewater as a source of drinking water. However, not all chemicals are removed in conventional wastewater treatment, and disinfection byproducts (DBPs) can form from these contaminants when disinfectants are applied during or after reuse treatment, especially if applied upstream of advanced treatment processes to control biofouling. We investigated the chlorination of seven priority emerging contaminants (17β-estradiol, estrone, 17α-ethinylestradiol, bisphenol A (BPA), diclofenac, p-nonylphenol, and triclosan) in ultrapure water, and we also investigated the impact of chlorination on real samples from different treatment stages of an advanced reuse plant to evaluate the role of chlorination on the associated cytotoxicity and estrogenicity. Many DBPs were tentatively identified via liquid chromatography (LC)- and gas chromatography (GC)-high resolution mass spectrometry, including 28 not previously reported. These encompassed chlorinated, brominated, and oxidized analogs of the parent compounds as well as smaller halogenated molecules. Chlorinated BPA was the least cytotoxic of the DBPs formed but was highly estrogenic, whereas chlorinated hormones were highly cytotoxic. Estrogenicity decreased by ∼4-6 orders of magnitude for 17β-estradiol and estrone following chlorination but increased 2 orders of magnitude for diclofenac. Estrogenicity of chlorinated BPA and p-nonylphenol were ∼50% of the natural/synthetic hormones. Potential seasonal differences in estrogen activity of unreacted vs reacted advanced wastewater treatment field samples were observed.

Comparative formation of chlorinated and brominated disinfection byproducts from chlorination and bromination of amino acids

Amino acids are the main components of dissolved organic nitrogen in algal- and wastewater-impacted waters, which can react with chlorine to form toxic halogenated disinfection by-products (DBPs) in the disinfection process. In the presence of bromide, the reaction between amino acids and secondarily formed hypobromous acid can lead to the formation of brominated DBPs that are more toxic than chlorinated analogues. This study compares the formation of regulated and unregulated DBPs during chlorination and bromination of representative amino acids (AAs) (e.g., aspartic acid, asparagine, tryptophan, tyrosine, and histidine). In general, concentrations of brominated DBPs (trihalomethanes, haloacetonitriles, and haloacetamides, 24.9–5835.0 nM) during bromination were higher than their chlorinated analogues (9.3–3235.3 nM) during chlorination. This indicates the greater efficacy of bromine as a halogenating agent. However, the formation of chlorinated haloacetic acids during chlorination was higher than the corresponding brominated DBPs from bromination. It is likely that an oxidation pathway is required for the formation of haloacetic acids and chlorine is a stronger oxidant than bromine. Moreover, chlorine forms higher levels of haloacetaldehydes (74.4–1077.8 nM) from amino acids than bromine (1.0–480.2 nM) owing to the instability of brominated species. The DBP formation yields depend on the types of functional groups in the side chain of AAs. Eight intermediates resulting from chlorination/bromination of tyrosine were identified by triple quadrupole mass spectrometer, including N-chlorinated/brominated tyrosine, 3-chloro/bromo-tyrosine, and 3,5-dichloro/dibromo-tyrosine. These findings provided new insights into the DBP formation during the chlorination of algal- and wastewater-impacted waters with elevated bromide.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10−13 M and the cumulative exposure of HO• reached 5.52 × 10−10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg−1 s−1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

DOM and DON transformation in full-scale wastewater treatment plants: Comparison of autotrophic and heterotrophic nitrogen removal units

There is limited knowledge regarding the differences and relationships in molecular composition between dissolved organic matters (DOM) and dissolved organic nitrogen (DON) in autotrophic and heterotrophic nitrogen removal processes. In this study, the composition of DOM and DON during two full-scale wastewater treatment plants (WWTPs), an autotrophic nitrogen removal with partial nitrification-anammox process (PN/A) and a heterotrophic nitrogen removal with anaerobic/anoxic/oxic process (A2O), were systematically investigated by using ultraviolet–visible spectroscopy, Excitation-Emission Matrix (EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results indicated that both PN/A and A2O resulted a decrease in molecular diversity and bio-availability of DOM. However, there were distinct variations in DON between the two processes. In PN/A, transformation of DOM and DON was found to be coupled, while there was a lack of correlation observed between DOM and DON in A2O. Pearson correlation analysis revealed that transformation of DOM and DON in WWTPs was associated with microbial roles. During biotreatment, PN/A exhibited a higher metabolic capacity for degrading high bio-available and high aromatic compounds compared to A2O. The autotrophic nitrogen removal unit in PN/A resulted in an increase in molecular weight (MW) of DON, as well as a decrease in bio-availability and unsaturation degree of DON. Therefore, autotrophic nitrogen removal unit may have a positive influence on control of eutrophication and disinfection by-products (DBPs) formation. This study improved the understanding of molecular composition and relationship between DOM and DON, as well as microbial roles on DON transformation within autotrophic and heterotrophic nitrogen removal processes.

Cocamidopropyl betaine - a potential source of nitrogen-containing disinfection by-products in pool water.

Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8µg L-1) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1µg L-1. Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown.

Trihalomethanes in developed and developing countries.

The reactions between natural organic matter, anthropogenic contaminants, ions, and disinfectants lead to the formation of disinfection by-products (DBPs) such as trihalomethanes (THMs) in drinking water. The formation of THMs is strongly related to the chlorination of water. The study's central objective was to compare the concentration of THMs in twenty developed and developing countries and their disinfection techniques. The THM concentration in 11 developed and 9 developing countries ranged from 0.5 µg/L (Germany) to 215 µg/L (Russia) and 3 µg/L (China) to 439.2 µg/L (Bangladesh), respectively. The developed country has partially succeeded in reducing THM concentration in drinking water, whereas significant steps are needed in developing countries to reduce the existing high THM concentration. The concentration of THMs in water varies among these countries because of the different water sources, water quality, environmental conditions, and efficiency of water treatment technologies. A meaningful relationship has been observed between the properties of water and the THM formation. The use of chemical disinfectants will result in new forms of DBPs that are undesirable due to their carcinogenic and mutagenic effects on human health. The DBP guidelines by various national and international agencies have helped to control and manage the THM concentration in drinking water. However, these regulatory standards are not continuously monitored. Therefore, the formation of these compounds should be prevented either by removing THMs forming precursors or by using an integrated approach for controlling THM formation by implementing advanced water treatment technology. Extensive research is desirable in domains like THM minimization strategies which are easy to deploy, scalable, and cost-effective.

Role of Copper in Disinfection Byproduct Formation Derived from Algal Organic Matter: Based on Two-Dimensional Correlation Spectroscopy Analysis

Role of Copper in Disinfection Byproduct Formation Derived from Algal Organic Matter: Based on Two-Dimensional Correlation Spectroscopy Analysis

Enhancing biological dissolved organic nitrogen removal in landfill leachate wastewater: The role of sodium acetate co-metabolism

Dissolved organic nitrogen (DON) comprises approximately 25% of dissolved nitrogen in landfill leachate wastewater (LLW), posing potential risks such as stimulating algal growth and forming disinfection by-products if not treated properly. While DON characterization and removal by physicochemical methods in wastewater treatment systems have been examined, biological strategies for effective DON removal remain less developed. This study explores the influence of sodium acetate addition during denitrification process on LLW DON removal. With sodium acetate addition (Stage I), we achieved 99% ammonia removal, 94% total inorganic nitrogen (TIN) removal, and 45% DON removal. Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) results suggested the majority of sulfur-containing DON molecules were eliminated in Stage I. Conversely, in the absence of sodium acetate (Stage II), while 99% ammonia removal was maintained, TIN removal dropped to around 10%, and DON concentrations (largely sulfur-containing DON) increased by approximately 22%. Cycle tests revealed similar DON reductions in the aerobic phase across both stages, whereas in the anoxic phase, DON concentrations decreased in Stage I but increased in Stage II. Functional gene prediction indicated higher expression of decarboxylase and deaminase genes in Stage I compared to Stage II. Consequently, this study posits that sodium acetate addition enhances DON removal, potentially via co-metabolism.

Influence of Application Method on Disinfectant Byproduct Formation during Indoor Bleach Cleaning: A Case Study on Phenol Chlorination

Influence of Application Method on Disinfectant Byproduct Formation during Indoor Bleach Cleaning: A Case Study on Phenol Chlorination

Release of biochar-derived dissolved organic matter and the formation of chlorination disinfection by-products: Effects of pH and chlorine dosage

Transformation, fragmentation, dissolution, and oxidation of biochar are inevitable in the environment, which will undoubtedly accelerate the release of biochar-derived dissolved organic matter (BDOM) into various water bodies. In addition, biochar may affect disinfection by-products (DBPs) during water treatment and subsequent disinfection. In this study, biochars were derived at three selected pyrolysis temperatures (350 °C, 500 °C, and 650 °C) from rice husk, wheat straw, and shrimp shell, and BDOM was extracted from biochar-derived in artificial seawater and ultrapure water. The TOC analyzer results showed that the concentrations of three BDOM decreased with increasing pyrolysis temperature. The BDOM derived from rice husk biochar and wheat straw biochar in seawater was lower than that in ultrapure water, while that of shrimp shell biochar showed an opposite trend, being released in seawater at nearly twice the extent of that in ultrapure water at 350 °C. Moreover, BDOM showed a catalytic effect on chlorination, and GC analysis showed that the concentrations of its DBPs were affected by pH. The concentration of halogenated acetic acid reached the highest value (54.51 μg/L) in weak acidic environment, while the concentrations of trihalomethane and halogenated acetonitrile had the highest values (23.63 and 47.53 μg/L, respectively) in alkaline conditions. The concentrations of all the three DBPs were lowest under neutral pH conditions. In addition, the volatile halogenated DBPs such as dichloroacetone and trichloroacetone were easily hydrolyzed under alkaline conditions. Therefore, it is something be aware of the release of BDOM and the effects of chlorination DBPs when biochar is used for water treatment or water purification.