Disinfection By-product Formation Potential Research Articles

Response mechanism of soil leachate and disinfection by-product formation to extreme precipitation events under continuous drought scenario

In this study, a rainfall simulation device was employed to investigate the response mechanism of soil leachate and disinfection by-products formation potential (DBPsFP) to extreme precipitation events. The results revealed that the aromaticity of dissolved organic matter (DOM) and the concentration of hydrophobic DOM containing aromatic carbon groups in leachate decreased with rising temperature. The humification degree of DOM decreased at 25 °C (99 mm/h), while the humification degree and protein-like level of DOM increased under high temperatures droughts (45 °C and 65 °C). Higher temperatures resulted in the leach of more microbial-derived humus and low molecular phenolic compounds from soil and broadened the range of molecular weight distribution. Increasing temperature increased DBPsFP and DBPs species and caused the precursors of haloacetic acids (HAAs) in leachate to become more hydrophobic, while the precursors of trihalomethanes (THMs) became more hydrophilic. Most importantly, the increased temperature attenuated the rainfall-mediated dilution of organic pollutant concentration, and temperature has a more significant effect than extreme rainfall in DOM abundance and the formation potential (or species) of DBPs. The results help to better understand the impact of climate change on the physicochemical processes of water quality.

Using machine learning to trace the pollution sources of disinfection by-products precursors compared to receptor models

To increase the efficiency of managing backup water resources, it is critical to identify and allocate pollution sources. Source apportionment of dissolved organic matter (DOM) was investigated in our work. Parallel factor analysis (PARAFAC) and the Spearman correlation analysis were used for source identification. After that, a newly hybrid model applying the fuzzy c-means and support vector regression (FCM-SVR) was employed for source apportionment compared to receptor models. The results demonstrated that the FCM-SVR model exhibited excellent generalization, and only required standardization and normalization as pre-processing steps for dataset. According to the results, microbial sources played a key role (28.1 %) in the formation potential of disinfection byproducts (DBPFPs). Additionally, shipping marine sources exhibited a substantial contribution (21.2 %) to DBPFPs. The prediction accuracy of DBPFPs was matched or exceeded receptor models, and the R2 of DOC (0.884) was significantly high. Therefore, we recommend the FCM-SVR model combined with PARAFAC to trace the source of DBPFPs as its significant effectiveness in source identification, source apportionment, and prediction accuracy, possessing the potential for further applicability in tracking more organic compounds. Environmental implicationThe disinfection byproducts precursors in water sources, which were thought to be hazardous materials in this study, are proved to be chlorinated into carcinogenic disinfection byproducts (DBPs) during drinking water treatment, However, the source apportionment methods of DBPs are not well developed compared to other inorganic matter, e.g., heavy metals and ammonia nitrogen. We proposed a new FCM-SVR model to trace the source of DBPs, which required easier pre-treatment and resulted a better source apportionment and prediction accuracy. As a result, it could provide a different prospect and useful management advices to trace the source of DBPs.

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%.

Synergistic disinfection effects and reduction of disinfection by-products in water treatment using magnetic quaternized cyclodextrin polymer combined with chorine disinfection process

Disinfection is vital in ensuring water safety. However, the traditional chlorine disinfection process is prone to producing toxic and harmful disinfection by-products (DBPs). The combination of quaternary ammonium polymer and the chlorine disinfection process can solve this shortcoming. Currently, research on the control of DBPs through the combined process is not systematic and the control effect between reducing the dosage of disinfectants and DBPs remains to be studied. Quaternized cyclodextrin polymers have attracted increasing attention due to their excellent adsorption and antibacterial properties, but their synergistic effect with chlorine disinfection is still unclear. In this study, a magnetic quaternized cyclodextrin polymer (MQCDP) is synthesized in an ionic liquid green system, and a combined process of MQCDP treatment and chlorine disinfection is established. The disinfection performance of the combined process on the actual water body along with its reducing effect on the amount of chlorine disinfectant as well as the trihalomethanes (THMs) and haloacetic acids (HAAs) DBPs are explored. MQCDP has a porous structure with a specific surface area of 825 m2 g−1 and is easily magnetically separated. MQCDP can remove most of the natural organic matter (UV254 absorbance decreased by 97 %) in the water at the dosage of 1 g L−1 and kill bacteria with a sterilization rate of 85 %. Compared with disinfection using chlorine alone, the combined process has higher disinfection efficiency and significantly reduces the amount of disinfectant used. A concentration of 5 mg/L of NaClO was needed to meet the standard by chlorine disinfectant alone, while only 2 mg/L of NaClO can meet the standard for the combined process, indicating 60 % of the chlorine demand was reduced. More importantly, the combined process can significantly reduce the generation potential of DBPs. When 10 mg/L of NaClO is added, the THMs and HAAs generated by the combined process decreased by 65 % and 34 %, respectively, compared with the levels produced by single chlorine disinfection. The combined process can reduce the dosage of chlorine disinfectant and MQCDP can adsorb humic acid DBP precursors in raw water, thus lowering the generation of DBPs during disinfection. In summary, MQCDP has excellent separation and antibacterial ability, and its synergistic effects combined with the chlorine disinfection process are of great significance for controlling the amount of disinfectant and the formation potential of DBPs, which has potential applications in actual water treatment.

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.

Nontargeted identification of disinfection by-product precursors from soluble microbial products in municipal secondary effluent

As soluble microbial products (SMPs) can serve as precursors for disinfection by-products (DBPs), the release of SMPs from municipal secondary effluent has the potential to increase the health hazards associated with reused water. Nontargeted identification of DBPs precursors from SMPs in municipal secondary effluent was explored in the present research. The hydrophobic (HPO) fraction that constituted the major portion of the SMPs was 48.0%, and the majority of organic SMPs were composed of low molecular weight (LMW) compounds. The results showed that the HPO fraction with MW < 1 kDa component has the highest disinfection by-product formation potentials (DBPFPs). X-ray photoelectron spectroscopy (XPS) results showed that the HPO fraction with MW < 1 kDa component was mainly composed of OC–OH (40.2%) and amide/peptide N (46.7%) functional groups. This finding was in line with the results showing the highest yields of DBPFPs in terms of HAAs (haloacetic acids) and trichloroacetamide (TCAcAm). Ultra-performance liquid chromatography coupled with tandem quadrupole-time-of-flight mass spectrometry (UPLC-Q-ToF-MS) data revealed that phospholipids, fatty acids, fatty acyls-fatty amides, phosphatidylcholine, glycosides, fatty acid esters, glycolipid, and steroids were the main chemical classes in SMPs. Among these chemical classes, phospholipids containing amino acids structures and fatty acids containing carboxyl functional groups with the maximum abundance could promote the formation of HAAs. This research offers a thorough characterization of SMPs derived from municipal secondary effluent. These results enable the implementation of targeted methods to decrease the formation of DBPs by identifying potential precursors of DBPs.

Aging of polystyrene microplastics by UV/Sodium percarbonate oxidation: Organic release, mechanism, and disinfection by-product formation

The occurrence and transformation of microplastics (MPs) in environment has attracted considerable attention. However, the release characteristics of MP-derived dissolved organic matter (MP-DOM) under oxidation conditions and the effect of DOM on subsequent chlorination disinfection by-product (DBP) still lacks relevant information. This study focused on the conversion of polystyrene microplastics (PSMPs) in the advanced oxidation of ultraviolet-activated sodium percarbonate (UV/SPC-AOP) and the release characteristics of MP-DOM. The DBP formation potential of MP-DOM was also investigated. As a result, UV/SPC significantly enhanced the aging and fragmentation of PSMPs. Under UV irradiation, the fluorescence peak intensity and position of humus-like and protein-like components of MP-DOM were correlated with SPC concentration. The aging MP suspension was analyzed by gas chromatography–mass spectrometry (GC-MS), and various alkyl-cleavage and oxidation products were identified. Quenching experiments and electron paramagnetic resonance (EPR) detection confirmed that carbonate and hydroxyl radicals jointly dominated the conversion of PSMPs. The formation of DBP was related to the components of MP-DOM. Overall, these results help to understand the aging behavior of MPs in AOP. Moreover, MP-DOM released by MPs after AOP oxidation may be a precursor of DBPs, which deserved more attention.

Modeling source water disinfection byproducts formation potential using environmental variables

AbstractPredictive models of disinfection byproducts (DBPs) formation in treated drinking water have been widely used to guide operational decisions. However, very few studies have addressed the issue of managing DBPs through watershed protection programs and proactive management of water supply systems through predictive modeling of DBP formation potential in source waters. Here, we propose a two‐component, simple statistical approach to predict the formation potentials of the sum of five haloacetic acids (HAA5fp) and total trihalomethanes (TTHMfp) in source water streams using environmental variables and ultraviolet absorbance at 254 nm wavelength (UV254) as a surrogate for DBP precursors. In the first component of the model, using three feature selection regression models and cross‐validation of subsets of the selected predictors, we identified three commonly monitored variables—streamflow, soil temperature, and total phosphorus for predicting UV254. In the second component, HAA5fp and TTHMfp are predicted from UV254. The approach is successfully demonstrated for two source water streams of the New York City water supply system (R2 was 0.8, and 0.7–0.8 for the two model components). Long‐term predictions of HAA5fp and TTHMfp showed distinct seasonal patterns that are linked to differences in land uses of the two watersheds. Moreover, sensitivity analysis showed that transport processes were important in one watershed whereas production processes were more important in the other.

Effective control of DBPs formation and membrane fouling in catalytic ozonation membrane reactor for municipal wastewater reclamation

This study aimed to evaluate the performance of different ceramic membranes, namely CuMn2O4 (CMO), g-C3N4 (CN), and CuMn2O4/g-C3N4 (CMO/CN) ceramic membrane (CM), in a catalytic ozonation membrane reactor (COMR) for municipal wastewater reclamation. The results demonstrated that CMO/CM and CMO/CN/CM used in the COMR exhibited high performance in terms of flux, removal efficiency of effluent organic matter (EfOM), control of disinfection by-products formation potential (DBPs-FP), and mitigation of membrane fouling. Notably, catalytic ozonation by CMO/CM showed superior reduction in DBPs formation (40.6 % of nitrogenous DBPs, 83.4 % of halogenated hydrocarbons, 36.6 % of haloacetic acids). Furthermore, significant inhibition of both organic fouling and biofouling was observed in the COMR. The addition of O3 altered the membrane fouling mechanism from gel layer formation to intermediate blocking. Ozonation primarily reduced the physically reversible fouling while catalytic ozonation additionally mitigated physically irreversible fouling. In addition to the almost complete removal of total cells and proteins, catalytic ozonation by CMO/CM further cleaned the α-polysaccharides and β-polysaccharides on the membrane surface, resulting in a 55.3 % reduction in biofilm thickness and demonstrating strong self-cleaning properties. These findings have important implications for enhancing the overall performance and durability of COMR systems in municipal wastewater reclamation.

Effects of the nutrient inhibition on the yield of DBPFPs by Microcystis aeruginosa.

The yield of three disinfection byproduct formation potentials (DBPFPs), including trichloromethane, dichloroacetic acid and trichloroacetic acid formation potential (TCMFP, DCAAFP and TCAAFP), by Microcystis aeruginosa under the nitrate and phosphate inhibition conditions was investigated. The results showed that excessive nitrate could inhibit the growth of M. aeruginosa, but the concentration of DBPFPs in the five fractions of algal metabolites, including hydrophilic extracellular organic matter (EOM), hydrophobic EOM, hydrophilic intracellular organic matter, hydrophobic intracellular organic matter and cell debris, only decreased slightly. Accordingly, the productivity of DBPFPs by M. aeruginosa increased by approximately 40% under the nitrate inhibition condition and the increased productivity of DBPFPs mainly came from EOM. The phosphate inhibition also performed a similar pattern with a lesser extent. The nutrient inhibition did not change the proportion of these three DPBFPs, and TCMFP accounted for approximately 87% of the total DBPFPs. The inhibition could promote M. aeruginosa to secrete more metabolites. However, the cyanobacteria tended to secrete more DBPFPs under the nitrate inhibition condition, which resulted in an increased specific DBPFP, while they tended to secrete more non-DBPFPs under the phosphate inhibition condition, which resulted in a decreased specific DBPFP.

A UVA light-emitting diode microreactor for the photocatalytic degradation of humic acids and the control of disinfection by-products formation potential

Chlorination is one of the most applied technologies for drinking water disinfection. However, the generation of disinfection by-products (DBPs) in the chlorination process is threatening drinking water safety, especially when the concentration of natural organic matter (NOM) is high in source water. Climate change increases the fluctuation of NOM in source water, which further challenges water safety in small and rural communities. In this study, environmental microfluidics was introduced to a UVA-LED photocatalytic oxidation system for a rapid oxidation of NOM. The results showed that HA adsorption and degradation, and DOC degradation were more favored in low pH. At pH 5, 56.9% of HA and 58.1% of dissolved organic carbon (DOC) were removed in 3.4 min by the microreactor. DBP formation potential was efficiently reduced, with the highest reduction of THM and HAA formation potentials by 76% and 70.7%, respectively. Compared with the bottle reactor, the degradation rate constants of HA and DOC by UVA-LED microreactor were increased by 2.99 – 15.8 times, and 6.8 – 170.2 times, respectively. Homogenous irradiation and rapid mass transfer in the microreactor accelerated the inhibited oxidation of HA in acidic and base solutions and increased the apparent quantum yields of photocatalysis. Further, the microfluidic photocatalytic oxidation was much more efficient in the reduction of DPBs formation potential in a source water sample. The process was rapid and had low chemical and energy consumption. Approaches on system scale-up, system simplification, and energy conservation would increase potential of microfluidic photocatalytic oxidation in water purification for households and small communities.

DBP-FP change of biofilm in drinking water distribution system induced by sequential UV and chlorine disinfection: Effect of UV dose and influencing mechanism

The issue of biofilm-related disinfection byproducts (DBPs) in drinking water distribution system (DWDS) has garnered significant attention. This study sought to examine the changes in biofilm-originated halogenated DBP formation potential (biofilm DBP-FP) in simulated continuous-flow DWDSs subjected to sequential UV and chlorine disinfection (UV–Cl2) treatments with varying UV doses and to propose the underlying mechanism. The formation potential of trihalomethanes (THMs), haloacetic acids (HAAs), and the total organic halogen (TOX, X = Cl and Br) produced by biofilm were measured. Results showed that the biofilm TOCl-FP was at a minimum with a UV dose of 80 mJ/cm2, corresponding to the lowest amounts of protein and polysaccharides in the extracellular polymeric substances (EPS). Sphingobium, Methylobacterium, and Sphingomonas played a crucial role in protein and polysaccharide biosynthesis. Bacterial community composition characterization together with metabolic function analysis indicated that dominant bacteria varied and metabolic function shifted due to UV-Cl2 disinfection, with Alphaproteobacteria increasing in relative abundance and Bacteroidia showing the opposite trend with increasing UV doses. Correlation analysis suggested that the UV-Cl2 disinfection process led to changes in the water matrix, including organics, inorganics, bacteria, and components that provide environmental pressure for the biofilm. These changes ultimately influenced the properties of the biofilm EPS, which had a direct impact on biofilm DBP-FP.

The interaction between chromophoric dissolved organic matter and xenobiotics (bisphenols and perfluoroalkyl substances) identified by UV-vis absorption and FT-IR spectroscopy

Chromophoric dissolved organic matter (CDOM) pool is a key component in biogeochemical processes and carbon cycles in aquatic environments. However, less attention has been paid to how CDOM pool is affected by xenobiotics. Herein, we investigate bisphenols (BPs) and perfluoroalkylated substances (PFAS) interaction with pure purchased humic substances (HS; i.e., humic acid (HA), fulvic acid (FA)) and amino acid (AA; i.e., tyrosine (TYR), tryptophan (TRY)) and the riverine CDOM pool using UV–vis absorption and Fourier-transform infrared spectroscopy (FT-IR). Notably, low and high (2.5 × 10−3 and 1 mg/L) concentrations of BPs and PFAS increase dissolved organic carbon to more than 100 and 200 %, respectively. However, CDOM abundance decreased by ∼95 and ∼60 % in treatments of HA with BPs and PFAS, respectively. Furthermore, controls FA and HA, TRY and TYR had higher aromaticity values (> 2, > 8, > 0.7 and > 0.8, respectively) compared to their corresponding treatments with BPs and PFAS (< 0.5, < 1, < 0.3, and < 0.5, respectively). BPs and PFAS significantly decrease (average of -45.34 and -65.53 %, respectively) riverine CDOM abundance and aromaticity. These findings demonstrate that BPs and PFAS are important carbon sources to aquatic ecosystems. They significantly reduce CDOM abundance which will enhance UV-light penetration into the water column, and also reduce CDOM aromaticity thus, increase its degradability and hydrophilicity, but decrease its disinfection byproduct formation potential. The findings of this study provide new and useful information about the impacts of BPs and PFAS on the CDOM pool.

Total organic halogen (TOX) in drinking water: Occurrence, correlation analysis, and precursor removal during drinking water treatment

Total organic halogen (TOX) in drinking water provides a measurement of the overall organic halogenated disinfection by-products (DBPs) formed during disinfection. Yangtze River Delta is one of the regions with the highest population density, the fastest urbanization process, and the most severe water pollution in China. Collecting water samples from full-scale drinking water treatment plants (DWTPs) in this region, this study firstly surveyed TOX occurrence in drinking water. Besides, the correlation of TOX formation potential (TOXFP) and trihalomethane formation potential (THMFP) with general water quality parameters (e.g., dissolved organic carbon [DOC], UV254, and specific ultraviolet absorbance) and the removal efficiencies of TOX precursors by different water treatment processes were also investigated. TOX levels in DWTP effluents (i.e., finished water) ranged from 29 to 165 μg/L (median 67 μg/L), and those in simulated distribution system waters ranged from 101 to 276 μg/L (median 158 μg/L). There were generally higher linear regression coefficient values for raw water (R2 = 0.51–0.88) than for treated water (R2 = 0.33–0.64) in terms of the relationship between DBP formation potentials and general parameters. However, a relatively stronger correlation between THMFP and TOXFP was observed for treated water (R2 = 0.80, p < 0.001) than for raw water (R2 = 0.64, p < 0.001). The overall treatment efficiencies of investigated parameters in DWTPs generally followed the order of UV254 > DOC > TOX precursors > THM precursors. Notably, the overall removal rates of DOC and TOX precursors in summer (averaging 59 % and 54 %, respectively) were obviously higher than those in winter (averaging 39 % and 38 %, respectively), which was assumed to be related to the seasonal variation of bioactivity in sand filter. These results could expand the knowledge of TOX in drinking water, and provide valuable perspectives to water industry and DBP research.

Rainwater extracting characteristics and its potential impact on DBPs generation: A case study

Frequent extreme precipitation events due to global warming can lead to large amounts of pollutants entering source water bodies via surface runoff and wet deposition, thus posing a threat to water supply security. In order to better understand the source characteristics and leaching mechanisms of rainwater dissolved organic matter (DOM), as well as its disinfection by-products formation potential (DBPsFP) during disinfection processes, rainwater samples were collected and extracting experiments were conducted. Three components were identified in rainwater through Parallel factor (PARAFAC) analysis, which were microbial humic-like component C1 (63.1 %), protein (tryptophan-like) component C2 (28.9 %), marine or terrestrial humic-like component C3 (8.1 %). The average molecular weight of rainwater fractions was ordered: hydrophobic neutral (HON) < hydrophobic bases (HOB) < hydrophobic acidic (HOA) < hydrophilic (HIS). The HOA and HON fractions of rainwater were the dominant precursors of trihalomethanes (THMs), while the rainwater HON fraction and hydrophilic fraction were the main precursor of haloacetic acids (HAAs) and trihloroacetonitrile (TCAN), respectively. Subsoil extracts had a higher concentration of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) than topsoil extracts. Partial least squares path modeling (PLS-PM) demonstrated that the extraction temperature was the dominant factor affecting the abundance of DOM in the topsoil extracts (R2 = 0.28), while the extraction time accounted more for the abundance of fluorescence substance and physicochemical indices in the subsoil extracts (R2 = 0.23 and 0.32, respectively). These results provide key information for controlling the impacts of global warming, in particular the risk of water sources being heavily contaminated by request rainfalls.

Testing carbon structures for metal-free catalytic/photocatalytic ozonation to remove disinfection by-product formation potential

Different graphitic carbon structures were prepared and tested for catalytic and photocatalytic ozonation of the precursors of chlorination disinfection by-products to remove their disinfection formation potential (DBPFP). Commercial graphite was submitted to ball milling and two chemical treatments with ammonium nitrate or potassium oxalate to increase its surface area. Additionally, ozonation in gas phase and liquid phase were used to generate surface oxygen groups in these materials and in commercial graphene. All the carbon samples were tested and compared with commercial graphene oxide in the removal of humic acid solutions. The highest catalytic activity during the catalytic/photocatalytic ozonation of humic acid was observed for commercial graphene, ozonated graphene and for graphene oxide; however, this did not result in high DBPFP removal and the instability of the materials was demonstrated. With a moderate catalytic activity but better stability, ball-milled graphite ozonated in liquid phase, was selected for photocatalytic ozonation of real surface water leading to a high DBPFP removal at the conditions tested (88 % 5-HAAs (haloacetic acids), 70 % 4-THMs (trihalomethanes), 70 % AOX (adsorbable organic halides); conditions: semi-batch experiments; 0.5 L volume; 5 mg L−1 O3; Qg = 10 L h−1; DOC0 = 5 mg L−1; pH = 7.8; 180 min under simulated solar radiation with average irradiance 580 W m−2).

Evaluation of the DBP formation potential of biocides and identification of knowledge gaps in environmental risk assessment

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

Impact of ozonation on disinfection byproducts formation from phenylalanine during chlorination

As a strong oxidizing agent, ozone is used in some water treatment facilities for disinfection, taste and odor control, and removal of organic micropollutants. Phenylalanine (Phe) was used as the target amino acid to comprehensively investigate variability of disinfection byproducts (DBPs) formation during chlorine disinfection and residual chlorine conditions subsequent to ozonation. The results showed that subsequent to ozonation, the typical regulated and unregulated DBPs formation potential (DBPsFP), including trichloromethane (TCM), dichloroacetonitrile (DCAN), chloral hydrate (CH), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and trichloroacetamide (TCAcAm) increased substantially, by 2.4, 3.3, 5.6, 1.2, 2.5, and 6.0 times, respectively, compared with only chlorination. Ozonation also significantly increased the DBPs yield under a 2 day simulated residual chlorine condition that mimicked the water distribution system. DBPs formations followed pseudo first order kinetics. The formation rates of DBPs in the first 6 hr were higher for TCM (0.214 hr−1), DCAN (0.244 hr−1), CH (0.105 hr−1), TCAcAm (0.234 hr−1), DCAA (0.375 hr−1) and TCAA (0.190 hr−1) than thereafter. The peak DBPsFP of TCM, DCAN, CH, TCAcAm, DCAA, and TCAA were obtained when that ozonation time was set at 5–15 min. Ozonation times > 30 min increased the mineralization of Phe and decreased the formation of DBPs upon chlorination. Increasing bromine ion (Br−) concentration increased production of bromine- DBPs and decreased chlorine-DBPs formation by 59.3%–92.2% . Higher ozone dosages and slight alkaline favored to reduce DBP formation and cytotoxicity. The ozonation conditions should be optimized for all application purposes including DBPs reduction.

Adapting direct filtration to increasing source water dissolved organic carbon using clarification and granular activated carbon

AbstractChanging source water quality namely through increasing natural organic matter (NOM) concentration challenges surface water treatment, especially direct filtration. We conducted a pilot‐scale assessment of various adaptation strategies (e.g., clarification, granular activated carbon [GAC] filtration) for direct filtration facilities under the stress of rising NOM levels. Recognizing that changing source water can impact broader aspects of treatment, we considered the implications of Fe and Mn removal via KMnO4 pre‐oxidation. GAC media showed promise as an adaptation strategy, providing ~60% removal of dissolved organic carbon (DOC), and a significant reduction in disinfection by‐product formation potential (DBPfp). However, KMnO4 pretreatment showed limited Mn and Fe removal, and filters with GAC media released dissolved Mn at up to ~30% of prefilter levels. These data suggest that using GAC may come with the risk of poor Mn removal performance if Mn is not removed during pretreatment. This work highlights the complexities anticipated under emerging climate pressures and emphasizes the need for comprehensive treatment solutions that consider factors beyond NOM.

Removal of Microcystis aeruginosa and its extracellular organic matters by using covalently bonded coagulant: An alternative choice in enhanced coagulation for algae-polluted water treatment

High coagulants dosage, Al or Fe residual, unstable flocs, and extracellular organic materials (EOM) released from cells cannot be avoided by using traditional Al or Fe based coagulants in algae removal. Thus, a novel covalently bonded coagulant poly aluminum ferrous chloride/cationic polyacrylamide (CAFM) was developed. The algae and EOM removal performance and mechanisms were investigated in current research. Al and Fe residual, cell integrity, and compactness of flocs were analyzed after coagulation. Furthermore, the disinfection by-products formation potential (DBPFP) and economics was also figured out to confirm the advantage of using CAFM. Results showed that 95.01% of turbidity and 99.3% of OD686 were effectively removed by using CAFM at 6 mg/L. Moreover, lower breakage probability of algae cells and denser flocs were realized by using CAFM compared to common used Al or Fe coagulants. In addition, lower Al and Fe residual and lower DBPFP were confimed in CAFM coagulation. DFT (Density functional theory) and ESP (Electrostatic Potential) results showed CAFM could combine bEOM (bonded extracellular organic matter) and dEOM (dissolved extracellular organic matter) through H-bond from Al atom in the covalent bond. Due to the introduction of various functional groups of different coagulants, charge neutralization and adsorption ability contributed to treating algae-containing water.