Disinfection By-product Formation Potential Research Articles

Effects of MPUV/chlorine oxidation and coexisting bromide, ammonia, and nitrate on DBP formation potential of five typical amino acids

Disinfection byproduct (DBP) formation is a potential concern with regard to MPUV/Cl2 application in water treatment. In this study, five typical amino acids (AAs) were selected to investigate their DBP alteration during short-term medium pressure (MP) UV/chlorine oxidation following post-chlorination relative to parallel dark controls. The five selected AAs include two potent DBP precursors (aspartic acid and tryptophan), one modest precursor (asparagine) and two poor precursors (phenylalanine and proline). MPUV/chlorine increased the total DBP formation and DBP-associated cytotoxicity of the two poor precursors phenylalanine (Phe) and proline (Pro) as well as their chlorine demands. Conversely, DBP formation and DBP-associated cytotoxicity of the three modest-to-potent DBP precursors showed the opposite changing trends due to MPUV/Cl2 oxidation. The two aromatic AAs (tryptophan and phenylalanine) were more readily to be affected by MPUV/Cl2 oxidation especially at acidic pH condition. Conversely, DBP formation and DBP-associated cytotoxicity of the three modest-to-potent precursors showed the opposite changing trends due to MPUV/Cl2 oxidation. Among the measured DBPs, the absolute formation potential changes of haloacetic acids and haloacetonitriles were the most prominent. Presence of bromide increased the trihalomethane formation potential of five AAs. Ammonia-spiked samples resulted in notably higher chlorine demands but slightly reduced DBPFP. Photonitration caused increased haloacetonitrile and trichloronitromethane formation but lower overall DBP formation potential and DBP-associated cytotoxicity. Results indicated that increased DBP formation of unreactive aromatic AAs may be problematic with respect to MPUV/Cl2 application, while the presence of inorganic ions may not contribute to further increase in calculated cytotoxicity of measured DBPs.

Quantitative and qualitative characteristics of dissolved organic matter derived from biochar depending on the modification method and biochar type

With the increasing utilization of biochar (BC), various modification methods have been developed; the evaluation of the environmental impact of modified BC is insufficient. In this study, three types of BC (rice husk, wood chip, and mixture) were modified through five different methods (oxidation, acidification, alkalinization, and impregnation of MnOx and FeOx), and the quantitative and qualitative characteristics of modified BC derived from dissolved organic matter (DOM) were evaluated. Quantitative analysis revealed that the yield of dissolved organic carbon (DOC) derived from modified BC was significantly lower than from BCraw, suggesting that DOM derived from BC was reduced following the modification of BC. In wood BC, the DOC yield was different from that of other types of BC, confirming that the quantitative characteristics of released DOC from modified BC depend on its type. DOM derived from BCoxidic, BCalkaline, and BCMnOx was characterized by highly condensed aromatic humic-like substances, with high trihalomethane and haloacetic acid formation potential. In contrast, DOM from BCacidic and BCFeOx showed a low degree of humification and disinfection by-product formation potential, suggesting that the qualitative properties and environmental impact of BC-derived DOM differ depending on the modification method. Overall, our findings extend our understanding of environmental impact and differences in BC-derived DOM depending on the BC types and modification methods.

Characteristics and chlorine reactivity of biochar-derived dissolved organic matter: Effects of feedstock type and pyrolysis temperature

Increasing biochar application worldwide may release more biochar-derived dissolved organic matter (BDOM) to the source water for drinking water supply. However, it is unclear how feedstock types and pyrolysis temperatures for biochar production would affect the characteristics and chlorine reactivity of BDOM. Here, we studied the spectroscopic characteristics of BDOM pyrolyzed from pine needle, wheat straw, walnut shells, alfalfa, pig manure, and sludge derived biochars at 300, 500, and 700 °C, as well as the formation potential of disinfection byproducts (DBPs) and their bulk toxicity after BDOM chlorination. The N/C ratio of biochar was higher for N-rich than C-rich feedstocks. Optical analyses indicated that BDOM aromaticity was highest at 700 °C, while the impact of pyrolysis temperature on the molecular weight of BDOM varied greatly among feedstocks. Increasing pyrolysis temperature caused consistently decreased BDOM reactivity toward haloketone formation but did not show consistent impacts on the other DBPs. Among feedstocks, the N-rich sludge showed the highest specific haloacetonitrile formation potential of BDOM at any given pyrolysis temperature. The DBP formation potential from biochar was consistently highest at 300 °C and was higher for N-rich than C-rich feedstocks. The microtoxicity of DBP mixture was highest for the BDOM derived from sludge produced at 300 °C. This study highlights the high variations in characteristics and chlorination reactivity of BDOM with varying feedstocks and pyrolysis temperatures, which implies that more attention should be paid to the environmental impacts of the intensive application of low-temperature biochar from N-rich feedstock such as sludge.

Drivers of variability in disinfection by-product formation potential in a chain of thermally stratified drinking water reservoirs

Increasing hydraulic residence time (HRT) along a chain of interconnected reservoirs enhances the formation potential of carbonaceous disinfection by-products (DBPs) and reduces the formation potential of nitrogenous DBPs, particularly N-nitrosodimethylamine (NDMA).

The Formation Potential of Disinfection By-Products of Ti3c2tx Mxene

The Formation Potential of Disinfection By-Products of Ti3c2tx Mxene

Separation performance of ultrafiltration during the treatment of algae-laden water in the presence of an anionic surfactant

Ultrafiltration was demonstrated to be an effective and efficient method to treat algae-laden water. However, the presence of compounds such as surfactants can act as a stimulus for algae outbreak and change the characteristics of algae cells and derived organics. Therefore, it is necessary to investigate the filtration and separation performance of ultrafiltration during the treatment of algae-laden water in the presence of anionic surfactants (the most widely used surfactant type). In this study, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (LAS) were employed respectively to simulate the presence of a low concentration of an anionic surfactant in eutrophicated water. It was found that surfactants present in natural waters could enhance the hydrophilicity of the algae interface and the stability of the algae-laden water system with mitigated algae aggregation. During the initial filtration process, membrane fouling was aggravated related to the more serious pore blocking induced by the present SDS or LAS; however, during the next stage, membrane fouling was alleviated due to the formation of a looser cake layer in the presence of SDS or LAS. The pore blocking at the earlier stage contributes more to the decrease of total flux when surfactants are involved. Furthermore, the disinfection byproduct formation potential was reduced with SDS or LAS mainly due to the degradation of free available chlorine by the surfactants. While the concentration of algal toxins was ascended in the ultrafiltration effluent, which indicates that the separation performance was highly impacted by the presence of anionic surfactant.

Prediction of Disinfection By-Product Formation Potential from Biofilm Chlorination in Plumbing Systems by a One-Dimension Model

Prediction of Disinfection By-Product Formation Potential from Biofilm Chlorination in Plumbing Systems by a One-Dimension Model

Improvement of Fe(Vi) Oxidation by Naclo on Degrading Phenolic Substances and Reducing Dbps Formation Potential

Improvement of Fe(Vi) Oxidation by Naclo on Degrading Phenolic Substances and Reducing Dbps Formation Potential

Unexpected Role of Nitrite in Promoting Transformation of Sulfonamide Antibiotics by Peracetic Acid: Reactive Nitrogen Species Contribution and Harmful Disinfection Byproduct Formation Potential

Peracetic acid (PAA) is an emerging oxidant and disinfectant for wastewater (WW) treatment due to limited harmful disinfection byproduct (DBP) formation. Nitrite (NO2-) is a ubiquitous anion in water, but the impact of NO2- on PAA oxidation and disinfection has been largely overlooked. This work found for the first time that NO2- could significantly promote the oxidation of sulfonamide antibiotics (SAs) by PAA. Unexpectedly, the reactive nitrogen species (RNS), for example, peroxynitrite (ONOO-), rather than conventional organic radicals (R-O•) or reactive oxygen species (ROS), played major roles in SAs degradation. A kinetic model based on first-principles was developed to elucidate the reaction mechanism and simulate reaction kinetics of the PAA/NO2- process. Structural activity assessment and quantum chemical calculations showed that RNS tended to react with an aromatic amine group, resulting in more conversion of NO2--N to organic-N. The formation of nitrated and nitrosated byproducts and the enhancement of trichloronitromethane formation potential might be a prevalent problem in the PAA/NO2- process. This study provides new insights into the reaction of PAA with NO2- and sheds light on the potential risks of PAA in WW treatment in the presence of NO2-.

Effects of pipe materials on the characteristic recognition, disinfection byproduct formation, and toxicity risk of pipe wall biofilms during chlorination in water supply pipelines

There are growing concerns over the contributions of biofilms to disinfection byproduct (DBP) formation in engineered water systems (EWSs). Three kinds of water supply pipes, ductile iron (DI), cement-lined stainless steel (SS) and polyethylene (PE) pipes, were selected for the experiment conducted in this study. Based on test results, the three pipe biofilms showed relatively obvious differences in growth, morphological characteristics, organic components and bacterial diversity. Secreted extracellular polymeric substance (EPS) accounted for more than 90% of the biofilm and had greater disinfection byproduct formation potential (DBPFP) than the cell phases. DI pipe wall biofilms had the highest DBPFP, which to a certain extent means that denser and richer organic matter can be produced as the precursor of different types of DBPs. UHPLC-Q Exactive was used to identify the types of DBPs generated from the chlorination of histidine (His), alanine (Ala) and tryptophan (Trp) shared by the three pipe materials and their formation pathways. Compared to carbonaceous disinfection by-products (C-DBPs), nitrogenous disinfection by-products (N-DBPs) had a significant advantage in toxicity generation potentials in the biofilms, especially dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM). DCAN and haloacetic acids (HAAs) were the key to cytotoxicity in biofilms, while TCNM was dominant in biofilm genotoxicity.

Effect of Al hydrates on minimization of disinfection-by-products precursors by coagulation with intensified pre-oxidation towards cyanobacteria-laden water

Pre-oxidation is warranted to improve cyanobacteria removal and minimize disinfection by-products (DBPs) precursors for subsequent coagulation with polyaluminum chloride (PACl) in drinking water treatment. However, the reduction in DBP precursors strongly depends on the Al hydrates for PACl coagulation. This study aimed to investigate the effects of intensified NaOCl and ClO2 pre-oxidation on the removal of Microcystis aeruginosa (MA) and the corresponding halogenated DBP precursors by PACl coagulation with different Al hydrates. Two PACl coagulants, namely PACl-W with 51% monomeric Al and PACl-H with 71% polymeric Al, were used for FlocCAM jar test. The results have shown that the reductions in MA cell and algogenic organic matter (AOM) are more pronounced by sweep flocculation in PACl-W coagulation coupled with NaOCl pre-oxidation. In contrast, ClO2 pre-oxidation with PACl-H coagulation outperforms the floc formation and the reduction in each fluorescent DOM substance, especially for humic acid-like (HAL) substances reduction in response to charge neutralization. Regardless of pre-oxidation approach, PACl-H coagulation exhibits a superior reduction in carbonaceous DBP formation potential (C-DBPFP) comparative PACl-W coagulation, especially for intensified pre-oxidation (Cl2:DOC = 3:1). Intensified NaOCl pre-oxidation is effective to enhance DBPFP reduction in a similar way to ClO2 oxidation by coagulation with both PACl coagulants. In addition, it clearly demonstrates that the halogenated DBP precursors are well-correlated with UV254 absorbance on the basis of principal component analysis (PCA) inference. It is concluded that intensified NaOCl pre-oxidation is an alternative approach to ClO2 pre-oxidation for the minimization of DBP precursors in oxidation-coagulation processes for cyanobacteria-laden water treatment.

Biologically Enhanced Coagulation–Ultrafiltration Process for Healthy Water Production with Low Fouling Propensity

Coagulation combined with ultrafiltration (UF) is an effective drinking water treatment process. However, inefficient removal of natural organic matter (NOM) and membrane fouling problems, especially those initiated by the adhesion of biopolymers, greatly restrict the practical application of the UF process. Here, we investigated a biologically enhanced coagulation–ultrafiltration (CUF) process treating samples of a natural surface water, which demonstrated a superior NOM removal and antifouling performance. The membrane flux (under 1.0 bar constant pressure) of the biologically enhanced CUF [using polyaluminum chloride (PACl)] process scheme was approximately 4.4 and 8.4 times higher than that of a conventional CUF and direct UF process, respectively, and PACl was found to perform better than AlCl3. Characterization of the NOM showed that the biological pretreatment combined with the coagulation process significantly contributed to the reduction of hydrophobicity, aromaticity, and molecular weight of the dissolved organics. Analyses of biopolymers showed that the combined process can remove over 99% of the biopolymers (represented by proteins and polysaccharides), which are considered to be the main cause of membrane fouling. Results of X-ray photoelectron spectroscopy and FTIR analyses further elucidated the transformation and reduction of biopolymers during the combined process. With respect to the disinfection byproduct formation potential (DBP-FP), the results showed that the conventional CUF process had a limited impact on the DBP-FP, while the biologically enhanced CUF process had a substantial impact consistent with meeting the current EPA DBP standards. Overall, this study has highlighted the potential advantages of using a biologically enhanced CUF process for producing higher quality drinking water with a simultaneous low membrane fouling propensity.

Towards microplastics contribution for membrane biofouling and disinfection by-products precursors: The effect on microbes

Public awareness of plastic pollution and its impact on the ecosystem has increased rapidly. The microplastics in raw waters and their removal during drinking water treatment is receiving growing attention, but the impact on the efficiency of ultrafiltration has not been examined previously, especially in regard to the formation potential of disinfection by-products (DBPs-FP) in effluent water. In this study, two bench-scale continuous-flow ultrafiltration systems, with and without microplastics, were operated to examine the effect of microplastics on ultrafiltration. Results showed that the microplastics not only increased microbial growth, but also affected the microbial community (e.g. families Xanthobacteraceae, Sphingomonadaceae, Leptolyngbyaceae), which can promote the production of extracellular polymeric substances and nitrogen fixation, causing rapid membrane fouling. The formation potential of THM (TCM and BDCM) and N-DBP (TCNM) species in UF permeate increased with the presence of microplastics, due to changes in water quality. Statistical analysis indicated that tyrosine-like components (C3), ammonium (NH4+-N) and tryptophan-like component (C1) can be used as indicators of the DBPs-FP. This study provides new insights into the relationship between microplastics, membrane biofouling and DBPs-FP, and the potential adverse impact of microplastics on drinking water treatment.

Organic matter removal with bicarbonate-form ion exchange: water quality, kinetics and mass transfer mechanisms

Ion Exchange (IEX) has been widely explored for the removal of organic matter. Chloride is traditionally used as counter-ion, but its release into water can increase the risk of corrosion. Research has shown that bicarbonate IEX can be an efficient alternative, and whilst some studies have compared its efficiency to chloride IEX, none have compared their performance in relation to the potential for disinfection by-product (DBPs) formation. The differences in organic matter removal between the two regenerants were assessed by looking at the molecular weight fractions derived from liquid chromatography organic carbon detection (LC-OCD) and dissolved organic carbon (DOC). Uptake kinetics, resin age and mass transfer diffusion were also investigated. DOC removal was similar for both chloride and bicarbonate resins, achieving ca 50% DOC removal. LC-OCD analysis revealed that organic matter between 0.35 and 1 kDa was the most efficiently removed, with slightly better uptake with bicarbonate IEX. However, these differences did not impact DBP formation potential. Trihalomethane (THM) and haloacetic acid (HAA) formation potentials followed the trends of DOC removal with up to 70% reduction after IEX treatment with both resin forms. However, the bromine substitution factor (BSF) increased with resin age -from 5 to 10% for THMs and from 4 to 7% for HAAs. Resin age resulted in up to 20% decrease in the organic matter uptake rates (from 0.19 to 0.15 min−1) and up to 34% decrease in pore diffusivities (from 9.4 × 10−12 to 7.1 × 10−12 m2/s for chloride IEX and from 1.0 × 10−11 to 6.6 × 10−11 m2/s).

Pilot study on the treatment of lake water with algae by ultrafiltration–ozone–biologically activated carbon

Abstract For the treatment of lake water with algae, the coagulation–ultrafiltration–ozone–biologically activated carbon (CUF–O3–BAC) integrated process was first used to treat East Taihu Lake water in China, aiming at evaluating the removal efficiencies of algae, permanganate index (CODMn), UV254, NH3-N and disinfection by-products (DBPs) precursors. In addition, the long-term performance of the membrane operation under the fluxes of 60, 70, 80 and 90 L/(m2·h) was also investigated, and kinetic models were established. The experimental results showed that the integrated process had positive impaction of algae, CODMn, UV254 and NH3-N removal, and the removal rates were 95.89 ± 1.52, 76.18 ± 4.38, 72.06 ± 4.72 and 81.31 ± 6.71%, respectively. The CUF process was prone to increase the formation potentials of DBPs. Although ozone could reduce the formation risks of chlorinated trihalomethanes (THMs) to a certain extent, it is ineffective to reduce those of brominated THMs and haloacetic acids (HAA5). However, the CUF–O3–BAC process was an effective technology for the removal of THMs and HAA5 precursors in drinking water treatment. Finally, it was found that the relationship between transmembrane pressure (TMP) and time conformed to the first-order and second-order kinetic models, and the linear fitting coefficients were all above 90%.

Characteristics of extracellular organic matters and the formation potential of disinfection by-products during the growth phases of M. aeruginosa and Synedra sp.

Extracellular organic matter (EOM) is an important precursor of disinfection by-products (DBPs). Nowadays, little is known about changes in molecular weight (MW) and hydrophilic (HPI)/hydrophobic (HPO) fractions of EOM during the entire algal growth phase. In this study, a combined approach of fractionation procedure and parallel factor (PARAFAC) analysis was applied to characterize the EOM during the entire growth phase of two algal species (M. aeruginosa and Synedra sp.), and investigated the relationships between fluorescent component and the DBP formation potential (FP) in MW and HPI/HPO fractions. Thereinto, three components (including one protein-like component (C1), one humic-like component (C2), and one fulvic acid-like component (C3)) were identified by the PARAFAC model. For two algae, the HPI and high MW (> 100 kDa) fractions were both the main components of algal EOM in the three growth phases in terms of the dissolved organic carbon. The high MW fraction had more C1 compared with other MW fractions, especially for M. aeruginosa. Besides, the formation risk of EOM-derived DBPs from M. aeruginosa was lower than that from Synedra sp. The result of this study showed the FP of DBPs varied with fluorescent components of algal EOM fractions and also indicated that the humic-like substances were tended to form trichloromethane and the tryptophan-like substances were associated with dichloroacetic acid by canonical correspondence analysis for both two algae.

Evaluation of enzyme activity for monitoring biofiltration performance in drinking water treatment

Many water providers monitor adenosine triphosphate (ATP) as an indicator of biological acclimation of their biofilters; however, strong correlations between ATP concentration and filter performance (e.g., organic matter or disinfection by-product precursor removal) are not typically observed. As an alternative, this study evaluated the use of enzyme activity for monitoring biological processes within filters. Recent studies have proposed that enzyme activity may be used as an indicator of biofilter function as it provides a means to quantify biodegradation which may allow for a more accurate measure of degradation potential and to gain a better understanding of biofilter performance. Sampling was completed from full- and pilot-scale biofilters to assess impacts associated with pre-treatments, varying sources waters, as well as pre-treatment and operating conditions. Enzyme activity (carboxylic esterase, phosphatase, ß-glucosidase, α-glucosidase, ß-xylosidase, chitinase, and cellulase) and ATP were measured from the top 5 cm of biofilter media representative of typical full-scale sampling; water quality parameters included dissolved organic carbon (DOC) and disinfection by-products (DBPs): trihalomethane (THM) formation potential (FP), and haloacetic acid FP (HAA FP). Results confirmed that ATP was not a reliable monitoring tool for DOC and DBP FP reduction in biofilters. A strong relationship was observed between esterase activity and DOC reduction; chitinase activity significantly correlated to THM FP reduction for filters treating three different source waters and HAA FP reduction achieved by filters treating the same source water with a range of pre-treatment and backwash conditions. This study showed that enzyme activity may be appropriate for monitoring biological processes within drinking water filters and may act as a surrogate for the removal of organic compounds.

Enhanced coagulation for mitigation of disinfection by-product precursors: A review

The unintended formation of disinfection by-products (DBPs) has received considerable attention as it may pose risks to human health. Coagulation is the most common process for removing particulates as well as dissolved organic matter (DOM) (i.e., DBP precursors) during drinking water and wastewater treatments. With the improvement of water quality standards and the increased fluctuation in source water quality, conventional coagulation becomes challenging. Thus, significant efforts have been made to enhance coagulation to promote the removal of DOM in source water and mitigate the formation of DBPs in drinking water. This review provides a brief summary of the properties of DBP precursors and summarizes the effectiveness of enhanced coagulation involving three types of coagulants (metal-based coagulants, organic polymers, and organic-inorganic hybrid coagulants) in controlling the formation of DBPs during chlor(am)ination disinfection. Metal-based coagulants can achieve a reduction in DBP formation potential of approximately 20%–60% in natural water under enhanced coagulation conditions. Both the organic polymers (used as coagulant aids) and novel hybrid coagulants increase the removal of DOM and exhibit high potential for mitigating DBP formation. In addition, integrated treatments combining coagulation with other treatment processes (e.g., oxidation, membrane filtration, ion exchange, and adsorption) to enhance DBP precursor removal are evaluated in terms of performance, mechanisms, and features. Advanced treatments, such as membrane filtration and activated carbon adsorption, are effective coagulation-assisted processes, and can further control chlorinated DBPs; however, the elevated formation of bromate or highly brominated DBPs is of particular concern.

Dynamic variations in DOM and DBPs formation potential during surface water treatment by ozonation-nanofiltration: Using spectroscopic indices approach

The combination of ozone and nanofiltration (NF) in drinking water treatment represents a potentially effective method of separating dissolved organic matter (DOM), and thereby reducing the potential formation of disinfection by-products (DBPs). This study has evaluated UV-absorbance and fluorescence-based optical descriptors, such as absorbance slope index (ASI), humification index (HIX), and the sum of fulvic-like and humic-like components (C1 + C2), etc., to track the variation of DOM constituents and DBP formation potential during the treatment of surface water samples by ozonation and nanofiltration (NF90 and NF270). Pre-ozonation markedly reduced the DOM molecular weight (MW) in the range of 5000–9000 Da by transforming the DOM into carboxylate-rich hydrophilic fractions, thereby mitigating the fouling of NF membranes. Among all the PARAFAC components, the humic-like component (C2) showed a predominant behavior against pre-ozonation and nanofiltration experiments. However, amino acid or microbial protein-like component (C3) was particularly associated with irreversible fouling of both membranes, compared to reversible fouling. C1 + C2 was found to be strongly correlated with both ASI and HIX, suggesting that C1 + C2 can be a useful surrogate for the humic-like content of the DOM. Principal DBPs detected after the chlorination were chloroform, bromodichloromethane and dichloroacetic acid, and DBP formation potential reduced with increased ozonation. A strong correlation between these DBPs and spectroscopic indices indicated that the humic content was an important factor in the formation of DBPs. In contrast, increasing ozonation not only shifted the DBP formation potential towards brominated precursors, but also resulted in increased brominated species of haloacetic acids. However, both NF membranes achieved approximately 90% removal of DBP precursors, for all of the detected DBPs, which was attributed to size exclusion and electrostatic interaction effects.

Performance of a Hybrid ED–NF Membrane System for Water Recovery Improvement via NOM Fouling Control

Natural organic matter (NOM) complicates water treatment and causes formation of disinfection byproducts (DBPs). NOM is removed well by nanofiltration (NF) but causes extensive membrane fouling, especially in the presence of divalent cations. This research investigated a hybrid electrodialysis-nanofiltration (ED–NF) system to treat freshwaters containing hardness and NOM. ED removes most ions but little to no NOM, and the ED diluate is, then, treated with NF to remove NOM with reduced fouling. Subsequently, some or all of the ED concentrate can be mixed with the NF permeate to increase water recovery, limit NOM concentration (and thereby reduce DBPs), and control the ion content. Compared to NF alone, ED–NF increases product water yield. NF fouling was reduced by the removal of divalent cations in ED. Spectroscopic and resonant scattering measurements of fouled membranes near the calcium K-edge reveal a significant contribution to NF fouling by calcium bridging between carboxyl groups in NOM and on the membrane surface. This novel ED–NF system allows several control “knobs” to increase water recovery and reduce DBP formation potential by adjusting ED water recovery, ED diluate (and concentrate) ionic composition, and the fraction of concentrate remixed with NF permeate to form the product water.