Amounts Of Disinfection By-products Research Articles

Percarbonate mediated advanced oxidation of irbesartan: A suitable alternative to chlorination?

This study aims to investigate the environmental fate of irbesartan when subjected to activated percarbonate treatment. The investigation delves into the formation of disinfection byproducts (DBPs) and evaluates their toxicity, and it seeks to draw comparisons with outcomes from treatment with sodium hypochlorite, already characterized in previous findings. The proposed treatment indicates the formation of at least 11 DBPs - eight identified for the first time - which have been isolated by various chromatographic techniques, identified by Nuclear Magnetic Resonance and Mass Spectrometry studies and for which a mechanism has been proposed to elucidate their formation. To evaluate irbesartan's biological impact during treatment with sodium percarbonate (SPC), a toxicity study of the DBPs was conducted using Daphnia magna, Aliivibrio fischeri, and Raphidocelis subcapitata, three model organisms. The ecotoxicity was evaluated using the Ecological Structure-Activity Relationships (ECOSAR) computer program and compared with experimental results. Compared to chlorination treatment, a lower mineralization percentage (−43 %) and amount of DBPs at least twice higher were observed. Toxicity assessment highlighted that DBPs formed during SPC treatment were more toxic than those from chlorination. ECOSAR predicted toxicity aligned with experimental findings. Additionally, the DBPs exhibited varying levels of toxicity, primarily attributable to the presence of aromatic and hydroxyl groups in their chemical structure, indicating that SPC treatment is not suitable for treatment of irbesartan polluted waters.

Effect of Oxidation on the Formation of Disinfectant By-products of Low Molecular Weight Organic Matter

Some natural organic compounds (NOC) such as aromatic compounds can trigger the formation of disinfection by-products (DBPs). In chlorination (disinfectant) process resultant water quality depletes. Some safe alternative oxidants are needed for cleaning water pollutants. KMnO4 had shown better oxidation results, especially for reducing aromatic and non-aromatic organic compounds present in water. The aim of this study was to analyze the effect of KMnO4 and Ca(OCl)2 oxidants on the concentration of high and low molecular weight organic matter including aromatic compounds in the water sample. In this experiment, artificial organic compounds, namely sinapic acid (high molecular weight aromatic compound) and resorcinol (low molecular weight aromatic compound) were used to identify the characteristic of organic matter under different molecular weights. Sinapic acid and resorcinol were oxidized by using KMnO4 and Ca(OCl)2 with a minimum contact time of 60 minutes. Samples were analyzed for aromatic contents and total organic carbon (TOC) before and after completion of the experiment by using UV-Vis spectrophotometer at 254 nm wavelength (UV254). It has been observed that both oxidants increased TOC concentration. Ca(OCl)2 produces a higher percentage of organic matter degradation by-products (DBPs) such as chloroform (CHCl3) a highly toxic compound than KMnO4. Since Ca(OCl)2 has a higher oxidation potential than KMnO4. It has been observed that KMnO4 is a safer oxidant than Ca(OCl)2 as potassium permanganate produces less amount of DBPs.

Contribution of extracellular polymeric substances and microbial community on the safety of drinking water quality: By mean of Cu/activated carbon biofiltration

Change in water quality was investigated with laboratory-scale ozone-biological activated carbon filters using copper-modified granular activated carbon (Cu/GAC) and unmodified granular activated carbon (GAC). In the first seven days of the experimental period, Cu/GAC removed organic matter more efficiently owing to its enhanced adsorption capacity. As the running time increased, the amount of disinfection by-products (DBPs), dissolved organic carbon, and extracellular polymeric substances (EPS) increased sharply in the effluent of the Cu/GAC filter (CCW). More importantly, the EPS suspended in the CCW exhibited weaker flocculating efficiency and hydrophobicity, causing more active chemical reactions between chlorine and EPS substances. The copper species significantly limited the microbial biomass (0.01 nmol/L adenosine triphosphate) but stimulated the secretion of significant amounts of EPS by microorganisms for self-protection. Furthermore, the microbial community in the bulk water was successfully shaped by Cu/GAC, resulting in a continuous supply of EPS-derived DBP precursors and a sharp rise in chlorine consumption in the downstream drinking water distribution. Therefore, use of modified GAC materials, similar to Cu/GAC, as carrier materials for biological activated carbon (BAC) treatment remains controversial, despite enhanced pollutant adsorption capacity. This is the first study to reveal the mechanism of BAC-modified materials for water quality stability. The study potentially contributes to a comprehensive understanding of the effects of biofilm transformation and microbial community succession on drinking water quality. These results showed that tap water safety risks could be reduced by improving BAC pretreatment in drinking water treatment plants.

Pathogen inactivation and by-product formation in a full-scale contact tank

Conventional designs of chlorine contact tanks in potable water treatment plants are insufficient in terms of disinfection efficiency due to low hydraulic and mixing efficiencies. Strong interaction of the turbulent flow with the solid baffles may adversely affect hydraulic, mixing and disinfection performance of the contact system. Recirculating and jet zones created in the tank may require high chlorine dosages to yield adequate disinfection levels, which can result in the formations of high disinfection by-products (DBPs) in the treated water. The use of treated water by the consumers with high chlorine dosages and DBPs may lead to environmental and health problems in the long-term. Disinfection efficiency of the tank can be increased by the modification of the baffles and required disinfection levels can be achieved using lower chlorine dosages. In this study, performance of a patented baffle design is evaluated by means of numerical simulations on a full-scale contact tank. Self-decomposition of the chlorine, pathogen inactivation and formation of Trihalomethane (TTHM) by-product are simulated using a second-order numerical model. Numerical results show that the new baffle design yields 3-log inactivation by using 40% less chlorine concentration than the conventional design and the amount of DBP can be decreased by 43%.

Effectiveness of Bio-Activated Carbon Filtration and Ozonation on Control of Halo Acetic Acids Formation during Chlorination of Ganga River Water at Kanpur, India

ABSTRACTChlorinated water from River Ganga is the main source of drinking water in Kanpur, India. But, this water contains a significant amount of disinfection by-products (DBPs) that include haloacetic acids (HAAs) as a major contributor, which pose a carcinogenic risk on long-term ingestion. Therefore, in order to control HAAs formation, different combinations of ozonation and bio-activated carbon filtration (BAC-filtration) were studied. The results elucidate that slight ozonation followed by BAC-filtration proved effective in reducing (75.8%) HAAs formation and meet the USEPA drinking standards. These findings open a path to explore cost-effective treatment techniques in continuous mode for safe drinking water.

Chemical and toxicological characterization of halobenzoquinones, an emerging class of disinfection byproducts.

Halobenzoquinones (HBQs), a new class of disinfection byproducts (DBPs), occur widely in treated drinking water and recreational water. The main concern regarding human exposure to DBPs stems from epidemiological studies that have consistently linked the consumption of chlorinated drinking water with an increased risk of developing bladder cancer. The U.S. Environmental Protection Agency and Health Canada have set regulations on the amount of DBPs in drinking water to minimize the risk. However, these regulated DBPs do not account for the increased risk of bladder cancer because they have different target organs or lower magnitudes of risk based on animal carcinogenesis studies. Because of the pervasive exposure to DBPs, identification of DBPs relevant to human health has become one of the important research targets to address DBP-associated health concerns. Quantitative structure-toxicity relationship (QSTR) analysis has predicted HBQs to be potential bladder carcinogens. Therefore, this perspective focuses on the chemical and toxicological characterization of HBQs. In vitro cytotoxicity experiments have shown that HBQs induce greater cytotoxicity and/or greater developmental toxicity than most of the regulated DBPs. Cellular mechanistic studies indicate that HBQs are capable of producing reactive oxygen species (ROS) either within cells or in solution, depleting cellular glutathione levels, and influencing cellular antioxidant enzymes, which further induces oxidative stress and oxidative damage to cellular proteins and DNA. Oxidative damage to DNA was demonstrated in the form of significant increases in cellular levels of 8-hydroxydeoxyguanosine (8-OHdG), DNA strand breaks, and apurinic/apyrimidinic (AP) sites. HBQs can also form DNA adducts, affect genome-wide DNA methylation, and inhibit DNA repair enzymes. These findings demonstrate that HBQs are highly cytotoxic and potentially genotoxic and carcinogenic, although in vivo data corroborating this is not available. To fully understand the potential adverse health effects and cancer risk due to HBQ exposure, multidisciplinary research is required regarding human exposure, health risk assessment, and toxicological mechanisms of HBQs.

Removal of viruses and disinfection by-products at two drinking water treatment plants in southern China

Abstract The removal of viruses and disinfection by-products (DBPs) at two water plants (A and B) in a city of southern China was investigated. Coliphages MS2 and Phix174 were used as indicators of viruses. The results clearly indicated that the removal efficiency of MS2 and Phix174 was over 99% by conventional coagulation/sedimentation with polyaluminium sulfate chloride (PACS) at Plants A and B. MS2 and Phix174 were not detected in the effluent of these two plants. However, the removal efficiency of UV254 and TOC by coagulation/sedimentation was only 22.05% and 64.57% at Plant A, and 17.64% and 11.89% at Plant B, respectively. The species and amount of DBPs and their formation potential had no significant decrease after coagulation/sedimentation. In biological filtration, UV254 and TOC could be removed 6.62% and 24.50%, respectively. However, more soluble microbial products (SMP) and extracellular polymeric substances (EPS), the precursors of DBPs, were produced. Granular activated carbon (GAC) was efficient in the removal of UV254 and TOC, with an efficiency of 16.18% and 14.85%, respectively. Sand filtration, the final process, performed poorly in removing viruses and DBPs precursors. Both the processes of Plants A and B were not efficient in the removal of DBPs and their precursors.

Removal of disinfection by-products in raw water using a biological powder-activated carbon system

This study investigates the removal efficiency of disinfection by-products (DBPs) in raw water at a water treatment plant using a biological powder-activated carbon system (BPACS). The presence of an excessive amount of DBPs has a large impact on the water quality of drinking water treated from the purification process. This study collected rapidly filtered water from an advanced water treatment plant for use in experiments on raw water. The removal efficiency of the trihalomethane formation potential (THMFP) and haloacetic acids formation potential (HAAFP) was studied under various hydraulic retention times and under organic DOC loadings. The results showed that the BPACS lowered the average concentration of dissolved organic carbon (DOC), UV254 and the SUVA value (equivalent to UV254/DOC) in raw water. The system efficiently removed the THMFP and HAAFP during the treatment of the three primary organic carbon items. These results highlight the importance of the BPACS for efficiently treating disinfection by-products. These discoveries provide important information on biological degradation behaviors that can remove excessive amounts of disinfection by-products from drinking water.

Simultaneous degradation of disinfection byproducts and earthy-musty odorants by the UV/H 2O 2 advanced oxidation process

Advanced treatment technologies that control multiple contaminants are beneficial to drinking water treatment. This research applied UV/H 2O 2 for the simultaneous degradation of geosmin, 2-methylisoborneol, four trihalomethanes and six haloacetic acids. Experiments were conducted in de-ionized water at 24 ± 1.0 °C with ng/L amounts of odorants and μg/L amounts of disinfection byproducts. UV was applied with and without 6 mg/L H 2O 2. The results demonstrated that brominated trihalomethanes and brominated haloacetic acids were degraded to a greater extent than geosmin and 2-methylisoborneol. Tribromomethane and dibromochloromethane were degraded by 99% and 80% respectively at the UV dose of 1200 mJ/cm 2 with 6 mg/L H 2O 2, whereas 90% of the geosmin and 60% of the 2-methylisoborneol were removed. Tribromoacetic acid and dibromoacetic acid were degraded by 99% and 80% respectively under the same conditions. Concentrations of trichloromethane and chlorinated haloacetic acids were not substantially reduced under these conditions and were not effectively removed at doses designed to remove geosmin and 2-methylisoborneol. Brominated compounds were degraded primarily by direct photolysis and cleavage of the C–Br bond with pseudo first order rate constants ranging from 10 −3 to 10 −2 s −1. Geosmin and 2-methylisoborneol were primarily degraded by reaction with hydroxyl radical with direct photolysis as a minor factor. Perchlorinated disinfection byproducts were degraded by reaction with hydroxyl radicals. These results indicate that the UV/H 2O 2 can be applied to effectively control both odorants and brominated disinfection byproducts.

Disinfection By-products: A Question of Balance

Disinfection By-products: A Question of Balance

Probing the mechanisms of NOM chlorination using fluorescence: formation of disinfection by-products in Alento River water

Experiments with Alento River water (a drinking water source in the province of Salerno, Italy) showed that considerable amounts of disinfection by-products, primarily chloroform and haloacetic acids, form in that water upon chlorination. The total yield of haloacetic acids was almost twice as high as that of chloroform. Chlorination also caused significant changes in the intensity of NOM fluorescence and the position of the emission band. To quantify the latter, the wavelength that corresponds to the position of the emission band at its half-intensity (λ0.5) was employed. Chlorination caused the λ0.5 values to decrease, while the THMs and HAAs concentrations were linearly correlated with the corresponding λ0.5 values. The strength of correlations between DBP concentrations and λ0.5 values indicates that the latter parameter can be employed in studies of DBP formation in drinking water.

Pathways of trihalomethane uptake in swimming pools

Chlorination of pool water leads to the formation of numerous disinfection by-products (DBPs), chloroform usually being most abundant. Bathers and pool guardians take up various amounts of DBPs by different pathways. Identification of different uptake paths is important in order to develop a technical strategy for swimming pool water treatment and to develop focussed technical solutions to minimize THM uptake. Basically, trihalomethanes (THMs) can be taken up by inhalation, by dermal absorption, or orally (swallowing of water). In our experimental study involving up to 17 participants we quantified the body burden resulting from exposure to three different concentrations of chloroform in water and air of an indoor swimming pool, during a 60 min exercising period. Chloroform concentration of the water was 20.7, 7.1, and 24.8 μg/l and was not influenced artificially. Corresponding air CHCl3 concentrations were measured at two different levels (20 cm and 150 cm) and ranged from to 85 to 235 μg/m3. To dissociate the dermal exposure route from that of inhalation, THM concentrations were measured in the blood of subjects practicing in an indoor pool with and without scuba tanks, as well as in the blood of subjects walking around the pool without swimming. Chloroform concentrations were measured in blood samples before and after each exercise period. Blood chloroform concentration of participants with scuba tanks was 0.32+/−0.26 μg/l, without scuba tanks 0.99+/−0.47 μg/l, and for persons walking around the pool 0.31+/−0.25 μg/l. Our results indicate that THMs are mainly taken up over the respiratory pathway. Only about one third of the total burden is taken up over the skin. We examined the relationship between blood concentration and environmental chloroform concentrations by using linear regression models. Blood concentrations are correlated to air chloroform concentrations; correlation to water concentrations is less obvious.

Fine-tuning the corrosion control targets of alkalinity and pH for Massachusetts Water Resources Authority

Massachusetts Water Resources Authority (MWRA) supplies metropolitan Boston with unfiltered surface water. The source water is corrosive. An interim corrosion control facility came on line in June 1996 to adjust the pH and alkalinity levels for better corrosion control. Copper levels have never been higher than the action limit of 1.3 mg/l and the 90th percentile copper is now less than 0.15 mg/l. The 90th percentile lead level is close to the action level of 0.015 mg/l, but is sometimes still in exceedance. The September 2002 sampling of lead and copper (after the paper was submitted) showed the 90th percentile of lead and copper to be 0.0113 and 0.117 mg/l. MWRA is exploring the option of changing pH and alkalinity targets to meet the lead rule. In addition to lead concerns, other water quality concerns were identified as being sensitive to alkalinity and pH targets. These include, for example, the amount of disinfection by-products formed, the amount of iron released, chloramine stability and nitrification, the buffering capacity of treated water (pH stability), virus inactivation and copper levels in the biosolids from wastewater treatment. The proper target level for pH and alkalinity is a balance between these protective public health and operational goals. Models were developed to assist in fine-tuning the current pH and alkalinity targets of 9.1 and 35 mg/l as calcium carbonate for optimum water quality.

A MULTIPLE-PURPOSE DESIGN APPROACH TO THE EVALUATION OF RISKS FROM MIXTURES OF DISINFECTION BY-PRODUCTS*

Drinking water disinfection has effectively eliminated much of the morbidity and mortality associated with waterborne infectious diseases in the United States. Various disinfection processes, however, produce certain types and amounts of disinfection by-products (DBPs), including trihalomethanes (THM), haloacetic acids, haloacetonitriles, and bromate, among others. Human health risks from the ubiquitous exposure to complex mixtures of DBPs are of concern because existing epidemiologic and toxicologic studies suggest the existence of systemic or carcinogenic effects. Researchers from several organizations have developed a multiple-purpose design approach to this problem that combines efficient laboratory experimental designs with statistical models to provide data on critical research issues (e.g., estimation of human health risk from low-level DBP exposures, evaluation of additivity assumptions as useful for risk characterization, estimation of health risks from different drinking water treatment options). A series of THM experiments have been designed to study embryonic development, mortality and cancer in Japanese medaka (Oryzias latipes) and liver and kidney endpoints in female CD-1 mice. The studies are to provide dose-response data for specific mixtures of the 4 THMs, for the single chemicals, and for binary combinations. The dose-levels and mixing ratios for these experiments were selected to be useful for development and refinement of three different statistical methods: testing for departures from dose-additivity; development of an interactions-based hazard index; and use of proportional-response addition as a risk characterization method. Preliminary results suggest that dose-additivity is a reasonable risk assessment assumption for DBPs. The future of mixtures research will depend on such collaborative efforts that maximize the use of resources and focus on issues of high relevance to the risk assessment of human health.