Assessing the role of different dissolved organic carbon and bromide concentrations for disinfection by-product formation using chemical analysis and bioanalysis

Performance evaluation of artificial intelligence with particle swarm optimization (PSO) to predict treatment water plant DBPs (haloacetic acids)

The prevention of water-borne diseases requires the disinfection of water consumed. Disinfection by-products, however, are an increasing concern, and they require advanced knowledge of water treatment plants before their release for human consumption. In this study, multivariate non-linear regression (MNR) and adaptive neuro-fuzzy inference system (ANFIS: Grid partition - GP and Sub-clustering - SC) integrated with particle swarm optimization (PSO) were proposed for the prediction of haloacetic acids (HAAs) in actual distribution systems. PSO-ANFIS-GP and PSO-ANFIS-SC were trained and verified for a total of 64 sets of data with eight parameters (pH, Temperature, UVA254, DOC, Br-; NH4+-N; NO2--N, residual free chlorine). With MNR, R2 is 0.5184 Collapse

Key Words

• Grid partition
• Haloacetic acids
• Multivariate non-linear regression
• Particle swarm optimization
• Sub-clustering

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MESH Headings

• Humans
• Artificial Intelligence
• Water Purification
• Neural Networks, Computer
• Fuzzy Logic
• Disinfection

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Grants Collapse

Affiliation(s)

Anthony I Okoji Department of Chemical Engineering, Covenant University, Ota, Ogun state, Nigeria.
Comfort N Okoji Department of Biology and Forensic, Admiralty University, Ibusa, Delta state, Nigeria
Olorunfemi S Awarun Department of Microbiology, Landmark University, Omu-Aran, Kwara state, Nigeria

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A critical review on quantitative evaluation of aqueous toxicity in water quality assessment

Conventional chemical techniques have inherent limitations in detecting unknown chemical substances in water. As a result, effect-based methods have emerged as a viable alternative to overcome these limitations. These methods provide more accurate and intuitive evaluations of the toxic effects of water. While numerous studies have been conducted, only a few have been applied to national water quality monitoring. Therefore, it is crucial to develop toxicity evaluation methods and establish thresholds based on quantifying toxicity. This article provides an overview of the development and application of bioanalytical tools, including in vitro and in vivo bioassays. The available methods for quantifying toxicity are then summarized. These methods include aquatic life criteria for assessing the toxicity of a single compound, comprehensive wastewater toxicity testing for all contaminants in a water sample (toxicity units, whole effluent toxicity, the potential ecotoxic effects probe, the potential toxicology method, and the lowest ineffective dilution), methods based on mechanisms and relative toxicity ratios for substances with the same mode of action (the toxicity equivalency factors, toxic equivalents, bioanalytical equivalents), and effect-based trigger values for micropollutants. The article also highlights the advantages and disadvantages of each method. Finally, it proposes potential areas for applying toxicity quantification methods and offers insights into future research directions. This review emphasizes the significance of enhancing the evaluation methods for assessing aqueous toxicity in water quality assessment.

Effects of dissolved organic matter removal and molecular transformation in different water treatment processes on formation of disinfection byproducts

Alterations in molecular composition of dissolved organic matter (DOM) during water treatments can influence the composition and toxicity of disinfection by-products (DBPs) in subsequent chlorination disinfection process. In this study, the impacts of DOM composition after various water treatment techniques (coagulation, adsorption, nanofiltration, biological aerated filter (BAF), and their integrated processes) on the generation mechanisms of DBPs were comprehensively explored by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in combination with GC-MS and LC-MS analysis. The results indicated that coagulation preferentially removed unsaturated (low H/C) and oxidized (high O/C) compounds, whereas adsorption was prone to remove the reduced (low O/C) component that was more reactive with chlorine, leading to lower yields (μg DBP/mg DOC) of trihalomethanes (THMs) and haloacetic acids (HAAs) during subsequent chlorination. The coagulation-adsorption technique exhibited a relatively high removal of both known and unknown DBPs, demonstrating that coagulation and adsorption were complementary for DOM removal at the molecular level. Nanofiltration selectively removed molecules with relatively high O/C, however, those with very low O/C that were more reactive with chlorine could pass through the nanofiltration membrane, resulting in the highest yields of THMs and HAAs. Although BAF was inefficient in removing DBPs precursors, it could convert molecules with low degree of oxidation and unsaturation into highly oxidized and unsaturated ones, thereby significantly enhancing the removal of DBPs precursors in the subsequent coagulation-adsorption process. These findings are instrumental in developing and selecting more effective techniques to minimize the formation of DBPs in water treatment.

Terrestrial dissolved organic matter source affects disinfection by-product formation during water treatment and subsequent toxicity

Restoring woody vegetation to riparian zones helps to protect waterways from excessive sediment and nutrient inputs. However, the associated leaf litter can be a major source of dissolved organic matter (DOM) leached into surface waters. DOM can lead to the formation of disinfection by-products (DBPs) during drinking water treatment. This study investigated the DBPs formed during chlorination of DOM leached from leaf litter and assessed the potential toxicity of DBPs generated. We compared the leachate of two native Australian riparian trees, Casuarina cunninghamiana and Eucalyptus tereticornis, and a reservoir water source from a catchment dominated by Eucalyptus species. Leachates were diluted to dissolved organic carbon concentrations equivalent to the reservoir (~9 mg L^-1). E. tereticornis leachates produced more trihalomethanes (THMs), haloacetic acids (HAAs), and haloketones after chlorination, while C. cunninghamiana produced more chloral hydrate and haloacetonitriles. Leachate from both species produced less THMs and more HAAs per mole of carbon than reservoir water. This may be because reservoir water had more aromatic, humic characteristics while leaf leachates had relatively more protein-like components. Using in vitro bioassays to test the mixture effects of all chemicals, chlorinated E. tereticornis leachate induced oxidative stress in HepG2 liver cells and bacterial toxicity more frequently and at lower concentrations than C. cunninghamiana and reservoir water. Overall, this study has shown that the DOM leached from litter of these species has the potential to generate DBPs and each species has a unique DBP profile with differing bioassay responses. E. tereticornis may pose a relatively greater risk to drinking water than C. cunninghamiana as it showed greater toxicity in bioassays. This implies tree species should be considered when planning riparian zones to ensure the benefits of vegetation to waterways are not offset by unintended increased DBP production and associated toxicity following chlorination at downstream drinking water intakes.