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Journal ArticleDOI

Cellular Automata-Based Mechanistic Model for Analyzing Microbial Regrowth and Trihalomethanes Formation in Water Distribution Systems

01 Jan 2021-Journal of Environmental Engineering (American Society of Civil Engineers)-Vol. 147, Iss: 1, pp 04020145
Abstract: This paper describes a novel cellular automata-based mesoscale multispecies reactive-transport (CA-MSRT) model for predicting microbial regrowth and trihalomethanes (THMs) formation in wate...

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Journal ArticleDOI
10 Feb 2021-Water
Abstract: The formation of bacterial regrowth and disinfection by-products is ubiquitous in chlorinated water distribution systems (WDSs) operated with organic loads. A generic, easy-to-use mechanistic model describing the fundamental processes governing the interrelationship between chlorine, total organic carbon (TOC), and bacteria to analyze the spatiotemporal water quality variations in WDSs was developed using EPANET-MSX. The representation of multispecies reactions was simplified to minimize the interdependent model parameters. The physicochemical/biological processes that cannot be experimentally determined were neglected. The effects of source water characteristics and water residence time on controlling bacterial regrowth and Trihalomethane (THM) formation in two well-tested systems under chlorinated and non-chlorinated conditions were analyzed by applying the model. The results established that a 100% increase in the free chlorine concentration and a 50% reduction in the TOC at the source effectuated a 5.87 log scale decrement in the bacteriological activity at the expense of a 60% increase in THM formation. The sensitivity study showed the impact of the operating conditions and the network characteristics in determining parameter sensitivities to model outputs. The maximum specific growth rate constant for bulk phase bacteria was found to be the most sensitive parameter to the predicted bacterial regrowth.

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4 citations


Cites background or methods from "Cellular Automata-Based Mechanistic..."

  • ...For simplification, the bacterial cells’ organic carbon contents were approximated as 1 × 10−9 mg-C/CFU [10,11]....

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  • ...0 mg-C/L represents water with possible organic pollution [11]....

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  • ...The chlorine-induced mortality was modeled with second-order kinetics based on the concept of competing reactions in water [11]....

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  • ...A similar work, utilizing a Cellular Automata-based model (CA-MSRT model), was recently reported by [11]....

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Journal ArticleDOI
G. R. Abhijith1, Avi Ostfeld1Institutions (1)
Abstract: A mechanistic simulation model predicting the response of water distribution systems (WDSs) operated with or without disinfectant residual toward accidental arsenic contamination is develop...

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1 citations


Journal ArticleDOI
27 Feb 2021-Water
TL;DR: The pipe material’s critical role in stimulating O-methyltransferases enzymatic activity and regulating 2,4,6-TCP bioconversion in water was established and kinetic expressions formulated were later applied to develop a novel EPANET-MSX-based multi-species reactive-transport (MSRT) model.

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Abstract: 2,4,6-trichloroanisole (2,4,6-TCA) formation is often reported as a cause of taste and odor (T&O) problems in water distribution systems (WDSs). The biosynthesis via microbial O-methylation of 2,4,6-trichlorophenol (2,4,6-TCP) is the dominant formation pathway in distribution pipes. This paper attempted to utilize the reported data on the microbial O-methylation process to formulate deterministic kinetic models for explaining 2,4,6-TCA formation dynamics in WDSs. The pipe material’s critical role in stimulating O-methyltransferases enzymatic activity and regulating 2,4,6-TCP bioconversion in water was established. The kinetic expressions formulated were later applied to develop a novel EPANET-MSX-based multi-species reactive-transport (MSRT) model. The effects of operating conditions and temperature in directing the microbiological, chemical, and organoleptic quality variations in WDSs were analyzed using the MSRT model on two benchmark systems. The simulation results specified chlorine application’s implication in maintaining 2,4,6-TCA levels within its perception limit (4 ng/L). In addition, the temperature sensitivity of O-methyltransferases enzymatic activity was described, and the effect of temperature increase from 10 to 25 °C in accelerating the 2,4,6-TCA formation rate in WDSs was explained. Controlling source water 2,4,6-TCP concentration by accepting appropriate treatment techniques was recommended as the primary strategy for regulating the T&O problems in WDSs.

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Cites result from "Cellular Automata-Based Mechanistic..."

  • ...The existing scientific knowledge was applied during the model development to define chlorine decay, NOM degradation, planktonic microbial regrowth, biofilm dynamics, and THM formation inside the distribution pipes....

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  • ...The MSRT model, implemented using the multi-species extension of EPANET (EPANET-MSX) [24], considers the advective transport and reactions of chlorine, NOM, microorganisms, and 2,4,6-TCP in WDSs. Simulations were conducted within two benchmark systems, and the resulted output includes concentrations of the relevant biotic and abiotic parameters signifying the physicochemical and biological interactions in WDSs....

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  • ...Recent research identified two independent pathways for 2,4,6-TCA formation [16]: chlorination of anisole in natural organic matter (NOM); microbial O-methylation of precursor 2,4,6-trichlorophenol (2,4,6-TCP)....

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  • ...Apart from SAM, the other methyl donors include methanol, methylamines, and methanethiol, which are amply present as NOM in the natural waters [20]....

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  • ...Yield coefficients were selected to represent THMs formation by chlorine reactions with NOM [25] and planktonic microorganisms [36]....

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Journal ArticleDOI
Gopinathan R. Abhijith1, Avi Ostfeld1Institutions (1)
01 Oct 2021-Water Research
Abstract: Recent studies identified fluoroalkyl amides (FAs) transformation to perfluorooctanoic acid (PFOA) during disinfection as an indirect source of PFASs contamination of drinking water. This paper discerns the position of water disinfection systems (WDSs) as a PFOA exposure pathway. A new mechanistic model incorporating the derived knowledge about the zwitterionic/cationic FAs transformation to PFOA with the unsteady-state hydraulic characteristics of WDSs was developed. The simulation outputs from model application to a WDS from the USA established the significant role of delivery via distribution network in the PFOA formation in drinking water. PFOA exposure risk assessment studies predicted >95% of the system nodes to be at high risk when the existing stringent health-based guideline values are adopted. The 1 to 3 years and 4 to 8 years old age groups were found susceptible to PFOA exposure through drinking water beyond the tolerable limit of 3 ng/kg/day. The model predicted that reducing the chlorine dose from 2±0.2 to 1±0.1 mg/L at the treatment units drops the share of 1 to 3 years old and 4 to 8 years old consumers falling to PFOA exposure from 4.32 to 0.45% and 0.32 to

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