Using discrete and online ATP measurements to evaluate regrowth potential following ozonation and (non)biological drinking water treatment.

Water utilities must control microbial regrowth in the distribution system to protect public health. In this study, an adenosine triphosphate (ATP)-based biomass production potential test using indigenous bacterial communities were used to evaluate regrowth potential following ozonation with either biofiltration (BF) or sustained chlorination (SCl). Two full-scale water treatment plants with different upstream processes (i.

Using upstream oxidants to minimize surface biofouling and improve hydraulic performance in GAC biofilters.

The combination of biological growth and particle loading can adversely affect hydraulic performance in drinking water biofilters. In this study, upstream oxidant addition was used to distribute biologically-derived filter clogging in granular activated carbon (GAC) biofilters. Oxidant penetration was assessed during pilot-scale operation and backwashing of dual media (GAC/sand) and multimedia (GAC/anthracite/sand) biofilters.

Predicting reactivity of model DOM compounds towards chlorine with mediated electrochemical oxidation.

Chlorine demand of a water sample depends on the characteristics of dissolved organic matter (DOM). It is an important parameter for water utilities used to assess oxidant and/or disinfectant consumption of source waters during treatment and distribution. In this study, model compounds namely resorcinol, tannic acid, vanillin, cysteine, tyrosine, and tryptophan were used to represent the reactive moieties of complex DOM mixtures.

Kinetics and mechanisms of nitrate and ammonium formation during ozonation of dissolved organic nitrogen.

Dissolved organic nitrogen (DON) is an emerging concern in oxidative water treatment because it exerts oxidant demand and may form nitrogenous oxidation/disinfection by-products. In this study, we investigated the reactions of ozone with DON with a special emphasis on the formation of nitrate (NO) and ammonium (NH). In batch ozonation experiments, the formation of NO and NH was investigated for natural organic matter standards, surface water, and wastewater effluent samples.

Biodegradability of DBP precursors after drinking water ozonation.

Ozonation is known to generate biodegradable organic matter, which is typically reduced by biological filtration to avoid bacterial regrowth in distribution systems. Post-chlorination generates halogenated disinfection byproducts (DBPs) but little is known about the biodegradability of their precursors. This study determined the effect of ozonation and biofiltration conditions, specifically ozone exposure and empty bed contact time (EBCT), on the control of DBP formation potentials in drinking water.

Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation.

When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and •OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6-8) and transferred ozone doses (0-1 mg/mg TOC).