Case Study: Ozonation and distribution system biostability

Abstract

Biodegradable organic matter that is not removed during water treatment can lead to the proliferation of bacteria within the distribution system. This, in turn, can deteriorate water quality, accelerate corrosion rates of pipes, and potentially increase the incidence of bacteriological diseases. The main objective of this project was to collect and analyze fullscale system data on short-term and long-term responses to the implementation of ozonation with respect to its impact on bacterial regrowth potential as quantified by assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). A major observation made during the sampling period was that ozonation caused a significant increase in the AOC concentration of the distribution system (more than 200% in the short term and more than 100% in the long term). Use of ozone also caused a significant increase in the bacterial counts within the distribution system for both the long and short terms. In contrast, ozonation affected BDOC and dissolved organic carbon (DOC) concentrations only slightly compared with its impact on AOC concentrations. However, this may be because of the source water, which had low DOC and BDOC concentrations (1.2 and 0.11 mg/L, respectively).

Diverse manganese(II)‐oxidizing bacteria are prevalent in drinking water systems

“…First, the observed abundance Mn(II)‐oxidizing bacteria in DW systems suggests that biogenic Mn oxides produced by these organisms could influence DW quality. Highly reactive biogenic Mn oxides (i) alter the speciation, toxicity and mobility of metal(loid)s such as chromium and arsenic and (ii) degrade refractory organic compounds into labile forms, which may influence bacterial regrowth in DW distribution systems (Escobar and Randall, ). Second, our results suggest that DW treatment strongly selects for taxa capable of Mn(II) oxidation, potentially amplifying their role in chemical transformations such as those indicated above.…”

Variation of assimilable organic carbon during coagulation by aluminum and iron in drinking water treatment

“…While the removal of AOC has been extensively studied and optimized during biological processes (Hu et ai 1999;Escobar & Randall 2001;Lehtola et al 2001), limited studies have been focused on the variation of AOC in conventional water treatment, especially during the coagulation stage. Coagulation may be an essential step in reducing the concentration of AOC in drinking water.…”

Drinking Water: Factors Affecting the Quality of Drinking Water

“…The BDOC concentration is calculated as a difference between the initial DOC and the minimal concentration of the latter observable during the incubation period [63]. It should be noted that some researchers underline the importance of separate identification of assimilated organic carbon (AOC) in which BDOC may be considered as part of AOC [55,[65][66][67][68]. In addition, these researchers believe that it is the content of AOC which correlates with the secondary bacterial growth and is a measure of the bacterial mass, while BDOC is a DOC fraction, which may be assimilated and mineralized by heterotrophic microorganisms [68].…”