Escherichia coli Behavior in the Presence of Organic Matter Released by Algae Exposed to Water Treatment Chemicals

Abstract

When exposed to oxidation, algae release dissolved organic matter with significant carbohydrate (52%) and biodegradable (55 to 74%) fractions. This study examined whether algal organic matter (AOM) added in drinking water can compromise water biological stability by supporting bacterial survival. Escherichia coli (1.3 ؋ 10 5 cells ml ؊1 ) was inoculated in sterile dechlorinated tap water supplemented with various qualities of organic substrate, such as the organic matter coming from chlorinated algae, ozonated algae, and acetate (model molecule) to add 0.2 ؎ 0.1 mg of biodegradable dissolved organic carbon (BDOC) liter ؊1 . Despite equivalent levels of BDOC, E. coli behavior depended on the source of the added organic matter. The addition of AOM from chlorinated algae led to an E. coli growth equivalent to that in nonsupplemented tap water; the addition of AOM from ozonated algae allowed a 4-to 12-fold increase in E. coli proliferation compared to nonsupplemented tap water. Under our experimental conditions, 0.1 mg of algal BDOC was sufficient to support E. coli growth, whereas the 0.7 mg of BDOC liter ؊1 initially present in drinking water and an additional 0.2 mg of BDOC acetate liter ؊1 were not sufficient. Better maintenance of E. coli cultivability was also observed when AOM was added; cultivability was even increased after addition of AOM from ozonated algae. AOM, likely to be present in treatment plants during algal blooms, and thus potentially in the treated water may compromise water biological stability.In spite of the disinfection processes, bacterial proliferation can be observed in drinking water distribution network systems (20,26,37,42) proving that certain bacterial populations are able to adapt, transiently or permanently, to the oligotrophic conditions of distribution networks (16,17). This phenomenon has been described for fecal indicators such as coliform bacteria, particularly Escherichia coli (16), and poses the problem of compliance with water quality health regulations.Although multiple factors certainly affect microbial growth phenomena, organic matter in treated waters, mainly the biodegradable fraction, has a determining effect since it provides a carbon and energy source essential to the growth of heterotrophic bacteria, including coliforms (16,19,25,38,39,42). Atypical events (algal bloom, swelling, rainfall, etc.) capable of modifying the quality of the organic matter in raw and treated waters have been suggested to be a catalyst for coliform growth (3, 18, 23). Lake et al. (15) showed that there is a strong link between the end of the algal bloom and the presence of coliforms in the distribution system, leading to a situation incompatible with health standards. Algal products in the treated water were suspected of providing a good nutritional source for bacterial regrowth in the distribution system. In addition to the natural capacity of algae to secrete organic compounds, massive contamination at the inlet of a treatment plant using preoxidation can lead to algal cell lysis and re...

Regrowth of Potential Opportunistic Pathogens and Algae in Reclaimed-Water Distribution Systems

“…Furthermore, decaying algal cells release organic carbon, which in turn increases the demand for disinfectant and increases turbidity. Algal cellular fractions can be a significant source of biodegradable carbon, especially in the presence of an oxidant such as chlorine (6,19,32). All of these factors stimulate bacterial growth, resulting in a loss of oxygen and creating anoxic conditions, which in turn favor anaerobes, such as sulfur-reducing bacteria, as documented for the systems with open reservoirs in which there were also high hydrogen sulfide concentrations.…”

Sunlight inactivation of faecal coliforms in domestic wastewater

“…The non-linear relationship between algal density and decay rates suggests that other factors apart from toxic oxygen molecules are involved in FC inactivation. Lyses of algal cells occur particularly at very high algal densities without any form of induction and this lysis leads to the release of algal organic matter (AOM), some of which may serve as sensitizers by absorbing electromagnetic radiation, transmitting it to faecal bacteria cell membrane leading to its destruction [1,12,15]. Others that are not capable sensitizers may serve as carbon and energy sources for faecal bacteria survival [4].…”

Variation of an indicator ofEscherichia colipersistence from surface waters of mixed-use watersheds, and relationship with environmental factors

“…These would include biologically-mediated factors such as predation (McCambridge and McMeekin, 1980) and viral lysis (Carlucci and Pramer, 1960b); and water quality parameters including the presence of antibiotics or other inhibitors (Carlucci and Pramer, 1960a), organic and particulate matter (Bouteleux et al, 2005), and nutrients (Cook and Bolster, 2007). Laboratory incubations were carried out at 30 xC, which corresponded to the maximum water temperature recorded in the field during the sampling period (data not shown).…”

“…Environmental factors that affect E. coli viability in natural waters include water temperature (Faust et al, 1975), predation (McCambridge and McMeekin, 1980), antibiotics (Carlucci and Pramer, 1960a), organic matter (Bouteleux et al, 2005), viral lysis (Carlucci and Pramer, 1960b), nutrients (Topp et al, 2003;Cook and Bolster, 2007), and irradiation with UV and visible light (Noble et al, 2004).…”