Multiple fouling dynamics, interactions and synergistic effects in brackish surface water distribution systems

The occurrence of legionellae in the hot water distribution systems of 67 buildings located in different parts of Finland was studied. Most of the buildings were apartment buildings. They had different hot water temperatures, and some received their cold potable water from surface water plants and some from ground water plants. Hot water samples were taken from taps, showers, and water mains just before and after the heat exchanger. Legionella pneumophila was isolated from 30% of the distribution systems. In the legionella-positive samples the legionella concentration varied from < 50 to 3.2 × 105 colony-forming units (cfu)/L (mean 2.7 × 103 cfu/L). The highest concentration of legionellae was found in the shower water. Legionellae appeared more often and with higher concentrations in hot water systems using cold water processed in surface water plants than in hot water systems associated with ground water plants. A high organic matter content in surface waters might favor the occurrence of legionellae and also the growth of other heterotrophic microbes. Mean water temperature just after heating was slightly higher in the legionella-negative systems than in the legionella-positive systems (53.5 vs. 51.5 °C).Key words: Legionella, organic carbon, hot water distribution system, water temperature.

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Experience in controlling Asellus aquaticus in water distribution systems

Water Science & Technology Water Supply ◽

10.2166/ws.2001.0040 ◽

2001 ◽

Vol 1 (2) ◽

pp. 217-223

Author(s):

A. Oleszkiewicz ◽

M. Geringer d'Oedenberg ◽

J. Chapman

Keyword(s):

Surface Water ◽

Peracetic Acid ◽

Distribution System ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Water Reservoir ◽

Distribution Networks ◽

Average Dose ◽

Asellus Aquaticus

Asellus aquaticus is one of the nuisance organisms found in water distribution systems. Case studies of operations aimed at control of this crustacean and its disinfestation, carried out in two water distribution networks: in Pevensey Bay (Eastbourne, UK) and in Gdansk (Poland), are presented. Raw water reservoir receiving surface water was the source of infestation in Pevensey Bay. In Gdansk A. aquaticus probably penetrated the water distribution system with surface water getting into a leaky collecting well receiving groundwater from a chalk aquifer. The presence of organic matter in water entering the systems seemed to favour the infestation. Chemical treatment with pyrethrins (Pevensey Bay) and peracetic acid/hydrogen peroxide preparation (Gdansk) was used. The concentration of pyrethrins was 10 (g/dm3 and the average dose of peracetic acid was 4 mg/dm3. Both chemical treatments were found quite effective, however, some sections of the (much larger than Pevensey Bay) distribution network in Gdansk were not completely cleaned of the infestation.

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Evaluation of the impact of disinfection processes on the formation of biofilms in potable surface water distribution systems

Water Science & Technology ◽

10.2166/wst.1998.0817 ◽

1998 ◽

Vol 38 (8-9) ◽

pp. 283-289 ◽

Cited By ~ 18

Author(s):

Maggy N. B. Momba ◽

T. E. Cloete ◽

S. N. Venter ◽

R. Kfir

Keyword(s):

Hydrogen Peroxide ◽

Surface Water ◽

Biofilm Formation ◽

Distribution Systems ◽

Water Distribution ◽

Water Distribution Systems ◽

Residual Effect ◽

Viable Count ◽

Significant Difference ◽

The Impact

In this study, surface water was used to evaluate the impact of disinfection processes (chlorination, chloramination, ozonation, UV irradiation and hydrogen peroxide) on biofilm formation in potable water distribution systems. Biofilm formation was obvious, even in the presence of residual disinfectant concentrations (16.5 mgl−1 hydrogen peroxide, 1 mg−1 monochloramine, 0.2 mgl−1 free chlorine) within the first day after disinfection in the laboratory scale unit. The yield in viable count was higher on stainless steel coupons than on cement coupons within the first 8 days. Viable bacteria numbers on cement coupons were similar (±2 log cfu.cm−2) in chlorinated, ozonated and in the control. Biofilm formation was related to the depletion of residual disinfectant concentration. Monochloramine and hydrogen peroxide had a longer residual effect controlling growth of biofilm cells in the system for a longer period before regrowth occurred. Once no residual concentrations could be detected there was no significant difference between the viable bacterial counts on any of the coupons in the various systems.

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