Nitrifying Bacteria in Drinking Water

Nitrifying bacteria rapidly colonized iron, plastic, and lead materials, more slowly colonized galvanized and stainless steel, and had difficulty surviving in relatively new copper pipes under conditions found in premise plumbing. Nitrification significantly decreased pH and dissolved oxygen (DO) in all pipe materials and sometimes caused sporadic sloughing of very high total organic carbon concentrations from cast‐iron coupons. The release of zinc from galvanized iron was reduced six times because of lower DO resulting from nitrification. Nitrification did not significantly increase weight loss as a result of corrosion among the three disinfectant conditions (no disinfectant, chlorine, chloramine plus nitrification) for cast‐iron, new lead, old lead, copper, galvanized‐iron, stainless‐steel, or concrete pipe material. Nitrification did not cause copper pitting corrosion or increase copper release in this study.

mentioning

confidence: 99%

Effect of nitrification on corrosion of galvanized iron, copper, and concrete

Zhang¹,

Griffin²,

Edwards³

2010

“…Nitrification occurs as a result of the presence of free ammonia, which is produced by chloramine decay, overdosing of ammonia during chloramine formation, or naturally occurring ammonia in groundwater (Zhang et al, 2009; Sathasivan et al, 2005; Wolfe & Lieu, 2001; Norton & LeChevallier, 1997; Wilczak et al, 1996). Because the nitrite produced from nitrification accelerates the decay of chloramine residuals (Valentine, 1984), higher rates of HPC growth may occur with chloramination than with chlorination.…”

mentioning

confidence: 99%

Accelerated chloramine decay and microbial growth by nitrification in premise plumbing

Zhang¹,

Edwards²

2009

Chloramine decay rates are accelerated by nitrifier colonization of premise plumbing, which compromises the effectiveness of secondary disinfection. As expected, in the absence of nitrification, chloramine was more stable than chlorine; but in the presence of nitrification, the relative stability (and efficacy) of the two disinfectants could be reversed. The net result with chloramination can be higher levels of heterotrophic bacteria in the bulk water and pipe biofilms than would be found with free chlorine. These experimental trends were confirmed using field data collected from homes in systems with active nitrification.

“…The alkalinity was added as inorganic carbon (NaHCO 3 ). The NH 3 level was 2 mg/L N, which is slightly higher than is typical at most utilities, but which is also lower than ammonia levels at some utilities where severe nitrification occurs (Zhang et al, 2009b; Wolfe & Lieu, 2001). Water in the pipes was changed twice a week, and nitrification activity was measured.…”

Section: Methodsmentioning

confidence: 70%

“…The pipes were kept horizontal between water changes, and each end was capped with a silicon stopper. Pipes were maintained at room temperature (20°C) and were covered with black plastic throughout the experiment to prevent possible light inhibition of nitrification through the translucent PVC (Wolfe & Lieu, 2001). After three months of inoculation, complete nitrification (defined in this article as 100% ammonia conversion to NO 3 within 24 h of stagnation) was confirmed to occur in PVC pipes.…”

Section: Methodsmentioning

confidence: 99%

“…The conversion of ammonia (NH 3 ) to nitrate (NO 3 ) by nitrifying bacteria (Zhang et al, 2009b; Wolfe & Lieu, 2001) poses an indirect health concern in drinking water systems. Nitrification can accelerate the loss of disinfectant residuals (Wolfe et al, 1988), enhance corrosion of water distribution system materials, or increase lead/copper contamination of water under at least some circumstances (Douglas et al, 2004; Murphy et al, 1997; Odell et al, 1996; Wilczak et al, 1996; Skadsen, 1993).…”

mentioning

confidence: 99%

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Nutrients and metals effects on nitrification in drinking water systems

Edwards¹

2010

The activity of nitrifying bacteria in potable water systems was strongly affected by nutrient levels and the presence of certain metals. Specifically, copper (Cu) and zinc (Zn) levels > 100 μg/L and phosphate levels < 5 μg/L inhibited nitrifier activity. This research also showed that inorganic carbon has important direct and indirect effects on nitrification because inorganic carbon (0.1 mg C/mg oxidized nitrogen) was required for autotrophic nitrifier growth, but higher inorganic carbon reduced the toxicity of Cu/Zn and can increase phosphate availability to nitrifying bacteria. Different pipe materials modify nutrient availability to nitrifiers and thus either inhibit or enhance nitrifier activity. For example, orthophosphate can leach to water during corrosion of some metallic alloys but can be removed from water during corrosion of other materials.