Water Chemistry and Growth ofNitrifying Bacteria in Drinking Water Distribution System

摘要

The impact of nutrients on growth of nitrifying bacteria is investigated under extremerncircumstances encountered in premise plumbing. Growth of nitrifying bacteria used inrnthis study could not be maintained long-term on glass pipes during days of stagnationrnbetween introduction of fresh water. However, if pieces of concrete were present,rngrowth was greatly stimulated. With continuous inoculation, nitrifying bacteria couldrnnot oxidize ammonia in stainless steel and pure lead pipes for a month of exposure, butrncould do so thereafter. Similar effects were observed after three months for galvanizedrniron but not in copper pipe after five months. Studies of nitrification in glass pipernrevealed that zinc levels above 150 ppb and copper levels above 500 ppb inhibitedrnnitrification. Phosphorus levels below 1 ppm, calcium below 0.27 ppm and potassiumrnbelow 3.89 ppm were associated with lower levels of nitrification. Other elementsrnincluding magnesium, molybdenum, cobalt, manganese, chelated iron, iron, nickel,rnchromium, tin, lead, aluminum did not have a strong effect on nitrification at levelsrnencountered in drinking water. Control of nutrients including phosphate could be anrnimportant strategy to prevention of nitrification.