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In this project, the effect of chlorite, copperion and chloramine on nitrification in a simulated household plumbing system wasinvestigated. A modified version of the CDC reactors developed at the Center for BiofilmEngineering at Montana State University was used to simulate a household plumbing system. Two sets of reactorswere used; each set consists of four reactors containing either PVC or copper as a couponmaterial. These reactors were fed water with 4 ppm humics as the organic carbon sourceand ammonium sulfate (0.71 ppm) as the nitrogen source and biologically treated tapwater to supply the bacterial population. Water in the reactors was stagnant for eighthours and then flowed for five minutes.After more than a year of operation all reactors showed signs of complete nitrification. Inone PVC reactor, copper sulfate was introduced with the influent water at an initialconcentration of 15 ppb and gradually it was increased to 1.3 ppm, allowing a two weekexposure time for every concentration. To ensure that most of the copper was in the ionicform, the pH of the influent was then gradually lowered to 6.6. No significant change innitrification was observed under any of these conditions.In the second investigation, chlorite, which has been shown to inhibit nitrification indrinking water systems, was introduced in a copper and a PVC reactor. Initially chloritewas added at 0.2 ppm and gradually increased to 2.0 ppm and finally a shock load of 20ppm was applied. The effect of chlorite on the PVC system was not significant but in thecopper system it inhibited nitrification only at 20 ppm.In the final stage of the project, different chlorine to ammonia ratios of monochloraminewere introduced to both PVC and copper reactors. The initial ratio was 0.5:1 chlorine toammonia, which was incrementally increased to 5:1. Only the 5:1 ratio ofmonochloramine was effective in controlling nitrification, but was not able to stop itcompletely. After eight weeks of exposure at the 5:1 ratio, monochloramine wasdiscontinued. The copper reactor regained full nitrification ability within three weeks butthe PVC reactor required six weeks. Includes 13 references, table.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 6File Size: 1 file , 710 KB