Nitrification - Seasonal Startups

Aug. 2, 2002
A 3 MGD (11,300 m3d) New England wastewater plant needs to nitrify each year from May 1 to October 1 in order to meet seasonal permit limits. Historically, plant operators tried to induce nitrification by extending the MCRT to 20 days or greater. Using this strategy, nitrification often did not begin until mid-June or mid-July and remained unpredictable throughout the season. During the winter of 1990, Novozymes Biologicals was contacted to determine if a bioaugmentation program could help the plant achieve its goals for a rapid seasonal start-up. After reviewing the plant, a site-specific 10-day dosing protocol using Novozymes Biologicals? BI-CHEM® 1010N 20xS, a concentrated blend of ammonia- and nitrite-oxidizing bacteria, was recommended. The plant has two aeration basins in parallel, each consisting of a large 0.6 MG (2270 m3) and small 0.2 MG (750 m3) cell. To increase the dosing efficiency, one of the small cells was isolated and converted into an on-site growth reactor. After degrading the remaining BOD, the cell was fed with ammonia and 30 lbs (13.6 kg) of BI-CHEM® 1010N 20xS over the next five days, allowing the nitrifying bacteria to grow and multiply. On the fifth day, the isolated cell was reopened to the system. One pound of BI-CHEM® 1010N 20xS was added to the front of the aeration basins over the next five days. Within four days of opening the cell, the effluent ammonia levels dropped below permit levels. That year, the seasonal permit was met during the month of May for the first time since the plant had been in operation. Ten years later, the plant successfully continues to use BI-CHEM 1010N 20xS for starting nitrification.