Title: Nitrification treatment of swine wastewater under cold temperatures Authors
Submitted to: Air and Waste Management Annual Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2007
Publication Date: September 16, 2007
Citation: Vanotti, M.B., Sumino, T., Szogi, A.A. Nitrification treatment of swine wastewater under cold temperatures. In: International Symposium on Air Quality and Waste Management for Agriculture, 16-19 September, Broomfield, Colorado. 5 p. 2007 CDROM. Technical Abstract: In addition to N load, cold weather nitrification is an important consideration for stabilized performance of biological processes applied to continuous animal production systems. We conducted a winter simulation experiment in the laboratory to evaluate performance of immobilized bacteria under cold weather conditions. Bench fluidized reactors (1.2 L) containing 120 mL polyethylene glycol nitrifying pellets (10% v/v) were operated under continuous flow using swine wastewater containing 330-450 mg NH4-N/L and 140-290 mg BOD5/L. Water temperature in the reactors was controlled using a refrigerated circulating bath with car antifreeze liquid. Starting with 15ºC, and a hydraulic residence time (HRT) of 18 hrs, wastewater process temperatures were decreased 2.5-3ºC every three weeks to a lowest of 3ºC. Ammonia was completely removed in all of these runs, which precluded calculation of nitrification potential. For this reason, the continuous flow experiment was repeated using higher N loads obtained with HRT of 12 hrs, each temperature run lasting 2 weeks. In addition to continuous flow, a series of batch tests were also done to determine nitrification rate at cold temperatures with a different method, each batch temperature test lasting 8 hours and replicated 3 times. As expected, the effect of process temperature on nitrification rate was well described by the exponential equation. But nitrification activity was not severely affected by the lower temperatures in the experiment (3ºC), indicating acclimation of the entrapped nitrifying bacteria. Temperature coefficient (Q10) obtained was consistent between continuous flow and batch conditions and averaged 1.41. This means that nitrification rate decreased by 29% for each 10ºC decrease in water temperature. This is significantly different than the Q10 of 3 (70% rate decrease per 10ºC) commonly used to predict activity of nitrifying bacteria under cold weather conditions. Thus, the immobilized technology appears well suited for nitrification of high-ammonia livestock wastewater under cold weather conditions.