Biological treatment of shrimp aquaculture wastewater

By Quenton Fontenot. One of the problems associated with rearing shrimp at high densities is the rapid accumulation of waste products, such as nitrogen and carbon. Raceway aquaculture systems usually solve this problem by filtering waste products from the water and disposing them as a concentrated sludge. Research being conducted at Nicholls State University is focusing on methods to reduce the amount of nitrogen and carbon in the form of chemical oxygen demand in the sludge with a sequencing batch reactor (SBR). The SBR is a single container that can be operated aerobically or anaerobically, and the timed sequence of aerobic and anaerobic periods is the key to reducing nitrogen and chemical oxygen demand. During the aerobic periods, nitrification is occurring and ammonia is being microbially converted to nitrate. During the anaerobic periods, denitrification is occurring and nitrate is microbially converted to nitrogen gas. By using a bench-scale SBR, researchers at NSU have been able to reduce the nitrogen and chemical oxygen demand in shrimp sludge-water virtually to zero. Also, initial results have shown a 20% reduction in total sludge volume. Future research includes the development of a pilot-scale SBR suitable for commercial shrimp aquaculture wastewater treatment, and feasible methods to remove the salt from the sludge.
Quenton C. Fontenot, Ph.D., Department of Biological Sciences, Nicholls State University, Thibodaux, LA 70310