Use of Bacillus consortium in waste digestion and pathogen control in shrimp aquaculture

Abstract

The wastewater from shrimp aquaculture industry contains high concentration of nitrogen and carbon. The use of microorganisms to remove nitrogen and carbon from shrimp aquaculture wastewater was investigated. A consortium of Bacillus species was used to enhance the performance of a sequencing batch reactor (SBR) for the treatment of shrimp aquaculture wastewater. An SBR is a variation of the activated sludge biological treatment process. This process accomplishes equalization, aeration, and clarification in a timed sequence in a single reactor basin to take the place of multiple tanks in conventional treatment systems. This is achieved through sequencing stages, which includes fill, react, settle, decant, and idle. The shrimp wastewater initially contained a high concentration of carbon and nitrogen. By operating the reactor sequentially, viz, aerobic, anaerobic, and aerobic modes, nitrification and denitrification were achieved as well as removal of carbon. Specifically, the initial chemical oxygen demand concentration of 1996 mg/L was reduced to 4 mg/L within eight days of reactor operation. Ammonia in the wastewater was nitrified within three days. The denitrification of nitrate was achieved by the anaerobic process and more than 99% removal of nitrogen was observed. The addition of Bacillus consortium also controlled the growth of shrimp pathogen, Vibrio harveyi in the wastewater.