A simple mathematical model of water quality control for recirculating pond on a shrimp farm

Abstract

— In many countries, shrimp is one of the most valuable export commodities. Shrimp farming raises a number of issues, including shrimp waste contamination, shrimp feed residues, and biochemical reactions in the shrimp pond. In this research, mathematical models were utilized to analyze the water quality in shrimp ponds and wastewater treatment ponds for circulation systems, with BOD serving as a significant indication of water quality. In the circulation system, two separate ponds were investigated: the shrimp pond and the wastewater treatment pond. The shrimp pond was tested for pollutant levels generated by shrimp excretion, shrimp feed residues, and biochemical reactions. A Chaipattana low-speed surface aerator was used to treat the shrimp pond pollutants, and some of the waste was drained to the next pond. The pollutant levels in the treatment pond were investigated. This pond is polluted by sewage from the shrimp pond as well as biological reactions. Lower-efficiency aerators treat the contaminants in the treatment pond, and part of the waste is transferred to the next pond. The advection equation is being used to describe the pollutant concentration in two ponds, and Runge-Kutta order 4 is also being used to determine the approximated solution to the problem. The results of the mathematical model are presented in graphs and tables comparing the pollutant concentrations in many cases. The last section shows an example of wastewater treatment by aerator in a shrimp pond. It was found to reduce the number of days needed for wastewater treatment. The water quality could generate shrimp in this condition, but the water quality could not grow shrimp if the aerator was not turned on the first day of shrimp farming and then turned on the next day. On the first day of shrimp farming, the aerator should not be turned off since the pollutant concentration would be high, making wastewater treatment difficult the next day. In addition, the research showed a maximum five-day reduction in wastewater treatment time (last days of the month). When wastewater is treated every other day, every three days, or every five days, the pollutant concentration must be lower than the minimum necessary for shrimp farming. It can also be used to reduce the cost of water treatment by saving energy.