An integrated wastewater treatment system for land-based fish-farming

A newly developed low cost system for fish-farm wastewater treatment was evaluated. The system consisted two major parts: (1) a new type of square tank design with two separate outlets, i.e. one centrally positioned high solids concentration outlet and one corner located low solids concentration primary outlet; and (2) a stationary bowed screen for solid removal from the high solids effluent. Removal rates for the particle outlet were on average 43.2% total phosphorus (TP) and 7.3% TN. The mean TP, TN, chemical oxygen demand (COD) and TS removal rates of the bowed screen were 49.3, 42.7, 48.0, and 74.4%, respectively. TP and TN waste removal rates for the whole system were 21.3 and 3.1%, respectively. The self-cleaning in the tank was poor at the start of the trials, but improved throughout the experimental period as fish density increased, thus also increasing the removal rates for the whole system.