An Ecological Engineering Pond Aquaculture Recirculating System for Effluent Purification and Water Quality Control

Water pollution arising from traditional pond aquaculture is a major problem facing China. A series of combined ecological engineering facilities composed of an ecological ditch, an ecological pond, and a subsurface flow constructed wetland together with three series-connected culture ponds were designed as an ecological engineering pond aquaculture recirculating system (EPAS) to control water quality and pollution from the effluent. Results from running experiment of the system revealed that, the mean removal rates of the ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP), potassium permanganate index (CODMn), and chlorophyll a (Chl-a) during the experiment period were 44.2, 47.6, 63.4, 61.5, and 83.0 by the ecological engineering facilities, respectively. With the fish density of 0.82kg/m(3) and daily water exchanges of 9.6%, the NH4+-N, TN, TP, CODMn, and Chl-a in the culture ponds were kept below 0.799 +/- 0.129, 3.015 +/- 0.427, 0.443 +/- 0.131, 7.172 +/- 2.071mg/L, and 3.098 +/- 1.046 mu g/L, respectively, which were significantly lower than those in the control pond (p<0.05). Compared with traditional static pond aquaculture, the EPAS constructed in this study could increase unit output from 0.75 to 0.82 (mean value) kg/m(3), and reduce the feed coefficient by 8.2%. These data implied that the EPAS might improve the water quality and provide a good culture environment, thus contributing to improve the culture efficacy.