Technological design and purification performance of a recirculation aquaculture system based on constructed wetlands

How to purify and reuse the aquaculture water becomes a challenge problem to sustainable aquaculture in China, as well as in the world. Constructed wetland, acting as an ecological engineering alternative, is capable of reducing suspended solids, BOD, nitrogen, phosphorus and heavy metals from wastewater of many sources. The integrated vertical-flow constructed wetlands (IVCW) combined with pond culture to establish a new aquaculture-wetland ecosystem was firstly designed; the feasibility of IVCW for purifying and reusing polluted water and the effluent from fish cultivating ponds was evaluated. During the 9 months' operating period, the IVCW was operated at various hydraulic loading rates, 313, 469, 625 mm/d and 781 mm/d, the removal rates of TSS, COD_Cr and BOD₅ were 80.5%～82.9%, 45.2%～64.2% and 61.0%～77.0%，respectively; Those of NH^＋₄-N, NO^-₃-N and TN were 51.5%～67.8%, -90.6%～40.0% and 29.1%～68.6%, respectively; TP and IP were 72.7%～89.1% and 0～33.3%; a good performance was also obtained for removing bacteria, total coliforms and algae. All parameters except dissolved oxygen of outlet from IVCW could meet the standard of national fishery water quality. The preliminary result shows that constructed wetlands for wastewater treatment and reuse in aquaculture have broad future.