Abstract:

To verify the practical culturing effect of a previously designed circulating water treatment system based on heterotopic pond restoration technology, a large-scale multi-species saturating culture experiment was carried out for 3 years. The effects of the system on water quality control was evaluated by measuring the total nitrogen (TN), total phosphorus (TP), chemical oxygen consumption (COD_Mn) and chlorophyll (Chla) in a common freshwater fish culturing pond. The results showed that in the early stage of the experiment, the total nitrogen level (TP) of the circulating water of the pond reached Class III of the Environmental Quality Standards for Surface Water (GB 3838—2002), and the total phosphorus level (TN) reached Class III to V. The average removal rate of TP, TN, COD_Mn and Chla was 40.13%, 45.02%, 43.37% and 86.6%, respectively. The removal efficiency of the system was significant. In the late stage of the experiment, with the continuous increase of the feed input, although the efficiency of the circulating system was greatly improved, the data of each index were still higher than expected. This experiment provides a new idea for the treatment of large-scale aquaculture water by circulating water in freshwater ponds.

Key words: circulating water treatment system, freshwater pond, total nitrogen, total phosphorus, chemical oxygen demand, chlorophyll a, evaluation