Treatment effects of pond aquaculture wastewater using a Field-scale Combined Ecological Treatment System and the associated microbial characteristics

Avoiding and mitigating the introduction of harmful effluent into the environment must be a key part of rural pond aquaculture development in order to minimize pollution impacts. We constructed a novel Field-scale Combined Ecological Treatment System (FCETS) involving multistage purification to efficiently remove nutrients from pond aquaculture wastewater. Pollutant removal efficiency is a crucial indicator for the performance evaluation in aquaculture wastewater treatment. Therefore, current study aimed to investigate the pollutant removal efficiency of FCETS for wastewater treatment. Results show that after a prolonged operation period, FCETS was able to remove TSS, TN, TP, COD, NO3  -N, NH4+-N and NO2  -N with 69.6 & PLUSMN; 6.6%, 72.1 & PLUSMN; 7.0%, 77.0 & PLUSMN; 6.6%, 58.1 & PLUSMN; 6.6%, 65.7 & PLUSMN; 7.2%, 85.0 & PLUSMN; 4.1% and 81.0 & PLUSMN; 6.4%, respectively and removal performance was the best in summer, followed by autumn, spring and winter. Further investigations were carried out to investigate the removal efficiency of each unit in FCETS. Findings reveal that TSS, TN and TP were mainly treated in CSP, FSP and EP. AP play a leading role in the CODMn removal process with the average of 15.6 & PLUSMN; 1.8%, followed by EP with the average of 12.2 & PLUSMN; 1.5%. EP contributed the most to the removal of NO3  -N, NH4+-N and NO2  -N, with the average rates of 23.6 & PLUSMN; 2.5%, 20.6 & PLUSMN; 1.5% and 32.7 & PLUSMN; 3.5%, respectively. Results also reveal that the influencing factors such as hydraulic retention time (HRT), water temperature (W.T) and functional microorganism have significant effects on the purifying performance of FCETS. Thus, based on these, operation and maintenance methods of FCETS were suggest to ensure standard emission. Overall, the results of the present study will contribute to the feasibility of contamination-free aquaculture and illustrate the microbial characteristics of nutrient metabolism in aquaculture wastewater treatment systems.