Effect of ecological interception system in reducing non-point source pollution from vegetable fields

Abstract: The ever-worsening problem of non-point source pollution has plagued vegetable industries worldwide. This study attempts to tackle this problem using an ecological interception system in Taihu basin, Zhejiang province, to examine the effects of removal of nitrogen (N) and phosphorous (P) from the effluents of vegetable fields. The system consisted of ecological ditches with filtration apparatus optimized for location, efficiency, and cost control. Construction of the system started in September 2010 and was completed and put into operation in April 2011. The results showed total-N removal rates of 79.75% and 88.86% in July 2011 and July 2012 respectively, which were 2.47 and 3.02 times the controls for the same years. The total-P removals in July 2011 and July 2012 were 86.74% and 96.35% respectively, which were 2.39 and 2.84 times of the controls for the same years. Compared to 2010, the total-N and total-P concentrations in the effluents in 2011 and 2012 were significantly reduced with total-N concentrations at 2.23-5.91 and 1.51-4.62 mg/L respectively and total-P concentrations 0.33-1.39 and 0.14-0.97 mg/L, respectively. The overall removals of nitrogen in 2011 and 2012 were 33%-52% and 43%-67% respectively and phosphorous 23%-59% and 43%-82% respectively. The removals were the highest during the rainy season June through September and higher in 2012 than in 2011.Not only did the project fully improve absorption and interception of nitrogen and phosphorus and other nutrients from vegetable waste water, it also extended the hydraulic retention time, reduced the emission load of vegetable waste water, and increased cycle utilization rate of vegetable wastewater. As a proof of concept, the project was a huge success, showing promising results not only for wastewater treatment but also landscape beautification and economic benefits for the region. There is no denying the important practical significance of exploring environmentally friendly high-efficiency systems for ecological agricultural uses.