生态沟—根孔湿地系统对大规模水产养殖尾水的净化作用

Purification of Tail Water from Large-scale Aquaculture by Ecological Ditch-Root Channel Wetland System

[目的]分析基于根孔湿地构建的生态沟渠对水产养殖尾水的净化效果,为大面积养殖区循环养殖和污染减量化提供科学参考。[方法]选取养殖面积超过500 hm^(2)的宁夏回族自治区贺兰县寇家湖园区进行试验,以原有农田排水沟渠为基础,在沟渠两岸构建根孔湿地提升其净化能力,于2022和2023年对沿程水体进行采样,分析该系统对大面积水产养殖区产生的养殖尾水的净化效果。[结果]2022年系统初运行时生态沟渠能有效净化养殖尾水中的磷酸盐、亚硝酸盐和氨氮,净化率分别为97.15%,96.00%和59.65%;2023年日常运行时该生态沟渠能有效净化大面积养殖区日常养殖过程中产生的养殖尾水,对磷酸盐、亚硝酸盐和氨氮净化率最高可达到87.70%,72.89%和83.15%,系统净化末端氨氮浓度低于0.5 mg/L,达到《地表水环境质量标准(GB3838—2002)》的Ⅱ类标准;缩短1/2的净化路程后,生态沟渠对养殖尾水依旧具有较好的净化效果,两个长度下生态沟渠出水口的营养盐浓度无显著性差异(p<0.05)。[结论]基于根孔湿地构建的生态沟渠能有效处理大面积水产养殖区日常养殖过程中产生的尾水,可实现养殖尾水的循环利用。

[Objective] The capacity of a drainage ditch modified as a root channel wetland(ecological ditch) to purify aquaculture tail water was analysed in order to provide a scientific reference for circular aquaculture and pollution reduction in areas of large-scale aquaculture.[Methods] The study site was Koujia Lake Park,in Helan County,Ningxia Hui Autonomous Region,with an aquaculture area exceeding 500 hectares.We constructed experimental root channel wetlands on both sides of an original farmland drainage ditch to improve the purification capacity of the ditch.To evaluate the purification effect of this ecological ditch system on the tail water from large-scale aquaculture,we collected water samples in the ecological ditch in 2022 and 2023.[Results] In 2022,at the onset of its operation,the ecological ditch effectively purified phosphate,nitrite,and ammonia nitrogen in the aquaculture tail water,with the purification rate being 97.15%,96.00%,and 59.65%,respectively.In 2023,the ecological ditch effectively purified the aquaculture tail water on a daily basis.The maximum purification rate for phosphate,nitrite,and ammonia nitrogen was 87.70%,72.89%,and 83.15%,respectively.The concentration of ammonia nitrogen at the purification end of the system was less than 0.5 mg/L,reaching the Class Ⅱ standard of the ‘Surface Water Environmental Quality Standard'(GB3838-2002).After shortening the purification distance by half,the ecological ditch still had a good purification effect on the aquaculture tail water,with no significant increase in the nutrient concentration at the ditch outlet(p<0.05).[Conclusion] The construction of a root channel wetland around the drainage ditch could effectively purify the tail water generated in the daily aquaculture operations across a large-scale aquaculture area,and achieve water recycling.