According to the nitrogen and phosphorus requirements of corn-cauliflower crop rotation farming,the engineering of ecologically returning sewage from the Chongming Beibaxiao Dairy Farm to its surrounding cropland was designed and constructed. The selected cropland was on the eastern side of the farm and the area was 35 hnv to ensure the liquid fertilizer being absorbed completely. A sprinkler irrigation system or furrow irrigation was used and 15 irrigation plugs were evenly distributed in the cropland.The total investment of the project was ￥746 200 and the annual operating cost was approximately ￥27 400.The engineering practice indicated that the normal crop yields could be gained and the discharged amounts of the farm's pollutants were reduced by 9.01 t/a in TN,0.65 t/a in TP and 64. 66 t/a in COD. Also the amounts of applied urea and calcium superphosphate were decreased by 13.07 t/a and 55.99 t/a respectively,thus annually reducing ￥3 300/hm2 in investment and having significant environmental and economic benefits.%根据玉米-花菜轮作田作物氮磷养分需求,对上海市崇明北八滧奶牛养殖小区污水生态还田工程进行工艺设计和施工建造,匹配农田选择场区东侧田块35 hm2,以确保能够完全消纳奶牛场液肥,并采用压力喷灌系统进行灌溉或沟灌,田间均匀布置喷灌栓15个,工程总投资74.62万元(人民币,下同),年运行费用约2.74万元.工程实践表明:在确保作物正常产量的同时,奶牛场污染物减排TN 9.01 t/a、TP 0.65 t/a、COD64.66 t/a；匹配农田节省尿素和过磷酸钙分别为13.07 t/a和55.99 t/a,折算减少投入0.33万元/(hm2·a),环境和经济效益显著.
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