玉米淀粉废水强化混凝与反硝化脱氮除磷技术研究

摘要

Considering the limit-exceeding problems of nitrogen and phosphorus in current cornstarch wastewater treatment, two solutions were put forward: one is to remove some pollutants by enhanced flocculation at the pretreatment stage; the other is to utilize the effluent of primary sedimentation tank as a carbon source for denitrification. The wastewater was treated by ferric chloride, aluminum sulfate, chitosan, and sodium alginate as flocculants, and optimum conditions were determined by single factor coagulation tests. The results showed that the ferric chloride was the suitable flocculant for treatment of cornstarch wastewater. When the dosing quantity of ferric chloride coagulant was 0. 40 g∕L, pH was 4, temperature was 35 ℃, the removal rates of TP, SS, TN and CODCr were 93. 5%, 94. 8%, 10. 8% and 10. 7%, respectively. The pollutant degradation characteristics and dynamic characteristics were studied by sequencing batch reactor with the effluent of primary sedimentation tank as the carbon source for denitrification, and Monod equation and piecewise zero-order kinetic model were used to fit the experimental data. The results showed that NO2--N accumulation was found in the denitrification process, and the accumulation rate was 61%. The predicted values of simulation parameters using Monod equation fit well with the measured data, and the maximum degradation rates of NO3--N、NO2--N and NOx--N were 24. 21, 12. 78 and 15. 97 mg∕( g MLVSS·h) respectively. The concentrations of NOx--N was also fit well by piecewise zero-order kinetic model and the denitrification rates of stage 1 and 2 were 16. 09 and 8. 71 mg∕(g MLVSS·h) respectively.%针对现行玉米淀粉废水处理工艺出水氮、磷易超标的问题,提出2种提高脱氮除磷潜能的解决方案：在预处理阶段设置混凝工艺强化去除部分污染物；在反硝化阶段引入部分竖流沉淀池(初沉池)出水作为补充碳源。通过设计单因素混凝试验,对比氯化铁、硫酸铝、壳聚糖、海藻酸钠4种絮凝剂对污染物的去除效果。结果表明：氯化铁较适合作玉米淀粉废水处理絮凝剂,当氯化铁投加量为0．40 g∕L,pH 为4,温度为35℃时,TP、SS、TN 和 CODCr的去除率分别为93．5%、94．8%、10．8%和10．7%。采用序批式反应器,研究了以淀粉废水处理过程中的初沉池出水作为反硝化碳源的污染物降解特性与动力学特性；分别采用基于Monod方程的微分方程模型和分段零级反应动力学模型拟合试验数据。结果表明：反硝化过程中存在NO2--N积累现象,NO2--N最大积累率为61%；采用基于Monod方程的微分方程模型,能够很好地拟合水解酸化段废水作为碳源的反硝化过程中NO3--N、NO2--N以及NOx--N( NO3--N与NO2--N当量总和)浓度的变化趋势,NO3--N、NO2--N以及NOx--N的最大降解速率分别为24．21、12．78和15．97 mg∕( g·h)(以MLVSS计)；分段零级动力学模型能较好拟合NOx--N浓度随时间的变化趋势,阶段1和阶段2的反硝化速率分别为16．09和8．71 mg∕( g·h)(以MLVSS计)。