利用白云石石灰去除和回收污泥消化液中磷的响应面法优化研究

Response surface methodology for optimization of phosphate removal and recovery by dolomitic lime from sludge digestion supernatant

针对污水处理厂污泥消化上清液的组成特点,利用白云石石灰去除和回收污泥消化液中的磷.同时,根据Box-Behnken Design实验设计及响应面法进行工艺优化,对实验过程中药剂的投加量(X1)、反应初始pH值(X2)及反应温度(X3)3个重要影响因素的单独作用及各因素之间的交互作用进行了考察,并建立了数学模型.结果表明,响应曲面模型拟合度较高(R2为0.9680),回归方程中X1、X2、X3、X1X3、X21、X22对磷去除率影响显著;综合考虑操作的简便性及经济性,选取最佳条件组合为:白云石石灰投加量300 mg·L-1,初始pH值9.0,反应温度25℃,验证实验结果为89.08%,与预测值相比偏差为0.39%.通过扫描电子显微镜、傅里叶变换红外光谱和X射线衍射表征技术分析结晶沉淀组成和晶形特征,表明产物中含有磷酸铵镁晶体、无定形磷酸钙及杂质碳酸钙等.

Dolomitic lime was utilized to recover phosphate from sludge digestion supernatant. The linear,quadratic and interaction effects of dolomitic lime dosage（X1）,initial reacting pH values（X2） and temperature（X3） on the removal efficiency were investigated using Box-Behnken Design experiments and response surface methodology. An empirical mathematical model describing the relationship between response values（phosphate removal rates,denoted as Y） and the influence factors was presented. The results demonstrated that regression equation fit well with experimental data（R2equals to 0. 9680）. X1,X2,X3,X1X3,X21and X22had significant effects on phosphate recovery efficiency. Considering simplicity and efficiency of operation,the optimum conditions of dolomitic lime 300 mg·L-1,initial pH 9. 0 and 25. 0 ℃ were selected. Under the optimum conditions the removal rate of phosphate was 89. 08% with 0. 39% of relative deviation between the experimental and predicted values. Scanning electron microscopy,Fourier transform infrared spectroscopy and X-ray diffraction were performed to characterize the composition of the recovered products. It was shown that the recovered products consisted of ammonium magnesium phosphate and amorphous calcium phosphate,as well as impurity,i. e. calcium carbonate.