基于微滤技术供水厂的臭氧预氧化前置工艺中臭氧投加量的优化

Optimization of ozone dosage in the pre-oxidation process of water treatment plants with microfiltration technology

通过臭氧预氧化降解水体中溶解性有机物(DOM)对DOM的氧化效果以及微滤(MF)膜污染的缓和效应进行了研究,并分析了臭氧氧化过程中光谱参数变化的规律,进而提出一种通过多目标优化模型确定最佳臭氧投加量的方法。结果表明,臭氧预氧化技术能够将中等分子质量的芳香类DOM转化为低分子质量的有机化合物,对应的UV_(254)去除率最高可达90.34%,从而显著改变了MF进水的光谱特性。此外,臭氧预氧化还显著缓解了DOM造成的膜污染,膜污染指数(FI)最多可降低51.49%。根据上述结果可建立多目标优化模型,并用于确定臭氧预氧化-膜过滤工艺最佳臭氧投加量。根据层次分析法,对SUVA_(254)、FI和臭氧利用率3个客观指标分配不同的权重,以满足不同饮用水厂的需求。此外,模型分析中可用光谱斜率作为SUVA254的替代参数,特别是S_(275~295)(R^(2)=0.9797),用UV_(254)作为FI的替代参数(R^(2)=0.8799),进而简化模型系数的获取。以上研究结果可为水厂在实际应用中优化臭氧投加量、综合提高水处理效果、缓解膜污染并降低运行成本提供参考。

Through ozone pre-oxidation to degrade dissolved organic matter(DOM)in water,the efficiency of pre-ozonation for dissolved organic matter(DOM)removal and membrane fouling control were studied,and the variations in the UV-vis spectra of the treated water were analyzed.Furthermore,a multi-objective optimization model was proposed for identifying the optimal ozone doses for pre-oxidation.The results showed that preozonation could transform aromatic DOM with medium molecular weight into small organics,the corresponding UV_(254) removal efficiencies could not exceed 90.34%,which significantly changed the spectral characteristics of the feedwater to the membrane filter.Moreover,pre-ozonation noticeably mitigated membrane fouling by DOM,and the fouling index(FI)decreased by no higher than 51.49%.Accordingly,the simplified multi-objective optimization model was developed to identify suitable ozone dosing for the integrated ozonation pre-oxidation-microfiltration process.Different weights were assigned to three objective factors,i.e.,SUVA_(254),FI,and ozone utilization ratio through the analytic hierarchy process,to account for the diverse needs of drinking water treatment plants(DWTPs).To further simplify instrumental requirements,SUVA_(254) used in the model may be replaced with the spectral slope parameters,especially S_(275~295)(R2=0.9797),and FI may be replaced with UV_(254)(R^(2)=0.8799).These findings provided useful guidance for DWTPs to optimize ozone dosage,comprehensively improve DOM removal,mitigate membrane fouling,and reduce operational costs.