高铁酸钾预氧化强化混凝工艺对污水深度处理效果的影响

以某污水厂出水为原水,高铁酸钾Fe(Ⅵ)和氯化铁Fe(Ⅲ)为预氧化剂和混凝剂,考察了NH4+-N、TOC、UV254、相对分子量分布和PO3-4-P参数的变化,分析了高铁酸钾预氧化对污水厂出水深度处理的影响.结果表明,单独铁盐混凝时,混凝剂投量为5 mg·L-1(以铁计),出水的TOC、UV254和PO3-4-P的去除率分别为31%、22%、40%:当投加 1mg·L-1高铁酸钾预氧化剂时,混凝后的出水TOC、UV254和PO3-4-P的去除率分别为39%、37%、47%;随着高铁酸钾投量的增加,去除率也有所增长.同时高铁酸钾预氧化使水中的NH+4-N也有部分升高.溶解态有机物分子质量分布表明,MT小于500的分子所占的百分比跟单独混凝时比较有很大一部分提高,证明高铁酸钾预氧化将原水中的大分子有机物氧化成小分子有机物,与此同时生成部分新生态的水合氧化铁,这些水合氧化铁由于其无定形状态和较小的粒径而具有很强的吸附能力,这就说明在总铁投量一定的情况下,高铁酸钾预氧化比单独混凝时对磷酸根的去除有一定的强化作用.

EFFECT OF FERRATE PREOXIDATION ON COAGULATION OF SECONDARY EFFLUENT FROM WWTP

The preoxidation of secondary effluent from WWTP with ferrate was conducted with respect to its impact on the following coagulation. It can be seen that TOC, UV_(254)-absorbance and phosphate decreased by 31%, 22%, 40% at the dosage of ferric chloride 5 mg·L~(-1), respectively, after coagulation, without ferrate preoxidation, and by 39%, 37%, 47%, respectively, after coagulation, with 1 mg·L~(-1) ferrate preoxidation. The removal rate increased with higher dosage of ferrate. It is also noted that NH_4~+-N concentration is increased after coagulation with ferrate.The results indicated that the concentration of organics with relative molecular mass (Mr) of less than 500 were substantially increased after the secondary effluent was coagulated with ferrate preoxidation, which suggested that some high molecular weight organic substances were broken into smaller ones during ferrate preoxidation, meanwhile, the freshly amorphous hydrated iron oxides were formed, they had much more adsorptive capacity due to theirs small size and amorphous state, therefore they had much affinity for ligand phosphate. It also explain the higher removal rate at the same dosage of total Fe with ferrate.