游离亚硝酸等电点预处理促进初沉污泥固液分离的特性

Efficiency of promoting solid-liquid separation of primary sludge by free nitrous isoelectric point pretreatment

城镇污水厂每天产生大量初沉污泥,初沉污泥成分复杂,无机质含量高,沉降性能不佳。等电点预处理能有效破坏初沉污泥的絮凝状态,游离亚硝酸通过有效破坏细菌结构促进有机物水解,经预处理后的污泥更有利于发酵回收利用和最终的处理处置。研究游离亚硝酸对初沉污泥作等电点预处理的效果,结果表明,在等电点条件下,初沉污泥沉降性能得到改善,CST从203.10 s降低至101.65 s,有机质在固相中得到最大程度保留,上清液中COD从1246.59 mg/L降低至1048.80 mg/L,同时,有效促进污泥中金属污染物溶出,减少了污泥外运处置可能导致的二次污染,但也促进了氮磷类污染物的溶出。投加300 mg/L NO_(2)^(-)-N后进行预处理,初沉污泥SCOD溶出增大,但明显减少了氮磷类污染物的释放,预处理后NH_(4)^(+)-N仅为118.88 mg/L,PO_(4)^(3-)-P为6.91 mg/L。结果表明,NO2--N投加量为300 mg/L、预处理时长取1 h为最佳条件。

WWTPs(Wastewater Treatment Plants)produce a large amount of daily primary sludge.The composition of primary sludge is complex.The inorganic content is high while the settleability is poor.Isoelectric point pretreatment can effectively destroy the flocculation state of the primary sludge.Free nitrous acid can effectively destruct bacterial structure and promote the hydrolysis of organic matter,the pre-treated primary sludge is more conducive to its fermentation,recycling,final treatment and disposal.The effect of isoelectric point pretreatment by free nitrous acid on primary sludge was studied in this study.Experimental results showed that the settling property of primary sludge is improved.The CST reduced from 203.10 s to 101.65 s.Organic matter is retained to the maximum extent in the solid phase.The COD in supernatant decreased from 1246.59 mg/L to 1048.80 mg/L.The metal pollutants in the sludge were released efficiently.The secondary pollution in transport and disposal was prevented and reduced.However,this condition also promoted the dissolution of nitrogen and phosphorus pollutants after 300 mg/L NO_(2)^(-)-N was added for pretreatment,SCOD dissolution increased,but the release of nitrogen and phosphorus pollutants was significantly reduced.After pretreatment,NH_(4)^(+)-N was only 118.88 mg/L and PO_(4)^(3-)-P was 6.91 mg/L.These results showed that the best pretreatment condition for primary sludge is 300 mg/L NO_(2)^(-)-N for 1 h.