基于有机物释放和经济性的污泥预处理方法评价

Evaluation of Organic Matter Release and Economy for Various Pretreatments of Sewage Sludge

污泥预处理方法包括机械法、化学法和生物法,选择上述方法中具有代表性的超声波20 k Hz、p H 10和厌氧70℃分别预处理污泥,从有机物释放情况和经济性评价不同预处理方法.结果表明,污泥经过预处理后,液相中有机物释放量均增多,但经过p H 10和厌氧70℃预处理后能释放更多的有机物,反应结束时其总溶解性蛋白质和多糖由预处理前的418.9mg·L^-1(以COD计,下同)分别增加到7 516.0 mg·L^-1和7 892.5 mg·L^-1,DNA浓度由预处理前的18.1 mg·L^-1依次增加到1 343.3 mg·L^-1和1 766.1 mg·L^-1;通过流式细胞术鉴定细胞形态得出预处理结束时污泥细胞死亡率从高到低为61.6%(p H10)、59.9%(厌氧70℃)和34.5%(超声波20 k Hz),相比预处理前分别提高45.6%、43.9%和18.5%;预处理结束时污泥有机物去除率依次为19.1%(p H 10)、13.8%(厌氧70℃)和7.6%(超声波20 k Hz);单位体积污泥经p H 10预处理比超声-20kHz和厌氧70℃分别多节约28.5%和124.1%.基于本研究中污泥有机物释放量和经济性,污泥预处理方法宜选择化学法(p H 10).

Mechanical,chemical,and biological methods are always used to pretreat sewage sludge. To determine which pretreatment can release more organic matter from sewage sludge,and therefore,make it more economical,mechanical pretreatment( ultrasonic treatment at 20 k Hz),chemical pretreatment( p H 10),and biological pretreatment( anaerobic conditions at 70℃) were compared.Results showed that all three pretreatments increased the organic matter release of sewage sludge;the initial total soluble protein and carbohydrate concentration of which was only 418. 9 mg·L^-1( cal. as COD) and the DNA content was 18. 1 mg·L^-1. However,the p H 10 and anaerobic( 70℃) pretreatments resulted in a greater organic release than the ultrasonic( 20 k Hz) pretreatment,with total soluble protein and carbohydrate concentrations of 7 516. 0 mg·L^-1 and 7 892. 5 mg·L^-1,and DNA contents of 1 343. 3 mg·L^-1 and1 766. 1 mg·L^-1,respectively. Flow cytometry was adopted to assess cell morphology. The cell mortality rates of sludge after pretreatment accounted for 61. 6%,59. 9%,and 34. 5% respectively,which was improved by 45. 6%( at p H 10),43. 9%( under anaerobic conditions at 70℃),and 18. 5%( with ultrasonic pretreatment at 20 k Hz) compared with raw sewage sludge. At the same time,organic matter removal ratios of sludge after pretreatment were 19. 1%( at p H 10),13. 8%( under anaerobic conditions at70℃),and 7. 6%( with ultrasonic pretreatment at 20 k Hz). Moreover,the pretreatment of per liter sludge at p H 10 saved 28. 5%and 124. 1% more than ultrasonic pretreatment( 20 k Hz) and anaerobic( 70℃) pretreatment. Taking both organic matter release and economic analysis into consideration,the chemical method of pretreatment( at p H 10) was identified as the best option.