不同pH值下初沉污泥与二沉污泥厌氧发酵对比

Comparative Study on Primary Sludge and Secondary Sludge in Anaerobic Fermentation at Different pH Values

pH值和发酵时间是影响污泥发酵的重要因素。采用序批法分别对初沉污泥和二沉污泥在pH值为5～12时进行发酵，分析了14d内两种污泥的发酵过程。从发酵产物如SCOD、VFAs、蛋白质、碳水化合物的溶出及氮、磷的释放等方面系统地对比了两种不同性质污泥的产物溶出过程及溶出率。结果表明：碱性条件明显有利于SCOD和VFAs的溶出，且SCOD在发酵前期迅速溶出，初沉污泥最佳发酵条件为pH值：9、发酵时间=9．5d，二沉污泥最佳发酵条件为pH值=10、发酵时间=7．5d；初沉污泥能在较短时间内溶出大量VFAs，因此在初沉污泥足量的条件下单独利用初沉污泥发酵是最有效快捷的获取污泥内碳源的方式；稳定后pH值=10时二沉污泥发酵溶出SCOD的量为671．9mgSCOD／gVSS，高于初沉污泥的501．6mgSCOD／gVSS，且氮、磷的释放率也远高于初沉污泥（二沉污泥为52．8mgNH4＋-N／gVSS、13．2mgPO4^3-P／gVSS，初沉污泥为21．8mgNH4＋-N／gVss、3．6mgPO4^3-P／gVSS）。二沉污泥发酵溶出的大量氮、磷会严重加大后续生物处理系统的负荷，因此为减小影响并结合两种污泥各自的发酵特点，建议利用混合污泥发酵来获取内碳源，且较优条件为pH值=10、发酵时间=8d。

pH value and fermentation time are two important faetors in the fermentation process of sludge. Sequeneing batch method was used to examine the fermentation proeesses of primary sludge and seeondary sludge at pH value of 5 to 12 and the fermentation time of 14 days. The dissolution proeesses and the dissolution rates of fermentation products of the two different kinds of sludge were eompared in terms of SCOD, VFAs, protein, carbohydrate, nitrogen and phosphorus. The results showed that alkaline conditions were obviously beneficial to the dissolution of SCOD and VFAs, SCOD dissolved rapidly in the initial stage, and the optimum fermentation conditions of primary sludge were pH of 9 and fermentation time of 9.5 days, while those of secondary sludge were pH value of 10 and the fermentation time of 7.5 days. Primary sludge could produce a large number of VFAs in a relatively short time, therefore, fermentation of sole primary sludge was considered to be the most effective and rapid method to obtain the internal carbon source. Though the amount of SCOD dissolved by secondary sludge （671.9 mgSCOD/gVSS） was much higher than that by primary sludge （501.6 mgSCOD/gVSS） at pH value of 10 after stabiliza- tion, the release rates of nitrogen and phosphorus from secondary sludge （52.8 mgNH4＋ - N/gVSS and 13.2 mgPO4^3- - P/gVSS） were also higher than those from primary sludge （21.8 mgNH4＋ - N/gVSS and 3.6 mgPO3- -P/gVSS）. Besides, a large amount of nitrogen and phosphorus released by secondary sludge seriously aggravated the treatment load of the follow-up system, therefore, in order to ease this impact and combined with the respective fermentation characteristics of the two kinds of sludge, it was suggested that fermentation of mixed sludge was used to obtain the internal carbon sources under the optimum conditions of pH value of 10 and fermentation time of 8 days.