基于微波预处理的酶强化污泥水解酸化研究

Enhancement of enzymatic hydrolysis acidification for sludge pretreated by microwave-H2O2-alkaline process

微波预处理能显著提高污泥上清液中溶解性有机物含量,进而可作为内碳源补充强化生物脱氮,但释放的大量溶解性有机物却存在碳源可利用性偏低问题.因此,为了提高上述碳源的可利用性,本研究通过批量试验,考察了添加中性蛋白酶和中温α-淀粉酶对微波预处理污泥水解酸化的强化效果,同时研究了水解酸化过程中污泥上清液中有机物的变化特征.结果表明,经过微波-过氧化氢-碱预处理的污泥进行水解酸化能产生较多的挥发性脂肪酸(VFA),碳源可利用性提高,但由于在水解酸化最初的2 d内存在产酸滞后期,导致水解酸化时间被延长.加入中性蛋白酶和中温α-淀粉酶不仅促进了预处理后污泥的水解酸化,而且解除了微波-过氧化氢-碱预处理导致的产酸滞后现象.在55℃、I/S(接种比)=0.07条件下,酶的最佳投加量分别为30 mg·g^(-1)(蛋白酶/总固体浓度TS)和90 mg·g^(-1)(淀粉酶/TS),最佳水解时间为0.5 d,最佳酸化时间为4 d.水解酸化过程中溶解性COD(SCOD)、溶解性蛋白质、溶解性糖类和VFA浓度均呈现先增加后降低的变化规律.水解0.5 d时,30 mg·g^(-1)(蛋白酶/TS)组和90 mg·g^(-1)(淀粉酶/TS)组的SCOD、溶解性蛋白质、溶解性糖类浓度均达到最大值.水解酸化4 d时,30 mg·g^(-1)(蛋白酶/TS)组和90 mg·g^(-1)(淀粉酶/TS)组的总VFA浓度分别为3373.39 mg·L^(-1)(以COD计,下同)和3226.79 mg·L^(-1),比预处理组分别提高了82.37%、74.45%.30 mg·g^(-1)(蛋白酶/TS)组和90 mg·g^(-1)(淀粉酶/TS)组的VFA主要组分均为乙酸、正丁酸和异戊酸,其中,乙酸占总VFA的比例分别为46.53%、45.94%,污泥上清液中的COD/总氮(TN)比分别为13.26、14.41.在碳源组成方面,在水解酸化0.5~4.0 d之内,30 mg·g^(-1)(蛋白酶/TS)组和90 mg·g^(-1)(淀粉酶/TS)组的SCOD浓度基本不变,但随着水解酸化时间的延长,溶解性蛋白质占SCOD的比例均在下降,总VFA占SCOD的比例均在提高,实现了在不改变碳源总量的条件下增加易生物降解有机物比例的目的.

Microwave-based sludge pretreatment can significantly release massive dissolved organic matters（ DOM） into the supernatant which can be served as an internal carbon source for the enhancement of biological nitrogen removal. But low bioavailability of released DOM is a problematic issue.Therefore, for improving bioavailability of DOM from sludge, this study was conducted to investigate effects of neutral protease and α-amylase on the enhancement of sludge hydrolysis acidification, as well as the characteristics of DOM during hydrolysis acidification.The results showed that hydrolysis acidification of sludge pretreated by the microwave-H2O2-alkaline could produce more VFAs and improve the bioavailability of carbon sources, but the time for hydrolysis acidification was prolonged which resulted from an acid production lag during the first 2 d of hydrolysis acidification. Neutral proteaseand α-amylase promoted hydrolysis acidification of pretreated sludge and eliminated the acid production lag caused by the microwave-H2O2-alkaline pretreatment. When the hydrolysis temperature was 55 ℃ and I/ S ratio was 0.07, the optimal enzyme dosage was 30 mg·g-1（protease/ TS） or 90 mg·g-1（amylase/ TS）, the optimal hydrolysis time was 0.5 d and the optimal acidification time was 4 d. During hydrolysis acidification process, concentrations of SCOD, soluble proteins, soluble sugars and total VFAs were firstly increased and then decreased. When the hydrolysis time was 0.5 d and the enzyme dosage was 30 mg·g-1（protease/ TS） or 90 mg·g-1（amylase/ TS）, concentrations of SCOD, soluble proteins, and soluble sugars reached their maximums.When the hydrolysis acidification time was 4 d and the enzyme dosage was 30 mg·g-1（protease/ TS） or 90 mg·g-1（amylase/ TS）, concentration of total VFAs was 3373.39 mg·L-1or 3226.79 mg·L-1（COD based）, and increased by 82.37% or 74.45%, respectively, compared to those of the pretreatment group. Acetic,n-butyric andiso-valeric acids were the main VFAs produced, and the percentage of acetic acid accounting for total VFAs was 46.53% or45.94% and COD/ TN ratio was 13.26 or 14.41 in the sludge supernatant. When the hydrolysis acidification time was from 0.5 d to 4 d and the enzyme dosage was 30 mg·g-1（ protease/ TS） or 90 mg·g-1（ amylase/ TS）, in terms of carbon sources composition, SCOD maintained stable, but with the extension of the hydrolysis acidification time, the proportion of soluble proteins decreased and the proportion of total VFAs increased, indicating that the proportions and readily biodegradable organic matters increased based on the unchanged total amount of carbon sources.