Impact of acid-alkali pretreatment on hydrolysis and acidification of excess sludge
酸-碱处理对剩余污泥水解酸化的影响

Waste activated sludge is rich in recyclable resource such as organic matters and nutrients. After removing and recycling the ammonia nitrogen and phosphorus, the organic acid solution generated in the process of hydrolysis acidification can serve as the carbon source for wastewater treatment. We investigated the effects of three kinds of pretreatment methods (alkali treatment alone, alkali-acid treatment and acid-alkali treatment) on hydrolysis acidification of the waste activated sludge by changing solution pH. The results showed that after alkali treatment, the SCOD dissolving out was 16% higher than that of the combination of alkali and acid treatment,and SCOD reached 5 406.1 mg/L after 8 d. Applying the acid-alkali treatment (pH 4.0 for 4 d first and then pH 10.0 for 4 d), the yield of acetic acid could reach 74.4 mg COD/g VSS, accounting for 60.5% of the total SCFAs, the yield and content of acetic acid in the SCFAs was higher than that of other treatment methods. Moreover, the dissolution of nitrogen and phosphorus was obvious with the acid-alkali treatment. Besides, the most effective method for sludge reduction was the alkali treatment, the removal rate of VSS was 36.6%.