热碱预处理对剩余污泥发酵产酸性能的影响

Effect of thermal alkaline pretreatment on the acids production performance of residual sludge fermentation

预处理技术可以加快污泥水解,提高厌氧发酵的效率.为此,以城市污水处理厂剩余污泥为研究对象,首先探究热碱预处理对剩余污泥破胞效果的影响;其次通过批式实验研究热碱预处理对污泥厌氧发酵产挥发性脂肪酸(Volatile fatty acids,VFAs)的影响;最后,以污泥比阻(Specific resistance to filtration of sludge,SRF)为考察指标,分析评价经发酵后的污泥脱水效果.结果表明,与单独热处理相比,热碱联合预处理能够显著促进污泥破解及有机质溶出,且随着温度与pH的增大,有机物的溶出量与污泥破胞率显著提高.热碱预处理后(120℃,pH=12)污泥破胞率达到54.9%,SCOD、蛋白质、多糖的最大溶出量分别达到了279.16 mg/g MLSS、115.48 mg/g MLSS、20.55 mg/g MLSS.同时,热碱预处理对缩短污泥发酵时间及提高VFAs产量均有显著效果,温度与pH越大,效果越显著.发酵产物中,乙酸为VFAs的主要成分,丙酸次之,在90℃、pH=11预处理条件下乙酸含量为4337 mg COD/L,占总VFAs含量的80%,是厌氧发酵产乙酸的有利条件.预处理污泥厌氧发酵后,SRF分布在(2.1~3.0)×10^(12)m/kg范围内,宜于后续进行机械脱水.

Pretreatment technology can accelerate sludge hydrolysis and improve the efficiency of anaerobic fermentation.In this study,the residual sludge of municipal sewage treatment plant was taken as the object to explore the influence of different thermal alkaline pretreatment conditions on the destruction effect of residual sludge,and the effect of thermal alkaline pretreatment on the production of Volatile fatty acids(VFA) by anaerobic fermentation through batch experiments.In addition,Specific resistance to filtration of Sludge(SRF) was used as an indicator to analyze the dehydration effect of fermented sludge after thermal alkaline pretreatment.The results showed that compared with the single thermal treatment,the thermal alkaline pretreatment could significantly promote sludge cracking and organic matter dissolution,and with the increase of temperature and pH,the yield of dissolved organic matter and the sludge cell destruction rate are significantly increased.After thermal alkaline pretreatment(120 ℃,pH=12),the destruction degress reached 54.9%,and the maximum dissolution amounts of SCOD,protein and polysaccharide reached 279.16 mg/g MLSS、115.48 mg/g MLSS and 20.55 mg/g MLSS,respectively.At the same time,the thermal alkaline pretreatment can shorten the fermentation time of sludge and increase the yield of VFAs.The greater the temperature and pH,the more significant the effect.Among the fermentation products,Acetic acid is the main component of VFAs,followed by propionic acid.The acetic acid content under the pretreatment conditions of 90 ℃ and pH=11 is 4 337 mg COD/L,accounting for 80% of the total VFAs,which is a favorable condition for anaerobic fermentation to produce acetic acid.After pretreatment,the anaerobic digestion SRF was in the range of(2.1~3.0)×10^(12) m/kg,which is suitable for subsequent mechanical dehydration.