The effect of biosurfactant rhamnolipid (RL) on hydrolysis and acidification of waste activated sludge (WAS) was investigated. The results indicated that RL could greatly reduce the surface tension of sludge, resulting in stimulating the hydrolysis rate of WAS and enhancing the production of short-chain fatty acids (SCFAs). With the increase of RL dosage from 0.2 to 0.5 g/g DS, the maximum soluble chemical oxygen demand (SCOD), protein and carbohydrate concentration increased correspondingly. After 6 h of hydrolysis, SCOD, protein and carbohydrate concentration increased from 371.9, 93.3 and 9.0 mg/l to 3,994.5, 800.0 and 401.4 mg/l at RL 0.3 g/g DS, respectively. Furthermore, the release of NH4 (+)-N, PO4 (3-)-P and the accumulation of SCFAs also improved in the presence of RL. The maximum SCFAs was 1,829.9 mg COD/l at RL 0.3 g/g DS, while it was only 377.7 mg COD/l for the blank test. The propionic acid and acetic acid were the mainly SCFAs produced, accounting for 50-60% of total SCFAs.

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This paper targets at understanding the causal effects of maternal marital instability on children’s marriage dissolutions through exploring a natural experiment and implementing IV approach, the forced rustication during 1968-1978 in China. With the 2008 and 2010 waves of Chinese Family Panel Survey, significant estimates imply that in urban China, one extra year of forced immigration has increased mother’s marital instability by 1.5%, further contributed to doubling the risk of her children to encounter marital instability. Contemporary comparisons show that, on average, the sent-down parents experienced more marital instability by 2%; married two years later; married older spouses; value relatively less in spousal intimacy. The latter two are proved to be significant mediators.