55 / 2023-05-18 11:04:39

Rice straw addition improves the stability and efficiency of high-solids anaerobic digestion of dewatered sludge via creating balanced function microbial community

dewatered sludge; thermophilic anaerobic digestion; high-solids; microbial community; co-digestion.

Sewage sludge (SS) is the main by-product eluted from wastewater treatment plants (WWTPs). Anaerobic digestion (AD) is widely used to stabilize SS by transforming organic matter into biogas, making SS a potential bioenergy source instead of solid waste requiring disposal. In this study, thermophilic high-solids anaerobic co-digestion of dewatered sludge (DS) and rice straw (RS) was conducted at a constant C/N ratio of 10 (hereafter called C/N ratio-adjusted DS); the long-term reactor performance and microbial community dynamics were compared with DS mono-digestion. The co-digestion allowed stable performance for 952 days, and biogas evolution was 402 ml/g-VTS with methane content of approximate 50% at a higher VTS loading rate of 8.0 g/kg-sludge/d. In contrast, the performance of DS mono-digestion was negatively influenced by the varied properties in DS even at a low VTS loading rate of 1-2 g/kg-sludge/d. Interestingly, the deteriorated DS mono-digestion performance was recovered and promoted by adding RS. Beta-diversity analyses revealed significant differences in the microbial community between co- and mono-digestion. The stable performance of co-digestion was attributed to more balanced function microbes in protein and cellulosic matter degradation, as a result, leading to alleviation of ammonia inhibition.