Insight into Effects of Initial Moisture Content on the Heat-Up of Sewage Sludge Composting During Mesophilic Phase

Yuran Su,Yu Li,Chuang Ma,Bin Hu

doi:10.46488/nept.2022.v21i01.045

Abstract

The effects of initial moisture content (55%, 60% and 65%) on the heat-up of sewage sludge (SS) composting during the mesophilic phase were investigated. Monitoring results showed that low moisture content (55%) increased the heating rate, high initial moisture content (60% and 65%) significantly improved the activities of cellulase and peroxidase during the mesophilic phase. Furthermore, although high moisture content improved the diversity of bacteria during composting, there were no significant differences in the microbial structure during the process of succession. So, rather than inhibiting the activity of the bacterial population, the negative effect of high moisture content (60 and 65 per cent) on composting temperature heat up was attributable to the difficulty of heating produced by the specific heat capacity of water. The correlation index between initial moisture content and microorganisms was relatively low, while the temperature was the largest environmental factor affecting the bacterial community. This conclusion provided a hint to make an association between initial moisture content and composting temperature-rising stage.

Highlights

Sewage sludge (SS) is a by-product of municipal wastewater treatment plants, and the production of municipal sewage sludge (SS) is steadily growing as sewage treatment expands (Ma et al 2019)
It is widely anticipated that the initial moisture content (MC) of the compost mixture would be increased as much as possible to improve treatment efficiency and lower the cost of composting operations in composting facilities (Zhou et al 2014, Zhou 2017)
Temperature changes: Initial MC has the greatest impact on temperature, which is widely considered as one of the most important parameters in the composting process (Zhou 2017, Ma et al 2019)

Summary

Introduction

Sewage sludge (SS) is a by-product of municipal wastewater treatment plants, and the production of municipal SS is steadily growing as sewage treatment expands (Ma et al 2019). Microbial DNA was collected from each pile on days 2, 5, and 10 during the mesophilic phase using a FastDNA soil rotation kit (MPBIO, USA) according to the trend of temperature change to determine bacterial diversity during the composting process.

Results

Conclusion