Adding a recyclable amendment to facilitate sewage sludge biodrying and reduce costs

Abstract

Finding an economical amendment, available in a steady supply, is needed to support the biodrying industrialization. This research developed a recyclable biodrying amendment (RBA) to condition the biodrying of sewage sludge. The pilot-scale treatment (TR), which included the addition of equivalent weights of RBA and sawdust as amendments, resulted in a higher pile temperature and longer thermophilic phase compared to the control (TC), which used only sawdust as an amendment. The final moisture content levels were below 50% with both TR and TC. The heat use efficiency for water evaporation was 72.2% and 73.0% in TR and TC, respectively. The activity of α-amylase and cellulose 1,4-β-cellobiosidase increased during the thermophilic phase, while the activity of endo-1,4-β-glucanase and endo-1,4-β-xylanase decreased during the thermophilic phase with both TR and TC. The fourier-transform infrared spectra indicated that adding the RBA resulted in good biodegradability of the lipids, proteins, and polysaccharides. The humic acid to fulvic acid ratio in TR and TC increased from 0.33 (TR) and 0.35 (TC) on day 0–0.46 (TR) and 0.45 (TC) on day 21, indicating the humification process. The RBA recovery rate was 95.6% and can be reused. These findings highlight that adding RBA showed satisfactory biodrying performance, reduced the amendment cost, and the biodrying product could be incinerated without energy deficit.