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A 20-day sludge biodrying process was coupled with photocatalysis to improve biodrying efficiency and investigate the effect of photocatalysis on biodegradation. After biodrying, the moisture content in the coupled photocatalytic group (T CA) and the control group (T UCA) decreased from 63.61% to 50.82% and 52.94%, respectively, and the volatile solids content decreased from 73.18% to 63.42% and 64.39%, respectively. Neutral proteinase activity decreased by 9.38% and 28.69%, and lipase activity decreased by 6.12% and 26.17%, respectively, indicating that photocatalysis helped maintain neutral proteinase and lipase activities. The Chao1 and Shannon indices showed that photocatalysis increased fungal diversity and reduced bacterial richness and diversity. The β diversity clustering analysis indicated that the bacterial community structure during the thermophilic phase in T CA differed from that in T UCA. The Kyoto Encyclopedia of Genes and Genomes annotation showed that photocatalysis has the potential to promote the synthesis and degradation of ketone bodies. Biodrying coupled with photocatalysis can improve the dewatering of sludge without negatively affecting biodegradation. [Display omitted] • Photocatalysis was applied to sludge biodrying. • The negative effects of TiO 2 addition on biodegradation and microbial communities were not observed. • Coupled photocatalysis helped the maintenance of enzyme activity. • The functional metabolism of microorganisms was analyzed using KEGG. [ABSTRACT FROM AUTHOR]

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 (T R), 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 (T C), which used only sawdust as an amendment. The final moisture content levels were below 50% with both T R and T C. The heat use efficiency for water evaporation was 72.2% and 73.0% in T R and T C , 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 T R and T C. 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 T R and T C increased from 0.33 (T R) and 0.35 (T C) on day 0–0.46 (T R) and 0.45 (T C) 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. Image 1 • The experiment developed a recyclable biodrying amendment to condition the biodrying. • Biodrying did not attenuate the carboxyl and Si–O–Si bonding intensity in the RBA. • Adding the RBA resulted good heating, active enzymes, and satisfactory drying. • Adding the RBA did not weaken lipid, protein, and polysaccharide degradation. • RBA reduced cost and biodrying product could be incinerated without energy deficit. [ABSTRACT FROM AUTHOR]