In-situ sludge reduction performance and mechanism in an anoxic/aerobic process coupled with alternating aerobic/anaerobic side-stream reactor

Cheng Cheng; Jinju Geng; Haidong Hu; Yihan Shi; Rongwei Gao; Xu Wang; Hongqiang Ren

doi:10.1016/j.scitotenv.2021.145856

In-situ sludge reduction performance and mechanism in an anoxic/aerobic process coupled with alternating aerobic/anaerobic side-stream reactor

Sci Total Environ. 2021 Jul 10:777:145856. doi: 10.1016/j.scitotenv.2021.145856. Epub 2021 Feb 15.

Authors

Cheng Cheng¹, Jinju Geng², Haidong Hu¹, Yihan Shi¹, Rongwei Gao¹, Xu Wang¹, Hongqiang Ren³

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, Jiangsu, PR China.
² State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, Jiangsu, PR China; Yixing Environmental Protection Research Institute, Nanjing University, Nanjing 214200, Jiangsu, China.
³ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, Jiangsu, PR China; Yixing Environmental Protection Research Institute, Nanjing University, Nanjing 214200, Jiangsu, China. Electronic address: hqren@nju.edu.cn.

PMID: 33677286
DOI: 10.1016/j.scitotenv.2021.145856

Abstract

Activated sludge process with anaerobic side-stream reactors (SR) in the sludge recirculation can achieve in-situ sludge reduction, but sludge reduction efficiency is limited with the low hydraulic retention time (HRT) of SR. An anoxic/aerobic (AO) process, AO coupled with anaerobic SR and AO coupled with alternating aerobic/anaerobic side-stream reactor (AO-OASR) were operated to investigate enhancing effects of alternative aerobic and anaerobic condition (AltOA) in SR on sludge reduction and pollutants removal performance. The AltOA was firstly proposed into SR with a low HRT during the long-term continuous operation. The results showed that AO-OASR presented a lower effluent COD concentration (29.6%) with no adverse effect on nitrogen removal, compared to AO, owing to the intensified refractory carbon reuse in the mainstream aerobic tank. The sludge yield in AO-OASR (0.240 g SS/g COD) was 39.7% lower than that in AO. The OASR accelerated sludge lysis and particle organic matter hydrolysis due to the weakened network strength of flocs, leading to an enhanced increase (17.3 mg/L) of dissolved organic matter (DOM), especially for the fraction of molecular weight (MW) < 25 kDa. The OASR reduced the adenosine triphosphate (ATP) content for heterotrophic anabolism in the mainstream reactor by 42.9%, compared to the ASR. MW < 25 kDa of DOM caused the disturbance of oxidative phosphorylation with a decreasing ATP synthase activity under high-level electronic transport system, leading to ATP dissipation. The cooperation interaction of predator (norank_Chitinophagales), hydrolytic/fermentative bacteria (unclassified_Bacteroidia and Delftia), and slow grower (Trichococcus) played a key role in improving the sludge reduction and carbon reuse in AO-OASR. The results provided an efficient and cost-saving technology for sludge reduction with modified SR under low HRT, which is meaningful to overcome the present bottleneck of deficient reduction efficiency for application in wastewater treatment plants.

Keywords: Activated sludge; Alternating aerobic/anaerobic side-stream reactor; Microbial community; Molecular weight; in-situ sludge reduction.

MeSH terms

Anaerobiosis
Bioreactors
Nitrogen
Sewage*
Waste Disposal, Fluid*

Substances

Sewage
Nitrogen