Ball-milled magnetic sludge biochar enables fast aerobic granulation in anoxic/oxic process for the treatment of coal chemical wastewater

Dan Li; Su Yan; Xiaoyu Yong; Xueying Zhang; Jun Zhou

doi:10.1016/j.scitotenv.2023.163241

Ball-milled magnetic sludge biochar enables fast aerobic granulation in anoxic/oxic process for the treatment of coal chemical wastewater

Sci Total Environ. 2023 Jul 1:880:163241. doi: 10.1016/j.scitotenv.2023.163241. Epub 2023 Apr 1.

Authors

Dan Li¹, Su Yan¹, Xiaoyu Yong², Xueying Zhang³, Jun Zhou⁴

Affiliations

¹ College of Environmental Science and Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China; Bioenergy Research Institute, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China.
² Bioenergy Research Institute, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China.
³ College of Environmental Science and Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China. Electronic address: xueyingzhang@njtech.edu.cn.
⁴ College of Environmental Science and Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China; Bioenergy Research Institute, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, Jiangsu 211816, China. Electronic address: zhoujun@njtech.edu.cn.

PMID: 37011673
DOI: 10.1016/j.scitotenv.2023.163241

Abstract

Coal chemical wastewater (CCW) containing toxic and hazardous matters requires to be treated prior to discharge. Promoting the in-situ formation of magnetic aerobic granular sludge (mAGS) in continuous flow reactor process has a great potential for CCW remediation. However, long granulation time and low stability limit the application of AGS technology. In this study, Fe₃O₄/sludge biochar (Fe₃O₄/SC) with biochar matrix derived from coal chemical sludge were applied to facilitate the aerobic granulation in two-stage continuous flow reactors, containing separated anoxic and oxic reaction units (abbreviated as A/O process). The performance of A/O process was evaluated at various hydraulic retention times (HRTs) (42 h, 27 h, and 15 h). Magnetic Fe₃O₄/SC with porous structures, high specific surface area (BET = 96.69 m²/g), and abundant functional groups was successfully prepared by ball-milled method. Adding magnetic Fe₃O₄/SC to A/O process could promote aerobic granulation (85 days) and the removal of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N)_, and total nitrogen (TN) from CCW at all tested HRTs. Since the formed mAGS had high biomass, good settling ability, and high electrochemical activities, mAGS-based A/O process had high tolerance to the decrease of HRT from 42 h to 15 h for CCW treatment. The optimized HRT for A/O process was 27 h, at which Fe₃O₄/SC addition can result in the increase of COD, NH₄⁺-N and TN removal efficiencies by 2.5 %, 4.7 % and 10.5 %, respectively. Based on 16S rRNA genes sequencing, the relative abundances of genus Nitrosomonas, Hyphomicrobium/Hydrogenophaga and Gaiella in mAGS accounting for nitrification, denitrification as well as COD removal were increased during aerobic granulation. Overall, this study proved that adding Fe₃O₄/SC to A/O process was effective for facilitating aerobic granulation and CCW treatment.

Keywords: Aerobic granulation; Bacterial community; Coal chemical wastewater; Magnetic sludge biochar; Wastewater treatment.

MeSH terms

Bioreactors
Coal
Magnetic Phenomena
Nitrogen
RNA, Ribosomal, 16S
Sewage* / chemistry
Waste Disposal, Fluid / methods
Wastewater*

Substances

Wastewater
Sewage
biochar
Coal
RNA, Ribosomal, 16S
Nitrogen