Electro-fermentation of iron-enhanced primary sedimentation sludge in a two-chamber bioreactor for product separation and resource recovery

Lin Lin; Long-Hang Tam; Xue Xia; Xiao-Yan Li

doi:10.1016/j.watres.2019.03.075

Electro-fermentation of iron-enhanced primary sedimentation sludge in a two-chamber bioreactor for product separation and resource recovery

Water Res. 2019 Jun 15:157:145-154. doi: 10.1016/j.watres.2019.03.075. Epub 2019 Mar 28.

Authors

Lin Lin¹, Long-Hang Tam², Xue Xia³, Xiao-Yan Li⁴

Affiliations

¹ Environmental Engineering Research Centre, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, China.
² Environmental Engineering Research Centre, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
³ Environmental Engineering Research Centre, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
⁴ Environmental Engineering Research Centre, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, China; Shenzhen Engineering Research Laboratory for Sludge and Food Waste Treatment and Resource Recovery, Graduate School at Shenzhen, Tsinghua University, Shenzhen, China. Electronic address: xlia@hku.hk.

PMID: 30953849
DOI: 10.1016/j.watres.2019.03.075

Abstract

Iron (Fe)-based chemically enhanced primary sedimentation (CEPS) is an effective process used to remove organic and phosphorus (P) pollutants from wastewater into sludge. In this study, electro-fermentation (EF) technology was developed to treat the organic- and P-rich Fe-sludge for the purposes of sludge reduction and resource recovery. Using a two-chamber bioreactor with a cation exchange membrane and an exterior voltage (0.5-1.0 V) for sludge treatment, the EF system enabled product accumulation and separation during the fermentation process. Compared with the conventional fermentation in a single-chamber reactor, the EF treatment of Fe-sludge significantly improved the efficiency of P dissolution from the sludge from 8% to 56% after 4 d. Meanwhile, about 70% of released ammonium ions and 50% of Fe in the sludge were driven by the current from the sludge suspension into the cathode chamber for potential recovery. With a similar yield of volatile fatty acids (VFAs) but less ammonium remaining, the COD_VFA/N_NH4 of the sludge supernatant from the EF reactor could reach 67.7, much higher than that from the single-chamber fermenter at 13.0. The protease activity was effectively promoted by the EF treatment, suggesting that both electrochemical and biological hydrolysis effects contributed to the increased P release from the sludge. Microbial community analysis showed that the electrical stimulation increased the relative abundance of Firmicutes and facilitated the growth of Acidobacteria. Overall, electro-fermentation was developed as an effective biotechnology for processing Fe-based CEPS sludge with the benefits of recovering organics, phosphorus, ammonium and iron resources.

Keywords: Cation migration; Electro-fermentation (EF); Hydrolysis enzymes; Microbial community; Phosphorus dissolution; Resource recovery.

MeSH terms

Bioreactors
Fatty Acids, Volatile
Fermentation
Iron*
Sewage*
Waste Disposal, Fluid

Substances

Fatty Acids, Volatile
Sewage
Iron