Persulfate and zero valent iron combined conditioning as a sustainable technique for enhancing dewaterability of aerobically digested sludge

Abstract

Aerobic digestion followed by dewatering is a widely applied method for sludge stabilization and reduction in decentralized wastewater treatment plants. It is important to enhance the sludge dewaterability of the aerobically digested sludge due to its considerable impact on cost of sludge disposal and management. In this study, an innovative technique is developed for improving the dewaterability of aerobically digested sludge by combined conditioning with persulfate (PS) and zero valent iron (ZVI). The results demonstrated that the dewaterability of aerobically digested sludge could be significantly enhanced with the PS and ZVI dosage in the range of 0 to 0.5 g/gTS and 0 to 0.4 g/gTS, respectively. The highest improvement was achieved at 0.05 g ZVI/g TS with 0.1 g PS/g TS, and the capillary suction time was reduced by ~80%.The extracellular polymeric substances (EPS) characterization revealed that the combined PS-ZVI treatment could largely reduce proteins, polysaccharides and humic acids-like compounds in the tightly bounded EPS of the aerobically digested sludge, leading to bound water releasing from sludge flocs. The recovery of the ZVI particles could reach around 45% -80% after the treatment, further proved the sustainability of the approach. The proposed PS-ZVI conditioning would not have significant impact on the final choice of sludge disposal and the mainstream wastewater treatment. However, plant-scale test are still required for better assessing the proposed technique.

The extent of reaction traced by determination of N2 content for synthesised cationic biodegradable polymer flocculant

“…Biodegradable "green" and safe substitutes to minimize environmental and health risks are drawing extensive attention for research interest. [1][2][3] This research work is experimental to develop a biodegradable starch-grafted polymer flocculant to treat industrial wastewater and make our environment clean and healthy. A grafted starchbased biodegradable polymer is developed to gain both the advantage of natural and synthetic polymers.…”

Adaptability of organic matter and solid content to Fe2+/persulfate and skeleton builder conditioner for waste activated sludge dewatering

“…Low SC means more water content, resulting in the agent concentration being "diluted", thereby reducing the effectiveness of conditioning. If the Fe 2+ :SPS molar ratio is too small, so that the Fe 2+ dosage is insufficient, the effective decomposition of SPS is limited as is the production of SO4• -, weakening the intensity of oxidation of the sludges (Luo et al 2018, Ni et al 2019.…”

“…Commonly used sludge conditioning methods are physical conditioning (Carrasco and Gao 2019, Mobaraki et al 2018, Ramachandra and Devatha 2020, chemical conditioning (Ge et al 2019, Hu et al 2020, Wang et al 2018) and biological conditioning (Chen et al 2015, Huo et al 2014, Liu et al 2016a). Advanced oxidation technology has become a subject of research interest in the area of chemical conditioning due to the advantages of low secondary pollution and fast reaction times (Bian et al 2021, Chen et al 2021, Chen et al 2020, Kim et al 2016, Ni et al 2019, Wei et al 2020, Zhang et al 2020b. Our previous research used Fe 2+ activated sodium persulfate (SPS) combined with phosphogypsum (PG) for sludge conditioning and found both oxidation and skeleton building effects (Shi et al 2015).…”

Combination of electrochemical and Fe2+ -activated persulfate oxidation for improving the dewaterability of aerobically digested sludge

“…It has been estimated that sludge treatment and disposal accounts for approximately 50-60% of the costs of treatment plants (Gurjar & Tyagi, 2017). Aerobic digestion is a frequently employed technique for sludge treatment in small-scale wastewater treatment plants (WWTPs) (Ni et al, 2019;Wang & Yuan, 2015).…”