Biodegradability enhancement of waste lubricating oil regeneration wastewater using electrocoagulation pretreatment

• Published in: Environmental science and pollution research international 2023-10, Vol.30 (48), p.106421-106430
• Main Authors: Shan, Li-li, Tan, Zhao, Chen, Yu, Wang, Ruo-shan, Zhang, Meng, Pang, Chang-long, Cui, Yu-Hong, Liao, Zhi-min, Ma, Hong-qiang, Zhu, Ze-bing
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Biochemical oxygen demand; Biodegradability; Biodegradation; Biological Oxygen Demand Analysis; Biological treatment; Chemical oxygen demand; Current density; Earth and Environmental Science; Ecotoxicology; Electrocoagulation; Electrocoagulation - methods; Electrodes; Electrolysis; Environment; Environmental Chemistry; Environmental Health; Environmental protection; Flocculation; Flotation; Fossil fuels; Gas chromatography; Industrial Waste - analysis; Lubricating oils; Mass spectrometry; Mass spectroscopy; Neutralization; Oil removal; Oil wastes; Oils; Organic compounds; Pretreatment; Recycling; Regeneration; Research Article; Sustainability management; Waste Disposal, Fluid - methods; Waste Water Technology; Wastewater; Water Management; Water Pollutants, Chemical - analysis; Water Pollution Control
• ISSN: 1614-7499; 0944-1344; 1614-7499
• DOI: 10.1007/s11356-023-29841-7

As a sustainable management of fossil fuel resources and ecological environment protection, recycling used lubricating oil has received widespread attention. However, large amounts of waste lubricating-oil regeneration wastewater (WLORW) are inevitably produced in the recycling process, and challenges are faced by traditional biological treatment of WLORW. Thus, this study investigated the effectiveness of electrocoagulation (EC) as pretreatment and its removal mechanism. The electrolysis parameters (current density, initial pH, and inter-electrode distance) were considered, and maximal 60.06% of oil removal was achieved at a current density of 15 mA/cm 2 , initial pH of 7, and an inter-electrode distance of 2 cm. The dispersed oil of WLORW was relatively easily removed, and most of the oil removal was contributed by emulsified oil within 5–10 μm. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that effective removal of the biorefractory organic compounds could contribute to the improvement of biodegradability of WLORW. Thus, the 5-day biochemical oxygen demand/chemical oxygen demand ratio (BOD 5 /COD) was significantly enhanced by 4.31 times, which highly benefits future biological treatment. The routes of WLORW removal could be concluded as charge neutralization, adsorption bridging, sweep flocculation, and air flotation. The results demonstrate that EC has potential as an effective pretreatment technology for WLORW biological treatment.