Treatment of Fluorescent Wastewater Using Chemical Demulsification Techniques

Abstract

The aerospace magnesium alloy castings manufacturing companies use tracer flaw inspection for castings, which generates fluorescent wastewater. This wastewater consists of mineral oil, surfactants, fluorescent agents, and many organic substances. Its composition is complex and difficult to treat. In this paper, the feasibility of treating fluorescent wastewater with high chemical oxygen demand (COD) concentration based on the chemical demulsification method was investigated. Single-factor experiments were conducted with selected demulsifier types, demulsifier dosage and pH to investigate the effects of each factor on the treatment effect; and through orthogonal experiments, the best demulsifier was found to be PR-2 demulsifier, with pH=7 and demulsifier dosage of 3 g/L. Single-factor experiments were conducted with stirring speed, stirring time and settling time to optimize the reaction conditions for the demulsification method. The best conditions for demulsification were then obtained through orthogonal experiments: stirring at 100 r/min for 30 min and settling for 30 min. Under the aforementioned conditions, it was observed that the wastewater COD concentration decreased from 2 406.0 mg/L to 233.8 mg/L, and the COD removal rate reached 90.26%. The water quality of the treated wastewater was found to meet the tertiary standard of the Comprehensive Sewage Discharge Standard (GB 8978-1996).

Keywords

• fluorescent wastewater|chemical demulsification|orthogonal experiment