Optimization of demulsification-coagulation-adsorption parameters for the treatment of wastewater with fluorescent permeating agent from a Chinese machinery plant

摘要

Fluorescent penetrant is used for the cleaning process of precision machine parts in non-destructive testing (NDT). Wastewater will be produced in that course with high chemical oxygen demand (COD) (1000-15,000 mg/L), high mineral oil (300-3000 mg/L) and high chroma (600-2000). This liquid waste has a serious influence on the environment due to its' stronger biological toxicity and higher virulence. When the oil content exceeds 0.01 mg/L in water, the water will lack oxygen and lead aquatic plants and animals to die, thus create badly water pollution. How to treat this polluted water is a difficult task in sewage treatment. The demulsification-coagulation-adsorption process was adapted for conducting this emulsifying wastewater. This research has compared the demulsification effects between the nonionic surfactant demulsifier of AR and the electrolyte demulsifier of CaCl2 and MgCl2 as well as the coagulation performance between the polymeric aluminum chloride (PAC) and the polyaluminium chloride sulfate (PACS). Effects of the types of demulsifier and coagulant, dosage, pH, static duration, absorbing time and other process parameters have been investigated. Based on this, the process parameters have been optimized. The results shown that the best treatment condition was using AR as demulsifier, PACS as flocculant, and vermiculite as adsorbent, which resulted in higher quality and efficiency in removal of 97.87% COD, 99.62% oil and 99.22% colority. This could meet the first grade standard of the national integrated wastewater discharge standard (GB8978-1996). Thus, the integration method of demulsification-coagulation-adsorbtion is a practicable way to solve this kind of sewage.