Study and engineering application of an MBR in treating cold-rolled steel wastewater

Abstract

The pickling process in virgin steel manufacturing generates a great deal of oily wastewater in the metals industry. During this process, the coated rolling oil needs to be removed by washing the surface of the steel with acid and alkaline solutions. High chemical oxygen demand (COD), oil, grease, and emulsified oil-in-water pollutants are the key characteristics of the wastewater. Chemical consumption in breaking emulsified wastewater and waste sludge are the main problems in traditional treatment methods. To improve treatment efficiency and reduce chemical usage, a membrane system was applied into the existing wastewater treatment process. The objective of this study is to build an engineering scale membrane bioreactor (MBR) system with a treatment capacity of 1,500 m³/d based on the attained optimum operating parameters in the field study. To assure the success of an actual MBR system being able to be used to treat the oily wastewater, two stages of pilot experiments were conducted. The results showed that the effluent quality of the pilot MBR system for grease concentration, turbidity, and COD were under 10 mg/L, less than 1 NTU, and lower than 100 mg/L, respectively. Based on the results, an actual full size MBR system was constructed and had reduced the costs of chemicals, daily operation, sludge treatment and disposal.

Keywords:

• MBR (membrane bioreactor)
• Cold-rolled steel wastewater
• Oil-in-water