Vacuum evaporation and reverse osmosis treatment of process wastewaters containing surfactant material: COD reduction and water reuse

The problem of process wastewater arises not only in fine chemical industry, but also where water is used for washing. In these cases, surfactant material is given to the water, so its washing capability is enhanced. The used water contains surfactant material and dirt. It has high chemical oxygen demand (COD) resulting in serious environmental problems. Finding a solution is inevitable because of the high wastewater fine which has to be paid by the factories if wastewater is emitted without any treatment. A suitable method had to be found that follows the principles of circular economy, so the industrial cycles can be closed like in nature and the water can be reused. Our designed method focuses on different kinds of wastewater containing special surfactant materials, and it has chemical industry relations. The treatment should have reduced the high COD value below to 1000 mgO2/L, which is the discharge limit. It was also aimed that instead of discharging, the treated water could be recycled and reused. Our new physicochemical treatment process consists of a vacuum evaporation method that reduces COD from c.a. 8400 to 1100 mgO2/L. Both laboratory and pilot experiments were investigated. Since this COD value was not satisfactory, a subsequent reverse osmosis membrane operation was also applied. This two-step method, vacuum evaporator followed by reverse osmosis, was able to reduce the COD in wastewater containing surfactant/washing material below the discharge limit. 100 mgO2/L could be reached with using TriSep™ X201 membrane. Penalty calculation and cost estimation also demonstrate the efficiency of our novel method.