Stainless steel cold rolled products surface treatment involves blasting, high temperature alkali leaching, molten salt electrolysis, mixed acid pickling, multistage rinsing combination process, such as multiplex emissions from wastewater including neutral salt, mixed acid wastewater, containing fluorine wastewater, rinse wastewater and flushing water, etc., has a complicated composition, high yield, high acidity and strong toxicity and harm is serious, It has become a difficult point of environmental protection treatment for stainless steel enterprises.

Due to the consideration of mature technology, convenient operation and maintenance, stainless steel enterprises at home and abroad mainly divided multi-channel wastewater into two types: neutral salt wastewater containing Cr6+ and mixed acid wastewater containing other heavy metals. After chemical reduction, most of the neutral salt wastewater is converted into Cr3+ and discharged into the acid-mixing wastewater regulation tank, followed by neutralization precipitation, sludge concentration and plate and frame pressure filtration, and finally the red brown mud cake is obtained.

The practice shows that the quality, quantity and variation trend of cold rolling acid wastewater directly determine the control difficulty of the treatment process, the dosage cost and the output of mixed sludge. In the actual treatment of waste water stations in various enterprises, in order to ensure that the effluent reaches the standard, lime milk is often overadded, resulting in a large number of mud cakes at the end of the process. Taking a stainless steel enterprise with wastewater volume of 100m3/h as an example, the production of mixed sludge exceeds 15,000 tons/year, excluding the operation and maintenance costs of chemicals, energy consumption and manpower.