Technology of complex wastewater treatment for paint and varnish, electroplating plants, enterprises of instrument and mechanical engineering
The technology with three stages of wastewater treatment is presented. At the first stage, with preliminary bubbling with compressed air of sewage with coatings with an intensity of 3-5 dm3/(s • m2) for 20 minutes, the COD is reduced by more than 20%. On the second, when treating the waste water of the combined waste stream containing paint and varnish and chromium using acidic waste solutions containing iron (II) as a reducing agent for 7-10 minutes at pH = 2.5-3.0 COD reduction is achieved not less than 30%. On the third, in the process of neutralizing the total wastewater flow at pH = 8.0-9.0, an oxyhydrate collector (a set of metal hydroxides) is formed, on which paints and varnishes are sorbed and the COD can be reduced after clarification to 30-40 mg O2/dm3. The use of waste process solutions instead of reagents purchased reduced their need by at least 80%.