Mumbai university > Civil > SEM 8 > Industrial Waste Treatment

Marks: 5M

Year: Dec 2015 ,

Following are the available technology for colour removal:

• Adsorption system: Resin separation, Ion-exchange, Activated alumina, activated carbon.

• Precipitation system: Coagulation with trivalent metal salts, lime, poly-electrolytes.

• Oxidation system: Ozone, chlorine, H2O2, UV-radiation

• Membrane system: Reverse osmosis, ultra filtration.

Oxidation system:

• Many dyes containing waste water are effectively decolorized using chemical oxidizing agents like chlorine.

• The chlorine level of about 150 mg/l in treating textile dying results in 77% of colour removal but chlorine residual 110 mg/l of chlorine applied remained in treated waste water.

• When dose was below 110 mg/l no residue was detected but 75% of colour was removed.

• Use of Cl2 is not desirable since chlorinated organic compounds that are generated in the process are highly objectionable as they are potential carcinogens.

• Ozone is a powerful oxidant and is reported to be effective in decolouring waste water containing reactive and basic dyes but ineffective in disperse dyes using about 1 g/l ozone.

• However, Ozone treatment produces little reduction in TOC or DOC cost and effectively are often barrier associated with ozone.

Reduction system:

• Chemical reduction of ozone dyes converts them to aromatic amines.

• The most commonly used chemical reducing agent is sodium hydrosulphide, sodium formaldehyde, sulfoxylateetc are additional reducing agents for treating dye and waste water.

• The chemical treatment with reducing agents is effective in decolourizing but the resulting effluent is reported to be inhibitory or toxic to subsequent aerobic biological treatment.