The conventional treatment technology employing surface aeration or dissolved aeration system for the treatment of wastewater require huge electrical power and vast land. The new technology known as Chemo Autotrophic Activated Carbon Oxidation system (CAACO) developed by Central Leather Research Institute has both biological and chemical oxidation system integrated in a single reactor. CAACO reactor employs rice bran based activated carbon as the matrix for immobilisation of organisms to fragment the heavier organics in wastewater and for oxidation of lower organics into stable end products. The oxygen required for the oxidation of organics is supplied in the form of air at ambient temperature and at low pressure. The wastewater discharged during the processing of skins/hides into wet blue leather (Raw to wet blue process) is characterised by COD 2600 mg/l, BOD 1650 mg/l, Dissolved Protein 965 mg/ l, sulphide 235 mg/l, sulphate 462 mg/l and Total Dissolved Solids 9742 mg/l. The wastewater was Coagulated―Flocculated to characterise COD 947 mg/l, BOD 620 mg/l, sulphide 135 mg/l and protein 524 mg/l. The primary treated wastewater was applied to CAACO reactor at an surface loading rate of 6.0 x 10~(-3) mVm~2/min and at hydraulic retention time 2 hours. The wastewater was of chracteristics COD 198 mg/l, BOD 148 mg/l and dissolved protein 56mg/l. Second stage CAACO treatment lowered the COD to 152 mg/l and BOD to 25 mg/l at Hydraulic detention time 1 hour. The rate constant for the removal of sulphide and dissolved protein was determined by concentration of sulphide in wastewater, space time application and temperature. It was observed that the rate of removal was increased with increase in temperature.
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