Coagulation for treatment of paint industry wastewater.
In the present study, the coagulation of paint industry wastewater was examined. Ferrous and aluminum sulphate and polyaluminum chloride (PACl) were used as coagulation agents and the influence of the coagulant dose and effective pH on the quality of treated wastewater was investigated. Optimum pH for FeSO4 addition was near 9.7, the required coagulant dose was about 2 g/L and average process efficiency varied between 30 and 80% in COD and between 70 and 99% in turbidity terms, for a wide spectrum of wastewater batches. In the case of Al2(SO4)3, no pH adjustment was needed and process efficiency varied between 70 and 95% in COD and between 90 and 99% in turbidity terms, for an effective dose of 2.5 g/L. Further improvement of process efficiency was possible by raising the pH of the supernatant liquid after alum-sludge sedimentation to 10. In the case of PACl optimum pH was around 7 and process efficiency was about 98% based on both quality parameters, for an effective dose of 4 g/L. Cationic polyelectrolytes were proved to have a higher potential vs. coagulation than anionic ones when acting as primary coagulants. Combination of Al2(SO4)3 or PACl with polyelectrolytes resulted in high process efficiencies, while maintaining liquid pH values at acceptable limits.
National Technical University of Athens, Department of Chemical Engineering, 9 Heroon Polytechniou Str., GR-15780 Athens, Greece.
Olga
O
Dovletoglou
Constantine
C
Philippopoulos
Helen
H
Grigoropoulou
D000534:Alum Compounds / Q000737:chemistry*; D000536:Aluminum Hydroxide / Q000737:chemistry*; D004563:Electrochemistry; D005296:Ferrous Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D010150:Paint; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D000534:Alum Compounds; D005296:Ferrous Compounds; D007220:Industrial Waste; C016213:aluminum oxychloride; C041524:aluminum sulfate; C020748:ferrous sulfate; D000536:Aluminum Hydroxide