Ozone treatment of textile wastewaters for reuse

Treatment of textile wastewaters by means of an ozonation pilot plant are d escribed. Wastewaters used were produced by a dyeing and finishing factory and were first treated in an active sludge plant and filtrated through sand . In the appropriate conditions very high colour removal (95-99%) was achie ved and the effluent could be reused in production processes requiring wate r of high quality as dyeing yarns or light colorations. Even if the chemica l oxygen demand of treated waters was still in a range (75-120 mg/l, a decr ease of up to 60%) that was usually considered to be too high for recycling purposes, recycling experiments were successful. The economical viability of the techniques implementation was also demonstrated and the industrial p lant is currently under realisation under an EU financed project. The paper considers also the possible improvement of ozone diffusion by mea ns of membrane contactors realised in a second pilot plant, in order to fur ther reduce operating costs of the technique. With respect to traditional s ystems, the gas/liquid contact surface is much higher being that of the mem brane. Ozone at the interface is therefore immediately solubilized and pote ntially consumed with no additional resistance to the mass transfer.