Textile wastewater reuse: Ozonation of membrane concentrated secondary effluent

Among the activities appointed by the EC research-project "Integrated water recycling and emission abatement in the textile industry" (Contract: ENV4- CT95-0064), the effectiveness of ozone for improving the biotreatability of recalcitrant effluents as well as for removing from them toxic and/or inhi bitory pollutants has been evaluated at lab-scale. Real membrane concentrat es (pH=7.9; TOC=190 ppm; COD=595 ppm; BOD5=0 ppm; Conductivity=5,000 mu S/c m; Microtox-EC20=34%) produced at Bulgarograsso (Italy) Wastewater Treatmen t Plant by nanofiltering biologically treated secondary textile effluents, have been treated with ozonated air (O(3)conc.=12 ppm) over 120 min. The re sults have indicated that during ozonation, BOD5 increases from 0 to 75 ppm , whereas COD and TOC both decrease by about 50% and 30% respectively. As f or potentially toxic and/or inhibitory pollutants such as dyes, nonionic su rfactants and halogenated organics, all measured as sum parameters, removal s higher than 90% were achieved as confirmed by the complete disappearance of acute toxicity in the treated streams. The only ozonation byproducts sea rched for and found were aldehydes whose total amount continuously increase d in the first hour from 1.2 up to 11.8 ppm. Among them, formaldehyde, acet aldehyde, glyoxal, propionaldehyde, and butyraldehyde were identified by HP LC. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All r ights reserved.