Treatability of Dye W astewaters by Conventional

ABSTRACT Several studies have reported that the color in dye wastewaters could be removed effectively by a combined biological treatment, ie, anaerobic digestion followed by aerobic degradation. Therefore, the Phoredox or anaerobic/aerobic process, which is a biological phosphorus (BPR) system, seems to be a very good combination for the decolorization of dye wastewater from the textile industry. This study compared the performance of conventional and anoxic+anaerobic/aerobic (A+A/A) sequencing batch reactors (SBRs) in removing organic matter, total kjeldahl nitrogen and color. The two SBR systems with 8 days of sludge age were operated under the same feeding, reacting, settling and withdrawal periods. However, the 10-hour reaction period of the conventional SBR was totally aerobic whereas that of the A+A/A system was separated into 2 hours of anoxic+anaerobic followed by 8 hours of aerobic conditions. The feed wastewaters contained specific target dyes, ie, disperse, sulfur and reactive dyes, which were collected directly from the treatment plants of local textile factories. At the steady state, it was found, as expected, that both systems were able to reduce the chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) of the wastewaters to the same extent. The phosphorus removal efficiency of the A+A/ A system was not so good, approximately only twice as high as that of the conventional system due to limited volatile fatty acids and anaerobic contact time. The visual color removal of the A+A/A syste