Nitrogen Removal from Dye-Industry Wastewater using Pile Fabrics as Biomass Carriers

Abstract

Wastewater from the dye industry contains high level of organic nitrogen derived from urea. Thus, an effective nitrogen removal process is needed to reduce effluent nitrogen concentration. We have developed a new nitrogen removal process using non-woven biomass carriers. In this study, we used pile fabrics, which are products of the local industry in the Wakayama prefecture, instead of non-woven materials as biomass carriers to improve nitrification rates. Several pile fabrics were then used for nitrification and continuous nitrification/denitrification experiments. The specific NOx－N production rate using an acrylic pile fabric was 3.4 times higher than that of non-woven carriers. About 75% nitrification efficiencies were obtained under a T－N loading rate of 0.5 kg－N/m³/day and a HRT of 10 hours during continuous nitrification using acrylic pile fabrics. Furthermore, continuous nitrification/denitrification experiments were carried out using acrylic pile fabrics in a base cloth with a mesh structure to improve the diffusion rates. Little biomass accumulated on the pile fabric surfaces so a high diffusion rate through the pile was maintained for long periods. Denitrification efficiencies of 56 and 77 % were achieved at HRTs of 12 and 19 hours, respectively, with influent concentrations of 200 mg/l T－N and 450 mg/l TOC.