Performance evaluation of anaerobic moving bed bioreactor (An-MBBR) for pretreatment of desizing wastewater

Only a few textile mills in Pakistan have installed wastewater treatment plants, and even if installed, aerobic treatment processes are hardly operational due to high energy requirements. The performance of a pilot-scale anaerobic moving bed bioreactor was thus investigated in terms of organic removal and biogas production as a potentially energy-efficient pretreatment of real textile desizing wastewater. The pilot plant was operated under on-site conditions for 122 d at Kohinoor Mills Limited Kasur, Pakistan. The temperature of the bioreactor was in the mesophilic range of 22°C–36°C, while pH and oxidation-reduction potential were in the range of 7.7–8.0, and –580–630 mV, respectively. The volumetric organic loading rate of the bioreactor varied 0.2–2.0 kgCOD/m3/d. Almost 50% of chemical oxygen demand (COD) removal was achieved and COD conversion into biogas was 0.35 m3biogas/kgCODremoved. The produced biogas had a high methane content with a specific methane production of 0.26 m3methane/kgCODremoved. The overall performance of bioreactor was marginally improved when the system was running with low sulfate enzymatic desizing wastewater instead of oxidative peroxydisulfate-treated desizing wastewater. After further optimization overcoming unsatisfying biomass retention, high H2S formation, and possible inhibitory effects of detergents used in the desizing process, this technology has the potential for widespread application in the textile sector of semi-arid developing countries.