Performance Evaluation and Integration of Upflow Anaerobic Sludge Blanket Reactor (UASB) and Aerobic Sequencing Batch Reactor (SBR) for the Treatment of Real Textile Wastewater

Abstract

A hybrid anaerobic-aerobic treatability of real textile wastewater was investigated by using laboratory scale Upflow Anaerobic Sludge Blanket (UASB) coupled with Sequencing Batch Reactor (SBR). The system was fed with real textile wastewater having fluctuating values of chemical oxygen demand (COD), pH, color and alkalinity. During the study, the efficacy of integrated system was determined under various operational conditions. In Phase I of the study, UASB reactor was operated and optimized on real textile wastewater. Anaerobic sludge was acclimatized for a period of 110 days before start of operation. The effect of organic loading rate (OLR), hydraulic retention time (HRT), upflow velocity etc. was investigated to achieve maximum COD and color removal efficiency. The reactor was operated at a hydraulic retention time (HRT) of 48 hours in a semi-continuous mode with 12 hours feeding, 12 hours non-feeding, again 12 hours feeding and 12 hours non-feeding cycle. Volatile fatty acid to alkalinity ratio (VFA/alkalinity) was kept in a range of 0.42 to 0.72 while pH was strictly maintained between 6.8 and 7.2 under mesophilic conditions (35oC). In Phase II of the study, integrated system encompassing UASB and SBR was operated and optimized on real textile wastewater. SBR was operated as a post treatment at HRT of 6 hours with MLSS concentration of 6000 to 7000 mg/L. The integrated system was optimized with 98.3, 93.6, 93.1 and 88.9% as maximum removal efficiencies of COD, color, total kjeldahl nitrogen (TKN) and Ortho-phosphate Phosphorus respectively; at an organic loading rate (OLR) of 0.40 to 1.10 kg COD m3/d. Results inferred that the integrated system is robust and flexible for reclamation of treated wastewater. Furthermore, UASB can be supplemented with biodegradable organic streams like de-sizing wastewater to provide excess carbon source for biogas production.