Study Of The Treatment Of High Sulfate Wastewater With EGSB Reactor

Sulfate-containing wastewater has always won the attentions around the world in the field of wastewater treatment because of its difficulty to deal with. The biggest problem is inhibition emerge from sulfide production even being able to lead to the complete failure of the system. As one of the anaerobic reactors belonging to the third generation, the Expanded Granular Sludge Bed (EGSB) reactor is widely used due to its advantages, such as good mass transfer effects, anti-toxicity capacity, etc. So, in this study high sulfate wastewater was treated by the EGSB reactor.Firstly, the reactor was started up without sulfate in the influent. A final organic loading rate (OLR) of 20 kg COD/ (m3·d) could indicate the success of start-up, then the reactor was run smoothly in this state. Following this, a operational parameter, liquid up-flow velocity, was studied and optimized in the above situation and the optimal value of 6 m/h was gained. Secondly, sulfate wastewater was treated in the EGSB reactor in the optimized situation as in the previous chapter. The influent sulfate levels were increased from 676 mg/L to 2700 mg/L step by step. It was observed that inhibition phenomena appeared in 2700 mg/L influent sulfate level, indicating that maximum sulfate reduction ability had been reached. The maximum sulfate reduction ability was 9 kg/(m3·d) under the organic loading rate of 20 kg COD/(m3·d). Also, the above inhibition effect was caused by competition for organic matter between methane producing bacteria (MPB) and sulfate reducing bacteria (SRB), not by sulfide toxicity with a sulfide level of 250 mg/L. At the same time, the lowest COD: SO42- value which could be achieved without the emergence of inhibition was 2.0 or so. Successively, kinetics of sulfate reduction was preliminarily studied and then tested at the end. Finally, molasses wastewater from an alcohol fermentation factory was treated with the same OLR as before. The influent COD removal efficiency of 86% was achieved and the reactor performed stably for continuous fifteen days. However, the color of the wastewater couldn't be degraded at all.