An advanced anaerobic expanded granular sludge bed (AnaEG) for the treatment of coal gasification wastewater

Abstract

A state-of-the-art advanced anaerobic expanded granular sludge bed (AnaEG) was developed for the anaerobic treatment of coal gasification wastewater (typical industrial wastewater with poor biodegradability and high toxicity). Three batch tests were conducted to check the efficiency of the reactor. The reactor was run for 330 days using acidification, with a final hydraulic retention time (HRT) of 48 hours. With an influent concentration of chemical oxygen demand (COD) of 1400 mg L⁻¹, 320 mg L⁻¹ total phenol , and 150 mg L⁻¹ volatile phenol, the effluent COD, total phenol, and volatile phenol could be decreased to 800 mg L⁻¹, 200 mg L⁻¹ and 40 mg L⁻¹, respectively. The AnaEG shows a COD removal efficiency of 50%, with a loading rate of 0.806 (kg COD per m³ per day), a removal rate of 0.357 (g COD per day), total phenol removal efficiency of 50%, and a volatile phenol removal efficiency of 80%. Besides being able to remove 70–95% of organic matter from the wastewater, this technology generates less sludge. Finally, scanning electron microscopy (SEM) revealed long-chain filamentous bacteria; coccus and rod-shaped bacteria were the dominant microorganisms. A CH₄ production rate of 227.23 (ml CH₄ per L per day) during a loading rate of 626.25 (mg COD per L per day) and a removal rate of 87.68 (mg COD per L per day) was observed. The significant reduction in the amount of sludge produced therefore reduces the sludge management cost. It does not have to reflux; this equipment is simple as it requires less accessory equipment and lower power consumption, and produces a high quality effluent. All the results demonstrate that the AnaEG could be used efficiently for the treatment of coal gasification wastewater containing high COD and phenol concentration.