[Effect of initial pH on bioacidification treatment of woolscouring effluent]

To remove biorefractory organic matter from woolscouring effluent, the bioacidification treatments pre-acidified by 4.5 mo x L(-1) sulfuric acid and bioacidified wastewater were performed through a 10 L stirred tank reactor. Hydraulic retention time (HRT) for the treatment was obviously shortened through pre-acidification of woolscouring effluent. Bioacidification treatment efficiency facilitated by pre-acidification with bioacidified wastewater was much higher than that by pre-acidification with sulfuric acid. When initial pH was adjusted to 5.20 with bioacidified wastewater, the bioacidification treatment resulted in more than 91% COD removal and 1.5 days of HRT, which was 7.5 days shorter than that of treatment without pre-acidification. It was found that pre-acidification with bioacidified wastewater played an important role in providing a more satisfactory environment for Acidithiobacillus thiooxidans growth, eliminating the buffer capacity of woolscouring effluent, and also inoculating more A. thiooxidans in the reactor. Therefore, the bioacidification treatment of woolscouring effluent through the recycling of a part of bioacidified wastewater for pre-acidification can be operated steadily and continuously, which exhibits a good prospect for engineering application.