Shen Dong-Sheng, He Ruo, Liu Xin-Wen, Long Yan
Department of Environmental engineering, Zhejiang University, 268 Kaixuan Road, HangZhou 310029, PR China.
J Hazard Mater. 2006 Aug 25;136(3):645-53. doi: 10.1016/j.jhazmat.2005.12.050. Epub 2006 Feb 28.
Upflow anaerobic sludge blanket (UASB) reactor that was seeded with anaerobic sludge acclimated to chlorophenols was used to investigate the feasibility of anaerobic biotreatment of synthetic wastewater containing pentachlorophenol (PCP) with additional sucrose as carbon source. Two sets of UASB reactors were operated at one time. But the seeded sludge for the two reactors was different and Reactor I was seeded with the sludge that was acclimated to PCP completely for half a year, and Reactor II was seeded with the mixed sludge that was acclimated for half a year to PCP, 4-CP, 3-CP or 2-CP, respectively. The degradation of PCP and the operation fee treating the wastewater are affected by the concentration of MEDS (microorganism easily degradable substrate). So the confirmation of the suitable ratio of [COD] and [PCP] was the key factor of treating the wastewater containing PCP economically and efficiently. During the experiment, the synthetic wastewater with 180.0 mg L(-1) PCP and 1250-10000 mg L(-1) COD could be treated steadily in the experimental Reactor I. The removal efficiency of PCP was more than 99.5% and the removal efficiency of COD was up to 90%. [PCP] (concentration of PCP) in effluent was less than 0.5 mg L(-1). [PCP] in influent could affect proper [COD] (concentration of COD) range in influent that was required for maintenance of steady running of the experimental reactor with a hydraulic retention time (HRT) from 20 to 22 h. [PCP] in influent would directly affect the necessary [COD] in influent when the UASB reactor ran normally and treated the wastewater containing PCP. When [PCP] was 100.4, 151.6 and 180.8 mg L(-1) in influent, respectively, [COD] in influent had to be controlled about 1250-7500, 2500-5000 and 5000 mg L(-1) to maintain the UASB reactor steady running normally and contemporarily ensure that [COD] and [PCP] in effluent were less than 300 and 0.5 mg L(-1), respectively. With the increase of [PCP] in influent, the range of variation of [COD] in influent endured by the UASB reactor was decreasing. The ratios of [COD] and [PCP] in influent could affect removal efficiency of PCP and COD, the concentration of total volatile fatty acids (VFA) in effluent, biogas quantity and methane content in biogas. [PCP] in influent was linearly or semi-logarithmically correlated to [COD] in effluent when [COD] in influent was 5750+/-250 mg L(-1), and so was the relationship between [COD] in influent and [PCP] in effluent when [PCP] in influent was 100.4 or 151.6 mg L(-1), less than the maximum permissible [PCP]. The sources of seeded sludge, the way of sludge acclimation and the characteristics of anaerobic sludge could all affect the UASB reactor capacity treating PCP. When [PCP] were less than 180.8 mg L(-1) for Reactor I and 151.6 mg L(-1) for Reactor II, the variation of [PCP] in influent had little effect on the UASB reactor volume gas production rate and substrate gas production rate. And [VFA] and pH value in effluent were affected a little. Volume biogas production rate and substrate biogas production rate of the UASB reactor were only affected by [COD] and loading rate in influent. But when [PCP] was more than 151.6 mg L(-1) for Reactor II, the biogas production fell quickly and was over 3 days later. [VFA] in effluent from Reactor II increased up to 2198.1 mg L(-1) quickly and the pH value fell to less than 7. Reactor II could not run normally. The component of VFA accumulated quickly was mainly acetate (above 50%). With [PCP] increased from 7.9 to 180.8 mg L(-1) gradually in influent, the methane content in biogas from Reactor II decreased from 70% to 60%, but the reactor could still run normally. Then as for Reactor II, the content of methane have fallen from 75% to 45% or so quickly. And Reactor II could not run steadily. So the conclusion could be drown that too high [PCP] in influent for UASB reactor mainly inhibited the activity of methane-producing bacteria cultures utilizing the acetate.
以适应氯酚的厌氧污泥接种的上流式厌氧污泥床（UASB）反应器，用于研究以蔗糖为额外碳源对含五氯苯酚（PCP）的合成废水进行厌氧生物处理的可行性。同时运行两组UASB反应器。但两个反应器接种的污泥不同，反应器I接种的是已完全适应PCP半年的污泥，反应器II接种的是分别适应PCP、4-氯酚、3-氯酚或2-氯酚半年的混合污泥。PCP的降解以及废水处理运行费用受易降解微生物底物（MEDS）浓度影响。因此，确定合适的[COD]与[PCP]比例是经济高效处理含PCP废水的关键因素。实验期间，实验反应器I中可稳定处理含180.0 mg L⁻¹ PCP和1250 - 10000 mg L⁻¹ COD的合成废水。PCP去除率大于99.5%，COD去除率高达90%。出水[PCP]（PCP浓度）小于0.5 mg L⁻¹。进水[PCP]会影响维持实验反应器稳定运行所需进水[COD]（COD浓度）范围，水力停留时间（HRT）为20至22 h。当UASB反应器正常运行处理含PCP废水时，进水[PCP]会直接影响进水所需的[COD]。当进水[PCP]分别为100.4、151.6和180.8 mg L⁻¹时，进水[COD]必须控制在约1250 - 7500、2500 - 5000和5000 mg L⁻¹，以维持UASB反应器正常稳定运行，同时确保出水[COD]和[PCP]分别小于300和0.5 mg L⁻¹。随着进水[PCP]增加，UASB反应器能承受的进水[COD]变化范围减小。进水[COD]与[PCP]比例会影响PCP和COD去除率、出水总挥发性脂肪酸（VFA）浓度、沼气量及沼气中甲烷含量。当进水[COD]为5750±250 mg L⁻¹时，进水[PCP]与出水[COD]呈线性或半对数相关，当进水[PCP]为100.4或151.6 mg L⁻¹（小于最大允许[PCP]）时，进水[COD]与出水[PCP]关系也是如此。接种污泥来源、污泥驯化方式及厌氧污泥特性均会影响UASB反应器处理PCP的能力。当反应器I的进水[PCP]小于180.8 mg L⁻¹且反应器II的进水[PCP]小于151.6 mg L⁻¹时，进水[PCP]变化对UASB反应器容积产气率和底物产气率影响较小，对出水[VFA]和pH值影响也较小。UASB反应器的容积沼气产气率和底物沼气产气率仅受进水[COD]和负荷率影响。但当反应器II的进水[PCP]大于151.6 mg L⁻¹时，沼气产量迅速下降，3天后停止。反应器II出水[VFA]迅速升至2198.1 mg L⁻¹，pH值降至7以下。反应器II无法正常运行。迅速积累的VFA成分主要是乙酸盐（超过50%）。随着进水[PCP]从7.9 mg L⁻¹逐渐增至180.8 mg L⁻¹，反应器II沼气中甲烷含量从70%降至60%，但反应器仍能正常运行。随后对于反应器II，甲烷含量迅速从75%降至45%左右，反应器II无法稳定运行。因此可以得出结论，UASB反应器进水[PCP]过高主要抑制了利用乙酸盐的产甲烷菌培养物的活性。
