Zinatizadeh A A L, Mohamed A R, Mashitah M D, Abdullah A Z, Hasnain Isa M
Water and Environment Division, Water and Power Industry Institute for Applied and Scientific Higher Education, Kermanshah, Iran.
Water Environ Res. 2007 Aug;79(8):833-44. doi: 10.2175/106143007x156646.
In the present study, characteristics of the granular sludge (including physical characteristics under stable conditions and process shocks arising from suspended solid overload, soluble organic overload, and high temperature; biological activity; and sludge kinetic evaluation in a batch experiment) developed in an upflow anaerobic sludge blanket fixed-film reactor for palm oil mill effluent (POME) treatment was investigated. The main aim of this work was to provide suitable understanding of POME anaerobic digestion using such a granular sludge reactor, particularly with respect to granule structure at various operating conditions. The morphological changes in granular sludge resulting from various operational conditions was studied using scanning electron microscopy and transmission electron microscopy images. It was shown that the developed granules consisted of densely packed rod- (Methanosaeta-like microorganism; predominant) and cocci- (Methanosarsina) shaped microorganisms. Methanosaeta aggregates functioned as nucleation centers that initiated granule development of POME-degrading granules. Under the suspended solid overload condition, most of the granules were covered with a thin layer of fiberlike suspended solids, so that the granule color changed to brown and the sludge volume index also increased to 24.5 from 12 to 15 mL/g, which caused a large amount of sludge washout. Some of the granules were disintegrated because of an acidified environment, which originated from acidogenesis of high influent organic load (29 g chemical oxygen demand [COD]/L d). At 60 degrees C, the rate of biomass washout increased, as a result of disintegration of the outer layer of the granules. In the biological activity test, approximately 95% COD removal was achieved within 72 hours, with an initial COD removal rate of 3.5 g COD/L d. During POME digestion, 275 mg calcium carbonate/L bicarbonate alkalinity was produced per 1000 mg COD(removed)/ L. A consecutive reaction kinetic model was used to simulate the data obtained from the sludge activity in the batch experiment. The mathematical model gave a good fit with the experimental results (R2 > 0.93). The slowest step was modeled to be the acidification step, with a rate constant between 0.015 and 0.083 hours(-1), while the rate constant for the methanogenic step was obtained to be between 0.218 and 0.361 hours(-1).
在本研究中，对用于棕榈油厂废水（POME）处理的上流式厌氧污泥床固定膜反应器中形成的颗粒污泥特性（包括稳定条件下的物理特性以及由悬浮固体过载、可溶性有机负荷过载和高温引起的过程冲击；生物活性；以及在批次实验中的污泥动力学评估）进行了研究。这项工作的主要目的是提供对使用这种颗粒污泥反应器进行POME厌氧消化的适当理解，特别是关于在各种操作条件下的颗粒结构。使用扫描电子显微镜和透射电子显微镜图像研究了各种操作条件导致的颗粒污泥形态变化。结果表明，形成的颗粒由紧密堆积的杆状（类似甲烷八叠球菌的微生物；占主导）和球状（甲烷鬃毛菌）微生物组成。甲烷八叠球菌聚集体作为成核中心，启动了降解POME颗粒的颗粒形成。在悬浮固体过载条件下，大多数颗粒被一层薄薄的纤维状悬浮固体覆盖，颗粒颜色变为棕色，污泥体积指数也从12至15 mL/g增加到24.5 mL/g，这导致大量污泥流失。由于高进水有机负荷（29 g化学需氧量[COD]/L·d）的产酸作用导致酸化环境，一些颗粒解体。在60℃时，由于颗粒外层解体，生物质流失速率增加。在生物活性测试中，72小时内实现了约95%的COD去除，初始COD去除率为3.5 g COD/L·d。在POME消化过程中，每去除1000 mg COD/L产生275 mg碳酸钙/L的碳酸氢盐碱度。使用连续反应动力学模型模拟批次实验中从污泥活性获得的数据。该数学模型与实验结果拟合良好（R2>0.93）。最慢的步骤被模拟为酸化步骤，速率常数在0.015至0.083小时-1之间，而产甲烷步骤的速率常数在0.218至0.361小时-1之间。
