Pham T T H, Brar S K, Tyagi R D, Surampalli R Y
INRS-ETE, Université du Québec, 490, Rue de la Couronne, Québec, Canada.
Ultrason Sonochem. 2010 Jan;17(1):38-45. doi: 10.1016/j.ultsonch.2009.06.007. Epub 2009 Jun 9.
The effect of ultrasonication and Fenton oxidation as physico-chemical pre-treatment processes on the change of rheology of wastewater sludge was investigated in this study. Pre-treated and raw sludges displayed non-Newtonian rheological behaviour with shear thinning as well as thixotropic properties for total solids ranging from 10 g/L to 40 g/L. The rheological models, namely, Bingham plastic, Casson law, NCA/CMA Casson, IPC Paste, and power law were also studied to characterize flow of raw and pre-treated sludges. Among all rheological models, the power law was more prominent in describing the rheology of the sludges. Pre-treatment processes resulted in a decrease in pseudoplasticity of sludge due to the decrease in consistency index K varying from 42.4 to 1188, 25.6 to 620.4 and 52.5 to 317.9; and increase in flow behaviour index n changing from 0.5 to 0.35, 0.62 to 0.55 and 0.63 to 0.58, for RS, UlS and FS, respectively at solids concentration 10-40 g/L. The correlation between improvement of biodegradability and dewaterability, decrease in viscosity, and change in particle size as a function of sludge pre-treatment process was also investigated. Fenton oxidation facilitated sludge filterability resulting in capillary suction time values which were approximately 50% of the raw sludges, whereas ultrasonication with high input energy deteriorated the filterability. Biodegradability was also enhanced by the pre-treatment processes and the maximum value was obtained (64%, 77% and 73% for raw, ultrasonicated and Fenton oxidized sludges, respectively) at total solids concentration of 25 g/L. Hence, pre-treatment of wastewater sludge modified the rheological properties so that: (1) the flowability of sludge was improved for transport through the treatment train (via pipes and pumps); (2) the dewaterability of wastewater sludge was enhanced for eventual disposal and; (3) the assimilation of nutrients by microorganisms for further value-addition was increased.
本研究考察了超声处理和芬顿氧化作为物理化学预处理工艺对废水污泥流变学变化的影响。预处理污泥和原污泥在总固体含量为10 g/L至40 g/L时表现出非牛顿流变行为，具有剪切变稀和触变特性。还研究了宾汉塑性、卡森定律、NCA/CMA卡森、IPC糊体和幂律等流变模型，以表征原污泥和预处理污泥的流动特性。在所有流变模型中，幂律在描述污泥流变学方面更为突出。预处理工艺导致污泥假塑性降低，这是由于稠度指数K分别从42.4降至1188、从25.6降至620.4和从52.5降至317.9；流动行为指数n分别从0.5增至0.35、从0.62增至0.55和从0.63增至0.58，分别对应于固体浓度为10 - 40 g/L时的RS、UlS和FS。还研究了污泥预处理工艺与生物降解性改善、脱水性能提高、粘度降低以及粒径变化之间的相关性。芬顿氧化促进了污泥的过滤性能，使得毛细吸水时间值约为原污泥的50%，而高输入能量的超声处理则降低了过滤性能。预处理工艺也提高了生物降解性，在总固体浓度为25 g/L时达到最大值（原污泥、超声处理污泥和芬顿氧化污泥分别为64%、77%和73%）。因此，废水污泥的预处理改变了流变特性，从而：(1) 改善了污泥的流动性，便于通过处理流程（通过管道和泵）输送；(2) 提高了废水污泥的脱水性能，便于最终处置；(3) 增加了微生物对营养物质的同化作用，以实现进一步增值。
