考虑pH值和挥发性脂肪酸影响的填埋城市固废厌氧降解模型

建立了描述填埋城市固体废弃物降解过程和行为的2阶段厌氧降解机理模型.模型考虑了含水率、挥发性脂肪酸(VFA)和pH值等主要环境因素的作用.为了适用于不同渗滤液酸化水平下的降解,单独考虑了pH值和分子态VFA对甲烷菌繁殖的影响.建立了气相高CO2分压下的渗滤液pH值计算方程,并给出了降解环境中CO2分压的计算方法.通过对一固废降解试验的模拟验证了模型的有效性.最后,采用所建立的pH值计算方程揭示了填埋环境下高CO2分压对渗滤液pH值影响显著,渗滤液pH值与VFA间缺乏不同酸化水平下的一致对应关系和高酸化水平下pH值对VFA浓度变化不敏感、分子态VFA抑制作用明显等规律.

An anaerobic degradation model for landfilled municipal solid wastes considering effects of pH and VFA

A two-stage anaerobic degradation mechanistic model was developed to describe degradation processes and behaviors of municipal solid wastes (MSWs). Primary environmental factors, including moisture content, VFA and pH, were considered in this model. In order to simulate degradations in different leachate acidified situations, effects of unionized VFA and pH on methanogenesis were considered separately. An equation calculating leachate pH under high CO2 atmospheric pressure was presented, and an approach for estimating CO2 pressure in landfilled conditions was provided. The effectiveness of this model was demonstrated by simulating a degradation experiment of MSWs. Finally, analyses were conducted with the presented pH calculating equation. Results showed that high CO2 pressure in landfilled environment affected leachate pH remarkably; a consistent correlation between pH and VFA at different acidified levels was not available; under highly acidified condition leachate pH was not sensitive to VFA concentration change and the inhibition caused by unionized VFA was considerable.