Mathematical models of anaerobic digestion for the treatment of swine effluents

ABSTRACT Pig breeding results in the production of large amounts of waste, which can cause serious environmental problems, when handled incorrectly. This study aimed at testing mathematical models to estimate the parameters of anaerobic biodigestion in biodigesters as a function of the composition of swine effluents with and without separation of the solid fraction and hydraulic retention times (HRT). Semi-continuous biodigesters fed with swine effluents with and without separation of the solid fraction and managed for 15, 22, 29 and 36 days of hydraulic retention were used. The potential of biogas and methane production, as well as the reduction of total solids, volatile solids and chemical oxygen demand, were assessed as a function of the effluents composition. HRT was the variable that most influenced the variation of the models, followed by the contents of total and volatile solids. Uni and multivariate models presented high confidence indices, being classified as “great” at predicting the potentials of biogas and methane production and “good” at predicting the reductions of total solids, volatile solids and chemical oxygen demand. The models obtained in this study can be used to reliably predict the parameters of the anaerobic biodigestion process of swine effluents in semi-continuous tubular biodigesters.

摘要：生猪养殖会产生大量废弃物，若处理不当将引发严重的环境问题。本研究旨在针对有无固液分离的生猪养殖废水组分，结合水力停留时间（hydraulic retention time, HRT），测试用于估算厌氧消化池内厌氧消化（anaerobic biodigestion）过程参数的数学模型。本研究采用了分别以固液分离和未固液分离的生猪养殖废水为进料的半连续式厌氧消化装置，运行设置了15、22、29及36天四种水力停留时间。本研究针对养殖废水组分，评估了沼气与甲烷产气量潜力，以及总固体（total solids）、挥发性固体（volatile solids）和化学需氧量（chemical oxygen demand）的削减率。结果显示，水力停留时间是对模型变异影响最大的变量，其次为总固体与挥发性固体含量。单变量与多变量模型均表现出较高的置信度指标：在预测沼气与甲烷产气量潜力时模型评级为「优秀」，在预测总固体、挥发性固体及化学需氧量削减率时评级为「良好」。本研究构建的模型可用于可靠预测半连续管式厌氧消化装置内生猪养殖废水厌氧消化过程的相关参数。