Dairy Science Department, South Dakota State University, Brookings 57007, USA.
J Dairy Sci. 2012 Nov;95(11):6188-203. doi: 10.3168/jds.2012-5732. Epub 2012 Sep 12.
Dairy food wastewater disposal represents a major environmental problem. This review discusses microorganisms associated with anaerobic digestion of dairy food wastewater, biochemistry of the process, factors affecting anaerobic digestion, and efforts to develop defined cultures. Anaerobic digestion of dairy food wastewater offers many advantages over other treatments in that a high level of waste stabilization is achieved with much lower levels of sludge. In addition, the process produces readily usable methane with low nutrient requirements and no oxygen. Anaerobic digestion is a series of complex reactions that broadly involve 2 groups of anaerobic or facultative anaerobic microorganisms: acidogens and methanogens. The first group of microorganisms breaks down organic compounds into CO(2) and volatile fatty acids. Some of these organisms are acetogenic, which convert long-chain fatty acids to acetate, CO(2), and hydrogen. Methanogens convert the acidogens' products to methane. The imbalance among the different microbial groups can lead not only to less methane production, but also to process failure. This is due to accumulation of intermediate compounds, such as volatile fatty acids, that inhibit methanogens. The criteria used for evaluation of the anaerobic digestion include levels of hydrogen and volatile fatty acids, methane:carbon ratio, and the gas production rate. A steady state is achieved in an anaerobic digester when the pH, chemical oxygen demand of the effluent, the suspended solids of the effluent, and the daily gas production remain constant. Factors affecting efficiency and stability of the process are types of microorganisms, feed C:N ratio, hydraulic retention time, reactor design, temperature, pH control, hydrogen pressure, and additives such as manure and surfactants. As anaerobic digesters become increasingly used in dairy plants, more research should be directed toward selecting the best cultures that maximize methane production from dairy food waste.
乳制品废水处理是一个主要的环境问题。本文综述了乳制品废水厌氧消化过程中相关的微生物、生化过程、影响厌氧消化的因素以及开发特定培养物的努力。与其他处理方法相比，乳制品废水的厌氧消化具有许多优势，因为它可以在较低的污泥水平下实现更高水平的废物稳定化。此外，该过程产生的甲烷易于使用，所需营养物质较少，无需氧气。厌氧消化是一系列复杂的反应，广泛涉及 2 组厌氧或兼性厌氧微生物：产酸菌和产甲烷菌。第一组微生物将有机化合物分解为 CO2 和挥发性脂肪酸。这些微生物中有一些是产乙酸菌，它们将长链脂肪酸转化为乙酸盐、CO2 和氢气。产甲烷菌将产酸菌的产物转化为甲烷。不同微生物群体之间的不平衡不仅会导致甲烷产量减少，还会导致处理失败。这是由于中间化合物（如挥发性脂肪酸）的积累，这些化合物会抑制产甲烷菌。厌氧消化的评价标准包括氢气和挥发性脂肪酸的水平、甲烷：碳比和产气量。当厌氧消化器中的 pH、出水的化学需氧量、出水中的悬浮固体和每日产气量保持不变时，就达到了稳定状态。影响过程效率和稳定性的因素包括微生物种类、进料 C:N 比、水力停留时间、反应器设计、温度、pH 控制、氢气压力以及粪便和表面活性剂等添加剂。随着越来越多的厌氧消化器在乳制品厂中使用，应该更多地研究选择最佳的培养物，以最大限度地从乳制品废物中生产甲烷。
