The growing interest in public health and environmental protection, and the need of resource recovery imposed by the environmental sustainability, induce to look at the anaerobic wastewater treatment as an attractive alternative to the current aerobic treatment practice. In order to exploit the great potential of anaerobic wastewater treatment, thanks to the consolidated technology of high rate bioreactors, the presence in the treated effluent of dissolved CH₄ deserves further investigation to avoid energy loss and to reduce greenhouse gas emissions. Reported concentrations of dissolved CH₄ in anaerobic effluents can account for about half of the total production, thus strategies for its recovery as energy source, or reuse by biological oxidation within the same treatment line, are the keys to approach energy-neutral anaerobic treatment, and to valorize the intrinsic features of such process to be economically feasible and environmentally friendly.

The aim of this review is to offer a complete overview of the available technologies, both for the dissolved CH₄ recovery through physical methods, such as aeration, gas stripping and degassing membranes, and for its biological removal through down-flow hanging sponge reactors and the more recent proposed process based on denitrification and anaerobic CH₄ oxidation (DAMO). Each technology has been deeply described highlighting weaknesses and strengths at different operating conditions and bioreactor configurations. The resulting critical analysis allowed identifying the knowledge gaps still existing in the field and the related research needs.

人们对公共健康和环境保护的兴趣日益浓厚，以及环境可持续性对资源回收的需求，促使人们将厌氧废水处理视为当前好氧处理实践的有吸引力的替代方案。为了开发厌氧废水处理的巨大潜力，得益于高速生物反应器的综合技术，处理后的出水中溶解的 CH _{4 的存在}值得进一步研究，以避免能量损失并减少温室气体排放。报告的溶解 CH ₄浓度在厌氧废水中可占总产量的一半左右，因此将其作为能源回收或在同一处理线内通过生物氧化进行再利用的策略是实现能源中性厌氧处理和发挥内在特征的关键这种工艺在经济上可行且环境友好。

本综述的目的是全面概述现有技术，包括通过曝气、气提和脱气膜等物理方法回收溶解的 CH ₄，以及通过下流式悬挂海绵反应器和最近提出的基于反硝化和厌氧 CH ₄氧化 (DAMO) 的工艺。每种技术都经过深入描述，突出了不同操作条件和生物反应器配置下的弱点和优势。由此产生的批判性分析允许确定该领域仍然存在的知识差距和相关的研究需求。