Domestic and industrial wastewaters are categorized as anthropogenic greenhouse gas emission sources. Wastewater collection systems, wastewater treatment plants and discharging wastewater to the environment lead to direct greenhouse gas (carbon dioxide, nitrous oxide, and methane) emission from biological processes and indirect emissions due to energy consumption. In this study, the current status of greenhouse gas emissions from the domestic wastewater sector in Iran and emission scenarios up to the horizon of 2030 were estimated. According to the developed estimations based on the calculation method presented by Intergovernmental Panel on Climate Change (IPCC) for greenhouse gas emissions, methane (144.94 kt/yr) and nitrous oxide (1.47 kt/yr) are emitted directly in the domestic wastewater sector. Thus, wastewater treatment plants are releasing methane (8.542 kt/yr) and nitrous oxide (0.0273 kt/yr) directly along with carbon dioxide (901.77 kt/yr) indirectly. In the next phase of this study, different scenarios of greenhouse gas emissions from the domestic wastewater sector were developed. According to the calculations, the highest emission will occur in 2030, when the people access to wastewater treatment systems increases, while the performance of the wastewater treatment plants has not been improved (6,024.46 ktCO_2e/yr). Also, the lowest emission will occur when people's access to wastewater treatment systems has increased and the performance of these wastewater treatment plants has been improved at the same time (2,739.31 ktCO_2e/yr). According to the result of this study, the best outline will be achieved if the primary focus is on the improvement of wastewater treatment operation by 2025, and since then the focus shifts forward to increasing population coverage and upgrading performance.

生活和工业废水被归类为人为温室气体排放源。废水收集系统，废水处理厂以及将废水排放到环境中会导致生物过程直接排放温室气体（二氧化碳，一氧化二氮和甲烷），并由于能耗而间接排放。在这项研究中，估计了伊朗生活废水部门的温室气体排放现状以及到2030年的排放情景。根据政府间气候变化专门委员会（IPCC）提出的温室气体排放量计算方法得出的估算结果，生活废水直接排放甲烷（144.94 kt / yr）和一氧化二氮（1.47 kt / yr）。因此，废水处理厂直接释放甲烷（8.542 kt / yr）和一氧化二氮（0.0273 kt / yr）以及间接释放二氧化碳（901.77 kt / yr）。在本研究的下一阶段，开发了生活污水部门排放温室气体的不同方案。根据计算，到2030年，当人们使用污水处理系统的人数增加，而污水处理厂的性能未得到改善时，排放量将最高（6,024.46 ktCO_2e / yr）。同样，当人们使用污水处理系统的机会增加并且这些污水处理厂的性能同时得到改善时，排放量将最低（2,739.31 ktCO _2e / yr）。根据这项研究的结果，如果主要重点是到2025年改善废水处理操作，那么将获得最佳轮廓，此后，重点将转移到增加人口覆盖率和提高绩效上。