Two-stage activated sludge technology is a wastewater treatment method that is typically used to treat wastewater with high organic loads. It divides the wastewater treatment process into two stages: anaerobic and aerobic. In the first stage, the wastewater comes into contact with sludge in an anaerobic environment, where some of the organic material is broken down into simpler organic matter. The second stage is an aerobic environment where microorganisms utilize oxygen to completely decompose the organic matter into water and carbon dioxide, completing the purification of the wastewater. This technology can efficiently treat high concentration organic wastewater and improve wastewater treatment efficiency. When using this dataset for Life Cycle Assessment, it is important to ensure that the boundaries of the assessment include the specific technological processes of the two-stage activated sludge system as implemented in Rattanakosin, Thailand in 2014. This process may exhibit unique characteristics due to its geographical and technological context, which should be accounted for in the LCA model. Users should verify that the data accurately reflects the operation of the two-stage activated sludge system for municipal wastewater treatment and that any assumptions related to scale, efficiency, and environmental impact are applicable to the assessment at hand.