Fully mixed activated sludge technology is a biological treatment method that utilizes microorganisms to convert organic substances in wastewater into water and carbon dioxide. By fully mixing and reacting sewage with activated sludge, it achieves the purpose of efficiently purifying wastewater and is widely used in urban and industrial wastewater treatment. Users of this data set should note that the information is specific to municipal wastewater treatment facilities utilizing complete mixed activated-sludge technology in Dindaeng, Thailand, during 2014. The data should be used with caution when applying to different geographical locations or timeframes, as the technology, regulations, and influent wastewater characteristics may vary. Users should also consider any updates to technology, regulatory changes, or shifts in influent composition when utilizing this data set. If the intention is to use the data in life cycle assessment, appropriate allocation procedures must be followed, especially if there is a co-product or waste recycling involved.