| Abstract | On-site sanitation systems such as pit latrine have widely been used in either developed or developing countries, especially in the areas with no sewerage systems. There are several types of on-site sanitation systems such as septic tank, leaching of which are not well performed systems, and anaerobic up-flow filter have been used in developing countries. This study assesses three types of the on-site sanitation systems: (i) the one cesspool system, (ii) the two cesspools system in series and (iii) the package tank system at Muaeng Klong Luang Municipality, Klong Luang district, Pathum Thani Province, Thailand. The assessments considered 5 aspects: environment, health, social, economy, and technical function. Characteristics of black water or influent of the on-site sanitation systems were investigated in this study including squat or pour flush latrine and flushing latrine. Based on 5 months investigations, the results revealed that black water is produced from a pour flush latrine at a rate of 30 L/d and having pH of 8.30, COD of 4,600 mg/L, BOD of 2,900 mg/L, TKN of 700 mg/L, NH3 of 460 mg/L, P04 3- of 70 mg/L and FC of 4.1 x 108 MPN/100 mL. Whereas, a flushing latrine produce black water at a rate of 80 L/d and having pH of 8.20, COD of 1,500 mg/L, BOD of 1,100 mg/L, TKN of 270 mg/L, NH3 of 200 mg/L, P04 3- of 20 mg/L and FC of 1.8 x 108 MPN/100 mL. The priority of sustainability indicators in this study area are (i) social, (ii) environment, (iii) health, (iv) economy and (v) technical function. Relative comparisons among the onsite sanitation systems based on scoring system showed that three systems (one cesspool system, two cesspools system in series and package tank system) obtained low scores on environmental consideration. Health problem in this study area was unlikely related to the environmental condition. The three systems could obtain high score on social consideration especially on attitude, knowledge, practice and acceptance, but low on awareness. One cesspool system obtained highest scores on economic consideration, whereas the two cesspools system in series was lower and the lowest at the package tank. In conclusion. priorities of the sustainability of three on-site sanitation systems in this study area were (i) one cesspool system (161 scores), (ii) two cesspools system in series (158 scores) and (iii) package tank system (146 scores). |