In developing countries with large Millennium Development Goals (MDGs) sanitation indicator, pollutant discharge reduction function of wastewater treatment systems should be considered. In this paper, pollutant generations per capita (PGCs) and pollutant discharges per capita (PDCs) are estimated as a base dataset for wastewater management in Thailand. PDCs of black water, i.e. toilet wastewater, are found to be much smaller than PGCs of black water. However, PDCs of gray water, i.e. municipal wastewater other than toilet wastewater are large. Gray water is often discharged without treatment and contributes much to ambient water deterioration. Moreover, possible 5-day biological oxygen demand (BOD5) discharge reductions with “soft interventions”, i.e. measurements in households to reduce wastewater pollutant discharge such as using a paper filter or a plastic net in kitchen sinks and so on, are estimated as 39, 21 and 34% for BOD5, total Kjeldahl nitrogen (TKN) and phosphate (PO4-P), respectively. For the estimation, environmental accounting housekeeping (EAH) books of domestic wastewater, spreadsheets with pollutant discharges by water usages and possible effects of “soft interventions” are applied. The framework of this study with “soft intervention” effects on pollutant discharge reductions should enhance wastewater management especially in the areas under development of wastewater treatment systems.