Financial, environmental and social sustainability of rural sanitary wastewater system: case study

Undeveloped sanitary wastewater systems and sanitation often based on septic tanks of unproven tightness, especially in the eastern part of Poland, pose the significant threat to the natural environment and public health. On the other hand, designing the sanitation systems for rural settlements with low population density, limited volume of wastewater, large distances and variable topography may be a difficult task because the proposed design, corresponding to actual law and standards, should not only limit anthropopressure on the environment but also should gain the local population acceptance due to investment as well as operation and maintenance costs. Thus, in our opinion, the variant analysis concerning financial, environmental and social sustainability of proposed sanitary systems is required at the initial stage of the design process. This paper presents variant analysis of financial, environmental and social sustainability of three variants of sanitary wastewater system proposed for the selected rural located in eastern part of Poland. The studied variants covered: vacuum sewage system, pressure sewage system and gravity sewage system combined with the individual, on-site devices for wastewater treatment. The financial analysis was based on three popular indicators of investment cost efficiency: Dynamic Generation Cost (DGC), Net Present Value (NPV) and Benefit-Cost Rate (BCR), while environmental analysis focused on possible intensity and pathways of emissions. Possible employment as well as social involvement and acceptance were selected as indicators for the determination of social sustainability. Then, the obtained results of partial analyses were introduced to weighed sum model (WSM) allowing to determine the most suitable design, attractive for investors as well as for the local population.