Assessing the environmental impact of two options for small-scale wastewater treatment: comparing a reedbed and an aerated biological filter using a life cycle approach

Different options for wastewater treatment have different performance characteristics and also different direct impacts on the environment. These impacts occur over the whole life cycle of the treatment system. Natural wastewater systems such as the reedbed may offer reduced whole life cycle environmental impacts compared to systems with more technical and material sophistication. This paper describes a study of the life cycle impacts of two options for small-scale wastewater treatment which are a horizontal flow reedbed system and a package bio-filtration plant. The study is limited to impacts during the construction and operation phases. Energy use, CO2 emission and solid emissions were chosen as the environmental aspects. It was found that overall the reedbed and conventional systems were quite similar in terms of life cycle energy use. Transport occurring during construction and operational maintenance was a key contributor to energy use and CO2 emissions. The environmental impact of the reedbed reduced if the soil excavated on site was suitable for re-use in the infill. The effect on the results of the different assumptions made during the study was checked using sensitivity analysis. This analysis also helped us to identify recommendations for reducing the life cycle impact of the reedbed system.