Resource information
A general overview and technical details of natural treatment systems (NTS) including constructed wetlands (CWs), waste stabilization ponds (WSPs), duckweed ponds (DPs), water hyacinth ponds and polishing ponds have been provided in Chapters 8 and 10. As outlined in Starkl et al. (2013), often assessment studies focus on technical aspects only, with no or little consideration of the non-technical aspects. It has been argued that the non-technical aspects do influence the long-term sustainability of technologies and therefore their critical assessment is of importance. This chapter compliments the previous information through investigations on environmental, health and safety as well as economic, social and institutional aspects of those technologies. The work presented here encompasses an initial sustainability appraisal of currently existing NTSs followed by a strength-weaknesses-opportunities-threats (SWOT) analysis. NTS utilise natural processes such as attenuation and buffering capacity of natural soil-aquifer and plant-root systems and as such, the process of contaminant removal is not aided by the input of significant amounts of energy and/or chemicals (Sharma & Amy, 2010). NTS can be classified as soil-based and aquatic treatment systems. Examples for soil-based systems are horizontal sub-surface flow constructed wetlands (HSSF-CWs), soil aquifer treatment systems or planted filters. Aquatic systems are DPs or WSPs. They can be used as secondary or tertiary treatment systems and in combination with conventional and other NTS (hybrids) or be solely based on the influent water quality and intended reuse of the treated water. It has also been reported that a combination of different treatment technologies allows for improved water quality of the effluent (Alvarez et al., 2008; Mbuligwe, 2004; Kaseva, 2003). The survey of existing NTS across India showed that the NTS for wastewater treatment are WSPs and DPs; other technologies such as modified CWs and floating wetlands have been implemented only at pilot scale so far. A detailed overview of NTS in India can be found in Chapter 8.
