An environmental life cycle assessment (LCA) of the optimisation of decentralised wastewater treatment systems (DEWATS) in the eThekwini Municipality, South Africa

Abstract

Sanitation in South Africa faces numerous challenges and new technologies are needed to cater for the country’s growing population. One such technology, showing potential in other developing countries, is DEWATS (decentralized wastewater treatment systems). This research investigated the environmental performance and optimisation potential of DEWATS in the local context by employing life cycle assessment (LCA) methodology to 3 possible scenarios. These were defined as (i) a ‘typical’ flush water system, (ii) a reduced flush water system and (iii) a reduced flush water system with urine separation and struvite production to replace a commercial fertiliser. LCAs were performed and the construction and operation of all three systems were modelled. The SimaPro LCA software was employed and 18 different environmental impacts were evaluated by following the ReCiPe midpoint method. This resulted in an environmental profile for each system enabling comparisons. The water consumed for sanitation is the highest single contributor to environmental burdens in all three systems and reducing the amount of toilet flush water not only saves a scarce resource but also decreased most other environmental burdens. The best overall environmental performance was achieved by the system with reduced flush water and the separation and processing of urine to a fertiliser. The use of rainwater for flushing toilets can lead to further improvements for all three systems. When comparing the burdens of the operation of DEWATS with those of their construction, these decrease with the reduction in water consumption, focusing further potential improvements on the materials used in construction. Therefore, this study shows how LCA can be used for local optimisation of DEWATS and guiding further improvements for these systems.