K5/2220 - Integrating agriculture in designing low cost sanitation technologies

A case study of Kwadinabakubo, eThekwini Municipality

Funded by: Water Research Commission
April 2013 – May 2016

Partner organisations: UKZN School of Agriculture, Earth and Environmental Sciences; eThekwini Water and Sanitation; BORDA; Decentralised Environmental Solutions (DES)

Project description 
In 2013, Soil Sciences and Pollution Research Group, in collaboration with partners BORDA, HERING, DES, and the eThekwini Municipality, embarked on a project funded by the WRC to investigate the benefits and safety of using decentralised wastewater treatment systems (DEWATS) technology in social housing programmes. Low cost sanitation systems like the DEWATS generate effluents with high concentration of nutrients that are beneficial for crop production. However, there is often no means of employing these effluents in a productive and safe manner. Integrating agriculture in the planning and design of low cost sanitation technologies could provide safe and sustainable mechanisms for disposing of such effluent by retaining the nutrients for crop production and releasing water into hydrological systems. This project aims to build on previous work by Soil Science UKZN to generate data on recovery and recycling of nutrients from DEWATS technology that will inform policy makers and town planners in the design of new social housing developments that integrate agriculture. 

The provision of social housing projects in close proximity to cities requires a high density in order to reduce costs and prevent urban sprawl. The eThekwini Municipality is developing plans for a social housing development in KwadinaBakubo, and are considering an alternative approach whereby metered potable water is provided through roof-tanks (5501/house/d), a BORDA Decentralized Wastewater Treatment System/Anaerobic Baffled Reactor (DEWATS/ABR), a horizontal-flow constructed wetland, and an adjacent agricultural area (30m2/hh). The ABR system is successfully used in other developing countries such as Indonesia (Malisie, 2008; Reynaud et al., 2009) and India (Eales, 2012), and the wastewater from the system has been found suitable for irrigation onto agricultural land. Social housing development that integrates agriculture into the planning provides additional employment opportunities and improves household security through the availability of produce and biogas for cooking. The first stages of the research are taking place at the Newlands Mashu Agrohub where a DEWATS plant constructed wetland, growing tunnel and agricultural field plots, field laboratory and offices have been provided by the municipality. 

The project involves the following activities:

  1. Develop soil/water/plant/climate models using Hydrus-2D to predict the outcome of the application of ABR effluent and other excreta derived products on different soils when growing selected crops under different climatic conditions.
  2. Establish focused observation and experimentation of critical parameters and processes for the calibration and validation of the model, including:
    • determination of the amount of land required for agriculture; 
    • the quality of run-off water and its management during the wet season; 
    • determination of water and nutrient-uptake by different plants grown on a range of soil types during the year
  3. Undertake Quality Risk Management Assessment of effluent, agricultural practices, crops grown, and off field mitigation methods. Pot experiments will be carried out in a growing tunnel at Newlands Mashu to determine nutrient uptake, plant responses, residual effects and QRMA data. Irrigation methods will be determined based on the QRMA results and theQMRA predictions will be confirmed by field testing.
  4. Generate information that could be used to develop protocols that integrate agriculture in social housing development schemes.