K5/2002 - Evaluation of the DEWATS process

Funded by: Water Research Commission

April 2010 – December 2013

Partner organisations: eThekwini Water and Sanitation (EWS); Bremen Overseas Research and Development Association (BORDA), Permaculture Centre

Project background

The Pollution Research Group, eThekwini Water and Sanitation, and BORDA are investigating the viability of a modularised Decentralised Wastewater Treatment System (DEWATS) for on-site waterborne sanitation and the usefulness of the treated water for agriculture. Following a Memorandum of Understanding between EWS and BORDA signed in 2009, a DEWATS plant was built in Newlands-Mashu for technical evaluation. The modularised wastewater treatment plant consists of a biogas/settler pre-treatment step, an anaerobic baffled reactor, two anaerobic filter chambers and effluent polishing in a constructed wetland. The plant receives up to 40 m3/d of domestic wastewater from the surrounding residential area. DEWATS plants usually cater for settlements from 20 to 2,000 households. The envisaged application for the DEWATS in eThekwini is to provide wastewater treatment to areas with relatively high population density that are beyond the sewer network of the city, such as informal settlements, development and transport nodes, and schools and clinics. The DEWATS process offers an additional benefit of producing nutrient-rich greywater useful for agriculture.

Although BORDA has constructed DEWATS plants in several places in Asia and Africa, no formal evaluation of the DEWATS operations has been conducted. In 2010, the Water Research Commission awarded PRG with funding to conduct an evaluation of the DEWATS plant in Newlands-Mashu, with the specific aims of 1) evaluating the system operations and assessment of load performance conditions; 2) evaluating the use of treated wastewater for agriculture; and 3) exploring new applications for DEWATS. The project has seven deliverables based on different analyses. To date, the West model of batch-fed laboratory –scale anaerobic digester has been developed and tested; data on unsteady-state modelling has been collected from a full-scale digester at the Southern Wastewater Treatment Plant in Amanzitoti; data from a full-scale co-digestion performance model has been collected and analysed; and analyses of different anaerobic digestion and co-digestion scenarios has been completed. In addition, the treated wastewater is being reused in garden areas on the premises incorporating the “Newlands Mashu Permaculture Leaning Centre”, a Municipal Centre of Excellence of eThekwini’s Agricultural Manangement Unit (AMU).

Publications and reports:

Journal Papers

Posters

Conference Papers and Presentations

Pietruschka, B., Pillay, S., Kayser, G.,Foxon, K.M., and Buckley, C.A., 2012. The development of a gas displacement method to determine the bioactivity of anaerobic sludge in DEWATS plants. Paper prepared for International Water Association Conference on Decentralised Wastewater Management in Asia. November 2012, Nagpur, India.
Pillay, S., Pollet, S., Foxon, K.M., and Buckley, C.A. 2012. The influence of membrane surface morphology on the fouling mechanisms of gravity driven membranes coupled to an anaerobic baffled reactor. Paper prepared for WISA Biennial Conference and Exhibition 2012, Cape Town, South Africa.
Pillay, S., Reynaud, N., Schöbitz, L., Foxon, K.M., Schmidt, A., and Buckley, C.A. 2012. An experimental DEWATS plant: Part II; Influence of increased hydraulic loadings on a full-scale BORDA DEWATS treating domestic wastewater. Paper prepared for International Water Association Conference on Decentralised Wastewater Management in Asia. November 2012, Nagpur, India.
Pillay, S., Schöbitz, L., Reynaud, N., Foxon, K.M., and Buckley, C.A., 2012. Practical Experience and operating data from a full-scale decentralised wastewater treatment plant treating domestic wastewater. Paper prepared for WISA Biennial Conference and Exhibition 2012, Cape Town, South Africa.
Reynaud, N., and Buckley, C.A. 2012. Field-data and operations-relevant parameters for communal decentralised wastewater treatment systems. Paper prepared for International Water Association Conference on Decentralised Wastewater Management in Asia. November 2012, Nagpur, India.

Reports and Other

Pillay, S., Reynaud, N., Schöbitz, L., Foxon, K.M., Schmidt, A., and Buckley, C.A. 2011. Evaluation for the DEWATS Process for Decentralised Wastewater Treatment. Progress Report for Water Research Commission.