Small town municipalities stand to benefit from a multi-year, interdisciplinary research platform being established at the CSIR.
Dr Louis Waldeck
Researchers are investigating models of sustainable and integrated municipal service delivery that could be operated as viable business concerns independent of the municipality's ability to recover costs, while not depriving the municipality of a key source of income. Providing municipal services like waste water treatment is a major challenge for small towns that often lack the capacity to manage and maintain infrastructure. Poverty in towns also presents cost-recovery challenges to the municipalities.
Alternative solutions to municipal service delivery problems will be developed, in particular to mitigate and adapt to climate change while simultaneously contributing to food, energy and water security and creating local economic opportunity.
"We completed a comprehensive feasibility study recently, which brought us one step closer to establishing an integrated research platform on the CSIR campus in Pretoria consisting of a number of outdoor laboratories and associated research programmes, collectively known as IRIP," says project leader Dr Louis Waldeck.
The project follows an industrial ecology approach, which is the sustainable combination of the environment, economy and technology, with waste from one process becoming the input of another. The processes being considered include the provision of energy, clean water and the collection and treatment of waste water and solid waste. The CSIR has considered the application at two scales - a small town of about 5 000 households and a large building or building complex.
Waldeck explains that at the small town scale, a typical application built in close proximity to the existing waste water treatment works would comprise the following: A heliostat array that concentrates sunlight on a solar collector with the heated air driving a gas turbine to generate electricity. The heliostat field is designed to capture more energy than the turbine requires and the excess heat is stored so that electricity can be generated at night.
Sludge from the primary waste water treatment plant is pumped into an anaerobic digester where it is digested by bacteria to produce carbon neutral biogas to generate additional electricity. The biogas yield can be improved by adding animal slurry and other forms of organic solid waste separated at source. Using the carbon dioxide from the combustion process, nutrients from the waste water and sunlight, micro-algae, are grown and harvested to produce carbon neutral biodiesel to also fuel the gas turbine.
Economic opportunities and food security are promoted by using the various waste streams (water, heat and nutrients) to produce food through farming activities including aquaculture and hydroponics. Vast amounts of waste heat are available for maintaining such operations within an optimum temperature range, as well as for producing distilled, bottled water and ice, providing cold storage based on absorption chillers and promoting water security by desalinating brackish groundwater.
"Small municipalities can hardly afford to lose any of the income derived from selling water and electricity, and few might have the expertise required to build and operate the relatively sophisticated plant envisaged. The question is whether the private sector would be interested in building and operating the plant on behalf of the municipality," comments Waldeck.
"During the feasibility study we simulated the annual income statement of a fictitious company by taking account of income generated from the sale of electricity, carbon trading and food produced by intensive farming, the cost of labour and capital, operation, maintenance, security, insurance, etc."
Due largely to the feed-in tariff of R2,10/kWh announced by NERSA recently for solar energy, the results of the simulation confirmed that such an operation could be financially viable from income sources limited to selling electricity, surplus biodiesel, carbon trading, aquaculture and bottled water. With considerable scope for optimising the design, achieving better economies of scale and augmenting income by considering other means of food production such as hydroponics, it is likely that the operation could be made even more attractive.
At the scale of a large building or building complex, a different configuration of more compact components will be required based on membrane bioreactor technology for self-contained waste water treatment and parabolic trough or linear fresnel collectors to capture heat for space heating and cooling purposes. An advanced laboratory is planned for developing material, production and assembly technologies for the construction and operation of buildings with improved resource efficiency through their entire lifecycle.
"The four other laboratories to be established at the CSIR will be used for investigating and refining anaerobic digestion, aquaculture (including algal culture), concentrating solar power and membrane bioreactor-based waste water treatment," concludes Waldeck.
Enquiries: CSIR Communication