Fly-ash Lime Filter Tower
This tower treats grey water at the source allowing reuse and recycling of this increasingly precious commodity. The tower consists of several layers of mostly waste items, which together act to purify the water. Fly-ash (a waste product) and lime form the first of the layers in the tower and sterilise the grey water by increasing the pH. An alien plant, a water hyacinth, forms the next layer which neutralises the water pH again. The remaining layers just act as sand filters. Finally, the technology includes a low-cost kit for detecting water contamination by faecal coliforms such that the end user can test for water safety."
Water scarcity in South Africa is an enduring concern and with climate change, the development of systems that can recycle water for use in other ways is key to water security. The design and construction of homes with built-in mechanisms for the treatment and recycling of domestic grey water represents a key solution and an important market opportunity. This system, designed at Rhodes University has been prototyped and piloted in several households. Effective involvement with local and national government could see these integrated into the design and construction of new homes. The system can also be readily integrated into existing homes.
This system, known as the fly-ash lime filter tower is comprised of a series of different layers, which, when placed in a low-cost container with an inlet and outlet pipe serves to sterilize domestic grey water for further use. The are five layers for water purification within the tower. The top layer is composed of fly ash (a waste product) and lime and this layer sterilises grey water by substantially increasing the pH. The resulting highly alkaline conditions kill off bacteria and disinfects the water. Phosphorus is removed in this layer by precipitation with calcium and the chemical oxygen demand is removed with adsorption and straining. The water hyacinth layer is located below the fly ash-lime layer. This consists of water hyacinth plant material which has been removed from areas where this alien vegetation causes substantial harm to aquatic life and water quality. The primary function of this layer is to neutralise the pH of the grey water to values of about 7, the normal pH of potable water. The remaining layers in the tower act as basic sand filters and also provides a matrix for the development of an active biofilm which further treats the grey water.
The system offers a low-cost and easily implementable technology to treat grey water in areas of South Africa where water recycling methods do not currently exist.
The use of low-cost waste materials and alien vegetation to purify water is novel, further, it allows this system to be deployed to any location be it in an urban developed setting a remote rural one.
We wanted to create a system which provides effective and low-cost grey water management and thus contribute to the protection of public health and water conservation in low-income and decentralised settings in South Africa and Africa. It can also serve to treat domestic grey water in urban or developed areas.
The core team consists of three academic staff members/research associates from the Rhodes University Biotechnology Innovation Centre and the Faculty of Pharmacy at Rhodes University. The team is led by biotechnologist Dr. Roman Tandlich. Working on the business aspects of the project is Dr. Bonga Zuma, a former graduate whose Ph.D research is focused on the principles driving the technology presented here. The team members have collective expertise in business, academia, water, sanitation, and biotechnology.