Turning noxious tannery waste into biogasand reusable water
Presently it is estimated that less than 10% of industries in Eastern Africa treat their industrial and agro processing waste to any degree. This poses a serious health and environmental challenge to the growing population of the region. Bio-Innovate supported scientists across eastern Africa are working on innovative solutions that treat and convert such wastewaterintoenergy, and bio-fertilizer and re-use of the treated water..
Policy makers may be in a dilemma in deciding what comes first, the productsand jobs created by the industries or the health risk posed by the industrial waste generated. On the other hand there is an opportunity for a win-win situation where this waste is converted to valuable by-products. At the banks of Modjo River in Central Ethiopia, the Addis Ababa University scientists supported by Bio-Innovate have installed a pilot facility at Modjo Tannery Ltd that is treating the wastewater generated and converting most of the organic elements into biogas and removing a range of toxic metal used during the tanning process. This Modjo site is one of the wastewater treatment technology being incubated to demonstrates how the public and private sector can partner to address a technological challenge that have a huge impact on the society. The anticipated outcome of this project is that the technology developed can be adopted by similar industries across the region. Tanning is a major industry in Ethiopia with most of the 30 tanneries situated along river banks. If this waste is not treated, it poses a serious danger to communities and their livestock living downstream that depend on the river for their livelihood and the fish in the river. Some of these negative effects are already visible and need to be arrested.
The wastewater treatment system is based on a biological system that is environmentally friendlier and less expensive. The system is composed of two-stage bio-digestion that produces biogas connected to a constructed wetland that removesresidual nutrients and other organic matter as well as trapping heavy metals resulting to treated water that meets national effluent discharge standards.
The project has demonstrated the technical feasibility and social and environmental benefits of the technology and is currently analyzing the cost-effectiveness of the technology with a view to building a business case that will encourage the commercialization of the innovation to be taken up by small and medium scale industries facing similar challenges in the country and region. The innovative solution is the outcome of more than ten years of research and innovation activities involving collaborating partners from national, regional and international organizations including the Royal Institute of Technology (Sweden), Addis Ababa university (Ethiopia), University of Dar es Salam (Tanzania), and Makerere University (Uganda)
Tests done on the site and downstream confirm that the treated water has a potential to be reused by the factory for cleaning, an activity that consumes a lot of water and by the nearby communities for irrigation. The release of treated effluent into the receiving Modjo river will also greatly reduce the pollution burden on the river which is used by downstream communities for cultivating vegetables, livestock consumption, recreational and other domestic purposes.
Thepilot-system is currently generating about 60m3/day of biogas that is used to offset the energy costs of the factory. The annual energy expenditure by the tannery is estimated at USD 28500. If installed full-scale, the pilot plant can result in energy costs savings of up to USD52000 per year.