Level of vegetables contamination
Approximately 496 hectares of land is being farmed using the the polluted water of the Akaki River. Studies have shown that vegetables grown using this water are contaminated by heavy metals - look at table one for details of contamination level and the maximum permissible amount of contamination. These heavy metals have detrimental effect to human health both to consumers and producers and their presence in food needs to be limited.
Water filtration system
Two filtration systems to treat the irrigation waters have been chosen due to the appropriateness of the technologies. These are the anaerobic filtration system and water hyacinths both can treat effluents, grey, black and brown water. All the materials required for building these filtration systems can be sourced locally and managed by the farming communities and the vegetable growers association under which all the farmers by Little Akaki are organized. The filtration systems are semi central and small- scale providing the convenience and opportunity for easy installation along the river at designated intervals. Since the two filtration systems have different capacities they will be used concurrently to complement their strengths and weakness. While the anaerobic system removes all the biological and organic matter the hyacinths will remove the heavy metals.
Anaerobic system: is a fixed bed biological reactor with one or more filtration chambers in series. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the active biomass that is attached to the surface of the filter material. It is a good system for limited space availability, which is the case in Addis Ababa. The materials used to filter the water include gravel, crushed rocks or bricks, cinder, pumice, or specially formed plastic pieces and bacteria build up.
Water hyacinths: have the ability to heavy metals are taken up by the roots of the plant and transported to the shoots and other plant tissues, where they are concentrated. Moreover harvesting and burning water hyacinths can extract valuable heavy metals from its ash. Water hyacinths thrive in wastewater environments, and are particularly efficient at removing heavy metals. As long as water hyacinths are being used in a controlled environment such as a constructed pond, and removed periodically to hinder over growth, it is an efficient and cost effective treatment system. Also since the idea is to implement as small-scale filtration system the hyacinths need to be removed more frequently.
Market access and labelling
The second phase in accessing new markets is through labelling of products, to give public health conscious consumers the opportunity to buy higher quality products. This will give the small-holder farmers a niche that arguably would expand their market share which currently focuses on local consumers to providing coroperate entities, hotels and restaurants.
Why The Hopeful River Project
1) Because we are first and foremost local experts working with local farmers who understand the current circumstances, challenges and opportunities;
2) Because we are working with existing, low-tech, proven technologies that can make a difference quickly;
3) Because we are determined to break the cycle of the negative impacts of rapid development on a city we love.