Low-Cost Stormwater Filtration System to Improve Urban Water Quality: The Case of Addis Ababa, Ethiopia

Abstract

Urbanization in developing countries often negatively impacts water re-sources by polluting surface waters. Addis Ababa, Ethiopia, is currently experiencing rapid urbanization accompanied by significant water shortages, unmanaged stormwater, and increasing river water pollution. To supplement the need for non-potable water and address stormwater runoff pollution, we constructed a low cost stormwater filtration system. The filtration system is comprised of a sedimentation area followed by three gravel grain sizes arranged horizontally from coarse to medium to fine filter media. We compared the quality of pretreatment water with post-treatment water by measuring physicochemical parameters, heavy metals and nutrients. We found that the filtration system reduced turbidity by 87%, TSS by 80%, Cu by 87% and Zn by 90%. Further, it positively increased the concentration of DO by 42%. However, the filtration system did not remove nitrates and nitrites. Implementing this system at outfalls in the rapidly expanding condominium housing areas can increase residents’ supply of non-potable water and reduce the amount of polluted stormwater entering nearby streams and rivers.