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

Dagnachew Adugna,Brook Lemma,Larissa Larsen,Geremew Sahilu

doi:10.4236/jwarp.2017.96046

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.

Highlights

The box for the filtration system was made based on the volume of stormwater which can be generated from the rooftop, local street and parking lots
10.42 liters {(12.8 m3 × 70 sec) ÷ (24 hr × 3600 sec/hr)} of stormwater could be filtered per 70 seconds revealing that 0.15 liters (10.42 liters ÷ 70 sec) of stormwater could be filtered per second by the filtration system
To supplement residents’ need for non-potable water supplies and to improve river water quality, we constructed a low cost stormwater filtration system and tested its effectiveness in July through August 2016 by comparing water samples based on levels of physicochemical parameters, heavy metals and nutrients

Summary

Introduction

Access to water as well as housing is two significant problems. In an effort to address Addis Ababa’s housing shortage, the city administration is constructing an extensive number of multi-story, multi-family condominium projects. According to the Addis Ababa Housing Construction and Development Bureau (2014), these multistory condominiums, are located on more than 134 sites throughout the city and are projected to house 1.3 million people upon completion [6]. One of the problems linked with these new developments is a water shortage due to the imbalance between the available water supply sources (such as limited water supply sources and insufficient water infrastructure) and the growing population (the annual rate of population growth is 2.8%) [8]

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Discussion

Conclusion