Sewage pollution in the Coastal waters of Mombasa City, Kenya: A norm Rather than an Exception

Okuku, E.O.; Ohowa, B.; Mwangi, S.N.; Munga, D.; Kiteresi, L.I.; Wanjeri, V.O.; Okumu, S.; Kilonzo, J.

doi:10.22059/ijer.2011.444

Sewage pollution in the Coastal waters of Mombasa City, Kenya: A norm Rather than an Exception

Document Type : Original Research Paper

Authors

E.O. Okuku ¹

B. Ohowa ²

S.N. Mwangi ³

D. Munga ⁴

L.I. Kiteresi ²

V.O. Wanjeri ²

S. Okumu ²

J. Kilonzo ²

¹ Kenya Marine and Fisheries Research Institute, P.O. Box 81651, Mombasa, Kenya, Soil and Water Management Division, Faculty of Bioscience Engineering, Katholike Universiteit

² Kenya Marine and Fisheries Research Institute, P.O. Box 81651, Mombasa, Kenya

³ Kenya Marine and Fisheries Research Institute, P.O. Box 81651, Mombasa, Kenya, University of Nairobi, P.O. Box 30197, G.P.O, Nairobi, Kenya

⁴ Mombasa Polytechnic University, P.O. Box 90420- 80100, Mombasa, Kenya

10.22059/ijer.2011.444

Abstract

This study investigated the effects of sewage discharge on nutrient concentrations and BOD5
levels in the coastal waters and sediments ofthe City of Mombasa. The results indicated that nutrient concentrations in Tudor, Mtwapa and Makupa Creeks were elevated as compared to concentrations in Gazi Creek (mean ranges of 0.022-0.039mg/L, 0.038-0.163mg/L and 0.034-0.118mg/Lphosphates, nitrates and ammonium respectively). Sediments were found to harbour relatively higher concentrations of nutrients than water compartment (mean ranges of 0.217-1.131mg/L, 0.199-0.603mg/L and 9.394-26.73mg/L for phosphates, nitrates and ammonium respectively) thus serving as a reservoir and potential source if sediments are resuspended
during heavy storms or dredging. Based on Chl-a levels, Makupa Creek could be classified as
eutrophic whereas Mtwapa and Tudor Creeks could be placed at the upper limit of higher mesotrophy while Gazi Creekcould be considered as an oligotrophic system. Of the three impacted Creeks, Tudor was found to be the most polluted.

Keywords

Pollution

nutrients

Eutrophication

Chlorophyll a

Sewage