Self-Purification Potential of Tropical Urban Stream: A Case Study of the New Calabar River in Port Harcourt, Nigeria

T. C. Dikeogu¹, J. I. Onyewudiala², A. C. C.Ezeabasili³, O.N.K. Swift⁴

¹Department of Geosciences, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria

²Department of Mechanical Engineering Federal University of Technology Owerri

⁴Anambra State University Uli

*Corresponding author. E-mail address: dikeogut@yahoo.comonyewudialajulius@yahoo.com, accezeabasili@yahoo.com

Tel: +2348060114036, +2348063314201

Accepted 16 December 2013

Abstract

Dissolved oxygen and biochemical oxygen demand (BOD₁₀) as well as hydrological parameters’ measurements were carried out on the stream to determine its deoxygenation and reaeration rate coefficients in order to ascertain its natural self – purification potential. Deoxygenation rate of 0.15 and 0.16/day were obtained indicating swift depletion of oxygen in the stream probably due to domestic sewage input whereas values of 0.10/day to 0.33/day were obtained as reaeration coefficients and these values suggest deep and slow moving streams. The measured DO values are quite high and indicate high dissolved oxygen concentration in the stream. FAIR’s number-distance plot for these values, and diurnal DO measurement showed respectively that spatially, 69.5% of the stream is under reaeration predominance whereas about 23.3% of the total dissolved oxygen in the stream originates from photosynthetic activity. However, dissolved oxygen profile analysis showed that the stream can re-attain its optimum DO level within flow time of 0.32day in the dry season and 0.21day in the rainy season.

Keywords: Self-Purification Potential, Deoxygenation, Reaeration, Dissolved Oxygen, Biochemical Oxygen Demand, Stream Velocity.