An Engineering Failure Analysis of a Biological Treatment Plant in Nigeria
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FEATURE—PEER-REVIEWED
An Engineering Failure Analysis of a Biological Treatment Plant in Nigeria I. A. Oke Æ K. T. Oladepo Æ J. O. Babatola
Submitted: 25 July 2008 / in revised form: 14 January 2009 / Published online: 21 March 2009 ASM International 2009
Abstract Waste stabilization ponds (WSP) have been found useful and applicable in most parts of the world. Their application has been found in the treatment of industrial, commercial, institutional, and domestic wastewaters. Failures of WSP have not been reported until recently. This then calls for engineering analysis of failed ponds to prevent the recurrence of these ugly events. This paper presents results of an engineering failure analysis conducted on a waste stabilization pond at Obafemi Awolowo University, Ile-Ife, Nigeria. The ponds receive wastewater from selected student halls and academic buildings by gravity as a result of the topography of the campus. The ponds were visited, and influent and effluent qualities of the ponds were determined. Adequacy of the design parameters and structural behavior were studied and compared with the standard code. The study revealed that some of the engineering parameters were higher than the upper limit recommended by the standard code. Solids had accumulated in the ponds, resulting in anaerobic conditions in the ponds, generating hydrogen sulfide and acids as end products. Production of these acids corroded the sewers, I. A. Oke and J. O. Babatola were formerly at Department of Water Resources and Environmental Engineering, Ahmadu Bello University, Zaria. I. A. Oke (&) K. T. Oladepo Department of Civil Engineering, Obafemi Awolowo University, Ile-Ife, Nigeria e-mail: [email protected]
cracked some manholes, and dislocated pipes (sewers). Accumulation of solid also led to sludge formation and thus reduced effective depth, length, and breadth of the ponds and made detention time below the specified range in the standard environmental pollution control code. It was concluded that the failure of the ponds can be attributed to partial adherence to the standard code in terms of vegetation, flood control mechanism, high biochemical oxygen demand and suspended loadings, and flow rate, as well as to low detention; all originated from improper maintenance. Keywords Waste stabilization ponds Anaerobic condition Sewers BOD loadings Flow rate Suspended solid Hydraulic loading Abbreviations BOD Biochemical oxygen demand DO Dissolved oxygen mg/L Milligrams per liter SS Suspended solids D1 and D2 Initial and final dissolved oxygen of the sample respectively (mg/L) f Ratio of seed in the sample to seed in the control p Decimal volumetric fraction of sample used B1 and B2 Initial and final dissolved oxygen of the seeded control respectively (mg/L) APHA American Public Health Association
K. T. Oladepo e-mail: [email protected]
Introduction
J. O. Babatola Department of Civil Engineering, Federal University of Technology, Akure, Nigeria e-mail: [email protected]
Wastewaters are known to be generated every
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