Investigation into the failure of Ubungo stabilization ponds

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Date
1993
Journal Title
Journal ISSN
Volume Title
Publisher
University of Dar es Salaam
Abstract
Stabilization ponds are potentially the most important method of waste-water treatment in hot climates. They are quite affordable and are capable of providing a very high quality effluent. Following the above rather common creed, a full scale waste stabilization pond was commissioned in 1989 to treat waste water from Ubungo Industrial area. Right from the start, this pond system was beset with criticism of being very smelly. Three years later, this pond system had completely collapsed. This research tries to identify the problems that could have precipitated the demise of these ponds so fast. It tries to pinpoint the factors which make this pond system an exception to the otherwise popular belief that stabilization ponds are the best for developing world. All existing data on waste water analysis carried out on the pond effluents were retrieved. In addition, extra sampling was carried out to assess the extent of deterioration in terms of performance. Interviews were held with the DSSD officials, under whose jurisdiction the ponds lie. On assessing all the obtained information, a conclusion is drawn that the pond physical structures have broken down because of lack of maintenance as well as poor embankment construction of the last two maturation ponds. The overall system efficiency has taken a steep downward trend. The BODS removal performance has fallen to 47.8% (Nov 92 - Jan 93) compared to 72.9% (Feb 91 - April 91). Faecal coliform removal presently stands at only 8 8 %. The poor and further deteriorating performance is a result of several factors. These include the total lack of maintenance and the collapse of pond physical structures including the emptying (hence loss) of the last maturation pond. Unsound waste water production methods such as batch waste-water effluents from Urafiki Textile factory have further worsened the performance. The omission of the consideration (or the downplay) of industrial toxicity during the design of the ponds is also a significant factor contributing to the poor performance. It is noted that though the discharge (and hence organic loading) of the ponds was underestimated in the design, these ponds are capable of handling the present industrial discharges just as they used to in their first year of commissioning. They cannot however take on extra loading such as cesspit emptier loads without risks of malfunctioning and foul smells. The presence of heavy metals namely copper and chromium is noted. Their concentration does constitute a problem though not very severe. It cannot be overlooked however because of the property of bio-accumulation of metals in fauna and flora. Suggestions of wastewater minimisation at Urafiki Textile are presented and a call to utilise modern recycling and/or water balancing techniques in the factories is made.
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Available in print form
Keywords
Stabilization ponds, Sewage disposal
Citation
Kayondo, N.H (1993) Investigation into the failure of Ubungo stabilization ponds, Masters dissertation, University of Dar es Salaam. Available at (http://41.86.178.3/internetserver3.1.2/detail.aspx)