THE FEASIBILITY OF COMBINING THE KISERIAN AND ONGATA RONGAI TOWNSHIPS WASTEWATER TREATMENT PLANTS

Abstract
In towns that lack proper planning, there lacks reserved land for the construction of wastewater treatment works. In most cases, the sites that are identified as technically suitable for such works are located on land already owned and registered to individuals. This makes such projects expensive due to the cost incurred in land acquisition. It also attracts resistance from residents living within and/or in close vicinity to the proposed sites.
The purpose of this study was to determine the technical and economic feasibility of combining the wastewater treatment systems for Ongata Rongai and Kiserian townships. The report concentrates on comparing the per capita cost incurred in acquiring land in both Kiserian and Ongata Rongai townships for the construction of two WWTPs to serve the townships separately to that of combining the wastewater sewerage system so that only one WWTP is constructed in Ongata Rongai to serve both townships.
To achieve this objective, various reports were reviewed so as to determine the appropriate projected population and water demand of both townships to the ultimate design year, 2036. A factor of 0.8 was applied to the water demand giving wastewater flows of 7,975m3/day and 22,800m3/day from Kiserian and Ongata Rongai townships respectively. The Google Earth Pro Software was used to view suitable trunk sewer routes so as to establish the suitability of the project area’s terrain to the adoption of a gravity flow system. The area required for the series of waste stabilization ponds, staff houses and administration blocks was then determined for both cases.
The analysis showed that a total area of 51 acres (20.6 ha) would be required to serve Kiserian Township at a cost of 510 million while 120 acres (52.6 ha) are required for the Ongata Rongai WWTP at a cost of 2.63 billion if the plants were to be constructed separately. For the construction of the combined WWTP, 169 acres (68.4 ha) would be required at a cost of 3.14 billion. The conclusion made from data analysis is that it would be approximately 8% cheaper to construct separate WWTPs than to construct one WWTP to serve both townships.

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