Upper Ruvu Water Supply System
Water Treatment Plant (WTP)
The intake of the UR plant is located 65 km west of DSM. Raw water is pumped to treatment works 6 km away at Mlandizi.
The first development of this scheme of capacity 18,000 m3/d occurred in 1959 and has been expanded in stages to reach a capacity of 82,000 m3/d. The treatment plant comprises the following:
- Intake on the Ruvu River: First intake constructed in 1956, another in 1991. Minimum recorded flow in the Ruvu River at the intake site was 1.72 m3/s in January 1961, maximum flow 1180 m3/s in April 1983. Design and operating capacity of the intake is > 2.21m3/s.
- Raw water pumping station: Single compartment sump receiving raw water from the grit chamber overflow, 4 vertical pumps of discharge 0.37 m3/s
(3 duty + 1 standby), and head 66 m, total pumping capacity 1.1 m3/s.
- Raw water pumping mains: 3 welded steel mains of diameters ranging from DN 350 to DN 760 mm in a distance of 6 km.
- Chemical room: Chemicals dosed into a single raw water main.
- Clarifiers: 32 units of upflow solids contact type, dimensions 7.5×7.5×5.5 m depth each, total capacity 1.1 m3/s.
- Filters: 15 units of rapid gravity sand filters of Paterson Candy type.
- Disinfection: Pre and post chlorination gas.
- Clear water tanks: 2 compartment reinforced concrete circular tank adopted on ground, dimensions 40 m diameter and 4.5 m height, total capacity 5,450 m3.
- Clear water pumping station: 4 horizontal pumps (3 duty + 1 standby), of discharge 0.316 m3/s and head 205 m (operating head 155 to 170 m), total capacity 0.95 m3/s.
System Upgrade (2011-2015)
The plant have recently been expanded to increasing water production in the water works facilities by 50%; thus increasing the treated water output from 82,000 to 196,000 m3/d. The expansion work has been completed and the new plant will be in full production from March 2016
The new additional water pipeline to transfer the additional 114,000 m3/d (total flow 196,000 m3/d), is being constructed and will start operation in March 2016.
Kimara Reservoirs receive treated water from the UR system. The reservoirs comprise three circular tanks, two of them are exposed and have a capacity of 8000 m3 each and the third one is buried and has a capacity of 18,200 m3. The total capacity of the three reservoirs is 34,200 m3, which accounts for about 9 hours storage of the UR WTP current capacity. The top water level of the reservoirs is 135.9 m asl. Chlorination takes place inside the reservoirs.
Upper Ruvu Transmission System
A combination of 3 mains of welded steel pipes of diameters ranging from 350 to 660 mm, conveying raw water to a distance of 6 km from the intake to the UR plant. C-value is 90 equivalent for one pipe of diameter of 950 mm.
3 transmission mains of diameters ranging from 520 to 900 mm conveying treated water to a distance of about 51 km from the UR plant to Kimara Reservoir with many off-takes along its route. Pipe materials are CI, steel and DI. The transmission mains suffered leakage at some off-takes, some non functional washouts and air valves, and alum deposits in pipes, with C-value ranging from 80 to 90. Four tanks of capacity 500 m3 each are connected to the mains at Kibaha, Tumbi and Kibamba.