Lower Ruvu Water Supply System
Water Treatment Plant
The Plant was constructed in 1975 with a nominal capacity of the LR WTP is about 180,000 m3/d.
• Intake on the Ruvu River: Design and operating capacity 386,000 and
• Intake main: Pre-stressed concrete DN 1350 mm main, capacity 286,000 m3/d for a length of 504 m, followed by 2 pre-stressed concrete DN 1200 mm mains for a length of 75 m.
• Raw water pumping station: 2 sump wells, 3 vertical pumps (2 duty + 1 standby), of discharge 1.1 m3/s and head 24 m each, total capacity 2.5 m3/s.
• Chemical room: Chemicals dosed into 2 raw water mains with inline mixers.
• Clarifiers: 2 clarifier units of upflow solids contact type, clarifier dimensions
38.1 x 38.1 x 5.5 m depth each, total capacity 1.3 m3/s for intermittent flow and 1.05 m3/s for continuous flow.
• Filters: Rapid gravity sand filters, 8 units of capacity 0.26 m3/s.
• Disinfection: Pre and post chlorination gas.
• Clear water tanks: Reinforced concrete tank of 2 compartments under the filters, total capacity is 4,720 m3.
• Clear water pumping station: 3 horizontal pumps of discharge 1.05 m3/s each and head 108 m (2 duty + 1 standby), total capacity 2.1 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 180,000 to 270,000 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 90,000 m3/d (total flow 270,000 m3/d), is being constructed and will start operation in March 2016.
University Reservoirs receive treated water from the LR system. The reservoirs comprise two reinforced concrete tanks, one exposed and the other buried. The total capacity of the reservoirs is 45,400 m3, which accounts for about 6 hours storage of the LR WTP current capacity. The top water level of the reservoirs is 70.2 masl. Chlorination takes place inside the reservoirs. The reservoirs needed the same remedial actions proposed for Kimara Reservoir.
Wazo Hill Tank of capacity 5,000 m3 was proposed to cater for Mbezi distribution area (currently under construction). The site elevation of the tank is 70.2 masl.
LR water transmission system, comprising the following:
A pre-stressed concrete transmission main of length 504 m and diameter DN 1350 mm conveying raw water to a T-junction, of C-value 125, followed by 2 pre-stressed concrete DN 1200 mm mains for a length of 75 and 80 m to the LR plant, of C-value 100. The main is in good condition.
A pre-stressed concrete transmission main of length about 55 km and diameter 1350 mm conveying treated water from the LR plant to University Reservoir, with 27 off-takes serving areas along its route, suffering the same problems encountered in the LR transmission main. These off-takes are of cast iron, galvanized steel and uPVC with diameters ranging from DN 63 to 200 mm, and C-value ranging from 80 to 90.
The treated water transmission main is reported to have a design C-value of 145, which corresponds to a carrying capacity of 182,000 m3/d for the existing pipe.