The processes of water treatment, for sustainable water use and creation of safe water systems. A study at Nakivubo water plant and Ggaba water treatment center (Ssusume Patrick)

1. Ssusume Patrick - DSTVE Makerere University
A STUDY REPORT ON THE PROCESSES OF WATER TREATMENT AT NAKIVUBO
WASTE WATER PLANT AND GGABA WATER TREATMENT PLANT OF NSWC.
National Water and Sewerage corporations has two arms, waste water treatment and clean water
treatment.
NAKIVUBO sewage treatment plant.
This plant is located in Bugolobi where by it receives municipal waste water and treat it in order
to improve public health issues and to ensure environmental protection. Municipal waste is the
sewage that comes out from residential places. This sewage is categorized into black waste water
that comes out of the water borne toilet facilities and grey waste water that comes out of non-
toilet facilities such as laundry, rain.
The source of this municipal waste water received by the plant is Kampala and it receives 15%
of waste water from Kampala which totals 30% of the entire country Uganda. The plant
receives waste water from Kampala business district like areas of Kololo, Muyenga, Kabalagala,
Nsambya and so this waste water flows by gravity and also pumping at Kibira road to the plant.
This plant uses conventional system technologies to treat this received waste water and it
encompasses the use of electro mechanical equipment and natural processes to treat the waste
water since it takes shorter retention time.
Process of waste water treatment
Sewage treatment at the plant is taken into three stages that is the pre-treatment stage, primary
stage and the secondary treatment stage
1. Pre-treatment stage. This involves two stages that is screening and; degreasing and degritting.
In screening, hard solid particles such as stones, plastics, large organic matter that come with
waste water are removed by the screens of the sewer network. While in degreasing, oils which
may block oxygen supply when treated waste water is released into water body are removed. In
degritting, small stones and sand which come with waste water are removed.
Primary treatment stage. This involves two stages that is primary sedimentation which
involves separation of the solid from the liquid whereby the solid/sludge settles to the bottom
and then water is pumped to the trickling filters which is the second stage, these filter water and
reduce the BOD of water and allow aerobic bacteria to break down organic matter in the water.
Water then flows to the secondary sedimentation tank.
Secondary treatment. This works like the primary sedimentation tank but gives time for the
sludge that didn't settle in the primary sedimentation tank to settle, then water that overflows is
safe for disposal and then is discharged into Lake Victoria.

2. Ssusume Patrick - DSTVE Makerere University
GGABA WATER TREATMENT PLANT.
It receives water from Lake Victoria. The challenges faced with this water source are lake water
pollution from nearby communities thus high cost of water treatment, as well there is also
fluctuations in the water levels of the water Source whereby sometimes they go low.
Main stages of water treatment.
Bar screening this involves removal of plastics, algae, and solid waste to avoid it entering the
plant which may interfere with the treatment process. After screening water moves by gravity to
the underground tanks.
Pre-chlorination, chlorine is added to water to kill the pathogens, to oxidize the algae and
remove the bad smell.
Coagulation, coagulants such as alum, polymer both in solution are added to the water. These
coagulants are positively charged and thus they neutralize the negatively charged particles such a
as dirt in water, then these particles bind together to form large particles.
Flocculation this involves mixing water as well as varying the speed at which water moves
whereby speed is slowed down to foster the increase in size of the floccs. Water then flows to the
sedimentation tank.
Sedimentation.in here water enters the sedimentation tanks and is left there for some few
minutes such that the heavy solid particles/flocs plus suspended materials settle down at the
bottom of the tank and these materials that settles called sludge, are removed by the process of
desludging. This water now moves to the filters.
Filtration; in here filters of sand are used whereby water passes through the filter bed and
collects in the filter through and then water moves to the contact tank.
Post chlorination in the contact tank, water is disinfected by chlorination. Water is
continuously monitored for Physio-chemical parameters such as PH and water enters the clean
water tank for storage and finally is lifted by pumps to reservoirs and distributed to the respective
areas around Kampala. The distributed water contains a small percentage of chlorine which kills
pathogens found in the pipes that transport this water to the final consumer. Possible
contamination from water clean water tanks to the tap include algae in the pipes, corroded metal
pipes, some pathogens may be inhabitants in the pipes, broken pipes during road construction
exposes water to contamination.