Kuala Muda District - Water Treatment Plant

Venue : Water Treatment Plant Pinang Tunggal
Time : 2.30 pm
Topic : Water treatment
Persons in charge : PPKP Selva


We had a visit to the Loji Pembersihan Air Pinang Tunggal guided by Mr.Selva. This water treatment plant is located about 12 km south of Sungai Petani and is able to supply about 45.5 millions of litre per day to Sungai Petani Utara and Selatan, Gurun, Tikam Batu and Pantai Merdeka. These treatment plants cleanses, treats and filters the river water to ensure the water is safe for the consumers. This treatment plant is run by a private holding which is Air Utara Indah SDN.BHD.
We were explained by the staffs of the water treatment plant on the different stages of water treatment.

1) Raw Water
The raw water pump station for this plant is located on the banks of Sg. Muda, 500metres from the administration building. It comprises screening system, motor pumps, panels, surge vessels, electrical appliances such as switchboards and transformers.

• Water screening: raw water is screened to remove large particles e.g leaves, twigs and wastes. Inorganic substances will turn into sediments around a special device. These sediments will be removed from the water using a sand suction system. Sediments need to be removed from the system at least once a day.
• Raw water pump: the raw water pump operates 24hours and the number of pumps operating depends on the demand. Flowmeter is set outside the station to measure the volume of the water pumped in. The rate of the water flow is important in ascertaining the dosage of chemicals needed for the treatment.

2) Aeration
Thru this process, oxygen from air will oxidize ferum, manganese, and other metals to non-dissolve substances. This process will also release gasses like carbon dioxide and hydrogen sulphide from the water to remove rust, odour and taste. This will also adds more dissolve oxygen in the water.

3) Chemical emulsification
This process will cause the small particles to become unstable and combines chemically to form flocs. Aluminium sulphate is the chemical used. Aluminium sulphate is available in the form of cubes (Kibbles). It is diluted up to 10% solvent before usage. The dosage required depends on the quality and quantity of raw water.

4) Flocculation
When aluminium sulphate is mixed with water, reactions takes place between the aluminium ions and the colloids to form microscopic particles which then conglomerates with each other. They then form flocs which are compacted, heavy and easily sedimented. This process takes place in a softening tank which has planks (baffles). These planks contain multiple slits to ensure more time for the aluminium to react completely in water.

5) Sedimentation
Due to gravity, the flocs are sediment in the sedimentation tank. Besides sedimentation of the colloids and floating particles, this process also removes potential bacteria and viruses. Every phase has its own sedimentation tank and the retention time for each tank is 2 hours. To ensure the sedimentation process is effective, this tank is cleaned at least once a month.

6) Filtration
The water that flows from this sedimentation tank will be filtered to remove fine & light colloids which are not able to be sediment, colouring agents & bacteria. There are 6 units of filters in the Pinang Tunggal water treatment plant. They are of the rapid gravity type which has 2 layers of sand with different sizes and thickness. The first layer which is the bottom layer is of 200mm thickness and the size of the gravel is 1.18 – 2.36mm. The second layer above is off 700mm thickness and the size of the grain is 0.6 – 1.18mm. Beneath these filters, lie hundreds of nozzles which have multiple fine holes. These nozzles function to ensure the fine sand is not taken along with the filtered water.

7) Softening
Calcium hydroxide (lime) is added into the filtered water to adjust its pH value to a safer pH range for consumption. This is important because, during the chemical emulsification process, addition of ‘alum’ contributes to the acidity of the water. Lime also functions to form a coating layer around the pipe to prevent rusting.

8) Fluoridation
Water released by the plant is enriched with fluoride. Fluoride salts used are sodium silicofluoride. The dosages of fluoride are as recommended by the Jabatan Pergigian Malaysia, 0.7mg/L.

9) Chlorination
Chlorine is added to the filtered water for disinfection. Chlorine reacts by killing harmful bacteria and viruses in the water. Chlorine gas is supplied in drums with a net weight of 930 kg each. It is then added into water using the vacuum system. Recommended and allowed dosage of chlorine in water in within 1.5 to 2 mg/L.

10) Treated Water Tank
The processed water is collected in a treated water tank. In this tank all chemicals that have been added previously will react completely. Water from this tank will then be channelled to a balancing tank to be distributed to the consumers.

11) Laboratory
The lab functions as a quality control centre for the water that is processed. Physical and chemical tests are carried out every 2 hours. Bacteriological tests are carried out once a day to ensure the water is free of any potential microorganisms.