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Our treatment process

The Ian Bartlett Water Purification Plant (IBWPP) was constructed in 1990 to improve drinking water quality. It is located in the Bass hills near Glen Forbes.

The IBWPP at Candowie Reservoir supplies drinking water to our customers via a large water main to the mainland and Phillip Island.

Raw water from Candowie Reservoir is treated using a combination of oxidation, adsorption, flocculation, coagulation, dissolved air flotation, filtration, pH correction, fluoridation and disinfection at the IBWPP.

The source water is predominantly high in nutrients and organics, and quality is typical of water that is sourced from an open, unprotected catchment. Below highlights the treatment process used at IBWPP.

  • Oxidation

    Oxidation is used to remove iron and manganese from the water. Potassium permanganate is added to aid the removal process.

  • Adsorption

    Adsorption is a process where a solid is used to remove a soluble substance from the water. Westernport Water uses Powdered Activated Carbon (PAC) as the solid in water. PAC is added to the water prior to coagulation to control potential taste and odour issues and to remove algal toxins from the water. The PAC accumulates the soluble substances in the filter, subsequently removing the substance from the water.

  • Coagulation/flocculation

    Coagulation is the process to remove fine suspended particles to aid the removal of colour and turbidity. The particles have a negative charge, allowing them to remain suspended in water. Coagulation involves the addition of a coagulant (aluminium sulphate) to water with a positive charge that neutralises the negative charge, enabling the fine particles to merge to create larger particles. Flocculation involves gentle mixing of the water which increases the particle size to visible suspended solids. The visible particles are called a ‘floc’.

  • Dissolved air floatation and filtration (DAFF)

    DAFF is the process of injecting air particles into water, causing the floc to float to the surface. The floc is then removed to waste and the clear water is filtered through graded filter media. The purpose of DAFF is to produce water low in turbidity. Over time filters become blocked with particles from the floc. To overcome the blockage, the filters are backwashed periodically to allow optimum production in the filters to produce consistently low turbidity results.

  • Fluoridation

    Fluoride is added to treated water to protect against teeth decay and to promote general oral health. Fluoridated water is delivered to all five localities in The Westernport Water distribution system.

  • pH correction

    To ensure treated water is within the ADWG desired range, caustic soda is added to raise pH.

  • Disinfection

    Westernport Water has multiple processes to achieve disinfection. They involve:

    (a) Ultraviolet light: An ultraviolet light (UV) disinfection system was commissioned in 2018 at IBWPP. UV light inactivates microorganisms that may be present in the water supply.
    (b) Chlorine: The final stage of treatment at IBWPP is chlorine disinfection. Disinfection is required to prevent the spread of waterborne pathogens and to retain an appropriate chlorine residual throughout the system.
    (b) Chloramination:We adopt the method of chloramination to address taste & odour issues and total chlorine residuals to the extremities of the distribution system. Chloramination is the process of adding chlorine to a small amount of ammonia. All localities (except Bass) receive chloraminated water. Find out more about chloramination.