Drinking water treatment

Managing risks to drinking water quality on a catchment level is addressed in two separate ways:

1. prevent possible pollution incidents by controlling potential pollution sources through the Planning process - development is strictly controlled in the Orara River drinking water catchment to prevent water quality problems, as per the Coffs Harbour City Council Rural Lands Strategy (2003); and
2. remove potential risks to water quality through rehabilitation works - Coffs Harbour Water provides funding every year to Orara River Landcare to undertake catchment management with local landholders, including river bank stabilisation, weed eradication and revegetation and fencing of riparian zones.

Clarence Valley Council also funds similar work in the Nymboida River catchment.

Abstraction of raw water from the Orara River at Cochranes Pool is controlled by an on-line turbidity meter. Turbidity is a measure of the amount of particles in the water; the higher the turbidity reading, the dirtier the water and the harder to produce clean water for residents to drink. Turbidity is measured in Nephelometric Turbidity Units (NTUs) and the on-line turbidity meter is set to a cap of 2 NTU, which is only just noticeable to the average human eye. If this threshold is reached, the pumps are automatically switched off and no dirty water is added to Karangi Dam.

Nymboida River abstraction has similar water quality controls.

Adding air bubbles below the surface, or aerating the water, in Karangi Dam helps to:

• prevent stratification (formation of layers of water with little/no oxygen and differing temperatures and water quality);
• oxidise iron (ferrous to ferric) and manganese, which then settle out of the water, resulting in cleaner drinking water;
• prevent thermal inversion (sudden "turnover" of water layers) in autumn where water in an anaerobic condition (no oxygen) from the bottom of the Dam, called the hypolimnion, comes to the top of the Dam, which increases dissolved iron, manganese, colour and organic matter in the surface waters. This can cause dirty water and algal blooms and leads to customer complaints about dirty washing, discoloured water and taste and odour problems with the drinking water supply.

Raw water from the Orara River is known for being naturally "soft". Soft water has low levels of minerals/calcium carbonate and can be quite corrosive to a water supply system, especially to copper, iron and concrete fittings.

Coffs Harbour Water adds Lime to the water leaving Karangi Dam on the way to the Treatment Plant to increase the alkalinity, buffering the pH levels and reducing corrosion issues.

Nymboida River water is not as soft.

The $60 million Dissolved Air Flotation, Filtration Water Treatment Plant at Karangi was officially opened on 9 June 2009. The DAFF is not open to the public, but guided tours for school or community groups can be arranged by telephoning Council on (02) 6648 4000.

Location of Plant

The DAFF Plant is located on Upper Orara Road, Karangi. The location of the plant was chosen following an extensive selection process that covers social, environmental and financial issues. Some of the determining factors for the final site were that it needed:

• to be in close proximity to the existing pipeline from Karangi Dam to the Red Hill Balance Tanks;

• to have specific elevations in order to minimise energy usage;

• to allow as much building setback from boundaries in order to reduce the impact on neighbours;

• to require little or no native vegetation removal; and

• to have minimal environmental impact.

Design and Construction

Risk Assessment and a Hazard and Operability Study (HAZOP) was conducted during the design to ensure that the right process was selected for our particular circumstances.

In addition, a Hazard and Critical Point (HACCP) study of the whole system, from catchment to tap, was also be carried out to ensure that the correct process controls are in place and that preventative measures are operating effectively.

This is in line with the procedures outlined in the Australian Drinking Water Guidelines for new Water Filtration Plants.

Operational and Environmental Documents

Hazard and Operability Study (HAZOP) Report(PDF, 124KB)

Operational Environmental Management Plan(PDF, 12MB)

Operations Emergency Planning Management Plan(PDF, 1MB)

Operations Safety Management Plan(PDF, 13MB)

Compliance Tracking Program(PDF, 5MB)

Complaints or Inquiries

Complaints or inquiries regarding the plant can be directed to Coffs Harbour City Council via:

Telephone:02 6648 4000

Postal Address: Locked Bag 155, Coffs Harbour NSW 2450

Email: coffs.council@chcc.nsw.gov.au

Karangi WTP OEMP Complaints Register Karangi-WTP-OEMP-Complaints-Register.pdf(PDF, 29KB)

More Information

Water Treatment Plant Approval(PDF, 3MB)

Water Treatment Plant process description(PDF, 61KB)

Water Treatment Plant process diagram(PDF, 447KB)

At its 3 June 2004 meeting, Council voted to approach Mid North Coast Area Health Service and ask for the Minister to convene the Fluoridation of Public Water Supplies Advisory Committee as they felt they lacked the necessary expertise in the matter to make a judgement.

The Committee was convened and on 6 August 2004, the Director General, through the Government Gazette, issued a direction that Coffs Harbour fluoridate its water supply. Council was ordered to commence this by 30 November 2005 but an extension was obtained until the Water Treatment Plant was commissioned. 

The water supply was subsequently fluoridated on 11 June 2009. 

All properties connected to the town water supply served by the Karangi Water Treatment Plant, from Sawtell to Corindi and Coramba, will receive fluoridated water. Nana Glen, which is not on the Karangi Dam supply system, will not receive fluoridated water.

The target concentration is a level of 1mg/litre.

More Information

Mid North Coast Area Health Service Fluoride brochure(PDF, 120KB)

As anyone with a swimming pool will know, chlorine is only effective at disinfecting water for a certain period of time before chlorine levels fall and potentially harmful bacteria and bugs can start to grow in the water. The same rule applies for drinking water supplies, so the longer water has to travel from the Treatment Plant to your house, the less chlorine there will be in the water. This is carefully considered by water authorities and sometimes extra chlorine needs to be added to the water supply at appropriate points along the way to your house to "boost" the effectiveness of the disinfection and ensure the safety of the drinking water supply for all residents, regardless of where you live in the network.

These chlorine top-up points are called Chlorine Booster Plants and Coffs Harbour Water currently has one (1) Chlorine Booster Plant attached to the Emerald Reservoir, which boosts the chlorine levels for all residents living at Emerald Beach and northwards.