Treatment options: small drinking water systems

The type and quality of source water used and the design of your drinking water system determines the treatment required

There are many ways to treat source water in your small drinking water system. Only choose products which are certified and meet industry standards.

Types of source water

In Ontario, most small drinking water system operators get their water from two sources: groundwater or surface water. The type and quality of source water used, and the design of your system, usually determines the treatment required.

Secure groundwater

Treatment may not be required for water that is obtained from a secure, well-constructed and maintained groundwater source, such as a drilled well.

Non-secure groundwater

Treatment is required if the source water supplying your small drinking water system is a non-secure groundwater source. If the construction or design of your well allows contamination by surface water, then you may be required to provide filtration and disinfection to the well water.

Surface water

Treatment must be provided if the source water supplying your small drinking water system is from a surface water source. For surface water, you will be required to provide mechanical or chemical-assisted filtration and primary disinfection.

If your system has a distribution system, you may be required to provide secondary disinfection.

What treatment device would work best for your small drinking water system?

There are two types of drinking water treatment devices available: disinfecting devices that are used to deactivate or remove harmful micro-organisms, and water conditioning devices that are used to control or remove chemical, taste and odour problems.

Before you choose a device, it is important to have your water tested and speak with a water treatment specialist. You can also speak with a public health inspector from Public Health Sudbury & Districts by phoning 705.522.9200 or calling toll-free at 1.866.522.9200. Look for a device that has been certified by an accredited body. They provide standards that have been designed to safeguard drinking water by helping to ensure the material safety and performance of products that come into contact with drinking water.

The two main processes used in treating your small drinking water system supply are filtration and disinfection.

Filtration

• This process uses a filter to remove particles and reduce the number of parasites from the source water. Filtration is required for all surface water systems and for non-secure groundwater systems that are vulnerable to surface water contamination.
• Filtration is the simplest method for removing suspended particles and turbidity from a drinking water supply to allow for successful disinfection. Filtration methods include slow and rapid sand filtration, diatomaceous earth filtration, direct filtration, membrane filtration and cartridge filtration.

Disinfection

• This process reduces or eliminates the number of harmful micro-organisms in water. Disinfection is required for all surface water systems and for non-secure groundwater systems that are vulnerable to surface water contamination.
• Disinfection can be achieved with chemical or physical disinfectants such as chlorine, chlorine dioxide, ozone and ultraviolet (UV) light. The most common disinfectants used to treat water for small drinking water systems are chlorine and UV light.

Depending on where the treatment is installed in your small drinking water system, it may be considered a point-of-entry treatment system or a point-of-use treatment system.

Point-of-entry treatment system

• This device is installed where the water enters the building. All water used within the building will be treated, including water used for bathing and laundry.
• Point-of-entry systems tend to be larger and more expensive than alternative systems.

Point-of-use treatment system

• This device is installed at the tap where the water is being used for drinking or cooking. Only water used from this tap is treated.
• Water from all other taps will be untreated and should not be used for drinking purposes.

Disinfection units and chemicals

Ultraviolet (UV) Light

• Ultraviolet treatment is the disinfection process of passing water by a UV light source. The UV light is immersed in the water in a protective transparent sleeve and emits UV radiaition that destroy harmful micro-organisms. UV devices are required to have an alarm or automatic shut-off to alert when there is a failure.
• The UV device works by emitting similar UV radiation to the sun. This radiation alters the genetic material of viruses, bacteria, moulds or parasites so they cannot reproduce and are considered inactivated. UV treatment does not remove dirt particles, metals such as lead or iron, or hard minerals such as calcium. Other devices are required to remove particles, metals and minerals.
• UV devices are not effective at treating water that is highly contaminated, heavily cloudy or turbid, or high in iron. To increase the effectiveness of the UV device, the water may have to be pre-treated.
• UV lamps should be checked and cleaned periodically, or replaced when necessary in accordance with the manufacturer’s instructions.

Chlorinators

• Chlorination devices provide disinfection to a system by continuously adding a chlorinated product to all water that is drawn from the system.
• Treatment is provided by thoroughly mixing all water in the system with a specific amount (concentration) of chlorine for a sufficient (contact) time period.
• The time that is required for disinfection depends on the concentration of the chlorine solution, the quality of the water entering the system, the pH and temperature of the water and the discharge rate of the pump.
• Frequent monitoring of the water chemistry is necessary to ensure that adequate disinfection is being continuously provided.
• Chlorine provides a disinfection residual, continuous disinfection and allows for easy monitoring.

Ozonators

• These devices use ozone to inactivate micro-organisms and provide some residual protection.
• The device is sealed and requires moderate amounts of electricity to produce ozone.
• These devices are easy to install and maintain, but can be expensive.

Treatment devices for chemical, taste and odour removal

The appearance, taste and smell of drinking water are usually more obvious to the consumer than the bacterial quality. Chemicals such as iron, manganese, sulphide and calcium hardness can cause odour and taste problems.

There are several devices available to remedy these problems; however, these units deal mainly with poor odour and taste problems and do not provide disinfection. If not used correctly, they may even increase existing problems with bacterial contamination.

 Activated carbon or charcoal filters

• These devices are used to remove chlorine, odour and taste caused by organic materials. The efficiency of the device depends on the quality of the source water your system uses.
• They are easy to install and require no power to operate. These are not disinfection devices and should only be used on water that is already disinfected and safe to drink.
• If using these devices for water conditioning, you should know that the bacterial levels in your drinking water may increase because of the dirt and organic material that are trapped in the filters.

 Reverse osmosis

• This device conditions your water supply by forcing water through a filtering membrane to remove most microbiological (bacteria, viruses and protozoa) and chemical (metals and mineral salts) parameters.
• It is easy to install and maintain, however the water must be pre-treated to increase the life of the membrane filters that may clog or rupture if the water is of poor quality.

Water softener

• This process is used to remove inorganic contaminants that are inadequately removed by filtration or sedimentation. It is also used to treat hard water and can be used to remove arsenic, chromium, excess fluoride, nitrates, radium and uranium.
• Softened water is not recommended for drinking because increased sodium content can pose health risks if exceeding the upper limit of 20 mg/L.
• This process may use and discharge significant amounts of salt; however, sodium-free softeners are available.

Get advice from a water treatment specialist to choose the best ways to make your drinking water safe.

For the best treatment, buy only devices that have been certified and meet industry standards.

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This item was last modified on August 27, 2018