Drinking water treatment provides protection against waterborne pathogens and toxic chemicals; both of which cause adverse health effects.

Pathogens and Chemicals

Waterborne pathogens present the greatest risk to drinking water supplies. Waterborne pathogens include disease causing bacteria, viruses and protozoa that can cause illness. In some cases, these pathogens can lead to long-lasting or severe illnesses, complications, or even death. The sources of waterborne pathogens originate from a variety of activities: recreational, industrial, agricultural, natural (wildlife, wildfires, floods, etc.) and residential (sewage/stormwater systems, etc.). Both surface water and groundwater can be contaminated by pathogens.

In addition to pathogens, chemical and physical substances may also need to be reduced or eliminated through treatment. Some of these substances only cause aesthetic changes (e.g. taste, odor, colour, salinity and hardness) to the water quality. While cosmetic changes may not make people sick, they will make the water unappealing to your customers and may cause them to lose faith in the safeness of the water you are supplying.

Examples of chemicals which can cause undesirable aesthetic changes to the water quality but aren’t currently linked to adverse health effects are:  chloride, hardness (calcium carbonate), iron, sodium, sulphate, sulphide and zinc. Some chemicals, such as manganese and copper, are both an aesthetic concern and a health concern as they can cause detrimental health effects.

It should be noted that some chemical and physical parameters (such as colour, hardness, iron, manganese, total dissolved solids and turbidity) cause aesthetic and/or health effects but may also inhibit or interfere with the operation of treatment systems used to reduce or eliminate pathogens. 

Water Treatment Plans

The first step in your water treatment plan will be to figure out the Minimum Treatment Requirements you require for your water source and this should be done in consultation with your Drinking Water Officer (DWO).

 After confirming the minimum treatment requirements for your water source, you should choose a method of treatment that ensures clean, safe and reliable water for your consumers. Your chosen method of water treatment system will be either centralized or decentralized (i.e. Point of Entry or Point of Use)treatment.

The pros and cons of each type of system are discussed in the section Centralized vs Decentralized Water Treatment Systems. Regardless of which type of treatment system you choose, small water systems are required to ensure that their treatment system and components meet NSF standards.