Guidance For Providing Safe Drinking Water in Areas of Federal Jurisdiction - Version 1

Part 2 - Application of The Federal Framework

5.0 Treatment System Design and Maintenance

5.1 Design of drinking water treatment systems

Treatment systems should be designed based on the site-specific raw water quality and quantity and should take into account seasonal variations. The characteristics of the treated water will be further affected by the treatment processes used, the treatment components, equipment design, chemicals used, treatment efficiency, and monitoring procedures, etc.

Because of the complexity of assessing the level of risk associated with drinking water hazards, as well as the need to properly design a water treatment system, the evaluation of the source water and the design and construction of the treatment facility must be performed by qualified authorities (e.g., registered professional engineers).

5.2 Continuous monitoring and automated systems

When considering the construction of a new treatment plant or upgrading an existing plant, it is recommended that the design include an automated, continuous monitoring system that allows an operator to control and monitor processes from a central location. When a plant does not have an operator present 24 hours per day, 7 days per week, such systems are capable of calling a designated location if there is a process failure during silent hours.⁽³⁸⁾ In addition, the use of Supervisory Control And Data Acquisition (SCADA) technology or similar products allows the operator to make operational adjustments from a remote location. These products should be secure from accidental or deliberate interference.

Automation is advantageous in situations where an operator's duties are shared between different systems or different roles (i.e., not just drinking water) and when it is not possible for the operator to physically check equipment every day (including weekends). It can be used for any size system, however, the utility of automation in a very small system would have to be assessed in terms of the costs and benefits related to the level of risk the water system represents to the users. The costs associated with the operator's time need to be assessed against the cost of the equipment suggested.

For very small systems, less sophisticated automated notification systems can be used to communicate alarms to an offsite location, such as a pager or phone, when a water quality parameter is out of compliance. As a general rule, only technology that is realistic should be installed.

5.3 Surface water intakes

A surface water source will have an intake structure for drawing water into a water treatment plant. The main purpose of the intake structure is to draw in water while preventing leaves and other debris from clogging or damaging pumps, pipes and other pieces of equipment in the treatment plant.

The location of the water intake structure can greatly affect the quality of the water withdrawn. Ideally the intake would be located upstream of any potential source of contamination or, if that is not possible, sufficiently downstream to minimize impact.⁽¹⁴⁾ It should also be located deep enough under water to ensure that the water around it does not freeze in the winter, thereby ensuring water can be drawn year round.

Proper design, maintenance and operation are essential to prevent partial or complete shut-down of the entire drinking water system. Screens should be cleaned regularly to prevent blockage. Each spring, the lake or river intake pipe and screen should be inspected by divers to ensure no damage has occurred over the winter.^{5 (39)}

5.4 Treatment options

The treatment process selected should address all potential hazards and the level of risk associated with those hazards identified in the source assessment.⁽¹⁷⁾ Only expert qualified professionals should be hired to design drinking water treatment systems.

Minimum treatment of all supplies derived from surface water sources and groundwater under the influence of surface waters should include sedimentation, flocculation, coagulation, filtration, and disinfection, or equivalent technologies.⁽¹⁸⁾

Technical standards, benchmarks and targets for drinking water quality are given in Section 4. Monitoring requirements are discussed in Section 7.3.

Operator training and certification are discussed in Section 7.2. For detailed information on water treatment technologies, see references 33 and 38.

⁵ Guidelines on screen designs to prevent fish entrainment are available from Fisheries and Oceans Canada. Intake construction should also be reviewed under the Navigable Water Act in consultation with the Coast Guard.⁽¹⁴⁾