Epcor's Source-To-Tap Multi-Barrier Approach
1. Source Water Protection
EPCOR maintains a source water protection and monitoring program that identifies risks in the raw water supply (North Saskatchewan River). EPCOR's Source Water Protection Plan (SWPP) was developed in 2008 to help mitigate potential risks to Edmonton's source water supplies by understanding the pressures on the watershed. An update to the plan, including enhanced land use maps, water quality assessment, and incorporation of the Drinking Water Safety Plan Risk Assessment, was published in 2014. Key SWPP risks were reviewed in early 2016 as part of the Drinking Water Safety Plan review.
EPCOR Edmonton water treatment plants (Rossdale and E. L. Smith) use both conventional and direct filtration treatment methods. When raw water quality is good, typically in the fall and winter months, the plants will shift to direct filtration. This requires a substantially lower dose of alum and results in a significant reduction in the amount of waste discharged to the North Saskatchewan River. See details in the Reducing Environmental Impacts section of this report). This treatment process removes any bacteria, viruses, Giardia cysts and Cryptosporidium oocysts that might be present in the untreated river water as follows:
- EPCOR achieves at least 99.97% (3.5 log) physical removal credit for Giardia cysts and Cryptosporidium oocysts from the raw water during conventional operation by ensuring turbidity of the treated water produced by each filter in the water treatment plant is very low. Filter effluent turbidity is maintained at less than 0.1 NTU on individual filters at all times. The target is to be less than 0.08 NTU. This performance readily exceeds the AEP requirement of less than 0.3 NTU;
- During direct filtration operation, the individual filter effluent turbidity is still maintained at 0.1 NTU or less, but the credit for physical removal credit is reduced to 3.0 log removal. Although Giardia cyst and Cryptosporidium oocyst removal credit is slightly lower during direct filtration (99.9% versus 99.97% or 3 log versus 3.5 log), the concentration of these parasites in the river is much lower during this period;
- Ultraviolet light (UV) disinfection provides an additional 99.9% (3 log) inactivation credit of any Giardia cysts and Cryptosporidium oocysts remaining in the water after filtration;
- Primary disinfection provided by free chlorine provides an additional barrier against Giardia cysts, and is the primary barrier against bacteria and viruses;
- The overall removal credit of Cryptosporidium oocysts is 99.99997% (6.5 log) during conventional operation and 99.9999% (6.0 log) during direct filtration operation. This exceeds the minimum approval requirement of 99.9997% (5.5 log) that is based on the raw water quality and a health risk assessment. Giardia cyst removal is slightly higher due to chlorination; and
- Bacteria and viruses are inactivated by chlorination but are also removed to some extent by filtration. Additional inactivation is achieved by UV disinfection.
Ammonia is added to the water to form monochloramine which provides a lasting disinfectant residual through reservoir storage and throughout the distribution system within the City of Edmonton and the regional waterworks systems.
3. Distribution System
EPCOR ensures the safety of water in the distribution system by maintaining adequate supply pressure. There are continuous pressure monitors at several locations throughout the system. Ongoing maintenance programs that safeguard distribution system integrity and water quality include:
See details in the Industry Leadership section of this report.
A Cross Connection Control (CCC) program maintained by EPCOR provides an additional public health protection barrier. The goal of the CCC program is to minimize the potential for unintended backflow into the distribution system from moderate and severe risk customers in the multi-residential, commercial and industrial customer segments. This is done by ensuring Canadian Standards Association approved backflow prevention assemblies are in place for premise isolation and are tested annually as required by the National Plumbing Code of Canada, CSA B64.10 Standard, and the City of Edmonton Bylaw # 15816 EPCOR Water Services and Wastewater Treatment Bylaw. Every year, additional facilities are added to the program. In 2015, 697 facilities were added for a total of 9,560 at the end of the year. In 2014, EPCOR staff inspected 1,148 facilities and issued 13,006 notices to customers and testers for installation requirements, annual testing, test kit calibration and certification renewals. Overall compliance (tracking overdue tests and devices not installed), met the target of 70% for the year and was up 3% relative to 2014.
The Lead Response Program reduces the potential for exposure to lead in tap water for approximately 3,400 homes in mature neighbourhoods of the city that are supplied through lead service lines. See details on this program in the Lead Response Program section of this report.
To ensure safety of the drinking water up to customer taps, EPCOR monitors raw water entering the Rossdale and E. L. Smith Water Treatment Plants, as well as partially treated water and finished drinking water entering the distribution system. In addition, a routine monitoring program ensures water quality throughout the reservoirs and distribution system. The water is also tested in response to valid customer complaints and following system depressurizations due to main breaks or planned maintenance work.
EPCOR exceeds the minimum amount of monitoring and testing required by the regulator. In a city the size of Edmonton, Health Canada recommends bacteriological testing on 178 samples collected from the distribution system each month. On average, in 2015, 200 samples were collected monthly. In addition, EPCOR sent an average of 50 duplicate samples to the Provincial Laboratory for Public Health each month for an inter-lab quality check.
In 2015, the EPCOR Water Laboratory carried out approximately 127,000 tests on 7,800 samples of the treated water that entered the distribution system, water in the distribution system and field reservoirs, as well as raw water that entered the Rossdale and E. L. Smith Water Treatment plants, and partially treated water. EPCOR tested for 192 parameters for Edmonton water. A further 5,500 tests were conducted on 1,230 samples and included another 203 additional parameters by external commercial laboratories. These figures don't include testing conducted for special projects or initiatives such as EPCOR's home sniffing program or the lead response program. Details of all testing and monitoring done are published in monthly and annual Edmonton Waterworks reports that are posted on EPCOR's public website.
In addition to the laboratory testing, EPCOR also uses numerous on-line analyzers to continuously monitor critical treatment performance and water quality variables in the treatment plants, such as chlorine concentration and filtered water turbidity. Back-ups are provided for critical analyzers. There are 137 on-line analyzers at the E.L. Smith WTP and almost 80 at the Rossdale WTP with a quality assurance program in place to confirm they are reliable. Operators at the plants perform frequent bench tests to ensure the performance of these analyzers. In 2015, operators performed approximately 40,000 and 30,000 tests at the E. L. Smith and Rossdale water treatment plants respectively.