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Environmental Monitoring

In addition to reducing the solids loading to the river, EPCOR has also been investigating the environmental impact of the solids that are discharged to the river.

  • In 2013 EPCOR began a program of river water sampling and testing to determine the extent of impact of solids discharges on the river immediately downstream of the discharge points. This sampling program continued through 2014 and 2015. In 2013 and 2014, this work involved collecting grab samples from the river or making measurements using hand-held probes from a boat during discharge events. In 2015, this work continued, but a datasonde was deployed directly in the river downstream of the discharge points to gather additional information. The datasonde is a device that allows essentially continuous in-stream monitoring of key water quality parameters like pH and turbidity.
  • So far, the results indicate that suspended solids, pH and total aluminum concentration increase within the near-field mixing zone in the immediate vicinity of the discharge points but return to normal levels within 2000 m downstream. The exception is dissolved aluminum where limited data has shown increased levels at the discharge point that still persist 2000 m downstream.

    Since 2010, EPCOR has been submitting quarterly composite samples of the solids discharges to a third party laboratory for determination of acute lethality using the 96 hour rainbow trout assay. None of the samples submitted have indicated acute toxicity to fish.

EPCOR will continue this monitoring program based on grab samples and datasonde information in 2016. The program will be expanded to include:

  • Development of a computer model to analyze the impact of total suspended solids and pH during discharges; and
  • Development of a monitoring program to assess the impact of the discharges on the benthic community (the benthic community are the organism live on the bottom of the river)


Reducing Environmental Impacts

The treatment of river water to produce clean, safe drinking water generates waste or “residual” streams. Some of these streams, such as the underflow from clarifiers and filter backwash, contain a lot of solid material that is a mixture of the suspended solid material removed from the river water and the solids produced by the addition of alum and, sometimes, powdered activated carbon. Some of these residual streams, such as filter backwash or treated water that does not meet the drinking water specification, also contain chlorine which can be toxic to fish. These waste streams have historically been released back to the river.

EPCOR has evaluated alternative strategies for managing these waste streams. Any successful strategy must balance reduction of environmental impact on the river against cost and our primary objective to meet drinking water treatment standards and to protect public health. Other environmental impacts, such as the energy footprint resulting from processing and transport of residuals to alternate disposal locations must also be factored into the equation.

Residuals Management Program

EPCOR has a program of continuous improvement in place to reduce the impact of solids present in the residual streams released into the North Saskatchewan River from its water treatment plants. Complete, year-round diversion of all solid residual streams from both Edmonton water treatment plants would require building very large, expensive treatment facilities at both water treatment plants and would involve trucking large volumes of solid material to landfills. This zero-discharge option was determined to be very costly and the net Environmental benefit was not clear. The volumetric flow and background solids concentration in the river fluctuates significantly during the year due to natural phenomena, which means that very large facilities would be required to manage the load during all seasons.

The EPCOR program has emphasized minimizing the loading of solids to the river during the fall and winter season, when river flow and the background suspended solid concentration are lowest and the relative impact of the solids discharged on the river quality is the greatest. This is achieved by reduction at source, that is by optimizing and minimizing the amount of alum added without compromising drinking water treatment. If less alum is added to the water for treatment, the amount of solid residuals produced and discharged to the river (especially the amount of chemical residuals) is reduced.

Reduction of Water Treatment Plants Winter Solids Residual Production

Since 2009, the EPCOR Rossdale and E. L. Smith Water Treatment Plants have converted to the direct filtration mode of operation during the winter months to reduce the amount of residuals released to the river. The switch from Conventional mode to direct filtration mode involves reducing alum dosing during treatment by up to 80%. This reduces the total mass of solids residuals produced during treatment that has to be discharged to the river by up to 50%. EPCOR's original plan was to operate in direct filtration mode during the months of November through February, and to build facilities to divert the remaining solids produced during these months to on-site solids treatment facilities for eventual landfill disposal (E.L. Smith plant) or sewer disposal (Rossdale plant).

While direct filtration operation has been successful in terms of maintaining excellent treated water quality and substantially reducing residuals discharged to the river, there have been some operational challenges. After seven seasons of direct filtration operation, EPCOR has learned that the key variable in determining operational success is the color in the raw water. During the first two seasons (2009-2010, 2010-2011) the colour was relatively low and stable. However, in subsequent years (2010-2013), the color was higher and more variable. This trend of higher colour, especially in the fall, has continued in subsequent years (2014-15). EPCOR determined that direct filtration can be operated successfully under the higher and more variable raw water colour conditions with appropriate alum dosing and by using all of the clarifiers at the plant for treatment. Unfortunately, direct filtration operation conflicted with the proposed design of the on-site solids treatment facilities wherein some of the unused clarifiers would have been used to thicken solids prior to removal and disposal.

With approval from AEP (Sept 2013), EPCOR modified its residual reduction plan to focus on extending the operation of direct filtration into the fall (September to October) and spring season (March), when the water quality of the river is often amenable to direct filtration treatment. In addition, EPCOR has been further reducing residuals production by optimizing and reducing alum and powdered activated carbon treatment in conventional mode operation during other times of the year.

The table below summarizes the actual solids discharged to the river from the two water treatment plants by application of this strategy over the last four years (2012-2015). In a given year, the actual solid loading to the river depends on the raw water conditions for that year and will, therefore, vary. To determine the effectiveness of the solids reduction strategy against this background variation, EPCOR compares the actual solids discharged from the two treatment plants to the amount that would have been discharged using the 2005-2010 conventional treatment strategy.

For example, in 2015 the actual amount of solids residual produced and discharged was 470 tonnes during the winter Direct Filtration period (Jan-Feb, Nov-Dec). If the plant had been operated in conventional mode with the same raw water conditions, 825 tonnes of residual solid would have been produced and discharged. Direct filtration operattion, therefore, achieved a 43 per cent reduction in solids reduced and discharged during this period. During the extended direct filtration operation period of late winter (March) and fall (Sept-Oct), 654 tonnes were discharged compared to 936 tonnes that would have been discharged by conventional operation (a 30 per cent decrease during this period).

Solid Residuals Discharged to the River From the Edmonton Water Treatment Plants for the Last Four Years (Tonnes)

Operating Mode Season 2012 ​ ​ 2013 ​ ​
Baseline+ Actual Decrease Baseline+ Actual Decrease
DF Jan-Feb
Nov-Dec
1,070 489 55% 1,060 523 51%
Extended DF* Mar
Sep-Oct
898 394 44% 935 586 37%
Chemical Optimization Apr-Aug 16,600 15,430 7% 18,950 17,840 6%
Total Jan-Dec 18,600 16,423 12% 20,940 18,940 10%
Operating Mode Season 2014 ​ ​ 2015 ​ ​
Baseline+ Actual Decrease Baseline+ Actual Decrease
DF Jan-Feb
Nov-Dec
1,170 581 50% 825 470 43%
Extended DF* Mar
Sep-Oct
936 654 30% Conventional Mode Operation ​ ​
Chemical Optimization Apr-Aug 10,190 9,190 10% 3,690 3,780 -3%
Total Jan-Dec 12,290 10,420 15% 4,500 4,240 6%

 

* Direct Filtration
+ Baseline load is calculated using 2005-2010 conventional treatment strategy and actual raw water conditions in 2012, 2013, 2014 and 2015

The reduction in solids discharged over the entire year has varied from year to year but has been modest (6 % to 15%). The reductions in the winter and fall seasons, when the flow and background solids loading in the river is lower, and the relative environmental impact larger, have been far more significant. During the winter season, under ice cover (Nov-Feb), reductions in loading ranging from 43% to 55% have been achieved. Reductions in the extended direct filtration period (Mar, Sept-Oct) have varied from none in 2015 to 44% in 2012.

The overall performance of direction filtration is variable and highly dependent on water quality conditions in the river in the fall and winter seasons. The extended direct filtration season was shorter in 2013 and 2014 due to poorer raw water quality conditions, late summer water demand and challenges with plant equipment (2014). This resulted in lower decreases in 2013 and 2014 relative to 2012. In 2015, higher river pH in the fall made direct filtration operation very difficult and the water treatment plants were not able to run in full direction filtration mode until November. Also, spring run-off in the river started relatively early in 2015 and it was not possible to operate in direct filtration in March. As a result, there was essentially no extended direct filtration season in 2015. During the chemical optimization period (Apr–Aug), the amount of solids discharged was actually greater then baseline condition. Despite all this, the actual amount of solids discharged to the river in 2015 was by far the lowest of the four years at 4,240 tonnes. This largely reflects the natural conditions in the river during the year where the turbidity was unusually low.

 

Impacts of Residuals Management Strategy on Drinking Water Quality

One of the primary objectives of the residuals management strategy is to achieve environmental benefit (reducing solids loading to the river), without compromising the health and safety of drinking water. Direction filtration has a slight impact on a few quality variables including turbidity, total aluminium, total organic carbon and disinfection by-products. However, the impact is minor these parameters remain well within health-based guideline levels or approval limits. As in earlier years, direct filtration operation in 2015 correlated with an increase in the number of detects of very low levels ofCryptosporidium oocysts in the treated drinking water at the Rossdale and E. L. Smith water treatment plants. Cryptosporidium oocysts were detected in three weekly samples (one from the Rossdale plant and one from the E. L. Smith plant) during fall direct filtration operation. Using Quantitative Microbial Risk Analysis, the risk associated with this level of parasites in the drinking water was determined to be well below negligible risk levels established by Health Canada and the World Health Organization.

Continuous Improvement Initiatives

In the spirit of continuous improvement, EPCOR has been investigating strategies to further reduce alum dosing and, thereby, reduce solids loading. These efforts have focused mainly on improving and optimizing direct filtration operation. In 2015 these included:

  • Zeta Potential: EPCOR has investigated the use of Zeta Potential (ZP) potential measurements as a way of better understanding and optimizing direct filtration operation. ZP is a measure of the charge on the surface of very small particles in water. In 2015, we used a ZP analyzer to measure particle surface charge at various points in the water treatment process. We have found that ZP potential is closely related to filtration polymer dose and this provides some insights into using filter polymer dose to improve direct filtration operation;
  • Improving Cryptosporidium Oocyst Removal: In 2014 EPCOR initiated a research project led by the University of Alberta to study the physical removal of Cryptosporidium oocysts during direct filtration operation. The study involves a combination of laboratory bench experiments and pilot-plant challenge experiments. The objective is to determine the mechanisms and variables affecting oocyst removal during filter operation. This will lead to strategies to further optimize oocyst removal during direct filtration. The project continued in 2015 and received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) for two years. In 2015, we were able to complete preliminary pilot plant experiments using glycopolymer-coated microspheres as surrogates for Cryptosporidium oocysts to assess the effect of filter polymer dose and filtration on the effectiveness of direct filtration. These experiments will continue in 2016;
  • Raw Water pH Adjustment: One of the challenges with direct filtration in the early fall months is the naturally high pH of the river water. In September and October, raw water pH is around 8.5 which is higher than optimal for direction filtration. In 2015, a trial to test the effect of lowering pH by addition of sulfuric acid to the raw water was carried out at the E. L. Smith water treatment plant. Although there were technical challenges with the trial, the results were sufficiently promising to plan further trials in 2016; and 
  • Using Deep Bed Filters: In 2013-2014, a comprehensive pilot study was completed to assess the feasibility of deep bed filters to provide additional plant capacity and facilitate direct filtration operation. An engineering analysis was also completed to determine the technical and economic feasibility of converting some of the filters at the E. L. Smith Water Treatment Plant to deep bed operation. In 2015, a proposal for a capital project to convert 12 of 18 filters at the E. L. Smith plant to direct filtration mode was developed. The proposal will be submitted to City of Edmonton in 2016 for approval as part of the 2017-2021 Performance Based Regulation rate application.

The Importance Of Dechlorination

Drinking water contains residual chlorine, added at the treatment plants to disinfect the water. While it is important to ensure a minimum residual in the water delivered to all customers for protection of public health, the chlorine residual can be toxic to fish as it damages their gills. EPCOR has committed to eliminating all discharges of chlorinated water from its facilities. This includes routine discharges of chlorinated water from the E. L. Smith and Rossdale Water Treatment Plants arising from filter backwashes, filter-to-waste, release of other water that does not meet drinking water specifications, and less frequent discharges of chlorinated water arising from activities at field reservoirs and in the water distribution system.

Dechlorination At The Water Treatment Plants And Field Reservoirs

Bisulfite dechlorination systems have been in place and operating the E. L. Smith and Rossdale drinking water treatment plants since 2009 and 2012, respectively, and meeting AEP approval limits since 2010 and 2012. These systems remove chlorine from chlorinated water streams including filter backwash, filter-to-waste and plant by-by passes before the water is returned to the river. As well, procedures are in place to ensure that all planned discharges of chlorinated drinking water from the field reservoirs are dechlorinated prior to release. In 2015, these systems and procedures functioned properly and there were no releases of chlorinated water to the river due to failure of these systems or procedures.

There was one reportable incident at the E. L Smith water treatment plant when chlorine was detected in the water released from one of the clarifiers. Normally, the water in the clarifier does not contain any chlorine, but 0.2 ppm chlorine was measured in a sample of clarifier blowdown during a routine fish toxicity test. An investigation showed that the presence of chlorine was due to a leaking valve on a cross connection between the clarifier blowdown line and a chlorinated service water. As a follow-up, EPCOR is carrying out a survey to identify all potential cross connections between chlorinated water and non-chlorinated wastewater streams at each of the treatment plants.

Dechlorination of Water Released to the Environment in the Distribution System

EPCOR has procedures in place to dechlorinate all drinking water released into the environment. This includes both planned releases (i.e. flushing and draining of pipes for maintenance) and unplanned releases (i.e. water main breaks and other emergency events). While it may be difficult to ensure 100 per cent dechlorination of all releases (especially those that occur due to unplanned events like main breaks), the procedures will ensure the majority of the water released from the distribution system is dechlorinated and that potential environmental impacts are mitigated.

In 2015, there were two releases of chlorinated water from the distribution to water courses reported during the year. Both were investigated and corrective actions put into place to prevent reoccurrence. These were:

  • An EPCOR contractor left drinking water running from a hose overnight to prevent freezing. The hose was discharging to a catch basin that contained bisulfite pucks for dechlorination, but the hose accidently moved during the night resulting in a release of chlorinated water chlorine to a combined sewer. The contractor revised their dechlorination procedures to better secure hoses.
  • About 300 m³ chlorinated drinking water was released to Wedgewood creek when a contractor doing work in the area damaged an old, unused service line and valve. A new procedure to properly identify and abandon these old service lines was developed.

EPCOR is committed to eliminating these kinds of occurrences through root cause investigations and implementation of corrective actions.