After learning about higher-than-expected turbidity levels in Holland Lake in 2013, Ladysmith council is going to look into water filtration.
During an April 17 special council meeting, council directed staff to pursue, in principle, water filtration as the method of secondary water treatment for the Town of Ladysmith and waive the purchasing policy for a Water Filtration Study.
Council had received a preliminary presentation about the 2013 Annual Water Report a week earlier and requested that it be brought forward to April 17.
The Town’s water system is operated and maintained in accordance with a permit issued through Island Health (VIHA), and the publication of this report is one of the permit requirements.
The report confirms that the Town’s water system generally complies with the intent of its permit, aside from the question of water treatment, John Manson, the director of infrastructure services, explained in his report to council.
A few years ago, VIHA published new guidelines for the treatment of surface water supplies for domestic consumption, and the filtration of surface water is required as one of the treatment steps to meet biological/pathogenic organism reductions in the guidelines, explained Manson.
One of those water treatment requirements is 1 NTU (Nephelometric Turbidity Units) turbidity maximum in finished water. High turbidity, which results in cloudy water, can interfere with the disinfection of drinking water and can be a source of disease-causing micro-organisms.
The Town has been actively upgrading the treatment and management of its water supplies to meet the requirements, most recently upgrading the old chlorination facility.
Manson explained to council that the Town has been closely monitoring water quality parameters, such as source water turbidity, to determine if the Town could continue to pursue a filtration deferral. Turbidity samples have been compiled for Stocking Lake, Holland Creek at Chicken Ladder, and Holland Lake.
According to Manson, Stocking Lake consistently delivers high-quality water year-round, “significantly” less than 1 NTU, the maximum allowable turbidity for filtration deferral.
In 2013, Holland Creek (Chicken Ladder) was more than 1 NTU for 13 days, which is less than the maximum 18 days permitted for filtration deferral.
The Town will typically draw its water from Holland Creek, except in winter months when Stocking Lake is overflowing. The Town will switch back to Stocking Lake during high-turbidity “events,” returning to Holland Creek after the water has returned to less than 1 NTU, explained Manson.
“To date, the Town has been able to successfully keep our blended water below the 1 NTU level for essentially all of the year in 2013,” he said.
Part of the Town’s strategy moving forward was to provide a direct connection from Stocking Lake to Holland Lake so Holland Lake water, expected to be higher quality, could also be accessed when Holland Creek was not suitable, he noted.
But Manson and his staff were surprised when 2013 turbidity readings taken from Holland Lake showed that the lake’s water exceeded the 1 NTU level for about 90 days in 2013, mostly during the winter months when the lake was frozen over.
Up to this point, the Town has been using a filtration deferral approach to water quality through the selective use of alternate supply sources to meet VIHA’s Drinking Water Treatment for Surface Water Supplies Policy, but these higher turbidity readings show that it is not likely the Town could obtain a filtration deferral should the Town wish to use Holland Lake water directly 100 per cent of the time.
The Town’s current direction for constructing a secondary disinfection system for the water supply is to construct a UV or Ozone system in lieu of filtration, but Manson is now recommending the Town look at a filtration system.
Manson advised council that, to move forward with filtration, a pilot project will be required to provide actual test data on water sources, and this will form the basis of a full-scale design.
Staff has tentatively placed this project in the Capital Plan for 2014 at a cost of $165,000. Manson says the numbers are very broad at this point.
“There’s no point trying to guess [the cost] right now,” he said. “We need to get the pilot project underway and do what the consultants tell us to find out the cost.”
The pilot project would look at two or three options for filtration (such as sand and membrane filtration) and run water through the different technologies, then come up with costs, Manson told council.
Coun. Bill Drysdale spoke in favour of going toward filtration.
“I think it’s good money after bad if we try to go with UV and then are directed to filtration later,” he said. “I think we should support the pilot project and get an idea of costs to our citizens.”