February 11, 2010

MAPLE REINDERS

Crews are working outside through the winter on the Picton, Ont. wastewater treatment plant.

FOCUS | Water & wastewater

Picton Wastewater Treatment Plant completed without public-private-partnership

IAN HARVEY

correspondent

It was a long time coming down the pipe, but the Picton Wastewater Treatment Plant is in the ground and on schedule for completion next fall.

Initial discussions to replace the existing 60-year-old treatment plant stretch back to 2004 and Prince Edward County had hoped to get it done as a public-private-partnership (P3) model but when the three bids came back in 2008, two were rejected because of high pricing and a third was disqualified.

Still, there was some pressure to get a new plant online since the existing facility was unable to keep up with population and industry growth in the area. There was also a Ministry of Environment directive to improve or replace the plant before any population increase swamped it.

The county went back to a traditional model and in June 2009 awarded the $24.7 million construction contract to Maple Reinders Constructors Ltd. All told, with legal costs, design, management and other allowances the project will ring in at about $29 million.

Some $10.3 million of the construction cost will be covered by the Canada-Ontario Municipal Rural Infrastructure Fund (COMRIF). Green municipal funding will be requested for two items: the turbine generator in the outfall and the effluent heat recover system totalling $439,950 while the remainder of the project will be financed through Infrastructure Ontario and repaid through user fees.

The new plant is being built at the same general location of the existing plant at Champlain Lookout but higher up on a hill because, as Maple Reinders project manager John Burke explains: “There just isn’t enough room physically there at the existing plant.”

Two massive force main pumps will lift the raw wastewater up the hill to the new facility which is rated at 6,000 cubic metres per day. It’s a more expensive solution but given the lack of space adjacent to the existing plant, unavoidable.

To offset those costs, one of the more unique features of the plant will be to convert part of the existing secondary clarifier chamber to house a generator turbine. It will transfer energy from the treated discharge into 17kW of energy at average day flow and approximately 27kW at maximum flow, which will be fed back into the pumps.

“We’ve got about 67 per cent of the concrete completed,” says Burke, noting work started in July and is on track for Oct. 30 completion. “And we’re working outside through the winter.”

The design calls for headworks, extended aeration tanks, secondary clarifiers, continuous backwash deep-bed sand filters and a UV disinfection unit for tertiary treatment. The generated sludge will be followed by aerobic digestion and mechanical dewatering, The facility also has the ability to take in raw sewage from hauler trucks.

Maple Reinders’ design incorporated extended aeration with digested sludge stored on site and periodically dewatered by an outside contractor who also will dispose of the dewatered sludge at an approved landfill.

This is a continuation of the existing practice and will allow the county to review and institute a sludge-management solution which may see more beneficial application of biosolids across the region.

The treatment technology itself consists of one mechanical screen with a standby manual screen to hand a maximum flow of 26,000 cubic metres/day. It in turn feeds one aeration and one secondary clarifier tank which can be put in or out of service as flow demands.

There are eight parallel cells of deep sand filters with two banks of UV lamps which will handle disinfection at much higher than the capacity rate.

Digested sludge will be stored in a sludge storage tank which will have about 63 days of storage while the digester tank, will have about 69 days of storage.

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