Colwood and Langford Wastewater Treatment
Aqua-Tex and a team of engineering and regulatory specialists have been working with the City of Colwood for the past 3 years to develop a plan for advanced wastewater treatment. The plan would see sewage from Colwood and Langford treated using a membrane bioreactor (MBR) at a single plant in Colwood. Water would be treated to near-drinking water quality and suitable for reuse purposes including groundwater recharge, irrigation, toilet flushing and indirect stream augmentation. As aquatic ecologists who have worked on southern Vancouver Island for decades, we have witnessed first hand the loss of summer stream flows and the subsequent loss of habitat for salmon and the species that depend upon them. We know water to be a vital resource, even on our "wet" coast.
The treatment plant would be located adjacent to the existing sewer trunk and avoid costly conveyancing. Colwood owns a suitable site and private lands have also been offered. Biosolids would be removed in two phases: initial screening would remove the bulk of the solids at the beginning of the process and pelletize them so they could be used as energy feedstock. This would be followed by membrane treatment and advanced oxidation, and remaining solids from that process would be dewatered and either trucked to a regional facility or could be used to generate energy on site using a thermal destruction process (preferred option). Taken together, the wastewater treatment and biosolids management would remove all microplastics, pathogens, and personal care and pharmaceutical products to the highest degree possible with current technology.
Colwood and Langford sit on extensive sands and gravels. It is our team's professional opinion that these gravels are suitable for discharge of the highly treated water to ground. This would recharge the aquifer and indirectly recharge local streams. The first phase of an Environmental Impact Statement has been completed and is favourable, but the second (field) component must be completed before this disposal option can be presented to the Ministry of Environment for review. Ground disposal is standard practice throughout much of North America. If ground disposal is not possible for Colwood/Langford, then an ocean outfall could be used. The budget has allowance for an ocean outfall if it was required in place of ground disposal.
The cost of this option is considerably cheaper for Colwood and Langford residents than the centralized McLoughlin option. The annual per door cost for Colwood residents is approximately $40 and the cost to Langford residents is about $60 assuming 2/3 senior government funding. This includes annual operating costs. If full on-site biosolids management were added (final step) it would add approximately $10/house/year to the cost.
The initial treatment plant would accommodate the existing wastewater flows plus 25% for growth (total 10 ML/D), but the building would accommodate greater capacity. As the community grows, modest development cost charges would finance additional capacity in the plant. This fiscally responsible "pay-as-you-go" approach does not burden taxpayers with expenses that are not needed and benefits from declining costs as membrane technology continues to become cheaper. New users pay for new service, but existing users do not pay for expansion.
The design and costing has been peer reviewed by Ed Clerico, P.E. and Bob Schwartz, P.E. (ret'd) of Natural Systems Utilities in New Jersey. They agree that the chosen technologies are appropriate and that the costs are in-line with their experience and published values. NSU has designed dozens of wastewater treatment systems and currently operates 210 systems across 10 states.
The Core Area Wastewater Treatment Project Board (CAWTPB) has recommended $2 M to complete the Environmental Impact Statement and other technical studies before a final decision will be made on a Colwood plant.
The Colwood design team includes:
Patrick Lucey, R.P. Bio, C.Biol., MRSB, Aqua-Tex
Cori Barraclough, R.P. Bio., C.Biol., MRSB, PMP, Aqua-Tex
Bruce Jank, Ph.D., P.Eng., Canadian Clean Water Technologies
Les McDonald, R.P. Bio., Spirogyra Scientific Consulting
Michael Payne, P.Eng., Payne Engineering Geology
Ian Ralston, Eng. L., TRAX Developments Ltd.
Dragan Rokic, P.Eng. LEED AP, MCPM, PMP, GreatPacific Engineering Ltd.
Jason Clarke, P.Eng., GreatPacific Engineering Ltd.
Jon O'Riordan, Ph.D.