From Disposal to a Resource – Shifting Directions in
Wastewater Management in the Capital Regional District

Victoria harbour

Membrane cassette being lowered in a bioreactor tank

Energy from Organic Solids The organic solids from wastewater treatment processes have long been recognized as a source of “green” energy, principally through the anaerobic digestion of the solids and the production of a biogas that can be used to generate on site electrical power. Current trends recognize that this biogas, in fact, has a higher value as a fuel. Technologies are now being developed to further refine this biogas to a quality that can be used to fuel vehicles or can be added to a natural gas grid. Biogas generation can be enhanced through the addition of other organic wastes such as food wastes from a source separated municipal solid waste program. Wastewater Heat Energy The typical average temperature of wastewater is about 15 degrees Celsius. Heat exchange technologies are rapidly advancing to cost effectively allow a portion of this heat to be extracted from the effluent prior to using the effluent for reuse or returning it to the environment. The heat recovered is typically used as a supplemental heat source in a centralized community heating system. Water Reuse Treated effluent can be used in a beneficial manner in a number of ways irrigation, industrial use, augmenting the flow in water courses, and non potable urban applications such as toilet flushing. There are two potential directions for provision of reuse water. The first is from a local wastewater treatment plant. The second is from an “internal” wastewater treatment plant in a building complex. In the latter, water recycling, often with the integration of rainwater capture, is used to reduce the overall potable water use in the complex and to reduce the amount of wastewater transported off site for treatment. Nutrient Recovery Wastewater contains phosphorus and nitrogen. While the traditional goal has been the reduction of these nutrients in the effluent dis charged to sensitive receiving environments, there is on going devel opment of technologies to recover these nutrients for their resource potential. Phosphorus can be recovered through a crystallization process, producing a high grade phosphate fertilizer. The majority of the nitrogen is contained in the ammonia in urine. Work is currently proceeding in Europe on the concept of urine separation at source in specially designed toilets. The “yellow” water can then be processed in a concentrated form, allowing the recovery of nitrogen for use as a fertilizer.

Over the last few decades, when the words “Victoria” and “sewage” are used together, it has usually been in reference to the debate on why one of Canada’s last major urban centres continues to discharge untreated wastewater into the marine environment. This debate has been heated and emotional – on both sides of the issue.

In 2006, the BC Capital Regional District (CRD) embarked on a program to develop a wastewater management strategy for the Victoria area. Associated Engineering, with CH2M Hill and Kerr Wood Leidal, developed a decision information report entitled, The Path Forward. The team is now working on further developing the CRD’s $1.2 billion Wastewater Management Program.

Project Manager Rick Corbett advises, “Ironically, the delay in moving to wastewater treatment may have been a blessing in disguise. As planning now moves ahead, the region has the opportunity to look at wastewater management from a different point of view – not as a waste to dispose of, but as a resource to utilize.”

Viewing Wastewater as a Resource

The change to viewing wastewater as a resource has three principle drivers – resource limitations, energy efficiency, and carbon footprint. While these are not new to the wastewater industry, they have taken on more significance in the past few years. These drivers create resource utilization or integration opportunities that fall into four main areas – energy from organic solids, wastewater heat energy, water reuse, and nutrient recovery (see sidebar).

Opportunities are significantly influenced by technology change in the wastewater industry. One of the major changes has been the development of membrane-based separation technology (see figure at right). In this approach, the traditional secondary clarifier, that separates the solids from the treated liquid portion by gravity, is replaced by a membrane process. This technology allows not only an increase in treatment performance, but also a much smaller footprint.

Setting the Direction

After a comprehensive triple bottom line analysis, the CRD decided to move towards a more “decentralized” approach that would see a larger number of wastewater treatment facilities throughout the region. Rick reports, “The direction adopted by the CRD for future wastewater management is a bold change from traditional thinking. It considers wastewater as a resource that can be integrated into urban resource management planning.” The CRD is planning for several decades into the future with the intent to establish the fundamental concept and facility siting decisions, so that, over time, wastewater management truly becomes part of the water and energy resources in the community.

Key Associated Engineering staff working on the project include Rick Corbett, Dr. Dave Forgie, Dr. Dean Shiskowski, and Michelle Maynard.