New Okanagan compost facility converts wastewater biosolids to Ogogrow™, a valuable soil amendment

The B.C. Okanagan cities of Kelowna and Vernon have long taken leadership roles in treating wastewater from their communities. Both cities operate advanced wastewater treatment plants incorporating biological nutrient removal (BNR) and create high quality effluent. The BNR process removes phosphorus, a nutrient found in wastewater that can lead to degradation of receiving waters.

The Kelowna Wastewater Treatment Plant discharges effluent to Okanagan Lake; the high quality of the effluent helps to preserve the quality of the lake. Effluent from the Vernon Water Reclamation Centre is stored during the winter and, from late April to early October, used for irrigating golf courses, orchards, a forestry centre, nursery, and agricultural land.

Typically, plants similar in size to Kelowna and Vernon use anaerobic (no oxygen) processes to stabilize their sludge (biosolids). However, BNR plants do not typically use anaerobic processes to stabilize sludge because bacteria used in wastewater treatment to remove phosphorus can release phosphorus under anaerobic conditions.

Since 1995, the City of Kelowna has composted sludge from their wastewater treatment plant. The Kelowna biosolids composting operation has been producing a product that meets British Columbia’s Organic Matter Recycling Regulation “Class A” requirements. Rich in nutrients such as phosphorus, this product is trademarked and marketed commercially as “Ogogrow”™, a soil conditioner, for landscaping, orchards, gardens, and potting soil.

Growing populations in both Kelowna and Vernon have driven the need to expand the cities’ sludge stabilization operations. The cities decided to collaborate on the design and construction of a larger composting facility to meet their joint needs.

Associated Engineering was selected to provide concept development, pre-design, process selection, design, equipment procurement, tendering, permit acquisition, construction contract management, and post construction services for the new composting facility.

The City of Kelowna decided to relocate the biosolids composting operation to a parcel of land located south of Vernon. The new biosolids composting facility had to be designed to accommodate current and projected biosolids production from the Kelowna, Vernon, Westbank, and District of Lake Country’s wastewater treatment plants, and from the Regional District of North Okanagan’s Septage Facilities. In addition, operational criteria for the new facility included the following:

• An aeration floor that could be easily loaded, unloaded, and maintained
• No obstructions around the compost piles for the front end loaders
• Automatic process control and data logging to meet regulatory requirements
• Readily expandable to keep up with on-going growth.

“The City of Kelowna had previously used the Aerated Static Pile (ASP) composting process successfully,” reports Senior Environmental Engineer, Dr. Dave Forgie. “So, the cities decided to base the new composting facility’s process on APS.” The advanced ASP process, provided by Engineered Compost Systems (ECS), has positive and negative aeration, enabling raw biosolids to be converted to Class A compost in 80 days, compared to the conventional ASP process that required a total of 120 days.

In addition to the composting area, the project also included an administration building with office, laboratory, and control room, sludge receiving and mix buildings, amendment and processed material storage areas, and leachate and surface runoff control and pumping. Stormwater and leachate from the facility is collected in a detention pond. Solids are removed and treated effluent is pumped to the City of Vernon’s reclaimed water reservoir. Recycled effluent is used as process water on site.

Project Engineer, Arash Masbough advises, “We decided to separate the project into three construction contracts and one equipment procurement contract. This allowed the design to advance with construction activities.” The project, from concept development to construction completion, was delivered in 18 months. The facility capital cost of $7.4 million was shared between Kelowna and Vernon, based on existing biosolids production from each city. Maple Reinders Inc. was the contractor for the main construction contract.

Dick Vest led design and construction administration for site works contracts. Gary Hussey provided project management for the main construction contract.

The cities of Kelowna and Vernon recently received the Union of British Columbia Municipalities (UBCM) Community Award of Excellence in the Leadership and Innovation (Large Community) category for this project.