Kimberley Wastewater Treatment Plant Odours Explained


We appreciate all of the comments concerning the odours at the Kimberley Wastewater Treatment Plant. While it’s not uncommon to smell foul odours from wastewater treatment plants (WWTP) in general, it is certainly unpleasant. The offensive odours are caused by anaerobic decomposition of organic compounds (bio-solids). A natural by-product of anaerobic digestion is hydrogen sulfide (H2S), which gives off the strong odour. Odours vary from season to season and day to day as higher temperatures elevate the smell and wind-direction blows it around.

Is it dangerous or unhealthy?

While offensive, there is no threat to public health from the smell at the WWTP.

Why do odours seem worse in the spring and summer?

  • Bio-solids removal must be done in the spring and summer months and is essential to ensuring space for annual bio-solids collection.
  • The process of bio-solids removal includes using 3 drying beds to empty large sludge holding basins. Two of these basins hold sludge for 3-5 years. This spring and summer, the second and largest sludge holding basin is being emptied.
  • Once dried to between 4% and 20% moisture content, the bio-solids are then removed from the site and trucked to the Central Landfill. This step can also create increased odours.
  • Weather patterns and wind direction can also dramatically increase odours in certain neighbourhoods.

Why does it seem to be getting worse?

  • Operational struggles due to the age of the existing WWTP and its components have made keeping up with bio-solids removal difficult, resulting in a backlog of bio-solids to be removed.
  • The ever-increasing population within Kimberley is contributing to increasing bio-solids, requiring them to be handled and removed in larger volumes annually.
  • The volume and composition of the sewer influent to the WWTP is changing on an ongoing basis making operation of aging WWTP technology difficult.
  • Various chemicals and other materials are flushed or drained into the wastewater treatment infrastructure. These chemicals and/or materials are reducing the WWTPs ability to break down bio-solids efficiently. The public is asked to ensure they are disposing of these materials properly and not flushing them down the toilet or releasing them down their drains. These materials include hot tub water, car and carpet wash chemicals, fats, oils, greases, wipes and feminine hygiene products.  If you are unsure what to do with these materials, please call City Operations at 250-427-9660.

What else is contributing to the odour?

  • The WWTP operations do not currently include odour control of any form. Modern facilities have extensive odour control systems.
  • At Kimberley’s WWTP, aeration tanks and sludge aeration basins require constant mixing. These are open to the atmosphere and are running 24/7.
  • In the spring and summer months drying beds are used to dry the bio-solids removed from the sludge storage basins. This process is what typically triggers the majority of the odour complaints
  • as it is evaporation of the odour laden liquid from the bio-solids that causes the increase in plant odours. This is a required operational process to enable the bio-solids to be dry enough to be legally hauled to landfill.
  • Processed bio-solids settle in uncovered, open air lagoons, in preparation for removal to the landfill which also causes odours.
  • All of the above operations involve or result in evaporation of process liquid and the release of the odours those evaporated liquids contain.
  • The regional landfill is only permitted to receive the bio-solids once they have dried to 4% to 20% moisture content. They cannot receive wet bio-solids.
  • Ministry of Environment (MOE) regulations are restrictive and do not allow for fast bulk removal of bio-solids as the rapid removal of the solids will result in the remaining liquids entering the WWTP process, upsetting the plant operation and resulting in non-compliant effluent discharge to the St. Mary River triggering environmental fines to the City.
  • The need to remove a considerable backlog of bio-solids has resulted in the Operators at the WWTP having to handle more bio-solids than what would be typical, thus creating significantly more odours.
  • To increase the volume of bio-solids able to be dried in one spring/summer season, the Operators are performing operations to enhance the drying process, unfortunately enhancing the odours created at the same time.
  • Odour issues at the WWTP have been ongoing for many years as noted in a report from 1999 to review odour issues at the WWTP. Unfortunately, no long-term solutions were actioned at that time.

What is being done to reduce odours?

  • City staff is working hard to remove accumulated bio-solids from sludge storage basins. In 2020 bio-solids removal was performed on the smaller basin and this year the same process is being performed on the second even larger basin in an attempt to gain ground. Although this will not be helpful for odour reduction in 2021, in fact it will likely increase it. Thankfully, it will help in future years as the volume of bio-solids will be at a more manageable level.
  • Staff are also working diligently to keep the WWTP compliant with all regulations of the Ministry of Environment (MOE), Municipal Waste Regulation (MWR) and Municipal Liquid Waste Authorizations (MLWA).
  • City Council has approved roughly $600,000 in 2021 to support bio-solids removal at the WWTP.
  • Managing the bio-solids aggressively this year will mean that the WWTP will be able to operate more efficiently and is expected to produce less odours.
  • The City has hired an engineering firm to help with short and long-term solutions for bio-solids management.
  • Odour masking agents are being considered but may not prove to be very effective with the volume of solids being moved and with the frequency of mixing required to achieve adequate drying.

How long before a new WWTP is in place?

  • The design for a new WWTP has been completed and is shelf ready for construction and will have full odour control and bio-solids dewatering onsite to allow for removal to landfill immediately.
  • The current cost estimate is $65M. The City is value engineering the design in order to identify opportunities to lower that cost.
  • The City requires the majority of the cost of the new facility to be covered by Provincial and Federal grants. Staff are actively researching grant opportunities and preparing for the grant application process.
  • Permitting for the new facility could take 2 to 3 years based on Ministry processes.
  • Construction of the new facility will take 2.5 to 3 years once a contractor has been selected through the competitive procurement process.
  • All options are being looked at with regards to the replacement of the existing WWTP to help make the process as affordable and viable as possible.

City of Kimberley Operations, May 27, 2021