Municipalities in northern regions of US and Canada are often challenged with cold weather conditions that can adversely affect microbial processes in the waste water treatment facilities. In early 2016, a municipality in Western Canada was impacted by reduced nitrification efficiency of their waste water treatment process during the winter season. This resulted in the accumulation of higher than acceptable levels of ammonia before the treated water was discharged into a nearby waterway. This case study presents numerous challenges during design, fabrication and installation of a modular insulated cover (MIC) system.
There were several challenges we encountered from the beginning. One of the main challenges was to design a cover with the following design attributes:
|Minimum temperature required, cC (cF)
Other challenges included:
Solutions and Results
1. MIC Design:
To understand the heat losses, Layfield developed a heat loss calculator to model the heat transfer with and without cover system. The model provided us with the required insulation properties of the EPS foam. The calculations determined the project required a R17 foam to provide required heat conservation at temperatures as low as -40○C (-40○F).
The MIC needed to be sufficiently buoyant so that our field crew could deploy the covers without significant deflection. The MIC panels are typically composed of expanded polystyrene foam encapsulated with synthetic barrier on both sides.
2. Fabrication of MIC panels included:
- Encapsulation of the foam with layers of impermeable geomembrane.
- Customization panels to cover as much exposed surface area as possible.
- Testing the panel for leakage.
- Optimizing the size and weight of panel to aid in shipping
- Custom tensile testing was performed to ensure the weld strength of the strap holding sand tubes to MIC panels.
MIC panels were fabricated at the Layfield Edmonton plant.
3. MIC Installation:
Installation of the MIC was carried out in phases. The 1st phase was to cover only cell #3 in December of 2016. Cells #4, #8 and #9A were required to be installed by June 2017.
Installation took place in extreme cold conditions posed challenges to our field technicians. Material handling and installation of the materials was a major challenge on first cell (#3) as the MIC panels needed to be installed in temperatures as low as -26○C ambient with a wind chill factor often reaching -35○C.
The cover provided sufficient buoyancy for our field technicians and met our safety criteria. To minimize wind uplift of the floating MIC cover a ballast system was welded on the top of MIC panels.