New USBF Bioreactor was installed near the two existing units.
In 2009, after securing Provincial and Federal Grants, the Municipality embarked on a plant expansion and upgrade. The objectives of the approximately $2.3 million project were:
- Installation of new mechanical headworks
- Plant expansion to double the hydraulic and the biological capacity with a provision to triple it in the future.
- Incorporation of "tertiary" treatment allowing the municipality treated effluent reuse for irrigation, and in the future, in dual plumbing applications. This would require effluent parameters to meet the Municipal Sewage Regulations "Unrestricted Public Access" parameters of BOD and TSS of respectively less than 10 mg/l, Turbidity of 2 NTU (avg.), Fecal Coliform of 2.2 CFU/100 ml (avg.), Ammonia of less than 1 mg/l, and Total Nitrogen of less than 20 mg/l.
- Waste sludge dewatering, reducing the cost of trucking wastewater sludge off the island and the carbon footprint.
- Incorporation of a Pressurized Outfall Station
- Septage receiving pilot facility to evaluate septage processing in the USBF bioreactors, while again, reducing the cost of sludge disposal and the carbon footprint.
The initial design work carried out by a team of Kerr Wood Leidal (KWL) and ECOfluid Systems commenced in early 2010, and in August 2010 ECOfluid was awarded a Design-Build contract to execute the project.
As a part of the upgrade, all flows (forcemain and gravity) were diverted to a new inclined mechanical auger screen installed within a concrete channel leading to a refurbished influent pump station. The all-weather IPEC screen collects and compacts screenings into a continuous bagging system.
USBF Bioreactor
A new bioreactor was installed adjacent to the two existing ones. The Sludge Blanket Filter (SBF) of the bioreactor is fabricated from epoxy coated steel and provides separation of the anoxic and aerobic compartments.
The bioreactor anoxic compartment was equipped with a new submersible mixer designed to mix the influent sewage with activated sludge recycled from the bottom of the SBF, thus providing the necessary conditions for enhanced nitrogen removal by nitrification/denitrification processes, and phosphorus removal by biological "luxury uptake".
Tertiary Treatment
The tertiary treatment consists of membrane filtration, UV disinfection, chlorination and reclaimed water storage.
For filtration, Mitsubishi SteraporeSUN™ immersed hollow fiber membranes were selected. The membranes are installed within a separate tank receiving effluent pre-filtered by the Sludge Blanket Filter (<10mg/l TSS). The configuration (sometimes known as CAS-MF) not only results in safer multi-barrier two stage filtration but it has many other advantages over conventional immersed MBR systems. Fine screening is not required, flux rate increases, fouling decreases, and energy input is reduced. Additionally, the biology and the membrane filtration are separated and the processes can be better individually optimized.
