Selkirk Waste Water Treatment Plant

Upgrade Project

Old Rexnord bar screen removed and replaced with new Headworks bar screen.

Screenings compactor installed Chlorine Disinfection system removed and

replaced with UV disinfection system

The Project

Bar Screen and Screenings Compactor

Screenings removed by rake and dropped into screenings compactor. Screenings are then compacted and dropped into a waste bucket, which is periodically emptied by a private contractor.

A screen with uniformly spaced bars meant prevent debris from getting into the process

A rake is used to clear the bar screen of built up materials.

A wiping mechanism cleans the rake of material.

Bar Screen

Bar screen removes solids from influent flow

Rexnord Cable Operated Bar Screen Bar dimensions: 2” x 3/8” x 3’10” Bar spacing: ¾” Overflow weir upstream bypassing bar

screen Wet weather design capacity of 8.5 million

gallons per day before overflow when half plugged

Wet screenings fall directly into waste bucket

Original bar screen

Not effectively screening out smaller debris Too much solids getting through Aging (40+ years old)

Reason for Upgrade

Old bar screen rake

Headworks Mahr continuous rake bar screen Bar Dimensions: 0.8cm x 0.4cm x 100cm Bar Spacing: 3/8” 10 degree incline (from vertical) increases

surface area exposed to flow

New Bar Screen

The continuous rake travels to the bottom of the channel and sweeps up, clearing the screen

Bars are easily replaceable, installed without welds or permanent fixtures

Heavy duty roller chains can sustain a minimum average exertion of 137.5 kN of force applied by the rake(if required too)

Screenings discharged into screenings compactor

New Bar Screen Cont’d

Screenings discharge from screenings compactor

Wet screenings pile into the top of the screenings compactor

Once screenings compactor fills to a certain level, a hydraulic ram pushes the screenings through the compactor, and into a waste bucket

Hydraulic ram presses out water held in screenings, significantly reducing volume and weight

If the bar screen runs continuously for a set period of time, the screenings compactor will run continuously until the bar screen stops

Screenings Compactor

Effluent Disinfection System

Flow can be directed through either UV module bank, or overflow

Treated effluent from UV modules is discharged

from the plant

2 Wallace and Tiernan V-notch Chlorinators Injected chlorine on a flow proportional

basis Chlorine contact chamber water retention

time 15 minutes Ideal residual chlorine in effluent: .5 ppm

Chlorine disinfection system

Upgraded to beat new legislation banning residual chlorine in wastewater effluent

UV system is lower maintenance than chlorine system

Reasons for Upgrade

Aquaray 40 VLS HO UV disinfection system Produces Ultra-Violet light at the 253.7 nm

wavelength. Disinfects by altering Bacteria DNA to

prevent reproduction Effectiveness dependent on water quality

(Clarity, Suspended Solids, etc.)

UV Disinfection system

Two channels with a bank of 3 UV modules each are online. Generally

only two modules of one bank are needed to effectively disinfect,

based on the flow rate

UV light can severely damage skin and eyes if overexposed. UV protective goggles and clothing required for prolonged exposure

Cleaned approximately every 2 months CLR, Scotch Bright pads, and high pressure

water are used to clean light jackets

UV Disinfection Safety and Maintenance

Cleaning pit and bubbler provided proved only marginally effective. Modules are cleaned by hand and rinsed with a pressure washer.

Modules are easy to lift out of the banks

with an overhead hoist

UV light bulb change quick and simple, reducing down time

Apart from cleaning, UV modules require very little human interaction. Monitoring is done to ensure UV modules are still disinfecting

UV Maintenance Cont’d

Lights are simple to unplug and replace, minimizing the time a single module has to be offline for a light bulb change. Other modules can be turned on to compensate for offline module.

Upgrades improve ease of operation of treatment plant

Reduced maintenance time and costs Discharge more environmentally friendly Beat legislation and costly upgrades due to

failing equipment

Conclusion

Questions?