Blackburn Wastewater Treatment Plant Upgrade Study

Section 3.0 -Audit of exist in^ Facilities
of two industrial subdivisions, Western Acres subdivision and the Blackburn
area The plant was originally constructed as a high rate activated sludge
process. In 1996, the plant was upgraded to a trickling filter/solids contact
(TFISC) process by the addition of trickling filters and new secondary
clarifiers. The most recent upgrade of the plant was designed for population of
115,000 and an average dry weather flow (ADWF) of 44.5 MLld.
Waste primary and secondary sludge from the plant is stabilized by mesophiIic
anaerobic digestion. The digested sludge is dewatered and stored on the plant
site before being trucked off-site for application to agricultural and forested
land.
At the time of the plant visit in September 1999, the plant was treating about
30 ML/d, which is approximately 67 percent of its design capacity. There are
no reported serious operating or odour problems at the plant.
3.2.2 Preliminary Treatment
Wastewater entering the plant is screened on two 1,500 mm wide Envirex
mechanically raked bar screens. The screens have a bar spacing of 19 mm.
Screenings are removed on a belt conveyor to a pneumatic ejector. Each
screen is followed by a 900 mm parshall flume, and Fisher and Porter
ultrasonic level sensor, which serve as the principal flow measuring devices.
The screened wastewater enters two aerated grit removal chambers (only one
unit is normally in service at a time). The grit and scum is dewatered and
trucked off site for disposal at the Regional sanitary landfill.
3.2.3 Primav Treatment
The screened degriaed wastewater enters two covered rectangular primary
sedimentation tanks. The tanks are equipped with plastic chain and flight, and
cross collector mechanisms. As well, the tanks are equiped with scum removal
devices. Effluent from the sedimentation tanks is collected through a system
of submerged launders and flows into a wet well.
3.2.4 Secondary Treatment
Secondary treatment consists of biofilters (trickling filters), a solids contact
tank and two circular secondary clarifiers. Primary eMuent from the wet well
is pumped to a series of headers for distribution over the top of the biofilters by
three (2 duty; 1 standby) 60 hp Flygt pumps located in the main pumpstation.
The biofilter pumps for the pumping of primary effluent to the biofilters are