Process Description - ProMinent DULCOMETER PH-501 Assembly And Operating Instructions Manual

2.1.2

Process description

Oil and Grease (O/G) removal
Raw sewage from the kitchens entering the system can contain high levels of fats, oils and grease that
can damage equipment and membranes downstream. To remove the oil and grease from the system
a double trap grease interceptor is installed prior to the kitchen sewage entering the fine screen.
Floating grease is removed via a vacuum truck hookup that will be used when the sludge tank is
emptied. A pipe and vacuum truck hookup are also used to remove any debris that sunk to the bottom
of the tanks. Vacuumed debris, oil and grease are to be disposed at the Meadowbank's tailings storage
facility (TSF).
Fine Screening
Raw sewage entering the MBR system contains particulates and solids that could damage the
equipment and membranes downstream. 0.5mm wedge wire fine screening protects the downstream
equipment by removing large solids and fibrous material. Two screens are used for redundancy so that
no unscreened influent enters the EQ tank. Redundant pumps are used to move the screened influent
to the equalization tank.
Flow-Equalization
Throughout the day the flow and strength of the sewage will vary. To accommodate this, an equalization
tank will buffer the flow and homogenize the loading. The equalization tank is aerated to maintain an
aerobic environment to reduce odors and to maintain suspension of solids and pumps transfer sewage
to biological treatment. This tank is provided with tank heaters. All wetted materials in this tank are
either stainless steel or polypropylene to eliminate the possibility of corrosion. In addition, the tank has
two liners, one primary, one secondary, with interstitial monitoring, providing the protection of a double
wall tank.
Biological Treatment
In the anoxic zone, the pre-treated sewage is combined with return activated sludge from the aerobic
tank and is kept mixed while maintaining a low level of dissolved oxygen (DO). Denitrification occurs
as specific microorganisms convert nitrates to nitrogen gas – reducing the total nitrogen (TN) in the
mixed liquor. Additionally, the anoxic stage optimizes the biological treatment process, which recovers
alkalinity, aids in stabilizing pH, and improves energy efficiency by reducing overall aeration demand.
In the aerobic zone, fine bubble diffusers create an aerobic environment where the organics contributing
to biological oxygen demand (BOD) and ammonia are oxidized by the biology. Dissolved oxygen is
continuously measured and aeration blowers controlled to maintain it in the range of 2 to 3 mg/L for
process optimization and energy savings. In the post-anoxic zone, return activated sludge from the
aerobic tank is kept mixed while maintaining a low level of dissolved oxygen (DO). The denitrification
process continues in the post anoxic zone to reduce the TN even further.
Phosphorous Reduction
Chemical precipitation is used to remove inorganic phosphate. An aluminum sulphate or "Alum" solution
is dosed into the mixed liquor causing dissolved phosphate to precipitate and coagulate. The
suspended phosphate cannot pass through the Newterra MicroClearUltra Filtration membrane (UF),
and the phosphate is eventually removed from the system as a solid with the waste activated sludge
(WAS).
Membrane Filtration
After being treated biologically, the treated effluent is separated from the mixed liquor and solids by the
Newterra MicroClear membrane modules and the permeate extraction system. The membrane
Operation & Maintenance Manual
Sewage treatment plant
February 2019
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