Wastewater Treatment Process

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Wastewater treatment, or water reclamation, is a multi-stage process to restore wastewater by removing organic matter, solids, nutrients, disease-causing organisms and other pollutants before it is discharged into a body of water.

Wastewater samples are taken daily for laboratory analysis both on the inlet and outlet side of operations. Samples taken on the inlet side are analyzed so that treatment can be optimized if the content in the wastewater coming into the plant differs from typical wastewater flows. For example, if there are hydrocarbons or some other volatile substance released into the sanitary sewer system, the treatment operations must be altered to accommodate this substance and to protect the river when the effluent is discharged after treatment.

Final effluent is tested daily before being discharged into the South Saskatchewan River to ensure it meets both Federal and Provincial regulatory requirements.

The wastewater treatment process begins at the Headworks.

Parshall Flume

After being transported across the river through buried high density polyethylene pipes, wastewater flow enters the Headworks Parshall Flume channel. The Parshall Flume is located on the North side of the Headworks building where the flow is metered and a daily composite sample is taken for laboratory analysis.

Grit ScreeningsCoarse Screeners

The wastewater continues into the Headworks building to a set of coarse screeners where larger objects like sticks and rocks are removed.

Grit Removal

Flow then enters the grit removal chambers where a significant portion of inert materials such as sand and silt settle out along with the heavier organic materials entering the facility. The settled grit is removed from the chambers by a chain and bucket system and deposited into a bin along with the other materials captured by the coarse screeners.

The grit and screenings materials are transported to the Waste Management Facility for disposal in the Landfill while the remaining wastewater liquid continues on toward Primary Clarification.

Chemically Enhanced Primary Treatment (CEPT)

Prior to being discharged into the Primary Clarifiers via the Primary Splitter Box, the wastewater is dosed with Aluminum Sulphate (Alum) as it is leaving the Headworks building. The Alum aids in the flocculation of the solid matter remaining in the wastewater. As the wastewater enters the Primary Splitter Box, Anionic Polymer is fed into the wastewater. The combination of the Alum and Anionic Polymer enhances the removal of the suspended solids, phosphorus and Biochemical Oxygen Demand (BOD) within the Primary Clarifiers.

Primary ClarifiersPrimary Clarification

The Primary Splitter Box evenly distributes the flow between three Primary Clarifiers, each being 21 metres in diameter, which are used for the initial settling of the wastewater. The wastewater remains in the clarifiers for an average of three hours to remove approximately 25% of the BOD and approximately 55% of the suspended solids from the waste stream.

This process produces a primary settled sludge which is removed and sent to a sludge thickener to further increase the density. The effluent from the Primary Clarifiers flows to the Trickling Filter Pumphouse where it is then pumped to the top of the trickling filters for further treatment.

The wastewater is now split into two separate stream types; Solids versus Liquid Streams.

Solids Stream

Sludge Thickener

The settled sludge from the primary clarifiers is pumped to the Primary Sludge Thickener building. The sludge thickener is a similar tank design to the primary clarifiers, but only 7.6 metres in diameter and provides additional retention time for the primary sludge to settle and increase in density.

Sludge Belt Pressing

Gravity Belt Thickening

Sludge is moved from the Sludge Thickener to the Secondary Dewatering building and is moved along two gravity belt thickeners where additional polymer is added to the sludge to aid in further thickening prior to the secondary sludge pressing.

Secondary Dewatering Presses

Sludge continues to move along conveyor belts that compress the sludge to remove the remaining liquids. This conveyor belt empties into a dump truck for transport. Sludge that may still contain too much liquid (not solid enough) is moved back through the process until it thickens to the proper consistency for use in the compost operations. Residual effluent compressed out of the sludge is transported to the Trickling Filters in the Liquid Stream for further treatment.

The final waste product which we’ve referred to as sludge is transported to the Waste Management Facility Compost operations for processing into the Biosolids Compost.

Liquid Stream

Trickling FiltersTrickling Filters

Effluent from the Primary Clarifiers is pumped up and distributed between the two trickling filters. The tricking filters are concrete structures filled with plastic media covered with a zoogleal mass of micro-organisms that completes biological treatment of the primary effluent. The trickling filters are designed with a maximum BOD removal of 4800 kg/day. The trickling filter effluent, averaging a dissolved oxygen level of 9 mg/L, is transferred to the Solids Contact Channels.

Solids Contact Channels

There are two solids contact channels, one for each trickling filter. Each channel contains 232 air diffusers which keep the remaining suspended solids from settling out. These channels transport the effluent to the Secondary Clarifiers. Near the end of the contact channels, Aluminum Sulphate (Alum) is introduced to the effluent prior to being deposited into the Secondary Clarifiers to facilitate the settling of any remaining solids and phosphorus removal. Phosphorus must be removed prior to the final effluent being discharged to prevent weed growth in the receiving water.

Secondary Clarification

Effluent from the Solids Contact Channels is distributed between four Secondary Clarifiers. The secondary clarifiers aid in additional settling time and polishing of the final effluent. Retention time in the secondary clarifiers is approximately 7.5 hours.

The final removal efficiency after the secondary clarification process is 98% Biochemical Oxygen Demand and 95% Total Suspended Solids. The final effluent is transferred through the final effluent Parshall Flume metering point to the Ultraviolet Disinfection System.

Return Secondary Sludge

A portion of the settled sludge from the secondary clarifiers is returned to the head of each contact channel to aid in flocculation of the fine colloidal particles which continuously slough from the trickling filters while the remaining sludge is transferred to the start of the Solids Stream for processing.

UV DisinfectionUltraviolet Disinfection

Final effluent is passed through the UV Disinfection system which has low pressure, high intensity lamps that disinfect the effluent to below 1000 Total Coliform and 200 Fecal Coliform counts. There are two reactors, each containing 128 UV lamps, with room to add a third when it is required in the future.

After UV disinfection, the final effluent is pumped into the storage ponds prior to being discharged to the river. A daily composite sample is taken of the final effluent and tested in the lab to ensure compliance before discharge.

Storage Ponds

There are five storage ponds that cover approximately 35 acres. The storage ponds are gravity fed, moving the effluent through and discharging into the river through diffusers under the water surface.

Storage pond #2 is left empty to provide the facility with additional holding capacity during abnormally high flow conditions or for emergency bypass purposes (i.e. power outage). Storage pond #2 is isolated from the other storage ponds with a capacity of approximately 36,000m3. Wastewater can be bypassed to this pond without interruption to the rest of the facility and then returned to the Headworks system for treatment once flows have diminished, repairs are completed etc.

Discharge

Final effluent discharge to the river goes through diffuser nozzles that are located just below the river bottom. The diffuser nozzles distribute the flow of the effluent into the river flow.