Wastewater is a combination of used water that comes out of homes, schools, businesses, restaurants, car washes and industries. Wastewater contains a number of different substances, most importantly Total Suspended Solids (TSS). Suspended solids in the wastewater, if not removed and discharged into the environment, can decay or break down naturally by consuming oxygen. This demand for oxygen commonly known as Biological Oxygen Demand (BOD) is a measure of how clean the wastewater is.
Why Treat Wastewater?
There are many reasons to treat the wastewater before discharging back to the environment:
- Marine life and aquatic habitat protection – untreated wastewater can consume oxygen that is available for plants and animals, and cause them to suffer and may even kill them.
- Recreation and quality of life – untreated wastewater can affect swimming, sport fishing, boating, picnicking etc. by imparting undesirable colour and unpleasant odour to the receiving water.
- Health concerns – untreated wastewater can cause disease causing microorganisms to enter into receiving water that we may use for drinking and recreation.
How is Wastewater Treated?
Wastewater is treated in many different ways. All kinds of wastewater treatment involve removing suspended solids and reducing BOD in the wastewater. Please read through the following steps to understand how wastewater is treated by the City of Abbotsford.
Primary Treatment
Primary Treatment involves mainly mechanical processes such as headworks and primary sedimentation that removes up to 40 percent of BOD and 60 percent of TSS from the wastewater.
Secondary Treatment
Secondary Treatment is a biological process that removes up to 90 percent of BOD and TSS.
Disinfection
Disinfection is a process by which microorganisms present in the wastewater are killed using chlorine, Ultraviolet light or Ozone.
The secondary effluent is pretty clean, but it still contains large number of invisible harmful microorganisms that need to be destroyed before discharge into the Fraser River. To destroy the microbes, the JAMES Wastewater Treatment Plant currently practices disinfection by injecting chlorine gas into the wastewater.
Treated Wastewater Discharge
After disinfection, the residual chlorine in the wastewater is neutralized by injecting sulphur dioxide gas. The treated wastewater is then discharged by gravity or pumping into the Fraser River via a 1200 mm diameter outfall pipe.
Digesters
There are three digesters at the JAMES Wastewater Treatment Plant. They are large enclosed tanks where the skimmings and settled sludge from primary sedimentation tanks and secondary clarifiers are digested or cooked in the absence of air or oxygen. This digestion process greatly reduces the organic content and odour of the sludge. The solids that enter in the Digesters are pre-pasteurized at 65oC to reduce the pathogenic bacteria to negligible concentrations. The end products of the digestion process are methane gas and “Class A” Biosolids.
The methane gas is used as a fuel to produce heat and electricity at the plant. Biosolids are dewatered by centrifuges and the dewatered biosolids are temporarily stored on site before land application.
What Can I Flush or Put Down the Drain?
Everything that you put down your toilet and household drain ends up in our sewer system.
Flushing non-flushables can cause sewer blockages, damage pipes and treatment systems, backup sewers in your home and result in sewer overflows that harm the environment. This could mean expensive repairs for you and often, increased operations and maintenance costs to the collection system and wastewater treatment plant.
Non-flushable items include Fats, Oils and Grease (FOG), “flushable” wipes, dental floss, and many more. View the Sewer Savvy Brochure to learn more about what not to flush or put down the drain!
Fraser River Sanitary Forcemain
The existing 600mm diameter steel siphon sanitary main, from Mission to the JAMES Wastewater Treatment Plant (WWTP) in Abbotsford, was installed across the Fraser River in 1982, downstream of the Mission Bridge.
The District of Mission is now planning for a new sanitary sewer pipe, in parallel with the existing main, to increase capacity and provide redundancy to the existing forcemain.
The project is being delivered as two separate distinct contracts; the Land Contract and the River Contract. Both contracts are anticipated to be completed in the 2018/2019 fiscal year. Additional project information and the construction schedule is available on the Fraser River Sanitary Forcemain on the District of Mission's website.