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SUPPLY WATER
Black Mountain Irrigation District had encountered water quality problems in the past in Mission Creek, especially in 1997 when heavy rains and mudslides upstream of the intake produced poor water quality conditions. Black Mountain Irrigation District took a proactive role in determining the most feasible plan to treat each year’s spring run-off and maintain drinking water standards within the Guidelines for Canadian Drink Water Quality (GCDWQ). A water treatment facility was designed and built to provide the necessary means of treating Mission Creek water. WATER TREATMENT PROCESS: OPERATION The Black Mountain Irrigation District operates a Class IV water treatment plant and water distribution system. They both require use of a SCADA system although manual control of the plant and system is possible in the case of an emergency. The plant has produced some very good results since its construction. These include; reduction in total organic carbon (TOC) by 50% (TOC can produce trihalomethanes when combined with chlorine), reduction in turbidity in the water distribution system of less than 1 NTU even though turbidity in Mission Creek can exceed 150 NTU, and reduction of colour as well. Black Mountain Irrigation District continues to provide quality drinking water to their customers.
Water enters the grit pond and flows slowly through it allowing heavier particles such as sand and silt to settle out. Once the water reaches the end of the grit pond, process water for the plant is screened through 1.5 mm fish screens and excess water is bypassed and discharged through a fish channel that allows fish and floating debris to flow back into Mission Creek.
3. RAPID MIX Process water is metered by 2 magnetic flow meters. From this point, it enters the one of 2 rapid mixer tanks where coagulant (Isopac) is added along with a cationic polymer. Water and coagulants are then rapid mixed for upwards of 1 minute.
4. FLOCCULATORS Flocculation begins at the first of 3 flocculation tanks with anionic polymer addition taking place in the second flocculation tank. By the time the process water reaches the third flocculation tank, floc forms and is clearly visible.
The water then enters one of 2 clarifiers for sedimentation.
Water flows through the clarifiers through a HDPE baffle curtain. The curtain
creates a “plug” flow
through the clarifier and allows clear water to flow through it and the
sludge to settle out. Once the sludge settles out of the water, the sludge
is collected
and pumped to a sludge holding pond where it is further processed. The
clear water from the top of the clarifier is diverted to the first of 2 balancing
reservoirs.
6. pH ADJUSTMENT Prior to the treated water entering the first of 2 reservoirs, pH adjustment must occur for corrosion control. Caustic soda is added to the clarified water to provide water with a minimum alkalinity of at least 15 mg/L and a pH of 7.5. 7. DISINFECTION Once the water has moved through Steven’s and Hadden Reservoir and given further time to settle out particulate matter, chlorine disinfection occurs. A fine screening process occurs at this point to screen out any material that may have entered either reservoir and from here the water enters the distribution system. Treatment Plant Schematic:
PLANT PARAMETERS:
PROCESS:
WATER QUALITY PARAMETERS:
Thanks to Brian Thorburn
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water quality drastically.
