OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00847
Who Was Contacted and Phone: Randy Harris (541) 459-5768
Contact Date: 03/23/2007
Contacted By: STRASSNER, BOB (DWP)
Contact Method/Location: Office
Reasons: N/A
Details: SUMMARY: Turbidity Profile DETAILS: The plant is treating raw water pumped from Calapooya Creek impoundment at a rate of 1050 gpm. Raw water NTUs over this filter runs previous 22.0 hrs averaged 5.5 NTUs. Prior to backwash the preparation for the Turbidity Profile included a baseline of the settled water NTUs was established. The samples were taken from the top of the filter, at the location where the profile samples would be drawn. A siphon was started using a garden hose placing the intake just at the point on the surface of the filter where the backwash water would rise and spill into the washwater trough to waste during the backwash cycle. The continuous flow was directed to the lab sink where the baseline settled NTU was measured at 2.89 NTUs. Sampling was begun at one minute intervals upon initiation of the backwash cycle. The Sutherlin-non Pariel WTP Backwash Process is automatic requiring little involvement from the operator. The Multi media filter of which there are four with 110.25 sq ft of surface area are backwashed independently. Typical filtration rates on the filter profiled were 0.43 gpm min sq ft. Seasonal demands would typically double the filtration rates during summer. The plant does have an auto shut down on high NTUs. Once backwash is initiated and the media is fluidized the surface water operates for approximately 3 to 4 minutes to dislodge the surface matting of turbidity while the hydraulic rate increases to 1875 gpm for the duration of the 10 minute cycle. The Backwash pump times out and filter flows are reduced to a value to allow restratification of the media layers prior to the filter brought back on line. The effluent NTU meter has been off line during the Backwash cycle and is now automatically returned to service. ACTION NEEDED: Be available for technical assistance if requested.

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