OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 01012
Who Was Contacted and Phone: John Boyle (541) 498-2604
Contact Date: 03/30/2007
Contacted By: STRASSNER, BOB (DWP)
Contact Method/Location: Field
Reasons: N/A
Details: SUMMARY: Turbidity Profile DETAILS: The plant is treating raw water pumped from the Toketee Lake Penstock at a rate of 40 gpm. Raw water NTUs over this filter runs previous 14 hrs averaged 1.8 NTUs. Prior to backwash the preparation for the Turbidity Profile included a baseline of the settled water NTUs sample 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 1.8 NTUs. Sampling was begun at one minute intervals upon initiation of the backwash cycle. The systemWTP Backwash Process is automated requiring little involvement from the operator. The Multi media filter has 20 sq ft of surface area. Typical filtration rates on the filter profiled were 0.5 gpm 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 air scour operates for approximately 3 to 4 minutes to dislodge the surface matting of turbidity while the hydraulic rate increases thru the remainder of the 8 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 filters being brought back on line. The filter to waste cycle is completed upon reaching the set point and filtered water is pumped to storage. Samples from the filter are processed by the online instrument. ACTION NEEDED: Be available for technical assistance if requested. A Tracer Study is pending once the system instlles an Effluent Flow Meter.

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