PROJ00156

• Contract/PO #: C153721
• Contractor Name: Lyons, Town of
• Contract Type: Loan
• Water District: 5
• County: Boulder
• Loan Projects - Doc Type: Feasibility Study

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Table 4, Flocculation/Sedimentation Rating Summary

Existing

USEP A CDOH
(2) (3)
10-40 range 20-30
2- 3 3
10.75 range 10-70
n/a 0,5-2,0

Flocculation: HDT (minutes)
Stages (recommended)
Mixing (G Sec -1)
Pipe velocities (fPs)

94 (note 1)
1
Unknown
2,S4 (for 12")

Sedimentation: Surface overflow rate for

Upflow type (g,p,m.lff) LOS
Tube settler type (g,p,m.lft2) n/a

0,5-0,7 0,7
1.0-2,0

n/a

Notes:
(1) Computed at 1043 g,p,m, flow rate; 24-hour production of 1,5 MGD, The HDT
for the existing basin configuration is a total of 94 minutes, Flocculation HDT is
unknown but probably inadequate,
(2) Refer to USEPA Handbook,
(3) Refer to Colorado Department of Health, Design Criteria,

The duration for which a filter is on-line, called a filter "run", is dependent upon the turbidity
of the filter influent. As the production rate through each filter decreases, due to particles
entrapped in the filter, water level rises over the filter. The rising level is detected upstream
in the clarifier unit; rising levels signal an automated valve to throttle the rate of raw water
entering the treatment plant, Chemical addition equipment is similarly adjusted by the
operators when production rates are significantly decreased, The operator manually shuts
down the plant by closing the influent valve and begins the backwash sequence to clean the
filters, At existing peak flow rates of 1043 g,p,m., existing loading rates to the filters are 2,9
g,p,m.lft2, as compared with a maximum rate of 5,0 g,p,m.lft2 as the state criteria, Using the
5,0 g,p,m.lft2 rate, the current potential for the filter process is about 2,34 MG/24 hrs,

Detailed review of 1993 operating records and interviews with the operator have revealed that:

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