Domestic Tertiary Filtration
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Plant History: The wastewater treatment plant has operated for many years as a lagoon treatment process. Over the years, with tightening discharge requirements, it became necessary to filter the final lagoon discharge to meet these more strict permit requirements.
Plant Description: The facility operates as a four stage lagoon operation. There is no aeration capability in any of the ponds. The plant flow rates vary during the year with average flows being in the 200,000 gallon per day range with peak flows being up to 750,000 gallons per day.
Tertiary Filters: The Centra-flo Gravity Sand Filter Model CF-150 with six (6) airlift units in a single tank. The system is designed to remove algae and suspended solids from the plant discharge stream. The plant does not have the ability to add chemicals to aid in the removal of solids. The peak design flow to the filter is 500 gpm with solids loading being as high as 120 mg/l TSS. The filter is designed to remove 50 to 75% of the influent TSS and produce water with a maximum of 40 mg/l TSS or less.
Filter Startup: The first Centra-flo was installed in May 1998. Equipment startup was completed and the filter system was put online in July of 1998. The filter has been in continuous operation since startup at a flow rate ranging from 175 to 300 gpm. The operation has been uneventful with only normal operator attention required. Typical operator time required on a daily basis is less then 30 min. per day. The system has continually exceed performance requirements and met expectations of the engineer and the City of Electra.