Wastewater Treatment Plant UPGRADE AND EXPANSION MEETS

Permit Compliance

An aging wastewater treatment plant together with stricter effluent limitations prompted West Lafayette to examine its long-term, 20-year, wastewater treatment needs. New requirements of West Lafayette's NPDES permit included the removal of ammonia and residual chlorine from plant effluent. Another key factor was the need to increase plant capacity from 7.8 mgd to 9 mgd (annual average) and from 14 mgd to 22.5 mgd (peak hydraulic). The resultant Wastewater Treatment Plant Upgrade and Expansion project provides the facilities for reliable, cost-effective compliance with the plant's NPDES permit and accommodates pending regulation of wet weather flows in combined sewer systems now and into the future. The project incorporated cost savings and increased reliability through the following facilities:

  • Low maintenance mechanically cleaned bar screens.
  • Energy efficient variable speed pumps.
  • Extended primary clarifiers fitted with longer lasting plastic/FRP collection equipment.
  • Modifications to allow step feed operation of the aeration tanks and increased effective treatment
  • Higher efficiency fine pore diffusers and blower equipment.
  • More reliable secondary clarifiers.
  • Waste activated sludge thickening to reduce recycle loads and to reduce digester loading and
    heating costs.
  • Increased digestion capacity by conversion of secondary digester to high rate digestion.
  • Increased reliability with the addition of second, independent electrical feeder.

Environmental benefits from the project include higher quality effluent to the river and increased treatment of wet weather flows.

SRF Loan Financed

West Lafayette used the State Revolving Fund Loan Program to finance the $15.8 million of capital improvements. The below-market interest rate will save the City more than $ 6 million overall. Sound planning and attractive financing has provided the citizens of West Lafayette with a cost-effective wastewater treatment facility that enhances the quality of the Wabash River and the community.

Plant Performance

Since start-up of the new facilities, plant performance has exceeded design requirements during both dry and wet weather. Removal efficiencies, average flow and effluent ammonia concentrations from January 1997 through December 1999 are:

  • Flow: Average -- 8.04 mgd
    Daily Maximum-- 23.4 mgd
  • TSS Removal Efficiency -- 96%
  • CBOD Removal Efficiency -- 97%
  • NH4 Effluent Average -- 0.70 mg/l

During a recent storm event of 1.85 inches, the treatment plant treated 18.72 mgd while producing effluent with a CBOD of 6 mg/l and total suspended solids of 11 mg/l.

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