City of Pekin, IL


Waste Water

Wastewater Treatment

The City of Pekin, Illinois constructed Wastewater Treatment Plant No. 1 (STP #1) in 1939, and completed plant capacity expansions in 1963, 1970 and 1995. The effluent discharged from STP #1 is regulated by the City’s National Pollutant Discharge Elimination System (NPDES) permit, administered by the Illinois Environmental Protection Agency (IEPA).

The existing wastewater pre-treatment facility includes a mechanically-cleaned bar screen, an aerated grit chamber with grit washer system, and a channel grinder. The primary treatment system removes grease and scum using a surface skimmer system. The primary effluent is pumped by the effluent pumping system into a 24-inch RCP forcemain to a split flow chamber. The split flow chamber constructed in the late 1980s is equipped with slide gates that provide flow regulation to each of the three secondary treatment units. The chamber allows for operation of the secondary treatment system in either conventional or contact stabilization mode. The chlorination system, housed in the Blower Building, is in good condition. Historically, the sludge handling facilities at STP #1 have consisted of liquid sludge storage lagoons. In 1989, a gravity belt thickener, vacuum sludge drying beds, sludge storage pad, and associated piping, controls and metering equipment were added for sludge handling. The existing anaerobic digester system consists of two primary digester's, a secondary digester, an “old” out of service digester, gas recovery and conditioning equipment, and electrical controls.

Capacity of Treatment Plant

STP #1 is currently rated at 4.5 MGD average flow and 8.74 MGD maximum flow. The existing STP #1 is designed to treat up to 7,506 pounds-per-day (ppd) of biochemical oxygen demand (BOD5) and up to 9,383 ppd of total suspended solids (TSS). These ratings reflect raw sewage concentrations of 200 parts-per-million (ppm) BOD5 and 250 ppm TSS at a design average flow of 4.5 MGD.

Number of Connections

  • Approximately 13,000

Number of Employees

  • 5 at Wastewater Treatment Plant
  • 10 in Street/Sewer Division (Responsible for Collector)

Annual Amount Treated

  • 1,280,000,000 Gallons (2001) = 3.51 MGD Daily
  • 1,320,000,000 Gallons (2002) = 3.62 MGD Daily

Wastewater Collection System

  • 80-85 Miles Separate Sanitary Sewers
  • 17 Miles Combination Sewers
  • Slightly less than 3,000 Manholes Total