Treatment Process

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The Water Pollution Control Department shows their commitment to environmental stewardship by ensuring that wastewater is treated above and beyond the required standards as set forth by the National Pollutant Discharge Elimination Standard (NPDES) permit. The plant took in and treated an average of 18.7 million gallons per day (MGD) in 2016 from more than 476 miles of sewers in the City service area. The treated wastewater that gets discharged into the Wabash River has the following removal rates from beginning to the end of the treatment process:
  • 99% removal of Total Suspended Solids (TSS)
  • 99% removal of Carbonaceous Biochemical Oxygen Demand (CBOD)
  • ~100% removal of ammonia
  • 90% phosphorus removal
To give you an idea of what the NPDES maximum final effluent permit standards are and what the WPCD actually discharges into the Wabash River, check out the table below that represents the averages for 2016:

   CBOD (mg/L)  TSS (mg/L)  Ammonia-N (mg/L), Summer  Ammonia-N (mg/L), Winter Phosphorus (mg/L)  pH 
NPDES Requirement  25  30  4.9  9.3  1.0 6.0-9.0 
Actual Discharge Level  3.8 3.43 0.024 0.047  0.74**  7.35
**On August 1, 2016, three 7,400-gallon fiberglass storage tanks and 10 Watson-Marlow pumps were installed to aid in phosphorus removal with the use of ferric chloride.
Did you know...
  • There are three backup generators at the plant in case of power outages to ensure that even during inclement weather, wastewater can be treated without interruption.
  • The Lafayette Water Pollution Control Department (WPCD) lab consists of two, full-time lab technicians as well as a lab chief, that spend each and every day analyzing the water that comes through the wastewater treatment plant. Lafayette boasts one of the nicest wastewater labs in the state. Laboratory technicians perform more than 24 tests each day, measuring everything from phosphorus to pH, and report results to the plant operators so they can adjust treatment as needed. The lab also monitors local ditch, creek and river water, as well as wastewater from local industries. 
  • In 2016, the WPCD produced 24,097,440 cubic feet of methane and thus saved about $688,000 on natural gas.

SPOTLIGHT: "BUGS"

Microorganisms, or "bugs," are essential in the wastewater treatment process. When the wastewater moves to aeration tanks, in which air is blown into the tanks, encouraging the growth of the oxygen-consuming bugs, which consume the dissolved organic matter in wastewater. The bugs multiply and form a suspension, and this mixture of suspended solids and wastewater moves on to the secondary settling tank, where the suspended solids, called "sludge," settle out by gravity. The sludge is sent to a gravity thickener belt, where a polymer is added to allow for flocculation. Excess water is sent back to primary treatment, and the thickened sludge is sent through the anaerobic digester for decomposition. These microscopic organisms are viewed under a microscope by personnel daily.

Scroll through using the right or left arrows to explore the different types of bugs you would find throughout the wastewater treatment process.

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The stalked ciliates, as shown, attach themselves to the flocculent mass, or floc, that forms during the wastewater treatment process. The presence of these protozoans is an indicator of a stable activated sludge process, which leads to proper settling and good effluent quality. The cilia have a stalk by which they anchor themselves to a piece of floc. They also can grow heads, or "zooids," and a higher number of heads indicates older sludge.

Source: Iowa Rural Water Association
STALKED CILIATES.pub
Free swimming ciliates are able to swim and chase after their prey, not needing to attach to the floc like the stalked ciliates. The fast movement of their hair-like structure called cilia propels them forward through the wastewater. Free swimming ciliates are normally found in maturing sludge processes and are indicators of a stable sludge environment.
FREE SWIMMING CILIATES
Rotifers are useful in removing any remaining material in the wastewater, but should never be dominant in the system. These metazoans emit a sticky substance to help the floc stay clumped together and firm. They are good indicators of wastewater toxicity.


Source: Iowa Rural Water Association
ROTIFER
Nematodes are generally 2-3 millimeters long and are long and thin, resembling earthworms under a microscope.They are more on the stiff side and move through the sludge by gliding or writhing. Nematodes are useful for indicating when toxins have been introduced. They are common in older activated sludge.



Source: Environmental Business Specialists
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