Treatment Plant Performance


Design Criteria

ContaminantDesign Average (Daily)Wet Weather Peak (Daily)
BOD91,300 lbs.
SS91,300 lbs.
TKN2,510 lbs.
  • MGD - Million Gallons per Day
  • BOD - Biochemical Oxygen Demand
  • SS - Suspended Solids
  • TKN - Total Kjeldahl Nitrogen (Organic Nitrogen + Ammonia)

Effluent Requirements

BOD10 mg/L
SS10 mg/L
NH3< 3.1 mg/L
pH6 - 9
E. Coli126 Daily
Oil and GreaseMonitoring Only

Average Effluent Water Quality for 2021

ContaminantTesting Result
BOD 6 mg/L
SS 3 mg/L
NH3 .48 mg/L
pH (median)7.3
E. Coli 4.9/100 mL
Whole Effluent Toxicity TestPassed
Total Phosphorus0.38 mg/L

Charts & Terms


Industrial and residential wastewater flowing into the SW Wastewater Plant.  


Fully treated influent flowing from the SW Wastewater Plant to Wilson's Creek.

% Removal of Influent Loading

SW Clean Water Plant is required to have a minimum of 85% removal efficiency on a 30 day average of BOD, TSS, and Ammonia.


Loading in parts per million (ppm) for influent/effluent:

Biochemical Oxygen Demand (BOD)

Measure of the amount of oxygen required to biologically stabilize a waste stream.  NPDES Permit limit for Effluent is 10 mg/L.   

Total Suspended Solids (TSS)

The amount of insoluble solids floating and in suspension in the wastewater.  NPDES Permit limit for Effluent is 15 mg/L.

Ammonia (NH3-N)

A government regulated nutrient which requires removal to prevent degradation of receiving stream.  NPDES Permit limit for Effluent 1.3 mg/L seasonally. 

Total Phosphorus (TP)

Essential chemical element and nutrient for life forms.  TP is a Government regulated nutrient which requires removal to prevent degradation of receiving streams.  NPDES Permit limit for Effluent is 0.5 mg/L.

Escherichia Coliform (E. Coli)

A genus and species of the fecal coliform bacteria group.  E.Coli is present in the intestines of warm-blooded animals and humans.  NPDES Permit limit for Effluent is 126 coli/100 mL  As of October 2014 the SW Plants NPDES permit changed to monitoring Escherichia Colifom.

Per- and Polyfluoroalkyl Substances 

Sludge Volume Index, Food / Microorganism Ratio & Sludge Retention Time

Sludge Volume Index, Food / Microorganism Ratio, and Sludge Retention Time are used in conjunction to assure the proper function of the activated sludge process.

Sludge Volume Index

The Sludge Volume Index (SVI) is the ratio of volume of sludge to settling quality. SVI is an indication of the density the settled sludge attains in a 30 minute settling test. A low number (100 to 200) indicates good settling and shows the process is working properly. A high number (>500) indicates poor settling and shows the process may need adjustment.

Food / Microorganism Ratio

Food / Microorganism Ratio (F/M) is a measure of the amount of food material (organic material in the wastewater) available to the activated sludge microorganisms. The plant processes function best when the amount of food is balanced with the amount of microorganisms. Either too much food or not enough will cause poor plant performance.

A high rate process would require a high food to microorganism ratio (>0.5). This requires a fairly constant food rate and is more prone to upsets. A conventional rate process requires a midrange F/M ratio (0.25 to 0.5). Conventional rate processes take food rate changes better and are easier to control. Extended aeration processes require a F/M in the range of 0.05 to 0.1. They are relatively simple to operate and even less prone to upsets. The NW Treatment Plant is a modified Extended aeration process. The process is regulated to keep the ratio in the range of 0.09 to 0.15.

Sludge Retention Time

Sludge retention time (SRT) is the average number of days microorganisms are kept in the activated sludge process before they are removed for beneficial reuse. The plant processes work best at the proper SRT. The plant is designed to operate in a range of 10 to16 days.

Additional Charts

Plant Effluent 2016

Southwest Clean Water Plant National Pollution Discharge Elimination System Permit Compliance

Municipal wastewater treatment plants buffer the natural environment from the wastewater generated in urban areas.  Uncontrolled the wastewater would degrade the water, land, and air on which we depend.  Strict government agencies and regulations, followed by the City of Springfield's Waste Water Treatment Plants, ensure the safe treatment and disposal of wastewater and biosolids.  The City of Springfield is committed to protecting the water quality of the Ozarks for many generations to come.  The SWCWP is an award winning facility for it high quality of treatment it provides.  It has received its Platinum 8 NACWA Award for zero NPDES violations for the 8th consecutive year.

  • Governed by Environmental Protection Agency (EPA) and Missouri Department of Natural Resources (MoDNR) through the Clean Water Act
  • National Pollutant Discharge Elimination System (NPDES) permit compliance program
  • SW Waste Water Treatment Plant NPDES permit


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