Recycling Treated Municipal Wastewater for Industrial Water Use

TM4: WWTP Effluent Quality
Recycling Treated Municipal Wastewater for Industrial Water Use
Craddock Consulting Engineers 3
In Association with CDM & James Crook
TM4-WWTP Eff Quality_0707.doc
Figure 1 presents the frequency of occurrence of CBOD5 concentration in the effluent
of all Minnesota WWTPs in 2005. Similar information is shown in Figure 2 for
facilities with design capacities greater than 1 mgd, defined as larger facilities for this
technical memorandum. The variability of effluent CBOD5 is also characterized for the
following ranges: < 5 mg/L, 5-10 mg/L, 10-20 mg/L, and >20 mg/L.
The average WWTP effluent CBOD5 concentrations are depicted by location and
facility capacity in Figure 3. As shown and further detailed in Figures 4-7, a high
percentage of Minnesota facilities produce a high quality effluent in terms of organic
concentration. There were 252 facilities with CBOD5 concentrations less than 5 mg/L,
accounting for over 600 mgd of the total WWTP design capacity in the state. A similar
number of facilities, with a combined design capacity of nearly 140 mgd, produced
effluent with CBOD5 in the 5-20 mg/L range. Only 16 facilities in Minnesota produced
an effluent with an annual average CBOD5 greater than 20 mg/L. The remaining
facilities did not measure CBOD5 in 2005.