Recycling Treated Municipal Wastewater for Industrial Water Use

TM2: Sampling Plan and Results
Recycling Treated Municipal Wastewater for Industrial Water Use
Samples were collected at four Council WWTPs:
Blue Lake
Empire
Metropolitan
Seneca
3.0 Sampling Results
The sampling program developed for this project provided an initial base of
information that was used for various tasks in the project, including:
general characterizations of effluent water quality for Minnesota WWTPs
plant-specific information to compare the effluent quality of the Council’s four
largest WWTPs
This technical memorandum serves to document the data and provide summary
information on the effluent quality of the four Council WWTPs evaluated.
3.1 General Summary
The constituents analyzed in this project’s sampling program, indicate that hardness
and salt concentrations occur at concentration thresholds of concern for a range of
industrial water uses. Similar to the results of Technical Memorandum 5, Wastewater
Treatment Plant Effluent Quality, which reviewed general water quality parameters for
all of Minnesota’s WWTPs, the NPDES permitted constituents for the four WWTPs
were well below required limits and had low variability in the samples measured.
Table 4 provides the mean and standard deviation of the samples collected for the Fall
2006 and Spring 2007 sampling periods. The recommended limits for each constituent
as it relates to cooling water uses, is provided in the third column. Exhibit A provides
additional statistics for this table, such as minimum and maximum values, and the
number of samples the statistics are based upon. It also contains recommended limits
for various industrial water uses in a format similar to Table 4. Exhibits B-D provide
data for each WWTP.
The Fall 2006 sampling data were evaluated with time series plots to look for any
outliers and see if any trends existed. Given that this is a small data set (8-28 samples),
this effort was used more to screen and identify any gross trends. Additional data will
need to be reviewed over a longer period of time to define any trends.
6 Craddock Consulting Engineers
In Association with CDM & James Crook
TM2-Sampling_0707.doc