Page 35 - MRWATODAYWinter2021final

Solutions

Flow Pattern Chemical Phosphorus Removal
Altering the way water flows through a wastewater pond Chemical addition is a common method of addressing
can help immensely in increasing the hydraulic retention phosphorus and is recommended only if lower effluent
time (HRT) and maximizing the depth of water. As the levels cannot be achieved using the other solutions
amount of time water stays in the pond system increases, provided in this report. A cost analysis for four chemicals,
the treatment time increases, leading to better nutrient ferric chloride, aluminum sulfate, Phoslock, and RE300,
removal and cleaner discharge water. The overall goal is was compiled. From this, ferric chloride, with a cost of
to keep the wastewater ponds as full as possible over the $21 per lb of phosphorus removed, was recommended. In
course of the year, ensuring that as much of the total pond order to reduce costs associated with the use of a boat
volume as possible is actually being used for treatment or mixer to add chemicals, gravitational addition of ferric
time. chloride solution to the transfer structures between the
primary and secondary ponds as water is being transferred
In ow and In ltration was identified as a lower cost option, utilizing the natural
Inflow and infiltration (I&I) refers to the unintentional flow mixing of the transfer process to distribute the chemical
of storm water into the sanitary sewer system. It leads to into the water.
ineffective use of the available volume in a pond, since
storm water does not need to be treated but still takes
up space, and reduces overall treatment time. Reducing “It has been great working with such talented
inflow and infiltration by performing dye tests, resealing professional and educated interns with the U of
manhole covers, and inspecting private properties would M MnTAP. The prospective and talents of the
serve to improve system hydraulic retention time. Interns brings confi dence and success to the
LCCMR wastewater pond optimization project”
Waterfowl Prevention ~ Frank Stuemke,
Minnesota Rural Water Association
Waterfowl, such as geese, contribute heavily to nutrient
levels in these ponds in the form of fecal loading. Because
waterfowl migration periods tend to align with wastewater
pond discharge windows, and waterfowl like to use
secondary, polishing ponds, slug loads of nutrients from
waterfowl may have adverse impacts on effluent nutrient “MnTAP interns provide site specifi c
concentrations. Deterring geese from landing on the ponds recommendations to operators for nutrient
during migration periods and deterring nesting at the reduction at their wastewater facility.”
ponds can lead to a direct decrease in nutrient levels. The ~ Tim Hagemeier,
use coyote cutouts and other decoys are suggested as Minnesota Rural Water Association
options worth testing to reduce direct waterfowl nutrient
loading into the ponds.

Reprinted with permission from 2020 MnTAP Solutions: http://www.mntap.umn.edu/resources/publications/solutions/

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2020 | MnTAP SOLUTIONS | www.mntap.umn.edu WINTER 2021 S MRWA TODAY 35