Algae Control Methods Compared: The Importance of Successful Algae Control for Facilities with UV Disinfection


In Connecticut, with the change over to UV from Chlorination for disinfection at some of the State’s WPCFs (Water Pollution Control Facilities), it has been observed that an increase in attached algal growth along with a proliferation of a dense population of “tiny” snails (Pouch Snails) is occurring in the UV chamber(s).   The end result appears to cause an “artificial” increase in Suspended Solids in the final effluent and at some facilities there is the need for filtration of the plant water in order to be able to recycle it back into the facility without maintenance problems.

Pilot Study Site and Detail of the Problem

Between the State, Municipality and, Inc., it was agreed that the Jewett City WWTP in Connecticut, which was built in 2005 to process 1.1 mgd of wastewater, would be the best site for a Pilot Study using Weir Washing technology.  Unit processes for this plant consists of Pretreatment, Carousel type Nitrification/Denitrification, Clarification and UV disinfection.  In 2006, the plant staff documented increased suspended solids in the final effluent samples, due to snail shells because a snail population had proliferated in the UV chamber(s).  Mr. David Drobiak, the Superintendent of the Jewett City WWTP, requested assistance with this concern from the CT DEP.  DEP biologist, Joe Nestico, had suggested that the high snail population appeared to be the direct result of an available food source i.e. attached algae growing in the UV chamber.  Mr. Nestico suggested regular cleaning of the attached algal growth on the Clarifier Launders and Weirs and washing of the UV chamber(s) to minimize or eliminate the snail population.   The amount of maintenance by the Jewett staff was governed by the consistent reduction in algal growth and of course the snail population.  In essence, there was a lot of consistent work to be done in order observe a “cause and affect” change in the problem.

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