Update: A recent report from SGWASA's chemist team revealed details on a rise in algal blooms affecting our region's natural water supply. A key factor contributing to the algal bloom is thermal stratification. During warmer months, sunlight heats the surface layer of the lake, creating a warmer layer (epilimnion) that separates from the cooler, denser bottom layer (hypolimnion).
Lakes are stratified into three separate sections: I. The Epilimnion II. The Metalimnion III. The Hypolimnion
The scales are used to associate each section of the stratification to their corresponding depths and temperatures. The arrow is used to show the movement of wind over the surface of the water which initiates the turnover in the epilimnion and the hypolimnion. 2
This stratification process reduces vertical mixing within the lake. Nutrients that typically sink to the bottom and decompose, become trapped in the warmer surface layer, creating ideal conditions for algae growth.
The presence of algae bloom and thermal stratification in Lake Holt significantly impact the water treatment plant.
The recent rise of algae bloom levels in the natural water supply overwhelmed the treatment plant's filters. Algae can produce complex organic compounds that can clog filters. This reduced filtration capacity necessitated shorter filter operating times. 1
Our utility teams are positioned to respond to the increase in algae bloom and are operating on an increased flushing schedule, outside the service requirement to remove accumulated algae from the filters.
SGWASA's chemist team noted that the taste and odor profile of the water would be primarily influenced by the presence of geosmin and methylisoborneol (MIB). Biosynthesized by the algae during a bloom event, these compounds can be detected by humans at incredibly low concentrations in the parts-per-trillion (ppt) range, or nanograms per liter (ng/L).
Technicians are closely monitoring water quality and adjusting treatment as needed. SGWASA will continue to provide updates on the situation and any actions taken by the water treatment plant.
Issued 7/12/24 by the South Granville Water and Sewer Authority
Krystle Lee, PIO
(919) 575-3367
Learn more on these and other related subjects:
Thermal stratification. Thermal Stratification - an overview | ScienceDirect Topics. (n.d.). https://www.sciencedirect.com/topics/chemical-engineering/thermal-stratification
“Sewer Gas.” Wikipedia, Wikimedia Foundation, 10 Nov. 2018, en.wikipedia.org/wiki/Sewer_gas.
Technologies, S. P. (2020, January 15). Tips To Keep Your Pipes Odor-Free During the Hot Summer Months. SPT. https://sptpipe.com/tips-keep-pipes-odor-free-hot-summer-months/
Disclaimer: The article references posted on this page are provided solely for reference purposes. The advertising information within the video, article, and personal content beyond water facts do not necessarily reflect the views or opinions of SGWASA (South Granville Water & Sewer Authority) or the SGWASA Board. Any opinions or statements expressed in the article are those of the individuals or organizations.
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Reference:
Sacramento State Water Programs. (2017). Water Treatment Plant Operation, Volume 1 (7th ed.). Sacramento, CA: Sacramento State. 1
Figure 1. Lake Stratification (11).svg. Retrieved July 12, 2024, from Wikipedia https://en.wikipedia.org/wiki/Hypolimnion 2