The following question was posed on the Orlando Reddit thread, HERE, which was then forwarded to Bungalower to investigate, earlier today.

“What were they doing in Lake Killarney today? Saw this leaving MCO today” – Sled14

We reached out to our friends at the City of Winter Park, who promptly responded with the following explanation.

“We are conducting an alum treatment on Lake Killarney to bind up the phosphorus (which is a nutrient pollutant).  The alum helps remove the phosphorus from the water column, which would otherwise fuel algal blooms.  [HERE] is a link to our Waterways Newsletter with an article on alum. Sometimes we treat via applications directly to the lake, and sometimes our stormwater (runoff) coming into the lake is injected with alum in a pipe underground before it hits the lake.” – Clarissa Howard, Director of Communications

According to Howard, the aquamarine coloration of the water is temporary side affect of the treatment, and should disappear after a few days.

Phosphorous is a main ingredient in many fertilizers and can contribute to rampant algae growth in freshwater lakes.

Alum is a chemical compound (hydrated potassium aluminum sulfate) or more generally known as a sulfate salt, that are soluable in water and are astringent and acidic. It was traditionally used as a dye fixative in the Middle Ages, but was also used as a flocculant or water purification tool in Roman cities.

Brendan O'Connor

Editor in Chief of

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  1. I live by the lake. They’ve been out cleaning and treating water for several months now. The color, while unnatural, looks nice up close in the sunlight.