How Water is Treated
The Florida peninsula is made mostly of limestone. Limestone is a carbonate rock made up of the fossilized and calcified remains of oceanic organisms. It is generally a porous material with interconnected cavities.
When water beneath the earth’s surface fills in the spaces between soil particles and rock surfaces, the water forms what is called an aquifer. Underlying Broward County, the highly permeable limestone, and less permeable soil and sandstone makes up the Biscayne Aquifer. The Biscayne Aquifer is the primary source of water for all Broward and Miami-Dade Counties, and southeastern Palm Beach County. It is one of the most productive aquifers in the world.
The Biscayne Aquifer is an “unconfined” aquifer meaning that its water is not restricted below a layer of solid rock or clay as in a “confined” aquifer. Water flows generally in an east-southeasterly direction at a rate of about two feet per day. In some areas parts of the County, the aquifer is just a few feet below ground. Here, only a thin layer of porous soil covers the highly permeable rocks of the Biscayne Aquifer. The aquifer water levels (also called groundwater levels) in these areas rise rapidly in response to rainfall. Rainfall is extremely important in providing natural recharge to the Biscayne Aquifer. Another critical source of recharge is groundwater flow from the Everglades natural system and surface water from the County’s extensive canal network.
The unconfined nature of the Biscayne Aquifer is beneficial — it makes aquifer recharge easier — but it also means that the aquifer is offered little protection from sources of surface water and groundwater pollution. That means that we all play a very important role in protecting this important water supply.
While soils and vegetation offer natural filtration of pollutants and contaminants from water recharging the Aquifer, they have a limited ability to absorb these chemicals. It’s important that we as residents of Broward County take action to eliminate potential sources of water pollution. The proper maintenance of swales, canal and lake banks, and other drainage features is critical in providing drainage and water quality treatment Click here to learn more about how to maintain your water management system.
Here are a few ways to protect the water quality of the Biscayne Aquifer:
- Do not dispose of any materials or products in canals, lakes, or other waterways. This includes leaves and other landscape debris.
- Limit use of fertilizers, pesticides and herbicides, always follow label instructions, and remove any product from hard surfaces (like driveways and sidewalks) with a broom.
- Keep swales free of debris and plant material.
- Use groundcovers to reduce sediment erosion and improve water filtration
These practices, along with natural filtration and dilution within the aquifer, help to reduce the concentration of water pollutants and contaminants, but they don’t do the whole job. As water seeps through the aquifer, it dissolves minerals (generally calcium and magnesium), making the water “hard.” So, even though water in the Biscayne Aquifer is generally of very high quality, when water is pumped from the aquifer, it still requires additional treatment.
Lime softening is used to remove minerals (primarily calcium and magnesium), and some color from the water. The water is piped to treatment plants where lime and ferric chloride are added to reduce hardness and improve color removal. After softening, filtration purifies the softened water by removing the remaining particulates. Fluoride is then added for enhanced protection against tooth decay. Disinfection is the final step, and is done by adding chlorine and ammonia, otherwise known as chloramines. A small amount of disinfectant is maintained throughout the distribution system in order to ensure high quality water. These chemicals are harmless to humans and animals but fatal to tropical fish, so before adding tap water to aquariums, use an additive that destroys chloramines. They are available wherever tropical fish are sold.
An alternative to lime softening is membrane softening. Many of the water utilities in Broward County are transitioning to or have already moved to this treatment process because it does a better job at removing disinfection byproducts (trihalomethanes and haloacetic acids) and tannins (dissolved organic matter) that can be present in water. Tannins (humic acid) can cause water discoloration, making it slightly yellow, like the color of tea. Since water in the Everglades contains a lot of humic acid and is a major source of recharge to the Biscayne Aquifer, our groundwater can be affected as a result. Although just an aesthetic concern, many utilities have sought to improve water quality treatment through this advanced treatment process which involves the use of membrane filters with a microscopic pore size. One drawback to the use of membrane technology is that it has a lower rate of recovery than lime softening. Therefore, it requires more raw water to produce the same amount of drinking water. This makes water conservation even more necessary.