How Your Treatment Plants Work

Wastewater treatment plants are designed to do one thing - clean dirty water. Manatee County treatment plants rank among the best in the state.

Steps in the Treatment Process

  1. Preliminary Treatment Phase - In this stage large objects and rags are removed from the waste system.
  2. Micro-organism Phase - Next, a healthy population of micro-organisms is kept alive to feed on incoming waste.  The generic term for these plant micro-organisms is "bugs."
  3. Final Phase - Lastly, the water is prepared before being placed into the reclaimed water system.

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Preliminary Treatment Phase

Aerial view of Aerator
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Aerial view of Aerator

From pumping stations raw wastewater is sent to the start (Headworks) of the treatment plant.  Bar screens allow water to pass through but capture rags, sticks, and other large objects, which are collected and disposed of in the landfill.  Then the wastewater passes through a grit chamber.  Removal of grit is accomplished either using slow moving water or by a centrifuge process.  With the slow moving water process, the flow of water is decreased, and grit falls naturally to the bottom of the tank where it can be removed.  The centrifuge process uses a procedure similar to the spin cycle on your washing machine where as the water spins heavy particles of grit are drawn naturally to the bottom.

 

 

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Micro-Organism Phase

Operator checking Activated Sludge Level
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Operator checking Activated Sludge Level

In this phase, air is added to the water so the "bugs" can breathe.   The mixture of oxygen and "bugs" is called activated sludge and is the heart of the plant.  It is used to consume the organic matter in the wastewater.  A certified operator keeps the balance of "bugs" and food in line.  If there are not enough "bugs" to feed on the incoming waste, the quality of water leaving the plant will be poor.  If there are too many "bugs" feeding on the incoming waste, the "bugs" will die from starvation, and the quality of water leaving the plant will be poor.

 

Next, are the clarifiers, where the water begins its cleaning.  In these tanks, the "bugs" realize that there is no oxygen and stop working.  They settle to the bottom of the tank and are then returned to the head of the aeration tank to continue feeding on incoming waste.  The water on top of the clarifier is sent to the final phase.

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Final Phase

Next, automatic backwash filters are used to clean the water.  Water flows downward through a media that is composed of one layer of sand and one layer of anthracite.  Clean water is pumped upward through the media to clean it.  Another pump removes the dirty water that is pumped upward and sends it back to the Headworks to be treated again.  After flowing through the media, the water goes to the chlorine contact chamber to be disinfected. 

 

The treatment plants generate almost 30 million gallons of reclaimed water a day. 

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The Dirty Side

Bio-solids Dryer
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Bio-solids Dryer

Once the water is cleaned we must deal with the by-product of the treatment phase - sludge (bio-solids).    In this phase, "bugs" are used to break down the composition of the sludge even further in tanks called digesters.

 

Manatee County treatment plants operate aerobic digesters.  These digesters contain "bugs" that require enormous amounts of oxygen to break down the sludge.    Once the sludge has been digested it is sent to a belt filter press.  The press is used to squeeze the water from the sludge.  After going through the press, the sludge comes out in the form of moist dirt.  Trucks haul off these biosolids to the Biosolids Dryer where they are pelletized to be sold for fertilizer to local farmers.

 

Sources of Wastewater

There are many diverse sources of wastewater that are generated in Manatee County.

Most individuals know about the generation of wastewater from the bathrooms; toilets, sinks, showers etc. Gray water is also produced by the washing machines, dry cleaners and other commercial industries that use water. Stormwater contributes to our wastewater system as well. This is the water that enters the system through the storm drains.

Quality of Water Output

Once wastewater has been treated it is known as reclaimed water. While not advisable to drink the water, it is treated to such high standards that it could be. Some areas of the country actually use reclaimed water as a drinking source.

In Manatee County, reclaimed water can be used

  • To irrigate parks, golf courses, medians and residential lawns. 
  • Tto irrigate citrus, pasture lands and other crops. 
  • Rapid infiltration basins can be used to allow high-quality reclaimed water to soak into the ground to recharge valuable ground water. 
  • Industrial facilities and power plants can use reclaimed water as a source of water for cooling, or for some manufacturing processes. 
  • To create, restore, or enhance wetlands. 
  • Supplied to fire hydrants and sprinkler systems for fire fighting. In Manatee County, fire hydrants connected to reclaimed water lines are painted a distinctive lavender. 
  • Used in decorative ponds, fountains and other landscaping features. 
  • Sprinkled at construction sites or other places to reduce dust.

Energy and Emissions