In advanced treatment systems, the discharge may undergo an additional process to remove nutrients and other impurities. The science behind efforts to recycle and reintroduce water is so advanced, it can match the physical, chemical and biological properties of whatever receiving stream the treated water will be discharged into.
One example of this advanced treatment includes membrane bioreactor filtration. It is introduced after primary treatment and combines several systems to treat wastewater using biological and physical methods.
In the first step of the process, bacteria are introduced, which feed on dissolved nutrients and organic matterin order to grow and multiply. The bacteria and the material they have eaten are then removed by filtering through a membrane system called micro-filtration. This system removes virtually all of the bacteria and any other solid material from the water down to 0.1 microns. After this biological treatment, the water is forced through even finer filter membranes using a process known as reverse osmosis. Reverse osmosis removes any remaining dissolved organic or inorganic matter down to 0.001 microns.
A micron is 1/25,000th of an inch, or roughly 100 times smaller than the width of a human hair.
Reverse osmosis will remove virtually all contaminants from any water, including bacteria, viruses and micro-constituents.
Wastewater treated through these advanced processes produces water that meets or beats all state and local standards for Environmental Protection Agency primary and secondary drinking water standards and groundwater recharge.
In communities with combined sewer systems, where wastewater and stormwater runoff flow through the same pipes, all of the water is treated and released using the processes described above. However, many Florida communities operate separate sewer systems for wastewater and stormwater. In these instances, stormwater may be treated using interceptor basins.
Stormwater runoff is captured in these basins and flows up and down, through a series of devices used to direct and regulate the flow. This causes separation of heavy suspended particles, and lighter, floatable materials, which are trapped and removed before discharge.
Stormwater runoff may also run directly to specifically designed catchments or other holding systems, where it percolates back into the ground, filtered by sand and rock. Treated naturally as it seeps deeper into the ground, making its way to the aquifer, the natural cycle begins all over again.