The type of septic system installed, how deep, and sometimes how large the leach field is, depends on the characteristics of the soil. Septic leach fields are installed as shallow as possible to take advantage of higher oxygen levels in the soil nearer the surface so that the aerobic bacteria can thrive to break down the organic matter in the effluent coming from the septic tank. They are also installed shallow to stay above the water table. Other types of systems do not utilize a leach field, but some type of chamber filled with mulch or sand where the water is treated. In Florida, the soil is generally quite porous, and the water table is high. This complicates septic system optimization and can lead to failed and dysfunctional systems where the effluent is not being adequately treated.
Florida’s problem is mainly
aging septic systems that are no longer functioning adequately. According to
environmental scientist Iuliia Istratiy, reporting for the Sun Sentinel:
“Florida has more than 2 million septic systems, one of
the highest numbers in the country. Many of them were installed decades ago,
long before today’s environmental standards and rapid population growth. While
septic systems are often seen as a private household issue, taken together,
they have become a major public and environmental concern."
These systems were generally
not designed to remove nitrogen, and with the porosity of the soils, the
effluents are able to bring nitrogen into the local shallow groundwater and
even into nearby canals, rivers, and coastal waters. Excess nitrogen feeds
algae, reduces oxygen levels in water, and damages freshwater and coastal
ecosystems. It also contributes to ongoing coastal issues like red tides and
eutrophication. Florida is basically a coastal plain, a low-lying area where
water can collect. The coastal regions are the most vulnerable. Rising sea
levels, flooding, and storm surges can further allow the contaminated water to
move around. Istratiy writes:
“Florida has taken steps to address water quality
problems, but progress in upgrading outdated septic systems has been slow and
uneven. Replacing old systems or connecting homes to sewer lines can be
expensive, yet the cost of doing nothing continues to grow. Environmental
damage, health risks and economic losses place a much heavier burden on
communities over time.”
“Solving this problem will require coordinated action.
State and local governments need to prioritize funding for septic-to-sewer
conversions in the most vulnerable areas, improve maintenance and inspection
requirements, and help homeowners manage the cost of necessary upgrades. Public
awareness also plays a key role. When people understand how individual septic
systems affect shared water resources, the issue becomes a matter of collective
responsibility.”
I have worked as a regulator
and inspector in the past of household sewage treatment systems (ie, septic
systems) in an area where it was common for some older systems and occasionally
even some newer systems to fail. I know that for regular people, it becomes a
significant economic issue. In modern times, it can be very expensive to
replace a failing septic system, and it can even be financially inconvenient to
pay to have it maintained and inspected. Thus, cost tends to slow down
mitigation and replacement.
In January 2025, Florida
moved its onsite sewage program regulation and permitting for 16 counties from
the County Health departments to the Department of Environmental Protection
(DEP). Below is an update from the Florida DEP about the improved permitting
and inspection numbers in the target counties.
Researchers from Florida
Atlantic University’s Harbor Branch Oceanographic Institute looked at water
quality in southwest Florida, tracking microbes, and found that septic systems
were a major contributor to water quality degradation. According to Florida
Atlantic University:
“…there are about 39,768 “known” and about 57,054 “likely”
septic systems in Southwest Florida’s Lee County (about 100,000 total). To
identify sources of pollution contributing to the water quality woes,
researchers examined septic system- groundwater- surface water couplings
through the analysis of various parameters.”
The researchers tracked
microbes and nutrients and distinguished them into human and animal origins.
Their research was published in September 2022 in the journal Science of the
Total Environment. They utilized several tracers and indicators. One effective
indicator for human waste was sucralose. The researchers found that human waste
was definitely contributing to harmful algae blooms (HABs). One very important
conclusion is that:
“Most (>80%) water table depth measurements were too
shallow to support septic system functioning (<1.07 m).”
This basically means that more than 80% of the septic systems in this region are basically dysfunctional, or what we used to call “failing.”
The study showed that both groundwater and
surface water were significantly contaminated with septic system waste, from both
pathogens and nitrogen. Pathogens are indicated by fecal bacteria indicators
like coliform bacteria.
The researchers concluded:
“Urban water quality is complex because it is affected
by myriad environmental, economic, and political issues. This means that
resource managers must be able to identify sources contributing to water
quality decline and then prioritize mitigation and abatement strategies. Due to
the nature of human waste inputs (i.e., reactive nutrients, pathogens,
bacteria, pharmaceuticals, etc.), improved wastewater infrastructure and
management, including advanced wastewater treatment (nutrient removal), in …”
References:
Aging
septic systems fuel Florida’s growing water quality crisis. Opinion by Iuliia
Istratiy. Tampa Bay Times. February 2, 2026. Aging
septic systems fuel Florida’s growing water quality crisis | Column
Water
Quality Woes in S.W. Florida Linked to Seeping Septic Systems. Gisele Galoustian.
Florida Atlantic University News Desk. August 9, 2022. FAU
| Water Quality Woes in S.W. Florida Linked to Seeping Septic Systems
The
Onsite Sewage Program has moved to the Florida Department of Environmental
Protection. Florida Department of Health. 2025. Septic
Systems - Florida Department of Health
Program
Update - Phase I Transition. Division of Water Resource Management. Onsite
Sewage Program. Florida Department of Environmental Protection. Program
Update - Phase I Transition | Florida Department of Environmental Protection
Septic
system–groundwater–surface water couplings in waterfront communities contribute
to harmful algal blooms in Southwest Florida. Rachel A. Brewton, Lisa B.
Kreiger, Kevin N. Tyre, Diana Baladi, Lynn E. Wilking, Laura W. Herren, and Brian
E. Lapointe. Science of The Total Environment. Volume 837, 1 September 2022,
155319. Septic
system–groundwater–surface water couplings in waterfront communities contribute
to harmful algal blooms in Southwest Florida - ScienceDirect
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