Remediating Nitrogen From Septic Systems

Basin Management Action Plans mandate, in certain areas, one of two options regarding the remediation of nitrogen release from traditional septic systems. One option is to replace one’s conventional, passive (non-electric) system with a nitrogen-reducing system (electricity-dependent), often called an “advanced” system. Here is a comparison of various septic systems.

WARNING: Your knowledge of these facts may anger you!

Conventional/Passive Systems – no modifications for nitrogen reduction

A conventional septic system allows gravity (not electricity) to transport waste from its source to the septic system. The system uses a tank to separate solids from liquid and breakdown bacteria. The liquid waste (effluent) flows into a drainfield where it is dispersed into soil beneath it. Finally, Florida law requires a minimum of 24 inches of soil separation between the drainfield and groundwater where further treatment occurs.

The installation cost of a conventional system is relatively inexpensive (approximately $6,000). Maintenance cost are approximately $300-500 every five years for a pump-out and inspection. There is no monthly expense and electricity is not needed.

Properly maintained, a conventional system operates efficiently for 20-30 years.

The Florida Department of Onsite Sewage says this is a “safe and effective means of wastewater disposal.” Although not designed to attenuate nitrogen, properly maintained traditional systems reduce nitrogen by 47 percent.

A 2017 study, initiated by CPR-FL with the Florida Department of Environmental Protection, documents that, given 13 feet of soil beneath a drainfield, a conventional septic system reduced nitrogen by 85 percent.

“Advanced”/Active Systems – A conventional system with tank modifications

An “advanced” system uses a modified septic tank to reduce nitrogen. Gravity transports waste from its source to the septic tank. In the tank solids and liquid are separated and nitrogen is treated. The modified tank uses mechanical moving parts and is dependent on electricity to reduce nitrogen. From there, the liquid is dispersed through a drainfield where it is released into the soil.

The installation of an “advanced” system is noticeably more expensive than a conventional system – approximately $20,000. A maintenance contract (approximately $300 – 500 annually) is required in addition to on-going electricity expense. This system requires a pump out more often than a traditional system due to their smaller pretreatment tank where separation tales place.

As with any electro-mechanical complex design, properly maintained, an “advanced” system can operate for 10 years before replacement is typically needed.

“Advanced” systems are tested in artificial conditions in laboratories using a simulated effluent called a “slurry,” which is approximately fifty percent of the strength of average household effluent.  If it can be shown that they reduce nitrogen by 50 percent, they receive a 245 rating from the National Sanitation Foundation (NSF). Neither  NSF or Florida Department of Health tests for nutrient reduction after they have been installed. In real-life conditions, limited testing of these complex systems show their nitrogen reduction can be as low as 33 percent with frequent breakdowns.

Innovative/Passive Systems – A conventional system with drainfield modifications

SPECIAL NOTE: Although innovative technologies described here have been known about for over 10 years, none have been permitted for use in Florida.

These innovative technologies use the same components as conventional systems (tank, drainfield and soil). Wastewater effluent from a conventional septic tank flows into a modified drainfield which is completely passive, requiring no electricity and no moving components. The drainfield pipes are re-designed to enhance treatment. Nitrogen reduction of up to 90 per cent is achieved. There are no on-going maintenance expenses other than a tank pump out and inspection as with a conventional system. Properly installed and maintained, such systems have an estimated life of 20-30 years. Installation costs of such systems is approximately $10,000.

Another way to modify a drainfield for nitrogen reduction is to lay a carbon-based material under the drainfield. As wastewater filters through the underlayment, carbon reductions of 90 percent and more can be achieved.

One such material was developed at the University of Central Florida approximately ten years ago. It was appropriately called “BOLD & GOLD.” This underlayment “medium” consisted of gravel and old, ground-up tires. Regretfully, attempts to develop this product with FDOH for use in residential septic systems proved futile. It is being used to underline stormwater drainage basins by some communities.

Another underlayment discovery is wood chips. Wood chips serve as a carbon-based medium which can reduce nutrients. Such an underlayment is completely passive requiring no electricity or moving components. Experimental woodchip underlayment has been installed by the Florida Department of Environmental Protection in only two known Florida residences. Their operational performance has not been publicly released. A third new wood chip design and installation requirements published in Florida code was never installed and tested by FDOH. Nevertheless, this wood chip design is approved for residential use by the Florida Department of Health.

Estimated at $20,000 or more. Residential use of wood chip underlayment has yet to be utilized by homeowners because FDOH has encumbered its installation and use with so many unnecessary rules, including mandatory deed declarations, that it has become unaffordable and too burdensome.

“Distributed” Systems (Sewers)

Distributed Systems are being described by our bureaucracies and agencies as innovative sewers. A review of one such “sewer system,” written by the Georgia Tech Research Institute describes the use of separation chambers, dosing chambers, reaction chambers, pumps, transfer floats, aeration systems, alarms, and drainfields. They are not connected to any wastewater transfer pipes. Effluent is dispersed through a drainfield on the property. In fact, they appear to be nothing more than a different type of advanced system regardless of the “clever” name by which they are called.

Its rationale to be called a sewer is that, in some cases, this advanced septic system can be monitored and controlled using wi-fi. There is no information on residential field testing available. Their testing to receive an NSF rating for nitrogen reduction is ongoing. Therefore, performance, reliability, nutrient removal and costs are also not available.

System Options Compared

The following charts summarize and compare the various systems:


Ten years ago, the legislature provided FDOH with $5 million dollars to expedite the Innovative Process for septic systems, including non-electric designs. However, the innovative systems discussed above, although known at that time, were never included in the FDOH study. Instead, FDOH designed new systems that, to this day, cannot be purchased or installed because no commercial vendor has expressed interest. Companies that have sought to use Florida’s Innovative Permitting Approval Process have found it complex, expensive, and frustrating. As a result, the innovative solutions described here as well as others are not approved for use in Florida today. Yet these same technologies continue to offer other States affordable solutions for removing nitrogen from their ground water. Florida needs to move forward and encourage the development of as many commercial solutions as possible. Competition will lower the price to the consumer and will provide a cleaner environment for all to enjoy. Our State agencies must work to encourage innovation, not hinder its use.

Revised: 6/27/2019

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Dan Peterson


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