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Under Florida Statute Section 403.067 (7), the Florida Department of Environmental Protection (FDEP) conducts Basin Management Action Plans (BMAP’s) all over the state with the purpose of reducing nutrients that negatively impact water quality. In the Springs areas, BMAP’s are focused on eliminating septic systems which have been accused of contributing nitrogen to groundwater that feeds the springs. While we have legitimate objections to the underlying “science” behind these mandates, the process, with all its flaws, is moving forward, and the counties must develop a plan for eliminating conventional septic systems near Florida’s numerous springs.

According to the BMAP computer modeling process, counties must reduce nitrogen from existing septic systems by a calculated number of pounds. The counties will only get credit for reducing nitrogen from septic systems by planning and implementing projects on the BMAP approved list. To date, only municipal sewers (gravity or grinder) or Advanced Onsite Wastewater Treatment Systems (AOWTS) are allowed by FDEP’s BMAP. The list of “approved” AOWTS is supplied by the Department of Health, Bureau of Onsite Sewage. Presently, there are no passive nitrogen-reducing septic system alternatives on their list.

In a previous issue, we discussed grinder sewers. This issue, we discuss Advanced Onsite Wastewater Treatment Systems. Warning to our readers – this is long, complex, and annoying. But, so are the systems we are trying to describe. You are challenged to read to the end!

Quite simply, an AOWTS is your own personal wastewater treatment plant, powered by your own electricity. It is not connected to a municipal treatment facility. It collects waste, sends it in small “doses” through treatment chambers where bacteria and nitrogen are reduced. Basically, it does what your septic system does, but it requires electrical power to run the numerous pumps, circuits, floats, fans, sensors, filters, and alarms. The dosing process must be constant and consistent, and many mechanical and electrical components are necessary to accomplish the dosing function. In reviewing the literature provided by our state bureaucracies, we find the projected capital costs are largely under-estimated, and the inevitable and frequent service calls to keep systems running are not accounted for. For these reasons, family finances and lifestyle will be impacted.

  • “Dosing” is a pre-set volume distribution process interrupted by high or low water use. Events like large gatherings, house guests, or an unusually heavy laundry day can cause the system to malfunction, trigger alarms and require a service call. Vacations, when there is no use, can cause solids in the system to harden and the system will stop working. It’s advisable to keep the service call number on your speed dial.
  • Some AOWTS systems force waste and household water through a “bio-filter”. These systems will shut down when the treatment filter receives certain substances. Antibacterial soaps Clorox, grease, garbage disposal contents, some prescription drugs, and even chemotherapy drugs eliminated in the waste of cancer patients will shut down these “high performance” systems. Some industry professionals consider these systems unsuitable for use by the average homeowner and certainly not suitable for entire communities.
  • Costs displayed on the Dept. of Health approved AOWTS list state only the unit’s purchase price, which represents only a small part of the actual costs that can be incurred with the installation and operation of an AOWTS. Consider the following:
    • AOWTS typically must be designed by an engineer for specific site and usage conditions. Special permits are also required.
    • Homeowner’s electrical panel may need to be upgraded to accommodate power requirements. A panel typically costs $2,500 to $3,000.
    • Cost to remove old tank and drainfield, fill dirt to restore grade level.
    • Cost to restore landscaping and sprinkler systems, and the cost of additional landscaping to hide access ports and air intake protrusions.
    • Cost of frequent pump outs, state-required inspections and annual permits, state-required maintenance agreements.
    • Cost of labor and parts replacement not covered by maintenance agreements.
    • Cost of additional homeowners’ insurance riders to cover damage to home if a backup occurs.
  • Mechanical and operational risks are numerous and predictable. Multiple pumps, relays, alarms, floats, circuit boards, filters, valves, check valves, fans, etc. all need regular maintenance and replacement.
    • Numerous models to choose from, many of which are manufactured overseas. Spare parts may be problematic if vendors do not stock parts locally.
    • Warranty periods are typically short, so availability of parts and maintenance over a 10-15 year time frame is critical.
    • Designs that become obsolete or companies going out of business may mean you must replace the entire system and the $20,000- $40,000 capital cost is incurred again.
    • Trained maintenance technicians must be available 24-7. In the event of a major power outage, thousands of homes will need service calls. Your choice of a vendor is critical. Please note that in Key West and in other areas, vendors have simply abandoned maintenance contracts. Frequency of service calls made the contracts unprofitable. Homeowners had no choice but to learn how to service their own units. There was no consequence to the vendors.
    • Without power, AOWTS units will not work and units are designed to prohibit any override that would allow it to operate like a conventional septic system. Water and toilet use must stop altogether unless a gasoline powered generator is used or a battery backup is in place. A continuous operation, residential battery can cost +- $5,000. Generators, of course have their own risks and it should be verified by the contractor that this is a safe, workable option for your particular unit.
    • “Next-Generation” AOWTS that are monitored and maintained by county utilities over a WIFI connection to the home network are being promoted and tested in a study jointly funded by FDEP and the St. Johns Water Management District. Understand that access to your home network exposes your personal network to installers and service technicians. Ask Target how that worked out when the air conditioning company they called to service their store used a remote maintenance connection to the HVAC system, leaving open the access to Target’s network and the loss of personal data of millions of Target customers. Not many homeowners know how to secure their network. Just saying. Not convinced, read: US Department of Justice – Cybersecurity Unit Bulletin – Securing your Internet of Things Devices.

Do AOWTS actually reduce nitrogen? Will the BMAP water quality targets be met using assigned nitrogen reduction numbers? According to numerous literature and professional resources, the answer is a resounding NO. Testing these systems in a lab setting is vastly different that testing in the field, so National Sanitation Foundation (NSF) certification doesn’t mean much. This fact was stated several years ago in a publication authored by a well-known professional engineering firm, Hazen & Sawyer – “systems of this type (advanced systems) at individual homes do not perform as well as expected, especially for nitrogen removal.” 1

This was proven in the Keys where AOWTS were required because the Keys were designated an “area of critical concern.” Rigorous performance testing was completed and a report issued by FL Dept. of Health. 50% of the systems installed never met the nitrogen reduction target. 25% met them only occasionally. 25% performed as expected. It was an expensive, but failed experiment in septic system “remediation.” Not to worry, though. It was federal taxpayer dollars, not state tax dollars, that were wasted.

Information submitted to The Sludge Report by another industry professional gives this example:

“Regulatory oversight for advanced systems is time consuming, complicated, and expensive. Buzzard Bay, MA has one of the most rigorous and heavily managed advanced system programs in the United States. They have reported that the currently installed advanced systems remove about 50% of the incoming nitrogen about 75% of the time.”

After reviewing current Wekiva Springs basin data, this industry professional further commented,

“Recent studies conducted in the Wekiva Spring basin showed that “the majority (55 %) of the septic systems had a N attenuation of 52%, which closely matches the 50 % overall N attenuation rate used in previous (FDEP’s NSILT) calculations”. It also closely matches the advanced systems! If both types of systems were fairly assessed on how they perform in the real world in most cases the common septic system if properly permitted and maintained would be a clear choice.”

Editor’s note: In spite of the consistently poor nitrogen reduction results from AOWTS in the real world, the Dept. of Health uses vendor-provided lab results to calculate nitrogen reductions achieved by counties if they plan to replace septic systems with AOWTS. The county gets 100% credit for pounds reduced whether they plan for AOWTS or sewers. Check the box and close the books. Mission Accomplished! It’s obviously a numbers game that has nothing to do with reality.



  1. (Roeder, 2005; La Pine Oregon Demonstration Project, 2006), A Review of Nitrogen Loading and Treatment Performance Recommendations for Onsite Wastewater Treatment Systems (OWTS) in the Wekiva Study Area,” by Damann L. Anderson, P.E., of Hazen and Sawyer, P.C.,.