REMEDIATING Man-Made Wastewater Through Septic to Sewer Conversion

THE MANDATE

Basin Management Action Plans mandate remediating septic systems in certain areas of Florida.

One option is to replace one’s conventional, passive (non-electric) system with a nitrogen-reducing system (electricity dependent) , often called an “advanced” system. CPR’s comparative study on replacement septic-system options can been found at http://www.cpr-fl.org/remediating-nitrogen-from-septic-systems/.

The other option is to connect homes (and businesses) to a sewer system where possible. In this article, CPR-FL compares these sewer options so that you may be better informed and help your community decide what is best for itself.

OPTION ONE – THE TRADITIONAL SEWER SYSTEM

A sewer system or sanitary sewer transfers raw sewage by gravity from the source (home) to an underground system of piping, leading to a wastewater treatment plant where it is treated. Where the natural topography of land does not always allow gravity to move sewage to the feeder lines, lift stations (pumps) are built to move sewage through the system to the treatment plant.

Most sewer systems are owned, operated, and maintained by local governments. Customers pay a monthly “rate” for this service; rates are approved by the Public Service Commission.

At the treatment plant, several steps are taken to treat the sewage and purify it before it is returned to the environment:

  1. Trash and other large particles (debris) are separated out.
  2. Remaining solids (biosolids) and separated from liquid effluent.
  3. Biosolids are treated and sold for fertilizer or taken to landfills. (called cake, biosolids contain nitrogen and phosphorus)
  4. The remaining effluent is disinfected to remove bacteria and chemically treated to remove nutrients.
  5. The treated effluent is released back into the environment.

Converting Septic Systems to Sewers

Conversion to a traditional sewer system means laying underground sewer mains to a neighborhood and then laying sewer pipes throughout that neighborhood so that each home, in turn, can be connected.

This involved digging trenches and laying PVC piping, typically in rights-of-way. It can be disruptive to landscaping and traffic while work is being done. Introducing sewers to an existing neighborhood is expensive, costing an average of $20,000 per home, depending on the amount of pipe that must be laid, and the number of lift stations required. The homeowner cost to connect his home to the sewer feeder line averages $5,000, plus the monthly sewer bill which varies from city to city.

Florida Facts About Traditional Systems

Approximately two-thirds of the public are served by traditional sewer systems. Florida has approximately 2,000 sewer domestic wastewater treatment facilities which are permitted by the Florida Department of Environmental Protection (FDEP). Each day, these systems treat 1.5 billion gallons of wastewater and reclaim 800+ million gallons of water. These systems have capacities that vary greatly, but, combined, they have a capacity to treat 2.7 billion gallons per day. In addition to these facilities, there are 2,300 industrial wastewater facilities.

Critical Issues Concerning Existing Traditional Sewer Systems

Over the past decade, 23,000 sewage spills have occurred in Florida. As a result, 1.6 billion gallons of wastewater have been released to the environment (either into waterways or onto land) due to failing sewer lines, lift stations, and municipal plants. More than 370 million gallons of that number were completely untreated. (Source: Florida Department of Environmental Protection)

Two aspects of sewer infrastructure need to be addressed if pollution is to be remediated.

Aging Sewer Lines

No matter how updated a wastewater treatment plant may be, if the sewage is not delivered to the plant, it becomes a health and environmental problem. Aging sewer pipes have a devastating impact on the environment in three ways:

Failure – The Cities of Ft. Lauderdale and Jacksonville, and the Tampa Bay/St. Petersburg region have painful first-hand knowledge of this problem. In recent years in Ft, Lauderdale, failing sewer pipes have released more than 20 million gallons of raw sewage into their waterways and city. In the Tampa Bay area, failing and clogged sewer pipes have contributed to tens of millions of gallons of sewage escaping into the environment.

Infiltration – when rains are heavy, stormwater infiltrates and overloads sewer pipes, causing them to break. Infiltration can also overwhelm lift stations and treatment plant capacities. Municipal plants have no choice but to dump untreated or partially treated sewage or risk catastrophic damage to the facility. Infiltration is responsible for spewing millions of gallons of sewage onto the ground and into streets and waterways.

Exfiltration – In many Florida cities, underground pipes are well over 50 years old, and aged pipes leak raw sewage into the environment. It is estimated that 10 percent and more of the raw sewage flowing through aged systems is exfiltrated directly into groundwater and the environment. (http://blog.envirosight.com/a-brief-history-of-pipe-materials) In a city like St. Petersburg, which has a capacity of 56 million gallons per day, 5.6 million gallons could be leaking into the environment every day.

It’s ironic and counterproductive that BMAP remediation plans do not acknowledge the environmental impact of aging sewer pipes. If “leaking” septic tanks are a threat to groundwater, then leaking sewer pipes are as well. However, aging sewer pipes are not considered a “source” of nutrient pollution, rather FDEP and BMAP define sewer pipes as a “transport”, and therefore, not eligible to receive funding or credit for environmental remediation. Remediating sewer systems should be the starting place to protect the public’s health and the environment from infectious bacteria and excessive nutrients.

Aging Facilities & Treatment Plants

Every treatment plant has a capacity. Under normal conditions, treated wastewater is released back into the environment through surface waters, deep aquifer injection wells, percolation ponds, and spray fields.

When that capacity is exceeded, usually due to heavy rain events and/or power outages, raw sewage and partially treated sewage overflows into the environment. In order to keep up with increased amounts of wastewater and stormwater, plants are “forced” to release or outflow untreated or partially treated wastewater into rivers or other water bodies. Power outages have an acute effect on a system because lift stations pumping wastewater to the treatment plant can stop pumping. Wastewater, then, backs up in sewer pipes forcing raw sewage to be discharged through manholes and onto streets.

Florida has been upgrading wastewater treatment plants to handle more capacity and treat wastewater to reduce nutrients. Many still need upgrades.

SUMMARY

In summary, converting septic systems to sewer systems in established neighborhoods is expensive and messy. Consideration should be given to treatment plant capacity lest the added sewage demands overload the system. The condition of sewer feeder lines and mains should also be considered. Newer systems with newer pipes offer longevity and environmental protection.

OPTION TWO: The Grinder System

Grinders, also called low pressure sewers, were originally developed to help homeowners who add additional bathrooms to their structures. When gravity cannot move the waste from the add-on bathroom, a macerating pump inside a small tank operates like a garbage disposer. It grinds the raw sewage into liquid and moves it into the already existing sewer line or septic system.

More recently, counties and cities are using grinders to chain-link whole neighborhoods to a municipal sewer system.

A grinder sewer system consists of a small tank capable of holding approximately 250 gallons (capacity varies with models) of water and sewage. For the average home, this is a one-day capacity of waste and water usage. Grinders use a submersible macerating pump, several floats to trigger the pump out action, relays to manage the starting and stopping of a 2+ horsepower motor, alarms, warning lights and override switches, and the very important mechanical check valve to stop waste from backing up into your home. The design requires continuous use and requires a cleanout action and filling of water when left unattended for long periods of time such as vacation or seasonal use.

Their installation costs are low enough to be borne by homeowners ($10K+) and only require a small diameter pipe to connect to existing nearby sewer lines. Although lift stations are still needed, municipalities can install grinders for approximately one-half the cost of gravity-fed, traditional sewers and with much less disruption to the neighborhood. The same sewer rates apply whether gravity fed or grinder systems. However, since the pump exists on private property, the cost of repairing the grinder pump is typically paid for by the homeowner.

Although relatively inexpensive, the average grinder is a very complex mechanism that operates in a highly corrosive, raw waste environment. Average life expectancy of a grinder pump is 3-5 years. Even when there is power, these components are known as maintenance nightmares, especially if high-quality materials like stainless steel have not been used throughout.

It should be noted that without power, they will not work and may overflow into homes or yards. Everglades City is but one place that learned this the hard way when the city lost power prior to and during the landfall of Hurricane Irma (See article on Everglades City)

SUMMARY

The use of grinders is a less expensive conversion option than the traditional system. However, in the event that electricity is lost, the system is rendered unusable. Attempts to use the system without electricity can produce an environmental disaster as experienced by Everglades City.

OPTION THREE: The Septic Tank Effluent Pump (STEP) System – A Hybrid System

The City of Vero Beach has been a pioneer installing STEP systems. Here’s how it operates.

The existing septic tank and drainfield are replaced with two plastic replacement tanks. The first tank replaces the septic tank and all wastewater flows into it using gravity. For an average family, this tank has a capacity of 1,060 gallons.

It is here where solids are separated from liquids (effluent). Using gravity, the effluent flows from the larger tank into the second smaller tank with a 500-gallon capacity.

Periodically, a simple water pump inside this tank moves the liquid from the small tank into a 1” line connected to a 2” line at the street. From there it is delivered to a 4” main line and on to the wastewater treatment plant.

If electricity is temporarily lost, the system continues to operate by gravity. If power is expected to be lost indefinitely due to an on-coming storm, the control box placed, on an outdoor wall, allows an owner to flip a switch to turn on the pump emptying the 500-gallon tank and allowing the system to be used without power for a longer period. A generator can easily be plugged into the system during a power outage allowing the 500-gallon tank to be emptied if needed.


THE COST OF STEP

In a case study of Vero Beach, approximately 1,500 residents were on septic systems. The conversion to a traditional gravity sewer system was estimated to be approximately $22.5 million. The additional costs of connecting the residents to sewers was to be an additional $18 – $22.5 million.

Using the STEP system, the build out of the infrastructure for residences was estimated to be $11.0 million and the residential connections costs were less than $1.0 million.

The City initiated the conversion by determining the order of which neighborhoods were to be converted. It then informed residents of the initial neighborhoods of the plan and start date. For a typical three-bedroom house, the cost to a homeowner to connect is $7930. However, if residents connect within one year of the neighborhood start date and pay in full up front, they receive an incentive credit of $3,390. The incentive brings the cost to the homeowner down to $4,540. Since 2015, 350 residents have converted and most pay in full. More importantly, they are pleased with the results.

SUMMARY

The city’s Water and Sewer Department have designed a low cost and reliable solution for septic system conversion. For those who are environmentally concerned, 100% of all nutrients enter the sewer system, not the environment. For residents desiring to watch their budgets, once installed, the monthly sewer bill averages $37/month. Components used in the system are quality and long-lasting, and, the city is responsible for the maintenance of the system. More details are available at the city’s website:
https://www.covb.org/187/Septic-Tank-Effluent-Pump-STEP-System

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Dan Peterson

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