Can A Septic Tank Float?

As crazy as it might sound, the answer is yes: Septic tanks can float out of the ground. Any buried structure will float when empty if it weighs less than the water that displaces it. That means that when installing any sort of septic system in an area with a high water table and/or that is prone to flooding, you must conduct buoyancy tests and determine if the system will remain stable.

Dr. Sara Heger, instructor at the University of Minnesota’s Onsite Sewage Treatment Program, has broken down the calculation to determine tank stability at Onsite Installer. The basic steps are below, but Dr. Heger’s walk-through explains each step in detail and shows example calculations. You will need to know the individual weights of the following: the empty tank, the minimum amount of water and media in the tank, the soil directly above the tank, and the maximum volume of water that is displaced.

Here’s the calculation:

1. Calculate the weight of water displaced by the tank (buoyant force B).
2. Calculate or look up the weight of the tank (WT).
3. Calculate the weight of the water in the tank (WW).
4. Calculate the weight of the soil cover (WS).
5. Evaluation of net forces.

So if your calculations indicate that the tank will float, what do you do then? Thankfully, there are anti-floatation measures that can be added to the system design plans. Perhaps the most basic is to use concrete, which weighs 85 pounds per cubic foot and can be added into the design in a few different ways. Some fiberglass tanks may also have an anti-floatation lip built onto them.

It’s important to consider that any anti-floatation measure will increase stress forces on the tank, so the tanks must be able to withstand the extra force. Read more from Dr. Heger at Onsite Installer on anti-floatation.

If you ever do need to deal with a flooded septic system, whether the tank has emerged from the ground or not, refer here:

• “Faced with a Flooded Septic System?” also from Dr. Heger at Onsite Installer
• “Protecting a Septic System During and After a Flood” at WaterOperator.org
• Contact the Onsite Sewage Treatment Program at UMinn.

Businesses on Septic Systems

If a business is in an area that does not have a public sewer system, or, if the business will generate a higher flow of additional wastewater than a sewer system will be able to handle, a commercial septic system will be necessary. This type of system, also called a large-capacity septic system, is defined by the U.S. Environmental Protection Agency as "a septic system that receives solely sanitary waste from either multiple dwellings or a non-residential establishment that has the capacity to serve 20 or more people per day."

The wide variety of facility types that a large-capacity system could service include schools, religious institutions, office and commercial buildings, shopping malls, hotels, restaurants, convenience stores, and more. Unlike residential septic systems or non-residential systems serving fewer than 20 people per day, the EPA does regulate large-capacity systems in order to protect underground drinking water sources.

Fundamentally, though, a septic system on a business property works in much the same way as a residential system, just on a larger scale. To keep up with the higher volume of wastewater the system will be handling, large systems will require more frequent pumping, maintenance, and service to ensure they operate properly for as long as possible. Business owners managing water use so that the system is not overwhelmed will also help keep the system in good working order.

Again, similarly to residential systems but on a larger scale, the costs of both installation and operating large-capacity systems will vary widely based on the individual factors of the commercial location and performance needs for the system.  

There are some differences to keep in mind for large-capacity systems. While these systems still only handle sanitary waste (so no industrial waste allowed), there are still different types of wastes produced by commercial buildings that their large-capacity septic systems will need to be able to handle. So they’ll need additional design components — such as grease traps in restaurants to keep fats, oils, and greases (the notorious FOG!) from clogging up the plumbing — and more specialized maintenance and service.

Multiple types of septic systems can be used for a commercial installation. AAA Pumping Service recommends sand filter systems, pressure distribution systems, evapotranspiration absorption systems, and cluster systems as well-suited for commercial properties. (A cluster system would serve multiple nearby businesses/commercial properties).

Note: Mention of commercial entities who share educational information does not constitute an endorsement.

Additional Reading

• Large-Capacity Septic Systems | U.S. EPA
• Best Septic Systems for Your Commercial Property | AAA Pumping Service
• Five Facts About Commercial Septic Systems | Moon Site & Septic
• Five Things to Know About Commercial Septic Systems | World Construction Today
• “Design Concerns with Restaurants, Convenience Stores, and Commercial Waste” Presentation | Onsite Installer

Nutrient Control for Wastewater Treatment Plants

The control of the discharge of nutrients (nitrogen and phosphorus) from municipal wastewater treatment plants is critically important to the achievement of the water quality goals of the Clean Water Act. Through National Pollutant Discharge Elimination System (NPDES) permits, effluent limitations on the concentrations of nutrients are set to support designated uses, based on state water quality standards.

We have 479 resources (and counting) on Nutrient Control in our Documents Database that provide valuable information on this topic. You can search for documents about resource recovery as a viable nutrient control alternative, phosphorus removal, costs associated with nutrient pollution, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Nutrient Control within our database just select "CATEGORY" in the dropdown then choose "Nutrient Control." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

Webinar Recording: Cybersecurity for Wastewater Operators

Watch this webinar recording to discover some of the most helpful cybersecurity resources and to learn how to use our search tools at WaterOperator.org to find additional resources and training events. This is the first webinar in our new series for wastewater operators!

The webinar answers questions such as:

• What is WaterOperator.org and how is it a useful tool for wastewater professionals?
• What are the best resources we have relating to cybersecurity in the water and wastewater sector?
• How can you find more cybersecurity resources and other similar resources on WaterOperator.org?

This free series will cover topics relevant to wastewater operators, including funding, asset management, compliance, and water quality. Upcoming events in the series include:

• Source Water Protection for Communities with Decentralized Wastewater (April 23)
• Funding Wastewater Infrastructure Projects (June 25)

Certificates of attendance for each session will be delivered upon request. Check with your certification body for acceptance criteria.

Here is the recording of the first webinar, held in February 2024. We cannot provide certificates of attendance for watching the webinar recording.

Biosolids & Activated Sludge Treatment

Biosolids are the nutrient-rich organic materials resulting from the treatment of sewage sludge. Often times, they are the solids removed from the bottom of a lagoon, that are applied to farm fields as fertilizer.

We have 379 resources (and counting) on Biosolids in our Documents Database that provide valuable information on this topic. You can search for documents that cover the types of lagoon sludge and how to calculate sludge volume and the volatile portion, what are nutrients and how they are removed, how to deal with accumulated sludge in a wastewater lagoon, and many other useful guides that will help you to deliver safe and clean water to utility customers. 

To access the wealth of knowledge on Biosolids within our database just select "CATEGORY" in the dropdown then choose "Biosolids." Once you make that selection, a second dropdown will appear where you can choose "HOST," “TYPE,” or “STATE” to narrow the search even further. If you have a specific search term in mind, use the “Keyword Filter” search bar on the right side of the screen.

This is part of our A-Z for Operators series.

FOG in Sewer Systems vs. Septic Systems

The use of FOG (fats, oils, and grease) in the average household typically cannot be avoided. Once these substances are rinsed or flushed down the drain, they have the potential to build up and create blockages within the pipes of the home. When these clogs form they can cause a variety of problems like: raw sewage backing up into the property, basement flooding, raw sewage overflowing into public spaces like parks, streets, rivers, etc., and increased maintenance costs to clean and repair damaged pipes.

It is important to make sure that community members are educated on ways to avoid the damage that can be done when these substances are not handled properly. Here are some ways you can educate the public on FOG:

Dos and Don’ts 

• Consider providing a dos and don’ts list, pamphlet, or flyer to community members outlining best practices for handling FOG substances. The Texas Commission on Environmental Quality (TCEQ) created a poster that does this well.
• For outreach to non-community water systems, specifically restaurants, there are resources that can be provided like this FOG Toolkit from the National Restaurant Association’s Conserve Program. You can also collaborate with your local health department on educational materials to distribute.

Recycle

• If your area has a Household Hazardous Waste program that accepts used cooking oil, provide the contact information to community members or consider hosting a collection event. For an example of how to provide this resource, TCEQ has a webpage with more information. If there is no program available, contact your local Solid Waste Authority for specifics on their recycling program.

SepticSmart

• For homeowners that use septic systems, provide information about EPA’s SepticSmart program. Not only does this program include insights on how FOG impacts a septic system, but it also provides valuable information on general septic maintenance.

Videos

• Nobody forgets the first time they see a "fatberg" and it can be helpful to trigger awareness and a potential behavior change. There are plenty of videos online so choose one that best represents your system to share with utility customers.

Providing resources like the ones above will help to ensure your ratepayers understand the importance of these best practices.
 

Hurricane Preparedness for Wastewater Facilities

As Hurricane Ian left swaths of Florida without water and wastewater services at the end of September, the New York Times was already reporting on potential environmental impacts of the storm hitting South Carolina. Beyond the acute hazards of exposure to untreated wastewater, the biggest concern in hurricane-impacted areas is nutrient pollution and the potential for harmful algal blooms.

As extreme weather events impact larger stretches of the country, the water sector (including regional watershed protection entities) will need to anticipate greater consequences in the emergency response planning process. Florida DEP's Hurricane Preparedness for Domestic Wastewater Facilities and FEMA's Hurricane and Flood Mitigation Handbook for Public Facilities offer some helpful recommendations.

FEMA divides its recommended (primarily anticipatory) mitigation strategies into four categories: elevate or relocate, protect or divert, floodproof, provide redundant systems. The fact sheet identifies which of these strategies are appropriate for each major component of a wastewater facility. For example, installing "backflow prevention devices such as valves on lines that flow into the lift station and emergency overflow lines" is an option for floodproofing a lift station.

FEMA also provides a similar framework for drinking water systems.

Florida DEP's suggestions for before and after a hurricane can provide an update to an existing baseline checklist, particularly for minimizing these concerning downstream impacts. For example, it is recommended to "drain wastewater holding ponds as completely as practical after receiving a hurricane warning" as well as ensure that biosolids for land application have been "spread or stored in a secure manner."

With the frequency and severity of hurricanes and other extreme weather events increasing, facilities may need to adopt new strategies to prevent costly cleanup efforts and even legal battles.

Additional Resources for Management of Dissolved Oxygen in Activated Sludge Plants

Below is a list of free resources on the management of dissolved oxygen in activated sludge plants to supplement our previous article Managing Dissolved Oxygen in Activated Sludge Plants. 

Troubleshooting Noncompliance at Small Wastewater Treatment Plants

This is a 171-page presentation from the Ohio EPA on Troubleshooting Noncompliance at Small Wastewater Treatment Plants that features information on activated sludge process control.  

Operating Tools and Measurement Techniques for Troubleshooting Activated Sludge Systems

This 29-slide presentation discusses tools that can be used to troubleshoot activated sludge systems. The presentation will introduce some simple tools, talk about some that are a little more advanced, and show operators that this is not the realm of only the laboratory or the engineer.

Activated Sludge Process Control Manual

This is a 106-page Activated Sludge Training Manual that was prepared by the Michigan Department of Environmental Quality with information on operating the activated sludge process, including nutrient removal, and troubleshooting. 

Holistic Aeration and Chemical Optimization Saves Big Money from 1 MGD to 600 MGD

This 36-slide presentation outlines automated dissolved oxygen control, which includes reduced operator labor/attention, improved process stability, and energy savings; automated biomass control; and automated chemical feed control for P removal, which includes a 95 percent reduction in chemical usage. 

Troubleshooting Activated Sludge Processes

This 32-slide presentation discusses how to troubleshoot activated sludge processes and covers process types & kinetics, influent monitoring, process monitoring, and control and nitrification.

Convert Activated Sludge to BPR

This 48-slide presentation discusses improving Bio-P performance by getting to know the system, initial assessment, expanding a zone for increased BPR performance, learning D.O. control, and more.

Efficient Nutrient Removal under Low Dissolved Oxygen Concentrations

This 25-slide presentation discusses the City of St. Petersburg Southwest WRF, City of Rochester WWTF, and more. 

Activated Sludge- It’s About Efficiency and Optimization

Doom & Bloom: Biochemical Oxygen Demand (BOD) in Wastewater Treatment

This website from the Environmental Finance Center Network provides an overview of the function of biochemical oxygen demand in wastewater treatment plants. 

A Tale of Two Filaments: BNR System Recovery from a Major Process Upset

This 7-page article discusses the Glendale Wastewater Treatment Plant in Lakeland, Florida that had a power outage that caused the dissolved oxygen concentrations in the aeration basins to drop very low. 

These resources and more can be found in our document library.

COVID-19 in Wastewater Surveillance

Over the past two years, researchers have turned to wastewater to find out more about the trajectory of the COVID-19 pandemic.

In September of 2020 the CDC developed the National Wastewater Surveillance System (NWSS) to help monitor and better understand the spread of COVID-19 throughout communities. The NWSS works directly with public health departments to track the presence of the SARS-CoV-2 virus in the wastewater of communities across the country. They are able to do this because humans infected with the SARS-CoV-2 virus shed the virus in their feces making it detectable within community wastewater systems. The CDC has been able to gather a large amount of data because 80 percent of households in the United States are served by municipal wastewater collection systems. Wastewater surveillance programs have been implemented across the country in places like Utah, Washington D.C., Massachusetts, Connecticut, and Illinois. Programs have also been implemented internationally. 

Wastewater surveillance technology has proven to be very beneficial to communities because it is able to detect the virus even before people start showing symptoms. This is helpful because once health departments are aware, communities can immediately take stricter precautions to prevent the spread of the virus. You can stay up to date on the presence of COVID-19 in your community by checking the COVID Data Tracker which provides regularly updated information on the presence of SARS-CoV-2 levels in wastewater at testing sites across the country. 

SURE! Sustainable Utilities Research and Education

SURE! is a program within the Cal Poly School of Civil and Environmental Engineering that seeks to find solutions within the water-energy nexus that will provide sustainable solutions to wastewater recycling and resource recovery. The mission of the SURE! program is to help expand the wastewater recycling workforce and develop new sustainable technologies. The program received a WEF award for its commitment to water treatment education and research. The SURE team has worked on algae-based wastewater treatment, algae biofuels, conversion of wastewater solids to energy, potable re-use, and dairy wastewater treatment.