Opportunity abounds for precasters who stay ahead of changing wastewater landscape

Onsite wastewater systems are changing … and growing.

The past perception that onsite wastewater systems were merely a temporary solution, waiting for municipal wastewater infrastructure to catch up with residential areas, has shifted. Onsite wastewater systems are no longer seen as a stopgap measure; instead they are recognized as a solution, gaining increased attention and support from government agencies. The U.S. Environmental Protection Agency (EPA) has stated “decentralized systems are an integral component of our nation’s wastewater infrastructure and can protect public health and water quality.”

The EPA continues to reaffirm their commitment to decentralized wastewater solutions through their collaboration with state and local governments and national organizations to improve overall performance and management of decentralized systems. With a focus on community collaboration, technological innovation and environmental sustainability, the future of these systems appears brighter than ever.

Onsite Wastewater Systems Today

The typical residential wastewater system today is designed for a single residence. The influent (waste coming from the residence) flows into the tank, which is typically designed for a flow rate of 100-120 gallons per day per bedroom. The tank is sized to contain the influent long enough to have gravitational forces separate the lighter floating material like oils, fat and grease and the heavier sinking solids from the wastewater and also enable some biological treatment. The effluent (discharge from the tank) can then flow into a drain field (or leach field) to be processed by the bacteria and microbes in the soil to clean the water before finally flowing into the main water table or aquifer. The system is not typically designed to withstand any kind of traffic, and the drain field area is typically not available for any other purpose.

Some septic systems also include a secondary wastewater treatment chamber where microbes purify the wastewater in the tank before it flows out into the drain field. These microbes are classified as either aerobic, requiring oxygen to live and perform their duty, or anerobic, which requires a reduced oxygen environment to survive. This secondary chamber may be required by some jurisdictions.

Cluster/Community Systems: A Sustainable Approach

According to the EPA, more than one in five households in the U.S. depend on individual septic (decentralized) systems or small community cluster systems to treat their wastewater.
The recent pandemic and the subsequent increase in people working from home has also resulted in people migrating to rural areas. This is likely to further increase the number of people dependent on decentralized treatment systems.

With housing subdivisions growing and rising in popularity in non-sewered rural areas or semi-rural areas, housing developers are constructing residential dwellings in closer proximity to each other. In the past, the traditional septic tank and drain field solution was not always a viable solution due to reduced lot sizes or non-suitable soil for the drain field. However, thanks to the evolving onsite wastewater demand, new ideas like mass drain fields for community wastewater systems have arisen.

Community systems are designed slightly differently than the traditional septic system. Instead of having a complete treatment system for each house consisting of a septic tank and drain field, the communal system consists of each residence having their own septic tank but sharing a community drain field. From each individual septic tank, the effluent is transported by gravity or via pump system to the larger-sized communal secondary treatment tank. After secondary treatment, the effluent can now flow into a combined drain field, which is shared by all homes. This structure is advantageous for three primary reasons.

The first main benefit of this updated structure is that the community can optimally place the drain field. The permeability of the soil in the drain field is key to a properly working onsite wastewater disposal system. The proper permeability of healthy soil allows the removal of contaminants by natural biological, chemical and physical processes that are important for a properly functioning system. The speed with which the effluent travels through the soil is very important. If the speed is too fast, microbes in the soil will not be able to properly purify the effluent. If it is too slow, it will cause a “backflow” or backup, which is not only a messy situation but also a biohazard for the homeowner. Having the drain field on an individual property, like in the standard system, could cause issues if the correct soil composition is not available. A communal system is a great solution, since in the planning stages of the subdivision design, the correct location for the drain field can be established and the planner will only design one big drain field instead of one drain field per residence.

The second benefit of the community drain field is that it allows each property owner more freedom to lay out their property how they desire. No special care must be taken in placing the driveways, sheds, trees or shrubbery for fear of damaging the drain field due to the added weight or root systems. The positive side effect of a communal drain field is that the required size will create a significant green space in the subdivision, which can be used as a recreational park area.

The final primary benefit of the shared system is the shared cost for maintenance. It is hard to pinpoint the exact lifespan of a septic system since multiple factors including maintenance and usage play a role in a properly functioning septic system. According to the EPA, residential septic tanks are typically pumped every three to five years. In addition to the shared cost of maintenance, a community drain field often avoids the need for major repairs. The single residence drain field commonly is damaged by overloading the area due to parked cars on the drain field or other heavy equipment as well as wrongly planted landscaping by the homeowner, which causes root intrusion into the drain field. A community system organized and managed by a neighborhood program or a homeowner association (HOA) can eliminate these issues since the drain field is commonly located where no cars or heavy equipment will have access and landscaping is designed to accommodate the needs of a drain field.

Regulations Driving Technology

Stricter environmental regulations are another driving factor for change in the onsite wastewater sector. For example, Florida’s House Bill 1379, which was approved by Florida Gov. Ron DeSantis on May 30, 2023, stipulates where new construction can’t be connected to a central sewer system, the onsite wastewater treatment system must include an enhanced nutrient reducing system. This bill not only covers onsite wastewater treatment, but also wastewater facilities and requires them to be upgraded to advanced wastewater treatment if the discharge flows into an impaired waterway. New technologies are being introduced at industry specific trade shows to meet these new regulations, and it is exciting to see where all this innovation will lead.

As a result of the new regulations, many septic systems are enhanced with aerobic treatment. An aerobic treatment system relies on oxygen-dependent bacteria to break down organic matter. To achieve a suitable environment for the bacteria, oxygen is introduced using aeration in the tank. This aeration increases and encourages the growth of aerobic bacteria, which thrives in oxygen-rich environments. The treatment chamber usually has some sort of free floating or fixed media in it where the bacteria can attach itself to achieve an optimal distribution of bacteria. These innovations lead to a higher level of purification of the effluent in the water and the ability to meet the stricter environmental regulations. The cleaner effluent reduces demand on the final treatment by microbes and bacteria. This allows the system to be employed in soils where the ground water is higher as well as in less suitable soils. A more versatile system that doesn’t comprise longevity and cost-effectiveness while meeting stricter environmental regulations is a huge advantage for consumers, developers and community health entities.

Secondary treatment also can be achieved using biofiltration systems, which consist of tanks containing a porous filter media such as sand, foam, peat and other materials. This also involves the use of aerobic microbes as they attach themselves to the filter media and are supplied with air through vents in the system. Septic tank effluent is distributed over the filter media, and contaminants are removed by microbial activity and filtration as it trickles down through the media. The treated effluent is collected at the bottom, then sent to a disposal field for final treatment and dispersal.

A properly engineered and designed onsite wastewater system could be a big help in reducing potable water waste. This means not only a reduction of use of fresh water from our ecosystems, but also a reduction of energy needed to transport fresh water via pumps from its place of origin to the place of usage.

Longevity and Water Reduction: A Sustainable Solution

These changes and innovations in onsite wastewater treatment will provide additional opportunities to precast concrete manufacturers. As this type of wastewater treatment continues to gain acceptance, the use will continue to grow. The most important thing precasters can do is to continually strive to improve quality, honing the great characteristics precast is already known for.

Precast concrete structures are durable and long-lasting. Concrete strength and resiliency can withstand environmental factors and natural disasters like rising ground water levels, wildfires and aggressive soil conditions and wastewater characteristics. A precast wastewater structure has a considerably higher density than alternative materials, which will increase stability and resistance to buoyancy in high water table conditions. Another big advantage is the structural capacity of the precast tank. If backfill bedding contains large stones or other large material, these can produce severe point loads that could significantly damage wastewater structures. Precast concrete possesses the strength to better resist these types of loads. These advantages create a more sustainable structure by reducing the need for significant repairs or premature replacement.

Another sustainable attribute can be attained by using advanced purification so that the effluent can be used as non-potable water (grey water). This non-potable water is great for lawn irrigation and car washes. In our current times with fluctuating climate patterns and an increase in drought conditions, using recycled water is a sustainable solution to reduce the demand on drinking water while keeping a lawn green and a truck clean.

Non-potable water also can be rerouted into the dwelling through separate piping to flush toilets. Toilets commonly use about 31% of fresh drinking water consumption, which can make a tremendous impact on the environment. Consider most modern water-saving toilets are estimated to use about 9.1 gallons per person per day. Assuming a family of four, this would compute to an amount of roughly 40 gallons per day or 14,600 gallons each year. This is equivalent to the daily drinking water for 40 people, according to the medical expert recommendation to drink about
1 gallon of water daily. If you are assuming standard toilets in older homes, this usage could be four times as high.

These are just two examples of how onsite wastewater treatment systems can create a more sustainable future. Improvements and advances in technology as well as the ability to meet new regulations in environmental protection will strengthen the future of onsite wastewater treatment systems. These systems are here to stay!

Key takeaway

What does this mean for the precast industry?

Opportunity abounds. A steadily growing market, innovation to match the trends in regulations and a sustainable product means that precast manufacturers are positioned well to compete in the onsite wastewater market. However, precast manufacturers of wastewater structures must be engaged in the market and see which innovations are coming up to stay ahead of the game while being ready and flexible to adapt to changes.

Think about joining a local onsite wastewater or environmental association, participating at the NPCA Committee Meetings or reach out to NPCA to advocate for your improvement in the standards body, American Society of Testing and Materials (ASTM), or partake in ASTM meetings yourself, to be part in the decision-making process that will shape our industry. The future of onsite wastewater treatment offers lots of opportunities for expansion.