Here are some reasons we continue to recommend subsurface drip disposal:
Drip systems are easy to install.
Unlike traditional drain fields or chamber systems, SDDS don’t require major excavation or backfill. The flexible drip tubing can be vibraplowed into undisturbed dirt from a spool to a depth of around 8″1.
Photo credit: Geoflow
Subsurface drip systems can be installed in shallow soil.
Because they slow-rate apply water just below the soil’s surface, they can overcome some limiting conditions such as shallow depth to bedrock.
Drip disposal can be installed just above a seasonal high-water table2.
With the right level of pretreatment, some states allow as little as 6″ of separation between the bottom of the drip line and a seasonally wet soil layer.
Subsurface drip disposal fields can be smaller than traditional drain fields.
Aqua Tech’s wastewater systems clean the water before it reaches the ground. This means the dispersal system doesn’t have to do the cleaning.
The absence of organics in the discharged effluent eliminates the possibility of field failure3.
Because they’re shallow buried at the root line, up to 80% of the water is taken up into the grass cross and disposed via evapotranspiration. This takes some of the burden for water absorption off of the soil.
Drip systems can be configured for non-discharge or beneficial reuse applications.
Perhaps the greatest concern associated with the disposal of domestic wastewater into a subsurface disposal system is over nitrogen. When nitrate concentrations over 10 mg/L reach the aquifer, public health is threatened. If high concentrations of ammonia nitrogen reach a surface water way, environmental health can suffer. Fortunately, plants need nitrogen and phosphorus. Drip systems can be designed to eliminate the risk of contamination by these nutrients by distributing treated effluent to a crop at the rate of agronomic uptake per the table below. Between evapotranspiration and agronomic uptake of nutrients, drip systems can be configured to eliminate potential discharge of wastewater to the environment4
Other surface discharge systems such as spray or overland flow can serve this same function although they usually require more space and are more expensive than SDDS. ↩︎
While every state is different, you’ll need to know the answer to the following two questions to get a wastewater discharge permit:
Question 1: What kind of discharge will it be?
Your state will want to know how much water you intend to discharge, where it’s coming from (e.g. houses, stores, restaurants, etc.), where you plan to dispose of it, and how clean it will be when it’s disposed of. Most of the time, the level of required treatment will be determined by where it will be discharged. Here are some options:
Subsurface
With subsurface discharge systems, much of the treatment of the wastewater is performed in a disposal system such as a traditional septic drain field or sand mound. Generally speaking, these permits are the easiest to obtain because they count on established technologies that don’t require much operation or maintenance. However, discharges of large quantities of primarily treated wastewater have the potential to degrade quality of ground water. Many states impose an upper design flow limit on subsurface systems, or they require pretreatment of the wastewater before it is discharged to a drain field.
Some states such as Georgia and Connecticut have issued GeneralPermits that expedite the approval of subsurface discharges. Other states likeNorth Carolina and Tennessee have privatized the approval of large subsurface disposal systems.
Land Application
This might sound the same as subsurface discharge, but it’s not quite the same. Higher volumes of wastewater can be disposed under a Land Application permit. The water usually must be treated at least to secondary levels before disposal. Because of this pretreatment, Land Application permits can also include surface application such as with spray irrigation or overland flow. These disposal methods can overcome concerns over aquifer contamination associated with subsurface disposal systems. They also have some drawbacks related to a higher potential for public exposure to treated effluent.
Subsurface drip dispersal system illustration. Note the depth of the drip lines and the nutrient uptake into the grass.
Land application of treated sewer water can virtually eliminate the risk of environmental degradation. Because of this, these permits are sometimes referred to as “non discharge.” In most cases, applicants should consider disposal to the land first. Though, sometimes, this isn’t feasible where non-infiltrative soils or other environmental factors require large swaths of land and sizeable impoundments for the application and storage of treated effluent.
Direct (Surface Water) Discharge
Open discharge of treated domestic sewer water to a waterway must be permitted under the National Pollution Discharge Elimination System (NPDES) as administrated on the state level. Some states have their own version of the NPDES permit such as Texas’ TPDES, New York’s SPDES, and Arizona’s AZPDES permits. But a clean water law by any other name still smells like a challenge.
NPDES permits are notoriously difficult and time consuming to obtain. This reputation is more or less deserved from state to state. In states like Louisiana, and South Carolina that have general permits for open discharge, it’s less deserved. In states like Connecticut or California, it’s more deserved. Regardless of the state, though, open discharge systems must hit stringent treatment targets that must be maintained through vigilant monitoring.
A direct discharge system being installed in Branson, MO
Besides the difficulty of navigating the regulatory red tape, NPDES permits presume access to a waterway. And that waterway might have to meet certain criteria. Some states, like North Carolina, require that a stream can be proven to always provide some dilution to the treated discharge before an NPDES permit can be approved. Other states, like New York, allow discharges to intermittent waterways but require the effluent to be highly treated beforehand. Sometimes a discharge will be disallowed to a large waterway because it’s already polluted. Before an open discharge can be approved, a waste load allocation must be available from the EPA.
Beneficial Reuse
Treated sewer water can be reclaimed for a variety of uses that include dust reduction at construction sites, crop irrigation, or fire suppression. To qualify for these uses, the water must be treated to a very high level. In many cases, for instance, it must be disinfected until it is completely sterile. This level of treatment can make the wastewater system significantly more expensive than one designed for surface water discharge.
From 474 mg/L to 3 mg/L BOD5. This diagram shows the treatment process calculations along the way.
Aqua Tech’s BioTankcan hit reuse standards in every state. If you’d like an estimate on one, just click the button below:
In some states, such as Arizona and Montana, concern over aquifer recharge can make beneficial reuse a preferable option despite the higher cost.
All of these discharge details come under the “administrative” portion of any permit application. In most cases, you will need a state-licensed environmental engineer to fill out the administrative section of the wastewater permit.
Get an Engineer Referral
Aqua Tech doesn’t employ permitting engineers, but we know some great ones! If you need an engineer that can design and permit a wastewater treatment system, just let us know.
Speaking of engineers, while Aqua Tech performs the job-specific design engineering for each biological treatment reactor we sell, we count on local P.E.s to perform the overall design. These folks do the siting of the system and put everything together in one place. Which brings us to the second question to be answered on a wastewater discharge permit.
Question 2: How will you clean the sewer water?
The other side of the wastewater discharge permit coin is the technical section. Most of the time, state environmental agencies will have one team to review the administrative side of the permit and another to review the technical side.
Like skinning a cat, wastewater treatment can be performed in many ways. While your engineer will perform the overarching design, they might defer to the end user to select the preferred treatment technology. If you plan to permit a decentralized sewer system for a development or a town, it’s important that you participate in the selection of the technology. That’s because you’re the one paying for it and because you or someone do business with will be responsible for its performance over the long haul.
Here’s a small sample of the design documentation we provide:
Just as important as picking the right equipment is picking the right equipment provider. That’s because regardless of which engineer you engage for permitting, they will need to partner with the equipment provider to complete the technical section of the discharge application and their final engineering report. An incompetent or unresponsive equipment provider extend the permitting process at best. At worst, they can leave you holding the bag with a non-compliant treatment technology.
There are several companies of various sizes that provide wastewater treatment and disposal equipment. It’s always best to reach out to several for an initial discussion and budgetary price. We don’t mind a little competition, we know we have the best equipment and service for the best price!
You can call or email us directly to see for yourself.
Wastewater systems in the US are sized based on the maximum number of gallons per day they can treat.
A 300-room hotel, for instance, might require a 50,000 gallon-per-day system. Depending on soil loading rate*, that system might need a 2 acre drip field for effluent disposal.
Every component in our systems must account for design criteria.
Here are some factors that determine how many gallons per day your community septic or other wastewater system must be able to handle:
Capacity in gallons per day is determined by state and local design specifications.
These regulatory agencies calculate required treatment capacity in terms of maximum gallons used per person per day or maximum flow per bedroom per day, etc.
Commercial wastewater systems use more complex formulas that take their specific usage into account. The hotel mentioned above might need to account for 75 gallons per bed per day but might also have a restaurant and a bar attached for which another 12 gallons per seat per meal would have to be added.
Design criteria must also assume the level of pollution present within wastewater from different sources. Very dirty wastewater takes longer to treat which means systems must have higher capacity than what is released to give the system the time needed.
Here is an example of a design criteria matrix from an actual state regulatory agency:
Design criteria differ based on locality.
Design criteria tables such as the one above provide a starting point to determine size, but in most cases, regulatory agencies grant variances based on actual flow and treatment level.
We at Aqua Tech will research the design criteria required for your project and budget around them. As the build gets closer, we reevaluate your treatment needs and work with civil engineers and regulatory authorities to ensure regulatory compliance without excess expense.
Bottom line: Use this table to get a rough estimate. When you’re ready, let’s talk and get more specific.
*Soils differ in how much moisture they can absorb per hour. Very dense soil might only be able to absorb one tenth of a gallon per square foot every hour while porous soil can absorb almost a full gallon per square foot. Soil absorption per hour is called its “loading rate.” The higher the loading rate the smaller the drip field needed.
Wastewater can be treated in up to three stages generally known as primary, secondary, and tertiary treatment. Here’s what’s involved in each of these stages:
Primary Treatment
In this stage, heavy solids and grease are separated from the raw sewage through gravity and buoyancy respectively. A conventional septic tank is an example of primary treatment.
Secondary Treatment
The wastewater that leaves a septic tank or other primary treatment apparatus is still pretty contaminated with suspended solids and toxic chemicals such as ammonia. Secondary treatment systems use oxygen to facilitate natural digestion of contaminants by micro organisms already present in the wastewater. All municipal systems use secondary treatment.
Tertiary Treatment
Even though much cleaner, water leaving secondary treatment can still pose somewhat of a threat to the environment. To ensure complete protection of aquifers and watersheds, wastewater effluent can enter a third treatment stage. Tertiary treatment usually involves some sort of natural or chemical filtration/sanitization. Examples of tertiary treatment are constructed wetlands or drip irrigation fields.
Our systems use all three stages of wastewater treatment to equip you for responsible growth. Let us show you how!
Increased building density. They don’t require big drain fields on each lot.
Longer lasting. Land disposal through drip irrigation doesn’t become spent through built-up solids like septic leach fields.
Much better for the environment. Decentralized systems treat wastewater through accelerated natural processes, thereby eliminating water-borne pollution.
Advantages over municipal systems:
Sooo much cheaper! Decentralized systems reduce or eliminate the need for miles of large diameter pipe and lift stations.
No smell. Designed to be small and efficient, they treat so fast that there’s no detectable odor outside of a few feet from the system.
They facilitate development in growth areas without increasing tax burden or contributing to suburban sprawl.
They keep water in local aquifers rather than sending it downstream.
One of the biggest challenges to implementing comprehensive land use plans is how to accommodate new development in locally designated growth areas that do not have public sewers. Many rural and suburbanized towns in the US face this question.
They want to direct growth to the most suitable areas of town – near existing services, such as fire stations and schools, for example – but have no prospect of gaining access to public sewer lines. New development must rely on soils, usually on a lot by lot basis, to handle wastewater. The conventional wisdom says that means low densities of development, negating the effectiveness of a growth area. However, towns and counties without public sewer systems have options that they may not realize.
Additionally, watersheds in the United States reflect tremendous diversity of climatic conditions, geology, soils, and other factors that influence water flow, flora and fauna. There is equally great variation in historical experience, cultural expression, institutional arrangements, laws, policies and attitudes. With regards to wastewater issues, it would be a mistake to impose a standard model from the federal level to address the needs on a local level. Correspondingly, centralized sewer systems are aging, frequently underfunded with respect to replacement costs and expensive to maintain. In addition, centralized sewer strategies are increasingly challenged by environmental and social considerations such as inter-basin transfer issues, aquifer depletion, nutrient loading and urban sprawl.
Decentralized wastewater management has the potential to be the catalyst for the re-creation of our institutions, to support a new agenda, and for rapidly building a flexible infrastructure to sustain the integrity of the natural systems that are essential to a healthy economy.
Tom Bartlett – founder and Ceo of aqua Tech
The new emerging civic agenda of smart growth, community preservation, open space planning, ecologically sound economic development, resource conservation, and watershed management demands that we rethink what constitutes assets and liabilities. With a capacity of roughly 200,000 gallons per day, these off-grid plants can be constructed at a cost of well under $3,000 per home. These are economic, environmental and quality of life issues and they do not lend themselves to single purpose solutions. They require local community based consideration within the context of flexible multipurpose planning.
Statistics have shown us that within the U.S., twenty-five percent of existing residential real estate and forty-seven percent of new construction are served by onsite treatment systems. Many of these systems are acknowledged to be inadequate with respect to soil absorption, nutrient removal, resource protection and public health. Ironically, despite these statistics and EPA policy changes, most regulatory codes as well as most municipal and commercial planning continue to consider onsite systems to be temporary solutions awaiting a centralized sewer hookup.
Looking beyond the traditional assumption that wastewater is simply a matter of safe disposal and the public health; the real contemporary wastewater issues are the economic and environmental issues in which the public has a primary interest:
Drinking water quality
Deterioration of recreational water resources and other natural systems services
Property Values
Economic development in small and rural communities
Urban sprawl
Beyond just disposal, decentralized wastewater management has the potential to contribute to the formation of an infrastructure to sustain watershed integrity. Decentralized wastewater treatment serves the “watershed agenda” and the principles of “community preservation” and “sustainable development.”
When approaches to the larger wastewater issues are successfully accomplished everyone benefits:
Local communities win open space zoning, water quality and supply protection, increased development capacity and an expanding tax base.
Natural systems are sustained through prudent zoning and reduction of non-point pollution.
Developers win additional lots for development and higher margins typically associated with conservation subdivision design and municipal infrastructure.
Regulatory agencies win because they gain partners in compliance management such as the municipality and perhaps a watershed authority.
Citizens and homeowners win because property values are enhanced as schools, healthcare providers, and retail outlets crop up around the new infrastructure which decentralized systems provide.
There are no major obstacles to a decentralized infrastructure for wastewater treatment.
New technologies in a properly managed context provide the opportunity for a land based watershed initiative that could significantly reduce small flow point source discharges such as those associated with onsite treatment systems. A decentralized wastewater management infrastructure should include:
Clustered, performance-based, decentralized wastewater management systems
Industrial & commercial pretreatment prior to discharge to existing sewage treatment systems
Wastewater reuse systems
Estimates suggest that this infrastructure is achievable with technologies that require 50% to 70% less space with corresponding reductions in cost of 40% to 50%. For citizens in small and rural communities these reductions represent opportunities to preserve water quality, to stimulate economic development and job formation and to restore property values. Essentially, we are shifting from large sewage collection systems and centralized treatment plants to small and decentralized management systems. Keep in mind also that this is not an alternative to centralized sewer. Rather, it is a complimentary adjunct to the existing infrastructure.
Moreover, the decentralized solution is coming from local community and watershed needs. It is not coming from the bureaucracy. It is essentially good old bottom-up American pragmatism. It is important, therefore, that the general population becomes informed about the benefits of the decentralized approach. We must find a suitable mechanism to accelerate the progress to support watershed management. If we can not find such a mechanism, we run the risk of letting the limited existing strategies (centralized and onsite) dominate the next 20 to 30 year cycle.
With every project being considered for an Aqua Tech System, planners must consider many factors in the selection of an appropriate site specific wastewater collection system.
Such as:
Housing density and road frontage
Size of the project and wastewater volume to be conveyed
Topography and sensitive natural resources
Depth to bedrock or groundwater
Distance to the wastewater treatment and dispersal site
The Settling Tank getting a final inspection
During the design process of your system the following methods should be considered:
Conventional gravity systems (with lift stations as required)
Septic Tank Effluent Gravity (STEG) system (AKA small diameter gravity sewers)
These collection or conveyance systems often represent the major portion of the total capital cost associated with any wastewater system, so careful consideration should be made to avoid extraneous expense while also ensuring reliability and environmental compliance.
Let us help you design a system that takes everything into account.
Several places around the US are currently experiencing a construction boom and we’re delighted to be a part of it. Here’s a mixed use system that our engineers have just designed.
This system is designed to treat 37,000 gallons of wastewater per day.
This particular system was designed to treat residential and commercial wastewater at the same time. Notice that the effluent (outflow) discharges at ground level. This is a septic system with no leach field!
Here’s the secret:
This private wastewater treatment plant removes nearly all of the Biological Oxygen Demand (BOD), Total Suspended Solids (TSS), and Total Nitrogen (TN).
