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.
Aqua Tech’s biological process carries out complete sewer sludge treatment eliminating the need for a clarifier.
This sewer sludge treatment is based on biofilm technology. Biofilm is a dense community of attached-growth microorganisms living on specially designed plastic media. Having direct contact with wastewater, biofilm absorbs and oxidizes pollutants thus providing treatment. Multiple biozones ensure that an appropriate biological system develops according to the nature of wastewater composition. It supports dynamic balance on its own both in mass and qualitative composition according to variations of wastewater parameters (within the range of optimal adaptation rates and allowable values of design loadings).
Multi-Chamber Design
Multiple chambers in our bioreactor create a series of ecosystems in which the excess biomass is digested and mineralized in successive chambers by higher level microorganisms. This process converts organic sludge into carbon dioxide, water and inorganic elements.
Each chamber houses specialized media to host the required microorganisms.
The first chamber of the bioreactor houses a smooth-surface floating media. The smooth surface coupled with high turbulence in the first chamber prevents high biofilm accumulation on the media.
Sloughed biofilm travels into the next chamber to be consumed by protozoa inhabiting porous media (Bio-Chip).
The Bio-Chip media mitigates biofilm overgrowth as the chips rub against each other under aeration. These unfavorable conditions on the outside of the Bio-Chip cause microorganisms to inhabit primarily the protected interior of the media. Treatment in this chamber is provided by slow-growing bacteria such as ANAMMOX which produce negligible biomass.
Subsequent chambers facilitate the development of a complete trophic system with all four trophic levels. This means that the amount of bacteria are controlled by Protozoa and Metazoans that consume any surplus bacterial biomass.
The last chamber utilizes static media and minimal aeration intensity to ensuring high efficiency adsorption and mineralization of any residual suspended matter.
The above described is the conceptual model or ideology of the bioreactors which does not change if a bioreactor has just two or three chambers. Thus, any our biological process is designed so that effluent biomass amount is within the required effluent limit for TSS.
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.
Secondary wastewater treatment uses natural biological processes to protect the environment from contaminants in sewage.
Wastewater poses several threats to the environment. Microorganisms use oxygen to digest the organic matter in sewage. The rate of this digestion can be measured as Biological Oxygen Demand (BOD). Water with high BOD can deplete dissolved oxygen in waterways thereby suffocating wildlife.
A common septic tank design
Septic tanks use gravity to settle out around 70% of wastewater solids. This settling is called “primary treatment.” The other 30% of solids remain in the wastewater and flow out into the environment. We measure this component of wastewater as total suspended solids (TSS). Primary treatment achieves only a 30% reduction in BOD. While better than nothing, septic systems discharge contaminated wastewater into the environment via a drain field. Larger flows, higher strength wastewater, or poor site conditions can require further treatment to protect the environment.
Enter the secondary wastewater treatment system.
While technologies vary, all secondary wastewater treatment systems use oxygen to accelerate the bacterial consumption of organics. Aqua Tech recommends and sells MBBR (moving bed biofilm reactors). MBBR technology is the most recent innovation in wastewater treatment systems. These biological reactors can treat to a high standard with virtually no operational time or recurring costs. And our MBBR’s are the best on the market.
All MBBR’s host a bacterial slime layer on a plastic media of some kind. Wastewater treatment takes place where that slime layer contacts the contaminated sewer water.
the bacterial slime or “biofilm” is actually three layers each hosting a different type of bacteria
Systems with more contact area treat more efficiently. Our MBBR’s use ultra-high density biofilm media to host up to 5000 M2 of contact area for every 1 M3 of reactor space. That means our treatment reactors can do a ton of work in very little space. And smaller reactors are cheaper reactors.
7000 gallons per day of treatment capacity in this tiny box!
Through secondary treatment BOD and TSS are normally reduced by at least 85%. Our systems can reduce them by 99%.
But BOD and TSS aren’t the only potential environmental hazards in wastewater.
Nutrients like nitrogen and phosphorus can choke waterways and pollute drinking water. Nutrient reduction in wastewater is called “tertiary treatment.”
Our high-density biofilm media performs tertiary treatment simultaneous with secondary treatment. A recently discovered species of bacteria metabolizes the most basic nitrogen compounds, into nitrogen and oxygen gas. The Annamox bacteria can’t grow in every kind of wastewater technology, though. Their long lifecycle requires a protected habitat for them to grow and reproduce in sufficient numbers to mitigate total nitrogen. Our proprietary “biochips” provide protected pockets for Annamox to live and do their work. After about a year, our BioTank reactors can produce effluent discharge under 10 mg/L in total nitrogen with only oxygen.
Conversion of ammonia to nitrate and nitrate to nitrogen gas in wastewater.
So our secondary wastewater treatment systems really provide tertiary results.
Wanna know more about wastewater or how we can take care of it for you?
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).
