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 contains nitrate and phosphorus which are nutrients that plants need to grow. Usually, nutrients are good things, but growing population density can result in too much of a good thing being deposited into streams, rivers, and other waterways. When this happens, plant life takes over – crowding out the habitats of fish and other aquatic life. As these plants die and rot, they can change water PH and bacterial levels.
To stop eutrophication, wastewater treatment systems need to greatly reduce or eliminate the amount of nitrate and phosphorus which they return to the watershed in their effluent. Governmental agencies set concentration maximums and enforce them through regular testing.
For the most part, nitrate and phosphorus can be reduced below regulatory thresholds through biological processes known as denitrification and mineralization. Advanced wastewater treatment systems use highly concentrated populations of beneficial bacteria to digest nitrate and phosphorus. The former is then released as nitrogen gas and the latter, collects in the tank as part of the sludge.
Even after advanced treatment, trace amounts of nitrate and phosphorus can frequently be found in wastewater effluent. Where mandated, further treatment can completely prevent even these from reaching the watershed.
If you’re in need of a wastewater system that will prevent eutrophication, let’s talk!
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!
Drip irrigation systems are an efficient and proven technology many communities use to recycle and dispose of treated wastewater. The effluent is applied to the soil slowly and uniformly from a network of narrow tubing, placed in the ground at shallow depths of 6 to 12 inches in the plant root zone.
Because water is such a precious commodity, recycling wastewater can have both economic and environmental benefits for communities. Reusing wastewater to irrigate land can help protect surface water resources by preventing pollution and by conserving potable water for other uses. This is particularly important where community water supply sources rely on wells. The more water that is pumped from wells and discharged as effluent into a stream or other surface water, the less will be available to recharge aquifer or groundwater sources upon which future well water supplies rely.
Another benefit of applying wastewater to the land is that the soil provides additional treatment through naturally occurring physical, biological and chemical processes. Irrigating with wastewater also adds nutrients and minerals to soil that are good for plants and it helps to recharge valuable groundwater resources.
Residential developments with low building density required by septic drain fields contribute to an undesirable sprawl and limit land available for playgrounds, hiking trails, and other open space amenities. Spray systems, while superior to septic, can also limit land use since they produce aerosols that require large buffer zones.
Community sewers that use drip irrigation consolidate undersoil treatment into one region of the subdivision. This region can provide a visually appealing common area for the development. Achieving higher land use densities with desirable open spaces are important and shared goals of land use planners, environmentalists, and developers alike.
Soil reuse systems require less monitoring and thus lower operating costs when compared to surface discharge.
Additionally, subsurface discharge expedites the acquisition of state and county permits by addressing potential concerns of downstream property owners removing any reason for them to contest approval.
Beneficial reuse through drip irrigation is just another way we’re equipping responsible growth. Click the button below to see how we can equip you.
