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. ↩︎
BioTank, Aqua Tech’s biological reactor, is the best value in wastewater treatment for residential and commercial development as well as for small to midsized communities. The following product details demonstrate BioTank’s durability, versatility, and efficiency.
A BioTank hot off the manufacturer’s floor
Aqua Tech’s BioTank bioreactors range in capacity from 160 GPD to 80,000 GPD. They can be installed modularly to build systems with a capacity over 1 million GPD.
Our stainless-steel package systems operate with minimal maintenance for decades. They provide a timely and cost-effective alternative to site-built treatment facilities.
Construction:
The BioTank is a factory-made, multi-chamber aeration tank made of stainless steel AISI-304. It is equipped with fixed and floating media and an aeration system comprised of an air compressor, snorkel, regulator valves, hoses, and oxygen diffusers.
The various chambers facilitate the growth of stage-specific microbes ensuring progressively higher levels of treatment through each chamber.
AISI-304 stainless steel construction allows for above ground and inground installation.
State of the art media provides maximum biofilm surface area which results in smaller bioreactors that treat up to municipal standards.
The aeration system ensures optimal oxygen conditions for advanced biological wastewater treatment.
Biological Reactor Applications in Wastewater Treatment
As a biological reactor, BioTank isn’t suitable for treating water from sources with high concentrations of chemical contaminants such as storm water, drinking water treatment centers, boiler houses or factories.
The BioTank treated effluent quality allows its safe discharge into the environment or reuse for irrigation or other technical needs.
A pristine waterfall at an RV and cabin resort with over 200 units serviced by one little BioTank.
General Provisions
Installation of an Aqua Tech system with BioTank biological reactor will require:
Site prep including a poured concrete pad for the BioTank, drainage areas and access roads
Dedicated electrical power supply (usually 3-phase)
Specialized onsite treatment systems for all local sources of wastewaters which do not correspond to the BioTank application terms
Wastewater should be primarily treated prior to be pumped to the BioTank. The primary treatment should include mechanical treatment (coarse solids and grit removal), FOG (fats, oils and greases) removal, wastewater settling and flowrate equalization.*
Process Specifications
FOG (fats, oils, and grease) Removal
FOG level should be constantly monitored, preferably by means of sensors.*
Amount of FOG enter the BioTank should not exceed 50 mg/l.
If FOG concentration is permanently higher than 50 mg/l in any of local discharges, then it is necessary to apply specially selected biopreparation for FOG decomposition, for example, BioEaseTM4210.
If FOG concentration exceeds 100 mg/l, then it is necessary to build a local grease trap and use the biopreparation for FOG degradation.
Overhead diagram of a wastewater treatment system for mixed-use featuring two BioTanks operating in tandem.
Coarse Solids Removal
The feed pumps should be protected from coarse solids present in wastewater. Depending on a primary treatment technology Aqua Tech Systems offers a solution for the removal of coarse solids.
Grit Removal
Wastewater usually contains certain amount of grit and other mineral substances, which should be removed before wastewater feeding to the BioTank.
Primary Settling
Suspended solids (SS) concentration limit for biological treatment based on the biofilm process is 105 mg/l. As raw wastewater usually has higher SS content (> 105 mg/l), primary settling should be introduced.
Primary Sludge Accumulation and Digestion
Primary sludge volume and odor are significantly reduced through the addition of a biopreparation such as Bacti-Bio 9500.
The sludge level should be constantly monitored by means of an automatic sludge level sensor or manual Sludge Judge device. Sludge removal and disposal should be handled by a certified contractor as needed (usually every 3-5 years).
Flowrate Equalization and Feeding
Aqua Tech installs flowrate equalization systems to minimize BioTank size and maximize performance.
Wastewater equalization enhances biological treatment by minimizing shock loads, diluting inhibiting substances, and stabilizing pH.
The assumed wastewater feeding duration to the BioTank is at least 18 hours/day.
The assumed feeding volume is:
v = Qday / 18, m3/hour, where Qday is wastewater amount per day
Aqua Tech Systems provides necessary settling-digestion and wastewater flowrate equalization tanks of the required volumes which are plastic or ferro-concrete.
A combination settling and equalization tank being installed in Alabama
Phosphorus Removal
If required, phosphorus is removed during primary settling through the addition of coagulant.
Biofilm cannot remove more than 1-1.5 mg/l of phosphorus. The formed biocenosis of the biofilm, being in a state of dynamic equilibrium, does not produce biomass and, accordingly, does not consume phosphorus.
Wastewater processing with coagulant ensures efficient organics reduction and reduces the phosphorus below 1.0 mg/l.
Where required, Aqua Tech provides a coagulant dosing apparatus at the primary treatment step.
Biological Treatment
Process Characteristics
BioTank’s biological wastewater treatment process is based on the biofilm technology. Biofilm is a dense community of attached-growth microorganisms living on specially designed plastic media. The surface of the biofilm treats wastewater by absorbing and oxidizing pollutants. Multiple biozones within the layers of the biofilm create a self-cleaning, self-sustaining ecosystem. The biofilm develops the microorganism diversity necessary for maximum treatment in each application. Due to efficient ecosystem development in the BioTank there is no excess biomass growth.
Technology
Incoming organics are sequentially oxidized by isolated biocenoses of microorganisms living on media retained within the borders of each aeration chamber. The media is submerged in water.
Oxygen supply and mixing are provided by aeration.
Due to change of oxidation rate at each process stage – from high on the first stage to low on the last stage – the loads on biocenoses and water saprobity vary from high to low accordingly.
In response to changing environmental conditions and amount of dissolved oxygen, the treatment process occurs as follows:
Stage One – sorption and oxidation of dissolved organic matter, adsorption of suspended solids and colloids and hydrolysis (fermentation) of suspended solids and colloids
Stage Two – sorption and oxidation of dissolved organics,
Stage Three – biofiltration (biosorption)
Process flow diagram for a commercial application with heavily contaminated influent.
Oxygen Conditions
Oxygen supply is provided by aeration. The oxygen mode is a function of organic load, biofilm density and thickness, and wastewater temperature.
The required amount of dissolved oxygen for each process stage should be optimized and adjusted according to the Aqua Tech Systems recommendations at start-up and follow-up analysis.
The corresponding environment allows formation of layered biocenosis. The layers are determined by the amount oxygen diffusion into the biofilm.
The biofilm surface is the aerobic layer which creates conditions for heterotrophic microorganisms to partially oxidize and reduce ammonium along with oxidation of organic matter.
The internal mass of the biofilm is the anaerobic layer that creates conditions for development, growth and accumulation of specific autotrophic microorganisms (ANAMMOX) which oxidize and reduce the main part of incoming ammonium.
Floating biofilm media from 440 M2 of biofilm per cubic meter to 5000 M2
Biofiltration (Biosorption)
Biofiltration or biosorption occurs in the BioTank on a static media.
In low load conditions bacteria release a significant amount of exopolymers capable to capture and retain solids during contact. In turn, solid substances captured by the biofilm (bacteria, organic matter) serve as a food for predators and detritophages that results in reduction of suspended solids amount.
It should be noted here that bacteria and predators create symbiotic relationship after a number of successions, under which predators regulate their quantitative and qualitative composition in a strict accordance with incoming food amount.
Also the significant input in clarification comes from attached stalked ciliates (Peritrichia). The peritrichs provide themselves with food by filtering large amounts of water. One individual is able to consume up to 30,000 bacteria per hour. This way peritrichia provide a high degree of biological disinfection, destroying pathogenic microorganisms.
Low organic load and high amount of dissolved oxygen in the biofilter provide partial ammonium removal.
Ammonium bio-oxidation is carried out in two stages, by two types of chemoautotrophic bacteria:
2NH4+ + 3O2Nitrosomonas = 2NO2- + 2H2O+4H+
2NO2- + O2Nitrobacter = 2NO3
Start-Up
Formation of the biofilm occurs spontaneously based on the set and maintained level of dissolved oxygen in each chamber. The biofilm reaches dynamic equilibrium as it develops through the initial operating period. Once this happens treatment process performance meets the project requirements.
Under conditions of actual loadings correspondent to the design specifications biocenoses fully mature:
For “B” bio-oxidation process – within four weeks
For “N” bio-oxidation and nitrification process – within one year.
The actual treatment efficiency should be at least 95.99% of the calculated one.
If necessary, the achievement of treatment quality for the process “N” can be accelerated by the use of methanol. Methanol provides an additional food source for heterotrophs which thereby multiplying their population. Due to lack of oxygen, heterotrophic microorganisms use oxygen from nitrates, thus reducing oxidized nitrogen. In this case it is possible to reach at least 90% of all required parameters within 60 days from start-up.
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!
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).
Removing ammonia nitrogen from wastewater is a well-established and quantifiable biological process. Nitrogen exists in the influent primarily in the form of organic nitrogen and ammonia nitrogen (Total Kejldahl Nitrogen + TKN). The principal part of the organic nitrogen is mineralized to ammonia nitrogen through bacterial activity. Therefore, ammonia-N is commonly regarded as the starting point in the nitrogen reduction process.
Wastewater nitrification and denitrification take place in our BioTank
Nitrification: the conversion of ammonia nitrogen (NH3-N) to nitrate nitrogen (NO3-N) is a biological process accomplished in the presence of dissolved oxygen. Typical requirements for effluent ammonia-N are from 1 to 3 mg/l, which is reliably accomplished. Successful nitrification is accomplished with a healthy microorganism population and an environment where PH, temperature, alkalinity, organic loading and dissolved oxygen are stable.
In the BioTank system the pH is generally buffered by the carbonate system associated with the wastewater; the temperature remains consistent due to the biological activity in the plant; the organic loading is relatively constant because the wastewater has been treated in the first compartment(s) of the plant; and the compressor provides an adequate supply of dissolved oxygen.
Nitrification/Denitrification Table
Facultative heterotrophic organisms under anoxic conditions accomplish biological denitrification. In this process bacteria convert the nitrate-N to nitrogen gas that is released into the atmosphere.
Denitrification occurs by several different means and though process control adjustments. As the microorganisms multiply, the biological film thickens on the submerged media and the diffused oxygen is consumed before penetrating the full depth of the slime layer. Consequently the film develops aerobic, anoxic and anaerobic zones. This process accounts for significant nitrogen removal via simultaneous nitrification and denitrification.
Denitrification utilizing septic tank carbon is widely considered to be the most economical and efficient method for nitrogen removal. Utilizing prescribed recirculation rates this method of returning BioTank nitrified wastewater to the carbon source in the anoxic zone of the primary tank has achieved reductions of nitrogen of approximately 80 percent.
Nitrogen removal may be enhanced further in a tertiary anoxic zone located after the aerobic treatment.
To learn more about this critical process and how Aqua Tech can help you utilize it, click the button below.
