Advanced Wastewater Treatment

Whitepaper for BioTank biological reactor in wastewater treatment.

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.

Moving bed biological reactor with transparent background
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.


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.

The BioTank can be designed to meet any effluent standards including advanced treatment required for sensitive areas.

A pristine waterfall at an RV and cabin resort with over 200 units serviced by a biological wastewater reactor
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 with methanol doser
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.

Installation of precast concrete tank for wastewater settling and equalization
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.


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 wastewater package plant diagram for commercial sewage treatment system
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 Biotank’s biofilm process configuration creates conditions for simultaneous nitrification and denitrification.

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.

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

man at advanced wastewater treatment system testing effluent levels


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.

*Sold and supported by Aqua Tech Systems.

What is Eutrophication?

Eutrophication is plant overgrowth in domestic waterways.

green grass on water
Photo by cottonbro on

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 treatment uses natural biological processes to protect the environment from contaminants in sewage.

Wastewater poses several threats to the environment. Micro organisms which digest the suspended organic matter (Total Suspended Solids – TSS) in sewage use up the dissolved oxygen (DO) present in the water. The rate of this digestion can be measured as Carbonaceous Biological Oxygen Demand (CBOD). Water with high CBOD can deplete dissolved oxygen in waterways thereby suffocating wildlife.

septic tank cutaway
A common septic tank design

All wastewater treatment from septic tanks to municipal systems use gravity to settle out most solids. After settling, smaller organic particles remain suspended in the effluent. The settled wastewater then moves into biological treatment which increases the density of micro organisms in an oxygen rich environment. When done properly, biological treatment can neutralize the oxygen depleting effects of wastewater.

Wastewater treatment also removes chemical pollutants.

infographic of nitrification and denitrification in wastewater
Conversion of ammonia to nitrate and nitrate to nitrogen gas in wastewater.

One byproduct of human metabolism, ammonia, can poison watersheds through untreated sewage. Beneficial bacteria naturally occurring in wastewater use DO to convert toxic ammonia into the nutrient, nitrate. That’s good, but not quite good enough. When nitrate along with another nutrient, phosphorus, enters the environment, they can cause plant overgrowth that chokes waterways. Conveniently, other wastewater bacteria turn nitrate into nitrogen gas and mineralize phosphorus which settles out of the resulting effluent.

cutaway of an aerobic wastewater treatment plant

These bacteria multiply into a slime layer called, “biofilm” in the biological reactor. Advanced treatment systems achieve high biofilm density by giving it a lot of surface area (media) to grow upon. The greater the surface area, the higher the treatment level.

Aqua Tech uses the latest in biofilm media technology to achieve maximum treatment in a very small treatment plant.

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).

Got an enquiring mind? Here’s an overhead view of the same sewer system design:

Here’s what a similar system looks like in real life:

Wastewater treatment plant overhead view
A 3-tank in-ground system with a methanol doser and all-weather controls

Whether you’re an engineer or a real estate developer, we can help you put together a system to meet your needs. Just click the button below!

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.

A diagram of showing the process of ammonium in wastewater being converted to nitrogen gas.
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

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.