Advanced Wastewater Treatment

Biological Sewer Sludge Treatment and Reduction

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).

depiction of three layer biofilm on plastic media

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.

Specialized Bio-Film Media

floating media for wastewater biofilm

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).

Floating media for biological film wastewater treatment plant

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.

wastewater treatment biological reactor static media

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.

Nota Bene:

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.

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.

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.

septic tank cutaway
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.

infographic of nitrification and denitrification in wastewater
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?

The BioTank is at the heart of the Aqua Tech System

The BioTank uses floating and fixed film processes in which microorganisms attach themselves to a  highly permeable media that is submerged in the wastewater. This allows for the absorption of organic and inorganic matter into the slime layer where treatment is realized. Designed properly, this filter is self-purging.

Hydraulic dosing and secondary sludge airlift pump systems are set at pre-determined rates to minimize maintenance and enhance treatment. The self-purging biological filter is designed by Aqua Tech Systems to accommodate influent characteristics and achieve effluent requirements. Oxygen is introduced to the system via an oil-less compressor and membrane aeration equipment.

Wastewater is pumped from the influent pump chamber to mechanical equipment or directly into the first baffled compartment of the BioTank. Alternatively, primarily settled
or prescreened wastewater is pumped from an equalization basin to the BioTank. Wastewater flows by gravity through each treatment compartment of the BioTank and effluent is discharged over a weir.

As flow enters each aerobic compartment dissolved oxygen is transferred to the wastewater via compressor and membrane aeration module. Each compartment has an independent and fully adjustable air regulation valve. In the aerobic modules the
compressor acts as a mixer to enhance treatment and prevent the short-circuiting of wastewater through the plant.

In the BioTank, the organic material in the wastewater is reduced by a population of microorganisms that attach to the filter media and form a biological slime layer. In the outer portion of the slime layer treatment is accomplished by aerobic microorganisms. As the microorganisms multiply the biological film thickens and diffused oxygen is consumed before penetrating the full depth of the slime layer. Consequently the film develops aerobic, anoxic and anaerobic zones.

Absent oxygen and a sufficient external organic source for all cell carbon the microorganisms near the media surface lose their ability to cling to the media. The wastewater flowing over the media washes the slime layer off the media and a new slime layer begins to form. The process of losing the slime layer is called “sloughing” and it is primarily a function of organic and hydraulic loading on the filter. This natural process allows a properly designed media bed to be self-purging and maintenance free.

Any excess sloughed biomass is transferred with the wastewater flow to the final clarifier as sludge. These secondary sludges are periodically pumped back to the primary tank or sludge holding tank for eventual removal or further treatment.

The BioTank treatment plants may also be supplied with bar racks or screens, grit chambers, flow meters, chemical dosing equipment, UV disinfection modules and sludge dewatering systems.

To put the BioTank to work for you, click the button below to schedule a consult.

When we say that our systems are the best, here’s a bit of what we mean.

Major components of the BioTank system are constructed of carbon steel or stainless steel, with plastic or zinc coated steel for railings and fences. The unit provides ready access to each treatment compartment facilitating operation and maintenance procedures. The media blocks are easily removed from each treatment compartment for inspection or plant maintenance.

Random packed media that is biologically inert and mechanically durable enhances oxygen transfer.

The oxygen delivery system comes self-contained within each BioTank.

An efficient oil-less compressor with few moving parts supplies dissolved oxygen to the treatment process. Low noise and vibration is a positive design characteristic associated with these

A 304 stainless steel exterior or NEMA 4X mountable control cabinet is provided with each
BioTank. Each cabinet contains the control logic to automate the function of the compressor, sludge airlift, coagulant dosing pump and cabinet heater if necessary.

The BioTank treatment plants can be supplied with separate or attached offices, laboratories and mechanical equipment rooms.

wastewater treatment system inside large building
BioTank installed in a metal building

The BioTank treatment plants may also be supplied with bar racks or screens, grit chambers, flow meters, chemical dosing equipment, UV disinfection modules and sludge dewatering systems.

All of our systems are completely customizable to perfectly fit your needs. Click the button below to speak with a member of our sales team.

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.

As these media get smaller, their treatment capacity goes up.

Biofilm. It’s not a documentary narrated by David Attenborough; it’s the organic factory that cleans wastewater in our BioTank biological reactors. Biofilm is a population of microorganisms that attach to a filter media and form a biological slime layer. As wastewater flows over the biofilm, the microbes consume the organic material. This means that the more square meters (m2) of biofilm present within a treatment system, the more treatment can take place. Earlier aerobic treatment tanks used suspended growth and fixed film systems which could treat wastewater down to TSS (Total Suspended Solids) and BOD5 (Biological Oxygen Demand) concentrations as low as 20mg/L. Those are impressive numbers compared to traditional onsite system effluent, but those older systems had to be especially large to accommodate a large enough population of microbes to get the job done. Also, treatment was quite slow requiring several days.

But those days are over!

example of a floating biofilm medium
Our treatment systems feature hundreds of these floating media

Aqua Tech’s BioTanks feature one or more* chambers filled with floating biofilm media. These media hold the slime layer rather than allowing the microorganisms to contribute to the suspended solids as with suspended growth systems. Because they move around through the wastewater, they treat more efficiently than fixed film.

How efficiently?

We actually have numbers to answer that question. Remember that when it comes to biofilm, more square meters means more treatment. More square meters per cubic meter (m3) means more treatment in less space – greater efficiency. Our floating media incorporates an incredible amount of surface area per cubic meter. With highly advanced production methods, we can now offer very small media with very high m2/m3 (square meters per cubic meter).

The evolution of floating biofilm media…

Five sizes of wastewater biofilm media
As the media get smaller, the biofilm gets larger.

The photo above shows five generations of floating biofilm media. Let’s look at the m2/m3 for each of them.

This one is a little smaller than a shot glass. It can host 440 square meters of biofilm to every cubic meter of treatment tank.

This one is about the size of a thimble. It’s surface area per cubic meter is over twice the amount of the first one.

This one could fit in a half teaspoon. It’s surface area is 2200 m2/m3.

Now get ready for an evolutionary jump!

Talk about biological engineering. Look at that thing! This little Pringle-shaped wafer boasts 4000 square meters per cubic meter.

It’s this kind of technology that enables Aqua Tech systems to treat down to <10mg TSS & BOD5 within a tiny footprint. And now, with a demand for high efficiency Single Family systems, we’re pushing the boundaries even further.

This little guy is smaller than a nickel. All of those tiny holes translate into a whopping 5000 square meters of biofilm per each cubic meter.

But the Biochips aren’t just pretty to look at. See them at work below!

Let us put one of our high tech wastewater treatment systems to work for you today! Just click the button below to get started.

*Number of chambers containing floating media varies by model and application