Regarding the conditions for growth and interaction between microorganisms, biological reactors can be classified in two ways: Suspended biomass reactors and attached biomass reactors.

Examples of suspended biomass reactors are the traditional processes of activated sludge, SBR, MBR etc.

The attached biomass processes have emerged as a possibility of increasing the capacity of existing suspended biomass treatment systems, increasing the performance of nitrification or denitrification and render more compact treatment systems designed to remove high organic or nitrogen loading.

The attached biomass processes are subdivided into fixed bed reactors or dynamic bed reactors. The two processes have some characteristics in common, for example, biofilm formation on a substrate and being able to incorporate the two types of technologies into existing systems.

However in fixed bed processes there are drawbacks such as clogging of the bed due to the permanence of dead cells in the biofilm, which becomes excessively thick to not loosen, a typical phenomenon of fixed bed systems. Consequently preferred paths and dead zones are created.

The clogging also carries anaerobiosis at certain points of the reactor, reducing the removal of organic matter and nitrification. Additionally there are problems such as odor and vectors proliferation at points where clogging is complete.

To solve these problems there is the necessity of stoppage of fixed bed reactors for periodic cleaning.

An additional drawback is the start of tanks: the removal of organic load will be damaged during the process of acclimatization of biomass, substrate adhesion and biofilm formation.

These limitations are eliminated with the use of Israeli technology AGAR ("Attached Growth Airlift Reactor"). This technology consists of adhered biomass reactors in a mobile bed, which consists of recycled PEAD biomass carriers on which biofilm will increase.

The "design" of biomass carriers was developed to provide a high internal area, which means a large surface area available for biofilm formation (650 m2/m3).
Carriers are drilled to prevent clogging, facilitating the transport of oxygen and substrates for biofilm. Another difference is the constant clash between the carriers, which is important to assist the detachment of the biofilm when its thickness increases excessively.

The following picture is a representation of biomass loading inserted into the moving-bed reactors.

The AGAR technology can be used in the MBBR and IFAS settings ("Integrated Fixed Film Activated Sludge").

The MBBR configuration ("Moving Bed Biological Reactor") consists of an aerobic reactor which contains part of its useful volume filled with biomass carriers. Autotrophic and heterotrophic communities form biofilms on biomass carriers for the removal of organic and ammonia nitrogen loads, with only a small portion of biomass is suspended. Then there will be a separation unit of the suspended solids and biofilm parts which drop away from carriers (sedimentation or flotation).

The MBBR process can also be used to remove nitrates if the carriers are added to anoxic reactors, in this case a combination of anoxic and aerobic reactors counting biomass carriers in the two tanks will be produced.

The following picture is a representation of the MBBR process.
The IFAS configuration combines the activated sludge and MBBR processes, consisting of the sequence of an aerobic moving bed reactor, an aerobic reactor suspended biomass and a solid phase separation. As in the MBBR, in IFAS configuration anoxic reactor biomass carriers may also be added to the process to reduce the nitrate.
The following picture is a representation of the IFAS process.

Some of the advantages of the AGAR technology adhered biomass with moving bed (valid for the MBBR and IFAS configurations) relative to suspended and adhered biomass conventional systems are:

- IFAS and MBBR settings can be used to increase the capacity of any existing biological treatment, from stabilization ponds and "trickling filters" to activated sludge systems;
- Increase of the treatment capacity of existing systems without new construction. Since it can maintain a higher microbial population in the bioreactor, it is possible to oxidize more organic load in the same volume;

- The expansion can be made gradually by adding more biomass carriers. This makes it possible to increase the capacity of a treatment system according to the need, minimizing the investment required;

- The implementation of the MBBR and IFAS settings is quick and can be performed without interrupting the operation of the existing system;

- The IFAS configuration is great for systems with biological removal of nitrogen and phosphorus, as it allows the maintenance of autotrophic population necessary for the oxidation of ammonia nitrogen in the biofilm when the suspended biomass reactor is operated with low sludge age values to avoid phosphorus release assimilated in excess biological sludge. Thus the oxidation of the ammonia nitrogen will not be affected by biological phosphorus removal;

- In MBBR configuration there is no need for the concentration of volatile solids in suspension adjustments on biological reactor (MLVSS), simplifying operation and monitoring through laboratory analysis;

- Conservation of a significant autotroph population in the lower layers of the biofilm, which enables high nitrification efficiency and lower losses of nitrifying biomass before shock conditions;

- The "design" of biomass carriers is elaborated so that there is a high surface area per cubic meter, providing large areas for the adherence of biomass. Thus one can maintain large concentrations of microorganisms in small volumes of reactor;

- As the thickness of the biofilm increases, the more superficial regions are predominantly aerobic (whichever the carbonaceous oxidation and nitrification) and regions near the biomass carriers assume character near the anoxic (denitrification occurs in significant amounts). Thus, in the same reactor it can be removed a wider range of pollutants;

- Operation of the system is simple and requires minimal automation, enabling the implementation of the system in places with few resources, and stations where the operation is shared with other units, for example, the areas of industrial installations of utilities;

-The Durability of carriers is high, with 20 year warranty for biomass carriers (both sanitary and industrial effluents).

Since 2013 the UPE has an exclusive partnership with the Israeli company AQWISE to provide biological treatment systems with biomass attached by AGAR technology. The AGAR technology has been patented after more than a decade of research, and the Israeli company AQWISE a world leader in deploying adhered biomass in moving bed systems.

With extensive operations in the Americas, the Middle East, Europe and Southeast Asia, AQWISE implemented the AGAR technology in more than 300 municipal and industrial facilities spread across 35 countries.

The partnership between the UPE and AQWISE enables the development of customized projects according to the specific needs of each client.