Technology of ADOS Water Treatment Plants



The technology USBF (Upflow Sludge Blanket Filtration) is unique since it integrates all necessary and required operations and processes (nitrification zone, pre-denitrification, final sedimentation zone, aerobic sludge stabilisation, sludge thickening, if need be) in a single vessel. It results in low costs of acquisition, smaller bay, low operating costs.


Purification Process

ADOS Waste Water Treatment Plants purify water on biologically based process.The process is based on life process of biomass represented by activated biological sludge. It is a mixture of microorganism that process substances contained in wastewater and which they need for their life.Biological reactor comprises three basic processes:


De-nitrification Process
De-nitrification is an opposite to nitrification and it means a reduction of nitrates and nitrites –  in wastewater. De-nitrification process takes place under anoxical conditions (content of dissolved oxygen is less than 2 mg/l). Following bacteria can perform denitrification: Micrococcus, Chromobacterium, Denitrobacillus, and others.


Nitrification Process
Under oxical conditions (concentration of dissolved oxygen is 2.5 to 4.0 mg O2/l) organic pollution in wastewater changes to biomass through biochemical synthesis (activated sludge) and amonial nitrogen are changed to nitrates and nitrites.Nitrification is performed in two steps. First amonial nitrogen is oxidized to nitrites by means of bacteria as Nitrosomonas, Nitrosococcus, Nitrospira, and Nitrosocystis. In the second step nitrites produced oxidize to nitrates by Nitrobacter and Nitrocystis microorganisms. Both the groups of microorganisms are strictly aerobic and they need carbon dioxide as a source of carbon.

In order to maintain a sludge load with KI = 100, it needs to keep content of V30 sedimentary sludge to be between 360 – 650 ml/l.


Final Sedimentation Process (separation USBF)
Purification process does not need any chemicals. Activated sludge is separated from effluent water in a special zone – final sedimentation zone USBF. Effluent overflows out and activated sludge returns back to the beginning of the purification process.

This purification system reaches remarkable parameters of water quality with aerobic stabilisation of unified activated sludge at the same time. The system is resistant against changes in loading and guarantees high efficiency of purification with low variation of effluent quality.

Effluent is separated from activated sludge and flows out from the reactor, activated sludge returns back to the beginning of the purification process. When starting the biological reactor an activated sludge from a Waste Water Treatment Plants in operation is applied and through purification process microorganisms are reproduced and thus activated sludge volume increases. Activated sludge volume is kept at an optimum volume and excess sludge is taken away from the reactor. This purification process does not need any chemicals.



High efficiency and low operating costs are two main characteristics.


1. High Activated Sludge Concentration

Traditional water treatment plants operate at low or medium loads of activated sludge. Our plants operate with higher concentrations of activated sludge that is one of precondition of high treatment efficiency.


2. All Processes may be integrated into one Bioreactor

Most conventional technologies are split in many building parts – tanks, reservoirs, bioreactors, final sedimentation tanks, ebc. Our technology can carry out all these processes in one compact bioreactor, combining all necessary operations and processes and this fact has a favourable impact on operating cost and vessel cost of wastewater treatment plant.



· Reduced capital expenditures:

Integrated bioreactor has lower capital demands than a set of individual sections and requires less bay area.

· Reduced operating and maintenance costs:

Integrated bioreactor having minimum number of movable parts with self-regulating purification process has minimum requirements for maintenance.

· High purification efficiency:

Units show high purification efficiency not only for BOD5 values but even for COD,SS, NL and N-NH4.

· Aerobically stabilised sludge:  

Low load and long age of sludge are the reasons for which the sludge from the treatment plants is aerobically stabilised and is not exposed to ecomposition.

· No odour:

Plants working in aerobic mode and do not emanate any odours..

· Hydraulic flexibility:

Final sedimentation section USBF is of such design that it can withstand a required hydraulic overload.

· Design flexibility:

Assembly of an integrated bioreactor can be tailored as a customer requires.



Essentially, the bioreactor combines all functions of conventional biological advanced treatment plants it operates with low load of sludge, higher age of sludge age and reaches higher treatment performance. Reductions of BOD and Total Suspended Solids (SS) under 30 mg/l are easily achievable. If observing the Operating Manual of Wastewater Treatment Plants the below tabulated values can be obtained.

BOD [mg/l] 20-25
COD [mg/l] 70-100
SS [mg/l] 25-30
N-NH4 [mg/l] 2-5
P-TOTAL [mg/l] 5-8


The quality of the effluent allows its discharge into a receiving or storm sewerage. After disinfecting the effluent can be reused for irrigation, washing of roads, pavements, etc.



Excess sludge

The activated sludge is a biomass consisting of microorganisms or of living matters using contamination of wastewater as their source of energy for life and reproduction. Entering contamination is converted to activated sludge. Thus the content of sludge continuously increases in the system.

An Age of sludge from this technology is longer than 26 days. This age provides fully for aerobic stabilisation. 

Since the system is continuously supplied with contamination included in wastewater then after reaching the operational concentration of activated sludge – excess sludge has to be discharged from the system.

A sludge facility is designed with respect to daily sludge production. Sometimes a container is sufficient soimetimes is needec pre-thickening up to sludge dewatering to the concentration of ca. 40 volume percentage of sludge dry residue can be applied.