Activated Sludge Controlled Oxygen Reactor



The pre-engineered ASCO2R treatment plant is a unique, intermediate sized biological wastewater treatment system. The overall pre-engineered design can achieve a clear and odour-free effluent with minimal maintenance. The system is pre-built at the factory and shipped to the project site as a self contained unit that requires only minimal field assembly.

The pre-engineered ASCO2R treatment plants are a type of biological treatment for sewage wastewater using the activated sludge extended aeration technology, but adding the feature of the patented maintenance-free Flouroprobe® technology for matching air requirements to both the hydraulic and biological loading or for creating aerobic or anaerobic zones within the single aeration chamber for nitrification and de-nitrification.

The basic design is an extended aeration period that is approximately 24-30 hours, coupled with a defined
settling period that is approximately four hours.

The extended aeration process purifies the sewage by the destruction of the organic compounds using air to mix and oxidize the volatile material into gas, water and sludge. By the continued aeration of these concentrated solids, biological organisms are produced and grow in colonies. These colonies will attach themselves to the volatile materials breaking it down into water, carbon dioxide and ash. The result is a clear and odour-free effluent.

ASCO2R is a packaged biological wastewater treatment system ideally suited for sewage wastewater flows of
15,000 gals to 750,000 gals per day and is complete and ready for operation in accordance with the plans and specifications. The wastewater treatment system is commonly known as the ASCO2R process (activated-sludge with Controlled oxygen reactor).
ASCO2R is an activated-sludge-return process commonly used in municipal and package treatment plants around the world combined with the patented maintenance-free oxygen "FlouroProbe's" unique ability to control the oxygen levels at different ranges within zones in the plant creating the conditions for the best microbial development for natural biological treatment.

The result is the capability for the system to:

1. Automatically control the DO level to match the demand created by either low flows, fluctuating flows, peak flows and fluctuating biological loading1. Automatically control the DO level to match the demand created by either low flows, fluctuating flows, peak flows and fluctuating biological loading

2. Vary DO levels from zone to zone within the plant for the creation of nitrification and denitrification zones that are established for Total Nitrogen reduction.

3. Minimize bio solids creation through the automatic ability to match the hydraulicloading and biological loading to the required DO and maintain a continuous treatment level at all times by the proper creation of the correct type of microorganism development.

4. Provide the correct balance of air to biological mass ratio to near-eliminate pin floe creation through maintaining "fat" and healthy microorganisms

The patented Flouroprobe® monitors the Dissolved Oxygen (DO) continuously and does not need cleaning or re-calibrating due to the unique method of measuring DO through luminescence of ultra-violet light.

This capability allows the Flouroprobe® to automatically adjust the DO level in the plant to match the level of DO needed to treat appropriately low flows, fluctuating flows, peak flows or fluctuating biological loading. Also it can vary the DO levels from zone to zone within the plant for the creation of nitrification and denitrification zones for Total Nitrogen reduction. The automatic, real-time DO matching to hydraulic and biological loading rates can minimize biosolids creation by maintaining a continuous treatment level at all times by the proper creation and stabilization of the correct type of microorganism for sewage treatment. The correct balance of air to biological mass ratio almost eliminates pin point floe normally associated with activated sludge plants by maintaining "fat" and healthy microorganisms.

The advantages of the ASCO2R Pre-Engineered Sewage Treatment Plant are: (1) sludge production is the least produced over that of other technologies (2) intermittent or longer term change in biological or hydraulic loading does not change the effluent quality as the DO is monitored to match the loading rates and achieve full designed treatment (3) Total Nitrogen reduction capabilities (4) no chemicals to add as only atmospheric air is introduced into the plant in controlled quantities given the loading rates and detained for a specified period given the effluent design parameters (S) Near-elimination of pin point floe normally associated with conventional aeration plants.

This ASCO2R process allows for the four (4) stages of proper micro-biological bacterial activity which are the key to the natural treatment of domestic raw sewage. These four (4) stages are:

This stage activates the bacteria microbes of amoeboids, flagellates, ciliates - free swimming, ciliates - stalked, and rotifers.

This stage has the established bacteria microbes go through their respective life cycles of growth to adulthood.

This stage has the right balance of the microbial types established to maintain and achieve optimum sewage digestion and breakdown.

This stage is where the microbes themselves die and their remains are inert materials within the aeration tank. The microbes remaining are oxidized and are reduced but not eliminated altogether.


The standard ASCO2R sewage treatment plant utilizes the activated sludge method of biological waste reduction.
Activated Sludge plants are characterized by the introduction of raw wastewater directly into the aeration tank,
long term aeration (usually 24 hrs.), high mixed liquor suspended solids, high sludge return ration, and low sludge wastage. This system is generally used to serve populations that produce up to 750,000 gallons per day of domestic sewage. Applications include subdivisions, multiple family dwellings, mobile home parks, shopping centers, commercial offices, industrial facilities, motels, schools, and recreation areas.

The long detention time in the aeration tank permits the plant to operate effectively even though flows and strengths vary widely. The standard basic plant can be divided into three units of operation:

1. Aeration Tank
2. Clarification Tank
3. Sludge Decanting Tank (aka Sludge Holding)

Aeration Tank:

The raw wastewater passes through a bar screen before entering the aeration tank. The bar screen prohibits large items from entering the tank that would not readily decompose and possibly plug the airlift pumps. The aeration tank is used for the detention and mixing of raw wastes with sludge the pumped from the clarifier hopper back to the inlet microorganisms present in the return sludge. The air keeps the contents mixed and the solids in continuous contact with the decomposing bacteria. The bacteria absorb the organic material, using it as food. The resulting residue is a stable humus material.

Clarification Tank:

The liquid and solids flow from the aeration tank into the clarifier. The clarifier is a quiescent zone, which allows the solids (sludge floe) to settle to the bottom where they are recirculated to the aeration tank. Small particles of buoyant material may rise to the surface where they are removed by a scum skimmer and pumped to the aeration tank for further detention and decomposition. The effluent from the clarifier is a clear liquid with approximately 90% removal of the suspended solids and organic material.

Sludge Decanting Tank:

This aerated tank is used for storage of excess solids wasted from the treatment plant proper. A portion of the sludge removed from the clarifier is discharged into the holding tank instead of returning it to the aeration tank and to further concentrate the sludge tank contents. The sludge is aerated and then manually discharged to sludge drying beds or disposed of in sanitary land fill.



The ASCO2R Series Sewage Treatment Plant is the newest generation of activated sludge sewage treatment plants, and has been available for over 35 years with over 15,000 units in operation throughout the world.

Nomadic Systems Inc., CANADA (BC) l USA (Florida) l AFRICA (Abidjan, Ivory Coast)

22867 Fraser Highway, V2Z 2T3 Langley, BC, Canada

Toll-free: +1.877-556-8489 | Tel. dir. (+225) 51 36 36 46 | (+225) 79 95 32 46

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