New generation automated fel type biological wastewater



The plant is intended for domestic wastewater, accessing from the kitchen, bathroom, WC, and other similar purpose rooms. Thus it is forbidden to pour oil and other petroleum products, grease (the allowable grease is the amount of grease, accessing the pipes during the dish washing), chemical substances, which access the sewage is not foreseen according to their scope (agro-chemistry, bleach and other chemical substances, especially containing chlorine). The surface waste water from the roof, yard, drain water and water from the basin also cannot access this equipment, as the aforementioned water would damage the hydraulic conditions of the plant.  The system treats domestic wastewater biologically.  

Standard - is green gelcoat cover in the complekt (1). But we can offer and other : 
TELESCOPE (2) - The option is ideal for those who save space on their plot. Height-adjustable telescope + black (or green) plastic cover.
TRANSITION UNDER THE CARRIAGEWAY (3) - The choice is suitable if you plan to install the cleaning device under the carriageway, where a cover is provided with pads or the like. After using the transition, all you have to do is take care of the cast iron cover, which you can choose according to your needs. 
For more info about this instalation bellow, in the list "Instalation"    

Information about Product



Before placing the wwtp on the vehicle, make sure that there are no sharp bulges which could damage the plant. Plant must be transported in vertical position! To avoid various damages during transportation plant should be securely fastened. For fastening use GRP, nylon or other non-metallic belts. 

During storage the plant must be protected from damage and third parties, and store the plant on the flat and stable surface.


Before starting the construction works, you will need following material and tools / machinery:

  • good quality adhesive-sealant (eg., Wurth Bond+Seal),
  • joint-pins M4x30 A2 or stainless steel screws DIN7337 M4x35 A2,
  • backfill: light soil (3-20 mm size sand or gravel),
  • PVC sewer pipes of required diameter,
  • PVC pipes or hose for air supply of required diameter,
  • electrical cable 3 x 1,5 kW, 220 V (in case when the air blower is installed outside next to the plant),
  • cable protection hose (in case when the air blower is installed outside next to the plant),
  • shovels, mini excavator bucket,
  • hot dip galvanized anchoring bolts M12x110 mm (if necessary),
  • concrete mixture or concrete reinforced plate of required diameter (if necessary),
  • personal protective equipment (vest, gloves, helmet etc.).

Also water supply is necessary in construction site.


The location where the plant will be installed should be selected as described in the technical project. If technical project is not available, the location shall be selected in accordance with Construction Technical Regulations. The plant shall be installed in location where the sludge suction vehicle can easily service it. Also, do not install the plant in a place where the rain- and snow water accumulates.


Groundworks should be carried out in accordance with Construction Technical Regulations and technical project.


The shape of the excavation shall look like funnel. Diameter of the excavation shall be at least 1.5 m wider at the top and 0.5 meter wider at the bottom than the diameter of plant. The maximum backfill from the ground surface to the top of the plant is 1.2 m.  


Model People equivalent Hydraulic daily flow  Cover, D (mm) Diameter (mm) Height (mm) Inflow (mm)
FEL/4 4 0,8 1000 1520 2090/2290 500/700
FEL/6 6 0,9 1000 1720 2450 770
FEL/10 10 1,5 1000 2020 2510 700
FEL/15 15 2,25 1000 2420 2610 700
FEL/25 25 3,75 1000 2870 2890 700

Excavation shall be prepared in two stages:

  1. The excavation is dig up by the excavator up to 20–30 cm of the altitude of the bed of excavation.
  2. The last 20–30 cm of ground shall be excavated manually. Keep the excavation dry by using pump if necessary.


 1. Low the plant into excavation. Use lifting belts and excavator bucket. Fasten the belts to the handles.

2. Centre the plant. Plant must be installed strictly in horizontal position. The spirit level can be used to ensure the level.

3. Backfill, i. e. light soil shall be compacted with water and / or using the soil compactor. It is prohibited to use different ground for backfill (eg., clay, construction waste, etc.) !!! Join the plant with manhole. It is necessary to ensure water tightness. Use good quality adhesive-sealant and joint-pins or stainless steel screws. Distance between screws is about 15 cm. Join the manhole with the inspection lid too.

4. Fill the tank with water and the excavation with the backfill by equal 20–30 cm layers as follows: 1) inner chamber, 2) external chamber, 3) excavation. Repeat it up to the outlet pipe.

5. Connect PVC sewer pipes to the inlet and outlet sleeves. The slope of the pipe should be 1-2 cm/m. Pipeline must be laid on the natural soil. Materials such as gravel, sand can be used for the base of pipeline.

6. Finish the backfilling up to designed altitude. For the upper layer of soil (20–30 cm) use compost. The upper layer of ground around the plant should be 5–10 cm higher than local area surface. Seed with the grass.


The control box shall be installed next to the plant. Distance shall be about 1 meter. There are two outlets on the bottom of control box. There are two at the bottom of the control box outputs for connection to the air supply pipe to the aerator and to the air supply pipe to the aerator. Also, just above the side of the equipment box is a connection to the electrical outlet. The power cord must have a protective armor.


When the plant has to be installed under low intensity vehicular traffic (vehicular loading under 1.5 tones), it is necessary to protect it from vehicle load. In this case it is necessary to install reinforced concrete plates. The plate should be mounted on the poles. The concrete plate cannot be bedded down on the plant; at least 5–10 cm of backfill shall be between the plate and plant. The size of plate is calculated by a designer (constructor) individually in each case, because it depends on vehicle weight and intensity.

The plant to be installed under vehicular traffic is equipped with extension shaft. 1 meter standard diameter is reduced to 0.6 meters. You can install plastic or cast iron sewer cover on top of it.


When the plant has to be installed in wet ground, where groundwater level is less than 2.5 meters from the ground surface, it should be anchored to reinforced concrete base. For concrete base regular reinforced mesh or plate can be used. Use anchoring straps and hot dip galvanized anchoring bolts. Distance between the bolt and the wall of the concrete base shall be not less than 105 mm. In case if customer ignores this note, the manufacturer is not responsible for long-term physical or mechanical forces which can deform the plant.


Wastewater treatment plant can be started-up by owner. There are two options to start-up it :

  • Natural grow up

With this option microorganisms (i.e. activated sludge) have to grow up in wastewater treatment plant naturally. During installation works the plant had to be filled with water, the control unit box connected to the plant, and electric power connected to the box. Switch on the control unit. You should observe turbulence (bubbles) in bioreactor. The aeration process is starts. Within first week of operation supply wastewater into plant only in urgent cases (i.e. WC, shower). Within first 3-4 weeks of the operation limit the quantity of household chemicals; use washing machine and/or dishwasher only if it necessary. I.e. during first month of operation the wastewater treatment plant shall receive more organic matter (WC, shower, sink) and less chemicals and large amount of water. From 4th-5th week of operation the plant can be fully loaded without limiting ourselves in household.

This option is the best when the average day temperature is no less than +10 ºC and at night time no less than 0 ºC, because cold season is not a good time for reproduction and decompose of microorganisms.

  • Bringing activated sludge

Switch the control unit and aerate the plant for one day. Next day pour the activated sludge from a properly operating biological wastewater treatment plant: the amount of sludge – 5–10 % of the volume of the plant (Table 01), concentration at least 4-5 g/l. Aerate the plant all next day. After this procedure you can supply wastewater into plant without limiting ourselves in household.

This option can be performed at any time of the year. 

Daily operation


The waste (excess sludge) formed during the treatment of domestic wastewater must be disposed in a proper and environmentally safe way. The amount of the sludge and de-sludging frequency depends on hydraulic and organic loading of the plant. Each plant has its own characteristics. During accredited 38-week test period no sludge removal was necessary. Plants serving domestic residential properties will typically require de-sludging once a year. How to determine when is the time to remove the excess sludge? You can perform a simple test: use clear container (eg. a jar) and take a sample of sludge and water mixture from the bioreactor. Allow sludge to settle for about 30 min. The sludge may occupy up to 70–80 % of the volume. When the volume of the sludge reaches 80 percent or more, it is time for de-sludging. The sludge shall be removed from both chambers (clarifier and bioreactor).

De-sludging must be performed by authorized service companies. Switch off the control unit box for 1–2 hours, sludge will settle. Open an inspection lid. De-sludging procedure will be carried out by the pump of the sludge suction vehicle.

Air blower maintenance

The efficiency of wastewater treatment depends on proper operation of the air blower, so it is very important to ensure a proper operation of it. Occasionally check whether the air blower is operating normally: is it making abnormal noise or vibrations, is the temperature abnormally high etc. It is necessary to clean the filter element once every 3 months:

  • Undo the truss head screw.
  • Remove the filter cover.
  • Slap down dust by hand. If it is heavily contaminated, wash it by using neutral detergent. Then rinse and let it dry in the air.
  • Reassemble the filter element back in place.
  • Secure the filter cover with truss head screw.

Prior to maintenance servicing, pull off the power cord. Do not use benzene or solvents to clean the filter element as it can damage it. More information about maintenance, possible failures etc. is described in the User Manual of air blower. Please read it carefully!

Daily operation

To maintain efficient daily operation of the plant, the following should be noted. Operating the plant is FORBIDDET TO :

  • Pour bacteria and other bio preparations (eg.: Septic Gobbler, Toilet Gobbler, BioActive, Bio 7 Fosses ). Such bacteria are intended for sewage or septic tanks, other anaerobic systems to eliminate the odour and decompose organic matter.
  • Discharge from water softeners (i.e. regeneration process wastewater) into the plant as the salts will significantly reduce the efficiency of wastewater treatment. In this case it is necessary to provide a separate drainage pipeline for process wastewater, bypassing the plant.
  • Discharge from condensing boilers.
  • Connect swimming pools, hot tubs etc. A large amount of water can wash the activated sludge from the system, and chlorine may affect the quality of the activated sludge.
  • Connect surface run-off, rainwater. Surface/rainwater should always be discharged to a rain drainage.
  • Put down to the toilet hygienic products, such as paper towels, sanitary pads, tampons, cotton pads, cotton swabs, diapers, wet wipes, rubber products (gloves, condoms) and other non-biodegradable waste.
  • Put down or pour to the toilet, sink or the plant itself the waste, which can block the pipes and/or all system, eg., cat litter, cigarette butts, garden chemicals and paints, automotive oil filters and engine oil, medical drugs, construction waste, sand, gravel etc.
  • Pour large quantity of oil and fat from fryers or pans. The allowable quantity of grease is the quantity remaining on the dishes and during the dish washing.
  • Even when the plant is not in use, it cannot be left empty! Ground pressure may affect the empty plant from outside, so it always must be filled with water.

Operating the plant is RECOMMENDED TO :

  • Limit chemical disinfectants which contain chlorine or active oxygen. Such disinfectants are marked with symbols Health hazard and Toxic.

  • Avoid a laundry day, and spread laundry through the week.
  • Do not exceed the doses of household chemicals and use it as subscribed on the package.
  • Use the same household cleaning chemicals, as the activated sludge will work more efficiently with familiar products.
How does it work ?

Wastewater treatment plants treat biologically

The system treats domestic wastewater biologically. Untreated wastewater is entering the system. Process of removal of organic pollutions and process of oxidizing nitrogen to nitrite develop in bioreactor when supplying compressed air and activated sludge. The anoxic processes are forming, when aeration is inactive (switched off): microorganisms are using the oxygen of nitrates, which allowing releasing gaseous nitrogen, i.e. removes nitrogen from wastewater. Phosphorus and activated sludge is sinking on the bottom of plant. Periodically settled phosphorus and exceed sludge must be de-sludged.

Technical parameters

Model People equivalent Hydraulic daily flow  Standard dimensions Power consumption 
Pieces of air-blower V, m³

Control box d/h

H, mm D, mm D1, mm H1, mm Pipe, mm
FEL/4 4 0,8 2290* 1520 1000 700* 110 0,42 1 2,4 800/400
FEL/6 6 0,9 2450 1720 1000 770 0,63 1 3,3 800/400
FEL/10 10 1,5 2510 2020 1000 700 160 1,05 1 5,0 800/400
FEL/15 15 2,25 2610 2420 1000 700 1,58 1 7,7 800/400
FEL/25 25 3,75 2890 2870 1000 700 2,63 1 12,7 800/400

Other inflow depths are available for this model. Ask the manufacturer.

Troubleshooting and problem solving
Symptom/Problem Possible reason Remedial action
1. Air blower is running but littleor no turbulence is observed inaeration chamber.This could be due to few reasons: a) blocked rubber diffuser a) disconnect air supply pipe, wash the rubber diffuser
b) leakage or air in air supply pipe, hose or fittings b) inspect pipes, hoses, especially at joints. Unblock as necessary
c) the condensate accumulates inside of air supply pipe or hose c) air supply pipe is laid without the slope.
Relay as necessary
d) worn air blower parts d) inspect air blower membranes, valves and diaphragm. Replace the parts or change into new one
2. A lot of white foam observed in aeration chamber. Foam climbs from the plant outside. NOTE: fresh white foam can be
observed 1 –3 days from the startup of the plant. It is natural phenomenon, meaning the growth of microorganisms
a) excessive use of laundry
a) don’t use a household chemicals for some time. The situation will return to normal after a day or few
3. Heavy dark-brown foam on the surface of aeration chamber a) activated sludge is very old a) make a jar test and de-sludge the plant, if  necessary
b) the plant is full of excess
4. Aeration chamber contents is greyish/blackish, may be felt
slight septic odour
a) the anaerobic processes take place in the plant, insufficient dissolved oxygen. See B a) – c). See. C a) – c).
5. Effluent is not clear, low quality, contains brown/black sludge particles, especially at peak-flow a) excessive hydraulic load from laundry and/or other activities a) reduce the frequency of laundry to 1 load per day
b) the plant is full of excess
b) make a jar test and de-sludge the plant, if
c) excessive layer of scum has
accumulated in the secondary chamber
c) make a jar test and de-sludge the plant, if necessary
6. Grease balls are observed in the aeration chamber a) excessive pouring of fat into the drain from the kitchen a) do not use household chemicals for some time. The situation will return to normal after a day or few. If the fat balls remain, remove them manually with the scoop
7. Thick dark sludge in secondary settler is being carried over the scum baffle a) low load of organic pollutions a) supply more organic matter (WC, shower, sink) and less chemicals and large amount of water into the plant for some time. The situation will return to normal after a few days
b) excessive load of organic pollutions b) Too many people use the plant. You should
appeal to designers for selection of correct size
or additional devices
c) influent before entering the
plant overstays on its way, it
being to fermented
c) inspect pipeline and control shafts for
blockages. Unblock if necessary
d) excessive use of acid chemicals, low pH of the influent d) don’t use an acid chemicals for some time. The situation will return to normal after a day or few
e) the plant receives nondomestic wastewater e) for commercial application you should
appeal to designers for or additional devices
f) the air blower is running not
f) inspect air blower membranes, valves and diaphragm. Replace the parts or change into new one. Don’t use a timer, if you do so
8. There is no circulation in air
Air lift is blocked Take the air lift out and unblock it with water
Technological parameters (certificates)

Wastewater treatment plants FEL complies with the standard EN 12566-3 + A2: 2013 “Small wastewater treatment plants up to 50 SGS. Part 3. Factory and / or on-site domestic wastewater treatment plants ’Annex ZA. 

The FEL FEL type was tested and certified by the German laboratory of PIA Gmbh Aachen (Notified Body, No. 1739). In 2017, a certificate was issued, on the basis of which the EU declaration of conformity is issued and the equipment is marked with the CE mark. 

The following results were obtained during the wastewater treatment efficiency test:


Certificates and declarations of products see here >>>

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