Nonautomated Biological domestic wastewater treatment system





Biological domestic wastewater treatment systems (wwtp) FEL are installed in areas where connection to the central sewer system is impossible. The systems are intended to treat wastewater from residential houses and individual residential units. The treated wastewater after biological wwtp can be discharged to the environment without harming the ecology, i. e. treated wastewater can be released to the roadsides, melioration ditches or into the surface water bodies. In the absence of water body, treated wastewater can be filtered into ground through the filtration wells or fields. Also treated wastewater can be used for lawn watering.

  • CE marked according to EN 12566-3
  • 15 years warranty
  • High treatment efficiency
  • Easy to ship and install 
  • Minimum maintenance cost
  • Treated wastewater is clear and odorless     
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"    

More about the product


Wastewater treatment plant can be started-up by the 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 air blower connected to the plant, and electric power connected to the air blower. Switch on the air blower. You should observe turbulence (bubbles) in central chamber. The aeration process is starts. Within first week of operation supply wastewater into plant only in urgent cases (i.e. WC, shower). Within first month 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 second month 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 air blower on 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 (see Technical parameters), concentration 4–6 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.

Watch the video how quickly and easily start the cleaning equipment of UAB Feliksnavis:

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 FEL plant consists of aeration chamber, secondary settler and air supply system (air blower and diffuser). The influent from the house first enters the aeration chamber. Its centre is equipped with small bubble diffuser. The supplied compressed air oxidizes organic pollutants. The circulation of activated sludge and pollutants takes place in aeration chamber. After start-up and a certain period of time bio-skin formed on the bio-load. When the circulating flow goes down, the concentration of the dissolved oxygen decreases, the bio-skin develop not only the processes of decomposing of organic pollutions, but also the processes of nitrification (an oxidation process of ammonia to nitrate) and denitrification (oxygen consumption from nitrates and nitrites). As a result, nitrogen concentration in the treated waste water is reduced. So, due to all these processes the treatment of wastewater takes place. Then treated wastewater and sludge fall into secondary settler. The separation process takes place: the sludge separated (precipitated) from wastewater. Then treated wastewater is carried over the scum baffle to the duct and goes out from the plant.

Biologically treated domestic wastewater is not harmful to the environment, so it can be discharged into flowing water bodies (rivers, canals, ditches). In absence of such possibility the treated wastewater can be discharged into the ground. Also it may be collected and used as technical water (lawn watering, car washing etc.).


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 2360* 1540 1000 710* 110 1,2 1 1,79 400/400
FEL-6 6 0,9 2340 1640 1000 850 1,73 1 1,95 400/400
FEL-10 10 1,5 2690 1780 1000 900 2,76 1 2,44 400/400
FEL-15 15 2,25 2800 2180 1000 900 5,04 1 3,67 500/400
FEL-25 25 3,75 3700 2380 1000 1130 160 7,32 2 6,73 800/400

* 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 little or no turbulence is observed in aeration 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 thesurface 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, lowquality, contains brown/blacksludge particles, especially atpeak-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 necessary
c) excessive layer of scum has
accumulated in the secondary
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
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
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 constantly 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
Technological parameters (certificates)

Biological wastewater treatment plants FEL meet requirements of standard EN 12566-3+A2:2013 Small wastewater treatment systems for up to 50 PT - Part 3: Packaged and/or site assembled domestic wastewater treatment plants and Construction Product Regulation (CPR) No. 305/2011.

Biological wastewater treatment plants were tested in SZU Engineering Test Institute (Brno, Czech Republic).


Certificates and declarations of products see here >>>

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