We find the cause (compressor, membrane, air line, airlifts, pump or sludge regime) and fix it. Send a request with the plant model and the symptoms; we will contact you within 5 minutes of receiving it.
Before you send a request: what to check yourself
- Whether there is power: whether the circuit breaker has tripped and whether the compressor is plugged in.
- Whether there was a power cut. Once power is restored, the controller usually restarts on its own; for example, the AUGUST BASIC switches on after 2 minutes with the previous programme.
- Whether the compressor's air filter is clogged (it is cleaned every six months).
- Whether the plant's hatch has been flooded with rainwater.
If the signal then disappears and fine bubbles are visible in the aeration zone again, no repair is needed. For what the specific signals mean, read the BIO plant alarm page.
The most common faults and their causes
| Symptom | Possible cause | What we do |
|---|---|---|
| Alarm, the compressor is silent | Worn membrane, faulty compressor or controller, blown fuse | We check the power supply and the controller, and replace the membrane or the compressor |
| The compressor is running, but there are no bubbles | Leaking or disconnected air pipe, clogged diffuser, closed valves | We check the air line, clean or replace the diffuser, and adjust the valves |
| Strong smell | No aeration, too much sludge, grease or chemicals have got into the plant | We restore the aeration, pump out the excess sludge and do a sludge test |
| Overflow or high level | Clogged airlift or outlet, overloaded or frozen infiltration, faulty discharge pump | We clean the airlifts and the outlet, and check the infiltration and the pump |
| Cloudy effluent, floating sludge | Too much sludge, incorrect recirculation, overload | We pump out the excess sludge, and adjust the airlifts and the regime |
| Brown foam | Several possible causes | Manufacturers advise calling in a service technician immediately; we diagnose it on site |
Without air, the activated sludge turns anaerobic: the water goes dark and smells. The sooner the aeration is restored, the less likely it is that the sludge will have to be built up again from scratch.
Replacing the compressor (air blower)
The compressor is the only part of the plant that runs for most of the day, for example about 18 hours in AUGUST's standard programme. Small plants usually use electromagnetic membrane compressors. The parts that wear out are the membrane (the AUGUST instructions specify replacing it once a year) and the air filter.
If the housing, the coil and the valves are intact, a membrane kit is enough. If the motor has burnt out, the housing has cracked or the compressor overheats, the whole compressor is replaced.
When choosing a new compressor, we take into account:
- the air output (l/min) and pressure to suit the plant model and its depth, because a different capacity upsets the balance of the airlifts and the aeration;
- the type recommended by the manufacturer; if it is no longer available, we choose an equivalent based on its specifications;
- the location: in a ventilated room or a protective housing, not touching a wall, and the permitted distance to the plant (AUGUST: no more than 5 m);
- adjusting the valves and checking the aeration after the replacement.
If only the controller is faulty, the AUGUST instructions allow the compressor to be connected directly to the mains for the time being, so that the bacteria aren't left without air while the repair is pending. If the plant is still under warranty, contact the seller first: manufacturers' warranty terms require original parts or parts of no lower quality.
Sources, checked on 30 October 2026: AUGUST AT6–AT50 technical passport (compressor type, STANDARD programme ~18 h, membrane replacement once a year, filter every 6 months, distance up to 5 m, controller signals, what to do if the controller is faulty, warranty conditions); PURA 4-50 technical passport (blower filter cleaning, airlift adjustment); Cabinet Regulation No. 384 of 27.06.2017 (point 15.3).
How the repair works
- Request Give the plant's manufacturer and model, the symptoms and how long they have been going on. A photo of the controller display or of the open hatch helps us prepare.
- Diagnosis on site We check the power supply, the compressor, the air line, the airlifts and the pumps, and do a sludge test: a litre of mixed liquor, 30 minutes of settling.
- Repair or ordering parts We replace the most common parts (membranes, filters, air pipes) on site. If a part has to be ordered, we agree on a temporary solution.
- Restoring the plant We pump out the excess sludge if there is too much, and adjust the airlifts and the aeration.
- Document We record the work in the maintenance log and issue a document. After an unscheduled service, a copy of it must be submitted to the decentralised sewage system register within a month.
How much does it cost?
The repair price depends on the diagnosis: a membrane kit costs a different amount from a new compressor, and after an overflow the plant may also need pumping. If the plant hasn't been serviced for a long time, we recommend combining the repair with a service (see biological treatment plant maintenance).