The same procedure applies to the larger AT-8. We carry out maintenance in Riga and the Riga region and record all the work in the plant's maintenance log; send a request and we will contact you within 5 minutes of receiving it.
What the AUGUST AT-6 and AT-8 are
The AT series plants are made by the Lithuanian company UAB “August ir Ko”. They are factory-made activated sludge plants in a single polypropylene tank. Inside there is an anaerobic-anoxic zone, divided by partitions into a “vertical flow labyrinth”, an aeration zone, and a secondary settling tank with a flow regulator that evens out the peaks from a bath or a washing machine.
Air is supplied by an electromagnetic membrane compressor. It doesn't just aerate; it also drives three airlifts: mixing the sludge in the coarse particle bag, returning sludge from the settling tank, and internal recirculation. The plant is run by the AUGUST BASIC controller; in the standard programme the compressor runs for about 18 hours a day, and there is also a holiday programme and a weekend-house programme.
| Model | Residents | Flow | Organic load | Sludge growth |
|---|---|---|---|---|
| AT6 | 1–4 | 0.6 m³/d | 0.24 kg BOD5/d | ~1 m³ a year |
| AT8 | 1–6 | 0.9 m³/d | 0.36 kg BOD5/d | ~1.5 m³ a year |
The data come from the manufacturer's product pages. There are also variants (for example, AT6K, AT6 PLUS, AT6GB); the maintenance is essentially the same, but the technical passport of the specific plant always takes precedence.
What the manufacturer specifies for maintenance
| Task | Frequency per the manufacturer's instructions |
|---|---|
| Sludge concentration check | every 6 months |
| Excess sludge removal | 1–2 times a year, depending on the load |
| Compressor membrane replacement | once a year |
| Check of the airlifts, aeration and flow regulator | every 6 months |
| Coarse particle bag check | every 6 months |
| Compressor air filter cleaning | every 6 months |
The controller reminds you itself: after half a year of compressor running time it shows “REPLACE FILTER”, and after a year “CHANGE MEMBRANE”. The owner can look at the aeration, the airlifts and the coarse particle bag once a month, but sludge work and replacing parts are a job for the service technician.
How we service an AT-6
- Visual check Odour, foam, floating sludge, how the compressor is running and the controller's signals.
- Sludge test We let a litre of mixed liquor from the aeration zone settle for 30 minutes. The normal range is 300–600 ml of sludge per litre, optimally 400–500 ml; if there is more than 600 ml, the excess sludge has to be removed.
- Excess sludge removal We switch off the compressor, let the contents settle for 30 minutes and pump the sludge from the bottom. The difference in level between the chambers must not exceed 15 cm, so that the partitions aren't damaged; afterwards we refill the chambers evenly. At least 300 ml of sludge per litre must remain in the plant.
- Coarse particle bag We lift it out and clear out the waste that doesn't break down: textiles, plastic, hygiene products.
- Compressor We clean the filter, replace the membrane if it is due, and confirm this in the controller.
- Airlifts and valves We set the air with valves A–E: the sludge must flow continuously, neither too weakly nor too strongly, and there must be fine bubbles in the aeration zone.
- Log and document We record the work and the sludge reading in the maintenance log and issue a document for you to submit to the decentralised sewage system register within a month.
If the plant is installed in high groundwater, we don't empty the tank completely, because the manufacturer warns that it can be lifted out or crushed.
Warranty and the manufacturer's conditions
The AUGUST technical passport states that inspection and servicing are carried out by AUGUST specialists or authorised representatives. The warranty is 10 years for the underground part of the tank and 2 years for the electrical part (compressor, controller). It is valid if the plant has been maintained strictly according to the instructions and original parts, or parts of no lower quality, have been used in repairs.
We are not AUGUST representatives. If your plant is still under warranty, check the seller's warranty terms before ordering maintenance. If the warranty has expired, we carry out maintenance to the same instructions and record everything in the log, because the manufacturer requires it to be shown if any claims arise.
Sources, checked on 30 October 2026: AUGUST AT6–AT50 technical passport (how the plant works, maintenance intervals, sludge test, pumping procedure, signals, warranty); the manufacturer's product pages for the AT6 and AT8 (august.lt); Cabinet Regulation No. 384 of 27.06.2017 (points 4.3, 15.3): maintenance at least once a year unless the documentation states otherwise, and a copy of the document to the register within a month.
Signals and problems between services
- Steady green: the compressor is pausing; this is not a fault.
- Flashing green: the compressor is running.
- Steady red: the compressor is disconnected or faulty.
- Flashing red with a sound signal: there is no power; the controller keeps signalling from its battery for several hours.
- Brown foam, a strong smell or floating sludge over more than half of the settling tank surface: a service is needed.
If the compressor or the controller is faulty, see biological treatment plant repair.
How much does it cost?
AT-6 or AT-8 maintenance costs from €160. The price depends on the amount of excess sludge, whether the membrane and filter need replacing, and the distance outside Riga. Spare parts are listed separately at actual cost.