Biological treatment plant maintenance

What a service includes

1. Inspection and measurements We check the water level, the smell, the clarity of the outflow and the amount of sludge in the aeration chamber. A settling test in a container shows how much sludge there is in the water.
2. Compressor and aeration We clean the air filter, check the membranes and the air supply, and see whether the bubbles rise evenly in the aeration chamber.
3. Sludge pumping We pump out the contents of the settling chamber and the excess part of the sludge, leaving enough activated sludge in the aeration chamber.
4. Flushing We flush the airlifts, overflows, inlet and outlet pipes, and the walls where grease and crust build up.
5. Floats and controls We check the float switches, the alarm and the control unit settings; for SBR plants, the work cycles too.
6. Refilling and restart We fill the tank with water to the working level, switch the plant on and check that everything works.
7. Document We issue a maintenance document with our findings and recommendations. A copy of it is needed by the municipality's register holder.

Sludge pumping and flushing

Bacteria multiply in the aeration chamber, so the amount of sludge grows over time. If the excess sludge is not pumped out, it starts to flow out with the treated water, clogs the outlet or the infiltration system, and the plant no longer treats the wastewater. How often sludge must be removed is set by the manufacturer's instructions (Riga's binding regulations also require this); in practice, the frequency also depends on the load.

Pumping sludge from a BIO plant is not the same as emptying a septic tank. If everything is pumped out, the bacteria are removed along with the excess sludge, and the plant treats poorly for several weeks. That is why we empty the settling chambers but leave some of the activated sludge in the aeration chamber.

Flushing is the other half. Airlifts and overflows are narrow pipes in which grease and sludge build up. If an airlift clogs, sludge no longer returns to the aeration chamber, the water level rises, and the plant soon starts to smell.

Compressor, aerators and alarm

A compressor runs for years, but its membranes and filter are wearing parts. When the membranes wear out, the air supply drops: the plant does not stop at once, but treatment gets worse and a smell appears. Over time the aerators at the bottom of the tank become clogged, and the bubbles become large and uneven.

An alarm usually means a high water level (a blockage, or a pump or airlift failure) or a compressor problem. What you can check yourself: BIO plant alarm. If parts need replacing: biological treatment plant repair.

Do BIO plants need bacteria

You usually don't need to buy bacteria for a BIO plant: activated sludge forms from the domestic wastewater itself. Additives can speed up recovery after start-up, after a long break or after chemicals have killed the sludge, but they do not replace sludge pumping and mechanical cleaning. More: bacteria for biological treatment plants.

Plants from different manufacturers

We carry out maintenance according to the specific manufacturer's instructions, because plants differ in chamber layout, number of airlifts and controls. In private houses you will find plants from AUGUST, PURA, Sotralentz, Biokubas and other manufacturers; if you know the model, include it in your request.

Separate pages on two models: AUGUST AT-6 maintenance and PURA treatment plant maintenance.

Signs that maintenance is needed now

• A sharp smell near the plant or in the house.
• The outflow water is cloudy, brown or has flakes in it.
• Thick foam or a crust on the surface.
• The alarm has gone off or the red light is on.
• The compressor is not working, hums unusually or is very hot.
• The water level in the tank is higher than usual.
• More than a year has passed since the last maintenance.

How much BIO plant maintenance costs

A service with sludge pumping and flushing costs from €160. The price depends on the plant's volume, the amount of sludge to be pumped out, the distance outside Riga (~€1/km) and whether parts need replacing (membranes, aerators, floats). We price replacement parts separately after an inspection.

All prices: prices. If you don't have a plant yet: biological treatment plants.

What the rules require

Cabinet Regulation No. 384 requires you to run the plant according to the manufacturer's documentation, maintain the activated sludge and have technical maintenance carried out once a year by a suitable company (unless the documentation states otherwise). Within a month of the maintenance, you submit a copy of the maintenance document to the register holder.

In Riga, in addition, samples of the water discharged into the environment must be tested in an accredited laboratory once every two years, and the results submitted to the Riga Housing and Environment Department. Failure to comply with the rules can lead to a warning or a fine.