Small sewage treatment plant and purification technology

System KLARO

The tried and tested: a two-stage, fully biological sewage treatment plant using the SBR process. The KLARO system is our "standard plant". It has been on the market since 2001 and has proven itself a thousand times over. Over the years, we have continuously developed the plant and added additional modules. The particular advantages of the KLARO are its robustness and flexibility.

  • In sizes from 4 to 1500 PE. (more about the sizes)
  • All types of waste water
  • Complete plant, retrofit

Structure - Two-stage SBR process

1st stage/chamber:
Sludge storage and buffer

  • Storage of primary and secondary sludge
  • Retention of settleable materials and floating materials
  • Storage of the supply water
  • Compensation of quantity- and concentration-related fluctuations in wastewater inflow

2nd stage/chamber:
Activated sludge stage in closed accumulation mode (= SBR reactor)

  • Biological purification with activated sludge
  • Nitrification and denitrification
  • Phosphate precipitation (optional)

Advantages and features

of the KLARO System

  • Separation of waste water and technology
  • Air pump instead of submersible pump
  • Retrofit kit made of stainless steel and waste water resistant plastic

  • With sludge storage or preclarification

  • Stable procedure against shock loads and underload
  • Stable cleaning performance even in winter
  • High operational reliability
  • Mature technology - on the market since 2001 - in use worldwide

  • Independent of container material and geometry
  • All sizes up to 1500 PE
  • All approvals

  • Wide range of process customization options via the control system

  • Low sludge accumulation - no desludging during the 38 weeks PIA test
  • For sludge removal, only the sludge storage tank and not the entire plant must be emptied
  • Low energy consumption through fine bubble ventilation

  • Low maintenance
  • User-friendly, because of automatic operation

The KLARO SBR-cycle


1. Loading phase

The raw wastewater temporarily stored in the sludge storage/buffer is fed into the SBR reactor via a compressed air jack. This is arranged so that only water free of solids is pumped. A special design of the jack guarantees a minimum water level in the sludge storage tank. A limitation of the water level by further components (e.g. by a float switch) is therefore not necessary.

2. Aeration phase

The waste water is aerated and mixed with membrane aerators, which are mounted on the floor. The required compressed air is produced by an air compressor, which is installed in an external control cabinet. The aeration is usually intermittent. This aeration causes two effects at the same time:
• The microorganisms of the activated sludge are supplied with oxygen, which is necessary for their metabolic activity and thus for the decomposition of the pollutants
• There is intensive contact between wastewater and bacteria

3. Sedimentation phase

During the 90-minute settling phase there is no aeration. The activated sludge may sediment. A layer of sludge forms at the bottom and a clear water zone in the upper area.

4. Sludge removal and clearwater extraction

The clear water is conveyed out of the SBR stage by means of a compressed air hoist. The special construction of this siphon
• Minimizes the unwanted penetration of activated sludge into the siphon during the aeration phase by means of an air barrier (see page 28)
• Ensures that a desired minimum water level is maintained in the system without additional components
Excess activated sludge is returned to the sludge storage chamber by means of an air-lift pump.

Cleaning performance

The KLARO system achieves excellent effluent values, comparable to municipal sewage treatment plants. This is confirmed by the results of tests and the thousands of plants in operation worldwide, which are regularly maintained and checked.
Over the years, the system has been practically tested several times at the PIA testing institute according to EN 12566-3 - also in connection with additional purification stages such as P-precipitation and hygienization. In addition, voluntary tests were carried out such as underload test, vacation home test, ...

Results of the practical test according to EN12566-3:

  • Very good cleaning performance
  • Very good nitrification
  • Stable discharge values
  • Trouble-free operation
  • Low power consumption
  • Low sludge accumulation detected (sludge disposal frequency "zero")

Effluent values

Wastewater parameterEffluent values*Efficiency*
COD48 mg/l92,3 %
BOD56 mg/l97,5 %
NH4-N8,3 mg/l75,8 %


16 mg/l67,5 %

3,1 mg/l

56,9 %

SS7 mg/l96,7 %









6 months of downtime do not matter to KLARO systems!

PIA Test shows that KLARO also has the right system for vacation homes!

In many regions of Europe there are vacation or second homes. These are only visited very irregularly or are not used at all for a long time.
Until now, it was said that SBR systems were not suitable for this purpose - KLARO proves the opposite with its system.

At PIA we have tested a KLARO Easy 5 PE with P-precipitation.
After the plant ran under normal load, we stopped the inflow 100%.
For 26 weeks (6 months) this plant did not receive any waste water and ran "only" in vacation operation during this time.
The testing of the cleaning was already done from the first day of inflow.

The extreme underload already affected the biology very much during the shutdown.
Nevertheless, the KLARO small sewage treatment plant was able to achieve top results in a very short time.

  • The BOD5 was already well below 10 mg/l on the first day of recommissioning.
  • The Pges. value was already 0.5 mg/l on the second day.
  • The AFS was clearly below 10 mg/l within the first 3 days.

The certified conclusion is that small sewage treatment plants with KLARO technology regenerate extremely quickly and achieve good effluent values very quickly
>> To the KLARO test certificateof the vacation home test

Quality since 20 years

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