Your project -

A complete success with KLARO

You need a small wastewater treatment plant (up to 50 PE) or you have to modernize your existing plant? In the following we have listed the options available to you to make your project a success with KLARO.

We distinguish:

  • New construction: Delivery of a ready pre-assembled wastewater treatment plant with tank
  • Retrofit: Supply of a retrofit kit to upgrade an existing septic tank to a fully biological treatment plant
  • Extension: Enlargement of an existing wastewater treatment plant
  • Modernization: Outdated, no longer functional wastewater treatment plants can be refurbished

Important factors in planning include:

  • Size: the size of the plant is expressed in PE (population equivalent)
  • Regulatory requirements: In general, the lower water authorities of the cities and district offices are responsible
  • Choice of location of septic tank and control cabinet
  • Structural condition of the existing septic tank, if retrofitting is required

We will be happy to advise you here and can recommend regional specialist partners.

  • New plant

    You need a complete system. Here you have the choice:

    KLARO small wastewater treatment plant in concrete tank

    Our wastewater treatment plants are also available as complete plants in concrete tanks, with pre-installed set-up kit and sampling. Larger plants can be distributed to several containers. All necessary pipe connections are already prepared. In principle, we only offer monolithic tanks from various manufacturers. Depending on the installation depth, a cone or a flat cover can be placed on the tank. In addition, there are different manhole covers. For plants larger than 200 p.e., tanks made of in-situ concrete can also be used. Learn more about concrete tanks à Link concrete septic tanks

    Complete plants with concrete tanks are available for both clarification systems KLARO and KLARO One, also for larger plants.

    KLARO small wastewater treatment plant in plastic tank

    Our wastewater treatment plants are available as complete systems in plastic tanks of the type Carat, Carat XL and Carat XXL for underground installation. Set-up kit and sampling are already pre-installed. All necessary pipe connections are already prepared. Depending on the installation depth, a shallower (Mini) or a higher (Maxi) tank dome is available for the tank. By means of a telescopic insert, the manhole cover can be adjusted to the terrain with centimeter precision (it can even be tilted on slopes!). In the end, only the grass-green manhole cover can be seen in the garden. Learn more about plastic tanks à Link septic tanks plastic

    Such complete plants are available for both clarification systems KLARO and KLARO One, even for larger plants.

  • Reftrofitting

    With our innovative retrofit kits, old existing septic tanks can be upgraded with little effort to modern fully biological small wastewater treatment plants that meet all official requirements. This also applies to larger pits. The possibilities here are almost unlimited:  No matter whether tanks are made of concrete or plastic, single or multiple chambers, single tanks or several, round or rectangular, etc.

    Prerequisites are:

    • Required minimum volumes and water depths must be maintained
    • All chambers must be accessible
    • The structure of the old septic tank must be intact


    Retrofit kits are available for both clarification systems KLARO and KLARO One.

    Our retrofit kit usually consists of air lift(s), aerator(s), immersion foil(s), sampling, air hoses and mounting material. All components are made of wastewater-resistant plastic or stainless steel. In addition, there is also the control cabinet.


    The retrofit kit is adapted to your tank by us. For this purpose, we request the necessary data in advance, such as EW, diameter, chamber division, water depth, partition wall height and partition wall thickness.

    Learn more about retrofit kits with air lift technology
    Learn more about concrete septic tanks

  • Extension

    Especially in larger plants, existing septic tanks can often be integrated into the new concept, even if their volume is not sufficient for the entire plant. In this case, new tanks can be installed downstream of the old ones. In most cases, the existing tanks are used as sludge storage/buffers and the new ones for SBR reactors, because they can be delivered practically pre-assembled.

    Thanks to our modular principle, various subsequent modifications and extensions are also possible with little effort, even years later. This provides security for the future.

    For example, if the official requirements for cleaning performance become more stringent, it is possible to switch to another higher effluent class.

    If the size of the septic tank needs to be increased, we check again whether it meets the new minimum volumes. Experience shows that this is usually the case with retrofitted septic tanks (because septic tanks used to be larger than small sewage treatment plants today). Often, only minor modifications to the control cabinet are then necessary. If the existing septic tank is too small, a new tank can be installed downstream and combined with the old plant.

    Plant examples

  • Modernization

    There is now a large inventory of various small wastewater treatment systems that are 25 years old or older. Some of them are in need of rehabilitation. Typical problems are high power consumption, increasing susceptibility to malfunctions, frequent repairs, odors, and even exceeding the effluent values. Often there are also difficulties with the procurement of spare parts.

    We advise here how such plants can be made afloat again with as little cost and effort as possible.

    Measures can be:

    Replacement of components

    If defective or worn components need to be replaced, we recommend checking whether a 1:1 replacement makes sense or whether newer and more advantageous alternatives are possible. Examples:

    • Compressors
    • Valves
    • Control
    • Aerator

    Conversion of technical plants

    When extending or rehabilitating old plants, it should be checked whether this is still possible and reasonable with the existing old treatment system. Conversion to a modern KLARO-SBR system is often the better long-term solution.

    In principle, it should be noted that a conversion must be coordinated with the lower water authority. In addition, the building fabric of the tank must still be intact. Examples:

    • Conversion trickling filter
    • Conversion fixed bed
    • Conversion of immersion disk
    • Conversion pump SBR


    Conversion of non-technical systems

    There are also large old stocks of near-natural systems for biological secondary treatment, such as filter ditches, filter beds, plant beds, clarification ponds, etc. Structural deficiencies and insufficient maintenance have caused many of these systems to fall into disrepair. A "readjustment" or repair is hardly possible here. However, all these plants have a multi-chamber pit according to DIN 4261-1, which can be equipped with a KLARO retrofit kit. Here, too, an intact building structure is a prerequisite.

    Learn more about retrofitting


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In over 80 countries


Specialists in Bayreuth