Retrofitting a small sewage treatment plant - what is possible?


Many older small wastewater treatment plants need to be modernized. For which reason this must be done, and what is to be considered, is explained here.

New EU Water Framework Directive

With 2015, a new, stricter EU Water Framework Directive will enter into force. In addition to the many changes, it is here among other things that every small wastewater treatment plant must operate the wastewater treatment with a biological stage.

As a result, a higher flow quality is achieved. This should help to better protect waters.

Many older systems must therefore be retrofitted. The modernization is required by the authority and must be carried out by the operator himself. Otherwise, a withdrawal of the water rights permit for the operation of the small sewage treatment plant threatens.

Retrofit over finished retrofit kits

Many manufacturers offer retrofit kits for older three-chamber septic tanks. For smaller systems such retrofit kits usually cost from about 2,500 to 3,500 EUR, for larger systems they are correspondingly expensive.

In most cases, extended maintenance and test requirements are associated with it. However, two servicing per year are standard in most modern plants in the replica.

The replica plants must comply with the cleaning classes prescribed by the authority. Cleaning classes are labeled with letters, and occasionally additional cleaning requirements for wastewater treatment are added. They are labeled with letters preceded by a + sign.

Financial burden for retrofitting

In many cases, the retrofitting means a considerable cost for the operator. Since it is mandatory, these costs are unavoidable. There are only subsidies in some federal states.

In Bavaria and Thuringia the funding is 1,500 EUR, in Saxony at 1,000 EUR. The installation of a new plant in Saxony, however, also funded with 1,500 EUR. Mecklenburg-Vorpommern shoots 750 EUR, Schleswig-Holstein 770 EUR.

Tips & Tricks

A conversion to near-natural processes such as wetland plants may also be worthwhile in the course of the conversion in some cases.


Video Board: MixAirTech Wastewater Treatment Plant Retrofit