Publication - Decentralised sewage treatment plants
15 Nov 2016

Types, numbers and performance of decentralized wastewater treatment plants in the EU-15

Background and objectives

The ERASM project team has asked Lettinga Associates Foundation (LeAF) to offer its services within a research project that investigates the effectiveness of decentralized sewage treatment plants in removing surfactants and detergents. Decentralized sewage treatment plants are defined here as systems serving 1 – 100 persons (or population equivalents, p.e.). The objectives of this study are the following:

  1. Identification of the different types of (aerobic) small wastewater treatment systems and septic tanks used in the “old” fifteen EU countries (EU-15). The EU-15 include Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden, United Kingdom.
  2. Compilation of the number of different types of (aerobic) small wastewater treatment systems used in the EU-15 countries.
  3. Compilation of the treatment efficiency specifications (especially BOD removal and nitrification) of these systems.

The ERASM project group has the overall goal to assess to which extent (intermediate degradation products of) surfactants and detergents might end up in the environment (water, soil) through the effluents of small wastewater treatment plants. The aim of this study is to provide an overview of the current situation with respect to small wastewater treatment systems and identify the most applied systems in the EU-15. This information will be guiding for a follow-up that will probably consist of an experimental study into the removal of surfactants and detergents in one or more small wastewater treatment plants.
This study has focused on the EU-15 member states. However, during the course of the project the ERASM project team considered it important to also include some statistical information on the 10 new member states that entered the European Union on 1 May 2004.
Therefore, chapter 3 contains some information on the state of wastewater treatment in the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, the Slovak Republic and Slovenia.