The problem of diffuse pollution by individual housing can be tackled by in
stallation of individual wastewater treatment systems. At the moment there
are initiatives towards standardisation and certification of these systems
to ensure efficient installations. Treatment results of recently installed
individual plants prove to be very good towards BOD, COD and SS removal. Fa
ctors such as frequency of maintenance, control and mechanical breakdown ma
y however affect these promising results. Investment and operation costs pe
r PE are discussed and compared with a more centralised approach, emphasisi
ng the highly variable nature of these costs for individual wastewater trea
tment. Additional long-term experience is needed to evaluate the potential
weak points and achieve improved cost-benefit analysis.