Comparison of technology, costs and environmental benefit of wastewater treatment plants in mountainous areas in the alps

back to comparison of technologies

As the monitoring  results indicate both types of biological treatment systems - biofilm and activated sludge - can achieve similar results in case they are properly designed and operated. The main limiting condition concerns the energy supply as demonstrated in figure 1. There is only one exception that an activated sludge system is supplied by an autarkic photovoltaic energy source (compare chapter "energy demand"). Temperature represents another major restriction. No biofilm systems have been applied at sites operated during the winter season because the activity of the large biofilm surfaces could be reduced by cold air. Due to the much higher specific energy of water compared to air activated sludge systems are less climate sensitive. Fig. 2 shows the influence of load and size of the WWTP on the choice of the treatment system. Activated sludge applications indicate a preference for sites with high loading.

Fig. 1: Energy supply

Fig. 2: Influence of load