Adsorption processes

Team
Markus Boller, Silvana Velten

Goal
To determine the significance of activated carbon (AC) adsorption within future process schemes for drinking water treatment including membranes and ozonation.

Description
In Switzerland, activated carbon adsorption is a process used in most modern water works treating surface waters. There is usually no specified task for the granular activated carbon filters (GAC) to remove single substances but rather to act as a general quality improvement process mainly by its biological activity. In recent years, GAC filters are mostly combined with a preceding ozonation step where substantial fractions of organic substances are oxidized to readily biodegradable compounds. These are further biochemically oxidized in GAC filters, leading to a more stable water with respect to potential growth and aftergrowth in holding tanks and distribution systems.

With the introduction of membranes into water treatment technology, the application of powdered activated carbon (PAC) became more important. The combination of PAC with ultra- or microfiltration revealed to be a viable alternative for the treatment of certain raw waters. The combination is considered to be a highly competitive treatment option compared to the more costly nanofiltration.

The project concentrates on the effects of activated carbon adsorption and on the parameters focused in this study such as NOM, AOC, taste and odour, and DBPs. These parameters are strongly influenced by ozonation. GAC or PAC are therefore considered as part of a treatment scheme following ozonation. Eventually, specific micropollutants are included in the study in order to demonstrate the potential of AC application on the removal of these compounds.