Zeolites as novel adsorbent in water treatment (Zeotreat)

State-of-the-art
Currently, activated carbon filtration is the state-of-the-art for the removal of organic micropollutants. While it can remove a broad range of targeted organic pollutants, it will also remove non-targeted natural organic matter (NOM). NOM can severely reduce the adsorption capacity for targeted organic pollutants due to adsorption competition, change in adsorbent surface characteristics and pore blockage (Newcombe, Drikas 1997).

Small, easily biodegradable assimilable organic matter (AOC) needs to be removed as well, to ensure biological stability of water in the distribution network. An effective method for this is using biologically active activated carbon, although a disadvantage is that post-disinfection is required to inactivate excess biofilm. Adsorption onto zeolites could be an alternative method to remove AOC.

Innovation/technology
High-silica zeolites can be an attractive alternative adsorbent for activated carbon, as

• Most NOM molecules are larger than the zeolite pores (<1 nm), and consequently will not compete with targeted organic micro-pollutants or AOC for adsorption [Pelekani ea 1999, Ebie ea 2001, Knappe ea 2005, Hung and Lin 2005, Hung and Lin 2006].
• The adsorption is more effective with high-silica zeolites than with activated carbon when there is a close match between pollutant molecule size and zeolite pore size [Anderson 2000, Rossner 2008, de Ridder e.a. 2012].
• Zeolites can be regenerated in situ with oxidative techniques. This has advantages to the regeneration of activated carbon, which is done off-site by energy-intensive thermal treatment.

These advantages allow zeolites to treat a larger volume of water before regeneration is required, which reduces overall production costs significantly for drinking water companies. Also, more cost-effective regeneration techniques can be used. Until now, high silica zeolites are not used in water treatment to adsorb organic micropollutants and AOC.

Research questions
Currently, high silica zeolites are mainly used as catalyst for specific reactions in industrial processes, and the bulk of the existing literature is related to this application. Using them as adsorbent in water treatment raises new challenges that require investigation.

1. Can (combinations of) zeolites effectively adsorb a broad range of organic micropollutants or AOC?
2. How does NOM affect adsorption of organic micropollutants or AOC onto zeolites
3. Can zeolites be developed in a granular/extruded form with sufficient adsorption capacity and acceptable adsorption kinetics?
4. Can zeolites be effectively regenerated by oxidative treatment?

Funded by
TKI Watertechnology

Partners
Oasen, Evides, PWN, HWL, TU Delft

Period
1-1-2015 till 31-12-2018