project

Strengthening research into activated carbon filtration for micropollutant removal

Organic micropollutants (OMPs), including persistent compounds, are being increasingly detected in groundwater and surface water. Understanding the action of (surface water) treatment in the removal of OMPs is required to enable targeted and effective operational management measures. In many treatment processes, activated carbon filtration (ACF) provides an important – and sometimes the only – barrier.

However, there is inadequate understanding of the processes that can negatively impact the OMP removal efficiency of ACF, particularly when natural organic matter (NOM) is present in the water and on the activated carbon.

Influence of NOM on adsorption with activated carbon

For modelling purposes, the sorption of an OMP is often simplified by assuming that the NOM can be described as a single equivalent background component that influences the sorption isotherm of an OMP, and thus the sorption capacity of the carbon. This requires an experimental assessment of the sorption isotherm of the NOM. But with this simplification it is practically impossible with the model to produce a realistic outcome whenever the NOM has a different composition, or when a fraction of the NOM blocks pores in the activated carbon. We therefore want to study the effects of different NOM fractions – obtained through nanofiltration – on pore blocking and sorption, and how we could model these effects. Moreover, the kinetics of sorption onto granulated carbon, for both the NOM and the OMPs, is generally unknown and only partially described in the literature.

Link with ACF experiments in ongoing Joint Research Programme research

In related research within the Joint Research Programme with the water utilities, a measurement plan has been developed to clarify the nature of the interaction of NOM (fractions) and OMPs during sorption by activated carbon. With this research proposal, we aim to contribute to strengthening this measurement plan and attempt to answer supplementary questions raised by Evides.

The objective is to better understand the sorption and kinetics of OMPs onto granulated activated carbon under the influence of the presence of low- and high-molecular NOM fractions (in the carbon and in the water), so as to acquire a clearer picture of the (effects of) pore blocking, sorption and breakthrough of OMPs.

Outcomes

  • Insights regarding ACF and the removal of OMPs in drinking water production and, specifically, the removal of OMPs in surface water pre-treated by Evides,
  • (Matching of) the research objectives for ACF, as defined in the Joint Research Programme with the water utilities – i.e., insight into particle-size distribution at plants on a practical scale, modelling with representative particle size, determining isotherm and kinetics for OMPs in the presence (fractions of) NOM, and understanding and validation of the model through column experiments.

Activated carbon.