The need to recycle (waste)water becomes highly critical due to depleting water reserves coupled with high water consumption accompanying the rapid population growth, urbanization and industrialization. Water quality and available quantity is therefore considered one of the top challenges of the 21st century. As such, both in China and in Belgium there is the need to develop and implement technologies that focus on water treatment and re-use. Furthermore, these technologies should be effective, scalable and have a low footprint. Electrocoagulation-flotation (ECF) is such an innovative treatment system which is gaining more attention in the last decade, since the local generation of an external current can nowadays be cheaply and sustainable achieved with solar panels. As such, the CO2 footprint of water treatment can be significantly reduced (water treatment is currently responsible for 1-5 % of the total greenhouse gas emission). The ECF technology offers an innovative method to induce coagulation species in-situ, by applying an electrical current through electrode pairs. Therefore, removing the need for additional chemicals and preventing the generation of secondary pollutants (chloride, sulphate, etc.), which are known problems in conventional (waste)water treatment plants. However, the technology is slowly evolving. On the one hand, the viability of the ECF technology has already been proven (for example by our own research), with effective removal of different pollutants (organic matter, phosphate, heavy metals, suspended solids). But on the other hand, the removal mechanism and conditions created in the reactor are not well understood yet, limiting the broad-based understanding of ECF. Also, research is still often performed by parallel arrangement of simple plate electrodes inside a reactor (batch mode) and few attempts are made to use more advanced set-ups, such as continuous flow or combining spontaneous flotation.

One key application of ECF in view of water re-use is the removal of silica as a pre-treatment for membrane filtration. Membrane filtration is deemed to be highly attractive for water re-use due to for example its smaller foot-print. However, silica scaling is a common problem encountered in membrane separation processes due to its low solubility. Indeed, the presence of silica in the feed solution can make filtration extremely difficult, since silica is very hard to clean from the membrane surface in the amorphous form and even harder when the silica forms a layer of scale on the membrane surface in the form of crystallized silica. The most common method of silica removal is by precipitation. However, applying traditional coagulation/flocculation along with sedimentation requires a large land footprint, which offsets the benefit of the less space required for the membrane process. As such ECF, as a sustainable technique typically requiring less footprint, can be applied as membrane pre-treatment.

In a globalised economy, locally developed and produced technology (in this case Flemish technology) can be applied in any place in the world (in this case China). However, follow up of the reactor operation, removal performance and energy consumption can be cumbersome. For this, online measurements present a solution. Therefore, there is a need to develop and investigate the possibilities to on-line and remotely measure the ECF reactor performance.