Application of electrocoagulation to water with low conductivity

The wastewater and drinking water sector in the Netherlands and Europe is committed to reducing its CO2 footprint. This also includes a desire to reduce the use of chemicals. During drinking water production, an iron flocculant can be dosed into the water to remove turbidity, phosphorus, NOM and arsenic, and to treat backwash water. Electrocoagulation offers a promising alternative to this chemical coagulation, thanks to its small CO2 footprint and high coagulation efficiency; moreover, it does not require any flocculant transport and storage.

This pilot study investigates the applicability of electrocoagulation for the treatment of water with low conductivity (≤600 μS/cm, a typical value for surface water, groundwater and rapid-filter backwash water), and seeks to determine which water-quality and operational parameters are crucial to this process.


In the application of chemical coagulation in drinking water production, the slow sludge settling velocity and the low dry-matter content of the iron sludge often pose problems. Electrocoagulation can produce thicker and better settling sludge compared to conventional coagulation. During electrocoagulation Fe hydroxides (iron flocs) are formed in situ, through the electro-dissolution of a sacrificial anode. Fe(0) oxidises to dissolved Fe(II), which then settles as iron floc sediment.

The advantages of electrocoagulation are:

  • No need for chemicals dosing; transport and storage costs for chemicals are eliminated.
  • Generation of thicker flocs that settle more quickly than in conventional coagulation.
  • Lower operational costs than in conventional coagulation. A KWR preliminary study showed that electrocoagulation can reduce operational costs by half [800 k€/Mm3 for electrochemical dosing of Fe, versus 1600 k€/Mm3 in operational costs for the treatment of rapid-filter backwash water (WTP Drost) with conventional coagulation (40% w/v)]. In addition, a preliminary LCA study of KWR with SimaPro 8 showed that electrocoagulation has a considerably smaller environmental impact than conventional coagulation. Moreover, the pH does not fall and no chloride is added to the water.


The comparison of electrocoagulation with coagulation using conventional flocculants is conducted through a pilot laboratory test and a desk study. KWR’s pilot has a capacity of 20 l/h, is equipped with 4 iron electrodes, and consists of a reactor, and a flocculation and a sedimentation compartment. The process variables are the iron release into the water and the gap between the electrodes. The iron release is controlled with the current and voltage supplied to the electrodes. The pilot’s results will be theoretically extrapolated to the design of a working installation.


The pilot experiments with rapid-filter backwash water (Dunea or Brabant Water), and surface water from the De Blankaart reservoir (De Watergroep, Belgium), should provide insight into the possibilities of applying electrocoagulation for the removal of turbidity, suspended solids, phosphorus, arsenic and organic matter.

The specific objectives are to:

  • Study the efficiency of electrocoagulation for the destabilisation of suspended solids.
  • Study the efficiency of electrocoagulation for the removal of dissolved compounds, such as NOM and phosphorus from water.
  • Determine the mechanisms of Fe precipitation in the electrocoagulation reaction, and study the performance of electrocoagulation under various water-quality conditions (electrical conductivity, suspended solids, pH, dissolved components, etc.), and operational conditions (current/voltage applied, electrode gap, dissolved oxygen, mixing speed, etc.)
  • Gain an understanding of the sedimentation and thickening behaviour of iron sludge.

When the project partners conclude on the basis of the lab experiments that electrocoagulation shows sufficient potential, a follow-up phase will begin involving long-term experiments on site. This will make it possible to answer a variety of research questions that cannot be answered in lab experiments. There is the hypothesis that microbial growth or iron precipitation could foul the electrodes over time, which would decrease the electrocoagulation efficiency because of the diminished solubility of the anode. A pilot installation should provide answers to various research questions. The research is conducted in Bergambacht (Dunea), using surface water from the Lek river and rapid-filter backwash water.

This follow-up research should provide:

  • Insight into the performance of electrocoagulation under seasonal changes in surface water quality.
  • Insight into fouling issues affecting the electrodes under extended operation, and as a function of water quality (surface water versus backwash water).
  • Insight into the settleability and filterability of the iron sludge, including a detailed study of the sediment’s structure, colloidal stability, water content, etc., through techniques such as SEM/TEM microscopy and laser diffraction (XRD).
  • Optimisation of the design of an electrocoagulation reactor based on the field trial insights regarding, for instance, the electrode gap, electrode connection (parallel, series, etc.), electrode position in the reactor, with/without flocculation chamber, etc. CFD modelling can be used for insight into the process design.


Pilot at KWR.