Removal of arsenic from groundwater rich in natural organic matter (NOM) by continuous electrocoagulation/flocculation (ECF)

• Arsenic abatement from groundwater rich in hydrophobic NOM by continuous electrocoagulation.
• Electrocoagulation led to 93% arsenic removal with 3.03 kW h/m3.
• Highest arsenic and NOM removal with the optimal residual Al obtained at pH of 5.03 ± 0.3.
• 30 min change of electrodes polarity successfully controlled passivation.

A novel technique of continuous ECF using bipolar Al electrode was attempted in this study to efficiently remove arsenic from groundwater rich in hydrophobic NOM (9.31 ± 0.52 mg C/L). The effects of several operational parameters such as, initial groundwater pH, evolution of temperature, conductivity and pH, electrode polarity time change on As and NOM removal efficiency were comprehensively examined by conducting 6 h long experimental runs. The average residual As in treated groundwater was 4.6 ± 0.4 μg/L. NOM removal according to UV254 absorbance, DOC and SUVA was 89%, 70%, 64%, respectively. The highest As and NOM removal with the optimal residual Al below 0.2 mg/L was obtained at the same groundwater pH = 5.3 ± 0.3. The change of electrode polarity at 30 min successfully prevented electrode passivation and enabled highest As removal with the optimal residual Al in treated groundwater. Specific reactor electric energy and electrode consumption for operational current density of 8.86 mA/cm2 was 3.03 kW h/m3, 0.059 kg Al/m3, respectively. Indicative reactor’s operating cost at the optimal operational conditions was estimated at 0.25 €/m3.