Mogućnost primene i efikasnost elektrokoagulacione tehnike u preradi podzemne vode sa visokim sadržajem prirodnih organskih materija / Appliance and efficiency of electrocoagulation in the treatment of groundwater with high concentration of natural organi

The aim of this research was to investigate possibility of appliance and the efficiency of electrocoagulation/flotation (ECEF) in the treatment of groundwater with the high concentration of natural organic matter and arsenic under laboratory conditions. A continuous electrocoagulation-electroflotation (ECEF) reactor was designed, built, operated and its operational parameters have been optimised. The influence of the ECEF reactor operational parameters such as, flow rate, A/V ratio, interelectrode distance and current density as well as conductivity and the initial pH of the solution were investigated and optimized in two phases of research. In the first phase of research the performance of the ECEF reactor has been evaluated using a synthetic humic substances solution Fluka (CAS No. 1415-93-6). In the second research phase the performance of the ECEF reactor has been evaluated using groundwater samples which are taken from the City of Zrenjanin groundwater sources. All results of this study has showed that ECCF treatment is a promising energy efficient purification technology for the treatment of groundwater containing high concentrations of NOM and arsenic. The processes of groundwater ozonation before ECEF treatment has shown positive effect on NOM electrocoagulation/flotation removal efficiency as well as has shown positive effect on reduction of ECEF reactor specific electric energy and aluminum electrode consumption. The highest NOM removal according to UV 254 absorbance and DOC was 82% and 71%, respectively, (relative to raw groundwater) as well as arsenic removal efficiency of 85% (6.2 micro;g As/l), meeting the drinking water standards of 10 ;micro;g/l was achieved with ozone doze of 0.68 mg O3/mg DOC and the following reactor operation parameters: current density 5.78 mA/cm 2lt applied potential 17 V, inter electrode distance 1.2 cm, flow rate 4.3 l/h, A/V ratio 0.248 cm-1, initial groundwater pH value 5.0. The specific reactor electric energy and electrode consumption were 1.66 kWh/m3 and 75 g Al/m 3 respectively.The basic lack of the continuous ECEF reactor used in this research was residual concentration of aluminium in the treated groundwater which was 7 times higher (1.55 ;plusmn;0.20 mg Al/l) than the maximum allowed concentration according to the Serbian low (0.2 mg Al/l ). Additional optimization 150 of the reactor operational parameters flow rate, electrode distance and ozone doze in this phase of research didn’t result in the reduction of the residual aluminum concentration of treated groundwater.