BIO-ELECTRICITY DRIVEN TREATMENT OF HIGH SALINITY GROUNDWATER CONTAMINATED WITH NITRATES

Groundwater constitutes one of the main sources of drinking water supplies, and its full exploitation is hindered by the progressive accumulation of nitrates mostly deriving from inefficient agricultural practices. Bioelectrochemical systems (BES) represent a promising option for the treatment of nitrate-contaminated groundwater. They combine the principles of microbiology and electrochemistry to achieve a low-cost reduction of nitrate to dinitrogen gas, without adding an external carbon source. This study presents the development of a resilient and sustainable bio-electricity driven technology for the treatment of high salinity groundwater contaminated with nitrates. The 2-chamber bioelectrochemical cell was fed continuously with synthetic groundwater simulating that of the nitrate vulnerable zone of Arborea (Sardinia, Italy), which is characterized by - -1 -1 high nitrate concentration (> 20-25 mgNO3 -N L ) and conductivity (> 2.5 mS cm ), as well as by the presence of other inorganic compounds such as calcium, manganese, etc. At a nitrogen loading rate of 44.7±2.4 mgNO -- 3 -1 -1 - -1 -1 N L d , the observed nitrate removal rate stabilized at 22 mgNO3 -N L d , and no nitrite was observed in the -2 -2 - -1 effluent. At steady-state, specific power consumption (SPC) was 0.9·10 ±0.09·10 kWh gNO3 -Nremoved , which is lower than well-established technologies (i.e. electrodialysis) and comparable with previous BES studies. Sensitivity tests carried out by adding calcium and manganese provided important information on their possible effects on overall system performance, which decreased as their concentration increased. Results were promising, however, there is still extensive room for improvement in order to achieve threshold limits for nitrates in - -1 drinking water indicated by World Health Organization and European legislation (11.3 mgNO3 -N L ).