Abstract
Nitrate groundwater contamination is an issue of global concern that has not been satisfactorily and efficiently addressed, yet. In this study, a 2-stage, sequential bioelectrochemical system (BES) was run to perform autotrophic denitrification of synthetic groundwater. The system was run at a 75.6 mgNO3−-N L−1NCC d−1 nitrate loading rate, achieving almost complete removal of nitrate (>93%) and Total Nitrogen (TN) (>93%). After treatment in the first stage reactor values of effluent nitrate compatible with the EU and USA limits for drinking water (<11.3 and 10 mgNO3−-N L−1, respectively) were achieved. Nitrite and nitrous oxide were observed in the first stage’s effluent, and were then successfully removed in the second stage. The observed nitrate removal rate was 73.4 ± 1.3 gNO3−-N m−3NCC d−1, while the total nitrogen removal rate was 73.1 ± 1.2 gN m−3NCC d−1. Specific energy consumptions of the system were 0.80 ± 0.00 kWh m−3, 18.80 ± 0.94 kWh kgNO3−-N−1 and 18.88 ± 0.95 kWh kgN−1. Combination of two denitrifying BES in series herein described proved to be effective.
Highlights
IntroductionAn increase in groundwater nitrate concentration in recent years has been reported [4,5]
Groundwater is used in large part of the world as a drinking water source; the intake of nitrate-contaminated water may lead to several health issues
Autotrophic bioelectrochemical nitrate removal systems could constitute an efficient methodology for denitrification of drinking water groundwater supplies
Summary
An increase in groundwater nitrate concentration in recent years has been reported [4,5]. The main sources for nitrate in groundwater are anthropogenic, due to intensive use of fertilizers [6], other important sources are represented by leakages from sewage systems, on-site wastewater disposal systems, cattle feedlots, and spread of manure and sludge residuals on agricultural land [7,8,9]; this variety of sources is the main cause of the widespread diffusion of the contamination in different areas of the planet despite different land uses and development levels. Nitrate can naturally occur in groundwater, with background natural concentrations reported to be higher than. Nitrate has been identified as toxic [11,12,13]
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