Avaliação e otimização de um processo eletroquímico por corrente pulsada na remoção de nitrato em água subterrânea na região do Cariri do estado do Ceará

Abstract

The pulsed current electrochemical technique was used in order to remove nitrate in groundwater. This work arose due to the water crisis in the State of Ceará and the need to use groundwater as alternative source of supply, however one of the difficulties in the use of groundwater is the presence of nitrate with a value higher than the maximum allowed value of 10 mg de N-NO3-/L established in the drinking legislation. To optimize the EC process for nitrate removal, a factorial design 24 was applied. Thus, the influence of the variables was studied: concentration of added sodium chloride, electrode spacing, agitation and pulse frequency. 16 tests were carried out in a reactor with four aluminum electrodes connected in parallel, monopolar, voltage of 13 V and test time of 20 min. The sample volume was 4 liters per batch, with an initial nitrate concentration of (10,00 +/- 0,39) mg de N-NO3-/L, sample conductivity of 523.9 uS . cm-1. The nitrate concentration was determined by the APHA-4500-NO3 B UV technique at 220 nm. A minimum of nitrate removal of 16.18% and a maximum of 23.17% were observed, with a standard deviation of 2.27%. The best efficiency of nitrate removal was observed with a frequency of 125 Hz, electrode distance of 2 mm, agitation of 200 rpm and without adding NaCl. The best condition observed in the planning, was applied in the treatment of an underground spring in the Cariri region with nitrate concentration of (20,00 +/- 0,36) mg de N-NO3-/L. The removal efficiency was 52%.