An heterotrophic/autotrophic denitrification (HAD) approach for nitrate removal from drinking water

An heterotrophic/autotrophic denitrification (HAD) approach supported by cotton and zero valent iron (ZVI) was proposed for nitrate removal from drinking water. Preliminary batch tests were performed to investigate the behaviour of ZVI and nitrate rich water system. Afterwards the HAD process was tested in continuous pilot-scale column reactors containing 380 g of cotton and 150–300 g of ZVI (R2–R4) and a blank reactor (R1) filled only with 380 g of cotton (cotton supported denitrification, CSD). The performance of the reactors was evaluated according to volumetric nitrate removal, stability with time and by-products formation.The HAD reactors, in particular, the HAD with 300 g of ZVI (R4), showed higher volumetric nitrate removal efficiencies (from 0.235 to 0.275 kg N m−3 day−1) than the CSD reactor (0.190 kg N m−3 day−1). Furthermore, released by-products such as soluble iron and ammonium were limited to very low levels (<0.095 and <1.25 mg l−1, respectively). The promising high performance obtained by the HAD shall be evaluated for in situ application as further study.