Nitrate removal with bacterial cells attached to quartz sand and zeolite from salty wastewaters

A mixed bacterial culture was acclimated to the removal of high nitrate-N concentrations (100-750 mg NO3-N L-1) from salty wastewaters. The experiments were carried out under anoxic conditions in the presence of 0.5, 1.5 and 3% (w/v) NaCl at different temperatures. The acclimated mixed bacterial culture was attached to quartz sand and zeolite. Denitrification was monitored in a continuous-flow bioreactor at different hydraulic retention times (HRT). Nitrate removal with cells attached to quartz sand and zeolite was completed at HRT of 167 h and 25 h respectively. Then brine denitrification with bacterial cells attached to zeolite was monitored for 85 days. Under the increased nitrate loading rate, nitrate removal was above 90%. Furthermore, during denitrification, not more than 0.5 mg NO2--N L-1 could be produced. It can be concluded that nitrate removal with the cells attached to zeolite is economically and operationally a promising solution to denitrification of brine wastewaters.