In this study, ultrasound (US), zero-valent magnesium (Mg0) and their simultaneous combination were tested at different Mg0
doses (0.5, 1, 1.5, 2 ve 2.5 g/L), pH values (2, 4, 7 ve 9) and ultrasonic powers (30, 60 ve 90 W) for nitrate reduction.
Ultrasound alone was found to be ineffective for nitrate removal at different pH values. Effect of ultrasonic power for pH
controlled operation, nitrate reduction was increased with increasing dose of magnesium powder. Ultrasound induced
profound effects on denitrification capacity of magnesium particles. For example, with controlling pH at 4, 95% of initial
nitrate was reduced by 2.5 g/L of magnesium powder within 60 min, while keeping the applying combined US/Mg0 for 30,
60, and 90 W ultrasonic powers at the same dose, required durations to achieve at the same nitrate removal efficiencies were determined to be approximately 30, 20 and 20 min, respectively. When pH was controlled at 7 and 9, up to 70% of nitrate was removed by 2.5 g Mg0/L dose after 60 min , but in the same conditions with 90 W ultrasonic power a complete nitrate reduction was attained only within 30 min. Effect of ultrasonic on magnesium surface activation and nitrate removal was arised more clearly at alkaline conditions, when particle surface passivation was increased at increased pH . Nitrogen gas
(N2), nitrite (NO2 ) and ammonium/ammonia (N4/NH3) were detected as the major denitrification by-products following
US/Mg0 treatment. As more ultrasonic power and magnesium dose were applied, the rate of conversion of nitrate to nitrogen gas increased significantly.