effect of metal nanoparticles on biological denitrification process: a review

globally, increasing nitrate concentrations have become a significant environmental problem and a potential risk to public health. the world health organization (who) has set a limit of (10 (mg.l -1 )) no 3 - for human consumption and (100 mg.l -1 )) no 3 - for animals. water above these limits requires denitrification. nitrates causes cancer, blue-bay syndrome, hypertension and thyroid hypertrophy. several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. available technical data, experience, and economics indicate that chemical denitrification and biological denitrification are more acceptable for nitrate removal than other thechniques. this review article investigated the efficiency of denitrification of drinking water  and ground water by various methods, specially biological denitrification and chemical denitrification by nano particles specially nano scale zero valent iron (nzvi) and emerging biodenitrification by nano scale zero valent iron. also in this article, affecting factors on denitrification from drinking water evaluated.