In this work the potential of dairy wastewater for denitrification process by means of a microbial culture of nitrificants and denitrificants was investigated. The aim of this work was to remove nitrate by using organic compounds from the dairy wastewater as an electron donors. The minimal ratio of COD/NO3-N of 10 (COD-chemical oxygen demand/NO3-N-nitrate nitrogen) was required to achieve complete reduction of NO3-N. The microbial culture of nitrificants and denitrificants, that was previously adapted on the dairy wastewater, carried out nitrate reduction with a different substrate utilization rate. The denitrification rate of 5.75 mg NO3-N/Lh was achieved at the beginning of denitrification when the microbial culture utilizes readily biodegradable COD. Further degradation occurred with the denitrification rate of 1.7 mg NO3-N/Lh.U ovom radu istražen je potencijal otpadne vode mljekarske industrije za proces denitrifikacije pomoću mikrobne kulture nitrifikanata i denitrifikanata. Cilj rada je bio ukloniti nitrat koristeći organske sastojke iz otpadne vode industrije prerade mlijeka kao elektron donore. Minimalan omjer KPK/ NO3-N (KPK-kemijska potrošnja kisika/NO3-N-nitratni dušik) potreban za postizanje potpune redukcije NO3-N iznosi 10. Mikrobna kultura nitrifikanata i denitrifikanata, prethodno prilagođena na otpadnu vodu mljekarske industrije, provodi redukciju nitrata uz različitu brzinu iskorištenja supstrata. U početku denitrifikacije mikrobna kultura troši lako razgradivi KPK i postiže brzinu denitrifikacije od 5,75 mg NO3-N/Lh. Daljnja razgradnja zbiva se uz brzinu denitrifikacije od 1,7 mg NO3 N/Lh
