NPK fertilizers, a nitro-phosphate type fertilizer, is produced through the Norsk-Hydro-ODDA technology. This technology has been modified to incorporate an effective wastewater evaporator system which reduces the amount of contaminated cooling water discharge. The wastewater passes through a series of evaporation steps whereby the vapors are used as wash water in the calcium carbonate filters and the concentrated solution is pumped to the neutralizers where it is mixed with the acidic NP solution and used to regulate the N/P205 nutrient ratio of the fertilizer. Through this modified technology, steam and electric energy consumption increases somewhat but such increases are balanced by the most effective utilization of nitrogen and the reduction of the wastewater stream discharge.