ga Kampüsü,

Struvite precipitation from wastewaters has gained importance as a means of nitrogen and pho-sphorus treatment and recovery. While the aspects of process modeling and application have been widely studied, little attention was paid to process kinetics. This study attempted to evalu-ate the induction time of struvite precipitation for low ammonia concentrations and in the pres-ence of ions commonly found in natural waters. Determination of induction time was based on absorbance measurements while conductivity and pH of the solutions were also monitored dur-ing the process. Results of the experimental study indicate that the presence of foreign ions is important in determining the induction time along with the degree of supersaturation. The pres-ence of over 50 10–3 mol dm–3 sodium ions retarded induction time significantly. Calcium ions at 2.5 10–4 mol dm–3 concentration caused no marked change in the induction time. While carbonate ions had a slight effect, sulfate ions increased the induction time. Crystal mor-phology was also observed to be affected by supersaturation and the presence of foreign ions. Keywords absorbance monitoring impurities induction time struvite crystal shape struvite precipitation supersaturatio