Continuous culture biodegradation of simazineʹs chemical oxidation products

Experimental studies were conducted to assess the continuous culture biodegradation of s-triazines which originate from the chemical oxidation of simazine. Simazine is a herbicide found widely in surface and groundwaters. The four s-triazines selected for study, didealkyl atrazine (CAAT), ammeline (OAAT), ammelide (OOAT), and cyanuric acid (OOOT), originate from the ozone/UV oxidation of simazine. Decreases in continuous culture net growth rate, decreases in C:s-triazine-N feed ratio, and increases in inorganic nitrogen either through addition to the feed or by nitrogen fixation resulted in poorer s-triazine removal. For each process variable studied, the reduction in removal efficiency was s-triazine specific. In general, the greatest reductions in removal efficiency was observed for CAAT followed by OAAT, OOAT, and OOOT indicating that the s-triazine ring substituent group is an important factor in determining its effectiveness as a nitrogen source for microbial metabolism. The relationship between ring substituent and s-triazine metabolism demonstrates the beneficial role that chemical oxidation can play in subsequent s-triazine biodegradation. The application of chemical oxidation may enable the use of existing biological process infrastructure, primarily municipal POTWs where nitrogen limitations do not typically exist, for the treatment of s-triazines.