Impact of environmental conditions on the suitability of microconstituents as markers for determining nutrient loading from reclaimed water

Nitrogen and phosphorous loading into waterways from designated beneficial uses of reclaimed water is a growing concern in many parts of the United States. Numerous studies have documented that organic microconstituents present in the reclaimed water can be utilized as indicators of its influence on surface water bodies. However, little to no information is available on the environmental attenuation of these microconstituents relative to the nutrients, which is a critical component in determining the effectiveness or limitations of those markers as a tool for elucidating their origins. In this study, the stability of selected markers (sucralose, carbamazepine, gadolinium anomaly, iohexol, and atenolol) was evaluated through bench-scale studies designed to simulate environmental conditions associated with biodegradation, adsorption, and photolysis. The primary pathway for nitrogen reduction was biodegradation (greater than 99%) while the highest phosphorous removal was due to adsorption (30-80%). Soils with low organic content were selected for this study. Sucralose was the most recalcitrant microconstituent in the environment with less than 15% removal by adsorption, biodegradation, or photolysis. Iohexol was too susceptible to photolysis (90% removal), and atenolol was susceptible to biodegradation (60-80% removal). Gd anomaly was fairly stable (less than 30% removal) in the environment. Carbamazepine was another efficacious marker for wastewater, but was susceptible (50% removal) to photolysis. Of the selected microconstituents, only atenolol showed any similarity with the attenuation observed for nitrate and none of the microconstituents showed any similarity with the attenuation observed for phosphorus.