The effect of liming on antibacterial and hormone levels in wastewater biosolids

Abstract

This study analyzes the effect of liming on levels of triclocarban (TCC), triclosan (TCS), estrone (E1), and progesterone (P), two antimicrobial agents and two natural hormones, respectively. Factors studied include lime particle size, mixing time, and overall lime contact time. The study results suggest that coarse lime may be more active than fine lime due to less interaction with surrounding air. Both TCS and TCC concentrations were lower in coarse limed samples versus unlimed samples and the decrease was a function of time. A similar, but statistically insignificant trend in TCC and TCS levels was observed in fine lime samples with respect to unlimed samples. Liming was also found to decrease apparent E1 levels, with more notable decreases in samples amended with coarse lime. P-levels significantly increased after 1-day of contact time, stabilizing over the next 14 days of the study period. This increase and stabilization of P-levels was attributed to the pH and moisture-driven conversion of more chemically complex steroids into P.

Keywords:

• Lime stabilization
• biosolids
• progesterone
• estrone
• triclosan
• triclocarban.

Acknowledgments

This study was supported by DC Water, Washington DC. The authors would like to thank the following people: Dana Armstrong for her assistance in acquiring and preparing biosolid samples, Garrett Hughes for his guidance in sampling and equipment use at DC Water, and Krystyna Bialek for her technical support in the laboratory at the USDA.