Title: The effect of liming on antibacterial and hormone levels in wastewater biosolids Authors
Submitted to: Waste Management and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 15, 2013
Publication Date: May 22, 2013
Citation: Olszewski, J.M., Lozano, N., Haines, C., Rice, C., Ramirez, M., Torrents, A. 2013. The effect of liming on antibacterial and hormone levels in wastewater biosolids. Waste Management and Research. 48:862-870. Interpretive Summary: Recent awareness of the limitation of our waste water treatment technology at adequately removing drugs and endocrine disrupter compounds has led to studies to better understand how current procedures actually interact with these organic chemicals. A treatment which is widely used is lime stabilization for managing the soil wastes produced in these plants. In this project, two high-use bacteriostats, triclosan and triclocarban, and two major-discharge hormones, estrone and progesterone, were stabilized with a fine lime product and a coarse lime product in order to see what type of changes in the concentration of these chemicals might occur. Factors studied were initial exposure mixing times, lime particle size, and overall contact time, these were all compared against biosolids that were not lime stabilized. Of the two bacteriostats, triclosan destruction trend was most rapid and 14-day exposures seemed to become too dry and loss rates seemed to decline with these samples. For the hormones, the concentrations were much lower and estrone levels declined much like the bacteriostats, but progesterone levels actually increased after day 1 and 7 but drying seemed to slow down any trends by day 14. Coarse lime was more active at producing these observations than fine lime.
Technical Abstract: In order to meet Class B quality requirements, wastewater biosolids are regulated for pathogen levels, metal concentrations, and vector attraction. One common method to decrease pathogen levels in these solids is to stabilize them by lime addition (CaO), which raises the pH and temperature of the material for a prescribed amount of time. 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. Our 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.