Remediation Of Tetracyclines In Soils and Manure Amended Soils: A Long-Term Greenhouse Column Study.

The presence of Tetracyclines (TCs) in manure, soil, sediment, sewage, surface water, and groundwater has been reported in several recent studies. The presence of TCs in the environment is of great concern because even at ng L-1 levels, these molecules are biologically active and can affect critical developmental stages and endocrine systems of aquatic and terrestrial organisms. Also, there are concerns over proliferation of antibiotic-resistant bacteria, decrease in the effectiveness of medical antibiotics, and other potential adverse human health and ecological effects. In the current one year greenhouse column study, we evaluated the effectiveness of a waste by-product from drinking water treatment process; namely Al-based drinking water treatment residuals (WTRs) to immobilize and stabilize tetracycline (TTC) and oxytetracycline (OTC) in soils and manure amended soils. Two physico-chemically variant soil types (Immokalee and Belleglade series) were chosen based on their potential differences with regard to TCs reactivity. Bermuda grass (Cynodon dactylon) and corn (Zea mays L.) were used as control and test plants respectively. Cattle manure was collected from Rutgers Cook campus. Manure and soil samples were spiked with various concentrations of TTC/OTC (0, 1, and 10 mM) and amended at three rates (0, 2.5 and 5%) of Al-WTR. Soils, manure-applied soils, plants, and leachate samples were collected periodically for one year. Soil and manure-applied soil samples were subjected to solid phase extraction to understand retention and release mechanisms of antibiotics. Results show that compared to the unamended (no WTR) soils, leaching and mobility of TTC/OTC significantly (p<0.001) decreased by 44-68% within 12 months across all the WTR treatments tested. Leaching of TTC and OTC reduced significantly (p< 0.05) from soils and manure-applied soils amended with 5% Al-WTR as compared to those with 2.5% Al-WTR. Presence of Bermuda grass and corn reduced leaching of TTC/OTC by 6-9% compared to columns with no plant cover. Highest total leaching (time zero to 12 months) was observed in Immokalee, followed by Belleglade soil and manure-applied soil, showing physico-chemically dependent leaching behavior.  Data from SPE showed less than 12% release of the initial TTC/OTC concentration in both manure-applied soils and soils in different phases tested, indicating strong binding of TCs on Al-WTR. Results obtained from the current greenhouse column study are encouraging and will potentially help in developing an optimal low-cost remediation technique for TCs and other veterinary antibiotics using a waste by-product.

Keywords:  Tetracyclines, Soil, Remediation, Drinking Water Treatment Residuals, Greenhouse column study.