Microbiologist Mark Ibekwe, from the US Agricultural Research Service (ARS) and soil chemist Daniel Ashworth from the University of California-Riverside (UCR) have designed a model for an economical filter system which can remove antibiotics from wastewater.
The prototype system was constructed using four layers of natural materials: gravel, sand, soil, and biochar in a column 50 cm tall and 12 cm in diameter. The model was used to remove four antibiotics: amoxicillin, cefalexin, sulfadiazine, and tetracycline.
These antibiotics were selected because they are among the most common in wastewater treatment plant effluent. Conventional wastewater treatment systems are relatively effective at removing nutrients and bacteria but not as efficient at removing antibiotics.
The system successfully removed 98% of tetracycline, 91% of cefalexin, 81% of amoxicillin and 51% of sulfadiazine. The antibiotics had initial concentrations of 10 ppb, comparable to levels in municipal wastewater.
Amoxicillin and cefalexin removal were controlled by chemical degradation in the gravel layer, while sulfadiazine was removed by a combination of chemical and microbial degradation in the soil mixed with biochar layer. Tetracycline was removed by hydrolysis in the gravel layer.