Recovering olaquindox and decreasing COD and salt concentrations in antibiotic wastewater by multiple freeze-thaw processes and crystallization

摘要

Wastewater from olaquindox-producing factories contains high levels of salts and organics. In this study, we investigated the multiple freeze-thaw technology to recover olaquindox from wastewater and decrease its chemical oxygen demand (COD) and salinity. Results suggested that under lower ice formation rate, the removal efficiencies of COD, electric conductivity, ammonia nitrogen and total nitrogen could reach 99.4%, 98.2%, 98.7% and 98.5% respectively. Higher ice formation rate, however, promoted wastewater concentration and volume reduction. A liter of wastewater concentrate can recover 11.5 g solid through a simple crystallization step at 4 degrees C for 12 h. This substance contained mostly olaquindox based on Raman infrared spectroscopy, scanning electron microscopy, and energy dispersive spectrometry. An industrial-scale wastewater treatment process, which the theoretical cost is one seventh that of conventional technologies, was then proposed to recover olaquindox and treat wastewater. (C) 2019 Elsevier Ltd. All rights reserved.