Fate of antibiotics during membrane separation followed by physical-chemical treatment processes

Highlights: • Fate of antibiotic during combined membrane separation processing (CMP) was obtained. • Antibiotic was most rejected by hollow fibre membrane ultrafiltration (HF) about 83%. • Extra treatment has positive effect on antibiotic removal (AR) for CMP production. • P25, activated charcoal, fine halloysite, coarse halloysite were evaluated for AR. • P25 has considerable practical importance for the removal of antibiotics. Membrane separation technology has been widely utilised to obtain clean permeate and concentrated nutrients from biogas digested slurry. However, some antibiotics are frequently found in digested slurry. Antibiotic removal during the steps, including paper filtration (PF), hollow-fibre membrane ultrafiltration (HF), nanofiltration (NF) and reverse osmosis (RO), of combined membrane separation processing (CMP) remain poorly understood. Experiments were performed on a pilot-scale CMP plant to investigate antibiotic transport and rejection efficiencies in CMP products and analyse the antibiotic removal performances of additional treatments. Results showed average relative antibiotic rejection efficiencies of 50%, 83%, 28% and 14% for PF, HF, NF and RO during CMP, respectively. Each CMP product needed additional treatment for antibiotic removal. Antibiotic removal capacity followed the order of fine halloysite > P25 > activated charcoal > coarse halloysite. The average antibiotic removal rates for different CMP products ranged from 73.3% to 99.9%. But antibiotics can only be adsorbed by fine halloysite and must be degraded through other treatments, Thus, P25 has considerable practical importance for the removal of antibiotics, as antibiotics can be degraded during photocatalysis.