Degradation of ciprofloxacin with Fe(II)-activated peroxide and anaerobic digestion: Treatability studies in tap water and chicken waste

Selected advanced chemical and biochemical treatments were examined on effluents bearing the second generation fluoroquinolone antibiotic Ciprofloxacin (Cipro). Firstly, ferrous iron(Fe)-activated peroxide oxidation was applied to Cipro-spiked reaction solutions (Cipro=2 mg/L in pure and real tap water; pH=5.0–5.5). An optimum ferrous iron:peroxide molar ratio of 1:2 (100 μM:200 μM) existed for all studied peroxides. Fe/persulfate performed best closely followed by Fe(II)/peracetic acid whereas Fe(II)/hydrogen peroxide always performed worse. In pure water (Fe^{2 +}=100 μM; peroxide=200 μM; pH=5.0; T=22 °C), relative total organic carbon (TOC) removal rates averaged 60 % after 60 min treatment for Fe/peracetic acid and Fe/persulfate than for Fe/hydrogen peroxide (43 % after 60 min). In real tap water (TOC=3.8 mg/L; pH=7.5; adjusted to pH=5.5), Cipro removals slowed down and TOC removals decreased from 62 % to 37 % after 60 min Fe/peracetic acid treatment. Acute toxicity (Aliivibrio fischeri) originally being 48 % in the 2 mg/L Cipro-containing tap water decreased to 32 % after 60 min Fe/peracetic acid treatment. Secondly, anaerobic digestion was applied to raw chicken waste at a relatively higher Cipro (=15 mg/L) which showed quite high organics removal and substantial biogas recovery. Compared to 76 % soluble COD removal in the control reactor; 16 % less soluble COD removal was observed in the tractor bearing 15 mg/L Cipro. The highest volatile fatty acid yield of 617 mg COD/(g volatile solids added) was achieved with 5 mg/L Cipro that was 53 % higher than 15 mg/L Cipro-containing bioreactor. Although cumulative biogas production was suppressed by 30 % when Cipro exceeded 10 mg/L, Cipro was still well tolerated in the anaerobic treatment system.