Novel advanced treatment of physically treated effluent from herbal decoction pieces wastewater using a combined ozone/persulfate-UBAF process

Performance of ozone/persulfate-UBAF used for advanced treatment of physically treated effluent from herbal decoction pieces of wastewater was investigated in a pilot scale experiment. Under optimum conditions - i.e., an initial pH, temperature 13-27°C, 30 min of oxidation, 35 mg/L O ₃ dosage, S ₂ O ₈ ^2- /COD (g/g) ratio (0.15), gas/liquid ratio in UBAF (3), hydraulic retention time in UBAF (5h) - the COD and NH ₃ -N removal efficiencies were 87.54-89.53% and 82.94-86.77%, respectively. Under optimum conditions, ozone/persulfate oxidation lowered pH values by about 0.1 pH units (average value), presented lower OCC (from 0.14 to 0.16 kg O ₃ /kg COD removed), and significantly improved the wastewater biodegradability from 0.16 to 0.55 (average value). Compared with O ₃ /H ₂ O ₂ oxidation, the ozone/persulfate system achieved a better enhancement effect in wastewater treatment (i.e., decreased 24.0% OCC and saved 11.4% in operational costs). Furthermore, the COD removal rate in ozone/persulfate oxidation stage followed the first order ln(C/C ₀ ) = -0.0167t, and the COD concentration in UBAF effluent was expressed by the model C/C ₀ = exp (-0.2940/L ^0.0912 H) at various hydraulic loading rates for maintenance and selection of UBAF. Finally, the study proved that the combined process was an efficient technology in treating physically treated effluent from herbal decoction pieces wastewater.