RESUMO
The present study investigates the removal of six selected pharmaceuticals from municipal wastewater in two membrane bioreactors (MBRs) with and without powdered activated carbon (PAC) addition. Two approaches were carried out for obtaining different carbon dosages related to the influent: (1) with a fixed solids retention time (SRT) and varying PAC concentrations; (2) with varying SRTs and a fixed PAC concentration. The results reveal that a PAC dosage related to influent of 21 mg L-1 and SRT of 20 d are optimal. The first approach achieved a better removal performance than the second. The removal of amidotrizoic acid (up to 46%), bezafibrate (>92%) and iopromide (around 85%) were mainly caused by biological process, but were also enhanced by PAC addition. Efficient removal (>95%) of sulfamethoxazole, carbamazepine and diclofenac were highly dependent on the PAC dosage. However, carbamazepine shows re-metabolization properties during biological processing. Decreasing the SRT as done in the second approach, not only increased the PAC amount, but also decreased the mass of activated sludge and reduced the capability to degrade complex organic matter. Consequently, biodegradability and adsorbability played decisive roles in the removal of each compound.
RESUMO
COD decreased obviously in normal molasses wastewater after anaerobic treatment, however, concentrations of nitrogen and phosphorus were still higher in the effluent which seriously damaged the ecological balance. In this study, aerobic granules cultivated in sequencing batch airlift reactor (SBAR) were carried out for treating the effluent; phosphorus removal processes and characteristics were discussed as well. The mean diameter of aerobic granules cultivated by multiple carbon sources (acetate, propionate and butyrate) was 1.7 mm. The average phosphorus removal efficiency was 90.9% and the level of phosphorus in effluent was only 1.3 mg x L(-1); TP released per COD consumed was 0.571 and the specific rate of TP released was 5.73 mg x (g x h)(-1). NO3(-) -N usage of phosphorus accumulating organisms (PAOs) improved during denitrifying process because the concentration of propionate and butyrate increased in multiple carbon sources which means the phosphorus uptake efficiency increased when per NO3(-) -N consumed. Phosphorus content represented a stronger correlation with magnesium, calcium and ferrum contents in aerobic granules and their extracellular polymeric substances (EPS), the phosphorus adsorption by EPS could enhance phosphorus removal. 61.9% of phosphorus accumulating organisms were denitrifying phosphorus accumulating organisms in aerobic granules and TP uptake per NO3(-) -N consumed was 1.14 which was higher than that of aerobic granules only cultivated by acetate.
