Membrane Bioreactor Combined With Nanofiltration And Reverse Osmosis For Advanced Treatment Of Landfill Leachate

There are several characters of landfill leachate, such as kinds of organic compounds, complicated water quality, variation concentration of composition and contaminations, heavy metal pollution. So it is difficult to achieve good treatment effect by the conventional wastewater treatment. In recent years, membrane bioreactor has be accepted widely as a treatment process for wastewater. In this paper, an anaerobic combined aerobic membrane bioreactor and anaerobic combinated GAC membrane bioreactor were used to treat old landfill leachate. To reach the purpose of wastewater reuse, advanced MBR treatment process combinated with nanofiltration and reverse osmosis has been introduced.The results showed that, both two kinds of membrane bioreactor can remove the suspended particles compeletly, COD and NH3-N removal rates in anaerobic-aerobic reactor were 81.5% and 92.41%, respectively. The removal efficiency of dissolved metal ions demonstrated that sludge had a better performance for high valence than monovalence ones. After a sharp membrane flux decline period, the flux fell in an slow decline period, and the membrane flux finally maintained at 0.0205 L·m-2h-1kPa-1. Membrane flux after cleaning predicted that 14.7% irreversible pollution was produced in MBR process. The average removal rate of COD was 84.7% in the anaerobic combinated GAC membrane bioreactor. The addition of GAC inhibited the growth of nitrifying germs in membrane bioreactor, so that the NH3-N removal decreased by 17.41% compared with first process. Cr, Pb, Cd, Cu were four kinds of heavy metal ions in the leachate. Variation of these heavy metal ions in the leachate was investigated. It was found that the removal efficiency of heavy metals are Cd>Cu>Pb>Cr, and the decline of removal efficiency went along with operation. After 10 hours fast fouling period, membrane fouling became slowly and the membrane flux eventually stabilized at 0.04 L·m-2h-1kPa-1. After NF treatment, the color of leachate can be completely removed, and the average removal rate of COD and NH3-N was 52.34% and 17.62% respectively. COD and NH3-N concentration in RO effluent was 12.39 mg/L and 2.6mg/L respectively. The final effluent after NF/RO process has successfully met the water reuse requirement of industry.