Reverse osmosis and nanofiltration of biologically treated leachate

Abstract

Experiments of nano-filtration (NF) and reverse osmosis (RO) were conducted to remove most pollutants from the biological treated leachate. For example, the purified permeate after reverse osmosis treatment with spiral membranes reached effluent water quality as follows: COD of 57 mg O₂/l, BOD₇ of 35 mg O₂/l, and suspended solid of 1 mg/l which satisfies the discharge standards in Estonia. For both RO and NF, conductivity can be reduced by 91% from 6.06 to 0.371 mS/cm by RO and 99% from 200 to 1 mS/cm by NF. To test the service life of the RO spiral membranes, the process was able to reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) of biologically treated leachate by 97.9% and 93.2% even after 328 and 586 hours, respectively. However, only 39.0% and 21.7% reductions of P_tot and N_tot were achieved. As a result, neither RO (spiral membranes process) nor NF was able to reduce the total nitrogen (TN) to the required discharge limit of 15 mg/l.

Keywords:

• landfill leachate
• leachate characteristics
• pre-treatment
• biological treatment
• reverse osmosis
• nanofiltration

Acknowledgements

The authors acknowledge the support of the Estonian Environmental Investment Center. WZT thanks the Fulbright Scholarship Program by the F. William Fulbright Foreign Scholarship Board and the Bureau of Education and Cultural Affairs of the United States Department of State for supporting his sabbatical stay at TTU in Estonia from September 2009 to May 2010.