Amelioration of ultrafiltration process by lime treatment: Case of landfill leachate

Nowadays membrane ultrafiltration process is generally used in effluents treatment. However, at industrial level, this process has major limitations such as important membrane fouling. In this study, a pre-treatment with lime upstream ultrafiltration was envisaged. The effluent considered is landfill leachate. The final waste storage centres produce leachates resulting from the percolation of waters through the hidden waste mass. These effluents strongly charged in mineral and organic matters, must be treated before their release into natural environment. Concerning the cleaning up, results have shown that the selectivity of membranes has an important influence on elimination of pollution from organic source. As expected, any action of retention on salts and heavy metals has been shown. During the filtration of raw leachate, the fouling of membranes turns to be very important and does not allow reaching satisfactory productivity no matter the cut-off limit. There seems to be no impact from hydrodynamics on velocity circulation higher than 4 m s− 1; this shows the existence of a dense and adhesive deposit on the membrane. The pre-treatment by lime allows (i) to precipitate carbonates under calcium carbonates form and ii) to eliminate by co-precipitation humic acids that are responsible for irreversible membrane fouling. Industrially, the implementation of the pre-treatment may allow reducing the costs of an ultrafiltration unit at about 50% in terms of investment and from 5 to 30% for operating costs.