Chemically cleaning of UF membranes fouled by oily waste water.

Abstract

The Ultra filtration membranes are used for treatment and reused of oily waste waters. The fouling of the ultra filtration membranes is caused due to inorganic and organic materials present in waste water that adhere to the surface and pores of the membranes and resulted in fouling and deterioration perforformance with increase in cost of energy and membranes replacement. In this experiment, Ultra filtration membranes fouling and cleaning were performed with oily waste water and selecting cleaning agents using laboratory scale cross flow membrane test unit. The result showed that the combination of cleaning agent that is metal chelating agent (Ethylene diamine tetraactetic acid) and an surfactant (sodium dodecyl sulfate (SDS) and sodium hydroxide were able to clean fouled membranes very effectively than the individual cleaning agent. The flux recovery percentage was found to improve with increasing cross flow velocity, temperature, pH and concentration of the cleaning solutions. Keywords-ultrafiltration; fouling; cleaning; surfactant; oily waste water. I. INTRODUCTION The fouling of membranes is typically caused by inorganic and organic materials that adhere to the surface and pores of the membrane and result in deterioration of performance (reduce flux of the membrane) with consequent increase in costs of energy and membrane replacement. A. Fundamental of Separation The forces of interaction between the membrane surface and particles in the solution are important in understanding the fouling phenomena. The normal basis for quantifying particle surface interaction is DLVO theory where the particle surface interactions in aqueous environments could be predicted by the summation of van der Waals and electrostatic double layer forces. Reducing the interaction between the particles and the membranes as much possible can reduce the fouling phenomena. This can be achieved when the critical value (flux and pressure) arises as a balance between the hydrodynamic force driving solute towards the pore and electrostatic forces opposing the motion. Critical flux stems from the concept that the higher the flux the stronger is the drag force towards the membranes. The stronger concentration polarization and higher the compaction of particles. Critical flux is defined as the limiting flux value below which a flux decline over time does not occur.(1).the number of parameter influenced this critical flux have been discussed in detail can be found(2).It is maintained that if one operates below the critical flux the fouling can be avoided or minimized. The fouling is common to all types of membrane separation. B. Fouling Membranes fouling are an extremely complex phenomenon that has not been defined precisely. In general the term used to describe the undesirable formation of deposits on membrane surfaces. This occurs when rejected particles are not transported from the surface of the membrane back to the bulk stream. The foul ant are typically colloidal materials of one types or another and their properties and interaction with membranes dominant fouling /cleaning processes. Colloids are defined as fine suspended particles in the size range of few nanometers to few micrometers. Examples of common colloids sizes foulant includes inorganic(clay, silica salt and metal