INTRODUCTION

• Filtration is the separation of a mixture of solids and fluids that includes the passage of most of the fluid through a porous media, which retains most of the solid particles of the mixture.
• The filtering media is the barrier that enables the passage of the liquid while it retains most of the solids, which accumulate in a layer over the surface or filter (filtering bed), so the fluid will go through the solids bed and the retention membrane.
• The Filterability Index Unit, “PEIF”, is a unit for demonstrating the filtering process through a porous media. It enables a water quality test to be made on a suspension to be filtered through sand or similar granular media.

GENERAL DESCRIPTION

• This unit utilises a bed of granular material, normally sand, which can be chosen by the student to suit his own purposes.The measurements taken with this unit enable a filterability index to be calculated which has significance in deep bed filter performance.
• The “PEIF” unit is a bench-top unit composed of a feeding tank, where the initial solution of water with solids in suspension is placed.
• During the normal operation, the tank is communicated with the sand filter upper part, through of a pipe.
• The filter lower part is communicated with the flowmeter. A regulation valve located at the flowmeter allows to change the flow which passes through the filter.
• The fluid pressure is obtained by means of the gravity, because the feeding tank is placed in high. The pressure is measured by a manometer.
• The filter cartridge is easily removable, so it allows to study the difference between different media, both in compositions and in mesh.
• This unit, in addition to students teaching and training, also can be used in routine control at water purification works, or at water treatment works which employ tertiary filtration.

SPECIFICATIONS

• Bench-top unit.
• Anodized aluminum frame and panels made of painted steel.
• Main metallic elements made of stainless steel.
• Diagram in the front panel with distribution of the elements similar to the real one.
• Feeding tank of 1 l capacity.
• Filtration unit, with porous bed filter, removable:

1. Height of the filter: 70 mm.
2. Test filter cell diameter: 44 mm.
3. The filter unit can be dismounted to change the sand.

• A regulation valve controls the flow, which is observed on a flow meter.
• Water flow meter, range: 0.07 - 0.55 l/min.
• Differential manometer of 500 mm, to measure the head loss.
• Corrosion-resistant materials are used.
• The elements and tubing connections of this unit are transparent so that the operation can be observed and air bubbles avoided.

Accessories included with the unit:

• Thermometer, with range from -10º C to 110º C.

 Stopwatch.

• 1 l graduated test tube.
• 0.6 l glass beaker to collect filtrate.
• Air pump for purging the manometer.

EXERCISES AND PRACTICAL POSSIBILITIES

1. Study of the filtration operation principles.
2. Study of Darcy equation.
3. Deep bed filtration of suspensions with different beds.
4. Calculation of Filterability Index.
5. Sand filter cleaning.