Filtration

1. Description: Filtration, as a unit operation for wastewater treatment processes is a relatively recent practice. Currently filtration is used, in a general sense, to get a greater removal of suspended solids coming from the effluents of biological and chemical treatment processes; it is also used for the removal of chemically precipitated phosphorus and as a precursor to the electro dialysis process. Filtration can be done as a single-stage separation of solids in suspension or as a previous treatment of coagulation or flocculation, which allows the separation of smaller solids and colloidal matter. The basic objective of filtration, therefore, is to separate particles and objectionable microorganisms, which have not been retained in coagulation and sedimentation processes. As a result, the work that the filters do, depends directly on the greater or lesser effectiveness of the preparatory processes.

2. Ranges of design: Lapsolite offers filters with a low surface charge (slow filters) or a high surface charge (fast filters) in porous material (clay pastes, filter paper) or in granular matter (sand, anthracite, garnet or combined), with upward, downward or mixed flow (part ascending and part descending). On the other hand, the filter can work under pressure or by gravity, depending on the magnitude of the hydraulic load that exists over the filter bed.

Important factors to consider in the design:

     a. Operation type.

     b. Types of filter media and sense of flow during the filtration phase.

     c. Acting pressure filtration.

     d. Methods of flow control.

     e. Speed of filtration.

3. Applications: Industrial plants (metallurgical, chemical, petrochemical, pharmaceutical, etc.).

4. Benefits:

     a. Low cost of operation and maintenance.