When people think of sand filtration, they automatically relate to municipal water treatment facilities. In general that's the arena that this classical filter has ruled, but it most certainly has found applications in pure industrial settings, oftentimes for niche applications where suspended solids and organic matter persist in process waters. Very common applications that I have seen in Eastern Europe have been part of cooling and process water treatment plants, particularly for large cooling tower applications in refineries and coke chemical plants, where biological growth problems can adversely impact on heat exchange equipment. Also, in many former Soviet block republics, municipal water treatment plants were almost always part of large industrial complexes, so that both the communities and plant water treatment requirements were met by a single operation. This leads to a very distinct set of problems that we in the U.S. and parts of Western Europe don't face, because of the separation of operations, and one which is way beyond the scope of this volume.
Sand filtration is almost never applied as the primary treatment method. Most often it is a pretreatment or final stage, but sometimes intermediate stage of water treatment, and is most often used along with other filtration technologies, carbon adsorption, sedimentation and clarification, disinfection, and biological methods. The term sand filtration is somewhat misleading and stems from older municipal wastewater treatment methods. While there is a class of filtration equipment that relies principally on sand as the filter media, it is more common to employ multiple media in filtration methods and equipment, with sand being the predominant media. In this regard, the terms sand filtration and granular media filtration are considered interchangeable in our discussions. The design, operation and maintenance of these systems are very straightforward, and indeed may be viewed as the least complex or simplest filtration practices that exist. It is a very old technology and much of the operational criteria is "art" in my opinion - although I have gotten into arguments with my colleagues on the use of this term. Be as it may - let's take a look at this technology and then try some Questions for Thinking and Discussing. Remember to refer to the Glossary at the end of the book if you run across any terms that are unfamiliar to you.
Was this article helpful?