Abstract

Nowadays, occurrence of abnormal mineral or organic natural (geogenic) compounds concentrations, in ground and infiltration water, but also quite often in surface waters, is now a common problem encountered in Poland, Europe and many other countries throughout the world. The most concern is usually paid on the removal of iron (Fe) and manganese (Mn) as well as anthropogenic compounds (in particular referring to the organic compounds such as nitrogen) associated with human activity. From the 19th century, the main filter media used in rapid gravity filtration have been silica sand and anthracite coal. Sand still remains the preferred filter medium in the lower layer with typically anthracite coal used in the upper layer. This dominance is due to its low cost, availability and extensive experience in water treatment applications, which has led to dependable and predictable performance. Over recent years multi-media filters have become the typical filter arrangement. Furthermore, granular filters can be made of a variety of natural materials. Depending on the origin of these materials they can have very different shapes, sizes and compositions. Granular filter media must satisfy various specifications before they can be considered for applications. These include grain size, grain surface condition, density, particle porosity, solubility, durability, settling rate (Mörgeli and Ives, 1979; Trussell et al., 1980). The aim of this study was to assess and compare the efficiency of the alternative Filtralite MonoMulti with a conventional dual-media filter beds consisting of anthracite coal on top of a silica sand layer. Media with the trade name “Filtralite” are processed (expanded) clay products with high porosity and quite rough grain surfaces. To perform a reliable comparison of the two different media filters, two pilot filter columns operated in parallel with the similar feed water and under iqual conditions were used. The pilot plant, constructed and installed in a „Gdańsk – Lipce” Water Treatment Plant (WTP) in northern Poland, provided the experimental database for comparative study of water quality parameters using conventional vs. alternative granular materials to improve the groundwater treatment process by dual-media filtration.

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