This is the second article in a three part series on the use of carbon block in water filters.
There are many different types of carbon blocks that can be engineered for specific applications in water filters. The two main methods of block manufacturing are extrusion and moulding. Both methods are equally effective in producing good quality carbon block, and both methods are capable of producing blocks with similar performance.
Carbon blocks are rated for sediment removal by the efficiency by which they remove particles. Typical ratings are 0.5 micron, 5.0 micron and 10 micron, whereby at least 85 percent of the particles are removed at the rated size. A block that removes cysts must remove 99.95 percent of particles of 3-micron size. Carbon blocks that filter smaller sized particles typically are more dense and, therefore, have a higher pressure drop at a given flow rate. Formulations can be adjusted to accommodate a wide variety of sediment filter removal rates and efficiencies.
Carbon block can also be tailor engineered for a range of chemical removal efficiencies by varying carbon source, mesh range and additives. For example, carbon can be derived from coal, coconut shell or wood. Each carbon type and activation level can produce widely varying performances for a given chemical compound. Performance depends on the carbon type, kinetics, flow rate through the block and the amount of carbon in the block. In addition, additives such as alumina-type compounds enhance heavy-metal removal. Again, formulations for water filters can be altered to select the level of chemical removal desired.