Gravel has been traditionally used in horizontal roughing filters. Meanwhile, activated charcoal also proves to be an effective filter media due to numerous adsorption sites in addition to its ability to serve as a filter. Does replacing gravel in horizontal roughing filter with activated charcoal significantly improve turbidity removal efficiency? If so, to what extent?
Dear Isaac,
I recommend the following interesting article that answers your question.
http://sajs.co.za/sites/default/files/publications/pdf/sajsci_v106_n10_11_a3.pdf
With my best regards
Prof. Bachir ACHOUR
I am not an engineer or water treatment expert, but have some knowledge on the subject that may help. Sand filters are sometimes used to help reduce turbidity, as they can slow water transfer rate and capture fine sediments, probably increasing efficiency with time, but also slowing rate as they may become clogged. However, gravel filters of gravel size particles may be inefficient at removing turbidity, especially at first until they start capturing more sands and perhaps silts. Turbidity causes by high dispersion clays such as montmorillonite are difficult to settle and remove, perhaps even taking months of settling unless flocculation or other methods are used. Activited charcoal can add filtering capacity and ability to absorb contaminates, but its raw filtering potential of turbidity and ability to move water through would be dependent on the size of the charcoal particles, and the types of turbidity involved. Turbidity can be part mineral (sands, silts, clays) and part organic (pieces of leaves, algae, etc.) based. There may also be various methods such as settling ponds and filter cloths that can capture some of the sediment loading before filtering, or aid in retaining water for chemical treatments. Depending on the specific circumstances and needs for low turbidity waters, finding alternative sources or drilling well to suitable aquifer with natural filtration can be advantageous.
my limited knowledge is that charcoal is more used to improve water taste and odor more than turbidity.
Dear Dr. Isaac Monney, Agreeing with Dr. WH Hansen, Sand filters definitely reduce turbidity, and slower the rate more capture of fine sediments is possible. At times Charcoal filters disintegrate but stay together and assist in gathering loose sediments. They also in their passage remove odour and some strong acidity is neutralised. Fine, and medium gravel is always used to keep the other layers/ loose matter intact without getting dislodged in the flow stream. Therefore, a combination of sand and charcoal followed by coarse and fine gravel in adequate proportion would be ideal. w wshs,,
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