Ceramic microfiltration with a sub-micron powdered activated carbon pre-coat for water treatment

摘要

In this study the removal of dissolved organic matter (DOC) from soil aquifer treatment water, and atrazine and MS2 phages from Delft canal water by a pilot plant combining ceramic microfiltration with a pre-coat of powdered activated carbon (PAC) is investigated. Two types of PAC are used; normal sized PAC (NPAC, average size 25 μm) and a ground form of the same PAC, sub-micron PAC (SPAC, average size 0.8 μm). The DOC removal with pre-filtered (0.45 μm) for a fixed SPAC pre-coat dose is optimal when the flux during pre-coating is □200 1 m~(-2) h~(-1), probably due to better packing of the PAC. The average DOC removal in a 1 hour filtration cycle increases with increasing SPAC pre-coat dose (14-56 mg/l) and varies from 51 to 70%. Pilot experiments with raw Delft canal water and atrazine show that SPAC is better than NPAC in removing atrazine. Atrazine removal with the pilot plant is better for a SPAC pre-coat than for a NPAC pre-coat; average removal for a 2 hour filtration cycle is 87% for 20 mg/l SPAC and only 41% for 20 mg/l NPAC. As the contact time of the water and PAC is very short (in the order of 0.4 s), the adsorption of atrazine to the smaller sized SPAC is very fast. Increasing the SPAC concentration to 40 mg/l only slightly increases atrazine removal (to 93%). Removal of MS2 phages is 0.3-1.5 log units and depends mainly on the trans membrane pressure increase, and not on the pre-coat type indicating that removal takes places by size exclusion rather than adsorption.