Installations include a series of coarse filters for pre-treatment, made from gravel, crushed stones, even coconut fiber. The – often three – consecutive filter beds have decreasing particle sizes, typically from 20 to 4mm. Applied to pre-treat high turbidity waters for slow sand filtration.
Construction costs are low to medium. Operation becomes more expensive because of backwashing. Specific costs…
Used mostly in centralized treatment. Requires little maintenance or operation, except for the backwashing events. Since roughing filters are used in combination with other processes (e.g. slow sand filtration), personnel for these processes can do maintenance jointly.
Risk of contamination of the (partly) treated water, if the installation is open (not covered). A large volume of highly contaminated backwash water is produced at installation-cleaning. The concentrated solids require proper handling, storage and disposal.
Different methods exist e.g. downflow, upflow or horizontal flow. Upflow roughing filters are relatively cheap and easier to clean than downflow or horizontal flow filters. Maintenance primarily related to cleaning process. Manually (time-consuming and labor intensive): removing, washing, replacing filter media. Hydraulic backwashing preferred. Effluent monitoring required.
Roughing filters are usually centralized treatment installations requiring no specific involvement from users. Therefore, no special awareness-raising is required. Roughing filters offer no guarantee of safe water without complementary treatment e.g. slow sand filtration or other disinfection treatments.
No relevant remarks for Roughing filter.