headloss

Well-operated slow sand filters use natural treatment processes, and nature will rebel with a headloss increase when filters are overloaded, in contrast to chemical and mechanised treatment processes, where chemical doses and water pressure can often be increased at the cost of the water quality produced.

8. Classification of roughing filters 1996

The caretaker may thus greatly influence and control the quality of the treated water by adequate slow sand filter operation and by monitoring the headloss development.

8. Classification of roughing filters 1996

However, besides efficiency in suspended solids separation, other criteria such as terminal headloss, filter running time and filter cleaning aspects have to be taken into consideration.

8. Classification of roughing filters 1996

An inlet weir can control the headloss and the water level increase in the inlet box located after the weir also indicates filter resistance development.

8. Classification of roughing filters 1996

Especially the gravel size of the top filter layer is smaller; i.e., less than 6 millimetres in diameter, while filtration rate is usually more than 5 m/h, Maximum available headloss is still limited and ranges between 20 and 40 cm in spite of finer filter material and greater filter velocity.

8. Classification of roughing filters 1996

Final headloss in a roughing filter is usually small; i.e., 10 to 20 cm, or 30 cm at the most.

8. Classification of roughing filters 1996

Since the headloss in intake filters can increase to 20 - 30 cm within a week [48], the flow through the filter has to be adjusted by gradual opening of the valve located in the effluent pipe.

8. Classification of roughing filters 1996

The headloss increases to a few centimetres in well-operated roughing filters.

8. Classification of roughing filters 1996

To maintain adequate filter performance and limit filter headloss, periodic removal of the accumulated solids from the filter media is essential.

8. Classification of roughing filters 1996

General aspects of roughing filter design9. 1 Main features9. 2 Basic filtration theory9. 3 Design variables and guidelines9. 4 Flow and headloss control9. 5 Filter drainage system9. 6 General design aspects10.

8. Classification of roughing filters 1996