Controlling the supply of bodyfeed to a filter

The present invention relates to controlling the supply of bodyfeed to a filter for removing solids from a liquid stream and relates particularly but not exclusively to removing yeast and haze from a beer stream. The invention features a control system for controlling the supply of bodyfeed to a filter for removing solids from a beer stream is described. By applying the bodyfeed at an appropriate rate and hence achieving appropriate effective bed voidage it is possible to maintain beer clarity while minimizing filter aid usage. The control system includes a means for determining turbidity of the liquid stream upstream of the filter, a means for determining the rate of pressure drop change across the filter, and a controller for altering the supply of bodyfeed to the filter in accordance with a calculated dose change.