Abstract: The invention relates to a mixing apparatus for maintaining a pressure differential over varying feed rates by mixing a flow of sludge with a flocculant. The mixing apparatus includes a monitor for monitoring the pressure differential across the apparatus and a device for varying the size of an orifice in the apparatus through the sludge flows. The orifice size is dependent on the monitored pressure differential to maintain a desired differential pressure over a range of sludge feed rates.

Abstract: This invention relates to a belt press for dewatering sludge, such as sewage sludge. The press includes a camera to monitor physical operation of a gravity belt section of the press. A numerical control device uses electromagnetic radiation received from the gravity belt section to control the physical operation of the gravity belt section. An actuator device may be used to control a height of a weir for distribution of the sludge over the gravity belt section, and another actuator device may be used to control positions of ploughs which plough the sludge.