Sludge conditioning apparatus

A sludge conditioning apparatus comprising at least one hopper (18, 19, 20, 21) for receiving waste water having solid impurities entrained therein, wherein the solid impurities settle out of suspension to be collected in a lower region of the hopper as sludge, the hopper having a sludge outlet (32) at a lower end thereof communicating with a pump (34,35,36,37) for removing sludge therefrom, sensing means (30) being provided for determining the amount of sludge collected in the hopper, the rate at which the sludge is removed by the pump being controlled by a control device, the control device controlling the operation of the pump to control the rate of removal of the sludge as a function of the output of the sensing means, said sensing means determining the weight of sludge collected in the hopper, wherein the hopper comprises an upper section (22) and a lower section (26) supported by the upper section (22), the sensing means comprising one or more load cells (30) acting between the upper and lower sections (22,26) of the hopper for determining the load applied to the upper section (22) by the lower section (26).