Abstract: The present invention is directed to a process of making fired mineral pellets by mixing particulate mineral material with moisture and binder comprising substantially water soluble organic polymer to form a moist pelletizable mix, pelletizing the moist mix by a tumbling process to form green pellets and firing the green pellets, characterized in that the binder comprises alkali metal silicate in a dry weight amount which is either (a) above 0.13% based on moist mix or (b) above 0.08% based on moist mix and at least three times the dry weight of substantially water soluble organic polymer.

Abstract: Primary polymer particles having a size at least 90% below 10 .mu.m and which contain water soluble and water insoluble polymer are made by reverse phase polymerisation of a water soluble ethylenically unsaturated monomer or monomer blend with cross linking agent, and the emulsion is then spray dried to form spray dried granules which disintegrate upon addition to water, thereby forming an aqueous composition of the insoluble particles having activity similar to the starting emulsion. This aqueous composition of insoluble particles is particularly useful for flocculation, for instance flocculation of sewage sludge followed by centrifugation or belt pressing, or for viscosification.

Abstract: A suspension is dosed with a coagulant and then with a flocculant and is dewatered to form a thickened sludge or cake and separated liquor, and control of the dewatering performance is improved by adding the flocculant at a predetermined dosage, monitoring the charge in the separated liquor (or monitoring other dewatering parameter of the separated liquor or suspension) and adding coagulant at a dosage selected in response to the monitored charge or other parameter value in order to maintain the value substantially at a preselected optimum value.

Abstract: The addition of polymeric flocculant or other chemical dewatering modifier to a suspension flowing through a service line to a dewatering plant is controlled automatically in response to automatic determination of a filtration rate parameter. This may be determined using novel apparatus which includes a filtration assembly comprising a chamber with a filter element mounted across its open end and water sprays for washing the filter element. In one embodiment it is preferred to assist back-washing with an air purge while in another embodiment there are means for disassembling the filtration assembly to permit cleaning.

Abstract: Phosphate is removed from an aqueous medium by adding inorganic coagulant followed by a cationic polyelectrolyte which is a water-soluble quaternary ammonium salt of a high molecular weight copolymer of acrylamide and an alkylaminoalkyl ester of acrylic or methacrylic acid. The process is of particular value in reducing the phosphate content of sewage effluent.