This volume contains the proceedings of a post -conference seminar held in Pretoria during April 1982, in conjunction with the 11th IAWPRC Biennial International Conference in Cape Town. The papers concern the removal of phosphate from wastewater. In the introductory section, three review papers describe the background, summarize the early work, and list the advantages of various proposed phosphorus removal mechanisms, which are described in the subsequent papers in detail. The individual contributions concern biochemical changes, the role of micro-organisms, a parametric model, and the PhoStrip process. Other papers interpret pilot and full scale experiments, design criteria, and optimal operation. The seminar provided a general overview of the present methods of phosphate removal. As J. L. BARNARD remarked in his introductory section: "it is interesting to note that the pure micro-biologists were more interested in the phenomenon of phosphate accumulation in the cells and less in the triggering of the rnerhanism in cells that would otherwise not accumulate excessive quantities". I n some plants in the U.S., the removal of phosphorus could be attributed t o one bacterial genus, Bci?aobacter, but as K. E. V. BRODISCH & S. J. JOYNER showed a t the seminar, in activated sludge processes, other micro-organisms can be identified.