Consequently, a fairly good agreement exists between the results of recently published investigations on filamentous organisms in activated ... In this way the present report may contribute to finding the solution of the bulking sludge problem. ... Dr. Ir. E. G. Mulder (Director of the Laboratory of Microbiology at Wagcningenl for reading and commenting on the manuscript. ... Breed R. S.. Murray E. G. D. and Smith N. R. (1957) Ber- tjcya#39;s Manual of Deternmtive Bacteriology. 7th edition.