DEVELOPMENT OF DESIGN PROCEDURES FOR  NONMECHANICAL DEWATERING OF ALUM RESIDUALS   Non-mechanical dewatering systems, either dewatering lagoons or sand drying beds, are the most widely used method of alum residuals treatment. This is especially true for the small to medium size utility. However, very little data existed on how to properly test and size such a system to assure its successful application. EE&T developed such testing and design procedures and verified the results with full-scale data. In conjunction with that work, EE&T developed a design program to model the performance of dewatering lagoons and sand drying beds. A field pilot plant procedure was developed to determine key variables, including such items as residuals conditioning, suspended solids concentration, residuals loading height, loading rate and annual yield. Working in conjunction with three utilities practicing one or more of the non-mechanical methods the pilot procedures were compared to actual performance. The end product was the development of testing and design criteria to enable utilities to properly size non-mechanical systems.