The potable water for the Egyptian Water-Supply Authority isobtained mainly from many treatment plants in which surface water(River Nile and its Canals) is treated by a system of coagulation,sedimentation filtration and chlorination stations. This thesis describesthe design of treatment units which are an automatic control systemfor any of the surface water treatment plants by using the computerprogram named SWTPl. This program can save a lot of time in thedesign of the surface water treatment plant whether small or large.SWTPl can grve the operation relationships between the succes-sive units in the plant. Also SWTPl gives the economic design bychoosing suitable practical and economic design criteria.This program IS flexible and gives the design for thealternative solutions for the surface water treatment plants.