Abstract : This paper introduces a distributed control system (DCS) for the Lanzhou Railway Water Plant, consisting of a host computer, programmable logic controller (PLC), frequency converter, and corresponding sensors and actuators. After careful demonstration and testing, the system proves reliable and comprehensive, providing a cost-effective and efficient solution for the technological upgrading of similar small and medium-sized water plants. Keywords : Host computer; Programmable logic controller (PLC); Frequency converter; Rotary clarifier; Pipeline pressure; Pump switching; Water level; Autotransformer pressure reduction start-up; Overflow. The Lanzhou Railway Water Plant is responsible for supplying tap water to the Lanzhou Railway area. Due to low automation levels, operating costs are high, and workers face significant labor intensity. Currently, the Lanzhou Railway Water Plant employs a two-stage pumping station management model: a primary pumping station using submersible pumps draws water from the Yellow River to the rotary clarifier of the No. 1 water supply plant for treatment; then, a secondary booster pumping station supplies water to the user network. Control is generally achieved through manual relay control. This results in low automation levels, significant waste of water and electricity resources, numerous equipment malfunctions, and management difficulties. To address this issue, a distributed control system for the water plant was designed and developed, consisting of a host computer, a programmable logic controller (PLC), a frequency converter, corresponding sensors, and actuators. After partial module application and testing, the system demonstrated stable and reliable performance, providing a technical upgrade solution for small and medium-sized water plants, primarily aimed at energy conservation, emission reduction, and improved automation. 1. Main Functions of the System The basic situation of the Lanzhou Railway Water Plant is as follows: The primary pumping station includes the Yellow River trough intake and three intake wells, each equipped with a 175kW submersible pump. The secondary pumping station includes two 500kW centrifugal double-suction pumps (14SH-6B) and two 120kW multistage centrifugal pumps (200D1-43×3). Based on dispatch orders and user water usage periods, the system rationally activates each pump or uses frequency converters to supply water according to the pipeline pressure. The primary pumping station has a water storage capacity of 540 m³/h for influent and 425 m³/h for effluent. Forced effluent of 45 × 2 m³/h is supplied through three cyclone clarifiers with a total retention time of 2 hours. After primary chemical dosing and sedimentation, water is supplied to the pipeline network by gravity. The water then reaches the secondary pumping station's flotation workshop (four filters with an effluent capacity of 375 m³/h), ozone workshop, carbonization workshop, and chlorination disinfection processes before entering five clear water tanks with a total storage capacity of 5000 m³. Finally, it is pressurized by two pumps and supplied to households. The design requirements for the control system are: automated control and management of the water plant's equipment operation and production status. [b][align=center]For more details, please click: A Brief Discussion on the Automation Technology Transformation of Lanzhou Railway Water Plant[/align][/b]