Node diagram originally commonly used in building construction, mainly indicates the building construction details of the diagram, the node is the confluence of more than two decorative surface. Node diagram is generally used to show the specific structure of the object. Sewage node diagram is to quote the above method, will be an industry or enterprise of a certain type of product production process with the node diagram method to show out, and will be pollutants generated links labeled, so that the "three simultaneous" pollution prevention and control and enterprises, environmental protection department environmental management is more targeted and operable. Discharge node diagram is commonly used in construction projects, environmental impact assessment, industry pollution emission control or standardization.