Study on External Water Quantity Calculation of Drainage Systems Based on Conductivity Measurement

The external water of drainage systems will cause a lot trouble to the operation of sewer pipe systems and waste water treatment plants. It can reduce the efficiency of sewerage treatment and increase the investment of pump stations and the cost of operations. The external water mainly includes underground water infiltration and rainwater inflow. Based on the theoretical analysis and experimental verification, this article put forward a new methodology of calculating the external water quantity according to the different conductivity of sewage and external water. The flow in sewer pipes was precisely calculated according to the relationship among the water levels of manholes, pipe diameters and pipe materials. The article proposed an evaluation technology of sewer pipe operation by analyzing the relationship of sea tide levels, underground water levels and infiltrations. In this paper, the sub-catchment zoning, monitoring equipment arrangement, and data acquisition technology were offered. Also, the tide influence on drainage systems of coastal cities was studied quantitatively based on the analysis of sewage collection ratio, external water amount and pump station operation results. The study results showed that this method is suitable for external water diagnosis and the evaluation of sewer drainage systems.