A Study On Urban Rainwater Runoff Pollution Control And Quantitative Sewer Pipe Defect Assessment

The rainwater surface runoff pollution and the underground sewer exfiltrationcaused by pipe defects are the two main sources of the urban non-point source pollution.How to effectively control the pollution from rainwater runoff and to assess andrehabilitate the sewer, becomes the key of controlling the urban non-point sourcepollution. In this study, several high adsorption capacity media were produced to adsorbphosphorus in rainwater runoff; novel rainwater collection and treatment processes weredeveloped to reduce the rainwater runoff pollution; a comprehensive sewer defectcondition evaluation model was established based on sewer pipe video inspection andfuzzy mathematic methods, and partial sewers in two southern Chinese cities werequantitatively assessed by the aforesaid model. The following conclusions came outwith this study:1. Nano iron particle was prepared using ferric ion reduction by NaBH4to modify phosphorus adsorption materials. The adsorption capacity of the modifiedmedia was increased at most up to75folds when treating phosphorous in rainwaterrunoff and the total phosphorus in the effluent was below0.02mg/L;2. A novel processcombining sedimentation and infiltration was designed and carried out to treat rainwaterrunoff from street in a southern Chinese city, City A. The system reached averageremoval efficiencies of98.6%,65.4%,55.1%and92.6%for SS, COD, TN and TP,respectively. An infiltration process was also built for the grassland rainwater runofftreatment, and it achieved high removal efficiencies under different hydraulic loadingrates. The removal efficiencies for SS and TP were around60%after a long periodoperation;3. An independently designed sewer inspection robot THUSIR-2was alsostudied and manufactured, and put into use for partial sewer video data collection inCity A.4. A comprehensive sewer defects evaluation model based on FuzzyComprehensive Evaluation (FCE) and Analytical Hierarchy Process (AHP) concerningthe function, structure and stability of the sewer was developed, which concerned all thedefects with different damage levels in one pipe during the evaluation and provided aquantitative index H to represent the defects conditions of the pipe;5. Partial sewervideo data from two southern Chinese cities, City A and City B, were analyzed by theaforesaid evaluation model, and results showed that, around30%of the pipes examined in City A were categorized in severe or urgent level, and the main occurring defecttypes were deformation and clogging, while20%were in moderate level with maindefects like clogging, and the rest were in slight-defecting or good condition. About15%of the examined pipes in City B were in severe level and another15%were in moderatelevel, both with main defects like clogging and joint damage, and the rest were in goodcondition.