| Accurately assessing and diagnosing the intrusion status of the sewer system(also known as inflow and infiltration,I/I)is an important pre-work to achieve the project goals of improving sewage treatment quality and efficiency and comprehensive water environment treatment.At present,a variety of extraneous water assessment methods based on monitoring pipe water quantity and water quality indicators have been developed,but the specific implementation often faces problems such as difficulty in water quantity monitoring and poor stability of water quality analysis,resulting in unreliable assessment results.In this paper,the following researches are carried out on the key influencing factors in the process of evaluating the extraneous water of the sewer system by the water quantity and water quality method:(1)In this study,a simulation test platform for the operation of the original size sewer pipeline was built,and the problems of the poor monitoring effect of the Doppler flowmeter under complex conditions and how to rationally use the relationship between the liquid level and the flow rate in the pipeline were carried out.In this study,the hydraulic test was carried out on the basis of the original size drainage pipeline operation simulation test platform built according to the actual form.By adjusting the inlet flow of the device and the installation height of the baffle,the conditions of free outflow,blockage and full water in the pipe are simulated.Based on the measured data and a series of evaluation indicators,the monitoring effect of the Doppler flowmeter and the liquid level-flow relationship in the pipe are evaluated.The results show that the flow velocity is the main factor affecting the monitoring effect of the flowmeter.Too high blockage and too low flow rate will reduce the accuracy and stability of flow monitoring.Under the condition of free flow,the quadratic function is the best model to describe the relationship between the flow level and the flow rate.Under different pipeline blockage conditions,the relationship between the flow level and flow rate in the pipe shows different trends due to the changes of the cross-sectional area and the average flow velocity;(2)Aiming at the reasonable selection of marker species in the process of evaluating the extraneous water in the sewer system based on the water quality method,the application trend of the current common marker species,as well as the applicability,advantages and limitations in practical engineering are summarized by reviewing the literature.And summed up the four main standards that need to be met for screening ideal marker species.The representative marker species of an actual drainage catchment were screened,and the conductivity can be used as an ideal water quality characteristic factor to characterize the local sanitary wastewater;(3)Aiming at the uncertainty factors of the three simple water quality indicators,namely conductivity,turbidity and temperature,an artificial inflow test was carried out based on the physical model of the original size.By setting the water quantity and water quality conditions of different sanitary wastewater and extraneous water,the APE of the quantitative extraneous water based on the measured data is: turbidity(0.06%～55.54%)>conductivity(3.50%～50.44%)> in-sewer temperature(2.81%～45.86%),the relative uncertainty is: turbidity(0.35～12.45)> in-sewer temperature(0.25～1.17)> conductivity(0.01～0.34),the overall quantitative effect of the conductivity indicator is better than turbidity and in-sewer temperature.By evaluating the effect and influencing factors of quantitative detection of extraneous water by three markers,it is found that the higher the proportion of extraneous water and the greater the difference in water quality between the extraneous water and the sanitary wastewater,the better the quantitative effect;the difference of water quality is the main factor affecting the quantitative effect... |
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