Research On Calculation Of Exterior Water Intrusion Ratio Of Urban Sewage Pipeline Based On Sulfur Stable Isotope

The problem of external water intrusion of sewage pipe network not only increases the operation load of sewage treatment plant and its operation and maintenance cost,but also leads to the bad consequences of high water level operation of sewage pipe and even sewage overflow.Therefore,it is of great significance to study the accurate qualitative and quantitative technology of external water intrusion of sewage pipe network.At present,the measurement technology of external water intrusion mainly involves equipment detection,model calculation and water quality and quantity balance calculation.As one of the measurement methods of water quality and quantity balance,the stable isotope method has a better ability to quantitatively measure the degree of external water intrusion under certain conditions.Among them,the stable sulfur isotope has great research potential and value because of its wide difference and superior stability.In this paper,the relative abundance of stable sulfur isotope(δ³⁴S)in the local independent drainage area of a university was studied for the first time under different domestic water consumption behaviors and in the terminal sewage of drainage area,and the synchronous comparison with ammonia nitrogen and sulfate ions was made.The factors influencing the calculation result of external water invasion ratio of sewage pipeline based on stable sulfur isotope were studied,and the invasion difference(the difference between external water and upstream sewageδ³⁴S before the invasion,The experiment in this paper involves the influence of 1.56‰,7.15‰and 17.00‰)and invasion ratio（5%,10%,20%and 30%）on measured external water ratio in deviation state and uncertainty level.The main conclusions are as follows:（1）Compared with ammonia nitrogen and sulfate,δ³⁴S is less affected by different domestic water behaviors;compared withδ³⁴S in tap water,kitchen behavior has the greatest influence on it,with an average variation range of 64.69%,while washing behavior,shower behavior,lavatory behavior and tableware cleaning behavior have relatively little influence,with an average variation range from-14.37%to 5.62%.In general,domestic water consumption behavior has a relatively small impact on the change ofδ³⁴S,andδ³⁴S has the potential to be a characteristic factor for calculating the proportion of water intrusion from sewage pipe network.（2）Compared with ammonia nitrogen and sulfate radical,δ³⁴S in the end sewage of the drainage area has a smaller hourly variation range and a stable trend,with a strong recurrence of daily fluctuation.compared withδ³⁴S in tap water,the average daily change was 25.99%.Under the influence of kitchen behaviors,the increase range in daytime is relatively large,and at night,it returns to the level close toδ³⁴S in tap water and tends to be stable,indicating thatδ³⁴S is suitable as a characteristic factor for quantitative calculation of the proportion of external water intrusion in sewage pipe network.（3）δ³⁴S is capable of quantitative measurement of the proportion of water intrusion from sewage pipes under certain conditions.Among them,based on the invasion difference of 7.15‰and 17.00‰andδ³⁴S in upstream sewage,the estimated results are close to-30%and-15%deviation level under the invasion proportion of 20%and30%.Based on the intrusion difference of 17.00‰andδ³⁴S in tap water,the calculated results are less than 10%deviation under the intrusion proportion of 20%and 30%.