CN114624407B - Method for measuring and calculating external water quantity of district sewage system based on typical land parcels - Google Patents

Abstract

The present invention discloses a method for calculating the amount of external water in a district sewage system based on a typical plot, comprising the following steps: (1) deploying monitoring points and obtaining flow and water quality data of the monitoring points; the monitoring points include primary monitoring points and secondary monitoring points; (2) selecting typical plots and calculating the background value of sewage water quality concentration in the district; (3) calculating the baseline value of external water quality concentration; (4) calculating the amount of external water. The present invention can quickly and accurately calculate the amount of internal and external water in a sewage system with less investment and cost.

Description

A method for calculating the amount of external water in a regional sewage system based on typical plots

Technical Field

The patent of this invention relates to the diagnosis technology of the operation status of sewage pipes in sewage systems, and specifically to a method for calculating the amount of external water in a district sewage system based on typical plots.

Background technique

In recent years, with the rapid increase in my country's urbanization, urban sewage treatment facilities have basically achieved full coverage, and the urban sewage treatment rate has also increased significantly. The urban sewage treatment system is a key infrastructure to ensure the sustainable development of cities. However, the urban sewage system has problems such as inadequate construction and maintenance of sewage pipe networks, insufficient sewage collection rates, and external water intrusion, which have caused the influent concentration of urban sewage treatment plants to be significantly lower than the design value, seriously affecting the normal operation and efficiency of the sewage treatment system, and bringing adverse effects to the sustainable development of cities and the construction of ecological civilization.

External water refers to groundwater, river water, spring water, and other leaking pipe water that enters the sewage system through damaged sewage pipes, pipe joints, and inspection wells; external water may also flow in through other adjacent rainwater pipes, construction site drainage, streams, and other waterways. The problem of external water worsens with the aging of the sewage system. Specific influencing factors include: the service life of the pipeline system, pipe quality, construction methods, construction quality, changes in groundwater levels, etc. The entry of external water into the sewage system not only affects the water quality concentration of the sewage treatment plant and the sewage treatment efficiency of the sewage treatment plant, but also increases the risk of pipe network operation and overflow risks on rainy days, which has a negative impact on the treatment of black and odorous water bodies and the improvement of the quality and efficiency of the sewage system. Therefore, it is crucial to do a good job in pipeline cleaning and sewage diversion and comprehensive evaluation of the operation status of the sewage system.

The flow meter monitoring method is one of the earliest monitoring methods used for river water (groundwater) infiltration into sewage mains, and it is also one of the simplest methods. This method of simultaneously monitoring the upstream water volume, water quality and downstream water volume and water quality can only be used for the main pipe part, and it is difficult to comprehensively estimate the water volume inside and outside the area, and there are certain defects in the exploration and summary of sewage system problems. Therefore, the patent of this invention aims to design a method for calculating the amount of external water in the area sewage system based on typical plots. Through the selection of typical plots and the detection of water quality, it is possible to better understand the sewage quality data of each plot in the monitoring area, estimate the amount of water inside and outside the area, and comprehensively judge the impact of external water and source water quality on the water quality of the area sewage system.

Summary of the invention

In response to the problems in the prior art, the present invention provides a method for calculating the amount of external water in a district sewage system based on a typical plot. The method can quickly and accurately calculate the amount of water inside and outside the sewage system, is widely applicable in my country's large-scale urban drainage systems, and provides a certain basis for the investigation of internal and external water in the district and the transformation of the sewage system, with less investment and cost.

To achieve the above object, the present invention provides a method for calculating the amount of external water in a district sewage system based on a typical plot, comprising the following steps:

(1) Deploy monitoring points and obtain flow and water quality data at the monitoring points: select a monitoring area within the area of the sewage system, select a number of monitoring points within the monitoring area; perform flow monitoring and water quality testing on each monitoring point to obtain the flow rate and water quality of the monitoring point;

The monitoring points include primary monitoring points and secondary monitoring points; the method for setting the primary monitoring points and secondary monitoring points is: according to the topological relationship of the sewage pipe network, the sewage collection point at the downstream end of the sewage trunk pipe is used as the primary monitoring point, the sewage flow threshold of the monitoring point is set, and the sewage branch pipe with a water volume exceeding the sewage flow threshold is selected as the secondary monitoring point;

(2) Screening typical plots and calculating the background value of sewage water quality concentration in the area: Divide the area into several plots, obtain the water supply of each plot, and classify the plots according to land use type. Select typical plots from the plots of each land use type based on the water supply; calculate the proportion of water supply of each land use type through the water supply of each typical plot, and conduct flow monitoring and water quality testing on the sewage discharged from the typical plots to calculate the background value of sewage water quality of each land use type; combine the background value of sewage water quality of each land use type and the proportion of water supply of each land use type to deduce the background value of sewage water quality concentration in the area;

(3) Calculate the baseline value of external water quality concentration: Conduct water quality tests on external water from different sources in the monitoring area to obtain the external water quality, and calculate the baseline value of external water quality concentration based on the external water quality.

(4) Calculate the amount of external water: Calculate the amount of internal and external water in the sewage system using the background value of sewage quality concentration in the area, the flow rate and water quality of the monitoring points, and the baseline value of external water quality concentration according to the water quality characteristic factor method.

Particularly, the water quality detection method is to measure the ammonia nitrogen water quality concentration.

Particularly, the water volume monitoring method is to monitor the water volume by using a Doppler flowmeter.

Particularly, the external water includes river water, groundwater, tap water and construction water.

In particular, the land use types include residential life, administrative institutions, and industrial enterprises.

In particular, in the step (1), the method for conducting flow monitoring and water quality testing on the first-level monitoring point is to conduct flow monitoring and water quality testing once during the peak period of water use in dry weather and once during the low-peak period of water use in dry weather; in the step (2), the method for conducting flow monitoring and water quality testing on the typical plot is to conduct flow monitoring and water quality testing once during the peak period of water use and once during the low-peak period of water use.

In particular, the specific method for selecting typical plots in step (2) is as follows: summarize and count the water supply data in the area provided by the water company, calculate the water supply proportion of each land use type plot respectively, and sort the water supply of each plot according to the land use type, and select several plots with large water consumption and uniform spatial distribution of the selected plots as typical plots under this land use type.

In particular, in step (2), the calculation formula for the background value of sewage quality for each land use type corresponding to each land use type is as follows:

C _j =(C _j1 *Q _j1 +C _j2 *Q _j2 + ... C _jn *Q _jn )/(Q _j1 +Q _j2 + ... Q _jn ),

In the formula, _Cj represents the background value of sewage water quality of each land use type of this land use type, _Cjn represents the ammonia nitrogen concentration of the land plot of this land use type; _Qjn represents the sewage water volume of the land plot of this land use type.

In particular, the method for calculating the reference value of external water quality concentration in step (3) is to conduct water quality testing on external water to obtain the actual measured ammonia nitrogen concentration of the external water quality and calculate the arithmetic mean to obtain the reference value of external water quality concentration.

In particular, in step (4), the specific method for calculating the amount of water inside and outside the sewage system is:

The amount of external water at a monitoring point is calculated using the following formula:

_Qw = ( _Cs - _Cd ) * _Qs / ( _Cd - _Cw ),

In the formula, _Qw represents the amount of external water; _Cs represents the ammonia nitrogen concentration at a certain monitoring point; _Qs represents the average water volume at a certain monitoring point; _Cd represents the background value of sewage water quality concentration; _Cw represents the reference value of external water quality concentration;

The amount of external water at all monitoring points is calculated using the above method.

After calculating the amount of external water, the main problems affecting the water quality in the area's sewage system can also be comprehensively evaluated through the amount of external water. Comprehensive evaluation of the sewage system refers to analyzing the main problems in the area, using the water quality and water volume data in typical plots and external water volume measurement to comprehensively judge the main factors affecting the water quality in the area, and provide data support for the investigation of water inside and outside the area. After calculation, if it is found that there is a large amount of external water in the main pipe, CCTV, QV periscope and other technologies can be used to detect this section of the sewage pipe, and finally the location of the sewage pipe damage can be found. For areas with low water quality, traceability is used to investigate the reasons for the low concentration of the plot.

The present invention has the following advantages:

(1) The present invention only requires the sewage trunk pipe and the selected sewage branch pipe in the area to be used as the primary monitoring point and the secondary monitoring point respectively to perform flow monitoring and water quality testing. It is not necessary to monitor along the entire process and each branch pipe, thus saving the cost of monitoring required for the installation of a large number of flow meters.

(2) The present invention uses typical plots to calculate the background value of sewage water quality for each land use type, avoiding the water quality and water quantity inspection of all plots in the area. At the same time, the sewage water quality of the plots in the area can be comprehensively reflected based on the selected typical plots. This method can not only systematically identify the water quality problems of plots under each land use type, but also comprehensively evaluate the water quality of the source in the area. The calculated background value of sewage water quality concentration in the area is both reasonable and relatively accurate.

(3) The present invention can measure the amount of inflowing water inside and outside the area, analyze the external water problem existing upstream of the branch pipe, identify the amount of external water infiltration in the area and on the branch pipe, improve the efficiency of diagnosing the operating status of the sewage system, and provide a reference for subsequent external water investigation, pipeline repair and other work. Finally, the water quality and water quantity data of typical plots and the external water quantity measurement can be used to comprehensively judge the main factors affecting the water quality in the area.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the principle of the method of the present invention;

FIG. 2 is a schematic diagram showing the distribution of primary monitoring points and secondary monitoring points in the monitoring area of the embodiment of the invention.

Detailed ways

The features of the present invention are further described below by implementing examples. The implementation methods are only used to explain the present invention and are not used to limit the scope of the present invention.

Taking a sewage system area in a southwestern city as an example, the treatment process of the implementation method of the present invention is explained.

When the sewage system is operating normally, the sewage in the sewage pipe belongs to the domestic sewage (including industrial sewage) discharged by various types of land use, and the "external water" entering the sewage system will not only affect the water quality in the sewage pipe, but also increase the treatment costs of sewage treatment plants and the risk of rainfall overflow, which will bring difficulties and challenges to the treatment of black and odorous water bodies and the improvement of the quality and efficiency of the sewage system. The water quality of "external water" is lower than that of the original sewage, and the ammonia nitrogen concentration is generally between 0.1-3mg/L. Therefore, by determining the water quality background value of the sewage system in the area and the water quality benchmark value of the external water, the amount of internal and external water in the area can be calculated, and a comprehensive evaluation and data support can be provided for the operation of the sewage system in the area.

As shown in FIG1 , a method for calculating the amount of external water in a district sewage system based on a typical plot according to an embodiment of the present invention includes the following steps:

(1) The monitoring area is selected according to the work purpose, the distribution of the sewage system network, the sewage flow direction and other factors. Taking Figure 2 as an example, according to the topological relationship of the sewage network, the sewage collection point at the downstream end of the sewage trunk pipe, that is, the sewage trunk pipe in the monitoring area (collecting all sewage in the area) is used as the primary monitoring point SJD1. Secondary monitoring points (CJD1, CJD2, and CJD3) are arranged in other large water volume branches in the monitoring area. Flow meter flow monitoring and water quality testing are carried out at each monitoring point; the ammonia nitrogen water quality concentration of SJD1 is C0, and the ammonia nitrogen water quality concentrations of the other secondary monitoring points are C1, C2, and C3; the method for flow monitoring and water quality testing at the primary monitoring point is to conduct flow monitoring and water quality testing once during the peak period of dry water use and the low peak period of dry water use, and the frequency can also be increased according to actual needs;

(2) Obtain water supply data for each plot in the area, classify each plot into residential areas, administrative institutions, and industrial enterprises, and select typical plots. The specific method for selecting typical plots is as follows: summarize and count the water supply data for the area provided by the water company, where the water supply refers to the tap water supply. Calculate the water supply proportion of each land use type plot, and sort the water supply of each plot by land use type. Select several plots with large water consumption and uniform spatial distribution of the selected plots as typical plots of this land use type.

Carry out water quality testing and flow monitoring on typical plots. The method for carrying out flow monitoring and water quality testing on typical plots is to carry out flow monitoring and water quality testing once during the peak water usage period and once during the low water usage period.

As shown in Table 1, _Cj is the background value of residential sewage quality, _Cx is the background value of administrative sewage quality, and _Cg is the background value of industrial sewage quality.

Taking residents’ life as an example, the calculation formula for the background value of domestic sewage water quality corresponding to residents’ life is as follows:

C _j =(C _j1 *Q _j1 +C _j2 *Q _j2 + ... C _jn *Q _jn )/(Q _j1 +Q _j2 + ... Q _jn ),

In the formula, _Cj represents the background value of domestic sewage, _Cjn represents the ammonia nitrogen concentration of residential land, and _Qjn represents the amount of sewage in residential land. Based on the above method, the background value of administrative sewage water quality _Cx and the background value of industrial sewage water quality _Cg are calculated.

As shown in Table 2, the background value of sewage water quality concentration C _d in the area is calculated by combining the background value of sewage water quality of each land use type and the proportion of water supply of each land use type.

Table 1 Calculation table of water quality background value for each land use type

Table 2 Calculation table of sewage background value in the area

(3) As shown in Table 3, water quality tests were conducted on external water in the monitoring area, including river water, groundwater, tap water, and construction water, to obtain the actual ammonia nitrogen concentration of each external water quality and calculate the arithmetic mean to obtain the external water quality concentration reference value _Cw .

Table 3 Calculation table of external water reference values in the area

(4) As shown in Table 4, the sewage background value _Cd of the plots in the area and the water quality _Cs and water volume _Qs of each monitoring point are used to calculate the water volume _Qw of the sewage system according to the water quality characteristic factor method. The specific calculation method of the water volume of the sewage system is:

The amount of external water at a monitoring point is calculated using the following formula:

_Qw = ( _Cs - _Cd ) * _Qs / ( _Cd - _Cw ),

In the formula, _Qw represents the amount of external water; _Cs represents the ammonia nitrogen concentration at a certain monitoring point; _Qs represents the average water volume at a certain monitoring point; _Cd represents the background value of sewage water quality concentration; _Cw represents the reference value of external water quality concentration;

The amount of external water at all monitoring points is calculated using the above method.

Table 4 Calculation table of external water reference values in the area

According to the above method, the amount of external water in the sewage system in the area is calculated to be 2917.9 tons/day. CCTV, QV periscope and other technologies are used to detect the sewage pipes in the area. The amount of external water found in the inspection accounts for 85% of the measured external water volume, which shows that the method is reasonable and effective. At the same time, it also provides data support and guidance for the external water inspection work. The collected sewage water quality data in the area can be further analyzed and the problems of the sewage system in the area can be comprehensively evaluated.

The invention is not limited to the above-mentioned embodiments. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the technical principles of the invention. These improvements and modifications should also be regarded as the protection scope of the invention.

Claims (2)

1. A method for calculating the amount of external water in a regional sewage system based on a typical plot, characterized by comprising the following steps: (1) Deploy monitoring points and obtain flow and water quality data at the monitoring points: select a monitoring area within the area of the sewage system, and select a number of monitoring points within the monitoring area; perform flow monitoring and water quality testing on each monitoring point to obtain the flow rate and water quality of the monitoring point; the water quality testing method is to measure the ammonia nitrogen water quality concentration; The monitoring points include primary monitoring points and secondary monitoring points; the method for setting the primary monitoring points and the secondary monitoring points is: according to the topological relationship of the sewage pipe network, the sewage collection point at the downstream end of the sewage main pipe is used as the primary monitoring point, the sewage flow threshold is set, and the sewage branch pipe with a water volume exceeding the sewage flow threshold is selected as the secondary monitoring point; The method of conducting flow monitoring and water quality testing at the primary monitoring point is to conduct flow monitoring and water quality testing once during the peak period of water use in dry weather and once during the low peak period of water use in dry weather; (2) Screening typical plots and calculating the background value of sewage water quality concentration in the area: Divide the area into several plots, obtain the water supply of each plot, and classify the plots according to land use type. Select typical plots from the plots of each land use type based on the water supply; calculate the proportion of water supply of each land use type through the water supply of each typical plot, and conduct flow monitoring and water quality testing on the sewage discharged from the typical plots to calculate the background value of sewage water quality of each land use type; combine the background value of sewage water quality of each land use type and the proportion of water supply of each land use type to deduce the background value of sewage water quality concentration in the area; the land use types include residential, administrative and public institutions, and industrial enterprises; The method of conducting flow monitoring and water quality testing on typical plots is to conduct flow monitoring and water quality testing once during the peak water use period and once during the low water use period; The specific method of selecting typical plots is as follows: summarize and count the water supply data in the area provided by the water company, calculate the water supply proportion of each land use type, and sort the water supply of each plot according to the land use type, and select several plots with large water consumption and uniform spatial distribution of the selected plots as typical plots under this land use type; The calculation formula for the background value of sewage water quality for each land use type is as follows: C _j = (C _j1 * Q _j1 + C _j2 * Q _j2 + … C _jn * Q _jn ) / (Q _j1 + Q _j2 + … Q _jn ), In the formula, _Cj represents the background value of sewage water quality of each land use type of this land use type, _Cjn represents the ammonia nitrogen concentration of the land of this land use type; _Qjn represents the sewage water volume of the land of this land use type; Calculate the baseline value of external water quality concentration: conduct water quality testing on external water in the monitoring area to obtain the external water quality, and calculate the baseline value of external water quality concentration based on the external water quality; the external water includes river water, groundwater, tap water, and construction water; The method for calculating the external water quality concentration benchmark value is to conduct water quality testing on the external water to obtain the actual measured ammonia nitrogen concentration of the external water quality and calculate the arithmetic mean to obtain the external water quality concentration benchmark value; (4) Calculate the amount of external water: Calculate the amount of internal and external water in the sewage system using the background value of sewage quality concentration in the area, the flow rate and water quality of the monitoring points, and the baseline value of external water quality concentration according to the water quality characteristic factor method; The specific calculation method of the amount of water inside and outside the sewage system is: The amount of external water at a monitoring point is calculated using the following formula: _Qw = (Cs _{- Cd} ) * _Qs / ( _Cd - _Cw ), In the formula, _Qw represents the amount of external water; _Cs represents the ammonia nitrogen concentration at a certain monitoring point; _Qs represents the average water volume at a certain monitoring point; _Cd represents the background value of sewage water quality concentration; _Cw represents the reference value of external water quality concentration; The amount of external water at all monitoring points is calculated using the above method. 2. According to the method for calculating the amount of external water in a district sewage system based on a typical plot of land according to claim 1, it is characterized in that the method for monitoring the amount of water is to monitor the amount of water through a Doppler flowmeter.