CN113919625A - A rainy day overflow pollution evaluation and control method - Google Patents

Abstract

The purpose of the present invention is to provide a rainy day overflow pollution evaluation and control method, comprising the steps of: determining an overflow pollution evaluation overflow outlet, an evaluation factor and an evaluation index; collecting water quality data of the overflow event of the evaluation overflow outlet; Calculate the evaluation index according to the collected water quality data; according to the calculation result of the evaluation index, determine the amount of pollution load to be reduced based on the management and control objectives, and formulate management and control measures; targeted control measures. The method evaluates the discharge characteristics of the overflow pollution by grades, determines the amount of pollution load to be reduced based on the management and control objectives, and proposes targeted treatment measures, thereby realizing the effective management and control of the overflow pollution, and has strong pertinence, strong applicability, and ease of use. operational advantages.

Description

Rainy day overflow pollution evaluation and control method

Technical Field

The invention belongs to the field of urban water environment treatment, and particularly relates to a rainy day overflow pollution evaluation and control method.

Background

The urban drainage system is an engineering facility system for treating and discharging urban sewage and rainwater, can effectively avoid the harm of sewage and rainstorm ponding, and ensures the orderly proceeding of urban life and production. Through continuous efforts for many years, the urban drainage pipe network architecture in China is basically formed. According to the environmental bulletin issued every year, the sewage treatment rate of each place is basically over 90 percent, the sewage collection and treatment rate is close to that of European and American countries, but the water quality difference of urban water bodies is large, and the true phase that sewage is directly discharged without being treated is hidden behind the high treatment rate, so that urban rivers are seriously polluted. With the promotion of black and odorous water body treatment, black and odorous water bodies in many cities are eliminated in fine days, but black and odorous river channels are accompanied by rain days. The urban water body turns black and turns smelly in rainy days, which is the bottleneck of black and odorous water body treatment and water environment quality improvement, and the rain overflow pollution of the water outlet becomes the root cause of the urban water body 'being black when raining'.

At present, domestic drainage systems mainly comprise a flow distribution system and a flow distribution system, and from long-term practical experience and practical situations of domestic and foreign urban drainage systems, the flow distribution system and the flow distribution system can not completely avoid overflow pollution, and overflow to a certain degree even has rationality within an environment capacity allowable range. The rainy day overflow pollution control is a key measure for promoting black and odorous river treatment, sponge city construction and sewage system quality improvement and efficiency improvement, but the treatment standard of combined system overflow pollution is lacked at present, so how to evaluate the overflow pollution and how to make reasonable management and control measures is a problem which needs to be solved urgently for the current overflow pollution control.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for evaluating and controlling overflow pollution in rainy days.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a rainy day overflow pollution evaluation and management and control method comprises the following steps:

s1, determining an overflow port for overflow pollution evaluation, evaluation factors and evaluation indexes;

s2, collecting water quality data of the overflow event of the evaluation overflow port;

s3, calculating an evaluation index according to the collected water quality data;

and S4, determining the pollution load amount to be reduced based on the control target according to the evaluation index calculation result, and making control measures.

The evaluation factor of the step S1 is total suspended matter TSS; the evaluation indexes comprise average pollutant concentration and initial scouring effect.

The water quality data in step S2 includes overflow water amount and pollutant concentration.

Step S2, the data collecting period is at least one flood season, the collected rainfall type at least comprises 2 types of light rain, medium rain, heavy rain and heavy rain, and the collecting mode is manual or automatic monitoring and collecting transient samples.

And step S2, sampling from the beginning of overflow of the overflow port, wherein the sampling time interval is 10min within the first 1h, the sampling time interval is 15-30min after 1h, the sampling time interval is 30-60min after 3h, and the sampling time length is not less than 80% of the total overflow time length.

The method for calculating the average Concentration (Event Mean Concentration) of the pollutants comprises the following steps

Wherein M is the pollutant load, g; v is the overflow amount, m³；C_tThe concentration of the pollutants of overflow sampling at the time t is mg/L; q_tIs the overflow in the t period, m³(ii) a j is the sampling frequency of a single overflow event; Δ t is the sampling time interval, min.

The evaluation of the initial scour effect is based on the initial scour coefficient b value: when b is more than 0 and less than or equal to 0.185, the strong initial scouring effect is obtained; when b is more than 0.185 and less than or equal to 0.862, the medium initial scouring effect is obtained; when b is more than 0.862 and less than or equal to 1, weak initial scouring effect is obtained; when b > 1, there is no initial scouring effect.

The method for calculating the initial scour coefficient b comprises the following steps

b＝log_FL，

In the formula, L is the pollutant cumulative load,%; m (t) is the pollutant accumulated load amount from zero to t time, kg; m is total pollutant load of the secondary rainfall, kg; f is the cumulative overflow amount,%; v (t) is the accumulated overflow of pollutants from zero to t, m³(ii) a V is total secondary rainfall event overflow, m³。

The management and control measures comprise one or more of interception, regulation and storage and terminal purification. For overflow ports with strong or moderate initial effects, regulation measures are preferably adopted; if the current storage and regulation facilities cannot reach the standard, intercepting is adopted; if the conditions cannot be met, new establishment or expansion of a storage and regulation facility is carried out, or end purification is carried out. And for overflow ports with weak or no initial effect, a combined mode of storage regulation and tail end purification is adopted.

The calculation method for reducing the pollution load amount comprises the following steps

W_{Can receive}＝(W_{General assembly}-W_{Morning sun})×0.8

M_{Can receive}＝W_{Can receive}×T_Overflow

M_Overflow＝M_{Runoff flow}+M_{Waste water}+M_{Flowing and accumulating material}＝(M_{Runoff flow}+M_{Waste water})/0.5

M_{Cutting down}＝M_Overflow-M_{Can receive}

In the formula, W_{Can receive}The soil-holding capacity of the water body in rainy days is g/s; w_{General assembly}The total pollutant carrying capacity of the receiving water body is g/s; w_{Dry sky}The actual pollution level of the receiving water body in dry days is g/s; m_{Can receive}The receiving water body can receive pollution load kg in rainy days; t is_OverflowMin is the time of occurrence of the overflow event; m_OverflowTotal load of regional overflow pollution, kg; m_{Runoff flow}The total load of rainfall runoff in the region is kg; m_{Waste water}The total load of sewage is kg for regional confluence or mixed connection; m_{Deposit material}Load of pipeline sediments, kg; m_{Cutting down}The total amount of pollution load reduction for regional overflow, kg; m_{Row of openings cut}The pollution load of the overflow port is reduced by kg; m_{Discharge port}Discharging pollution load kg for an overflow port.

Further, the method for evaluating and controlling the overflow pollution in rainy days further comprises the following steps: s5, accounting the load contribution rate of each pollution source, determining the main pollution sources, and implementing targeted control measures on the pollution sources.

The pollution source comprises one or more of surface runoff, confluent or mixed-joint sewage and pipeline sediment.

The method for calculating the load contribution rate of the pollution source comprises the following steps

M_{Flowing and accumulating material}＝M_Overflow-(M_{Runoff flow}+M_{Waste water})

M_{Waste water}＝V_{Waste water}×C_{Waste water}

M_{Runoff flow}＝V_{Runoff flow}×C_{Runoff flow}

In the formula, V_{Waste water}M is the total amount of the combined or mixed sewage³；C_{Waste water}The concentration of the confluent or mixed sewage is mg/L; v_{Runoff flow}M is the total amount of rainfall runoff³；C_{Runoff flow}The average concentration of rainfall runoff events is mg/L; c_RiThe average concentration of each runoff underlying surface in the overflow port catchment range is mg/L;

the runoff coefficient for each underlying surface; s_iThe catchment area, ha, of each underlying surface; i is the number of runoff underlying surfaces.

The invention has the beneficial effects that: TSS has better correlation with other water quality indexes such as COD, TN and TP in the rain overflow pollution, and the control and treatment of other pollutants can be effectively guided through TSS concentration evaluation; the invention combines the actual situation of most urban drainage systems at present, comprehensively considers various drainage ports, and is suitable for rainy day overflow pollution under different drainage systems; the proposed control measures are strictly based on the evaluation result of the overflow pollution emission characteristics, have the advantages of strong pertinence, strong applicability, easiness in operation and the like, and are suitable for popularization and use.

Detailed Description

The technical solutions of the present invention will be described in detail and fully with reference to the following specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

Example 1

A rainy day overflow pollution evaluation and management and control method comprises the following steps:

s1, selecting a plurality of overflow ports of different types in a certain urban area to evaluate overflow pollution, and taking total suspended matter TSS as a target water quality evaluation factor, wherein evaluation indexes comprise average pollutant concentration and initial scouring effect.

S2, collecting water quality data for evaluating overflow events of the overflow port, wherein the collected water quality data comprise overflow water volume and pollutant concentration, the collection data period is a first flood season, the collected rainfall types comprise light rain, medium rain, heavy rain and heavy rain, and the collection mode is that instantaneous samples are collected through manual monitoring; sampling is carried out from the beginning of overflow of the overflow port, the sampling time interval is 10min within the first 1h, the sampling time interval is 15-30min after 1h, the sampling time interval is 30-60min after 3h, and the time length of each acquisition is not less than 80% of the total overflow time length.

S3, calculating an evaluation index according to the collected water quality data; the method for calculating the average Concentration (Event Mean Concentration) of the pollutants comprises the following steps

Wherein M is the pollutant load, g; v is the overflow amount, m³；C_tThe concentration of the pollutants of overflow sampling at the time t is mg/L; q_tIs the overflow in the t period, m³(ii) a j is the sampling frequency of a single overflow event; Δ t is the sampling time interval, min.

The method for calculating the initial scour coefficient b comprises the following steps

b＝log_FL，

In the formula, L is the pollutant cumulative load,%; m (t) is the pollutant accumulated load amount from zero to t time, kg; m is total pollutant load of the secondary rainfall, kg; f is the cumulative overflow amount,%; v (t) is the accumulated overflow of pollutants from zero to t, m³(ii) a V is total secondary rainfall event overflow, m³。

The maximum emission limit value of the target water quality evaluation factor TSS is set according to the emission standard of 50mg/L specified in the evaluation Standard for sponge City construction (GB/T51345-2018), the average concentration of the overflow port events is lower than 50mg/L and can be directly discharged, and the initial flushing effect evaluation is carried out on the overflow port higher than 50 mg/L.

The average concentration of the overflow event TSS under different rainfall conditions is approximately shown in Table 1 by calculation according to measured data of an overflow port of the mixed rainwater and sewage prepared in a certain city.

TABLE 1 mean concentration of Overflow event TSS under different rainfall conditions

Incident of rainfall	1	2	3	4	5	6
							TSS mean concentration (mg/L)	164.2	133.3	211.7	129.5	117.1	119.4

The evaluation of the initial scour effect is based on the initial scour coefficient b value: when b is more than 0 and less than or equal to 0.185, the strong initial scouring effect is obtained; when b is more than 0.185 and less than or equal to 0.862, the medium initial scouring effect is obtained; when b is more than 0.862 and less than or equal to 1, weak initial scouring effect is obtained; when b > 1, there is no initial scouring effect.

And S4, determining the pollution load amount to be reduced based on the control target according to the evaluation index calculation result, and making control measures.

The management and control measures comprise one or more of interception, regulation and storage and terminal purification. For overflow ports with strong or moderate initial effects, regulation measures are preferably adopted; if the current storage and regulation facilities cannot reach the standard, intercepting is adopted; if the conditions cannot be met, new establishment or expansion of a storage and regulation facility is carried out, or end purification is carried out. And for overflow ports with weak or no initial effect, a combined mode of storage regulation and tail end purification is adopted.

The calculation method for reducing the pollution load amount comprises the following steps

W_{Can receive}＝(W_{General assembly}-W_{Morning sun})×0.8

M_{Can receive}＝W_{Can receive}×T_Overflow

M_Overflow＝M_{Runoff flow}+M_{Waste water}+M_{Deposit material}＝(M_{Runoff flow}+M_{Waste water})/0.5

M_{Cutting down}＝M_Overflow-M_{Can receive}

In the formula, W_{Can receive}The soil-holding capacity of the water body in rainy days is g/s; w_{General assembly}The total pollutant carrying capacity of the receiving water body is g/s; w_{Dry sky}The actual pollution level of the receiving water body in dry days is g/s; m_{Can receive}The receiving water body can receive pollution load kg in rainy days; t is_OverflowMin is the time of occurrence of the overflow event; m_OverflowTotal load of regional overflow pollution, kg; m_{Runoff flow}The total load of rainfall runoff in the region is kg; m_{Waste water}The total load of sewage is kg for regional confluence or mixed connection; m_{Deposit material}Load of pipeline sediments, kg; m_{Cutting down}The total amount of pollution load reduction for regional overflow, kg; m_{Row of openings cut}The pollution load of the overflow port is reduced by kg; m_{Discharge port}Discharging pollution load kg for an overflow port.

According to relevant regulations in the evaluation Standard for sponge City construction (GB/T51345-2018), the total reduction amount of the annual average overflow pollutants TSS of combined overflow pollution is controlled to be not lower than 50%. Because of the comprehensive consideration of the occupied area of the storage tank, the economic cost and the like, the optimal operation standard of the storage and regulation facility is the overflow water amount of 25 percent of the closure secondary overflow event, 50 percent of pollutant load is intercepted, and the mode of setting the storage and regulation tank in the process is suitable for the drainage area with larger catchment area. The pollutant carrying capacity of the water body is comprehensively calculated according to natural properties of the water body, the influx condition of various types of pollution sources and the like, and considering non-point source pollution directly entering a river from a side slope in rainy days or pollution load brought by a rainwater background, the pollution load discharged into the water body by various overflow discharge openings, underdrains and the like is lower than 80% of the actual pollutant carrying capacity of the river channel in rainy days.

The overflow pollution has the characteristics of randomness, complexity, persistence and the like, has higher requirements on the treatment time and the flow of the terminal purification process, is not suitable for selecting a biological process, is suitable for adopting physical processes such as rapid filtration, sedimentation, cyclone separation and the like, and the overflow discharge outlet with lower pollution concentration can be discharged to an artificial wetland system. The effluent quality of the tail end purification process is based on the 1-grade A discharge of a sewage treatment plant, a near principle is adopted when a tail end purification device is arranged, and the treated tail water is discharged to a peripheral river channel as make-up water.

S5, accounting the load contribution rate of each pollution source, determining the main pollution sources, and implementing targeted control measures on the pollution sources.

The pollution source comprises one or more of surface runoff, confluent or mixed-joint sewage and pipeline sediment.

The method for calculating the load contribution rate of the pollution source comprises the following steps

M_{Deposit material}＝M_Overflow-(M_{Runoff flow}+M_{Waste water})

M_{Waste water}＝V_{Waste water}×C_{Waste water}

M_{Runoff flow}＝V_{Runoff flow}×C_{Runoff flow}

In the formula, V_{Waste water}M is the total amount of the combined or mixed sewage³；C_{Waste water}The concentration of the confluent or mixed sewage is mg/L; v_{Runoff flow}M is the total amount of rainfall runoff³；C_{Runoff flow}The average concentration of rainfall runoff events is mg/L; c_RiThe average concentration of each runoff underlying surface in the overflow port catchment range is mg/L;

the runoff coefficient for each underlying surface; s_iThe catchment area, ha, of each underlying surface; i is the number of runoff underlying surfaces.

The surface runoff monitoring selects various underlying surfaces such as roads, greenbelts, roofs and the like in a drainage area to carry out synchronous monitoring of water quantity and water quality, and the runoff pollution characteristics of different underlying surfaces are mastered; monitoring the drainage area with confluent or mixed sewage in a dry day to master the daily change rule of the sewage amount and concentration; because the pipeline sediment has higher sampling difficulty in rainy days, the contribution of the pollution load of the pipeline sediment is obtained based on the calculation of the difference value between the total overflow pollution load and the runoff and sewage load. Table 3 shows the contribution rate of three pollution sources at a plurality of overflow ports in a typical rainfall event of a certain city.

TABLE 3 Overflow Port traceability analysis of a certain city

Source of pollution	Surface runoff	Mixed sewage	Pipeline deposit
				Overflow port 1	12.6％	21.1％	66.3％
Overflow port 2	9.5％	52.3％	38.2％
				Overflow port 3	41.9％	0％	58.1％

Aiming at the overflow port 1, pipeline sediments are a main pollution output source, and dredging repair is preferably carried out by adopting a pipeline process control technology, such as winch dredging, high-pressure water jet and the like; aiming at the overflow port 2, overflow pollution mainly comes from the interior of the pipeline, and the wrong mixed joint is preferably repaired and rectified, so that the interception multiple is increased, and dredging repair is carried out; to overflow mouth 3, should develop sponge city construction in corresponding drainage zone, add low influence development facility, the lime green combines, like biological detention pond, green roof, permeable paving etc. should regularly carry out the desilting restoration in the pipeline simultaneously, strengthen follow-up maintenance management.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein are included in the scope of the present invention, and the scope of the present invention is subject to the scope of the claims.

Claims (10)

1. A rainy day overflow pollution evaluation and management and control method is characterized by comprising the following steps:

s1, determining an overflow port for overflow pollution evaluation, evaluation factors and evaluation indexes;

s2, collecting water quality data of the overflow event of the evaluation overflow port;

s3, calculating an evaluation index according to the collected water quality data;

s4, determining the pollution load amount to be reduced based on a control target according to the evaluation index calculation result, and making a control measure;

the evaluation factor of the step S1 is total suspended matter TSS; the evaluation indexes comprise average pollutant concentration and initial scouring effect;

the water quality data in step S2 includes overflow water amount and pollutant concentration.

2. The method for evaluating and managing the overflow pollution in the rainy days according to claim 1, wherein the data acquisition period in the step S2 is at least one flood season, the acquired rainfall types at least comprise 2 types of light rain, medium rain, heavy rain and heavy rain, and the acquisition mode is manual or automatic monitoring and acquisition of instantaneous samples.

3. The method for evaluating and managing the overflow pollution in the rainy day according to claim 1 or 2, wherein in step S2, sampling is performed from the beginning of overflow at the overflow port, the sampling time interval is 10min within the first 1h, the sampling time interval is 15-30min after 1h, the sampling time interval is 30-60min after 3h, and the sampling time is not less than 80% of the total overflow time.

4. The method for evaluating and managing overflow pollution in rainy days according to claim 1, wherein the method for calculating the average concentration of pollutants is

Wherein M is the pollutant load, g; v is the overflow amount, m³；C_tThe concentration of the pollutants of overflow sampling at the time t is mg/L; q_tIs the overflow in the t period, m³(ii) a j is the sampling frequency of a single overflow event; Δ t is the sampling time interval, min.

5. The method for evaluating and managing rainfall overflow pollution according to claim 1, wherein the evaluation of the initial scouring effect is based on an initial scouring coefficient b value: when b is more than 0 and less than or equal to 0.185, the strong initial scouring effect is obtained; when b is more than 0.185 and less than or equal to 0.862, the medium initial scouring effect is obtained; when b is more than 0.862 and less than or equal to 1, weak initial scouring effect is obtained; when b > 1, there is no initial scouring effect.

6. The method for evaluating and managing the overflow pollution in the rainy day according to claim 5, wherein the initial scouring coefficient b is calculated by

In the formula, L is the pollutant cumulative load,%; m (t) is the pollutant accumulated load amount from zero to t time, kg; m is total pollutant load of the secondary rainfall, kg; f is the cumulative overflow amount,%; v (t) is the accumulated overflow of pollutants from zero to t, m³(ii) a V is total secondary rainfall event overflow, m³。

7. The method for evaluating and managing the overflow pollution in the rainy day according to claim 1, wherein the management and control measures comprise one or more of interception, regulation and terminal purification.

8. The method for evaluating and managing overflow pollution in rainy days according to claim 1, wherein the calculation method for reducing pollution load is

W_{Can receive}＝(W_{General assembly}-W_{Morning sun})×0.8

M_{Can receive}＝W_{Can receive}×T_Overflow

M_Overflow＝M_{Runoff flow}+M_{Waste water}+M_{Deposit material}＝(M_{Runoff flow}+M_{Waste water})/0.5

M_{Cutting down}＝M_Overflow-M_{Can receive}

In the formula, W_{Can receive}The soil-holding capacity of the water body in rainy days is g/s; w_{General assembly}The total pollutant carrying capacity of the receiving water body is g/s; w_{Dry sky}The actual pollution level of the receiving water body in dry days is g/s; m_{Can receive}The receiving water body can receive pollution load kg in rainy days; t is_OverflowMin is the time of occurrence of the overflow event; m_OverflowTotal load of regional overflow pollution, kg; m_{Runoff flow}The total load of rainfall runoff in the region is kg; m_{Waste water}The total load of sewage is kg for regional confluence or mixed connection; m_{Deposit material}Load of pipeline sediments, kg; m_{Cutting down}The total amount of pollution load reduction for regional overflow, kg; m_{Row of openings cut}The pollution load of the overflow port is reduced by kg; m_{Discharge port}Discharging pollution load kg for an overflow port.

9. The rainy day overflow pollution evaluation and management and control method according to claim 1, further comprising the steps of: s5, accounting the load contribution rate of each pollution source, determining the main pollution sources, and implementing targeted control measures on the pollution sources.

10. The method for evaluating and managing overflow pollution in rainy days according to claim 9, wherein the pollution sources comprise one or more of surface runoff, interflow or mixed sewage and pipeline sediment; the method for calculating the load contribution rate of the pollution source comprises the following steps

M_{Deposit material}＝M_Overflow-(M_{Runoff flow}+M_{Waste water})

M_{Waste water}＝V_{Waste water}×C_{Waste water}

M_{Runoff flow}＝V_{Runoff flow}×C_{Runoff flow}

In the formula, V_{Waste water}M is the total amount of the combined or mixed sewage³；C_{Waste water}The concentration of the confluent or mixed sewage is mg/L; v_{Runoff flow}M is the total amount of rainfall runoff³；C_{Runoff flow}The average concentration of rainfall runoff events is mg/L; c_RiThe average concentration of each runoff underlying surface in the overflow port catchment range is mg/L;

the runoff coefficient for each underlying surface; s_iThe catchment area, ha, of each underlying surface; i is the number of runoff underlying surfaces.