Method for estimating nutrient substances of faeces discharged from families to surface water

Abstract

The invention relates to a method for estimating the content of nutrient substances in faeces discharged from families to surface water under the influence of social economic development and climate change, which comprises the following steps of: constructing a future discharge scene according to five shared social economic paths SSPs, and calculating the content of nutrient substances in faeces discharged from families to surface water by means of a point source model of a global nutrition model (IMAGE-GNM); generating, transferring, treating and discharging processes of nutrient substances in the excrement under various future scenes are simulated, and the nutrient load capacity discharged to the receiving water body is estimated; a climate mode is coupled, meteorological data such as temperature and rainfall of a future research city are estimated based on a typical concentration path RCPs, and by means of an eutrophication module in WASP water quality software, the change condition of the content of nutrient substances in a receiving water body under the influence of climate change is simulated and quantified; therefore, dynamic change of nutrition load from a human system to a natural system is described, and human system behaviors are fed back and adjusted. According to the obtained content change condition of the nutrient substances in the receiving water body, analyzing future environment pressure caused by nutrient discharge in human excrement, verifying the implementation effect of an excrement collection and treatment technology in a future environment, and providing suggestions for reversely guiding and adjusting an excrement treatment plan to reduce pollution of excrement to surface water. According to the method, a theoretical basis can be provided for future pressure prediction of nutrient discharge collected from human excrement, and decision support is provided for decision makers to formulate feasible excrement collection, clearance, treatment and discharge management specifications.

Description

Technical Field

[0001] The present invention belongs to the field of surface water quality prediction, and in particular relates to a method for estimating the nutrient content in feces discharged from households into surface water under the influence of socio-economic development and climate change. Background Art

[0002] Feces can pollute water bodies. Excessive nutrients can cause eutrophication of water bodies, seriously affecting ecosystem services such as drinking water, fisheries, and aquaculture; a large number of pathogens can also lead to the spread of diseases. In 2017, nearly 2 billion people in the world still drank water contaminated by feces, facing the risk of contracting a variety of diseases and even death. Therefore, fecal pollution will not only seriously pollute the ecological environment, but also endanger human life and health. At present, households are the main source of feces in densely populated urban areas. The environmental pressure caused mainly depends on the level of sanitation, whether it is connected to the sewer system, and the degree of wastewater treatment, and is finally discharged into surface water bodies.

[0003] Eutrophication is one of the main consequences of fecal pollution of water bodies. Specifically, the nitrogen (N) and phosphorus (P) nutrient loads in feces are discharged into surface water bodies, causing algae to grow wildly in ecosystems such as rivers and lakes, thereby damaging water quality. Reducing N and P nutrient loads is crucial to the restoration of eutrophication of surface water bodies, and the nutrient load in urban household feces is one of the most likely potential sources to be reduced. The production, transportation, treatment, and discharge of N and P substances in feces are closely related to the level of socioeconomic development, and the nutrient content ultimately discharged into surface water bodies will also be affected by climate change and change to a certain extent. Therefore, estimating the nutrient content of feces in the process from households to surface water in the future requires considering both the level of socioeconomic development and the degree of global climate change. Summary of the invention

[0004] In response to the problem that existing surface water nitrogen and phosphorus load predictions do not comprehensively consider the impact of socio-economic development and climate change, the present invention provides a method for estimating the nutrient content in feces discharged from households to surface water under the influence of socio-economic development and climate change. The method of the present invention ensures that the degree of socio-economic development and the degree of global climate change are taken into account when estimating the nutrient content in feces discharged from households to surface water in the future.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for estimating the nutrient content of feces discharged from households to surface water under the influence of socioeconomic development and climate change, comprising the following steps:

[0007] Step 1: Survey baseline data, construct future emission scenarios based on five shared socioeconomic pathways (SSPs), and use the point source model of the global nutrient model (IMAGE-GNM) to simulate the production, transportation, processing and emission of nutrients in feces under various future scenarios, and estimate the nutrient load discharged to receiving water bodies;

[0008] Step 2: Couple the climate model to estimate the future temperature and rainfall of the city based on the representative concentration pathways (RCPs). Use the eutrophication module in the WASP water quality software to simulate and quantify the changes in nutrient content in the receiving water under the influence of climate change, thereby describing the dynamic changes in nutrient load from the human system to the natural system and providing feedback to regulate the behavior of the human system.

[0009] Step three: Based on the changes in the nutrient content in the receiving water, analyze the future environmental pressure caused by nutrient emissions from human excreta, verify the implementation effect of feces collection and treatment technology in the future environment, and propose reverse guidance and adjustments to the feces treatment plan to reduce feces pollution to surface water.

[0010] In the above step 1, the data of the baseline survey include but are not limited to population size, urban population, GDP, daily per capita feces and urine volume, seasonal per capita feces and urine volume, annual per capita feces and urine volume, national and local environmental protection policies, residents' living habits, environmental awareness, sanitation level of the city, toilet conditions, whether there is a sewer system, septic tank treatment technology and treatment level, number of sewage treatment plants and nutrient removal level and other urban development factors, in addition, it also includes the hydrological and water quality of the receiving water body and local climate factors;

[0011] In the above step 1, various future emission scenarios are constructed based on SSPs to quantify the future nutrient content of feces from households discharged into surface water under the influence of socioeconomic drivers, among which the total household emission is proportional to the population size, the income level affects the protein consumption in human diet, the degree of sewage system connection (SC), the number of sewage treatment plants and their nutrient removal efficiency level (NR) are related to per capita income, scientific and technological development level, environmental protection policies, etc.;

[0012] In step 1 above, IMAGE is an integrated assessment modeling framework, and the Global Nutrient Model (GNM) is part of the IMAGE framework, which describes the global nitrogen and phosphorus flow cycles. Regarding the N and P nutrient emission process in household feces, the IMAGE-GNM point source model considers human food consumption as the main source of N and P in domestic wastewater. It is assumed that the total excretion in urine and feces is equal to the intake minus the loss;

[0013] In the above step 2, six typical concentration pathways RCPs (RCP1.9, RCP2.6, RCP3.4, RCP4.5, RCP6.0, and RCP8.5) are set based on the direct or indirect radiative forcing caused by greenhouse gases, aerosols, and various external influencing factors that depict the most likely future life and development mode of human society to estimate the changes in temperature and precipitation in the study area in the future.

[0014] Compared with existing methods, the present invention proposes a method for estimating the nutrient content in feces discharged from households to surface water under the influence of socio-economic development and climate change.

[0015] The advantages of the present invention mainly include:

[0016] 1. The present invention couples human and natural systems to simulate the transfer process and content changes of nutrients in feces from households to surface water;

[0017] 2. For the first time, a matrix of shared socioeconomic pathways (SSPs) and representative concentration pathways (RCPs) was combined in the prediction of nutrients in feces discharged from households to surface water;

[0018] 3. A future estimation model of nutrient emissions from feces from households to surface water using the GNM-SSPs-RCPs-WASP was constructed, taking into account the impacts of socioeconomic development and climate change. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the method of the present invention.

[0020] Figure 2 Technical roadmap of the method of the present invention. DETAILED DESCRIPTION

[0021] Example 1

[0022] First, the study cities were selected and the baseline data were investigated. The survey data included population size, urban population, GDP, daily per capita feces and urine volume, seasonal per capita feces and urine volume, annual per capita feces and urine volume, national and local environmental protection policies, residents' living habits, environmental awareness, sanitation level, toilet conditions, whether there is a sewer system, septic tank treatment technology and treatment level, number of sewage treatment plants and nutrient removal level and other urban development factors. In addition, the hydrological and water quality of receiving water bodies and local climate factors were also included. Then, the five future shared socioeconomic pathways (SSPs) proposed by the Intergovernmental Panel on Climate Change (IPCC) of the United Nations were selected to construct various emission scenarios in the future to quantify the future nutrient content from feces discharged from households to surface water under the influence of socioeconomic driving factors. Among them, the total household emission is proportional to the population size, the income level affects the protein consumption in human diet, and the degree of sewage system connection (SC), the number of sewage treatment plants and their nutrient removal efficiency (NR) are related to per capita income, scientific and technological development level, environmental protection policies, etc. Finally, based on the IMAGE-GNM point source model, human food consumption was taken as the main source of N and P in domestic wastewater, and the total excretion of urine and feces was assumed to be equal to the intake minus losses. Regression analysis was performed based on historical data on the relationship between GDP and protein consumption, the degree of sewage system connection, and the degree of nutrient removal by sewage treatment plants to obtain regression relationships. The future treatment trend of nutrients in feces was simulated based on the obtained regression equation, and the trend was corrected based on baseline data. Since the model parameters may be uncertain, the sensitivity analysis of the parameters was carried out with the help of the Latin hypercube sampling method to quantify the impact of the uncertainty of the input parameters on the model output. Multiple runs were performed for the five SSPs in 2010 and 2050 to calculate the standard regression coefficients (SRCs) of the input parameters and the model output N and P. In this way, the generation, transportation, treatment and discharge processes of nutrients in feces under various future scenarios were simulated, and the nutrient load discharged to the receiving water body was estimated.

[0023] Example 2

[0024] First, a receiving water body in the study city is selected as the research object. According to the rules of applicability of climate models and availability of model data, the climate model is downscaled and analyzed to select the climate model suitable for the study area. The effects of temperature and precipitation events are simulated and verified based on historical data and observational data such as precipitation and temperature. Afterwards, with the help of the downscaled climate model, six typical concentration pathways RCPs (RCP1.9, RCP2.6, RCP3.4, RCP4.5, RCP6.0, RCP8.5) are set based on the direct or indirect radiative forcing caused by greenhouse gases, aerosols and various external factors depicted by the most likely way of life and development of human society in the future. The changes in temperature and precipitation in the study area in the future are estimated, and the numerical values ​​of climate data in the local historical period are used for simulation and verification. Finally, the water bodies were generalized through the topographic maps, elevation maps, basic water parameters and other hydrological and water quality data of the receiving water bodies of the study city collected in the early stage, and the WASP water quality model was established. The model was calibrated and verified using measured data, sanitary remote sensing data, historical data and previous research results. The meteorological data such as temperature and precipitation provided by the selected climate model were embedded in the calibrated WASP model, and the point source emission data of nutrient load after urban feces treatment were input to simulate the content of nutrients in the receiving water bodies of the study city under the dual influence of socio-economic development and climate change.

Claims

1. A method for estimating the nutrient content of feces discharged from households to surface water under the influence of socio-economic development and climate change, characterized in that: The steps include: Step 1: Survey baseline data, construct future emission scenarios based on five shared socioeconomic pathways (SSPs), and use the point source model of the global nutrient model (IMAGE-GNM) to simulate the production, transportation, processing and emission of nutrients in feces under various future scenarios, and estimate the nutrient load discharged to receiving water bodies; Step 2: Couple the climate model to estimate the future temperature and rainfall of the city based on the representative concentration pathways (RCPs). Use the eutrophication module in the WASP water quality software to simulate and quantify the changes in nutrient content in the receiving water under the influence of climate change, thereby describing the dynamic changes in nutrient load from the human system to the natural system and providing feedback to regulate the behavior of the human system. Step three: Based on the changes in the nutrient content in the receiving water, analyze the future environmental pressure caused by nutrient emissions from human excreta, verify the implementation effect of feces collection and treatment technology in the future environment, and propose reverse guidance and adjustments to the feces treatment plan to reduce feces pollution to surface water.

2. The method according to claim 1, characterized in that: In step 1, the data of the baseline survey include but are not limited to population size, urban population, GDP, daily per capita feces and urine volume, seasonal per capita feces and urine volume, annual per capita feces and urine volume, national and local environmental protection policies, residents' living habits in the study city, environmental awareness, sanitation level of the study city, toilet conditions, whether there is a sewer system, septic tank treatment technology and treatment level, number of sewage treatment plants and nutrient removal level and other urban development factors. In addition, it also includes the hydrological and water quality conditions of the receiving water body and local climate factors.

3. The method according to claim 1, characterized in that: In the step 1, various future emission scenarios are constructed based on SSPs to quantify the future nutrient content of feces from households discharged into surface water under the influence of socioeconomic driving factors, where the total household emission is proportional to the population size, the income level affects the protein consumption in the human diet, and the degree of sewage treatment system connection (SC), the number of sewage treatment plants and their nutrient removal efficiency level (NR) are related to per capita income, scientific and technological development level, environmental protection policies, etc.

4. The method according to claim 1, characterized in that: In step 1, IMAGE is an integrated assessment modeling framework, and the Global Nutrient Model (GNM) is part of the IMAGE framework, which describes the global nitrogen and phosphorus flow cycles. Regarding the N and P nutrient emission process in household feces, the IMAGE-GNM point source model considers human food consumption as the main source of N and P in domestic wastewater. It is assumed that the total excretion of urine and feces is equal to the intake minus the loss.

5. The method according to claim 1, characterized in that: In the second step, six typical concentration pathways RCPs (RCP1.9, RCP2.6, RCP3.4, RCP4.5, RCP6.0, and RCP8.5) are set based on the direct or indirect radiative forcing caused by greenhouse gases, aerosols, and various external influencing factors that depict the most likely future life and development mode of human society to estimate the changes in temperature and precipitation in the study area in the future.

Images