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Flow measurement: at present, most countries in the world adopt the control method of combining pollutant emission concentration control and total amount control. Therefore, when understanding the sewage quality, we should also measure the water level (m), flow rate (M / s), flow rate (m3 / s) and other hydrological parameters to calculate the environmental capacity, control the emission of pollution sources, and estimate the pollution control effect. (1) Measurement of surface water flow For larger rivers, hydrological departments generally have hydrological monitoring sections, so the measured parameters should be used as much as possible. If there is no hydrological section in the monitored river section, the section with stable hydrological parameters and representative discharge should be selected for measurement one   Velocity area method First, divide the measuring section into several small pieces, measure the area and velocity of each small piece, calculate the corresponding flow, and then add up the flow of each small section, that is, the water flow on the section                                                        ( 3-1) Where: Q -- water flow, m3 / S; ——The average horizontal velocity on each small section, M / S; F1, F2... FN -- the area of each small section, M2. The flow velocity is mostly measured by current meter, which includes single point current meter (such as mechanical current meter, electric current meter, etc.), three-dimensional current meter (such as Doppler acoustic current meter, etc.) and multi-functional intelligent current meter. The flow velocity range of 0.020-10m / s can be measured by using different settlement devices. two   Buoy method Buoy method is a simple method to measure the velocity of water in small rivers and canals. During the survey, a straight river section is selected to measure the three cross-sectional areas of the starting point, the middle point and the end point within 2m interval of the river section, and the average cross-sectional area is calculated on this basis. Put the buoy in the upstream to measure the time required for the buoy to flow through the determined reach (L). Repeat the measurement for several times to calculate the average time (T) to calculate the flow velocity (LGT), and then calculate the flow rate according to the following formula:                                                               ( 3-2) Where: Q -- water flow, m3 / min; ——Average velocity of buoy, M / s, i.e. L / T; S -- cross section area of discharge, M2. K is the coefficient of buoy, which is related to the air resistance and the uniformity of velocity distribution on the cross section. Generally, it needs to be calibrated with a current meter, and its range is 0.84-0.90. (2) Waste water flow measurement one   Flowmeter method At present, more than ten kinds and hundreds of kinds of sewage flow meters have been developed at home and abroad, mainly including volumetric, differential pressure, turbine, area, electromagnetic, ultrasonic and overflow weir flowmeter. The suitable flowmeter can be selected according to the flow range and test accuracy of the actual water flow. two   Volumetric method The sewage is introduced into a container or sewage pool with known volume, the time of full flow of the container or sewage pool is measured, and then the volume of the container or sewage pool with its receiving volume is divided, and the flow can be calculated. This method is simple and suitable for measuring the continuous or intermittent discharge of sewage with small sewage flow. three   Overflow weir plate method Overflow weir plate method is the main method to measure water flow. This method is suitable for the measurement of water flow in irregular sewers. In this method, triangular or rectangular or trapezoidal weir plates are used to block the flow and form overflow weir. The water head and water level before and after the weir plate are measured and the flow is calculated. Figure 3-3 is a schematic diagram of flow measurement with triangular weir method. The flow calculation formula is as follows:                                    ( 3-3) Where: Q -- water flow, m3 / S; H -- weir head height, m;                         K -- discharge coefficient;                                            D -- height from flow bottom to weir edge, m; B -- upstream flow width of weir, M. Under the following conditions, the error of the above formula is < ± 1.4%: 0.5m≤ B≤ 1.2m 0.1m≤ D≤ 0.75m                                        0.07m≤ h≤ 0.26m                     H≤ B/3
Water pollution sources include industrial waste water source and domestic sewage source. Before formulating the monitoring plan, the first step is to conduct investigation and research, collect relevant data, check the water use, the type of wastewater or sewage, the main pollutants and the discharge direction and discharge, the number and location of the sewage outlets in the workshop, factory or area, the wastewater treatment, whether it is discharged into the river, river, lake and sea, and whether there are seepage pits in the area. Then, the comprehensive analysis is carried out to determine the monitoring items, monitoring points, sampling time and frequency, sampling and monitoring methods and technologies, and quality assurance procedures, measures and implementation plans are formulated. (1) Layout of sampling points one   industrial waste water (1) The first type of pollutants shall be sampled at the discharge port of the workshop or workshop treatment facilities; The second type of pollutants are sampled at the unit total discharge port; (2) In the internal monitoring of industrial enterprises, the sampling is usually selected at the total discharge port, the discharge port of workshop or workshop and the discharge point of relevant processes or equipment; (3) For factories with existing wastewater treatment facilities, sampling points shall be set at discharge orifice of treatment facilities. In order to understand the effect of wastewater treatment, sampling points can be set at the inlet and outlet respectively; (4) In the sewage discharge channel, the sampling point shall be located in the place where the channel is relatively straight, the water quantity is stable and there is no sewage inflow upstream. two   domestic sewage (1) Urban sewage pipe network: sampling point shall be set at the inspection well where the branch pipe of non resident domestic drainage is connected to the main pipe of urban sewage; Different locations of the main sewage pipes in cities; Different positions of sewage entering the water body; (2) Urban sewage treatment plant: set sampling points at the sewage inlet and the total discharge orifice. If the treatment efficiency of each sewage treatment unit needs to be monitored, sampling points can be set at the inlet and outlet of each treatment unit. In addition, sludge sampling points should be set. (2) Sampling time and frequency one   industrial waste water The pollutant content and discharge of industrial wastewater are often different with the process conditions and the starting rate. Therefore, the selection of sampling time, cycle and frequency is a more complex problem. For the pollution sources with discharge of wastewater ≥ 5000t / D, automatic on-line water quality monitoring instrument shall be installed, and continuous automatic monitoring shall be conducted at any time; The main pollution sources with wastewater discharge of 1000-5000t / d need to be installed with equal proportion automatic sampler and flow measuring device, and the monitoring shall be conducted once / day; The pollution source with wastewater discharge ≤ 1000t / D shall be monitored for 3-5 times / month. Monitoring water quality and water quantity simultaneously; The monitoring frequency of unstable pollution sources depends on the production cycle and the pollution discharge. two   domestic sewage For the sewage of urban pipe network, the mixed sample of flow ratio can be collected from the total discharge outlet in the rainy, flat and dry seasons of one year, and sampling can be conducted once every day and night and every 4 hours. In the municipal sewage treatment plant, in order to regulate the treatment process parameters and supervise the external drainage water quality, the sewage samples shall be collected from the treatment unit and the main discharge port every day to conduct routine monitoring on the index items.
Water stored in the soil and rock voids (pores, fissures, dissolution gaps) is collectively referred to as groundwater. The groundwater is buried in different depths of the stratum. The changes of the fluidity and water quality parameters are slow compared with the surface water. (1)    Layout principle of monitoring network (1) In general and macro, different hydrogeological units should be controlled, and the environmental quality and spatial changes of groundwater quality of underground water system in the region should be reflected; (2) The monitoring focuses on aquifers for water supply purposes; (3) Monitor the key polluted areas and areas where pollution may occur, monitor the pollution degree and dynamic changes of the pollution sources to the groundwater, so as to reflect the pollution characteristics of the groundwater in the area; (4) It can reflect the water supply source of groundwater and the hydraulic connection between groundwater and surface water; Monitor the funnel area, ground subsidence and special hydrogeological problems of groundwater level drop; (5) Considering the influence of industrial construction projects, mine development, water conservancy projects, oil development and agricultural activities on groundwater; (6) The principle of monitoring the density of network layout is that the main water supply area is dense and the general area is sparse; The urban area is dense and the countryside is sparse; Groundwater pollution The serious areas are dense and the non pollution areas are sparse. Obtain enough representative environmental information with the minimum monitoring points as possible; The monitoring points shall be selected from the frequently used civilian wells, production wells and spring water as far as possible. (2) Investigation, research and data collection Before setting up monitoring point network, relevant local hydrological and geological data shall be collected, including: (1) Geological map, profile, relevant parameters of existing well (well location, drilling date, well depth, well forming method, aquifer location, pumping test data, drilling unit, use value, water quality data, etc.); (2)   The geographical distribution and hydrological characteristics of the river, river, lake and sea as the local groundwater supply source (water level, water depth, velocity and flow), water conservancy facilities, utilization of surface water and water quality; (3) Aquifer distribution, groundwater supply, runoff and discharge direction, groundwater quality type and groundwater resources development and utilization; Spring water exposure, origin type, supply source, flow rate, water temperature, water quality and utilization; (4) Regional planning and development, distribution of urban and industrial areas, resource development and land use, application of fertilizer and pesticide, water pollution sources and sewage discharge characteristics. (3)    Sample point settings Because of the complexity and particularity of hydrogeology and other factors, the setting of groundwater sampling points is more complex. The density of monitoring points in general national controlled groundwater is not less than 100km2   0.1 well, each county shall have at least 1-2 wells, and the plain (including basin) area is generally every 100km2   0.2 well, important water source or polluted areas shall be properly encrypted. Desert area, hill area and karst mountain area can be selected as required to set monitoring points in typical representative areas. The density of monitoring points of provincial and municipal groundwater monitoring points can be determined according to the specific situation and relevant specifications. Monitoring points (monitoring wells) should be set in the areas where groundwater is the main water source, the area with high incidence of drinking water type local diseases (such as high fluorine disease), and the areas with great influence on the regional groundwater, such as sewage irrigation area, garbage disposal area, groundwater return irrigation area and large mine drainage area. In order to understand the types, distribution and diffusion conditions of pollutants, and to understand the stratification and flow direction of groundwater, background value monitoring wells and pollution control monitoring wells are usually needed. one   The layout of monitoring wells (points) with background value According to the regional hydrogeological unit and the main groundwater supply source, one or more background value monitoring wells are set up upstream of groundwater flow around the polluted area. The background value monitoring well should be far away from the urban residential area, industrial area, pesticide fertilizer application area, agricultural irrigation area and traffic main road as far as possible. two   The layout of pollution control monitoring well (point) The distribution of pollution sources and the diffusion of pollutants in underground water are the primary factors to be considered in the layout of pollution control monitoring wells. According to the local groundwater flow direction, distribution of pollution sources and the form of pollutant diffusion in underground water, pollution control monitoring wells can be arranged by combining point to surface, with the monitoring focus on the water supply water source protection area. ① Pollutants in the seepage pit, seepage well and solid waste stacking area spread in the area with high permeability of aquifer. The monitoring wells should be arranged along the direction of groundwater, and controlled by parallel and vertical monitoring lines; Pollutants in the seepage pit, seepage well and solid waste stacking area spread in the area with small permeability of aquifer, and monitoring lines can be arranged in cross shape near the pollution source for control; ② When industrial wastewater, domestic sewage and other pollutants are discharged or leaked along the river channel to spread with belt pollution, the monitoring line perpendicular to the river channel shall be set by grid distribution method according to the state of the river channel, the flow direction of groundwater and the geological conditions; The sewage in sewage irrigation area and residential area without sanitation facilities is easy to cause massive pollution to the surrounding environment in a large area, and monitoring points shall be arranged in a parallel and vertical way to the direction of groundwater; ③ The funnel area where the groundwater level drops mainly forms the lateral pollution diffusion near the mining funnel, monitoring and measuring points shall be set in the funnel center. If necessary, monitoring lines can be arranged outside according to the cross shaped or radial shape through the funnel center; ④ The pollution range of the strong diffusion area or old pollution source with good permeability may be large, and the monitoring line can be extended appropriately. Otherwise, it can only be distributed near the pollution source. (4) Determination of sampling time and frequency (1) The background value monitoring well and the regional controlled pore pressure well are sampled once a year in the dry season; (2) The pollution control monitoring well is sampled once a month and six times in the whole year; If a monitoring project is lower than one fifth of the control standard value for two consecutive years, and there is no new pollution source near the monitoring well, and the existing pollution source discharge is not increased, the project can be sampled once a year in the dry water period. Once the monitoring results are greater than one fifth of the control standard value, or there are new pollution sources near the monitoring wells or the new discharge quantity of existing pollution sources, the normal sampling frequency will be restored; (3) The groundwater monitoring logging, which is used as the centralized water supply for drinking water, is sampled once a month; (4) The sampling time of monitoring wells in the same hydrogeological unit should be concentrated as far as possible, and the date span should not be too large; (5) In case of special circumstances or pollution accidents, the sampling frequency shall be increased at any time when it may affect the quality of groundwater.
Determination of sampling time and frequency In order to make the collected water samples representative and reflect the temporal and spatial variation of water quality, it is necessary to determine the reasonable sampling time and frequency according to different water body functions, hydrological factors, pollution sources, pollutant discharge and other actual conditions (1) The monitoring sections in drinking water source areas and provincial boundary sections that need to be controlled should be monitored at least 12 times a year; (2) For the monitoring sections of large water systems, rivers, lakes and reservoirs, samples are taken once a month and monitored six times a year; The national monitoring section (or vertical line) is sampled once a month, generally from the 5th to the 10th of each month; (3) The sampling of monitoring section affected by tide is carried out in spring tide and neap tide respectively. Water samples of rising and falling tide were collected for determination. The rising tide water sample should be taken at the rising water level of the section, and the falling tide water sample should be taken at the falling water level; (4) The background section of water system is sampled once a year; (5) If a required project has not been detected for three consecutive years, and it is determined that there is no new emission near the section, but the emission of existing pollution sources has not increased, it can be sampled once a year for determination. Once it is detected, or there is a new emission source near the section, or there is a new emission from the existing pollution source, the normal sampling will be resumed; (6) In case of special natural conditions or pollution accidents, emergency monitoring scheme shall be adopted in time to increase sampling frequency; The sampling frequency should be increased in a certain period of time when the river course of local flow area is renovated, and the specific scheme should be formulated by the local administrative department of environmental protection where the renovation project is located. Result expression, quality assurance and implementation plan Many chemical, physical and biological monitoring data measured by water quality monitoring are the basic basis for describing and evaluating water environment quality and carrying out environmental management. It must be calculated and processed scientifically and expressed in the monitoring report according to the required form. Quality assurance summarizes all activities and measures to ensure the accuracy and reliability of water quality monitoring data. Quality assurance runs through the whole process of monitoring. See Chapter 2 for details. The implementation plan is the specific arrangement for the implementation of the monitoring scheme, which should be practical and feasible, so that all aspects of the work can be carried out in an orderly and coordinated manner.
Determination of sampling points: after setting the monitoring section, the sampling vertical line on the section shall be determined according to the width of the water surface (see table 3-4), and then the position and number of sampling points shall be determined according to the depth of the sampling vertical line (see table 3-5). Table 3-4 setting of sampling vertical line number Water surface width Number of vertical lines explain ≤50m One (thalweg) 1The vertical line should be set away from the pollution zone, and additional vertical line should be added to the pollution zone to be measured. 50-100m Two (near left and right bank with obvious water flow) 2If it can be proved that the water quality of the section is uniform, only the thalweg vertical line can be set.3. When the pollutant flux is to be calculated in this section, it must be set according to this table >100m Three (left, middle, right) Set the vertical line.   Table 3-5 sampling points setting on sampling vertical line Water depth Sampling points explain ≤5m A little bit up there 1The upper layer refers to the place 0.5m below the water surface and 1 / 2 of the water depth when the water depth is less than 0.5m. 2The lower layer refers to 0.5m above the river bottom. 5-10m Upper and lower two points 3Middle layer refers to 1 / 2 depth of water. >10m Upper, middle and lower levels 45 m under the ice, and 1 / 2 of the water depth when the water depth is less than 0.5 m. 5If the pollutant content is to be calculated in this section, the sampling points must be set according to this table. When there is temperature stratification in the water body of lakes and reservoirs, the number and location of sampling points can be determined according to the relationship between temperature distribution layer and sampling points (table 3-6).   Table 3-6 setting of vertical sampling points for Lake (reservoir) monitoring Water depth Stratification Sampling points explain ≤5m   One point (0.5m below water) 1Stratification refers to the stratification of lake water temperature.2. When the water depth is less than 1m, the measuring point is set at 1 / 2 of the water depth.3. When there is sufficient data to prove that the water quality of the vertical line is uniform, the number of measuring points can be reduced as appropriate. 5m-10m No stratification Two points (0.5m below water surface and 0.5m above water bottom) 5m-10m layered Three points (0.5m below water surface, 1 / 2 inclined temperature layer, 0.5m above water bottom) >10m   Except 0.5m below the water surface and 0.5m above the water bottom, 1 / 2 of each inclined layer is set   Fig. 3-2 schematic diagram of sampling point setting in intermediate temperature layer A1: in the surface temperature layer;A2: under the interlayer;A3: in the subthermal layer;A4: about 1m above the interface between sediment and water medium;h: After the location of water depth monitoring section and sampling point is determined, there should be fixed and obvious natural signs on the bank.If there are no natural markers, artificial markers should be set up, such as vertical stone columns, piling, etc.Each sampling should be strictly based on the markers, so that the collected samples are taken from the same location, so as to ensure the representativeness and comparability of the samples.