Dilution ratio. Biotest analysis - an integral method for assessing the quality of environmental objects Educational and methodological manual

Order of the Ministry of Natural Resources of Russia dated December 4, 2014 N 536 "On approval of the Criteria for classifying waste into hazard classes I - V according to the degree of negative impact on the environment" (Registered with the Ministry of Justice of Russia on December 29, 2015 N 40330)

III. Dilution ratio of aqueous extract from waste, at which there is no harmful effect on aquatic organisms

III. DILUTION RATE OF WATER EXTRACT FROM WASTE,

IN WHICH THERE IS NO HARMFUL EFFECT ON HYDROBIONS

12. Determination of the dilution factor (Cr) of an aqueous extract from waste, in which there is no harmful effect on aquatic organisms, is based on biotesting of an aqueous extract of waste - a study of the toxic effect on aquatic organisms of an aqueous extract from waste obtained using water, the properties of which are established by the biotesting method used at mass ratio of waste and water is 1:10.

13. Determination of the dilution factor of the aqueous extract from the waste, at which there is no harmful effect on aquatic organisms, is carried out according to certified measurement techniques (methods), information about which is contained in the Federal Information Fund for Ensuring the Uniformity of Measurements in accordance with the Federal Law of June 26, 2008. N 102-FZ “On ensuring the uniformity of measurements” (Collected Legislation of the Russian Federation, 2008, N 26, Art. 3021; 2011, N 30, Art. 4590, N 49, Art. 7025; 2012, N 31, Art. 4322; 2013, No. 49, Article 6339; 2014, No. 26, Article 3366).

14. When determining the dilution ratio of an aqueous extract from waste, at which there is no harmful effect on hydrobionts, at least two test objects from different systematic groups (daphnia and ciliates, ceriodaphnia and bacteria or algae) are used, for example, the mortality rate of the crustaceans Ceriodaphnia affinis is not more than 10% in 48 hours (BKR10-48), mortality of the crustaceans Ceriodaphnia dubia no more than 10% in 24 hours (BKR10-24) or mortality of the crustaceans Daphnia magna Straus no more than 10% in 96 hours (BKR10-96) and a decrease the level of chlorophyll fluorescence and a decrease in the number of cells of the algae Scenedesmus quadricauda by 20% in 72 hours (BKR20-72). The final result is taken to be the hazard class identified on the test object that showed higher sensitivity to the analyzed waste.

When studying water extracts from waste with high salt content (the content of dry residue in the studied water extract is more than 6 g/dm3), at least two test objects are used that are resistant to high salt content from different systematic groups, for example, the mortality of the crustaceans Artemia salina is no more than 10% in 48 hours (BKR10-48) and by a decrease in the level of chlorophyll fluorescence and a decrease in the number of cells of the algae Phaeodactylum tricomutum by 20% in 72 hours (BKR20-72).

Dilution is one of the main factors in wastewater treatment. Although dilution does not change the total amount of pollutant entering the water body (wastewater receiver), the neutralizing effect is very significant. Dilution has the same effect on both conservative and non-conservative substances. The dilution of wastewater in the wastewater receiver stream is caused by the mixing of contaminated streams with adjacent, cleaner streams under the influence of turbulent mixing.

In calculation practice, the following concepts are used: dilution factor n and mixing factor A. The dilution factor is a quantitative characteristic of the intensity of the process of reducing the concentration of pollutants in reservoirs or watercourses caused by mixing and dilution of wastewater in the surrounding aquatic environment.

The multiplicity of the general (total) dilution is expressed by the product:

n = n n ·n basic(2.3)

Where n n– multiplicity of initial dilution, due to more intense dilution in the initial dilution zone; n base– multiplicity of the main dilution.

When discharging wastewater into watercourses and into zones of stable unidirectional flows of reservoirs, the initial dilution is calculated according to N.N. Lapshev.

Initial dilution should be considered in the following cases:

– for pressure, concentrated and dispersive wastewater discharges at the ratio of velocities in the wastewater receiver ( V p) and in the outlet section of the wastewater outlet ( V out): V out > 4 V R;

– when the absolute value of the flow velocity in the outlet section of the wastewater outlet is more than 2 m/s (at lower speeds, the initial dilution is not calculated).

The initial dilution factor is calculated as follows:

1) The speed is located on the axis of the jet

V 0 = V p + Δ V (2.4)

where Δ V – excess of the river flow velocity over the velocity on the jet axis (set within 0.1...0.15 m/s).

2) given by the number of outlet openings of the wastewater discharge head and the flow rate in the outlet section V out (2...5 m/s), determine the diameter of the outlet section:

Where q– consumption of wastewater discharged through the wastewater outlet, m 3 /s; the diameter is rounded down in multiples of 0.05 m.

3) The parameter is calculated T(speed ratio) m = V R / V output and ratio ( V 0 /V p) – 1

4) according to the nomogram (Figure 2.1) the ratio of the diameter of the contaminated jet (spot) in the initial dilution area ( d) to the diameter of the outlet section of the wastewater outlet ( d out);

5) The diameter of the unconstrained jet in the design section is calculated

6) The ratio of the initial dilution without taking into account the restriction of the jet (when the diameter of the spot ( d) is less than the average water depth in the river ( N

(2.7)

7) The ratio of the initial dilution taking into account the restriction of the jet (when the diameter of the spot ( d) greater than the average depth of water in the river ( N) in the initial dilution zone) is determined by the formula:

where the reduction correction factor determined from Fig. 2.2).

The ratio of the main dilution at the design site is determined by the formula:

(2.9)

where is the estimated flow rate of river water in m 3 /s involved in mixing; q– wastewater flow, m 3 /s, A– mixing coefficient – a dimensionless coefficient showing what part of the wastewater receiver flow rate is mixed with wastewater in the maximum contaminated stream of the design site.

Mixing coefficient A found by the formula:

(2.10)

Where e – base of natural logarithms; L f. – distance to the design target along the fairway, m (determined according to the plan of the water body - Fig. 2.3).

Theoretically, the distance from the wastewater outlet to the complete mixing point is infinity, therefore the value of the coefficient A, equal to 1, does not occur in practice.

Meaning α found by the formula:

Where φ – river tortuosity coefficient; ξ – coefficient depending on the place of release (for onshore release ξ = 1, with fairway ξ = 1,5); D – turbulent diffusion coefficient, m/s; q – wastewater flow, m 3 /s (according to the assignment option).

Tortuosity coefficient φ determined by the formula:

Where L – length to the design site in a straight line, m (determined according to the plan of the water body - Fig. 2.3).

Table 2.1.

Roughness coefficients for open channels of watercourses

Watercourse category	Bed characteristics	Roughness coefficient
I	Rivers in very favorable conditions (clean, straight bed with free flow, without landslides or deep gullies)	0,025
II	Rivers in favorable flow conditions	0,03
III	Rivers in relatively favorable conditions, but with some rocks and algae	0,035
IV	Rivers with relatively clean channels, winding, with some irregularities in the direction of the streams, or straight, but with irregularities in the bottom topography (shoals, gullies, rocks in places), a slight increase in the amount of algae	0,04
V	The channels (of large and medium-sized rivers) are significantly clogged, winding and partially overgrown, rocky, with a restless current. Floodplains of large and medium-sized rivers, relatively developed, covered with a normal amount of vegetation (grasses, shrubs)	0,05
VI	Rapids areas of lowland rivers. Pebble-boulder riverbeds of the mountain type with an irregular surface of the water surface. Relatively overgrown, uneven, poorly developed river floodplains (ravines, bushes, trees, with the presence of creeks)	0,067
VII	Rivers and floodplains are very overgrown (with weak currents) with large, deep gullies. Boulder-type, mountain-type, riverbeds with a turbulent foamy current, with a pitted surface of the water surface (with splashes of water flying upward)	0,08
VIII	The floodplains are the same as in the previous category, but with a very irregular flow, creeks, etc. A mountain-waterfall type channel with a coarse boulder bed structure, the differences are pronounced, the foaminess is so strong that the water, having lost its transparency, has a white color, the noise of the flow dominates above all other sounds. Makes conversation difficult	0,1
IX	The characteristics of mountain rivers are approximately the same as in the previous category. Swamp-type rivers (thickets, hummocks, almost stagnant water in many places, etc.). Floodplains with very large dead spaces, with local depressions, lakes, etc.	0,133

Turbulent diffusion coefficient (for lowland rivers) D found using the formulas:

For summer time

Where: g– free fall acceleration, g = 9.81 m/s 2 ; V – average speed of the watercourse, m/s; H – average depth of the watercourse, m; p w– river bed roughness coefficient (table 2.1), S w– Chezy coefficient, m 1/2 /s, determined by the formula N.N. Pavlovsky,

where R is the hydraulic radius of the flow, m (R ≈ N); parameter y, defined as.

Determination of the hazard class of waste using biotesting

Among animals, at the cellular level of organization, daphnia have the most important indicator value. They have an advantage over other groups of protozoa (sarcodes and flagellates) because their species composition and numbers most clearly correspond to each level of saprophobicity of the environment, they are highly sensitive to changes in the external environment and have a clearly expressed reaction to these changes, they are relatively large in size and quickly multiply. Using these features of daphnia, it is possible to establish with a certain degree of accuracy the level of saprobity in the aquatic environment, without involving other indicator organisms for this purpose.

Determination of the toxicity of water and aqueous extracts from waste based on Daphnia mortality

The methodological manual includes biotesting techniques using crustaceans and algae as test objects.

The technique is based on determining changes in the survival and fertility of daphnia when exposed to toxic substances contained in the test water compared to the control.

Short-term biotesting - up to 96 hours - makes it possible to determine the acute toxic effect of water on daphnia by their survival. The survival rate is the average number of test objects that survived in the test water or in the control for a certain time. The criterion for acute toxicity is the death of 50 percent or more of daphnia over a period of time up to 96 hours in the test water, provided that in the control experiment the death does not exceed 10%.

In experiments to determine the acute toxic effect, an average lethal concentration of individual substances is established that causes the death of 50% or more test organisms (LCR) and a harmless concentration that causes the death of no more than 10% of test organisms (TBR).

Long-term biotesting—20 days or more—allows us to determine the chronic toxic effect of water on daphnia by reducing their survival and fertility. The survival rate indicator is the average number of initial female daphnia that survived during biotesting. The criterion for toxicity is a significant difference from the control in the survival rate or fertility of daphnia.

The starting material for cultivation (daphnia) is obtained in laboratories engaged in biotesting, which have a culture of the required species (Daphnia magna Straus).

Biotesting of water and aqueous extracts is carried out only on a synchronized culture of daphnia. A synchronized culture is a culture of the same age obtained from one female through acyclic parthenogenesis in the third generation. Such a culture is genetically homogeneous. The crustaceans that make it up have similar levels of resistance to toxic substances, mature at the same time and at the same time produce genetically homogeneous offspring. A synchronized culture is obtained by selecting one medium-sized female with a brood chamber filled with embryos and placing it in a 250 ml beaker filled with 200 ml of culture water. The emerging fry are transferred to a crystallizer (25 individuals per 1 dm of water) and cultivated. The resulting third generation is a synchronized culture and can be used for biotesting.

Daphnia need to be provided with a combined yeast-algae diet. Green algae of the genera Chlorella, Scenedesmus, Selenastrum are used as food.

Algae are cultivated in glass cuvettes, battery cups or flat-bottomed flasks under round-the-clock illumination with 3000 lux fluorescent lamps and constant blowing of the culture with air using microcompressors. After 7-10 days, when the color of the algae culture becomes intensely green, they are separated from the nutrient medium by centrifugation or settling in the refrigerator for 2-3 days. The precipitate is diluted twice with distilled water. The suspension is stored in the refrigerator for no more than 14 days.

To prepare yeast feed, 1 g of fresh or 0.3 g of air-dried yeast is poured into 100 ml of distilled water. After swelling, the yeast is thoroughly mixed. The resulting suspension is left to stand for 30 minutes. The missing liquid is added to the vessels with daphnia in the amount of 3 ml per 1 liter of water. The yeast solution can be stored in the refrigerator for up to two days.

Daphnia in acute experiments are fed daily, once a day, adding 1.0 cm of concentrated or twice diluted algal suspension with distilled water per 100 cm of cultivation water.

In a chronic experiment, an additional 0.1-0.2 cm of yeast suspension per 100 cm of water is added 1-2 times a week.

Wastewater samples for biotesting are taken in accordance with the instructions for sampling for wastewater analysis NVN 33-5.3.01-85; industry standards or other regulations. Natural water samples are taken in accordance with GOST 17.1.5.05-85. Soil sampling, transportation and storage are carried out in accordance with GOST 12071-84.

Biotesting of water samples is carried out no later than 6 hours after their collection. If the specified period cannot be met, the samples are stored for up to two weeks with the lid open at the bottom of the refrigerator (at +4°C). Preservation of samples using chemical preservatives is not permitted. Before biotesting, samples are filtered through filter paper with a pore size of 3.5-10 microns.

To carry out biotesting, an aqueous extract is prepared from selected samples of sewage sludge and waste; for this purpose, water used for cultivation is added to the leaching vessel, where there is a suspended air-dry mass of waste or sewage sludge with an absolute dry mass of 100 ± 1 g . Water is added in the ratio of 1000 cm3 of water per 100 g of absolutely dry mass.

The mixture should be stirred lightly on a stirrer for 7-8 hours so that the solid is suspended. It is unacceptable to crush waste particles or sediments during mixing. A magnetic stirrer is used and the stirring speed should be as low as possible to keep the material in suspension.

After mixing is completed, the solution with the sediment is left to settle for 10-12 hours. The liquid above the sediment then siphons off.

Filtration is carried out through a white ribbon filter on a Buchner funnel using a low vacuum.

The biotesting procedure is carried out no earlier than 6 hours after preparing the extract from the sludge or waste. If this is not possible, then the extract can be stored in the refrigerator for no more than 48 hours.

The water extract should have pH=7.0-8.2. If necessary, samples are neutralized. After neutralization, the samples are aerated for 10-20 minutes. Before biotesting, the sample temperature is brought to 20 ± 2C.

To determine the acute toxic effect, biotesting of the original test water or a water extract from the soil, sewage sludge, waste and several of their dilutions is carried out.

Determination of the toxicity of each sample without dilution and each dilution is carried out in three parallel series. Three parallel series with cultivation water are used as a control.

Biotesting is carried out in chemical beakers with a volume of 150-200 cm3, which are filled with 100 cm3 of test water, ten daphnia aged 6-24 hours are placed in them. The sensitivity of daphnia to toxicants depends on the age of the crustaceans. Age is determined by the size of the crustaceans and is ensured by filtering the crustaceans through a set of sieves. Daphnia are caught from cultivators in which a synchronized culture is grown. Crustaceans of the same age are placed in a separate glass after they have been filtered through a set of sieves, and then they are caught one by one with a 2 cm pipette (with a sawn and singed end) with a rubber bulb and placed in a glass with the water being tested.

Daphnia planting begins with a control series. Daphnia are placed in the test solutions, starting from large dilutions (lower concentrations of pollutants) to smaller dilutions. To work with the control series, there must be a separate net.

For each series of test water, 3 beakers are used.

Daphnia mortality in the experiment and control is recorded every hour until the end of the first day of the experiment, and then 2 times a day every day until 96 hours have passed.

Stationary individuals are considered dead if they do not begin to move within 15 seconds after gently shaking the glass.

If the death of daphnia in the control exceeds 10%, the results of the experiment are not taken into account and it must be repeated.

To determine the acute toxicity of the test waters and water extract, the percentage of daphnia dead in the test water is calculated compared to the control:

where X is the number of surviving daphnia in the control; X is the number of surviving daphnia in the tested water; A - percentage of dead daphnia in the tested water.

At A? 10%, the tested water or aqueous extract does not have an acute toxic effect (AT). At A? 50%, the tested water, aqueous extract, has an acute toxic effect (AT).

If experimentally it is not possible to establish the exact value of the dilution factor causing 50% death of daphnia within 96 hours of exposure, then to obtain the exact value of the LCR without performing additional experiments, a graphical or non-graphical determination method is used.

In the graphical method of determining LCR, probit analysis is used to obtain a linear dependence on the graph. The results of experiments to establish the acute toxic effect from the work log are entered into Table 1. The probit values are set according to Table 2. The probit values for the experimentally determined percentage of death of daphnia and the values of decimal logarithms for the studied concentrations of wastewater, water extracts from soils, and sediments are entered in Table 3 sewage, waste.

Based on the values of probits (Table 2.8) and decimal logarithms from the experimentally obtained data (Table 2.7), a graph is constructed, the values of logarithms of the percentage concentrations of the studied waters are plotted along the abscissa axis, and probits from the values of the percentage of death of daphnia are plotted along the ordinate axis. Experimental data is entered into the coordinate system, and a straight line is drawn through the points.

On the graph, parallel to the axis of logarithms of concentrations (lgС), a straight line is drawn from the point corresponding to the probit value of 5, which corresponds to 50% of the death of daphnia (from Table 2). From the point of intersection of the straight lines with the graph of the dependence of the probit value of inhibition of the test parameter on the logarithm of concentrations, the value of the logarithm of the concentrations of the studied waters, aqueous extracts corresponding to the LCR is obtained.

The obtained biotesting data is entered into a table, the recording form of which is presented in Table 2.7

Table-2.7 Form for recording the results of determining the acute toxicity of wastewater

Probit values for experimentally determined mortality of Daphnia from 0 to 99% are presented in Table 2.8

Table -2.8 Probit value

In the non-graphical method of determining the LCR, the decimal logarithm of the concentration of the wastewater under study is designated as x, and the numerical values of the death probits of daphnia are designated as y. As a result, we obtain a linear relationship:

The numerical values of the coefficients k and b are calculated using the formulas:

The resulting logarithm of the percentage concentration of the water under study (lgC) is converted into percentage concentration. The harmless dilution factor (BKR10-96) is calculated by dividing 100% by the resulting percentage concentration.

The hazard class is established by the dilution factor of the aqueous extract, at which no impact on aquatic organisms was detected in accordance with the following dilution factor ranges in accordance with Table 2.8

Table - 2.8 Indicators of the dilution factor of the aqueous extract

Results of determining the hazard class.

After conducting a series of experiments, the following data were obtained to establish the hazard class for enterprises in the cities of Saratov and Engels.

The experiment carried out on test objects of daphnia in order to establish changes in their fertility for the enterprise JSC SEMZ "Electrodetal" gave the following results, presented in table 2.9. Based on the data obtained, the calculated IFR50-96 is equal to 219.3, which corresponds to the acute toxicity of the waste, and the IFR10-96 is equal to 1466.2, the value of which lies in the range from 10000 to 1001, which corresponds to hazard class 2 in accordance with Table 2.8 of the methodology.

The experience carried out on Daphnia test objects for the enterprise OJSC Gazprommash Plant gave the following results, presented in Table 2.10. Based on the data obtained, IKR50-96 was calculated equal to 312.6, which corresponds to the acute toxicity of the waste and IKR10-96 equal to 910.7, the value of which lies in the range from 1000 to 101, which corresponds to hazard class 3 in accordance with Table 2.8 of the methodology.

The experience carried out on Daphnia test objects for the Saratov Refinery OJSC enterprise gave the following results, presented in Table 2.11. Based on the data obtained, ICR50-96 was calculated to be equal to 3.8, therefore it does not have an acute toxic effect, and BCR10-96 is equal to 13.7, the value of which lies in the range from 1 to 100, which corresponds to hazard class 4 in accordance with Table 2.8 of the methodology.

The experience carried out on Daphnia test objects for the enterprise JSC Fax-Auto gave the following results, presented in Table 2.12. Based on the data obtained, ICR50-96 was calculated to be equal to 0.95, therefore it does not have an acute toxic effect, and BCR10-96 is equal to 1.61, the value of which lies in the range from 1 to 100, which corresponds to hazard class 4 in accordance with Table 2.8 of the methodology.

The experience carried out on Daphnia test objects for the enterprise OJSC ATP-2 gave the following results, presented in Table 2.13. Based on the data obtained, ICR50-96 was calculated to be equal to 0.49, therefore it does not have an acute toxic effect, and BCR10-96 is equal to 1.001, the value of which lies in the range?1, which corresponds to hazard class 5 in accordance with Table 2.8 of the methodology.

The experience carried out on Daphnia test objects for the enterprise OJSC SGATP-6 gave the following results, presented in Table 2.14. Based on the data obtained, ICR50-96 was calculated to be equal to 0.199, therefore it does not have an acute toxic effect, and BCR10-96 is equal to 0.409, the value of which lies in the range?1, which corresponds to hazard class 5 in accordance with Table 2.8 of the methodology.

Given the known composition of contaminants and wastewater flow rates, the required dilution rate mainly depends on the geometric dimensions of the reservoir, the speed and direction of movement of water in it.

When wastewater is released into water bodies, the concentration of pollutants decreases due to the mixing of wastewater with the aquatic environment. This process is quantitatively characterized by the dilution factor:

Where C in– concentration of pollutants in wastewater released by a reservoir;

From 0 And WITH– concentration of pollutants in the reservoir before and after the release of wastewater.

However, the formula is inconvenient to use in practice.

For reservoirs with directional movement (rivers), it is recommended to determine it using the formula:

(2.2)

Where Q V, Q 0– volumetric flow rate of wastewater and reservoir, respectively

γ – displacement coefficient, showing what part of the flow rate Q is involved in the displacement.

In the initial section, the dilution factor is 1; because

γ = 0 ; That = 1.

Concentration of pollutants in a reservoir at any time:

(2.3)

Where τ = V*(Q 0 + ∑Q V – Q V) the period of complete exchange of water in a reservoir;

V– volume of the reservoir;

Q V– loss of water flow (for example, due to evaporation);

The concentration of pollutants for the most polluted stream of a river flow without specifying its location, shape, size is determined using the Florov-Rodziller method:

C max = C + (C 0 – C)* (2.4)

Where α – coefficient characterizing the hydraulic conditions of displacement;

x– coordinate in the direction of speed and flow, the origin of which is (x=0) the place of wastewater discharge.

The displacement area in the reservoir is conventionally divided into three zones (Fig. 2.1).

Fig.2.1. Scheme of distribution of wastewater in a reservoir:

Zone I – the concentration of pollutants decreases due to displacement caused by the difference in the speed of the wastewater stream and the reservoir;

Zone II – area of turbulent mixing;

III – zone – the area of complete mixing, when the speeds of the wastewater jets and the reservoir are completely equalized.

To estimate the smallest dilution ratio for low-strength reservoirs, another method is used, the so-called N.N. Lapshev method. It is used to calculate the dilution ratio for distributed and concentrated wastewater discharges with the flow rate from outlet devices W 0≥ 2 m/s:

……………………………………(2.5)

Where A– coefficient characterizing the uniformity of output; for concentrated release A = I, and for distributed release:

(2.6)

I– distance between release devices; d 0– diameter of the outlet; R– coefficient characterizing the degree of flow of a reservoir (lake, reservoir);

S– a parameter determined by the relative depth of the reservoir.

For a reservoir where the movement of water is determined by the flow of discharged wastewater:

Where I n– distance from the wastewater discharge point to the shore in the direction of the wastewater flow velocity, m; F 0– total area of the outlet openings, m3.

For a body of water where the current is determined by the wind, the coefficient is:

, (2.8)

Where Wn– flow speed, m/s;

W 0– speed of wastewater at the outlet of the head, m/s.

Calculation of the dilution ratio of wastewater in rivers

Wastewater dilution is the process of reducing the concentration of pollutants resulting from the mixing of wastewater with the aquatic environment. The intensity of the process is quantitatively characterized by the dilution factor (n), which for reservoirs with directed water movement (river flow) is determined by the formula:

, (2.9)

Where Q V And Q 0– respectively, the volumetric flow rates of part of the water in the reservoir and waste water;

γ – mixing coefficient, showing the proportion of water in the reservoir participating in the mixing process:

Where L– length of the channel from the wastewater discharge point to the water consumption point, m;

α – coefficient depending on the hydraulic mixing conditions – coefficient:

Where ξ – coefficient taking into account the location of the wastewater outlet (for onshore outlet ξ = 1, for channel outlet ξ = 1.5);

δ – channel tortuosity coefficient;

D– coefficient of turbulent diffusion,

, (2.12)

Where q– free fall acceleration, m/s 2 ;

H– average channel depth, m;

W a n– average speed of water flow in a reservoir, m/s;

S w– Chezy coefficient, (1/m*s);

M g- Boussinesq coefficient, 1/m*s (for water M g = 22.3 (1/m*s)).

Calculation of the dilution ratio of wastewater in winding channels

The method discussed above does not take into account the transverse components of water flow velocity in winding channels, which can significantly speed up the process of mixing wastewater. This is explained by the fact that such currents take place from areas with high concentrations of pollutants to areas with lower concentrations and vice versa.

The lowest total dilution for concentrated wastewater discharge is determined by the formula:

, (2.13)

Where β – coefficient taking into account the relative parameters of the channel B/N And R/B(Fig.2.2);

IN– river width, m;

N– depth, m;

R– radius of curvature of the drain, m;

L– distance from the outlet to the design section, m;

The dilution factor is calculated in the following order:

1. The curved section is divided into m sections with the same values of the relative parameters B/H and R/H.

2. Determine the lengths L 1, L2, …, L m and according to the graph (Fig. 2.2) they find the values β 1, β 2, …, β m. In this case, changing the sign of curvature does not change the calculation method.

3. Dilution ratio in the first section, and then the consumption of a mixture of domestic and river water at a distance L 1:

Q 1 = n 1 *Q

4. Dilution ratio, consumption of wastewater mixture in subsequent sections:

Q i = n 1 *n 2 *…*n i *Q 0 .

5. General dilution ratio:

n = n 1 *n 2 *…*n m .

Calculation of the dilution ratio of wastewater in reservoirs and lakes

The conditions for mixing wastewater with water from reservoirs and lakes differ significantly from the conditions of mixing in rivers.

The degree of pollution of water bodies decreases intensively at a short distance from the place of wastewater discharge, but complete mixing of wastewater with the volume of water in the lake occurs at very large distances from the place of discharge.

Calculation of the dilution factor is carried out for scattering and concentrated discharges at the wastewater outflow rate W 0

When calculating the VAT for local wastewater discharge, it is recommended to use the semi-empirical method used in established practice when calculating the MPC standard (“Methodology for calculating the MPC of substances in water bodies with wastewater”, 1990).

The basic equation for calculating the PDS is:

Q,q-calculated water flows in water bodies and wastewater,

The concentration of pollutants of the same type in wastewater and in the water body up to the point of wastewater discharge,

– mixing coefficient,

– is accepted as the maximum permissible concentration at the design site for a given water body.

The determination of the standard discharge of pollutants depends on the mixing factor or the more commonly used concept of dilution factor.

The dilution factor is related to the mixing coefficient by the following approximate relationship:

The wastewater dilution process occurs in 2 stages: initial and main dilution.

The total dilution factor is presented as the product:

-multiplicity of the main dilution.

1.2. Determination of the initial dilution factor.

The initial decrease in the concentration of pollutants is associated with the injection (penetration) of waste liquid into the inflow stream of the watercourse.

It is recommended to calculate the initial dilution when releasing wastewater into water bodies based on the ratio of the speeds in it (river speed and release speed). Or at absolute speeds of jet outflow from the outlet. At lower speeds, the initial dilution is not calculated.

The initial dilution factor is calculated in accordance with the method of N.N. Lapsheva “Calculations of wastewater discharge” Moscow, Stroyizdat, 1978.

Initial data for calculation.

A channel concentrated outlet is installed in the river, discharging wastewater with a maximum flow rate of q=17.4 m 3 /h=0.00483 m 3 /sec.

Estimated minimum average monthly river flow 95% probability Q=0.3 m 3 /sec.

Average river flow speed.

Average depth H av = 0.48 m.

The speed of jet outflow from the outlet, while

We accept =0.1 m

Corrected outflow velocity from the water outlet

Initial dilution factor

Relative diameter of the jet in the design section

Definition of parameter m

The relative diameter of the jet in the design section will be determined using a nomogram.

The initial dilution ends at the section where the jet cannot add flow. According to experimental studies, this cross section should be conditionally accepted where the speed on the axis of the jet is 10-15 cm/sec higher than the speed of the river flow.

Initial dilution factor

Due to the district's restriction of fluid access, the dilution rate will decrease.

To quantify this phenomenon, it is necessary to calculate the ratio, where

– depth of the watercourse,

Unconstrained jet diameter

1.3 Determination of the main dilution factor.

Outside the initial dilution area, mixing is carried out due to the diffusion of the impurity. To calculate the main dilution of wastewater, we will use the methodology of N.D. Rodziller “Instructions for methods for calculating the mixing and dilution of wastewater in rivers, lakes and reservoirs”, Moscow 1977. This technique can be used to relate wastewater flow to water flow in a water body.

Initial data.

Estimated flow rate in the watercourse in the background section Q = 0.3 m 3 /sec

Estimated wastewater flow rate in the outlet q=0.00483 m 3 /sec

Average speed of the watercourse at the calculated flow rate V c р =0.11 m/sec

Average depth of the watercourse at the estimated flow rate N av = 0.48 m

Distance from the outlet to the control point in a straight line L p =500 m

Distance from the outlet to the control point along the forward channel L f =540 m

1) Determination of the mixing coefficient