Categories of ponds and their distinctive features

head ponds designed to accumulate water with its subsequent supply to the system of industrial ponds. The location of the head pond is chosen so that the water horizon in it is higher than the horizon of all production ponds. This makes it possible to provide gravity water supply to the ponds. The size of the head ponds is determined depending on the size of the production ponds.

spawning ponds intended for fish breeding and must meet optimal conditions for spawning, development of eggs and maintenance of larvae. The water supply of the ponds is necessarily independent. The ponds must descend quickly. Spawning ponds should not be used for other purposes, so as not to lead to wetting and disappearance of meadow vegetation at the bottom, as well as for reasons of disease prevention.

fry ponds designed for growing larvae transplanted from spawning ponds or coming from the incubation shop. For a better development of the forage base, it is recommended to plow up the bed of fry ponds and apply organic fertilizers.

nursery ponds serve for rearing of the yearlings. Larvae transplanted from spawning or fry ponds are kept in rearing ponds until the end of the growing season, then the juveniles are transplanted into wintering ponds. The water supply of nursery ponds should be independent, with the installation of gravel and sand filters on the water supply system, as well as the installation of fish catchers on the water supply.

Wintering ponds intended for winter maintenance fish. They are located close to the water supply source, which makes it possible to reduce the possibility of water cooling during the period when it enters the ponds and when the water supply to the wintering ponds is interrupted. To create optimal wintering conditions for fish, it is necessary to maintain optimal depths at the rate of at least 1 m of non-freezing water layer, flow rate of about 15 l / s per hectare. Water supply sources should have a high oxygen content, low oxidizability, no pollution.

Table 3

Characteristics of the main categories of fish farm ponds
(Privezentsev, Vlasov, 2004)

Indicators	Pond categories
spawning	fry	nursery	wintering	foraging	uterine	pre-spawning	cage ponds	quarantine
1. Pond size, ha	0,05-0,1	0,5-1,0	10-15	0,5-1,0	50-100	1-2	0,001-0,002	0,05-0,1	0,1-0,5
2. Depth, m:
at the spillway	1-1,2	1,2-1,5	1,2-1,5	1-1,2	3-4	1,2-1,5	1-1,2	1,5	1,5
average	0,5	0,5-0,8	1,0-1,2	1,5-2,5	1,3-1,5	1,2-1,5	0,9-1	1,3	1,0
3. Terms of filling, days:
Desirable	0,2		10-15	0,3-0,5	15-20	0,5	0,002	0,2	0,3
Permissible	0,3						0,003	0,3	0,5
4. Terms of descent, days:
Desirable	0,1	0,3-0,5	3-5	0,5-1,0	5-10	0,3	0,001	0,2	0,2
Permissible	0,2	0,8				0,5	0,002	0,3	0,3
5. Flow rate per 1 hectare, l/s		0,5-1	1-1,5		0,5-1	0,5-1

feeding ponds intended for the cultivation of marketable fish. These are the largest ponds in the economy, the fish productivity of which depends on their size. On small fish ponds, where it is easier to carry out a complex of various intensification measures, a higher yield of fish products is obtained. Great depths are unfavorable for feeding and growth of carp, which is associated with more low temperatures water and lower oxygen content in the bottom layers. For best performance, the ponds must be well planned so that they are completely drained when lowered.

Mother Ponds are intended for summer and winter maintenance of producers and replacement young animals. The size and number of ponds depend on the number of producers.

quarantine ponds are intended for temporary keeping of sick fish or producers imported from other farms. They are made necessarily flowing, but at the outflow the water (if a sick fish sits in the pond) is disinfected by chlorination. Such ponds are located at the end of the farm at a distance from other categories of farm ponds.

cage ponds are used in autumn to store live fish, and in spring - for temporary overexposure of yearlings until they are sold. Cages are also used in spring to keep spawners until they are planted for spawning and for repair material until they are planted in mother ponds.

Pre-spawning ponds intended for keeping spawners before landing for natural spawning in spawning ponds and for keeping after pituitary injections. Ponds should be located in close proximity to the hatchery, have good flow and, if necessary, quickly descend.

In a farm with a three-year turnover, there is an additional category of ponds - rearing ponds of the second order, which do not differ in structure from feeding ponds with a two-year turnover.

Table 4

Approximate ratio of individual categories of ponds, (%)

The percentage ratio of the areas of ponds of certain categories depends on the type, system, turnover, capacity of the farm, the adopted technology for breeding and rearing fish, the degree of intensification, fish breeding and technological standards. The areas of mother and quarantine ponds are set depending on the percentage of ponds of the main categories.

The ratio of ponds of the main categories, shown in Table 4, is approximate and varies depending on the characteristics of the technology, the level of intensification of a particular pond farm.

Questions for self-control:

1. What are the differences between full-system and non-full-system pond farms?

2. What is turnover?

3. Name the main categories of ponds of full-system farms with a 2-year and a 3-year turnover of commercial fish rearing.

3. List the main advantages and disadvantages of one-, two- and three-year turnover.

4. Designate the purpose and distinctive features of each category of ponds in a full-system and non-full-system carp farm.

Practice #6
"Requirements for the quality of water used for fish farming"

Objective: To study the requirements for water quality in fish ponds.

Exercise: 1. Familiarize yourself with the requirements for water quality in fish ponds.

2. Write to workbook the main parameters characterizing the quality of water.

3. Mark the indicators of the maximum permissible concentrations of harmful substances in the water of fish ponds.

The quality of the water used in technological process, should provide an optimal regime for growing fish, which not only excludes the occurrence of mortality phenomena, but contributes to obtaining maximum fish productivity.

The main indicators characterizing the quality of water used for fish farming purposes are:

Temperature;

Transparency and color;

Hydrogen index (pH);

organic matter;

Biogenic elements;

Salt composition;

Microbiological indicators.

Temperature water: water is characterized by low thermal conductivity, due to which there is a layering effect (in summer, the water is warm at the surface, cold at the bottom, winter period The water at the surface is colder than at the bottom. Depending on their relationship to water temperature, fish are divided into warm-water (so, for carp, the optimum temperature is 23-28ºС) and cold-water ( optimum temperature water for trout - 14-18ºС).

Transparency and color: it is noted that the closer the color of water to blue, the more transparent it is, the yellower the color of water, the lower its transparency. The less transparent the water, the better developed the zooplankton in it.

Hydrogen index (pH): Neutral pH value is most favorable for fish. With significant shifts in pH to the acidic or alkaline side, the intensity of fish respiration decreases. Valid values The pH depends on the type of fish. Thus, pike tolerates pH fluctuations within the range of 4.8-8.0, trout - 4.5-9.5, carp - 4.3-10.8 units.

Gas composition: with an increase in water temperature and an increase in its salinity, the solubility of gases deteriorates. With a decrease in the level of oxygen dissolved in water, the consumption of feed by fish worsens. Highest value fish have oxygen and carbon dioxide. The optimal content of dissolved oxygen for carp is 5 mg/l, for trout - 9-11 mg/l, carbon dioxide content - 10-20 mg/l.

organic matter: present in water in dissolved and suspended form, replenished due to photosynthesis of phytoplankton, chemosynthesis of some types of bacteria. Enters water bodies precipitation and industrial waste.

Biogenic elements: these include phosphates, nitrates, trace elements that ensure the development of phyto- and zooplankton. The productivity of water bodies depends on the level of their development.

Salinity: the total value of the amount of salts dissolved in water. According to this indicator, 3 groups of water bodies are distinguished: fresh - salt content up to 1 mg / l, brackish - 1-15 mg / l, salty - 15-40 mg / l.

In fish farms, water quality is also assessed by the indicator total hardness. The higher the hardness, the higher the osmotic pressure to which the fish are sensitive.

General requirements and norms for the quality of water supplied to fish farms depend on the category of ponds and type of farms. The main norms characterizing water quality are shown in tables 5,6 and 7.

Why do we need fisheries water quality standards. Water quality standards for water bodies of fishery importance. Classification, purpose and features of fishery reservoirs. Quality standards aquatic environment for similar water bodies. MPC of some hazardous substances. Principles of calculation of water standards for objects of fishery water use. Fishery water quality standards help to maintain the proper condition of reservoirs intended for rearing fish. The water quality standards for water bodies of fishery importance are stipulated in the orders of the federal agency for fisheries.

Classification of reservoirs of fishery importance

According to the regulatory document "Rules for the protection of surface waters", all surface water objects are conventionally divided into the following categories:

• objects of economic and drinking and cultural purposes;
• objects of fishery purpose.

We will consider the requirements for the last type of water bodies in our article. Reservoirs of fishery water use are divided into certain subspecies:

• Reservoirs of the first category are objects that are intended for breeding and preserving valuable species of fish. Such reservoirs are used for representatives of the aquatic fauna, which are very demanding on the concentration of oxygen in the aquatic environment.
• Reservoirs of the second category are fishery facilities that are used for other purposes.

If in such water bodies wastewater is discharged, then the indicators of the quality of the aquatic environment in the reservoir in a place located below the entry point of the wastewater are necessarily evaluated. These indicators must comply with the requirements of sanitary standards for each type of water use.

Fisheries water quality standards

The quality standards for the aquatic environment for fishery facilities include the following indicators:

1. General characteristics of the components and qualities of the aquatic environment. Each type of water use object has its own standards.
2. List of maximum permissible concentrations of substances present in the aquatic environment. MPCs for each substance may differ for each water use facility.

Despite the fact that the requirements for the concentration of certain substances differ for each water use object, there are also general standards that describe the composition and quality of the aquatic environment. These include: the concentration of impurities, the percentage of suspended solids, color, taste qualities, smell, acidity, degree of mineralization, oxygen concentration, toxicity.

The maximum permissible concentrations of certain substances describe the permitted content of this substance in the aquatic environment, at which the water will be absolutely safe for the inhabitants. In this case, both the complete absence of a substance and its concentration below or equal to the agreed norm can be considered the norm.

It is very important to regulate the concentrations of toxic substances, since some of them are able to slow down the natural processes of self-purification of a reservoir, namely, the biochemical oxidation of organic matter. All this can lead to a poor state of the aquatic environment: lack of oxygen, decay processes, and an increase in the concentration of hydrogen sulfide. That is why the maximum permissible concentrations of substances are normalized according to the general sanitary sign of harmfulness.

Water quality standards for water bodies of fishery significance normalize the concentration of hazardous substances:

• Oil products. When their concentration in the reservoir is within 0.1-0.2 mg/l, the fish acquires a specific smell and taste of petroleum products.
• The concentration of substances hazardous to health is normalized according to toxicological characteristics.
• The concentration of Cu ions in 10 mg/l can have a toxic effect on the body. The same substance in a volume of 5 mg/l can disrupt the processes of self-purification of the reservoir, and the content of this substance in a volume of 1 mg/l worsens the taste of the liquid. As a result, for fishery reservoirs, this indicator is normalized according to toxicological characteristics and is allowed to be equal to no more than 10 mg/l.
• Also, in regulatory documents, such an indicator as LPV is used - a limiting sign of harmfulness. It indicates the lowest maximum permissible concentration of a substance.
• The concentration of arsenic in fishery reservoirs is 0.05 mg/l. And according to European standards, the concentration of this substance can be in the range of 0.2 mg / l.

Principles for calculating water standards for fishery water use facilities

1. The principle of "zero strategy" states that the slightest change in the natural aquatic environment must be considered unacceptable.
2. Any standards must be established in accordance with technological capabilities aimed at reducing the degree of pollution of the reservoir, as well as in accordance with the control of their concentration in the aquatic environment.
3. The maximum allowable concentration of pollutants must be normalized so that the costs of maintaining their normal concentration do not exceed the costs in the event of uncontrolled pollution of the reservoir.

If you need to perform an analysis of the aquatic environment of a reservoir to assess the concentration of various substances, you can order such a test in our laboratory. To do this, you just need to call the specified numbers.

The protection of water bodies from pollution is carried out in accordance with the Sanitary Rules and Norms for the Protection of Surface Waters from Pollution (1988). The rules include general requirements for water users regarding the discharge of wastewater into water bodies. The rules establish two categories of water bodies:

I - reservoirs for drinking and cultural purposes;

II - reservoirs for fishery purposes.

The composition and properties of water in water bodies of the first type must comply with the standards in sites located in watercourses at a distance of at least one kilometer upstream of the nearest water use point, and in stagnant water bodies - within a radius of at least one kilometer from the water use point. The composition and properties of water in type II reservoirs must comply with the standards at the place of wastewater discharge with a scattering outlet (in the presence of currents), and in the absence of a scattering outlet - no further than 500 m from the outlet.

The rules establish normalized values ​​for the following parameters of water in reservoirs: the content of floating impurities and suspended particles, smell, taste, color and temperature of water, pH value, composition and concentration of mineral impurities and oxygen dissolved in water, biological water demand for oxygen, composition and maximum allowable concentration (MPC) of toxic and harmful substances and pathogenic bacteria. Maximum allowable concentration - the concentration of a harmful (toxic) substance in the water of a reservoir, which, with daily exposure for a long time to the human body, does not cause any pathological changes and diseases, including in subsequent generations, detectable modern methods research and diagnostics, and also does not violate the biological optimum in the reservoir.

Harmful and toxic substances are diverse in composition, and therefore they are normalized according to the principle of a limiting hazard index (LHI), which is understood as the most likely adverse effect of a given substance. For reservoirs of the first type, three types of LPW are used: sanitary-toxicological, general sanitary and organoleptic; for reservoirs of the second type, two more types are additionally used: toxicological and fishery.

The sanitary condition of the reservoir meets the requirements of the norms when the inequality is fulfilled

for each of the three (for water bodies of the second type - for each of the five) groups of harmful substances, the MPCs of which are established, respectively, for the sanitary and toxicological HPS, the general sanitary HPS, the organoleptic HPS, and for fishery reservoirs - also for the toxicological HPS and the fishery HPS. Here n is the number of harmful substances in the reservoir, related, for example, to the "sanitary-toxicological" group of harmful substances; C, - concentration of the z-th substance from this group of harmful substances; m is the number of a group of harmful substances, for example, m = 1 - for the “sanitary-toxicological” group of harmful substances, m = 2 - for the “general sanitary” group of harmful substances, etc. - five groups in total. At the same time, the background concentrations of Cf of harmful substances contained in the water of the reservoir before the discharge of wastewater should be taken into account. With the predominance of one harmful substance with a concentration of C in the group of harmful substances of a given LP, the requirement C + Cf must be met<ПДК.

MPCs have been established for more than 400 harmful basic substances in drinking and cultural water bodies, as well as more than 100 harmful basic substances in fishery water bodies. In table. 2 shows the MPC of some substances in the water of reservoirs.

table 2

Maximum Permissible Concentrations of Certain Harmful Substances in Water Bodies

Substance
	Sanitary-T toxicological		Toxicological
	Organoleptic		Fishery
Gasoline, kerosene
	Sanitary and toxicological		Toxicological
	Organoleptic
	general sanitary
	Sanitary and toxicological
	Organoleptic

Rationing of water quality and categories of water bodies in accordance with legislative acts and regulatory documents. The main normalized indicators of surface water bodies.

The standardization of water quality in reservoirs is carried out in accordance with the Sanitary Rules and Norms SanPiN 2.1.5.980-00, "Hygienic requirements for the protection of surface waters", which establishes hygienic standards for the composition and properties of water in water bodies for two categories of water use. 1 category- this is the use of water bodies or their sections as a source of drinking and domestic water use, as well as for water supply to food industry enterprises. 2 category- this is the use of water bodies or their areas for recreational water use.

The main normalized indicators are weighted substances-increase in concentration (when sewage is discharged, the concentration of suspended substances in the control section does not increase compared to natural conditions by more than: 1 category = 0.25 mg / dm 3, 2 k. \u003d 0.75 mg / dm 3); floating impurities (films of oil products, oils, fats, etc. cannot be found on the surface of the water); coloring (not to be found in the column: 1k. = 20 cm, 2k. = 10 cm); odors (water is not for acquiring odors with an intensity of more than 2 points); temperature - temperature increase (flight water temperature as a result of wastewater discharge does not rise by more than 3 C ▫ compared to the average monthly water temperature of the hottest month of the year over the past 10 years); pH value (pH=6, 5-8.5); water mineralization - the concentration of all mineral salts when sediment remains (no more than 1000 mg / dm 3, including chlorides 350 mg / dm 3, sulfates 500 mg / dm 3); dissolved oxygen - for the oxidation of organic. in-in (not d / be less than 4 mg / dm 3 in any period of the year in a sample taken before 12 noon); BOD 5 - biochemical oxygen demand is the amount of O 2 in mg / dm 3, which is necessary for the oxidation of biochemically oxidized organics with the help of microorganisms (proteins, fats, sugars, hydrocarbons) in within 5 days (do not d / exceed at a temperature of 20 C▫: 1k. \u003d 2 mgO 2 / dm 3, 2k. \u003d 4 mgO 2 / dm3); COD - chemical consumption of O 2 is the content of O 2 in mg / dm 3 of water, necessary for the oxidation of all organics in-in, including organics oxidized by biochemical means (do not exceed: 1k. = 15 mgO 2 / dm 3, 2k. = 30 mgO 2 /dm3); chemical in-va (maximum concentration limit or ODU-approximately permissible level); causative agents of intestinal infections (water should not be d / contain); various bacteria; the total volumetric activity of radionuclides in their joint presence.

MPC(mg / l) - this is the maximum concentration of water in water, in which, with daily intake into the body of a person, throughout life, it does not have a direct or indirect effect on the health of the population. and the next generations, and does not worsen the hygiene of the water use conditions, mg / dm 3. Approximate allowable level (ODE, mg / l) - temporary hygienic standard, developed on the basis of calculation and express experimental methods for predicting toxicity and used only at the stage of preventive sanitary supervision of enterprises being designed or under construction, reconstructed treatment facilities

Organolytic properties: - color; - smells; - taste (it is not standardized).

MPC is established according to 3 hazard criteria (LPV): 1-sanitary-toxicological (s-t) (reflects the effect of a substance on human health); 2-organoleptic (org.) (if a harmful substance gives the water a smell, taste, coloring); 3- general sanitary (general) (the effect of a given chemical substance on the processes of water self-purification, i.e. on the community of microorganisms, mainly from organic substances).

MPC is set according to all harm criteria as MPC, the smallest of the threshold values ​​is selected, i.e. the limiting sign of harmfulness is characterized by the smallest harmless end in the water.

MPDs are set for each source of discharge and each pollutant. MPD (g / h) is the mass of a substance or microorganisms in wastewater, the maximum allowable for discharge with the established regime at a given point of a water body per unit

LECTURE 10. Rationing, regulation, control of water quality in reservoirs

10.1 Rationing and regulation of water quality in reservoirs

The protection of water bodies from pollution is carried out in accordance with the Sanitary Rules and Norms for the Protection of Surface Waters from Pollution (1988). The rules include general requirements for water users regarding the discharge of wastewater into water bodies. The rules establish two categories of reservoirs: 1 - reservoirs for drinking and cultural purposes; 2 - reservoirs for fishery purposes. The composition and properties of water in water bodies of the first type must comply with the standards in sites located in watercourses at a distance of at least one kilometer upstream of the nearest water use point, and in stagnant water bodies - within a radius of at least one kilometer from the water use point. The composition and properties of water in type II reservoirs must comply with the standards at the place of wastewater discharge with a dispersive outlet (in the presence of currents), and in the absence of a dispersive outlet - no further than 500 m from the outlet.

The rules establish normalized values ​​for the following water parameters of reservoirs: the content of floating impurities and suspended particles, smell, taste, color and temperature of water, pH value, composition and concentration of mineral impurities and oxygen dissolved in water, biological water demand for oxygen, composition and maximum allowable concentration (MPC) of toxic and harmful substances and pathogenic bacteria. The maximum permissible concentration is understood as the concentration of a harmful (toxic) substance in the water of a reservoir, which, when exposed daily for a long time to the human body, does not cause any pathological changes and diseases, including in subsequent generations, detected by modern methods of research and diagnostics, and also does not violate the biological optimum in the reservoir.

Harmful and toxic substances are diverse in composition, and therefore they are normalized according to the principle of a limiting hazard index (LH), which is understood as the most likely adverse effect of a given substance. For reservoirs of the first type, three types of LPW are used: sanitary-toxicological, general sanitary and organoleptic; for reservoirs of the second type, two more types are used: toxicological and fisheries.

The sanitary condition of the reservoir meets the requirements of the norms when the inequality is fulfilled

C i n ∑ i=1 MPC i m

for each of the three (for water bodies of the second type - for each of five) groups of harmful substances, the MPCs of which are established, respectively, for the sanitary-toxicological HPS, the general sanitary HPS, the organoleptic HPS, and for fishery reservoirs - also for the toxicological HPS and the fishery HPS . Here n is the number of harmful substances in the reservoir, belonging, let's say, to the "sanitary-toxicological" group of harmful substances; C i is the concentration of the i-th substance from this group of harmful substances; m is the number of the group of harmful substances, for example, m = 1 - for the "sanitary-toxicological" group of harmful substances, m = 2 - for the "general sanitary" group of harmful substances, etc. – only five groups. In this case, the background concentrations C f of harmful substances contained in the water of the reservoir before the discharge of wastewater should be taken into account. With the predominance of one harmful substance with a concentration of C in the group of harmful substances of a given DS, the requirement must be met:

C + C f ≤ MAC, (10.2)

MPCs have been established for more than 640 harmful basic substances in reservoirs for drinking and cultural purposes, as well as more than 150 harmful basic substances in reservoirs for fisheries. Table 10.1 shows the MPC of some substances in the water of reservoirs.

For wastewater itself, MPCs are not standardized, but the maximum allowable quantities of discharge of harmful impurities, MPD, are determined. Therefore, the minimum required degree of wastewater treatment before discharging them into a reservoir is determined by the state of the reservoir, namely, the background concentrations of harmful substances in the reservoir, the water flow of the reservoir, etc., that is, the ability of the reservoir to dilute harmful impurities.

It is forbidden to discharge wastewater into water bodies if it is possible to use more rational technology, waterless processes and systems for re- and recycling water supply - re-use or permanent (repeated) use of the same water in the process; if the effluents contain valuable waste that can be disposed of; if the effluents contain raw materials, reagents and production products in quantities exceeding technological losses; if wastewater contains substances for which MPCs have not been established.

The reset mode can be one-time, periodic, continuous with variable flow, random. At the same time, it is necessary to take into account that the water flow in the reservoir (the debit of the river) changes both by season and by year. In any case, the requirements of condition (10.2) must be satisfied.

Table 10.1

Maximum allowable concentrations of certain harmful substances in water

yomax

MAC, g/m 3 0.500 0.001 0.050 0.005 0.010 0.010 0.050 0.000 MAC, g/m 3 0.500 0.001 0.100 0.010 1.000 1.000 0.100 0.100 Substance Benzene Phenols Gasoline, kerosene Сd 2+ Cu 2+ Zn 2+ Cyanides Cr 6 + DP Toxicological Fishery The same Toxicological The same - « - - « - -

Sanitary

toxicological

Organoleptic

Sanitary

toxicological

Organoleptic

general sanitary

Sanitary

toxicological

Organoleptic

Of great importance is the method of wastewater discharge. With concentrated discharges, the mixing of effluents with the water of the reservoir is minimal, and the contaminated jet can have a large extent in the reservoir. The most effective use of scattering outlets in the depth (at the bottom) of the reservoir in the form of perforated pipes.

In accordance with the above, one of the tasks of regulating the quality of water in reservoirs is the task of determining the permissible composition of wastewater, that is, the maximum content of a harmful substance (substances) in wastewater, which, after discharge, will not yet exceed the concentration of a harmful substance in the waters of a reservoir over the MPC of this harmful substances.

The balance equation of the dissolved impurity when it is discharged into a watercourse (river), taking into account the initial dilution in the outlet section, has the form:

C st \u003d n o (10.3)

Here C cm , C r.s, C f are the concentrations of impurities in wastewater before discharge into the reservoir, in the design section and the background concentration of impurities, respectively, mg/kg; n o and n r.s - the ratio of dilution of wastewater in the outlet section (initial dilution) and in the calculated section, respectively.

Initial dilution of wastewater at their outlet

where Q o \u003d LHV is the part of the drain flowing over the scattering outlet, which, for example, has the form of a perforated pipe laid on the bottom, m 3 / s; q - wastewater consumption, m 3 / s; L is the length of the dissipating outlet (perforated pipe), m; H, V are the average depth and flow velocity above the outlet, m and m/s.

After substituting (10.4) into (10.3), we get that

For LHV >> q

In the course of the drain, the wastewater jet expands (due to diffusion, turbulent and molecular), as a result of which the wastewater mixes with the water in the stream, the dilution ratio of the harmful impurity increases and its concentration in the wastewater jet, more precisely, now already mixed water decreases. Ultimately, the section (section) of the jet will expand to the section of the watercourse. In this place of the watercourse (where the polluted jet site coincided with the watercourse site), the maximum possible dilution of the harmful impurity for this watercourse is achieved. Depending on the values ​​of the initial dilution ratio, width, speed, tortuosity and other characteristics of the watercourse, the concentration of harmful impurities (C d.c.) can reach the value of its MPC in different sections of the polluted jet. The sooner this happens, the smaller the area (volume) of the watercourse will be polluted with a harmful impurity above the norm (higher than the MPC). It is clear that the most suitable variant is when the condition (10.2) is already provided at the outlet itself and, thus, the size of the polluted section of the watercourse will be reduced to zero. Recall that this variant corresponds to the condition of discharge of effluents into the watercourse of the second type. Normative dilution to MPC at the outlet site is also required for watercourses of the first type, if the outlet is carried out within the locality. This option can be achieved by increasing the length of the perforated outlet pipe. In the limit, blocking the entire drain with a discharge pipe and thus including the entire flow of the watercourse in the process of diluting effluents, taking into account that for the outlet section n r.s = 1, and also putting C = MPC in (10.5), we obtain:

where B and H are the effective width and depth of the watercourse; respectively, Q = BHV is the flow rate of the watercourse.

Equation (10.7) means that with the maximum use of the dilution capacity of the watercourse (watercourse flow), the maximum possible concentration of a harmful substance in the discharged wastewater can be assumed equal to

If for the purpose of diluting wastewater it is possible to use only a part of the water flow of the watercourse, for example, 0.2Q, then the requirements for wastewater treatment from this harmful substance increase, and the maximum allowable concentration of harmfulness in wastewater must be reduced by a factor of 5: In this case, the value of qC cm , equal in the first case

and in the second should be considered as limiting

allowable discharge (MPD) of this hazard into the watercourse, g/s. If these MPC values ​​(Q MPC and 0.2Q MPC, g/s) are exceeded, the concentration of a harmful substance in the waters of the watercourse will exceed the MPC. In the first case (MPD = Q MPC), turbulent (and molecular) diffusion will no longer reduce the concentration of harmfulness along the course of the watercourse, since the initial dilution site coincides with the site of the entire watercourse - there is nowhere for the polluted water jet to diffuse. In the second case, along the course of the watercourse, there will be a dilution of effluents and a decrease in the concentration of harmfulness in the water of the reservoir, and at a certain distance S from the outlet, the concentration of a harmful substance may decrease to MPC and below. But even in this case, a certain section of the watercourse will be polluted above the norm, that is, above the MPC.

In the general case, the distance from the outlet point to the calculated point, that is, to the point with a given value of the dilution ratio, n r.s or - which is actually the same - with a given concentration of a harmful impurity, for example, equal to its MPC, will be equal to

where А = 0.9…2.0 is the coefficient of proportionality, depending on the category of the channel and the average annual water flow of the watercourse; B is the width of the watercourse, m; х is the width of the part of the channel in which discharge is not performed (the pipe does not cover the entire width of the channel), m; f- tortuosity coefficient of the channel: the ratio of the distance between the sections along the fairway to the distance along the straight line; Re = V H / D is the Reynolds diffusion criterion.

The expansion of the polluted jet along the watercourse occurs mainly due to turbulent diffusion, its coefficient

where g is the free fall acceleration, m 2 /s; M is a function of the Chezy coefficient for water. M \u003d 22.3 m 0.5 / s; C w - Shezy coefficient, C w \u003d 40 ... 44 m 0.5 / s.

After potentiation (10.8), the value of n r.c is obtained explicitly

Substituting the expression for n r.s. in (10.6) and setting С r.s. = MPC, we get:

Equation (10.11) means: if at an initial dilution determined by the values ​​L, H, V, and with known characteristics of the watercourse j, A, B, x, R ∂ , C f, it is necessary that at a distance S from the outlet of wastewater the concentration of the harmful substance be at the MPC level or less, then the concentration of the harmful substance in the effluent before discharge should not exceed the value C cm calculated according to (10.11). Multiplying both parts of (10.11) by q, we come to the same condition, but already through the maximum allowable reset C cm q = MPD:

From common solution(10.12) follows the same result obtained above on the basis of simple considerations. In fact, let us assume that the problem is being solved: what can be the maximum (maximum permissible) discharge of wastewater into a watercourse so that already at the place of discharge (S = 0) the concentration of a harmful substance is equal to the MPC, and only a fifth of the flow is used for initial dilution watercourse (river debit), i.e. LHV = 0.2 Q.

Since for S = 0 n r.c = 1, from (10.12) we obtain:

MPD = 0.2 MPC.

On the principles outlined, in general, the regulation of water quality in watercourses is based when suspended, organic substances are discharged into them, as well as water heated in the cooling systems of enterprises.

The conditions for mixing wastewater with the water of lakes and reservoirs differ significantly from the conditions for their mixing in watercourses - rivers and canals. In particular, complete mixing of effluents and waters of a reservoir is achieved at significantly greater distances from the place of release than in watercourses. Methods for calculating the dilution of effluents in reservoirs and lakes are given in the monograph by N.N. Lapsheva Calculations of wastewater outlets. - M.: Stroyizdat, 1977. - 223 p.

10.2 Methods and instruments for monitoring water quality in reservoirs

Water quality control of reservoirs is carried out by periodic sampling and analysis of water samples from surface reservoirs: at least once a month. The number of samples and the places of their selection are determined in accordance with the hydrological and sanitary characteristics of the reservoir. At the same time, sampling is mandatory directly at the water intake site and at a distance of 1 km upstream for rivers and canals; for lakes and reservoirs - at a distance of 1 km from the water intake at two diametrically located points. Along with the analysis of water samples, laboratories use automatic water quality control stations that can simultaneously measure up to 10 or more water quality indicators. Thus, domestic mobile automatic water quality control stations measure the concentration of oxygen dissolved in water (up to 0.025 kg / m 3), electrical conductivity of water (from 10-4 to 10-2 Ohm / cm), pH (from 4 to 10), temperature (from 0 to 40°C), water level (from 0 to 12m). The content of suspended solids (from 0 to 2 kg / m 3). Table 10.2 shows the qualitative characteristics of some domestic standard systems for quality control of surface and waste water.

At the treatment facilities of enterprises, they control the composition of the source and treated wastewater, as well as control the efficiency of the treatment facilities. Control, as a rule, is carried out once every 10 days.

Wastewater samples are taken into clean borosilicate glass or polyethylene containers. The analysis is carried out no later than 12 hours after sampling. For wastewater, organoleptic indicators, pH, suspended solids content, chemical oxygen demand (COD), the amount of oxygen dissolved in water, biochemical oxygen demand (BOD), concentrations of harmful substances for which there are normalized MPC values ​​are measured.

Table 10.2

Qualitative characteristics of some domestic standard systems for quality control of surface and waste water

When determining coarse impurities in wastewater, the mass concentration of mechanical impurities and the fractional composition of particles are measured. For this, special filter elements and measurement of the mass of the “dry” sediment are used. Also, the speeds of ascent (deposition) of mechanical impurities are periodically determined, which is important when debugging treatment facilities.

The COD value characterizes the content of reducing agents in water that react with strong oxidizing agents and is expressed as the amount of oxygen required to oxidize all the reducing agents contained in the water. Wastewater samples are oxidized with a solution of potassium bichromate in sulfuric acid. The actual measurement of COD is carried out either by arbitration methods, performed with great accuracy over a long period of time, and by accelerated methods used for daily analyzes in order to control the operation of treatment facilities or the state of water in a reservoir with a stable flow rate and composition of water.

The concentration of dissolved oxygen is measured after wastewater treatment before they are discharged into a water body. This is necessary to assess the corrosive properties of effluents and to determine the BOD. The most commonly used Winkler iodometric method is used to detect dissolved oxygen with concentrations greater than 0.0002 kg / m 3, lower concentrations are measured by colorimetric methods based on the change in the color intensity of the compounds formed as a result of the reaction between special dyes and sewage. For automatic measurement of the concentration of dissolved oxygen, devices EG - 152 - 003 are used with measurement limits of 0 ... 0.1 kg / m 3, "Oximeter" with measurement limits of 0 ... 0.01 and 0.01 ... 0, 02 kg/m 3 .

BOD - the amount of oxygen (in milligrams) required for oxidation under aerobic conditions, as a result of the biological processes occurring in the water of organic substances contained in 1 liter of waste water, is determined by analyzing the change in the amount of dissolved oxygen over time at 20 ° C. The most commonly used five-day biochemical oxygen demand - BOD 5.

The measurement of the concentration of harmful substances for which MPCs are established is carried out at various stages of purification, including before the release of water into the reservoir.