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10
Laboratory work №3
ANTHROPOGENIC WATER POLLUTION AND ITS CLEARING METHODS
1 Work purpose
Conducting of water pollution monitoring. To acquaint with the sewage cleaning methods. Acquisition of skills concerning methodical calculations.
2 Key positions
2.1 Rational use and guard of water resources
Problem of the proper amount and water quality providing is one of most essential and has a global value. Even B.C. Aristotle pointed out necessity of rational clean water consumption and separation it from that which is utilized for economic necessities.
The state of 2/3 water sources by water quality does not meet normative requirements. Because of low-quality water use morbidity of people grew in 4-5 times. Politicians more frequently talk about possibility of ecological wars for water in the row of countries.
Water is utilized for machines and mechanisms cooling, technological processes functioning and constituent of produced products. Water consumption specific norms for one ton production of finished products make, : cast iron − 160...200; steel − 150; rolled metal − 10...15; nickel − 4000; copper − 500; synthetic rubber − 2000…3500; paper − 400...800; plastics − 500...1000.
Thermal and atomic power-stations consume a large water volume. It is spent 1,2... 1,6 of water on 1 million kW powers of the thermal annually, and atomic station − in 1,5...2 times greater. There is a permanent water rotation, which provides water evaporation and transpiration by plants, by precipitation in nature. Water cycle speed is characterized by such information, years: World ocean − 2500 (mixing − 63); underground water − 400; lakes water − 17; bogs water − 5. In rivers water cycle takes place for few days, and in the organism of person − for few hours.
In the circulation process water transports warmth, dissolves and carries natural elements, destroys and converts lithosphere, takes part in meteorological and hydrological processes, is the environment of water organism existence which product considerable part of oxygen. If necessary terms are provided amount and quality of water recommence. However development of industry, transport, agriculture, urbanization, resulted in natural reservoirs are not able to self-purify, that’s why artificial mechanisms are needed for water clearing.
Reservoirs are characterized by mirror area, length, depth, volume and water expense, flow speed and water level, its temperature, harmful conditions duration and water cycle periods conditions (freezing-up, flow absence and others), water cycle indexes, soils filter properties.
Depending on water pollution measure objects are admissible, moderate, high and extraordinarily high pollution degrees (table 3.1). It should be taken into account during water consumption organization.
2.2 Water consumption and water use
Water consumption is the water objects use for population and subjects of economic activity necessities satisfaction.
In accordance with State Standard 17.1.1.03-86. water consumption is classified for such signs:
Depending on the water consumption purposes water-supply sources are divided into two categories.
To the I category belong water objects, utilized as centralized or uncentralized household water-supply sources, and also for the water-supply of food-processing industry enterprises.
To the II category belong water objects for cultural and welfare purposes and which are located within the settlements limits.
Requirements according to water composition and properties are regulated depending on the water objects category.
There is water use, which can be irretrievable, repeated, circulating in the presence of water consumption. With the purpose of the water rational use the water consumption norms are inculcated on one inhabitant and on conditional product unit, which is characteristic for enterprises of each branch of industry. In limited water resources districts the waterworks balance, which foresees water use comparison with the potential resources of water pools, should be adhered.
Table 3.1 – Qualitative indexes of water objects I and II pollutions
|
Pollution level |
Organoleptic mode |
Toxico-logical mode |
Sanitary mode |
Bacterio-logical mode |
Pollution index |
|||
|
Smell, flavor, marks |
, excess degree |
, excess degree |
Dissolved oxygen, |
Quantity of lactose- positive colibacillus in 1 |
||||
|
I |
II |
|||||||
|
Admissible |
2 |
1 |
1 |
3 |
6 |
4 |
less than |
0 |
|
Moderate |
3 |
4 |
3 |
6 |
8 |
3 |
1 |
|
|
High |
4 |
8 |
10 |
8 |
10 |
2 |
2 |
|
|
Extraordi-narily high |
>4 |
>8 |
>10 |
>8 |
>10 |
1 |
more than |
3 |
Note: − maximum possible substances concentrations, established according to harmfulness organoleptic sign; − maximum possible substances concentrations, established according to harmfulness toxicological sign; − biological oxygen consumption for 20 days for water use reservoirs I and II categories.
On character of water use the water-supply systems are divided into straight current, successive, circulating, ijected.
Straight current water is utilized once during the production process, whereupon threw off in reservoirs or sewage system.
Consistently used water is consumed in a few technological processes.
Circulating water is used repeatedly in production, with its periodic or continuous clearing. On the well equipped enterprises an index of circulating and successive water-supply degree is 30...90 %. Thus it should be taken into account that buildings of water circulating systems is tenfold cheaper, than corresponding power purifying buildings.
Areas of sanitary guard, in which the special mode of waters guard is set from chemical matters, harmful biological organisms and sewage pollution , settle down round water supply point or another water-supply resource. The area of sanitary guard is divided into two or three subareas.
First subarea − high security subarea, sometimes with the special guard. This area is planted around the forest planting, here are forbidden to build, to pasture cattle, any type of activities, which can entail water pollution.
Second subarea has limitation on the types of activities, which cause pollution and capable to penetrate to water supply point; here are forbidden to dispose storehouses of fuels and lubricants (FL), stock-raising farms, apply fertilizers.
Third subarea is preventive. The types of activities, which draw water pollution, are also limited here.
General water use of enterprise is determined after a formula:
,
where , − specific norms of water use on economic and production necessities;
− amount of shift workers;
− amount of production users;
− amount of workers groups and equipment.
Level of water resources use in industry, and also technical equipment of buildings and in applied sewage clearing technologies is characterized by such coefficients:
1) use of circulating water in general volume of water use
,
where − water volume, used accordingly in a turn, which perches from a source, and arrived with raw material;
,
where , − water volume, which accordingly thow off to the reservoir, and utillized repeatedly;
,
overflow-pipe
,
where − water volume which arrives from other users;
5) normative loading of pollution reservoir by sewages
,
where − clearing coefficient;
− coefficient of the normal loading of pollution reservoir by sewages;
− mass of pollutions, which are subject to extraction from sewages,
;
− mass of pollutions, which is admitted to throw off in reservoirs (GDS);
− mass of contaminating matters in sewages.
Water-supply is carried out from conduits which are divided into drinkable and technical. From city water conduit water can be utilized for economic-drinkable necessities and fires extinguishing. Assumed to satisfy up to 15 % water production requirements from city water conduit, other requirements should be covered by technical conduits.
2.3 Sources of water pollution
Matters which draw violation of water quality are named pollutants. Next to physical and chemical pollutants, thermal and microbial water pollution takes a place.
Flow waters of boiler rooms contain softeners, products of corrosion. A presence of butters, oil on the water surface worsens exchange processes, reduces maintenance of oxygen in water which results the fishes death. 1L of oils contaminates to 12 of water reservoir surface. If maintenance of mineral oil makes up over 200 , the zoological equilibrium of water objects is violated. Synthetic superficial active matters perniciously influence on phytoplankton development.
Lead, mercury, cadmium, nickel, zinc, manganese, getting in water, do it toxic, that results not only in death of zooplankton but also harms health of people. Sewages of galvanic areas by maintenance of metals exceed in 2000...5000 one times. Pesticides, which get in water at processing of forest plants, gardens, vegetable gardens, negatively influence on living organisms and people which consume such water. building of bridges and other buildings on the rivers inflicts large harm to water objects.
Economic-domestic flows result to biological water pollution what can cause intestinal-gastric diseases (cholera, typhus) and diseases of liver (hepatitis). Too dangerous are the water states of points of linen and overalls sanitary treatment, flows from hospitals, domestic flows, which getting in water, can cause various intestinal worm diseases (ascaridiasis, echinococcus and others like that). Organic contaminations often result to the not supposed processes − joint oxygen in water, death of living organisms and phytoplankton. Surpluses of phosphorus and nitrogen in water result to its flowering and violation of biological equilibrium in reservoirs (table 3.2).
Table 3.2 − Consequences of muddy water use by a person
|
Character of water use |
Pollutant |
Deseases |
|
Biological |
||
|
Drinking and eating |
Pathogenic bacteria |
Cholera, dysentery, typhoid, gastroenteritis, leptospirosis, rabbit-fever |
|
Virus |
Infectious hepatitis |
|
|
Parasites |
Amoeba dysentery, drankunkulez, helminthiasis, strongyloidiasis |
|
|
Washing and laundering in water |
Parasites |
Shestosomiaziz, dermatitis, strongyloidiasis |
|
Dwelling or stay is near water |
Through insect vector |
Malaria, yellow fever, sleeping-sickness, filariasis |
|
Chemical |
||
|
Drinking and eating |
Nitrates |
Metahewettite |
|
Connections of fluorine |
Endemic |
|
|
Arsenic |
Intoxication |
|
|
Selenium |
Selenomethionine, intoxication |
|
|
Lead |
Intoxication |
|
|
Polycyclic aromatic carbohydrates |
Cancer |
|
|
Too much soft water |
Atherosclerosis, hypertension |
|
|
Chromium |
Kashin-Bek disease |
|
|
Nickel |
Allergy of skin, destruction of eye cornea |
|
|
Copper |
Defeat of the nervous system |
|
|
Phenol |
Poisoning |
Radio-active matters, getting in water, predetermine its ionization which unfavorably influences on development of living organisms. Moreover, phytoplankton and fishes is able to master plenty of radio-active matters and accumulate them in the organism. A consumption of such fish is dangerous for people health.
Water objects with the possible pollution degree can be utilized for all types of water use without limitations, with the moderate pollution degree are utilized only for cultural and welfare water use, with the high pollution degree are dangerous for any kind of water consumption. Water objecta with the extraordinarily high pollution degree are useless for all kinds of water consumption.
A degree of ecological safety of water objects can be expressed by a formula
where − actual indexes value of water quality;
− rationed indexes values of water quality.
2.4 Control of water quality
Water characterized by composition and properties which determine its convenience for the concrete types of water consumption. The estimation of water quality is given on signs, elected and rationed depending on the type of water consumption. One of water indexes is considered as limiting. For limiting sign is elected those which is characterized the least harmless concentration of matter in water. The total numerical estimation of water quality is given on an index which is the aggregate of basic indexes by the types of water consumption. Quality, composition and properties of water in reservoirs is regulated by hygienic requirements and sanitary norms.
For the hygienic evaluation of water such indexes are used (табл.3.З):
Table 3.3 − Hygienic requirements in relation to composition and properties of water
|
Indexes of composition and properties of water |
Category of water consumption |
|
|
for an economic-drinkable water-supply |
for bathing, sport and rest of population |
|
|
Hangings up matters |
Maintenance of hangings up matters must not be increased more than on: |
|
|
0,25 |
0,75 |
|
|
Floating admixtures |
On a surface of reservoir must not be floating tapes, the spots of mineral butters and accumulations of other admixtures |
|
|
Smells |
Water must not acquire unusual its smells by intensity an over 1 mark |
|
|
Color |
Must not appear in a column |
|
|
20 cm |
10 cm |
|
|
Temperature |
Summer temperature of water as a result of lowering of sewages must not rise more than on 3°С comparatively with average monthly temperature |
|
|
Hydrogen index |
6,5 |
8,5 |
|
Mineral composition |
Must not exceed by the dry remain of 1000 , in the that number of chlorides − 350 , sulfates are 500 |
|
|
Soluble oxygen |
Must not be less than after 4 of any period of the year in a test, taken at 12 o'clock of day |
|
|
Exciters of diseases |
Water must not contain the exciters of diseases |
Such indexes are utilized for the sanitary evaluation of water as:
• maximum possible concentrations of matters in water;
• orientation possible levels of matters in water (OPL );
• limiting the signs of harmfulness (sanitation-toxicological, pantosanitary, organoleptic with decoding of its properties: smell, influence on a color, formation of suds and tape, infusion of taste).
Chemical matters in water are divided into four classes of danger: I class − extraordinarily dangerous; II class − high-dangerous; III − dangerous; IV class − reasonably dangerous.
Ascription harmful matters to the class of danger depends on their toxicity, shaped-charge, capability to cause remote effects, the type of limiting index of harmfulness (табл.3.4).
Table 3.4 − Maximum possible concentrations of harmful matters in water of water objects household, cultural and welfare water use
|
Name of matters |
Class of dangerous |
Maximum possible concentration mg/l |
|
Ammonia (by nitrogen) |
III |
2,0 |
|
Active chlorine |
III |
Absents |
|
Acetone |
III |
2,2 |
|
Benzol |
II |
0,5 |
|
Cadmium |
II |
0,001 |
|
Cobalt |
II |
0,1 |
|
Manganese |
III |
0,1 |
|
Copper |
III |
1,0 |
|
Oil products |
IV |
0,1 |
|
Nitrates |
III |
45,0 |
|
Nitrites |
II |
3,0 |
|
Mercury |
III |
0,0005 |
|
Lead |
II |
0,03 |
|
Turpentine |
IV |
0,2 |
|
Phenol |
IV |
0,001 |
|
Chrome |
III |
0,05 |
|
Zinc |
III |
1,0 |
Except of state control, the state of water is controlled by enterprises which utilize water and throw down flows to the reservoirs. For this purpose posts, equipped a necessary apparatus for conducting of analyses, are created on enterprises at factory or special laboratories.
During conducting of control of waters state and flows physical, chemical, biological and organoleptic methods are utilized.
Physical methods are utilized for determination of transparency, lees, amount of hangings-up particles and conductivity of water and flows. Amount of hangings-up particles is determined by diaphragm and paper filters through which skipped test of volume 100...500 ml. Transparency, lees are determined by devices or by organoleptic comparison of specimens.
Chemical methods are utilized for determination of acidity, alkali of metals, salts, organic and synthetic matters in water.
A bacterial analysis is executed by the special methods in the laboratories of the sanitary epidemiology stations. Control of muddiness by a help of bacteria − biotesting deserves on attention. Some bacteria at appearances of pollutions begin to shine. The larger toxic matters in water, the bacteria shine stronger.
2.5 Methods of clearing of flow waters
Prevention of pollution of water objects by sewages can be provided with organizational and technical arrangements.
Organizational arrangements are taken to prevention of sewage disposal to the reservoirs without their clearing. Technical arrangements foresee clearing of sewages by different methods: repeated use of sewages for technical necessities and watering, creation of the circulating and closed systems of water use, perfection of technological processes on enterprises in the direction of decreasing of pollution coming in the flows, transition to zero-emission technologies, decreasing of territory pollution by oil products which with sewages can get to the reservoirs.
Clearing of sewages on enterprises can be carried out by one of such schemes:
The methods of clearing of muddy industrial waters can be combined in such groups: the mechanical, physical, physical-mechanical, chemical, physical-chemical, biological, complex (fig.3.1.)
Figure 3.1 – Classification of methods of waters flow clearing
Mechanical methods of clearing are used for purging of flows from hard and oily contaminations. The mechanical clearing is carried out by one of such methods:
Choice of scheme of water clearing from hangings-up particles and oil products depends on a kind and amount of pollutios, necessary degree of cleaning.
The physical-mechanical methods of water and flows clearing are based on flotation, membranous methods of clearing, anisotropic filter.
Flotation is a process of molecular adhesion of particles of pollutions to the surface of division of two phases (water − air, water − hard matter). Clearing process of SPAR, oil products, fibred materials by flotation consists of formation of the system of "particle of pollution − bubbles of air", which emerge on a surface and utilized. On principle of the action of the flotation settings are classified by such method:
Back osmosis (hyper filtration) is a process of filtration of sewages through semipermeable membranes under pressure. By the concentration of salts of 2...5 g/l there must be pressure to 1 MPa, and by the concentrations of salts 10...30 g/l − about 10 MPa.
Ultrafiltration is a membranous process of solutions division osmotic pressure of which is small. It is used for purging of sewages from high molecular matters, hangings-up particles and colloids.
An electro-dialysis is a process of separation of ions of salts in a membranous vehicle which is carried out under act of direct electric current. An electro-dialysis is used for demineralization of sewages. A basic equipment is electrodialysis apparatuses, that consist of cation and anion membranes.
Chemical clearing is utilized as an independent method or as previous method before the physical-chemical and biological clearing. It is utilized for the decline of corrosive activity of sewages, deleting from it heavy metals, clearing of galvanic areas flows, for oxidization of sulphuretted hydrogen and organic matters, for disinfection and discolouring of water.
Neutralization is used for flows ablution of galvanic, etching and other manufactures, where acids and alkali is used. Neutralization is carried out by mixing of sour sewages with alkalis, adding to sewages reagents (lime, carbonates of calcium and magnesium, ammonia and others like that) or filtration through neutralizing materials (lime, dolomite, magnesite, chalk, limestone and others like that).
An amount of reagent is for neutralization of sewages
where − a coefficient of supply of reagent
− mass of active constituent in sewage;
− volume of sewages;
− expense of reagent for neutralization of active matters;
− concentration of acid and alkali.
Oxidation is used for disinfecting of sewages from toxic admixtures (copper, zinc, sulphuretted hydrogen, sulfides), and also from organic compounds. Oxidants are a chlorine, ozone, oxygen, chloride of lime, to the hypochlorite of calcium and others like that.
Let’s consider physical-chemical methods.
Coagulation is a process of connection of small particles of pollutants in greater by coagulators. Coagulating ions for positively charged particles are anions, and for negatively charged are cations. Coagulators are lime milk, salts of aluminum, iron, magnesium, zinc, sulfur-sour calcium, carbon dioxide and others like that. Coagulating ability of salts of trivalent metals is in ten one times higher, than bivalent, and in thousand one times more than univalent.
Flocculation is a process of aggregation of small particles of pollutants in water due to formation of bridges between them and the molecules of fluctuons. Fluctuons are active silicic acid, ethers, starch, cellulose, synthetic organic polymers (polyacrylamide, polyoxyethylene, polyacrylate, polyethylenamine and others like that).
Coagulates and fluctuons are simultaneously used for illumination of water is, for example sulfur-sour aluminum and polyacrylamide PPA. Coagulation and flocculation are carried out in the special capacities and chambers.
Electro-coagulation − process of enlargement of particles of pollutants by the action of direct electric current is used at water clearing.
Sorption is a process of absorption of pollutions by hard and liquid sorbents (by an absorbent carbon, ash, small coke, peat, silica gel, active clay and others like that). Adsorption properties of sorbents depend on the structure and size of pore, division by sizes, nature of creation. Activity of sorbents is characterized by mass of pollutions which are taken in on unit of their volume or the mass (). Devices for an exception from sewages or solutions according to this method are maked as filters.
Three types of sorption processes of sewages clearing are distinguished: absorption, adsorption, chemical adsorption.
At absorption absorption of pollutions is carried out by all mass (volume) of the absorbed matter.
At adsorption absorption of pollutants takes a place only by the surface of adsorbent due to molecular forces of two bodies which co-operate.
At chemical adsorption absorption of pollutants by the sorbents takes a place with creation on the surface of division of new component or phase.
A choice of sorbent is determined by character and properties of pollutions. The process of flows clearing is carried out by the different kinds of sorbents in the special columns, filled with sorbents.
Extraction is an exception from sewages valuable matters by extragens, which must have such characteristics: high extragenic ability, selectivity, small solubility in water, to have closeness, separated from the closeness of water, small specific warmth of evaporation, small heat capacity, to be explosion-proof and untoxic, to have a small cost.
Extracting of matters from sewages is carried out one of methods: cross-flow, stepwise-antisudorific, uninterruptedly-antisudorific. Volume of extragen, essential for extraction,
,
where − specific gravity of extragen for one extraction;
− amount of extractions;
− volume of sewages, liable extraction.
This method is utilized for an exception from sewages phenol.
An ionic exchange is based on an exception from sewages valuable admixtures of chrome, zinc, copper, PAR due to an exchange ions between admixtures and ion exchangers (ion-exchange resins) on the surface of division of phases "solution − resin". By the sign of charge ion exchangers are divided into cationites and anionites, which nave sour and alkaline characteristics accordingly. Ion exchangers can be natural and synthetic. Natural ion exchangers by type of aluminum silicate, hydrates and salts of polyvalent metals, ion exchangers from coal and cellulose and various synthetic ion-exchange resins are practically used.
Basic property of ion exchangers is their taking-in ability − exchange capacity (an amount of gram-equivalents in flow water which is taken in by 1 of ion exchanger to the complete satiation).
After mechanical, chemical and physical-chemical methods of cleaning there can be various viruses and bacteria in sewages (dysenteric bacteria, choleric vibrio, exciters of typhoid, virus of poliomyelitis, virus of hepatitis, cytopathogenic virus, adenovirus, viruses which entai the disease of eyes). That is why with the purpose of prevention of diseases sewages before the repeated use for domestic necessities are liable to the biological cleaning.
Water sterilization is carried out by heating, chlorinating, ozonization, processing by ultraviolet rays, bioprocessing, electrolysis of silver, when an anode is a silver electrode, and a cathode is coal. The ions of silver have a bactericidal action. For sterilization of 20 it is needed to withdraw from the anode 1 g of silver.
The second method of electrolysis treatment of water consists of adding to water kitchen salt which at admission of current is laid out, exuding a free chlorine.
Biological clearing is carried out in biofilters, in aerotanks, in oxidizing channels, in biotsnks, in aerotanks with fillers.
Biological clearing can be carried out and in natural terms on sewage farms, fields of filtration, in biological reservoirs.
Depending on microorganisms which undertake participating in destruction of organic matters, aerobic (oxidative) and anaerobic (renewed) biological clearing of sewages is distinguished.
In production conditions complex methods of clearing which are based on mechanical, chemical, physical-chemical, biological methods and devices for the exception of pollutants has often to be utilized.
1. Basic chemical and physical properties of water.
2. What is a difference between distilled and drinkable waters?
3. What necessities is water utilized on?
4. Sources of pollution of water.
5. Component indexes of water quality.
6. What matters are most dangerous for water (for MPC)?
7. Methods of sewages clearing.
8. How does hydraulic cyclone work?
9. What is aerotank and biofilter?
1. For successful implementation and defence of laboratory work it is needed to learn the proper literature by a student.
2. To draw the charts of the systems of water clearing.
3. To prepare to the discussion on a theme : "Water is basis of life".
5 Laboratory task
1. To familiarize with a construction and principle of action of the systems of water clearing.
2. To familiarize with an equipment (PEOM) on a workplace.
3. To do classification of reasons of pollution and matters-pollutants of water.
4. To familiarize with a structure and principle of action of the various systems of water clearing. To choose two most optimum systems and do comparison (point 2 home task).
5. On the basis of information of department to conduct the calculations of term of clearing of water area of the Black sea from oil products.
6. To calculate water use and water losses of telecommunication enterprises (from data of department).
6 Maintenance of report
Report must contain