Transcript local cleaning industrial cleaning

Lecture № 4
SOURCES OF SOLID WASTE:
Wastewater.
Gas emissions
The main sources of waste water
•
•
•
•
•
•
•
•
•
industry
enterprises of household purpose;
large livestock facilities;
large agricultural complexes;
waste of the deposits mining;
mines and quarries water;
processing and alloy products;
discharges of water and rail transport;
primary flax processing waste, etc.
Composition
and sources of
Состав и происхождение
wastewater
сточных
вод
Types of
wastewater
ATMOSPHERIC
(storm)
Domestic or
municipal
The qualitative
composition
solids
petroleum
products,
fertilizers
organic matter
(60%),
Suspended
substanses
colloids
minerals (40%),
microorganisms
and bacteria
INDUSTRIAL
(depend on
enterprises)
Phase
Composition
solids
Mineral oil and
petroleum products,
inorganic acids and
their salts,
alkali, surfactants
heavy metal ions
Solutions of
organic
compounds
Ionic solutions
Types of wastewater pollution
• Mechanical - high content of mechanical impurities, mainly for
surface water;
• Chemical - toxic and non-toxic organic and inorganic (mineral)
substances: acids, bases, salts (arsenic, lead, cadmium, mercury,
chromium, copper, fluoride), hydrocarbons of various structures and
their derivatives - more than 1 million substances
• Bacterial and biological - the presence of organic matter in the
water (300 - 380 Mt. / year), surfactants, nutrients, a variety of
pathogenic microorganisms, fungi and small algae.
• Radioactive - the presence of radioactive substances in surface
water or groundwater;
• Heat - heated water of thermal and nuclear ES, industrial
wastewater
Industrial wastewater
• formed as a result of water use in various industrial
processes and depend on the enterprise
The main (foreground) pollutants:
• mechanical suspension (sand, scale, metal shavings,
dust, fluxes, cotton fiber, etc.);
• mineral oils and other petroleum products;
• inorganic acids and their salts;
• alkali;
• surface-active agents (surfactants);
• inorganic salts of heavy metals.
Atmospheric sewage or runoff
• formed from runoff of the rain and
snowmelt from an area directly into the
water bodies or sewage system.
Composition varied:
• solids (sand, stones, chips, dust, soot,
crop residues, etc.)
• petroleum products, fertilizers, etc.
Particularity - low concentrations of
pollutants (except HD)
Domestic wastewater or municipal
wastewater
• formed in the process of human life,
Have a relatively constant composition:
• contain about 60% of organic matter,
• about 40% of minerals,
• predominant types of microorganisms:
Escherichia coli, Salmonella, Staphylococcus,
Streptococcus, Enterococcus, Clostridium,
Enteroviruses
The content of organic substances in industrial
wastewater
Pollutants
Amount
in the world's stock
Mt. / year
Oil products
26,563
Phenols
0,460
Waste of synthetic fibers
5,500
Plant fossils
0,170
In total
33,273
Chemical contaminants of
industrial effluents
•
•
•
•
•
biologically labile organic compounds;
low toxic inorganic salts;
oil and oil products;
biogenic compounds;
substances with specific toxic properties,
including heavy metals;
• biologically hardly decomposed (or
nondecomposed) organic synthetic compounds.
The most dangerous and most widespread
types of chemical contaminants
1. Heavy metals (mercury, lead, cadmium, zinc, copper, arsenic,
chromium, nickel, cobalt, manganese, antimony, tin, bismuth) persistent chemical contaminants have got cumulative effect of the
specific toxic properties
Heavy metals
+
ENVIRONMENT
COMPONENTS
Connectivity
conditions:
t, nature of the metal,
pH, ionic forms
Complexes
Synergistic
mixtures
Hydrated ions
Oxyhydrates
Ion pairs
The most dangerous and most widespread
types of chemical contaminants
2.Oil and petroleum products, metalworking
fluids coolant - the main chemical contaminants
in the land waters, waters of seas and oceans, 6.1
million tons annually
Danger: they have an ability to form stable colloidal
systems like micelles
Na+
Na+
dipole
emulsifier
R-CH2-COO)+Н-
Oil
globule
Na+
Na+
Modern methods of sewage treatment against
industrial pollution
Wastewater treatment - destruction or removal of the
hazardous substances.
Destructive methods: the destruction of contaminants or
transformation into non-toxic products and the removal of
sediments in the insoluble form
Regenerative methods: based on extraction and
utilization of impurities.
Wastewater treatment can be considered as complex,
multi-stage manufacturing process cause it:
• uses raw materials (waste water)
• has finished products (purified water)
• has waste products (precipitation).
Modern methods of sewage treatment
(according to the mechanism of action)
Biological: filtering
fields, biological ponds,
aeration, methane tanks,
aerotanks, biofilters,
Sewage treatment
Mechanical: settling, filtering,
centrifugation, filtration,
microfiltration, cleaning in
hydrocyclones
Physical: magnetic,
ultrasonic, Electro
treatment, ionizing
radiation
Physicochemical: coagulation,
floatation, adsorption, ion exchange,
extraction, distillation, freezing,
electrodialysis, reverse osmosis
Chemical: oxidation (chlorination,
ozonation, liquid-phase and vapor-phase
oxidation), reduction, neutralization,
precipitation, complexation
Mechanical methods
Removes mechanical impurities (coarsely
dispersed particles), depending on the size:
• by grilles, screens, sand traps, septic tanks,
manure traps of different designs;
• surface pollution – by oil traps, petrole traps,
sumps, etc.
• allows to select up to 60-75% of insoluble
impurities from the municipal sewage, and from
industry sewage - up to 95%
Chemical (reagent) methods
Purpose - precipitation in the form of
insoluble substances:
Processes: oxidation, reduction,
neutralization
Advantages:
allow to achieve the efficiency up to 95% of
soluble and 25% of insoluble impurities
Physicochemical methods
Advantages:
• remove fine particles and dissolved
inorganic impurities;
• organic matter and hardly oxidizable
substances are broken down
• Apply: electrocoagulation, sorption,
extraction, ion exchange, electrofloatation,
galvanic coagulation
Floatation (flocculation)
• Used to treat wastewater from the rough and
fine impurities and condensation of suspensions
with fine phase.
• Principle: The formation of particle-bubble
complex, bubbles floating and removing of the
foam layer containing impurities from the water
surface.
• Advantages: remove fine and colloidal
impurities with the help of coagulants and
flocculants.
Reverse osmosis (hyperfiltration)
• the process of the solution separating by
filtration through a membrane: pore diameter of
about 1 nm pass through water molecules but is
impermeable or semi-permeable to hydrated salt
ions or undissociated molecules
Advantages:
• selectivity of the membranes;
• efficiency - up to 99%;
• provides clean water that can be returned to the
water recirculation system
Ion exchange
•
Apply: for deep purification of industrial water from
heavy metal ions (desalting) and for local systems of
metals recovering;
• Advantages: in some cases can return considerable
pert of the water into the work cycle;
• Ion exchange materials (resins): insoluble
polyelectrolytes react (exchange) with the ions of the
solution:
R’H + Na+  R’Na + H+; R’’OH + Cl-  R’’Cl + OH- ,
where R’ and R’’ - solid organic matrix (polystyrene) with
cation and anion, respectively; Na+, H+, Cl-, OH- exchanging mobile ions.
The scheme of an ion exchange plant
№ 1, 2, 3 - valves, 4 - tank with regenerating solution
Wastewater
Regenerating
solution
Grille and
resin layer
1
2
4
3
Pump
Working
solution
Adsorption method
• the most affordable and effective method
of deep cleaning (post-treatment) of the
dissolved organic matter.
• Applied active sorbents: fine substances
with a developed surface - sawdust, ash,
peat, clay, coke breeze, activated carbons.
Municipal sewage (domestic waste water)
contain large amounts of:
• synthetic detergents (surfactants);
• oils and fats,
• nitrate and nitrite,
• phosphorus, chloride and sulfate,
• vegetable fibers,
• faecal matter,
• food waste.
Methods for biological treatment of municipal
wastewater
Cleaning equipment
Microorganisms
Anaerobic
digestion
Aerobic
oxidation
Bacteria
Protozoa
Activated
sludge (silt)
Biofilm
COMPOSITION AND PROPERTIES
Activated sludge (silt):
colloidal system, pH 4 - 9,
the negative charge
Biocenosis of:
bacteria, worms, fungi,
yeasts, algae - in total
about 12 species, solid
substrate
Airotanks,
methane tanks
Biotanks,
submerged
biofilters
Biofilters
Biofilms: mucous fouling
thickness of 1 - 3 mm
Biocenosis of: bacteria,
fungi, yeast
General chemical composition of the
sludge: C54H212O82N8S7
Agricultural wastewater and livestock
enterprises
Contain about 60% of organic origin,
including:
• biological contaminants (bacteria, viruses,
fungi, algae);
• pesticides, herbicides, insecticides;
• chemical fertilizers;
• Insecticides in the form of suspensions,
dissolved in the oil
Classification of gas emissions
based on the aggregative state
Gas emissions
GASEOUS:
sulfur dioxide,
oxides of nitrogen &
carbon,
hydrocarbons
LIQUID
Solutions of acid,
alkalis, salts
SOLID
carcinogens,
heavy metals & their compounds
organic and inorganic dust
soot, tarry materials
Amount of gas and dust emissions on a
global industry
Brunch of industry
Emisssion, %
Energy (thermal power
plant)
Ferrous and nonferrous
metallurgy
Refining industry
43,0
Other brunches
23,1
23,1
10,8
Methods of the air protection
1. Prevention of harmful contaminants and
their introduction into the ambient air.
2. Cleaning of the air-gas emissions:
mechanical, chemical, physical and
chemical.
3. Creation of buffer zones around industrial
enterprises
Methods for cleaning of gas & dust
emissions from aerosols
1. Mechanical cleaning by dry and wet methods:
• dry - gravitational settling, inertial and
centrifugal dust removal, filtration;
• wet - centrifugal scrubbers, foam scrubbers,
Venturi scrubbers
Gravitational settling
dust-filled
gas
processed
gas
1
2
2
Hollow chamber (long tube or corrugated sleeve) for
the deposition of dust: 1 - body, 2 - tanks with hose to
remove dust
Purified gas
Polluted
stream
\
2
1
3
4
dust
Construction of cylindrical cyclone:
1-socket, 2-inner cylinder, 3-outer cylinder, 4 – tank for the dust.
"Wet" cleaning of gas and dust emissions from
aerosols
gas
gas
gas
liquid
gas
liquid
liquid
gas
gas
Sludge
Sludge
Sludge
Scheme of the main ways of dust collection in the wet scrubber:
a - in the volume of liquid, b – by a film of liquid, c – by sprayed liquid
1 - gas bubbles, 2 - liquid drops 3 - solids
Физико-химическая очистка газопылевых
выбросов от газообразных примесей
Хемосорбция, адсорбция, каталитическое и
термическое окисление
Абсорбенты: вода, растворы аммиака, едких и карбонатных
щелочей, солей марганца, этаноламины, масла, суспензии
гидроксида кальция, сульфат магния и т.д.
Очищенный
поток
Абсорбент
2
1
Загрязненный
поток
Отвод на
регенерацию или
рециркуляцию
Схема абсорбера:
1 – корпус абсорбера; 2 – сетка с насадками