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Water quality engineering mind map
A mind map about water quality engineering, with a detailed introduction and comprehensive description. I hope it can help interested friends learn.
Edited at 2023-11-25 16:51:41
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Water quality engineering mind map
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- Outline
water quality engineering
Water quality and water quality standards
(1) Types and properties of impurities in natural water
Impurities in water come from classification
Source of impurities
natural process
Human Factors
Classification of impurities
Classified by nature: inorganic matter, organic matter, biological matter
According to size
Dissolved matter 0.1～1.0nm (transparent)
Colloidal particles 1.0~100nm (turbid under light)
Suspended matter 100nm～1μm (turbid or even visible to the naked eye)
According to chemical properties: inorganic impurities, organic impurities, biological impurities
Water quality characteristics of various typical water bodies
Types of natural bodies of water
groundwater
surface water
river water
Lake and reservoir water
seawater
(ii) Pollution and self-purification of water bodies
Common pollutants in water and their sources
According to chemical properties: inorganic organic pollutants
According to physical properties: suspended substances, colloidal substances, soluble substances
According to the pollution characteristics of pollutants
organic matter
biodegradable organic pollutants
Mainly including carbohydrates, proteins, fats and other natural organic substances, organic acids and bases, surfactants, etc.
Properties It is extremely unstable in the natural environment and can be oxidized and decomposed by biological organisms. During decomposition, it consumes dissolved oxygen in the water.
Pollutant evaluation index
BOD biochemical oxygen demand
Carbon oxidation stage
nitrification stage
COD chemical oxygen demand
The amount of oxygen required for chemical oxidants to oxidize organic matter
oxidizing agent
Potassium dichromate
potassium permanganate
TOD total oxygen demand
TOC total organic carbon
Refractory organic pollutants
Features
Extremely chemically stable and not easily degraded by microorganisms
Easily enriched in living organisms, mostly strong "three causes" substances
Pollution evaluation index
COD
TOD
TOC
Special indicators
Inorganic matter
Inorganic pollutants without direct toxic effects
type
Granular inorganic impurities
Acid and alkali substances
Plant nutrients such as nitrogen and phosphorus
Features: No direct toxic effects, but affects the use function of water bodies
Directly toxic inorganic pollutants
Mainly include: six major toxic substances
five poisons
HG
cadmium
lead
chromium
arsenic
cyanide
Features: Highly toxic and can be transferred to the human body through the food chain
Eutrophication of water bodies
Reason: Nitrogen and phosphorus enter the water body
measure
Self-purification of water bodies
definition
process
physical effects
chemical action
Biological effects
Drinking Water Quality and Health
The impact of aquatic organisms on human health
Effects of chemicals in water on human health
Water quality and endemic diseases
Water quality standards
Water quality indicators
Physical indicators: temperature, color, turbidity, smell and taste suspended matter and conductivity
Chemical water quality indicators: BOD5 COD TOD Phytonutrients
Toxicological indicators
radioactive index
Wastewater quality indicators
Physical indicators: including water temperature, color, odor and solids
Chemical indicators: including inorganic substances, pH, nitrogen and phosphorus, non-heavy metals, inorganic toxic substances
Biological indicators: There are three main categories: total number of bacteria, total coliforms and viruses.
Drinking water quality standards
A total of 34 routine testing items
Sensory properties indicators and general chemical indicators
Virological indicators
Bacteriological indicators
radioactive index
62 non-routine testing items
Water quality standards for other water uses
Wastewater discharge standards
Basis for establishing sewage discharge standards
The discharge of sewage directly affects the quality of surface water environment.
my country's "Surface Water Environmental Quality Standards" (GB3838-2002)
Wastewater discharge standards
Introduction to water treatment methods
Main unit processing methods
basic concept
①Water treatment process
②Processing unit
③Tasks of water supply treatment
Physical and chemical treatment methods of water
Concrete
Precipitation and clarification
air flotation
filter
Membrane separation
Adsorption
Ion exchange
neutralize
redox
Biological treatment methods for water
principle
Type: Aerobic and Anaerobic
biofilm approach
suspension growth method
Water supply treatment process
①Remove suspended solids, colloids, bacteria, and viruses from water
Concrete
precipitation
filter
disinfect
② When the water source is seriously polluted by organic matter, add pre-treatment/advanced treatment
Pre-oxidation
Concrete
precipitation
filter
disinfect
Activated carbon adsorption
③ Deodorization and deodorization: use air flotation or microfiltration machine, and use aeration method to remove dissolved gases in water
④Removal of iron, manganese and fluoride: contact oxidation method to remove iron, manganese, activated alumina or coagulation precipitation or agglomeration granulation to remove fluoride
⑤Softening: Remove calcium and magnesium
⑥Desalination and desalination: distillation method, ion exchange method, or chemical softening method
⑦ Reduce water temperature: cooling tower or water spray cooling pool
⑧Water corrosion and scaling control: use corrosion inhibitors and scale inhibitors
Coagulation (coagulation and flocculation)
Colloidal stability
Electric double layer structure of colloids (sterm)
① The lattice substitution in the crystallization of colloidal particles generates charges on the colloid surface (isomorphous substitution, regardless of the dispersion medium water)
② Certain chemical groups on the surface of colloidal particles are ionized in water to make the colloid charged.
③The surface of the colloidal particles reacts with water to dissolve and ionize, making the colloid charged.
④The adsorption of certain ions in the water by colloidal particles makes the colloid charged
Interactions between colloids (DLVO)
Colloidal stability
dynamic stability
with some stability
Colloidal solvation stability
coagulation mechanism
The coagulation mechanism of colloids
Compression of electric double layer
adsorption electroneutralization
adsorption bridging effect
Net catching and sweeping function
flocculation mechanism
Anisotropic flocculation
co-flocculation
Main factors affecting coagulation effect
Effect of water temperature (20-30)
Effect of pH
Effect of alkalinity
The concentration of turbid particles in water
Effects of organic pollutants in water
The influence of coagulant type and dosage
The influence of coagulant dosage method
The influence of hydraulic conditions
coagulant
Inorganic salt coagulant
Aluminum sulfate
PH＜3 Al3 [Al(H2O)6]3 compressed electric double layer
PH4~5 Hydroxy aluminum ion mainly adsorbs and electrically neutralizes
PH6.5～7.5 Aluminum hydroxide Net capture and sweep
Ferric chloride (suitable for dry dosing or concentrated solution dosing)
ferrous sulfate
polymer coagulant
Polyaluminum chloride (PAC)
Polyacrylamide (PAM) monomer shall not exceed 0.0025%
Compound coagulant
Coagulant
Purpose of adding
① Coagulant aid for the purpose of adsorption and bridging to improve the formed floc structure
② Coagulant aid for the purpose of adjusting the pH of raw water to promote hydrolysis of coagulant
③A coagulant aid that improves the coagulation effect by destroying the stabilizing effect of organic pollutants in water on colloidal particles.
④ Coagulant aids that change the chemical form of the coagulant to promote coagulation effect
Bone glue (animal glue)
Principles for selecting coagulants
Good coagulation effect
No toxic effects
adequate supply
low cost
Health approval of new pharmaceuticals
Learn from existing experience
coagulation dynamics
Anisotropic flocculation kinetics (colloidal particles are very small)
co-flocculation kinetics
ideal flocculation reactor
Control indicators of flocculation process
During the mixing phase, stir quickly and vigorously.
Flocculation stage (slow)
coagulation process
Coagulant configuration
①Medicine dissolved
②Solution dilution
Coagulant measurement (equipment includes metering pump, rotor flowmeter, electromagnetic flowmeter, orifice, and mouthpiece)
Dosing of coagulant
Dry hopping and wet hopping
Add before pump Add after pump
Water ejector dosing
Automatic control of coagulant dosage
Flowing Electrodynamic Detection (SCD) Method
Light transmittance pulsation detection method
Flocculated particle image detection and control method
digital modeling method
On-site simulation test method
Quick mix
flocculation reaction
Concrete facilities
Mixing facilities
hydraulic mixing
water pump mixing
tube mixing
mechanical mixing
Flocculation facility
Mechanical flocculation pool (number of pools is not less than 2)
Partition flocculation tank (cannot be used in small water plants)
Folding plate flocculation tank (time 12~20min)
Gate jump (grid) flocculation tank
Perforated cyclone flocculation tank
Other forms of flocculation tanks
coagulation test
precipitation
Sedimentation of impurity particles in still water
Free settling of impurity particles in water
Crowded sedimentation of impurity particles in water
advection sedimentation tank
ideal sedimentation tank theory
Assumptions
① The particles settle freely, and the size, density, and settling speed remain unchanged.
②The flow velocity at each point on the water section from horizontal flow is equal and remains unchanged.
③Particles will be removed when they sink to the bottom of the pool and will not return to the water.
Structural characteristics of muddy water hyperpycnal flow and advection sedimentation tanks
Froude number (stability)
Factors affecting the water flow in the pool: temperature difference, uneven water inlet and distribution, wind and waves
Water inlet and outlet devices for advection sinking pools
Sludge discharge from advection sedimentation tank
Inclined plate, inclined tube sedimentation tank
Inclined plate, inclined tube sedimentation theory (inclination angle is 60º)
Factors affecting the sedimentation efficiency of inclined plates and inclined tubes
Inclined plate, inclined tube sedimentation tank
inclined plate
Inclined tube sedimentation device
Water inlet and distribution device
Water outlet water collection device
Mud discharge device
clarifier
How clarifiers work (contact flocculation)
Mechanical stirring clarifier and pulse sedimentation tank
filter
filter
Slow filter and fast filter
Slow filter 0.1～0.3m/s
Fast filter 5~10m/h
Granular filter material
basic requirements
Have sufficient mechanical strength
Has good chemical stability
With user-required particle size and particle size composition
Local materials, sufficient supply
Grading: the weight proportion of particles of various particle sizes
Operation of quick filter
Changes in effluent quality and head loss of rapid filter tanks
Initial filtered water: When filtration is resumed after backwashing in the rapid filter tank, the effluent turbidity is high.
Maturity period: the duration of initial water filtration
Effective filtration period: After the turbidity of the initially filtered water drops to the required value, it enters the effective period.
Leakage turbidity: During the effective filtration period, until the effluent turbidity rises to equal the required value, the leakage point is reached, and the corresponding turbidity value is called leakage turbidity.
Water quality cycle: The period from when the filter enters the effective filtration period until the turbidity of the effluent reaches the leakage value is called the water quality cycle.
Pressure cycle: As the clarification and filtration process proceeds, the head loss h of the filter layer gradually increases. When it reaches the maximum value, the filter layer needs to be backwashed.
Filtration head: refers to the difference between the highest water level of the water before filtration and the water level after filtration.
Water quality cycle ≥ pressure cycle, optimal when equal
Optimization of filter layer in fast filter
Hydraulic grading phenomenon: Hydraulic grading of the filter material will occur when the uneven filter material filter layer is backwashed in the filter tank.
negative head
Reason: When the filter reaches the point where the upper fine filter material filter layer is seriously blocked, the water head loss increases sharply. At this time, the pressure of part of the filter layer is lower than the atmospheric pressure.
Preventive measures
Increase water depth on sand surface
Set the water outlet on the surface of the filter layer
filter material
Top: big and light
Bottom: small and heavy
Control of filter operation:
Variable head constant velocity filtration: siphon filter, valveless filter
Constant velocity and equal water head: fast filter, v-shaped filter
Variable speed and water head
Kamann-Conzeni: Head loss is proportional to flow rate/porosity
filter theory
The mechanism of filtration to remove suspended solids: migration-adhesion-desorption
Basic function {mainly depends on the size of the particle size}
precipitation
inertia
intercept
diffusion
dynamic effect
Backwashing of filter layer
Backwash basis
Effluent turbidity
head loss
filter time
Control indicators
strength
Rinse time
head loss
Expansion rate
Filter water distribution system and supporting layer
water distribution system
Function: Collect filtered water during filtration, and distribute water evenly during backwashing
Classification
Large resistance - quantitative control, uniform water distribution Disadvantages: large head loss Use perforated pipe Ordinary fast filter V-shaped filter
Small resistance - weak control, small head loss. Use grid, orifice plate, perforated channel, filter head
Air and water backwash of filter layer
Advantages: Hydraulic classification is not obvious
Strong ability to intercept pollution
Save half the water consumption
Several common filters
The V-type filter has strict requirements for flushing operations and strict construction requirements.
Ordinary fast filter: filtration speed 8~10m/s
Adsorption
Introduction to adsorption
adsorption phenomenon
In the two-phase interface layer, a certain substance can automatically become enriched.
Classification
Physical adsorption Van der Waals force Small adsorption heat No selectivity Unstable Easy to desorb Single or multi-layer Fast adsorption rate
Chemical adsorption Chemical bond Large adsorption heat Selective Stable Single layer structure Slow adsorption rate
adsorption isotherm
Activated carbon adsorption
Classification
Powder
Granular
Rod-shaped
preparation
Carbonization: Also called pyrolysis, it is the heating of raw materials in isolation from air. The general temperature is below 600°C.
Activation: heating the carbonized material under the action of an oxidant to produce activated carbon products
nature
physical properties
Has a large specific surface area
Has a well-developed pore structure
Powdered carbon is difficult to recycle because of its small particle size, while granular carbon is conducive to regeneration.
Chemical properties: refers to the surface properties of activated carbon [mainly related to surface functional groups]
Adsorption properties: Parameters commonly used to characterize the adsorption properties of activated carbon include methylene blue adsorption value [mesoporous], iodine adsorption value [micropore], carbon tetrachloride adsorption value [gas phase adsorption capacity] BET area
Factors affecting the adsorption performance of activated carbon
Properties of activated carbon
Properties of adsorbate
other sexual factors
Activated carbon adsorption process
penetration curve
Adsorption tape
Activated carbon column test
Contact time
leak time
Applications of activated carbon
Functions of activated carbon
Removal of odor and smell
Total organic carbon removal
Removal of disinfection by-product precursors
Removal of volatile organic compounds
Removal of synthetic organic matter
Applications of powdered carbon
Dosage amount
Contact time
Choice of dosing points
Dosing methods and equipment
Regeneration of activated carbon
method
Thermal regeneration method
chemical regeneration method
chemical oxidation regeneration method
biological regeneration method
Wet oxidation regeneration method
ultrasonic regeneration method
Process: Dehydration··Drying··Carbonization··Activation··Cooling·
The regenerated carbon loss is about 7% to 10%
Other adsorbents in water treatment processes
Zeolite [adsorption of unsaturated organic matter]
diatomite
fly ash
Redox and Disinfection
Overview
Oxidizing agents and disinfection methods
Often used to remove pathogenic microorganisms and organic and inorganic pollutants from water
Common oxidizing agents
Chlorine [has a strong substitution effect, and there may be residual chlorine after treatment]
Ozone [strong bactericidal effect, selective]
Chlorine dioxide [a good disinfectant, it needs to be prepared on site, and the dosage should not be too large]
Hydrogen peroxide [strong oxidant, mainly used for advanced oxidation of water and sewage]
Permanganate [strong oxidant, selective]
persulfate
ferrate
chemical oxidation
According to the different dosing points of chemicals in the water treatment process and the different effects they produce, oxidation can be divided into pre-oxidation, intermediate oxidation and post-oxidation.
Disinfection and inactivation
Chick's Law
CT value
Chlorine oxidation and disinfection
Properties of chlorine: yellow gas, irritating, easily soluble in water
Chlorine disinfection process
The lower the PH, the stronger the disinfection effect, which proves that HOCL is the main ingredient for disinfection.
The higher the temperature, the better the disinfection effect
Chloramine disinfection
Free chlorine disinfection is effective
Combined chlorine disinfection is highly durable
Breakpoint chlorination method
Formation and control of chlorination disinfection by-products (DBP)
Main products: trihalomethane, haloacetic acid
Control Technology;
Enhanced concrete
Granular activated carbon adsorption
Filter membrane [expensive and troublesome]
Ozone oxidation and disinfection
Mechanism of action: Oxidize hydrogen sulfide in water into silver sulfate to remove its odor
Effect of ozone pre-oxidation on water treatment effect
Remove algae and smell
Controlling the role of chlorination disinfection by-products
Control effect of ozone pre-oxidation on trihalomethanes
The effect of ozone pre-oxidation on other chlorination disinfection by-products
Oxidative coagulation aid
Ozone oxidation by-products
Ozone intermediate oxidation
Features
Break down large organic molecules into small biodegradable molecules
Ozone cannot completely oxidize and destroy the Jiangsanlujiawan precursor, but only enhances its reproducibility.
Ozone disinfection
Disinfection effect: ozone > chlorine dioxide > chlorine > chlorine ammonia
Disinfectant stability: chlorine ammonia > chlorine > chlorine dioxide > ozone
Mutational activity of disinfected water: chlorine > chlorine ammonia > chlorine dioxide > ozone
Disinfection cost: Ozone ≈ chlorine dioxide > chlorine > chlorine ammonia
Other oxidation and disinfection methods
Chlorine dioxide oxidation and disinfection
Physical and chemical properties: green gas, easily soluble in water, more irritating than chlorine
Oxidizing properties [PH value has a great influence on chlorine dioxide oxidation treatment]
Chlorine dioxide pre-oxidation
Advantages: The concentration of chlorination disinfection by-products is significantly reduced
Disadvantages: interaction with reducing components in water will also produce a series of by-products
The disinfection effect of chlorine dioxide [the ammonia in the water does not affect the disinfection effect] is stronger than chlorine in killing general bacteria and many viruses, and the disinfection effect is less affected by PH
Preparation of chlorine dioxide
Prepared with sodium chlorite and chlorine, economical advantage
Prepared by reacting acid with sodium chlorite {conversion rate 80%}
permanganate oxidation
Ion exchange
Ion exchange overview
The structure of ion exchange resin
Polymer skeleton has a huge spatial structure and is a water-insoluble polymer compound.
Exchangeable active groups that provide exchangeable ions
preparation
monomer
Cross-linking agent: a bridging substance that forms a polymer. It is a component that fixes the shape of the resin and enhances the mechanical strength of the resin. The degree of cross-linking is generally 7% to 12%.
exchange group
Physical and chemical properties of ion exchange resin
Physical properties
granularity
density
wet true density
Wet apparent density
Moisture content
Swellability
Mechanical strength
Thermal stability
chemical properties
chemical stability
Reversibility
Acidity and alkalinity
Exchange capacity of ion exchange resin