LIVING ENVIRONMENT AND HEALTH
Qiaoyuan Yang
Department of Preventive MedicineGuangzhou Medical College
• Living environment is concerned with all the
factors,circumstances and conditions in the environment
or surroundings of a human being which can influence
the human health and well-being.
• The environment provides man with the essential life
support systems;but it also presents him with a variety
of hazards which may prejudice his health.
• Living environmental conditions include
air,water,soil,food and shelter.
Constituent of Environment
• Section 1 air sanitation
• Section 2 water sanitation
• Section 3 geological environment and soil
Section 1 air sanitation
1.Air
• No element of the natural world is more essential to life t
han air.
• The chemical and physical characters are obviously relat
ed to the human health and desease.
Atmospheric sphereAtmospheric sphere
• Definition : the air layer which surround the surface of earth and circumrotate with earth.
The thick is around 2000km ~ 3000km.(no evident upper bound )
Character: physics and chemistry of atmospheric sphere is change with height.
There are three delamination methods of air vertical structure.
• according to the vertical change of air temperature
troposphere
stratosphere
intermediun layer
hot layer
exosphere
• According to air ionized condition ionosphere nonionosphere
• According to chemical composition homosphere nonhomosphere
troposphere
stratosphere
Ozone layer25 ~35km, 20km
umbrella of earth
Upright structure of atmospheric sphere
mesphere
thermosphere
• stratosphere : including of ozone layer(the air temperature inversion)
• troposphere : including of air,water vapour,fume,micro-organism. (the air temperature decrease progressively )
1. Nearness earth2. The temperature is change3. Upright and horizontal move 4. Mostly climate changes happen in this layer5.Contain mostly pollutants
There is a intimate relationship between the
troposphere and the mankind.
The pollutants concentrate mainly in the troposphere.
The air pollutions often happen in this layer.
People’s living condition will be importantly effected
by the troposphere,especially the range near to the
ground.
(1) chemical composition
• Pure air is colorless, odorless, and tasteless. (mixing gas)
• Air is mainly composed of nitrogen,oxygen,argon. (99.96%)
• Some water vapor , (below 4%)
• Free radical ( source : ptotochemical reation of oz
one )
Constant compositionConstant composition : nitrogen,oxygen,orgen,noble gas(Ne,He,etc)
Changeable compositionChangeable composition : CO2 and water vapor
unconstant compositionunconstant composition : 1.dust,hydrogen sulfide (H2S),nitrogen oxide(NOX),foul gas produced by volcanic eruption,earthquake and so on.
2.coom,power dust, nitrogen oxide(NOX) produced by human activities
• Including of solar radiation,air ioniz
ation and meteorologic factor which
are closed to human health.
(2)Physical state
• pigmentation 黑色素沉着作用
• Erythema effect 红斑作用• Anti-rachitic effect 抗
佝偻病作用• Germicidal effect 杀菌作
用
• Heat effect
• UltravioletUltravioletUV-A ( 320~400 nm)
UV-B ( 275~320 nm)
UV-C ( 200~275 nm)
• Infrared lay ( 760~30000 nm)
• Visible light ( 400~760 nm)
solar radiation
help to form sense of sight
• The adequate solar radiation could prevent
people from eyes fatigue and near sight.
• People is easy to get tired because of the weak
light.
Light ionLight ion :: neutral gas element sticking to ion, neutral gas element sticking to ion, 10-
15 molecule
Heavy ionHeavy ion :: light ion binding with dust and smog.light ion binding with dust and smog.
air ionization
Positive ionPositive ion
Negative ion Negative ion (beneficial)(beneficial)
hygienic assessment of air ionhygienic assessment of air ion• Quantity of air ion : negative ion , cleaning degree
• Heavy ion / light ion> 50 : air is muddy
• air temperature,humidity,air current,air pressure
• Meteorologic factor can adjust many physiologic function.
(cold and thermal sensation,body heat regulation,nervou
s system funtion,immune function,etc)
• Meteorologic factor make a important role in the diffusio
n process of air pollutants 。
meteorologic factor
• The quality of the air we breathe can have a
significant impact on our quality of life.
• The Industrial Revolution in Europe in the 19th
century saw the beginning of air pollution as we
know it today, which has gradually become a global
problem.
2.Air pollution
• Air pollution is aggravated because of four
developments: increasing traffic, growing
cities, rapid economic development, and
industrialization.
• Many countries have a "serious" air
pollution problem.
• Definition
• 由于人类活动或自然过程,使得排放到大气中物质的浓度及持续时间足以对人的舒适感、健康,对设施或环境产生不利影响时,称大气污染
1. Natural sources
2. Man-made sources
• Industrial pollution
• Living pollution
• Traffic transportation
Sources of air pollutants
Natural sources
• Probably the most important natural source of air pollution is volcanic activity( 火山爆发 ), which at times pours great amounts of ash and toxic fumes into the atmosphere.
• Dust storms in desert areas and smoke from forest fires and grass fires contribute to chemical and particulate pollution of the air.
Industry and enterprise may be chiefly responsible to the air pollution.
1.Combustion of fuel ( coal & oil )2. Emission from working process( native material & finished product )
Man-made sources --1
Industrial pollution
• The following industries are among those that emit a
great deal of pollutants into the air: thermal power pla
nts, cement, steel, refineries, petro chemicals, and mi
nes.
Living pollution
Living cooking range &heating boiler
Combustion of fuel
coal
Man-made sources --2
我国主要燃料中灰分和硫含量我国主要燃料中灰分和硫含量
燃烧种类 灰分( % ) 含硫量( % )
煤 5-35 0.7-5.5重油 0.1-0.51 0.1-3.8
页岩 40-66 1.2-5.5
燃烧一吨煤排出的各种有害物质的重量 (kg )
有害物质 电厂锅炉 工业锅炉 取暖锅炉 SO2 60 60 60
CO 0.23 1.4 22.7 NO2 9.1 9.1 3.6
HC 0.1 0.5 5 Dust 一般燃烧 11 11 11燃烧良好时 3 6 9
Traffic transportation
result from the combustion of mobile vehicle fuel
Mobile pollution source( 流动污染源 )
the pollution range is related to it’s race.
Man-made sources --3
汽 车 排 气汽 车 排 气一氧化碳 100
%碳氢化合物 60%氮氧化物 100%
从曲轴箱漏出的气体从曲轴箱漏出的气体碳氢化合物 20%
从油箱和汽化器中挥发的汽油从油箱和汽化器中挥发的汽油碳氢化合物 20%
机动车尾气污染物占大城市空气污染物 的比例( % )
Pb CO CO2 CH
美国 69 70 33 35
上海 85 80 96 56
北京 63 73 22
• Air pollution can affect our health in many ways. • Different groups of individuals are affected by air
pollution in different ways. • The extent to which an individual is harmed by air
pollution usually depends on the total exposure to the damaging chemicals, i.e., the duration of exposure and the concentration of the chemicals must be taken into account.
How can air pollution hurt our health?
ingressive pathway of air ingressive pathway of air
pollutantpollutant
Respiratory passage(major)
Digestive tube
Skin
A small quantity
How can air pollutants intrude into our body?
The effects of air pollution on human health
Direct harm
Indirect harm
• Acute poisoning
• Chronic and long-term effect
direct direct health hazard of air pollution
• ( 一 ) Acute poisoning
• The concentration of pollutants rapidly increase in short-term , a lot of pollutants (fume, exhaust gas) have been absorbed by population induced acute poisoning.
• Examples of acute effects include irritation to the eyes, nose and throat, and upper respiratory infections such as bronchitis and pneumonia.
• Other symptoms can include headaches, nausea, and allergic reactions.
• Short-term air pollution can aggravate the medical conditions of individuals with asthma and emphysema.
• Smog episode
• productive accident
• Coal smog(Lond
on)
• Photochemical s
mog(losangeles)
Major type
Productive accident
• Toxic gas leakage accident in Bphopal, india (印度博帕尔毒气泄漏事件,异氰酸甲酯 )
• Explosion of unclear power plant in USSR
(前苏联切尔诺贝利核电站爆炸事件)
• Special disasters: fire, explosion of volcano, leak of gas, the use of chemical weapon.
Smog incident
• Coal smog incident: Physical: primary pollutants
• Photochemical smog incident: Chemical: secondary pollutants
Coal smog incident
SO2 + fluoride
SO2 + metal dust
The major pollutant of London smog incident
sulfur dioxide and fog (created by burning coal and heavy oil that contain sulfur impurities in power plants, industrial plants, etc... )
Photochemical smog incident
• Definition: Nitrogen oxides from motor vehicle exhaust gas and hydrocarbons from industry process emission are converted to ozone and other photochemical species form light blue smog through photochemical reaction under sunlight ultraviolet ray.
• Los Angeles photochemical smog incident : The first time of this phenomena was occurred in Los angles (1943).
•Pollutant: nitrogen oxides +
hydrocarbons
•Photochemical reaction
Los Angeles photochemical smog incident
Graph of photochemical reaction
10%
Over 85%
SO2----SO3 ------ H2SO4
Smog incident•Coal smog incident:
Physical: primary pollutants
London smog incident
•Photochemical smog incident:
Chemical: secondary pollutants
Los Angeles photochemical smog incident
煤烟型烟雾事件与光化学型烟雾事件发生条件的比较
煤烟型烟雾事件 光化学型烟雾事件污染来源 煤和石油制品燃烧 石油制品燃烧
主要污染物 颗粒物、 SO2 、硫酸雾 HCs 、 NOX 、 O3 、 SO2 、 CO 、 PANs
发生季节 冬季 夏秋季
发生时间气象条件
逆温类型
地理条件
症状
易感人群
早晨气温低 (-1℃~ 4 )℃ 、气压高、风速很低、湿度 85% 以上、有雾
辐射逆温
河谷或盆地易发生
咳嗽、喉痛、胸痛、呼吸困难,伴有恶心、呕吐、发绀等,死亡原因多为支气管炎、肺炎和心脏病。
老年人、婴幼儿以及心、肺疾病患者
中午或午后气温高 (24℃~ 33 )℃ 、风速很低、湿度 70% 以下、天气晴朗、紫外线强烈
下沉逆温
南北纬度 60º 以下地区易发生
眼睛红肿流泪、咽喉痛、咳嗽、喘息、呼吸困难、头痛、胸痛、疲劳感和皮肤潮红等,严重者可出现心肺功能障碍或衰竭心、肺疾病患者
Chronic and long-term effect
• Inflammation caused by long-t
erm stimulation
• Cardiovascular disease
• Chronic Chemical poisoning
• Allergic reation
• Carcinogenic action
• Non-special damage (descend
of immune function)
( 二 ) chronic harm
1. Caused inflammation by long-term irritation: (1) COPD: chronic obstructive pulmonary diseases, including chro
nic bronchitis, bronchial asthma, and emphysema (2) the morbidity and mortality is higher
2. Accelerate aging of the lung: air pollution is stronger than smoke in the lung damage
3. Cardiovascular disease: (1) lung disease can decrease pulmonary function and increase pul
monic pressure, caused pneumocardial disease
(2) hemoglobin’s affinity for O2 decrease, oxygen-carrying capacity, caused hypoxia, increase heart motion, caused penumocardial disease
空气污染与居民眼结膜炎检出率
三 明 鞍 山 沈 阳 平顶山 对照 重污染 轻污染 重污染 轻污染 严重污染 对照 污染 7.2 43.2 3.3 18.7 3.2 7.3 0.4 10.6
4. Decreased immunological function: (1) Immunological function decrease is a early index.
(2) Various in different age populations.
(3) Child is most susceptivity and sentitivity
5. Allergy: (1) Allergen exist in air including dust etc.
(2) Some pollutants such as SO2, formaldehyde, petroleum product
Effect of air pollution on immunological competence in children
地区 杀菌力指数 溶菌酶 (mg/L)
碱性磷酸酶活性
工业区 2.5±1.0 25±2.8 49.35±6.2
对照区 4.2±0.4 47.8±5.2 80.9±17.7
( 三 ) long-term effect
1. Chronic poisoning: metal, such as Pb, Cd, Cr, As,
F, and Hg.
2. Carcinogenesis:
(1) exist carcinogen, such as arsenic, benzo(a)pyrene
(2) air pollution associated with morbidity and mortality from lung cancer.
Indirect harm
of air pollution on health
• Acid rain
• Greenhouse effect
• Ozone depletion
• Climatic changes
indirect indirect health hazards of air pollution
Acid rain
• When a pollutant, such as sulfuric acid combines with droplets of water in the air, the water (or snow) can become acidified acidified .
• The effects of acid rain on the environment can be very serious. It damages plants by destroying their leaves, it poisons the soil, and it changes the chemistry of lakes and streams.
Greenhouse effect• The Greenhouse Effect, also referred to as global
warming, is generally believed to come from the build up
of carbon dioxide gas in the atmosphere.
• This buildup acts like a blanket and traps heat close
to the surface of our earth.
• Carbon dioxide is produced when fuels are burned.
• The amount of carbon dioxide in the air is continuing to increase.
• Changes of even a few degrees will affect us all through changes in the climate and even the possibility that the polar ice caps may melt. (One of the consequences of polar ice cap melting would be a rise in global sea level, resulting in widespread coastal flooding.)
Ozone depletion
• Ozone depletion is another result of pollution. Chemicals released by our activities affect the stratosphere , one of the atmospheric layers surrounding earth.
• The ozone layer in the stratosphere protects the earth from harmful ultraviolet radiation from the sun.
The health effects of major air pollutants
• Sulphur dioxide
• Suspended particulate matter (S
PM)
• Oxides of Nitrogen
• Polycyclic aromatic hydrocarbon( 多环芳烃 )
• Dioxins( 二口恶英类 )
Sulphur dioxide (SO2)
• Sulphur dioxide (SO2) is a gas produced from
burning coal, mainly in thermal power plants. S
ome industrial processes, such as production o
f paper and smelting of metals, produce sulphu
r dioxide.
• It is a major contributor to smog and acid rain.
Sulfur dioxide can lead to lung diseases.
(1) SO(1) SO22+ H+ H22SOSO44::• 刺激眼、鼻咽粘膜• 刺激上呼吸道收缩、分泌增多;炎症、腐
蚀性组织坏死;致急性支气管炎、肺水肿。(2) (2) SOSO22++ 飘尘飘尘::进入肺深部 FeO3 H2SO4 肺纤维病变 肺气肿(3) SO(3) SO22:: 变态反应原,引起支气管哮喘(4) SO(4) SO22+B(a)P+B(a)P ::促癌作用
SOSO22 来源于含硫来源于含硫燃料(煤、石燃料(煤、石油)的燃烧。油)的燃烧。
Nitrogen oxide (Nox)
• Nitrogen oxide (Nox) is produced from burning fuels including petrol, diesel, and coal.
NOx(little water-solubility)
Little stimulation to eyes and upper airway
it is easy to intrude into deep airway and air sac
( peroxidation of alveolar surfactant , damage the ciliated epithelial cells and alveolar cell , cause emphysema,wet lung, COPD)
NOx nitrite( 亚硝酸盐 )
combine with hemoglobin( 血红蛋白 )
Decrease the oxygen carrying capacity
Organiztion hypoxia
• The pulmonary damage is obvious when the most amount of Nitro
gen oxide is NO2. But when the most amount of Nitrogen oxide i
s NO,methemoglobinemia and the damage to the central nerve
• Nitrogen oxide (Nox) causes smog and acid rain.
Suspended particulate matter (SPM)
• Suspended particulate matter (SPM) consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze which reduces visibility.
• The finer of these particles, when breathed in can lodge in our lungs and cause lung damage and respiratory problems.
Health effect of SPM :• Blockage effect to partial organ
ization
• immunotoxicity
• “carrier”function
• promotion ( metal )• Influence solar radiation
• Long-term hazard
3.Indoor Air Pollution
• Persons spend nearly 75 percent of their life time indoors at work,at
school,and at home or between these places in an automobile.They have
more chances to expose to indoor air pollutants than outdoor air
pollutants.
• For infants, the elderly, persons with chronic diseases, and most urban
residents of any age, the proportion is probably higher,so they are at greater
risk.
• In addition, the concentrations of many pollutants indoors exceed those
outdoors.
• The indoor environment has only recently be
en widely appreciated as a major contributor
to total personsal exposure.
• Indoor air pollution is now identified as one o
f the most critical global environmental probl
ems.
Magnitude
Sick-Building Syndromes(SBS)
• This collection of ailments,defined by a set of
persistent symptoms enduring at least 2
weeks,occurs in at least 20 percent of those
exposed and is typically of unknown specific
etiology but is relieved sometime after an affected
individual leaves the offending building.
Symptoms Commonly Associated with the Sick-Building Syndromes
• Eyes,nose,and throat irritation• Headaches• Fatigue• Reduced attention span• Irritability• Nasal congestion• Difficulty breathing• Nosebleeds• Dry skin• Nausea
Sources
• Indoor air pollutants may be physical,chemical or biological.
• There are many sources of indoor air pollution. Tobacco smoke, cooking and heating appliances, and vapors from building materials, paints, furniture, etc.
• Pollution exposure at home and work is often greater than outdoors.
⑴Combustion products
(2)Human activities(tobacco smoke)
(3)building and decorative materials
(4)household chemicals
(4)Pollutants from outdoor
Health Effects of the Major Indoor Air Pollutants
• Fomaldehyde( 甲醛 )• Volatile organic compounds ( 挥发性有机化
合物 )• Carbon monoxide(CO)• Biological factor
Evaluation of indoor air quality
• Carbon dioxide(≤0.10 %)
• Microbes(general bacterial polulation)
• Suspended particulate matter(≤0.15mg/m3)
Section 2 Water
INTRODUCTION • Water sustains life.• 60% - 75% of the adult human body is water -
82% of blood is water; 70% of the brain and 90% of the lungs are made up of waterBlood in animals and sap in plants is composed mainly of water
• Life on earth probably originated in water • Water is essential for industry and agriculture.
• Our earth is very rich in water resources. (water is comprising over 70% of the Earth’s surface.)
• It is limited for utilisation.(Of the world’s water ,97% is in the ocean and 2% in ice masses;1% is fresh and available for human use.)
• The demand for water has increased over the years and this has led to water scarcity in many parts of the world.
• The world is heading towards a freshwater crisis due
mainly due to its mismanagement. This crisis is already
evident in many parts of the world
• Another reason for the depletion of freshwater
resources, particularly groundwater resources, is a
rapidly increasing human population.
• Freshwater resources all over the world are threatened not only by over exploitation and poor management but also by ecological degradation.
• A worlewide water shortage is imminent.• Water shortage and higher costs for water appear inevitable,thus,we need to keep our surface water clean and make good use of it.
water pollution is serious in china
• the Chinese industry economy increases quickly, the pollution of
the environment is serious more 。 • Due to the increase in population there has been a rise in the
demand for food, space for housing, consumer products, etc.,
which has in turn resulted in increased industrialization,
urbanization, and demands in agriculture thereby leading to both
river and groundwater contamination.
1.Classification and characteristic
• Fall water
• Surface water
• Underground water
水源 水量 水质 易受污染程度 利用的可行性
降水 小,易波动 良好 容易 大
地面水 大,易波动 一般 很容易 较大
地下水 中,稳定 较好 不容易 一般
2.Sanitary requirement of drinking water
• There must be no pathogenic microorganism and parasite egg in the water,it can prevent the conveying of water-borne infection.
• Chemical materials and radioactive materials in the water must not hazardous to human health.
• Good sense organ character
• The drinking water standard was formulated
according to the Sanitary requirement of
drinking water ,and the feasibility in economic and
technical aspects were taken into account too.
drinking water standarddrinking water standard
• Sensitive and General chemical indexSensitive and General chemical index
• Toxicological indexToxicological index
• Bacteriological indexBacteriological index
• Radioactive indexRadioactive index
Sensitive and General chemical indexSensitive and General chemical index
• Water temperature
• chroma
• Odor and taste
• Power of hydrogen
• Turbidity
• Tatal hardness
• Consumed oxygen
……..
Toxicological indexToxicological index
• There are 11 toxicological test items.
(砷、铬、氰化物、氟化物等。 )
• More rigid rules of some items were set in r
ecent years.
• General bacterial population (细菌总数)• Tatal coli group(总大肠菌群 )
• Dung coli group(粪大肠菌群 )
• Liberated chlorine residual (游离性余氯 )
Bacteriological indexBacteriological index
Radioactive indexRadioactive index
• The radioactivity of drinking water is very
small in normal conditions.
• the radioactivity of Þ ray < 0.5Bq/L
the radioactivity of ß ray < 1Bq/L
3.Water Pollution
• Water pollution is any chemical, physical or biological change in the quality of water that has a harmful effect on any living thing that drinks or uses or lives (in) it.
• When humans drink polluted water it often has serious effects on their health. Water pollution can also make water unsuited for the desired use.
Where does water pollution come from?
• Water pollution is usually caused by human
activities.
• There are several classes of water pollutants.
• The first are disease-causing agents. These
are bacteria, viruses, protozoa and parasitic
worms that enter sewage systems and
untreated waste.
• A second category of water pollutants is
oxygen-demanding wastes; wastes that
can be decomposed by oxygen-requiring
bacteria. When large populations of
decomposing bacteria are converting these
wastes it can deplete oxygen levels in the
water. This causes other organisms in the
water, such as fish, to die.
• A third class of water pollutants is water-soluble inorganic pollutants, such as acids, salts and toxic metals. Large quantities of these compounds will make water unfit to drink and will cause the death of aquatic life.
• Another class of water pollutants are nutrients; they are water-soluble nitrates and phosphates that cause excessive growth of algae and other water plants, which deplete the water's oxygen supply. This kills fish and, when found in drinking water, can kill young children.
• Water can also be polluted by a number of organic compounds such as oil, plastics and pesticides, which are harmful to humans and all plants and animals in the water.
• A very dangerous category is suspended sediment, because it causes depletion in the water's light absorption and the particles spread dangerous compounds such as pesticides through the water.
• Finally, water-soluble radioactive compounds can cause cancer, birth defects and genetic damage and are thus very dangerous
4.water pollution and its hazards
• Physical pollution
• Chemical pollution
• Biological pollution
Physical pollution
• heat pollution
• Radioactive pollution
Biological pollution
• The most common hazard of
biological pollution is water-borne
infectious disease.
*water-borne infectious disease
• Epidemic causeEpidemic cause
1.the water was supplied to inhabitant without pro
per conditionding after the water resource was p
olluted by pathogens.
2.the processed drinking water is recontaminted i
n the transporting and storing process.
* water-borne infectious disease
• Epidemic characteristic:1.Large amount of case will appear (break out)after the water r
esource was polluted generously.
2.Case distribution is in one accord with water supply range ;
3.Desease will be controlled quickly once the governing measures be taken.
4.We can get known about the pathway which the water was polluted by the epidemiogic survey probably; and there is a abnormal change in bacteriological examination of water 。
pathogen
Pathogenic bacteria
salmonella(沙门氏菌属),shigella(志贺氏菌属),enteropat
hogenic E coli(致病性大肠杆菌)
virus
Parasite and worm
Chemical pollution
• Organic pollutant
( phenolic compounds, benzene compounds,halogena
ted hydrocarbon )
• Inorganic pollutant
( heavy metals ,cyanide,fluoride )
Effects of water pollution
• The effects of water pollution are not only devastating to people but also to animals, fish, and birds.
• Polluted water is unsuitable for drinking, recreation, agriculture, and industry.
• More seriously, contaminated water destroys aquatic life and reduces its reproductive ability.
• Eventually, it is a hazard to human health.
5.water conditioning and
centered water supply
The mode of water supply
• Centralized water supply (in the cities)
• De-centralized water supply (in the countryside )
(集中式给水)(集中式给水)
(分散式给水)(分散式给水)
hygienic measures of water supplyhygienic measures of water supply
水量充足水源的选择水源的选择 水质良好 便于防护 技术经济
上合理
水源的卫生防护:水源的卫生防护: 地面水的防护 地下水的防护
饮水的净化与消毒饮水的净化与消毒
Alternative qualification of water resource:Alternative qualification of water resource:
sufficient water capacity
good water quality
be easy to protect
be reasonable in economy and technique
water purification (净化) and disinfection (消
毒)
• Adequate and safe water supplies are essential to
health.
• To be safe,drinking water must be free from
contamination with both pathogenic
microorganisms and harmful chemicals.
• The prevention of drinking water contamination
rests on the purification and disinfection.
coagulation and precipitation
filtration
disinfection
Pre-treatment
Additional treatment
Conventional water conditioning process
purification(混凝和沉淀)(混凝和沉淀)
(过滤)(过滤)
1 、 purification(coagulation and precipitation &filtration)
Purpose• ① It can decrease the content of water suspended
material and colloid particle ,So it can make the turbidance and chrominance to accord with the sanitary standard for drinking water.
• ② it can cut down the content of the water microbes and prepare for the next disinfection process.
*coagulation and precipitation
• Frequently used coagulant agent
1.metal salts ( aluminium salt ,iron salt )
2.high polymer ( cassel yellow, 碱式氯化铝、 PP
A )
• Influential factor to coagulation result
(混凝 剂的种类、水中微粒的性质和含量、水温、水的PH 值等)
* filtration • In this process the water is passed a porous bed to remove fine
suspend and colloidal matter.
• These porous beds are generally made of sand,gravel,other coarse material or a combination of these.
• Some commonly used filtration methods are enumerated below.
Sand filtration
Gravity filtration
Pressure filters
2 、 water disinfection
As the raw water resources are increasingly getting polluted by seepage or by industrial and municipal wastes,disinfection has become an absolute necessity to ensure acailability of safe and generally pathogen free water.
water disinfection is a important measure to prevent the water-borne infectious desease.
• purpose : oxidize organic matter and kill
any remaining microorganisms, and ensure
the security of drinking water .
• Methods of disinfection
Physical methods ( boiling of water,ultraviolet
rays,etc.)
Chemical methods (chlorine and its
compounds,ozone,etc.)
3. Chlorination( 氯化消毒 )
mechanism Cl2 + H2O HOCl +HCl
* active chlorine(chemical valence ≥ -1)
(( 有效氯有效氯 ))
Influential factor of chlorination
• Chlorine dosage and contact period;• Power of hydrogen
• Water temperature
• Turbidity
• Type and amount of microorganisms
The dosage of chlorine is controlled in order to maintain a small residual amout of
free chlorine in the public supply.
The amout of chlorine residual must not be lower than 0.3mg/L after being contac
ted for 30 minites ,and in the strainer ending water the amout of chlorine residu
al must not be lower than 0.05mg/L .
the methods of chlorination
• Common cholorination(普通氯化消毒 )
• Excessive cholorination(过量加氯消毒 )
• Sustained cholorination(持续加氯消毒 )
The merits and demerits of chlorination
• meritsmerits :: ① it is easy to operate and the effect is good.
② there is remnant antiseptic in the treated water ;and the remnant antiseptic is easy to be monitored.
③ the cost is very low.
• demeritsdemerits :: ① chlorine gas is toxic , it is essential to prevent it to leak out a
nd cause some accidents.
② if the concentration of alcohol phenyl (酚含量 ) is high in u
ntreated water, the chlorophenol foul(氯酚臭 ) will appear.
③ if the concentration of organics( 有机物 ) is high in untreate
d water, large amount of chloridate(氯化副产物 ) by –prod
uct will be appear.
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