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.