EnE 301

 

Why Environmental Engineering:

The goal of the course is to provide students with the scientific principles, concepts, and methodologies required to understand the interrelationships of the natural world, to identify and analyze environmental problems both natural and human-made, to evaluate the relative risks associated with these problems, and to examine alternative solutions for resolving and/or preventing them.

The beginning of 20th century: Major emphasis on control of epidemic communicable diseases. Importance on water supply and sewage disposal.

The middle of 20th century: Solid waste disposal, air pollution control, occupational hygiene

gain significance.

The latter part of 20th century: Chemical pollution, radiation hazards, and hazardous waste

management join the array of environmental pollution problems.

Ecology: science dealing with interrelationship of things.Organisms depend on the quality of

environment, and they also exert an influence on the quality of environment.

Man exerts a tremendous impact on the environment through:

Extraction of resources, and Modification and manipulation of the environment, and pollution resulting

from deposition of wastes.

Ecological impact on environment: on the productivity of the ecosystem (green

plants, atmospheric oxygen)on other organisms (microorganisms, insects,

animals)on climate (global warming, ozone hole, acid

rain) 

Health impact: Due to microbiological pollution Due to microchemical pollution

Environment:The human environment encompasses all physical, chemical,

biological and social processes and influences, which individually or in combination exert directly or indirectly a significant influence on the health and well-being of human race.

Health: Health is not merely the absence of disease or infirmity, but a state of physical, mental, and social well-being. (WHO)

  In developing countries: Microbiological pollution is of more significance. Environmental factors serve as links in the chain of transmission of diseases Communicable disease like cholera, typhoid, dysentery, malaria, bilharziasis, etc.  In industrialized countries: microphysicochemical pollution is of more significance. microchemical health hazards more complex than communicable diseases cancer, leukemia, cardiovascular disorders, etc 

ENVIRONMENTAL ENGINEERING definition:Environmental Engineering is manifest by sound

engineering thought and practice in the solution of problems of environmental sanitation, notably in the provision of safe, palatable, and ample public water supplies, the proper disposal of or recycle of waste water and solid wastes; the adequate drainage of urban and rural areas for proper sanitation; and the control of water, soil, and atmospheric pollution, and the social and environmental impact of public health, such as control of anthropod-borne diseases, the elimination of industrial health hazards, and the provision of adequate sanitation in urban, rural, and recreational areas, and the effect of technological advances on the environment. (ASCE)

More population - more food - more water - more of everything - more industrial goods - more wastes - more pollution!

 World population:

1900 - 1.6 billion1950 - 2.5 billion1980 - 5.0 billion2000 - 6.0 billion2110 - 10.5 billion (estimated)

Rate of population growth in developing countries is 40% greater than in the world as a whole.

Environmental impact of agriculture-related activities:

DesertificationDams and ecological disasters

Salinity problemsUse of fertilizersUse of pesticides

Animal wastes

Environmental impact of urbanization: Concentration of people

- increased demand on resources - increased volume of waste-waters - Production of solid wastes - Problems of residential environment - Slums - Air pollution

 Closely related to the influence of

industrialization! 

Environmental impact of industrialization:

Industrial wastewatersIndustrial solid wastesHazardous wastesGrowing numbers and complexity of wastesToxic, carcinogenic, cumulative and

synergistic chemicalsIncreased demand on resourcesProblems of occupational environment

IMPLEMENTING LAWS, RA’S, DECREES, AND LOCAL LAWS:Philippine Clean Air Act of 1999 (RA 8749)The Clean Air Act promoted cooperation and

self-regulation and pollution prevention as well as encouraging public participation to air quality planning and monitoring.

It advanced the formulation and enforcement of a system of accountability as regards environmental impact of a project, program or activity and converted the Environmental Management Bureau (EMB) as a line bureau and created the EMB Regional Offices.

Philippine Clean Water Act of 2004 (RA 9275) 

The Clean Water Act advanced the prevention, control, and abatement of pollution in water resources.

It encouraged that water quality management issues should not be separated from concerns on water sources and ecological protection, water supply, public health and quality of life.  

The Act thus endorsed management programs to address water pollution.

Environmental Impact Assessment (PD 1151)

RA 6969: Toxic Substances and Hazardous and Nuclear Wastes Control Act (1990)

- controlled toxic substances and hazardous and nuclear wastes by way of regulating, restricting or prohibiting the importation, manufacture, processing, sale, distribution, use and disposal of chemical substances and mixtures that present unreasonable risk and/or injury to health or the environment. It also prohibited the entry, even in transit, of hazardous and nuclear wastes and their disposal into the country.

RA 9003: Ecological Solid Waste Management Act (2000)This Act maximized the utilization of valuable

resources and encouraged resource conservation and recovery.

It promoted solid waste avoidance and volume reduction.

RA 9003 places the primary enforcement and responsibility of solid waste management with LGUs and encouraged cooperation and self-regulation among waste generators.

ENVIRONMENTAL SYSTEMS“SYSTEMS APPROACH” – looking at all inter-related parts and their effects on one another.

Three environmental systems:

•Water resource management system•Air resource management system•Solid waste management system

Many important environmental problems are not confined to one of these systems but cross boundaries from one to the other. These problems are referred to as MULTIMEDIA pollution problems.

WATER RESOURCE MANAGEMENT SYSTEM

WATER SUPPLY SUBSYSTEM

The components of a water supply system may include:

•collection works•transmission works•treatment works•distribution works

Two major sources of water supply:•Surface water – streams, lakes, and rivers•Groundwater – wells

Factors that influence water consumption:Consumer Groups:

•Domestic and public use•Industrial and commercial use•Livestock use•Waterworks use•Losses and wastes ('unaccounted for' water)•Fire demand

Factors influencing water use: •Size of city•Climate and location•Industrial development•Habits and living standards•Parks and gardens•Water quality•Water pressure•Cost of water

The following factors also influence water consumption:

•Extent of sewerage•Systems pressure•Water price•Availability of private wells

•Standard of living•Per capita water use increases with and increased in standard of living. Highly developed countries use much more water than the less developed nations. Likewise, higher socioeconomic status implies greater per capita water use hat lower socioeconomic status. Higher average annual temperature implies higher per capita water use, whereas areas of high rainfall experience lower water use.

Variations in water demand: •Average day demand•Maximum day demand•Maximum hour demand

Source: to meet average day demand or maximum day demand

Transmission from source to treatment plant: To meet average day demand or maximum day demand

Water treatment plant:To meet maximum day demand

Pumping plant: To meet maximum day demand (if feeding into reservoirs) Distribution system: to meet maximum hour demand or (maximum fire

demand + fire demand) whichever is greater.

A single family residence uses about 400 Lcpd (liters per capita per day).

The variation of demand is normally reported as a factor of the average day.

For metered dwellings the factors are as follows:

Maximum day = 2.2 x average day

Peak hour = 5.3 x average day

Problem 1. A small residential development of 28 houses is being planned. Assume that the average residential consumption applies, and that each house has three residents. Estimate the additional average daily water production in L/d that will have to be supplied by the city.

Solution: (28 houses)( 3 people/house)(400 Lcpd) = 33,600 L/d

Problem 2. If a faucet is dripping at a rate of one drop per second and each drop contains 0.150 milliliters, calculate how much water (in liters) will be lost in one year.

Solution:(0.150 mL/s)(86,400 s/d)(365 d/y)(1 x 10-3

L/mL) = 4,730 L/y

Problem 3. A sanitary landfill has available space of 16.2 ha at an average depth of 10 m. Seven hundred sixty five (765) cubic meters of solid waste are dumped at the site five days per week. This waste is compacted to twice its delivered density. Draw a mass-balance diagram and estimate the expected life of the landfill in years.

Solution: Compaction to twice delivered density means that the volume is reduced to ½. The annual volume of compacted solid waste is:

(5 d/wk)(52 wk/y)(765 m3/d)(1/2) = 99,450 m3/yThe available space:

(16.2 ha)(1 x 104 m3/ha)(10 m depth) = 1,620,000 m3

The expected life of the landfill is:1,620,000 m3 / 99,450 m3/y = 16.3 years

A materials balance approach to problem solving

Matter can neither be created nor destroyed but that it can be changed in form. This concept serves as a basis for describing and analyzing environmental engineering problems. This concept is called a materials balance, or a mass balance.

In environmental system or subsystem, the equation would be written:

ACCUMULATION = INPUT – OUTPUT

EX. Mr. and Mrs. Consumer have no children. In an average week they purchase and bring into their house approximately 50 Kg of consumer goods (food, magazines, newspapers, appliances, furniture, and assorted packaging). Of this amount, 50% is consumed as food. Half of the food is used for biological maintenance and ultimately released as CO2; the remainder is discharged to the sewer system. Approximately 1 Kg accumulates in the house. The couple approximately recycles 25% if the solid waste that is generated. Estimate the amount of solid waste they place at the garbage cab each week.

Solution:

Mass balance equation:Input = Output 1 + output 2 + output 3 + output 4 + accumulation

One half of input is food = (0.5)(50 Kg) = 25 kg

One half of food is for biological maintenance = output 1 = (o.5)(25 Kg) = 12.5 Kg

One half of food is lost to sewer system = output 2 = (0.5)(25 kg) = 12.5 kg

The recycled amount is 25 percent of what remains of input after food and accumulation is removed = Output 3 = 0.25( input –output 1 – output 2 – accumulation) = 0.25(50 – 12.5 -12.5 – 1) = 6 kg

Output 4 = input – output 1 – output 2 – output 3 – accumulation= 50 – 12.5 – 12.5 – 6 – 1= 18 Kg

HYDROLOGYThe continuous circular process, in which the water of the Earth

evaporates from the oceans, condenses, falls to the Earth as rain or snow, and eventually returns to the oceans through run-off in rivers or streams. Some water is absorbed by plants and returned to the atmosphere as vapor.

Description

The water cycle has no starting or ending point. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. Rising air currents take the vapor up into the atmosphere, along with water from evapotranspiration, which is water transpired from plants and evaporated from the soil. The vapor rises into the air where cooler temperatures cause it to condense into clouds. Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Snowpacks in warmer climates often thaw and melt when spring arrives, and the melted water flows overland as snowmelt. Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers. Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers (saturated subsurface rock), which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as ground-water discharge, and some ground water finds openings in the land surface and emerges as freshwater springs. Over time, the water continues flowing, some to reenter the ocean, where the water cycle renews itself.

The different processes are as follows:

•Precipitation is condensed water vapor that falls to the Earth's surface. Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet. Approximately 505,000 km³ of water fall as precipitation each year, 398,000 km³ of it over the oceans.

•Canopy interception is the precipitation that is intercepted by plant foliage and eventually evaporates back to the atmosphere rather than falling to the ground.

•Snowmelt refers to the runoff produced by melting snow.

•Runoff includes the variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may infiltrate into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

•Infiltration is the flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.

•Subsurface Flow is the flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface (eg. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at lower elevation than where it infiltrated, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.

•Evaporation is the transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere. The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Approximately 90% of atmospheric water comes from evaporation, while the remaining 10% is from transpiration. Total annual evapotranspiration amounts to approximately 505,000 km³ of water, 434,000 km³ of which evaporates from the oceans.

Sublimation is the state change directly from solid water (snow or ice) to water vapor.

Advection is the movement of water — in solid, liquid, or vapour states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.

Condensation is the transformation of water vapour to liquid water droplets in the air, producing clouds and fog. 

TRANSPIRATION

Loss of water from a plant, mainly through the stomata of leaves. Darkness, internal water deficit, and extremes of temperature tend to close stomata and decrease transpiration; illumination, ample water supply, and optimum temperature cause stomata to open and increase transpiration. Its exact significance is disputed; its roles in providing the energy to transport water in the plant and in aiding dissipation of the sun's heat (by cooling through evaporation of water) have been challenged. Since stomatal openings are necessary for the exchange of gases, transpiration has been considered by some to be merely an unavoidable phenomenon that accompanies the real functions of the stomata.

•EVAPOTRANSPIRATION

(ET) is a term used to describe the sum of evaporation and plant transpiration from the earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapour through stomata in its leaves. Evapotranspiration is an important part of the water cycle.

•Potential evapotranspiration (PET)

Is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile. It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour from the ground up into the lower atmosphere. Evapotranspiration is said to equal potential evapotranspiration when there is ample water.

AQUIFER 

In hydrology, a rock layer or sequence that contains water and releases it in appreciable amounts. The rocks contain water-filled pores that, when connected, allow water to flow through their matrix. A confined aquifer is overlain by a rock layer that does not transmit water in any appreciable amount or that is impermeable. There probably are few truly confined aquifers. In an unconfined aquifer the upper surface (water table) is open to the atmosphere through permeable overlying material. An aquifer also may be called a water-bearing stratum, lens, or zone.

Volume of water stored inthe water cycle's reservoirs

Reservoir Volume of water([[1 E+15 m³|106 km³]])

Percentof total

Oceans 1370 97.25Ice caps & glaciers 29 2.05Groundwater 9.5 0.68Lakes 0.125 0.01Soil moisture 0.065 0.005Atmosphere 0.013 0.001Streams & rivers 0.0017 0.0001Biosphere 0.0006 0.00004

Reservoirs

In the context of the water cycle, a reservoir represents the water contained in different steps within the cycle. The largest reservoir is the collection of oceans, accounting for 97% of the Earth's water. The next largest quantity (2%) is stored in solid form in the ice caps and glaciers. The water contained within all living organisms represents the smallest reservoir.The volumes of water in the fresh water reservoirs, particularly those that are available for human use, are important water resources.

The hydrologic equation:The total quantity of water available to the earth is finite, the global hydrologic system is considered to be a closed system: that is self-contained or in mass balance.

VP(ρ) – Vs(ρ) – VR(ρ) – VG(ρ) – VE(ρ) – VT(ρ) = 0

Where:V = volume P = precipitation S = storage R = runoff G = groundwater infiltration E = evaporation T = transpiration ρ = density

Infiltration: (Horton’s equation)

f = fC + (fO – fC)e-kt

Where:f = infiltration rate, mm/hfC = equilibrium or final infiltration rate, mm/h

fO = initial infiltration rate, mm/h

k = empirical constant, h-1

t = time, h

Note: rate of precipitation > rater of inflation

Evaporation:

E = (es – ea)(a + bu)

Where:E = evaporation rate, mm/hes = saturation vapor pressure, kPa

ea = vapor pressure in overlying air, kPa

a , b = empirical constantsu = wind speed, m/s

Note: high wind speeds and low humidities result in large evaporation rates.

WATER TREATMENT

Water can be consumed in any desired amount without concern for adverse health effects in termed to be potable water. Potable water does not necessarily mean that the water tastes good. In contrast, palatable water, which is one that is pleasing to drink, but not necessarily safe. Water should be both potable and palatable.

As population increase, so must water production. Often increased production requires the use of new water sources that contain higher contaminant levels. As production increases while plant capacity remains the same, the task of producing potable water increasingly difficult.

Water pollutants

OUR BODY DEPENDS UPON WHAT YOU DRINK!

Information states that there is some kind of toxic substance in our ground water no matter where we live. Even materials added to our drinking water to "protect" us (such as chlorine) are linked to certain cancers, and can form toxic compounds (THM's) which adversely affect us. The old adage "If you want something done, do it yourself" applies to our drinking water also.

BIOLOGICAL IMPURITIES:

Bacteria, Virus, and Parasites -- Years ago, waterborne diseases accounted for millions of deaths. Even today in underdeveloped countries, an estimated 25,000 people will die daily from waterborne disease. Effects of waterborne microorganisms can be immediate and devastating. Therefore, microorganisms are the first and most important consideration in making water acceptable for human consumption.

Generally speaking, modern municipal supplies are relatively free from harmful organisms because of routine disinfection with chlorine or chloramines and frequent sampling. This does not mean municipal water is free of all bacteria. Private wells and small rural water systems have reason to be more concerned about the possibility of microorganism contamination from septic tanks, animal wastes, and other problems.

INORGANIC IMPURITIES:

Dirt and Sediment or Turbidity -- Most waters contain some suspended particles which may consist of fine sand, clay, soil, and precipitated salts. Turbidity is unpleasant to look at, can be a source of food and lodging for bacteria, and can interfere with effective disinfection.

Total Dissolved Solids -- These substances are dissolved rock and other compounds from the earth. The entire list of them could fill this page. The presence and amount of total dissolved solids in water represents a point of controversy among those who promote water treatment products. Here are some facts about the consequences of higher levels of TDS in water:

1. High TDS results in undesirable taste which could be salty, bitter, or metallic.

2. High TDS water is less thirst quenching.

3. Some of the individual mineral salts that make up TDS pose a variety of health hazards. The most problematic are Nitrates, Sodium, Sulfates, Barium, Copper, and Fluoride.

4. The EPA Secondary Regulations advise a maximum level of 500mg/liter (500 parts per million-ppm) for TDS. Numerous water supplies exceed this level. When TDS levels exceed 1000mg/L it is generally considered unfit for human consumption.

5. High TDS interferes with the taste of foods and beverages, and makes them less desirable to consume.

6. High TDS make ice cubes cloudy, softer, and faster melting.

7. Minerals exist in water mostly as INORGANIC salts. In contrast, minerals having passed through a living system are known as ORGANIC minerals. They are combined with proteins and sugars. According to many nutritionists minerals are much easier to assimilate when they come from foods. Can you imagine going out to your garden for a cup of dirt to eat rather than a nice carrot; or drinking a whole bathtub of water for LESS calcium than that in an 8 ounce glass of milk?

8. Water with higher TDS is considered by some health advocates to have a poorer cleansing effect in the body than water with a low level of TDS. This is because water with low dissolved solids has a greater capacity of absorption than water with higher solids.

Toxic Metals or Heavy Metals -- Among the greatest threats to health are the presence of high levels of toxic metals in drinking water - Arsenic, Cadmium, Lead, Mercury, and Silver. Maximum limits for each are established by the EPA Primary Drinking Water Regulations. Other metals such as Chromium and Selenium, while essential trace elements in our diets, have limits imposed upon them when in water because the form in which they exist may pose a health hazard. Toxic metals are associated with nerve damage, birth defects, mental retardation, certain cancers, and increased susceptibility to disease.

Asbestos -- Asbestos exists as microscopic suspended mineral fibers in water. Its primary source is asbestos-cement pipe which was commonly used after World War II for city water supplies. It has been estimated that some 200,000 miles of this pipe is presently in use to transport our drinking water. Because these pipes are wearing, the deadly substance of asbestos is showing up with increasing frequency in drinking water. It has been linked with gastrointestinal cancer.

Radioactivity -- Even though trace amounts of radioactive elements can be found in almost all drinking water, levels that pose serious health hazards are fairly rare--for now. Radioactive wastes leach from mining operations into groundwater supplies. The greatest threat is posed by nuclear accidents, nuclear processing plants, and radioactive waste disposal sites. As containers containing these wastes deteriorate with time, the risk of contaminating our aquafers grows into a toxic time bomb.

ORGANIC IMPURITIES: Tastes and Odors -- If your water has a disagreeable taste or odor, chances are it is due to one or more of many organic substances ranging from decaying vegetation to algae; hydrocarbons to phenols. It could also be TDS and a host of other items.

Toxic Organic Chemicals -- The most pressing and widespread water contamination problem is a result of the organic chemicals created by industry.

Chemicals end up in our drinking water from hundreds of different sources. There are hundreds of publications each year highlighting this problem. The effects of chronic long term exposure to these toxic organics, even in minute amounts, are extremely difficult to detect. Contaminated drinking water may look and taste perfectly normal. The users symptoms might include recurring headache, rash, or fatigue - all of which are hard to diagnose as being water related. The more serious consequences of drinking tainted water are higher cancer rates, birth defects, growth abnormalities, infertility, and nerve and organ damage. Some of these disorders may go unnoticed for decades!! Just how toxic these chemicals are may be illustrated by looking at two examples: TCE is a widely used chemical which routinely shows up in water supplies. Just two glassfuls of TCE can contaminate 27,000,000 gallons of drinking water! One pound of the pesticide, Endrin can contaminate 5,000,000,000 gallons of water.

Chlorine -- Trihalomethanes (THM's) are formed when chlorine, used to disinfect water supplies, interacts with natural organic materials (e.g. by-products of decayed vegetation, algae, etc.). This creates toxic organic chemicals such as chloroform, and Bromodichloromethane. A further word about chlorine: Scientists at Colombia University found that women who drank chlorinated water ran a 44% greater risk of dying of cancer of the gastrointestinal or urinary tract than did women who drank non-chlorinated water! Chlorinated water has also been linked to high blood pressure and anemia. Anemia is caused by the deleterious effect of chlorine on red blood cells.

WATER QUALITYPrecipitation in the form of rain, hail, or sleet contains very few impurities. It may contain trace amounts of mineral matter, gases, and other substances at it forms and falls through the earth’s atmosphere. The precipitation, however, has virtually no bacterial content.Groundwater, therefore, often contains more dissolved minerals than surface water.The following four categories are used to describe drinking water quality:

Physical: Physical characteristics relate to the quality of water for domestic use and are usually associated with the appearance of water, its color or turbidity, temperature, and, in particular, taste and odor.Chemical: Chemical characteristics of waters are sometimes evidenced by their observed reactions, such as the comparative performance of hard and soft waters in laundering. Most often, differences are not visible.Microbiological: Microbiological agents are very important in their relation to public health and may also be significant in modifying the physical and chemical characteristics of water.Radiological: Radiological factors must be considered in areas where there is a possibility that the water may have in contact with radioactive substances. The radioactivity of the water is of public health concern in these cases.

GROUND SURFACEConstant composition Varying composition

High mineralization Low mineralization

Little turbidity High turbidity

Low or no color Color

Bacteriologically safe Microorganism present

No dissolved oxygen Dissolved oxygen

High hardness Low hardness

H2S, Fe. Mn Tastes and odors

Possible chemical toxicity

General characteristics of groundwater and surface water

TREATMENT SYSTEM

Treatment plants can be classified a simple disinfection, filter plants, or softening plant. Public Water Systems

Public Water Systems (PWSs) come in all shapes and sizes, and no two are exactly the same. They may be publicly or privately owned and maintained. While their design may vary, they all share the same goal - providing safe, reliable drinking water to the communities they serve. To do this, most water systems must treat their water. The types of treatment provided by a specific PWS vary depending on the size of the system, whether they use ground water or surface water, and the quality of the source water.

Tapping a Source of Water

Large-scale water supply systems tend to rely on surface water sources, while smaller systems tend to rely on ground water. Around 35 percent of the population served by community water systems (CWSs) drink water that originates as ground water. Ground water is usually pumped from wells ranging from shallow to deep (50 to 1,000 feet). The remaining 65 percent of the population served by CWSs receive water taken primarily from surface water sources like rivers, lakes, and reservoirs.

Treating Raw Water

The amount and type of treatment applied by a PWS varies with the source type and quality. Many ground water systems can satisfy local as well as national government requirements without applying any treatment, while others need to add chlorine or additional treatment. Because surface water systems are exposed to direct wet weather runoff and to the atmosphere and are therefore more easily contaminated, regulations require that these systems treat their water.

Water suppliers use a variety of treatment processes to remove contaminants from drinking water. These individual processes may be arranged in a "treatment train" (a series of processes applied in sequence). The most commonly used processes include filtration, flocculation and sedimentation, and disinfection for surface water. Some treatment trains also include ion exchange and adsorption. Water utilities select a combination of treatment processes most appropriate to treat the contaminants found in the raw water used by the system.

Water Treatment Plant