BUILDING UTILITIES 1 Fundamentals of Water Supply Systems

WATER BASICS Water and its appropriate use

‒ important part of design, especially the design of green buildings

‒ every building designed today is supplied with potable water

‒ most of this clean water is used to carry away organic waste

‒ impact on a wide range of design affecting bathroom fixtures arrangement, and the overall plans of large and complex water and sewage treatment facilities

‒ THE NEXT GREAT WORLD CRISIS WILL BE WATER SUPPLY

USES OF WATER • Nourishment • Cleansing and Hygiene • Ceremonial uses • Transportation • Cooling • Ornamental uses

– Reflectivity – Liquidity – Life-sustaining potential

• Protective uses

Water source Water volume, in cubic miles

Water volume, in cubic kilometers

Percent of freshwater

Percent of total water

Oceans, Seas, & Bays

321,000,000 1,338,000,000 -- 96.54

Ice caps, Glaciers, &

Permanent Snow

5,773,000 24,064,000 68.6 1.74

Ground water 5,614,000 23,400,000 -- 1.69 Fresh 2,526,000 10,530,000 30.1 0.76 Saline 3,088,000 12,870,000 -- 0.93

Soil Moisture 3,959 16,500 0.05 0.001 Ground Ice & Permafrost

71,970 300,000 0.86 0.022

Lakes 42,320 176,400 -- 0.013 Fresh 21,830 91,000 0.26 0.007 Saline 20,490 85,400 -- 0.007

Atmosphere 3,095 12,900 0.04 0.001 Swamp Water 2,752 11,470 0.03 0.0008

Rivers 509 2,120 0.006 0.0002 Biological Water 269 1,120 0.003 0.0001

Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).

THE HYDROLOGIC CYCLE • Earth's water is always in movement and is

always changing states, from liquid to vapor to ice and back again.

• The process whereby water constantly circulates is called the natural water cycle, also known as the hydrologic cycle, and

• It describes the existence and the continuous movement of water on, above, and below the surface of the Earth.

• It is powered by about ¼ of the earth’s solar energy, and the water cycle has no starting point.

EVAPORATION • Heat energy from the sun causes water in

puddles, streams, rivers, seas or lakes to change from a liquid to a water vapor.

• This is called evaporation.

• The vapor rises into the air and collects in clouds.

CONDENSATION

• Water vapor collects in clouds. As the clouds cool the water vapor condenses into water drops.

• This is called condensation. • These drops fall to the earth as rain,

snow or hail.

PRECIPITATION

• Water falls to the earth from clouds mainly as rain, but sometimes as snow and hail.

• This is called precipitation.

TRANSPIRATION

• Transpiration is the process by which plants lose water out of their leaves.

• Transpiration gives evaporation a bit of a hand in getting the water vapor back up into the air.

Water for human consumption comes from one of two basic systems:

Water from a well to supply an individual residence, well water for farmstead properties, and well water for small public sector properties that include schools, public buildings, and small commercial enterprises.

Municipal water systems that provide potable water to a wide array of commercial property and domestic use buildings including apartments, condominiums, duplex housing, and single family dwellings.

ANATOMY OF A WATER SYSTEM

A water system has two primary requirements:

it needs to deliver adequate amounts of water to meet consumer consumption requirements plus needed fire flow requirements.

the water system needs to be reliable; the required amount of water needs to be available 24 hours a day, 365 days a year.

BASIC WATER SOURCES FOR WATER SYSTEMS

GROUND WATER SOURCES (WELLS) water is below ground level or below the earth’s surface. necessary to dig or bore a well in order to tap into the water

source; also generally referred to as a “well-water source.” it occupies the spaces between soil and rock particles.

− at a certain depth below the land surface, the spaces between the soil and rock particles can be totally filled with water, resulting in an aquifer from which ground water can be pumped and used by people.

some of the precipitation that falls onto the land infiltrates into the ground to become ground water. − Once in the ground, some of this water travels close to the land surface and

emerges very quickly as discharge into streambeds − because of gravity, much of it continues to sink deeper into the ground. − water moving downward can also meet more dense and water-resistant

non-porous rock and soil, which causes it to flow in a more horizontal fashion, generally towards streams, the ocean, or deeper into the ground.

What’s the difference between a flowing artesian well and an artesian well? An artesian well is a well that taps into a confined aquifer. Under artesian pressure, water in the well rises above the top of the

aquifer, but does not necessarily reach the land surface. A flowing artesian well is one that has been drilled into an aquifer

where the pressure within the aquifer forces the groundwater to rise above the land surface naturally without using a pump. Flowing artesian wells can flow on an intermittent or continuous

basis and originate from aquifers occurring in either unconsolidated materials such as sand and gravels or bedrock, at depths ranging from a few meters to several thousand meters. All flowing wells are artesian, but not all artesian wells are flowing

wells.

Well construction typically consists of three steps: well will be drilled to meet all well construction

standards in the area a trench is dug to connect the well to the system a well pump is selected that will raise water from the

well and deliver it to a storage tank, where it is held under pressure until needed

WELL CONSTRUCTION

WELLS AS SOURCES OF WATER • Bored wells

– Are dug with earth augers – usually less than 30m deep – Located in boulder-free sites that will not cave in – Diameter range is 50 to 760mm – Cased with metal, vitrified tile, or concrete

• Driven wells – Simplest and usually the least expensive – A steel drive-well point (32-50mm dia.) is fitted on the end

of the pipe sections and driven into the earth – Materials and drive-well points design vary according to

expected characteristics of the well site – A pilot hole is dug first, and the drive-well point and pipe

sections are lowered into it – Well is driven well below the water table

• Jetted wells – Require a source of water and a pressure pump – A washing well point is supplied with water under pressure

; this loosens the earth and allows the point and pipe to penetrate.

• Drilled wells – Require elaborate equipment of several types – Dug by either percussion method or rotary drilling method – Percussion method involves raising and dropping of a

heavy drill bit and stem – After being pulverized, water is added to the hole to form

a slurry, which is periodically removed – As drilling proceeds, a casing is also lowered

• Drilled wells – Rotary method uses a cutting bit at the lower end of a drill

pipe – A drilling fluid or pressurized air is constantly pumped to

the cutting bit to aid in the removal of earth particles – After the drill pipe is withdrawn, a casing is lowered into

position – Another method is the pneumatic hammer method which

combines the percussion and effect with a rotary drill bit

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

AUGERED OR BORED

CUTTING LIPS OF A ROTATING AUGER SHAVE OR CUT MATERIAL LOOSE FROM THE BOTTOM OF THE HOLE.

AUGER, DETACHABLE TUBULAR EXTENSIONS, AND A HANDLE FOR ROTATING.

AUGER MUST BE REMOVED FROM THE HOLE WHENEVER IT IS FULL OF CUTTINGS. THIS NECESSITATES UNCOUPLING EXTENSIONS.

EQUIPMENT IS SIMPLE AND CAN USUALLY BE FABRICATED OR ADAPTED LOCALLY. CANNOT PENETRATE HARD FORMATIONS. UNCOUPLING EXTENSIONS SLOWS WORK AT GREATER DEPTHS. USUALLY CANNOT BE USED BELOW THE WATER TABLE.

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

DRIVEN A POINT ON THE LOWER END OF A STRING OF PIPE ALLOWS THE PIPE TO PENETRATE AS IT IS DRIVEN ON THE UPPER END. NORMALLY ACCOMPLISHED BY ALTERNATELY RAISING AND DROPPING A WEIGHT USED AS A DRIVER.

DRIVE POINT WHICH USUALLY ALSO INCLUDES A WELL SCREEN ABOVE IT, SPECIAL DRIVE PIPE WITH COUPLINGS, DRIVE CAP, AND DRIVER.

MATERIAL IS NOT REMOVED FROM THE HOLE, BUT IS FORCED OUT LATERALLY AS THE DRIVE POINT IS FORCED THROUGH IT.

FAST AND SIMPLE. SPECIAL WELL POINTS AND HEAVY DRIVE PIPE MAY NOT BE AVAILABLE LOCALLY. HARD FORMATIONS CANNOT BE PENETRATED. LIMITED TO SMALL DIAMETERS, BUT MULTIPLE WELL POINTS MAY BE CONNECTED TO A COMMON PUMP.

METHOD HOW PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

JETTED A HIGH VELOCITY STREAM OF WATER COMING OUT OF THE BOTTOM OF A VERTICAL PIPE WASHES AWAY MATERIAL AHEAD OF IT AS IT IS LOWERED.

PIPE EQUIPPED WITH JETTING ORIFICE (S) AT LOWER END, COUPLINGS, SUITABLE PUMP (HAND. OR MOTOR POWERED), FLEXIBLE CONNECTION BETWEEN PUMP AND PIPE, AND SUPPLY OF WATER.

THE WATER USED FOR DRILLING RETURNS TO THE GROUND SURFACE BY HAY OF THE ANNULAR SPACE AROUND THE JETTING PIPE CARRYING THE MATERIAL REMOVED WITH IT.

FAST. CANNOT PENETRATE HARD FORMATIONS. DIFFICULTY IN BRINGING LARGE GRAVEL OR STONE TO THE SURFACE. DRILLING EQUIPMENT CAN BE FABRICATED LOCALLY, BUT A PUMP AND A SOURCE OF WATER ARE REQUIRED.

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

HYDRAULIC PERCUSSION

THE HOLE IS KEPT FULL OF WATER. THE ALTERNATE RAISING AND DROPPING OF A STRING OF PIPE EQUIPPED WITH A CUTTING BIT AT THE BOTTOM ALLOWS PENETRATION BY A COMBINATION OF MECHANICAL AND HYDRAULIC ACTION.

HOLLOW DRILL BIT WITH WATER INLETS AND A CHECK VALVE, STRING OF PIPE, DEVICES TO AID RAISING AND DROPPING. A MAN'S HAND OVER THE TOP OF THE DRILL PIPE MAY BE SUBSTITUTED FOR THE CHECK VALVE.

THE RAISING AND DROPPING ACTION IN CONJUNCTION WITH THE CHECK VALVE CAUSES WATER TO BE PUMPED UP THE INSIDE OF THE DRILL PIPE CARRYING THE CUTTINGS WITH IT.

EQUIPMENT CAN BE FABRICATED LOCALLY OR PURCHASED. WATER REQUIRED. TRADITIONALLY USED IN SOME AREAS, THUS UNDERSTOOD BY LOCAL WELL DRILLERS. HARD FORMATIONS CANNOT BE PENETRATED. DIFFICULTY IN BRINGING LARGE GRAVEL OR STONES TO THE SURFACE.

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

CABLE TOOL PERCUSSION

A HEAVY CYLINDRICAL WEIGHT EQUIPPED WITH A CUTTING EDGE AT THE BOTTOM AND WITH A ROPE OR CABLE ATTACHED TO THE UPPER END IS ALTERNATELY RAISED AND DROPPED. IMPACT PULVERIZED MATERIAL AT THE BOTTOM OF THE HOLE.

HEAVY DRILL BIT, ROPE OR GABLE, DEVICES TO AID RAISING AND DROPPING.

THE PULVERIZED CUTTINGS ARE MIXED INTO A SLURRY WITH WATER DURING DRILLING. THESE ARE REMOVED USING A BAILER.

ALL FORMATIONS CAN BE PENETRATED AT VARYING RATES. SOME WATER REQUIRED. COMMERCIALLY BUILT RIG IS EXPENSIVE AND REQUIRES CONSIDERABLE SKILL TO OPERATE, BUT A SIMPLE SET OF TOOLS CAN BE FABRICATED LOCALLY AND ADAPTED TO MAN OR MOTOR POWER.

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

BAIL DOWN A LONG, CYLINDRICAL BUCKET WITH A CHECK VALVE AT THE BOTTOM AND A ROPE OR CABLE ATTACHED TO THE TOP IS ALTERNATELY RAISED AND DROPPED IN A HOLE PARTIALLY FILLED WITH WATER. PENETRATION IS ACCOMPLISHED BY HYDRAULIC AND MECHANICAL ACTION.

BAILER, ROPE, DEVICES TO AID RAISING AND DROPPING.

SLURRY OF CUTTINGS AND WATER ENTER THE BAILER AS IT IS REPEATEDLY DROPPED. THESE ARE PREVENTED FROM LEAVING THE BUCKET BY THE CHECK VALVE. THE BUCKET IS RAISED TO THE SURFACE FOR EMPTYING.

EQUIPMENT CAN BE FABRICATED LOCALLY. FREQUENTLY USED IN CONJUNCTION WITH OTHER METHODS, SUCH AS PERCUSSION. HARD FORMATIONS CANNOT BE PENETRATED BY THE BAILER ALONE.

METHOD HOW

PENETRATION IS ACCOMPLISHED

MINIMUM EQUIPMENT REQUIRED

REMOVAL OF MATERIAL FROM

HOLE

ADVANTAGES & LIMITATIONS

HYDRAULIC ROTARY

A HOLLOW DRILL BIT WITH EITHER A FIXED CUTTING EDGE OR TOOTHED ROLLERS IS ROTATED AT THE BOTTOM END OF A STRING OF PIPE. MATERIAL IS SCRAPED, ABRADED OR CHIPPED AWAY BY MECHANICAL ACTION.

DRILL BIT, DRILL PIPE, CIRCULATING PUMP, DEVICE FOR ROTATING DRILL PIPE.

WATER OR "MUD" IS PUMPED DOWN THE HOLLOW DRILL STEM TO LUBRICATE THE BIT AND TO CARRY THE CUTTINGS UP TO THE SURFACE THROUGH THE ANNULAR SPACE AROUND THE DRILL PIPE. CIRCULATION MAY ALSO BE IN THE REVERSE DIRECTION.

COMMERCIALLY BUILT RIG IS EXPENSIVE AND REQUIRES CONSIDERABLE SKILL TO OPERATE. HOWEVER, SMALL ADAPTATIONS USING EITHER MAN POWER OR SMALL ENGINES HAVE BEEN DEVISED. A WATER SUPPLY IS NECESSARY. IT IS DIFFICULT TO DRILL IN LOOSE FORMATIONS.

SURFACE WATER SOURCES represent the second general classification of water supplies. water is taken from aboveground water sources that include both

large and small natural lakes, and high and low reservoir lakes formed by manmade dams to retain the water, rivers, and streams prior to use. − main uses of surface water include drinking-water and other public uses,

irrigation uses, and for use by the thermoelectric-power industry to cool electricity-generating equipment.

− majority of water used for hydroelectric power, public supply, irrigation, mining, and industrial purposes came from surface-water sources.

factors such as chemical and bacterial quality greatly influence the economics of water treatment and the physical quality of the water.

BASIC WATER SOURCES FOR WATER SYSTEMS

SURFACE WATER SOURCES divided into two distinct classifications, filtered and unfiltered.

‒ based on 1) type of treatment necessary to produce potable water, and 2) quality of such water prior to any required treatment process.

‒ unfiltered surface waters are delivered from a watershed area that is entirely owned or completely controlled by the water company or water authority. ‒ treatment of water derived from such a controlled watershed usually

consists of coarse screening and continuous chlorination. Preferred treatment would consist of fine screening, pressure sand filtration, pH adjustment, corrosion control, and continuous chlorination.

‒ filtered surface water sources require complete treatment and include those that are not entirely owned, supervised, or controlled by the water company or authority. ‒ water will contain normal bacteria content commonly associated to the

community life; proper treatment will render the water potable.

BASIC WATER SOURCES FOR WATER SYSTEMS

WATER SYSTEMS TYPES THAT SUPPLY WATER UNDER PRESSURE Gravity feed systems. Pumping pressure systems Each of these systems must:

‒ take water from a supply source, ‒ pass the water through a treatment plant, and then ‒ transport the water into the distribution system.

High or low reservoirs that hold non-potable water for gravity feed.

Pumping station systems that use ground water from streams, rivers, canals, man-made or

natural lakes, and other special provisions for impounding water.

raw water is pumped from the source point to the treatment plant and then either pumped directly into the distribution system or into storage to be used on demand by the community.

CLASSIFICATIONS OF COMMUNITY WATER SYSTEMS ACCORDING TO THE WATER SOURCE:

Pumps at well sites that pump water to the treatment facility. ‒ Based on the difference in elevation between the treatment

facility and the community to be served, the water may flow by gravity through the distribution systems, or there may be the need for another pumping station.

A combination of gravity flow and one or more pumping stations ‒ transport the water from the source point to all of the water

demand points on the distribution system. ‒ potable water flows by gravity from the storage tank to the

distribution system.

CLASSIFICATIONS OF COMMUNITY WATER SYSTEMS ACCORDING TO THE WATER SOURCE:

Water well pumps uses pressure or suctions to help raise the water from a low level to a high level. Selecting or sizing the well pump is a critical step in the construction of water wells. It is determined by the yield of the well and the needs of the system.

The general rule is to never install a pump that has a greater capacity than the well. ‒ The pump usually refers to both the pump itself and an electric motor, which

together make up the pumping unit. ‒ When the pump turns on, it fills the pressure tank used for water storage.

In the best and most economical water system, the needs of the system are less than the rate at which water can be drawn from the well.

If the peak demand exceeds the maximum rate of water available, the pump must be sized within the well capacity and the peak demand reached through added storage capacity. ‒ Usually a large-size pressure tank can perform this function. In fact, a larger

water storage tank can prolong the life of your pump, as it reduces the need for the pump to cycle as often.

ROLE OF THE WELL PUMP

Type of Pumps

Classified by operating principle

Pump Classification

Dynamic Positive Displacement

Centrifugal Special effect Rotary Reciprocating

Internal gear

External gear Lobe Slide

vane

Others (e.g. Impulse, Buoyancy)

Pumps

Dynamic Positive Displacement

Centrifugal Special effect Rotary Reciprocating

Internal gear

External gear Lobe Slide

vane

Others (e.g. Impulse, Buoyancy)

Pumps

WATER PUMPS • Positive displacement pumps

– There are 2 principal types: reciprocating pumps and rotary pumps • In reciprocating pumps, a plunger moves back and forth

within a cylinder equipped with check valves • The cylinder is located near or below the groundwater

level • Water enters the cylinder through an initial check valve • As the plunger moves toward this check valve, water is

forced through a 2nd check valve located within the plunger itself

• As the piston returns to its original position, water is forced upward toward the surface

WATER PUMPS • A rotary pump has a helical or spiral rotor – a turning

vertical shaft within a rubber sleeve • As the rotor turns, it traps water between it and the

sleeve, thus, forcing the water to the upper end of the rotor

WATER PUMPS • Centrifugal pumps

– This type contains an impeller mounted on a rotating shaft.

– The rotating impeller increases the water’s velocity while forcing the water into the casing, converting the water’s velocity into higher pressure

– Each impeller is called a stage; many stages can be combined in a multistage pump; there are two basic types of impellers: volute and turbine. o Turbine impellers are surrounded by diffuser vanes which provide

gradually enlarging passages in which the velocity of the water is slowly reduced thus transforming the velocity head into pressure head.

o Volute impellers are characterized by having no diffusion vanes. Instead, its impeller is housed in a case which is spiral shaped and in which the velocity of the water is reduced upon leaving the impeller, with resultant increase in pressure.

WATER PUMPS • Centrifugal pumps

– The number of stages depends upon the pressure needed to operate the water supply system, as well as the height to which the water must be raised

– Most common centrifugal pumps are those used in deep wells

WATER PUMPS • Centrifugal pumps

– There are 2 principal types of centrifugal pumps: turbine and submersible pumps • Turbine pump has a vertical turbine located below

groundwater level and a driving motor located higher up, usually over the well casing at grade; a long shaft is thus required between the motor and the turbine

– These pumps are usually used for high capacity from deep wells, up to 450m deep. The capacity and pressure depends on design, diameter, and number of impellers.

– The advantages are that it produces smooth, even flow and is easy to frost proof. The long drive shaft requires a straight and vertical well casing.

– The disadvantage is that the pump must be pulled from the well in order to repair it.

WATER PUMPS • Centrifugal pumps

• Submersible pumps are designed so that the motor can be submerged along with the turbine

– This type operates like a centrifugal pump except that several impellers are mounted together on a vertical shaft.

– The impellers and motor are in a housing which is positioned below the water level.

– Submersible pumps can lift from up to 300m deep. The pump capacity and pressure depends on diameter, speed, and number of impellers.

– The advantages to a submersible multistage pump is that they produce a smooth and even flow. They also have a short pump shaft to the motor.

– The disadvantage to this type of pump is that they are easily damaged by sand in the water, and repair requires pulling the pump out of the well.

WATER PUMPS • Jet pumps

– A venturi tube is added to the centrifugal pump – A portion of the water that is discharged from a

centrifugal pump at the wellhead is forced down to a nozzle and the venturi tube

– The lower pressure within the venturi tube induces well water to flow in and the velocity of the water from the nozzle pushes it up toward the centrifugal pump, which can then lift it more easily by suction

WATER SUPPLY

DESIGNER’S CONCERNS

Fundamental considerations for both designing and evaluating water supply systems. • Most important is to match the quality of

water to the task it will perform • The quantity of water required and provision

for the recycling of water • Specify plumbing fixtures that use less water

COMMON WATER QUALITY PROBLEMS and TREATMENT

PHYSICAL QUALITY OF WATER

Most noticeable aspects of water • Turbidity

– easy to see and a likely source of dissatisfaction for consumers – caused by presence of suspended materials such as clay, silt,

other inorganic material, plankton, or finely divided organic material

– even those materials that do not adversely affect health are usually aesthetically objectionable

• Color – another visible alteration – caused by dissolved organic matter, as from decaying vegetation – some inorganic materials also color water, as do microorganisms – usually do not threaten health, but they are often

psychologically objectionable

PHYSICAL QUALITY OF WATER

• Taste and Odor – can be caused by organic compounds, inorganic salts, or

dissolved gases – can be treated only after a chemical analysis has identified the

source • Temperature

– people expect drinking water to be cool – water supplied between 10O and 16OC is preferred

• Foamability – Caused by concentrations of detergents – Foam presence may not pose threat, but may indicate that

other more dangerous pollutants associated with domestic waste are also present

– Detergents must use linear alkylate sulfonate (LAS) which biodegrades rapidly – except in the absence of oxygen (lack of oxygen is a characteristic of septic tank drainage fields)

CHEMICAL QUALITY OF WATER

Water is an excellent solvent; groundwater is particularly subject to chemical alteration. • Alkalinity

– caused by bicarbonate, carbonate, or hydroxide components

– testing for these components is a key to determining which treatment to use

• Hardness – caused by calcium and magnesium salts – Can be classified as temporary (carbonate) or permanent

(non-carbonate) – Temporary hardness can be removed by heating the water;

permanent hardness cannot be removed by simple heating – inhibits the cleaning action of soaps and detergents – It deposits scale on the inside of hot water pipes and

cooking utensils

CHEMICAL QUALITY OF WATER

• pH – a measure of water’s hydrogen ion concentration,

as well as its relative acidity and alkalinity – a pH of 7 is neutral

• Toxic substances – occasionally present in water supplies – knowledge of acceptable concentrations of such

substances are a must

TOXIC SUBSTANCES IN WATER • Chlorides

– enter water as it passes through geologic deposits formed b marine sediment, or because of pollution from seawater, brine, or industrial or domestic wastes. A noticeable taste results from chloride in excess of 250mg/L.

• Copper – enter water from natural copper deposits or from copper piping

that contains corrosive water. Concentrations of copper in excess of 1.0mg/L can produce an undesirable taste

• Iron – is frequently present in water. Corrosive water in iron pipes will

also add iron to water. At concentrations above 0.3mg/L, iron can lend a brownish color to washed clothes and can affect the taste of water.

• Manganese – Can both pose a physiological threat and produce color and

taste effects similar to those produced by iron; recommended limit is 0.05mg/L.

TOXIC SUBSTANCES IN WATER • Nitrates

– In high concentration can pose a threat to infants (can cause “blue baby” disease). In shallow wells, concentrations can indicate seepage from deposits of livestock manure.

• Pesticides – A growing threat to water supplies; particularly common in

wells near homes that have been treated for termite control. • Sodium

– Primarily dangerous for people with heart, kidney, or circulatory ailments. Sodium in drinking water should not exceed 20mg/L. Some water softeners can raise sodium concentrations in water.

• Sulfates – Have laxative effects; can enter water groundwater from natural

deposits of magnesium sulfate or sodium sulfate. Concentrations should not exceed 250mg/L.

• Zinc – Sometimes enter groundwater in areas where it is found in

abundance. Although not a health threat, it can cause an undesirable taste at concentrations above 5mg/L.

BIOLOGICAL QUALITY OF WATER • Potable water should be free, as possible, of disease-producing

organisms – bacteria, protozoa, and viruses – these are not easily identifiable and a thorough biological water test is

complex and time-consuming. • Should be tested for one kind of bacteria – the coliform group ,

better known as E. coli. – always present in the fecal wastes of humans and which outnumbers

all other disease-producing organisms in water. – recommended maximum concentration is one organism/100mL of

water. • A water source should be chosen that does not normally support

much plant or animal life – Thus, groundwater is usually chosen over surface water as a source.

• The supply should be protected from subsequent biological contamination. – Human activities are frequently excluded from the watersheds.

• Organic fertilizers and nutrient minerals should also be kept out of the water supply to discourage biological activity.

• Stored water should be kept dark and at low temperatures. • Organisms are commonly destroyed at treatment facilities.

RADIOLOGICAL QUALITY OF WATER

• Mining of radioactive materials and the use of such materials in industry and power plants have produced radiological pollution in some water supplies.

• Because radiological effects are cumulative, concentrations of radioactive materials should be very low.

• “Safe” minimum concentrations have continually been revised downward for other radiation exposures.

Step 1: Screening Water passes through a series of screens designed to remove debris such

as twigs, leaves, paper, stones, and other foreign matter. Screens are frequently removed for cleaning or are back-washed from

high-pressure pumps to prevent clogging.

Step 2: Presedimentation While the water moves slowly through each reservoir, much of the sand

and silt settles to the bottom. Treatment lines and basins are shut down periodically during times of

minimum domestic consumption for cleaning. This applies to the portions of the physical plant described in Steps 2

through 8.

Step 3: Coagulation A coagulant, aluminum sulfate, is added to the water as it flows to

sedimentation basins. Coagulants aid in the removal of suspended particles in the water by

causing them to consolidate and settle.

HOW DRINKING WATER IS TREATED

Step 4: Flocculation The water is gently stirred with large paddles to distribute the coagulant. This takes approximately 25 minutes.

Step 5: Sedimentation The water flows into sedimentation basins where particles settle to the

bottom. After about 4 hours, roughly 85 percent of the suspended material settles

out.

Step 6: Filtration Water at the top of the basins flow to large gravity filters, traveling

through layers of small pieces of hard coal, sand, and gravel. The filters help remove smaller particles from the water.

HOW DRINKING WATER IS TREATED

Step 7: Disinfection This may be accomplished by these methods:

‒ Chlorine is added to kill bacteria and viruses. ‒ Ammonia also is added. ‒ The chlorine and ammonia combine to form chloramines compounds.

Step 8: Additives Depending on the quality of the water at this point, the following additives

may be injected into the water stream to accomplish the stated benefits: ‒ Fluoride is added to reduce tooth decay. ‒ Calcium hydroxide is added to reduce corrosion in the pipes and

equipment of the distribution system.

HOW DRINKING WATER IS TREATED