QUIZ 3: WATER SUPPLY

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Water Quality

Water Quality

A measure of how good the water is, in terms of supporting beneficial uses or meeting its environmental values.

Once a year

Minimum frequency of physical/chemical test

Chemical aspect, Physical aspects, and Microbiological aspects

Components of water quality

Hardness, Alkalinity and Acidity, Carbon dioxide, Dissolved oxygen, Chemical oxygen demand, Organic nitrogen, Iron and Manganese, Toxic substances, Phenolic Compounds

Chemical Aspects

Representative Samples

Before deciding on the source, water quality tests should be conducted first through

Hardness

due primarily to calcium and magnesium carbonates and bicarbonates and calcium and magnesium sulfate and chloride

Alkalinity

refers to the water’s capacity to neutralize acids while acidity indicates the concentration of hydrogen ions in water, determining the water's pH level.

Carbon Dioxide

is naturally present in water as a result of respiration from aquatic organisms and the decomposition of organic matter. Carbonic acid formation and the presence of free CO2 causes corrosion

Dissolved Oxygen

refers to the amount of oxygen gas dissolved in water. It causes flat taste. Water devoid of oxygen may indicate an appreciable level of oxygen-consuming organic substances.

Chemical Oxygen Demand

A measure of the amount of organic content of water. High COD levels indicate significant pollution, particularly from organic substances that consume oxygen.

Organic Nitrogen

consists of nitrogen compounds in organic matter, such as proteins, amino acids, and urea. It is an essential nutrient for aquatic life but can lead to eutrophication (over-enrichment of water bodies with nutrients) if present in excess, promoting algal blooms and reducing oxygen levels.

Iron & Manganese

These are naturally occurring metals that cause staining of clothing and plumbing fixtures, clogging of strainers and screens, and rusting of metallic conduits.

Toxic Substances

include chemicals like heavy metals (lead, mercury, arsenic), pesticides, and industrial pollutants. These substances can be harmful to both aquatic life and human health, often causing chronic health issues if consumed or if water comes into prolonged contact with such substances.

Phenolic Compounds

are organic compounds that can be introduced into water through industrial discharges. These compounds can cause bad taste and odor in water, and at high concentrations, they can be toxic to aquatic life.

Turbidity, Color, Odor, Taste

Physical Aspects

Turbidity

It refers to the cloudiness or murkiness of water caused by suspended particles like silt, clay, algae, organic matter, and microorganisms. It affects the clarity of water and is measured in Nephelometric Turbidity Units (NTU).

Color

Can be due to dissolved or suspended substances such as algae, organic materials, and metals (like iron and manganese).

Odor

Is often a sign of contamination or the presence of dissolved gases or organic material.

Taste

is the presence of undesirable taste in water indicates the presence of contaminants. It is influenced by dissolved salts, metals, and other chemicals.

California bacteria

Primary indicator of fecal pollution

Parasitic Protozoa, Helminths, Entamoeba, Giardia

Other indicators of fecal pollution

Pathogens

can be removed by filtration or by disinfection

Chlorine

which is readily available and inexpensive, is the usual disinfectant

Multiple-tube Fermentation and Membrane Filtration Method

Basic method used for enumeration of coliform organisms

Multiple-tube Fermentation

Coliform density is estimated via a most probable number (MPN), which is generated using specific probability formulas

Membrane Filtration Method

A technique for testing water samples. Water is drawn through a special porous membrane designed to trap microorganisms larger than 0.45 μm.

The Philippine National Standards for Drinking Water 2017

-a policy established by the Department of Health (DOH) which prescribes the standards and procedures on drinking-water quality aiming to protect the public and consumer’s health

-provides the minimum standards for quality of potable water

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Standard Values

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Standard Values

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Standard Values

Rainwater

Can be utilized as an important source of water supply in areas where rain is well distributed throughout the year and where surface and groundwater are scarce

Rainwater harvesting

is the process of collecting and storing rainwater in a scientific and controlled manner for future use.

Indus Valley

A place where the earliest known infrastructure was found. which is located close to modern-day India, Pakistan, and Afghanistan, and dates back to 5,000 BC.

Rainwater Harvesting Benefits

✓ Environment-friendly, easy approach for water requirements

✓ Uses simple technologies that are inexpensive and easy to maintain

✓ Ideal solution for water supply in areas without adequate alternative water resources (good backup source to wells and municipal water)

✓ Increases ground water level and improves its quality

✓ Mitigates the effects of drought

✓ Reduces the runoff, which otherwise would flood storm water drains

5 mg/l

The cistern be treated after every rain with a chlorine compound of at least _____ chlorine.

Germany and Australia

Countries that use rainwater harvesting

Irrigation Use, Indoor (non-potable use), Whole house (potable use)

Uses of collected rainwater

Rain Barrels, Dry System, Wet System

Methods of collecting Rainwater

Dry System

This method is a variation of a rain barrel set-up, but it involves a larger storage volume.

Wet System

This method involves locating the collection pipes underground in order to connect multiple downspouts from different gutters.

Rainwater, Springs, Infiltration wells and Surface water supplies

Development of water sources

Springs

Are outcrops of groundwater that often appear as small water holes or wet spots at the foot of hills or along river banks

Find the source, Properly develop it, Eliminate surface water intrusion, Prevent animals from gaining access to the spring

To obtain satisfactory water

Flow

should be measured monthly for a year to determine the spring’s design yield.

Spring box

box is a watertight collecting box constructed of concrete, clay, or brick with one permeable side.

Infiltration Wells

-involves a simple means of obtaining naturally filtered water

-consists of a system of porous, perforated, or open-joint pipe or other conduit that drains to a receiving well

Surface water

Includes water from streams, rivers, lakes, ponds, seas and oceans.

Surface water

usually contains organic and inorganic minerals and needs expensive water treatment. And it should be avoided for rural water supplies.

Well

is a hole which has been dug, bored, driven, or drilled beneath the ground for the purpose of extracting ground water.

Unsaturated zone

zone immediately beneath the ground surface and contains both water and air in the voids and pores.

Saturated zone

zone where the voids are all filled with water. Water in this zone is referred to as groundwater

Water table

the boundary between the unsaturated zone and the saturated zone.

Unconfined Aquifer, and Confined Aquifer

Types of Aquifer

Unconfined Aquifer

-also called water table aquifer

⁃ are often shallow and the hydraulic pressure at its surface water level or water table is equal to atmospheric pressure

Confined Aquifer

- also called artesian aquifer

⁃ an aquifer is sandwiched between an upper impermeable layer and a lower impermeable layer

⁃ hydraulic pressure is greater than the atmospheric pressure

Shallow Wells, Deep Wells and Artesian Wells

CLASSIFICATION OF WELLS BASED ON AQUIFER TAPPED

20 meters

A well is considered shallow if it is less than ________ deep

Shallow Wells

✓could be unreliable and sometimes intermittent

✓usually more affected by contamination

Deep Wells

✓are over 20 meters deep

✓taps the deeper unconfined aquifer

✓not confined by an overlying impermeable layer

✓characterized by the presence of a water table

✓less susceptible to surface contamination

✓yield tends to be more reliable

Artesian Wells

✓Like deep wells but water is extracted from confined aquifer

✓confining impermeable layers are above and below the aquifer

Mechanical Blockage, Chemical Encrustation, Bacteriological Plugging

Typical Causes of Reduced Blockage

Mechanical Blockage

caused by corrosion by-products of the metal portions of the well which act to cover the openings of a well screen

Chemical Encrustation

the deposition of minerals on the well screen or gravel pack which act to restrict the movement of water into a well

Chemical Encrustation

caused by the precipitation of minerals dissolved in the groundwater due to changes in flow and/or pressure conditions at the well.

Bacteriological Plugging

-This is when microorganisms, such as bacteria, cause clogging problems in wells

⁃ Usually caused by types of iron-related bacteria

Chemical Treatment, and Physical Methods

Typical Methods of Well Rehabilitation

Chemical Treatment

✓The selected chemicals are placed in the well and agitated frequently for 24 to 72 hours.

✓The well is then pumped with water before a water test is given

Physical Methods

is a method where a brush is attached to the drill and used in the well to mechanically remove incrustations

Physical Methods

is a method that features a tool with an adjustable, multi-head, water- powered jet that lowers into the well and injects water at a high pressure, dislodging debris from the well

Well surging

is the repeated injecting and flushing out of water in a well system. With repeated flushing, the debris is washed away

High-pressure jetting, Well drilling rig, and Well surging

Physical Methods

Dug Wells, Driven Wells, Bored Wells, and Drilled Wells

TYPES OF WELLS BASED ON DESIGN

Dug Wells

⁃ are holes or pits dug manually into the ground to tap the water table

⁃ may be up to 15 meters deep, with diameter usually ranging from 1 meter to 1.5 meters

⁃ lined usually with concrete masonry, bricks, stones, or reinforced concrete

Driven Wells

like dug wells, they tap the shallow portion of the unconfined aquifers

Driven Wells

typically made using a specialized drilling rig called a "well driver" that is designed to pound a small diameter pipe or casing into the ground

Bored Wells

⁃ constructed with hand or power augers, usually into soft cohesive or non-caving formations that contain enough clay to support the boreholes

⁃ depth could be up to 15 meters

⁃ very prone to surface contamination

⁃ not applicable on hard consolidated materials and is not advisable on predominantly boulder formations

Drilled Wells

can extract groundwater from a much deeper level than the other types of wells

Percussion or Cable Tool Method, Rotary Drilling Method, Reverse-Circulation Rotary Drilling Method, Air Rotary Method, Down-the-hole Drilling Method

WELL DRILLING METHODS

Percussion or Cable Tool Method

⁃ a traditional method of drilling water wells that has been used for centuries

⁃ involves using a heavy chisel or bit attached to a cable or rope, which is repeatedly raised and dropped by a drilling rig to break up rock and soil and create a hole.

Rotary Drilling Method

was developed to increase drilling speeds and reach greater depths in most formations

Reverse-Circulation Rotary Drilling Method

Differs from the direct rotary in that the drilling fluid circulates in the opposite direction.

Air Rotary Method

air, with a small volume of water and surfactant (foam), serves as the fluid and excavation is accomplished exactly as is done in the conventional direct rotary method.

Down-the-hole Drilling Method

In this method, the percussion mechanism – commonly called the hammer assembly – is located directly behind the hammer bit.

Pumping “Safe Yield” Test and Water Quality Test

TESTS OF WELL SUITABILITY

Pumping “Safe Yield” Test

✓The well’s safe yield can be roughly determined by operating a test pump with capacity at least equal to the system peak demand and operating it for 24 to 48 hours.

✓After 24 hours pumping, the drawdown should be measured at several time intervals to determine if it has stabilized.

✓The pumping rate at a stabilized pumping water level is the so called maximum pumping level and the safe yield is about 60 - 80% of the figure

Water Quality Test

This is done to determine if the physical and chemical characteristics of the groundwater meet the parameters set by the PNSDW

Hydro-Geological Conditions

Refers to the geological and hydrological factors that affect the movement, availability, and quality of groundwater within an aquifer system.

Preliminary Design and Final Well Design

2 stages of well design

Preliminary Design

-prepared by an experienced professional or driller based on hydro-geologic information gathered before the drilling

⁃ the basis of the well drilling contract and the cost estimates

Final Well Design

⁃ the preliminary well design will be adjusted based on actual observations and findings on the specific site during the drilling period

⁃ during this stage, the design assumptions used are verified and become actual design parameter

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Objective of well design

Casing Diameter

could be either a straight casing or telescopic casing.

Well Screen

the intake portion of the well. The yield of a well depends greatly on the design and location of the screen.

Screen, and Slotted or perforated casing

Types of Well screen

Screen

The more expensive alternative and is necessary if the aquifer is composed of loose material such as fine sand, gravel or soft sandstone.

Slotted or perforated casing

Can be used when the aquifer formation is more consolidated

Slot openings

must be small enough to keep out sediment but permit easy entry of water into the well.

Screen or Perforations

must be placed adjacent to the aquifer.

Gravel Pack

The annular space between the well screen, well casing, and borehole wall is filled with gravel or coarse sand

Cement Grout

should be used to fill the upper 3m of the annular space between the casing and the bore hole to provide a seal against possible surface contamination.