Water Supply System Design & Demand

Water Supply System Design

• Water supply systems must account for future population and water demand rates across different sectors.
• Predicting future population can be done using these methods:
  • Arithmetical increase: Pn = P + nI, where P is the present population, I representes the average increase per decade and n represents the amount of elapsed decades.
  • Geometrical increase: Pn= P x ( 1+(Ig/100))^n Ig is the average incremental increase and n is the number of decades
  • Incremental increase: Pn= P+nI+ n(n+1)/2 x r; where r is the incremental increase

Water Demand Composition

• Public water demand encompasses water for domestic, public/civic, industrial, and commercial uses, acknowledging water system losses as well.

Water Consumption Factors

• Average per capita water consumption is about 135 liters per day but can vary due to several factors:
  • Living standards
  • Water supply access
  • Water cost
  • System losses including leakages and unmetered taps

Water Distribution System Losses

• Losses arise from leakage, overflow from service reservoirs, and issues in main and service pipe connections.
• Additional losses are seen on the consumer end, such as unmetered household supplies, under-registration of supply meters, and public taps.

Water Loss Percentages

• Well-maintained water systems total water loss is less than 20%.
• Partly metered and unmetered systems can see losses up to 50%.

Water Demand Variations

• Water demand changes based on the season, month, day, and hour.
• Seasonal variations reach 130%
• Monthly variations 140%
• Daily variations 180%
• Hourly variations 150% of the annual average daily consumption.

Water Supply Design Considerations

• Water supply systems are designed to manage water demand fluctuations, catering to each component's service needs.
• Distribution mains require the largest capacity to handle maximum hourly demand.

Desirable Water Qualities

• Water should be colorless, clear, have good taste and odor, and be reasonably soft.
• Water should be available in plentiful quantities and be cheap
• It should be free of suspended solids to prevent sediment deposits, and also free from disease-causing organisms, objectionable dissolved gases like H2S, but with sufficient dissolved oxygen.
• Free from harmful salts, objectionable minerals (iron, manganese, lead, arsenic, poisonous metals), and radioactive substances like radium
• Free from phenolic compounds, chlorides, fluorides, and iodine
• It should not lead to scaling and be non-corrosive

Learning Objectives

• Examine main water quality parameters
• Relate main impurities in water and water-borne diseases
• Understand objectives, structures, and procedures of water quality standards

Water Quality in Nature

• Finding pure H₂O in nature is impossible.
• Raindrops falling from clouds can be pure but contaminated with gasses and particles when hitting the ground.
• Chemically impure water may have a good taste and nutrition due to some minerals presence.
• Purity and suitability depend on the water source.

Water Source Qualities

• Underground water may contain dissolved matter from strata.
• Shallow wells are more prone to bacterial pollution than deep wells.
• Streams and rivers contain more organic matter, sewage, and industrial effluents than any source.

Common Impurities

• Suspended impurities such as microscopic substances cause turbidity.
• Dissolved impurities make water a good solvent but lead to bad tastes, hardness, and alkalinity.
• Colloidal impurities are electrically charged small particles that constantly shift and resist settling.

Common Impurities: Effects and Constituents

• Bacteria can cause some diseases.
• Algae and protozoa cause odor, color, and turbidity.
• Silt causes murkiness or turbidity.
• Calcium and Magnesium bicarbonate (Salt) causes alkalinity
• Calcium and Magnesium Carbonate (Salt)Alkalinity, hardness
• Calcium and Magnesium Sulphate (Salt) causes hardness. Calcium and Magnesium bicarbonate (Salt) causes hardness corrosion.
• Sodium bicarbonate (Salt) causes alkalinity and softening effect
• Sodium Carbonate (Salt) causes alkalinity and softening effect.
• Sodium Sulphate (Salt) cases water foaming in boiling
• Sodium Fluoride (Salt) can cause dental fluorosis or mottled enamel
• Sodium Chloride (Salt) impacts taste
• Iron oxide causes taste, red color, corrosiveness, and hardness.
• Manganese causes black or brown color
• Lead causes cumulative poisoning
• Barium has toxic effect on heart and nerves.
• Cadmium can be toxic, causing illness,
• Cyanide is fatal.
• Boron affects the central nerve system
• Selenium is highly toxic to animals, and fish
• Arsenic causes toxicity and poisoning.
• Silver causes discoloration of skin and eyes.
• Nitrates cause blue baby conditions, infant poisoning, causes color and acidity
• Vegetable dye is a common impurity.
• Oxygen is corrosive to metals
• Carbon dioxide causes acidity and corrosiveness.
• Hydrogen Sulphide causes odor, acidity, and corrosiveness.

Colors in Water

• Water may gain color from organic matter (leaves, peat, logs) in true solution or suspension.
• Water color determined using the Hazen, platinic chloride, Burgess, or cobalt scale via tintometer.
• If turbidity causes the color, suspended particles can be removed by centrifuging.
• Color intensity measured in arbitrary units on the cobalt scale.
• 1 mg of platinum cobalt in 1 liter of distilled water produces this color.
• Public water supply should not exceed 20, ideally less than 10.

Palatability Factors

• Taste and odor define palatability.
• Changes are due to mineral salts, tarry substances, industrial waste, domestic sewage, decomposing organic matter, microscopic organisms, phenols.
• Taste and odor are hard to quantify due to dependence on personal and atmospheric conditions.
• Odor measured with a threshold odor number.
• Threshold odor number equals the sample volume (cc) to add is added to100 cc odor-free water to produce a distinguishable diluted sample.
• Threshold odor number should be no higher than 3 for public water.

Odor Testing

• An odor test occurs by inhaling diluted distilled water samples (ratios of 1:1, 1:2, 1:3) via Osmoscope.
• Threshold odor is the first detectable odor, and fresh water addition is the odor-intensity or pO value.

Odor Intensity Scale

• Level zero indicates no perceptible odor.
• Level one indicates a very faint odor, detectable only to train observers. Level two indicates a faint odor, detectable to average person only if he is told.
• Level three indicates a distinct odor, readily detectable by most people.
• Levels four, five, and six indicate distinct, strong and intense, and extremely strong odors, respectively.

Temperature Importance

• Provided water should be between 10°C and 20°C; temperatures above 25°C are objectionable.
• Temperature impacts density, viscosity, vapor pressure, and surface tension.
• Temperature further affects saturation values of dissolved solids and gases.
• Biological Oxygen Demand (B.O.D.) and biological activities rely on water temperature.

Defining Turbidity

• Defined by the colloidal matter present in water, such as clay, loam, or microscopic organisms.
• Measure for the resistance of water to light passage.
• Estimated it against standard suspensions of a siliceous material such as Fuller's earth.
• The standard unit, produced by one part of Fuller's earth in a million parts of distilled water.
• Expressed terms of parts of suspended matter per million parts of water by weight (ppm).
• One ppm equals 1 mg per liter (0.001 g of solids/1000 g of water).
• Permissible turbidity of domestic water is 5 to 10 p.p.m.

Examination of Total Solids

• Measures suspended, dissolved, and colloidal solids separately.
• Total solids should be less than 500 ppm.
• High solid content signals contamination or excessive minerals.
• Suspend solids are estimated filtering and weighing retained solids.
• The filtered sample is evaporated, leaving dissolved and colloidal solids.
• Fixed solids or inorganic ash is the mineral matter.
• Organic matter burns when the remained solids are heated, leaving inorganic matter.

Chloride Examinations

• Determines the sodium chloride content.
• Rainwater contains minor amounts, whereas surface water is often polluted oil-field waste, salt water, and mineral deposits.
• Groundwater receives larger amounts from geological strata, sewage effluents, and waste to rivers.
• Common chloride content ranges 10 to 20 ppm
• Chloride detection is via titration, using silver nitrate with potassium chromate as indicator.

Water Hardness

• Water hardness is from calcium and magnesium carbonate, bicarbonates, chlorides, and sulfates.
• Total hardness is from temporary and permanent hardness components.
• Temporary is also 'carbonate hardness' is from calcium and magnesium carbonates and bi-carbonates—easily removed by boiling water or adding lime.
• Permanent or 'noncarbonate hardness' results from calcium and magnesium sulfates, chlorides, and nitrates, which resists boiling and require special treatments.
• Hardness is expressed in ppm or degrees.

Degree of Hardness

• Soft water is described as 0-55 ppm.
• Moderately hard water is about 100-200 ppm.
• Very hard water indicates levels up to 201-500 ppm.
• Measurement varies across English, French, and German units.
• English units: one degree equals 14.3 g of CaCO3/liter.
• French and German units are 1.43 and 0.83 times.

Understanding pH Value

• Pure water has equal hydroxyl (OH-) and hydrogen (H+) ion concentrations at 10⁻⁷ mol/L at 21°C.
• Acidic water is when there is increased presence of Hydrogen.
• Alkaline water is when when there is increased presence of Hydroxide OH-.
• A small concentration means the pH value is based on logarithm of reciprocal of hydrogen ion.
• Pure water has a pH value of 7.

pH Extremes and Effects

• A pH value of 0 indicates maximum acidity.
• A pH value of 14 indicates maximum alkalinity.
• Acidic water results in tuberculation
• Alkaline water results in incrustation on pipes.
• Potable water should measure between 6-9, optimally 7-8.5.

Metals and Chemical Substances: Iron

• Iron leads to hardness, bad taste, discoloration of clothes, and scaled water mains.
• Water with iron is ferruginous.

Metals and Chemical Substances: Manganese

• Manganese gives water a brownish-purplish tint, stains laundered items and plumbing fixtures, and impairs coffee/tea taste.
• Manganese is estimated by matching the permanganate pink.

Metals and Chemical Substances: Lead

• Lead is a cumulative poison causing serious injury or death via short or extended contact.
• A safe concentration level is below 0.05 mg/l.
• Presence is detectable through white precipitate creation via sulfuric acid.

Metals and Chemical Substances: Arsenic

• Chronic arsenic poisoning is often evasive and disabling.
• Arsenic removed through ion exchange equipment, using activated alumina or bone char.

Metals and Chemical Substances: Fluoride and Iodides

• Small concentrations are useful to the body
• Iodine (1 ppm) prevents goiter
• Fluorine (1.2 ppm) will prevent dental caries
• Excess concentrations (above 3 ppm) can cause dental fluorosis or mottled enamel.

Metals and Chemical Substances: Barium and Boron

• Barium is present in some mineral springs and carbonate salts. It has toxic effects on the heart, blood vessels, and nerves.
• Boron consumption in large amounts may damage the central nervous system, or protractedly, create borism or boron poisoning.

Metals and Chemical Substances: Cadmium

• Is highly toxic and contaminates water via electroplating plant waste or galvanizing operations.

Metals and Chemical Substances: Sodium and Potassium

• The body’s regulatory mechanism maintains constant sodium through urination/excretion.
• Sodium-containing fluids accumulating may cause oedema from heart, liver and kidney diseases.

Metals and Chemical Substances: Phenols

• Phenols come from trade waste, tarmac roads, gas liquors, and creosoted surfaces A 0.001 ppm concentration impacts water taste post-chlorination.
• Their removal constitutes a serious water treatment challenge.

Effects of Nitrogen in Water

• Nitrogen enters water often through agricultural processes.
• Nitrogen compounds include fertilizers, nitrate, urea and amines.
• Nitrogen itself is not harmful but causes environmental damage.
• Large amounts of nitrate cause oxygen depravation and fish deaths by providing additional nutrients and algae growith.
• Toxicity at low pH values is achieved by nitrification which oxidizes ammonia to nitrite and nitrate.
• Nitrate maximum is 10 mg/l
• Nitrite maximum is 1 mg/l High levels then can be converted by the body which creates nausea and stomach aches due to blood oxygen transport disruption of hemoglobin

Aquatic Plant

• Common aquatic plants are water weeds, mosses and liverworts, ferns and horsetails, and algae.
• Water Weeds block canal carrying capacity add organic matter upon death grow densely under favorable conditions
• Algae simple, photosynthetic plants have unicellular reproduction may microscopic/hundreds of meters, in size, within fresh/seawater bad taste & odor cause blockages w/ turbidity & color changes clog filtration beds

Aquatic Animals

• Fish amphibians, mussels, snails, crustace insects, spiders, etc, live in water.
• Occasionally worm parasites are complained about by water consumers
• Metazoa polyzoa can cause obstructions by clogging strainers meters, as well as reducing pipe bore and increasing friction losses
• Protozoa pathogens destroy bacteria, representing simplest life
• Some protozoa have the effect of amoebic dysentery which is long lasting from cysts that excret in bowel discharges in the infected
• They may also deposit onto utensils, and bathroom fittings

Aquatic Molds, Bacteria and Viruses: Fungi

• cable of growing in low pH environments as non-photosynthetic plants growing in large moist areas
• decomposition creates taste and odor water after death
• combination with bacteria, causes earthen, muddy musty Odors
• control is found through copper Suplhate or chlorine treatments

###. Aquatic Molds, Bacteria and Viruses: Viruses

• Can be controlled through copper sulphate.
• Viruses, in sizes from 10 to 500 um bypass certain filters, also causing the children respiratory and gastrointestinal issues

Aquatic Molds Bacteria and Viruses: Bacteria

• Single walled micro-organisms extract soluble food through it and convert it to new
• different based on oxygen and temperature, such as origin, shape type
• Oxygen requirements, classify aerobic and aerobic
• Cold vs Heat Sensititvity, allows dormant and survive extreme longevity
• Some tolerate high, other's Low pH

Aquatic Molds, Bacteria and Viruses: The Important Group

• Bacteria from animal and sewage exrement, with disease, intensional and faecal strepcocci subgroups

Problem causing types in Water Supply (bacterial)

• Iron bacteriasulour bacteria
• Pitting tubercularisation through liquification
• odor, forthing, taste, in water
• slimy reddish brown Deposits
• bacterial corrosion

Contamination: Diseases are common through water supply

• water is known to have waterbourne disease from dysentery, gastroenenties, through typhoid, paratyphoid, infectious hepatitis, and cholera
• contamination through bacteria can be from feaces urine, milk or eggs. - by flies
• Water, flies, human, may cause protozoal diseases
• viruses are likely infectious through contaminated water

Human Water Quality Needs

• Level of purity required are based on each specific human is and use case
• Standards determined by
• comparing quality factors
• chemical
• physical and
• microbilological characteristics to certain quality guidelines
• Intended to enable safe use
• based on acceptable assessed toxic levels

Ecosystem Water quality Needs

• maintenance of natural condiction or
• in a lesser amount, large withstanding ecosystesm, it's quality can withstand small changes physical chemichal composition
• Water degraded from human forces adapt from gradual subtle qualities, which until a dramatical shift might exist in the condition

Influences on surface and ground water quality

• Human
• minerals
• • weathering
• --atmospherics leaching hydrology biology
• different sources need different monitoring and parameter guidelines for quality control and standards

Water Source Quality Monitoring

• Deep groundwater: Dissolved solids like Iron, Hardensss and Manganese
• ---Bacteriological and toxic
• -ground and uplannd are similiar with the potential for toxic wells

Water Quality Standards: What is a guideline, Statues and rules

• Guideline - means of understanding a criteria for assessment
• Statues- known the the aact of parliament that dictates administration and its rules

The water quality's importance is determined by

Data Analysis and

• -sciencic judgments of the aquative impact,

• therefore criterias developed protect animals and people Standards based on use , discharge and circumstance or even backing. educated guesses,experimentation, health effects, and mathematical models

• The quality is based on already established of water is used by organization’s like WHO as the main standard, among other international

• In HKSAR it's based under Drinking Safety committee and Water Standard from 2021