ERT 349 SOIL AND WATER

ENGINEERING

Water Quality

At the end of this topic, student should be able to:

1.Determine the sources of water pollution2.Analyze water quality parameter based on water quality standard3.Design the water treatment process

Outline

Introduction to Water QualityWater Pollution

Types Sources of Pollution Sources categories Eutrophication

Water Quality LegislationWater Quality ParameterWater Quality Treatment

Introduction

Most of the Earth’s surface is covered with water.

Our bodies, plants & animals are consist about 90% of water.

We can only survive a few days without water.

Water is an essential nutrient for all plants & animals

Water transports nutrients & carries away waste products.

Water cools the body

Water Pollution

The presence of a substance in the environment that because of its chemical composition or quantity prevents the functioning of natural processes and produces undesirable environmental and (human) health effects.

Types of water pollutant

1. Sediment2. Sewage/Domestic effluent3. Pathogen (Water-borne disease)4. Organic compound5. Inorganic/chemical compound6. Radioactive compound7. Thermal pollution

Sediment

Erosion causes loose soil to enter the waterways

Suspended sediment blocks sunlight to plants and reduces dissolved oxygen.

Sewage/ Domestic effluent

Sources of pollution

1. Agriculture Fertilizers, animal wastes, etc.

2. Municipal Waste Sewage, fertilizers, dumping into drainage

ditches, etc.

3. Industrial Waste Chemicals left over from manufacturing,

waste products, etc.

Pollution sources categories

Point sources Water pollution can be traced at specific spot

through drain, pipe and sewer Example: Industrial/ domestic treatment plant

Non-point sources Pollutants that enter bodies of water over

large areas rather than being concentrated at a single point of entry.

Example: Agricultural fertilizer runoff and sediments from construction.

Point sources and non-point sources

Eutrophication

Definition The enrichment of a lake or pond by inorganic

plant and algal nutrients such as phosphorus and nitrogen.

The additional nutrients are food for algae and fish, so the more eutrophic a lake is, the more living organisms it sustains.

When a lake becomes shallower from added sediment, even more plants can grow because the littoral area increases in overall percentage.

Eutrophication is a natural process that a lake goes through over hundreds to thousands of years.

Eutrophication is also sometimes referred to as lake aging.

Water Quality Indicator

PhysicalChemicalBiological

PHYSICAL INDICATOR ColourTaste and OdorTurbiditySuspended Solid

Colour

May be due to the presence of organic matter, metals (iron, manganese) or highly coloured industrial waste

Aesthetically displeasing

Taste and Odour

Mainly due to organic substances, biological activity, industrial pollution

Taste buds in the oral cavity specially detect inorganic compounds of metals like magnesium, calcium, sodium, copper, iron and zinc

Water should be free from objectionable taste and odour.

Turbidity

Turbidity refers to water clarity.Caused by suspended matter/sedimentHigh level turbidity shield and protect

bacteria from the action of disinfecting agents

Unit in NTU

Total Suspended Solid (TSS)

TSS is the measure of the sediment suspended in the

water.

TSS is related to turbidity.

Water with high TSS usually has high Total Dissolved Solids (TDS)

as well.

ORGANIC & CHEMICAL INDICATOR pHHardnessAlkalinity

Organic

Dissolved Oxygen (DO) The amount of oxygen gas dissolved in a

given volume of water at a particular temperature and pressure.

Organic

Biological Oxigen Demand (BOD) The amount of oxygen required by aerobic

microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage.

When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is being consumed by the bacteria.

Organic

Chemical Oxygen Demand (COD) A measure of the capacity of water to

consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite.

Another term that refers to COD is a measure of organic materials in a wastewater in terms of the oxygen required to oxidize the organic materials chemically.

pH

It is the measure of hydrogen ion concentration

Neutral water pH-7Acidic water has pH below 7 Basic water has pH above 7

Hardness

Capacity of water for reducing and destroying the lather of soap

It is total concentration of calcium and magnesium ions

Temporary hardness – Bicarbonates of Calcium and Magnesium

Permanent hardness – Sulphates, chlorides and nitrates of calcium and magnesium

Hardness

0 – 50 mg/l - soft50 – 150 mg/l - moderately hard150 – 300 mg/l - hard300 above - very hardSurface water is softer than ground

waterCauses encrustations in water supply

structures Note: heat can change hardness ->

forms scale on boilers, coffee pots

Alkalinity

Capacity to neutralise acidPresence of carbonates, bi-carbonates

and hydroxide compounds of Ca, Mg, Na and K

Alkalinity = hardness, Ca and Mg saltsAlkalinity > hardness - presence of

basic salts, Na, K along with Ca and Mg

Alkalinity < hardness – neutral salts of Ca & Mg present

Units expressed as CaCO32-

Iron

One of the earth’s most plentiful resource

High iron causes brown or yellow staining of laundry, household fixtures

Metalic taste, offensive odour, poor tasting coffee

Cause iron bacteria

Chloride

Causes Dissolution of salt deposit Discharge of effluents Intrusion of sea water

Not harmful to human beingsRegarding irrigation – most

troublesome anion

AmmoniaAmmonia is produced by the

decay of organic matter and animal waste.

Ammonia is toxic to most aquatic life, especially at high pH.

Bacteria readily convert ammonia to nitrate (a plant nutrient)

Ammonia is a form of nitrogen and part of the Nitrogen Cycle.

AmmoniaNitrogen Cycle

Nitrate

Increasing level of nitrate is due to Agricultural fertilizers, manure,animal dung,

nitrogenous material ,sewage pollutionCause blue baby diseases to infants

Phosphate •Phosphate’s concentrations in clean water is generally low; however, phosphorus is used extensively in fertilizer and other chemicals.

•The primary sources of phosphates to surface water are detergents, fertilizers, and natural mineral deposits.

•High levels of phosphate can over stimulate the growth of aquatic plants and algae.

•This in turn, will cause high DO consumption and death to fish and many aquatic organisms.

FluorideOccurs naturallyLong term consumption above

permissible level can cause – dental flurosis (molting of teeth)Skeletal flurosisRemedy

Deflouridation Mixing Fluride free water Intake of vitamin C,D, calcium, antioxidants

Arsenic

Occur in ground water from arseniferous belt

Industrial waste, agricultural insecticide

High arsenic causes various type of dermatological lesions, muscular weakness, paralysis of lower limbs, can also cause skin and lung cancer

Heavy Metals

Present as mineral in soil and rocks of earth

Human activities Battery – Lead & Nickel Textile - Copper Photography – Silver Steel production – Iron

Pesticides

These chemicals are very complex. Effect on aquatic organism

Cancer Birth defects Blood disorder Nervous disorder Genetic damage

BacteriaMost bacteria are important in nutrient and other organic cycles.

Excess nutrients cause algal blooms.

As algae die and decay, the high bacterial load rapidly consumes dissolved oxygen.

BIOLOGICAL

Certain types of bacteria indicate animal and human waste pollution.

Escherichia coli are coliform bacteria found in the intestines of warm-

blooded organisms. Most strains are harmless but one E. coli strain can cause severe diarrhea and kidney

damage.

Water Quality Legislation

Water Quality Legislation

Interim National Water Quality Standard (DOE, 1986) Surface Water Marine Water Drinking Water

Sources:

http://www.wepa-db.net/policies/measures/currentsystem/malaysia.htm

Environmental Quality Act, 1974 Environmental Quality (Sewage and Industrial

Effluent) Regulation, 1979• Standard A• Standard B

Table 1. Water Use Classes in the National Water Quality Standards

Class UsesCLASS I Conservation of natural environment water supply 1 -

practically no treatment necessary.Fishery 1 - very sensitive aquatic species

CLASS IIA Water Supply II - conventional treatment requiredFishery ll - sensitive aquatic species

CLASS IIB Recreational use with body contact

CLASS III Water Supply lll - extensive treatment requiredFishery lll - common, of economic value, and tolerant species livestock drinking

CLASS IV IrrigationCLASS V None of the above – Dead river

PARAMETER UNITCLASS

I IIA IIB III IV V

Ammoniacal Nitrogen mg/l 0.1 0.3 0.3 0.9 2.7 > 2.7

Biochemical Oxygen Demand mg/l 1 3 3 6 12 > 12

Chemical Oxygen Demand mg/l 10 25 25 50 100 > 100

Dissolved Oxygen mg/l 7 5 - 7 5 - 7 3 - 5 < 3 < 1

pH - 6.5 - 8.5 6 - 9 6 - 9 5 - 9 5 - 9 -

Colour TCU 15 150 150 - - -

Electrical Conductivity* µS/cm 1000 1000 - - 6000 -

Floatables - N N N - - -

Odour - N N N - - -

Salinity % 0.5 1 - - 2 -

Taste - N N N - - -

Total Dissolved Solid mg/l 500 1000 - - 4000 -

Total Suspended Solid mg/l 25 50 50 150 300 300

Temperature °C - Normal + 2 °C - Normal + 2 °C - -

Turbidity NTU 5 50 50 - - -

Faecal Coliform** count/100 ml 10 100 400 5000 (20000)a 5000 (20000)a -

Total Coliform count/100 ml 100 5000 5000 50000 50000 > 50000

Notes* = At hardness 50 mg/l CaCO3# = Maximum (unbracketed) and 24-hour average (bracketed) concentrationsN = Free from visible film sheen, discolouration and deposits

Sourse : EQR2006

National Water Quality Standards For Malaysia

Parameter Unit Standard A Standard B(i) Temperature °C 40 40(ii) pH Value   6.0 - 9.0 5.5 - 9.0(iii) BOD5 at 20°C mg/l 20 50(iv) COD mg/l 50 100(v) Suspended Solids mg/l 50 100(vi) Mercury mg/l 0.005 0.05(vii) Cadmium mg/l 0.01 0.02(viii) Chromium, Hexavalent mg/l 0.05 0.05(ix) Arsenic mg/l 0.05 0.10(x) Cyanide mg/l 0.05 0.10(xi) Lead mg/l 0.10 0.5(xii) Chormium, Trivalent mg/l 0.20 1.0(xiii) Copper mg/l 0.20 1.0(xiv) Manganese mg/l 0.20 1.0(xv) Nickel mg/l 0.20 1.0(xvi) Tin mg/l 0.20 1.0(xvii) Zinc mg/l 1.0 1.0(xviii) Boron mg/l 1.0 4.0(xix) Iron (Fe) mg/l 1.0 5.0(xx) Phenol mg/l 0.001 1.0(xxi) Free Chlorine mg/l 1.0 2.0(xxii) Sulphide mg/l 0.50 0.50

(xxiii) Oil and Grease mg/lNot detectable

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PARAMETER LIMITS OF EFFLUENT OF STANDARD A AND STANDARD B 

Water Treatment

Water Treatment

Water treatment is a process of removing contaminants from raw water to produce water that is chemically and bacteriological safe for human consumption. 

The water must also be aesthetically acceptable, free from apparent turbidity, colour, objectionable taste and odour. 

Water Treatment Process

Source: SAJ

Water Treatment Process

The conventional treatment plant comprises of the following processes:

1.Screening Floating debris such as woods, leaves,

aquatic plants and others are screened at the intake by coarse screen. After screening, the denser suspended matters are removed by allowing water to pass through chamber where it settles down to the bottom.

2. Aeration Raw water pumped from the intake is

mixed with air at the aerator. The aeration process provides oxygen from atmosphere for the oxidation of dissolved iron and manganese to their insoluble form thus enable their removal. The process also helps in the removal of taste and odour.

3. Coagulation / FlocculationCoagulants, usually alum, are added

leading to the formation of microscopic particles in water. This is followed by gentle agitation causing small particles in the water to collide and combine to become bigger settleable flocs.

4. SedimentationThe flocs are allowed to flow through the

sedimentation tank as uniform as possible for long enough period for them to settle. The clarified water will be collected from the top.

If the flocs are light, another process will apply. In this process minute air bubbles are introduced. The flocs will stick to the air bubbles and float to the top. The clarified water will be collected from the bottom.This process is called Dissolve Air Flotation.

5. FiltrationThe settled water then goes through filters

where the fine particles and bacteria are trapped. The clean water then goes to the clear water tank. The filters are backwashed regularly through a combination of agitation by air and water to ensure efficient operations.

6. Disinfection /pH AdjustmentIn the clear water tank, the water is

disinfected to destroy microorganism still remain in water after filtration. Gaseous chlorine or chlorine compound are normally used for disinfections. The pH is adjusted using lime or soda ash.  

7. Clear Water TankTreated water will be collected and kept in

Clear Water Tank for distribution.8. Water Supply DistributionFrom the clear water tank at the water

treatment plant, treated water is pumped through long pipelines to balancing reservoirs with sufficient height for distribution by gravity to service reservoirs in various demand centers. In areas where water is unable to be supplied by gravity, secondary pumping systems will be introduced. 

Alternative water quality treatment

Reverse Osmosis (RO)Membrane TreatmentUV SystemFiltration system

Ultrafiltration Biofiltration

Natural Treatment Wetland