KAAF UNIVERSITY COLLEGE

CIV 364 ENVIRONMENTAL QUALITY ENGINEERING

Course Outline

• Introduction to environmental quality engineering

• Air pollution

• Soil erosion and sedimentation control

• Storm Sewer Design

• Water and Sewage Treatment

Management of solid waste

• 1) Recycling 2)incinerators 3) Landfills

• Development of groundwater resource

• Groundwater pollution and control

Management of Hazardous and Toxic waste

• 1) acid Mine Drainage 2) Disposing of Nuclear and chemical waste

• 3) Bio-reclamation 4) insitu-vitrification

• Course work 30%, Exams 70%

WHAT IS INCLUDED IN ENVIRONMENTAL ENGINEERING

FUNDAMENTALS:

Mathematics, Physics, Chemistry, Microbiology,

Thermodynamics, Economics, Computing, Legal

Social Sciences and Geology

Applications:

Air Pollution Control, Erosion and sedimentation control, Hydrology, Solid waste, water quality, water and wastewater treatment, hazardous waste, groundwater resource management and groundwater pollution control.

Environmental Work is Multidisciplinary!!!!

What do we Protect & Conserve?

1

PROTECTION:

• Health of Humans, Animals, Plants, microorganisms

• Water and Water Supplies

• Surface water (rivers and lakes)

• Groundwater

• Coastal

RESOURCE CONSERVATION

• Raw materials & Natural resources, energy/fossil fuels, land consumption

What causes pollution?

Human Activity

• Municipal Wastewater and Solid Waste

• Land Development

• Material Consumption i.e. plastic bottles, newspapers etc.

Unsustainable Development

Water & Air

Water Quality

• Drinking water supply and treatment

• Waste water treatment

• Contaminated Runoff

Surface water quality

• Protection of fresh and marine habitats

Air Quality

• Particulate control

• Acid rain

• smog

2

Microbial analysis

Understanding the impact of microorganisms

• Pathogenic (disease-producing) bacteria synthesize toxic substances that cause disease symptoms. E.g., clostridium tetani causes tetanus. Botulism bacteria cause food poisoning. Viruses

• Most bacteria are harmless and many are beneficial. Bacteria are known to biodegrade toxic chemicals in soils and groundwater. There is the need to identify these microorganisms and make them work for us.

Solid and Hazardous waste

Solid waste management

• Landfill Design

• Recycling

• Incineration with energy recovery

Hazardous Waste

• Where does it come from?

• Industries such as chemical, pharmaceutical, electronics, metal smelting plants,

Coastal engineering

• 50% of world’s population lives within 50 miles or 75 kilometres of the coast.

• Sea water intrusion in fresh groundwater

• Sea level rise and beach erosion

• Impact of storms on coastal infrastructure and natural environment

JOB OPPORTUNITIES

Consulting

• Provide engineering services to Government and industry

Academia i.e. teaching and research

Government:

3

EPA, NADMO, ministry of science.

• develop and enforce regulations and also issue permit

• Design of treatment facilities and landfill sites

1. AIR POLLUTION

The quality of the air we breathe has a major impact on public health and safety.

Therefore it is important for various Governments of this global village to have regulations (EPA) which define the nation’s air quality goals (i.e., the levels of acceptable pollution which have a minimal effect of public health. The means to achieve these goals are expressed in the form of permissible emission levels.

Adequate air pollution control measures such as dust emission control are necessary to enhance public safety, health, welfare and comfort and to reduce damage to any property, residence or business. A large quantity of atmospheric dust triggers Asthma in children with breathing problems.

Economically, business are forced to close down because of dust emissions or newly painted residential or business building turn brown overnight and cars have to be washed daily.

Occasionally, temporary dust emissions are a nuisance than a health impact on the ambient atmosphere.

DEFINITION:

Air pollution may be defined as the presence in the atmospheric air of one or more contaminants or combinations thereof in such quantities and of such durations as may be injurious to human, animal or plant life, or property, or which interferes with the comfortable enjoyment of life or property or conduct of business.

2 TYPES OF AIR POLLUTION

A) Particulate matter—Dust and /or volcanic ashB) SmogC) Acid rainD) Noise

4

E) SmellF)

2 a. Particulate Matter –Dust

Fugitive Emissions

Causes

Dust particles are generated when wind speed exceeds 40 km/h. Sandy and silty soils tend to be the most susceptible. Increased traffic speed on new or un-tarred roads or large construction projects such as new sports arena also generate dust. Mining activities such as blasting or the illegal mining called ‘Galamasey’ are prime generators of fugitive emissions.

Plant emissions

The source of the dust emissions can be traced to a single point source, for example, cement plant, drilling and crushing of rocks at a quarry site. It is easy to control the dust emissions in plant emissions than in fugitive emissions.

PRACTICES TO CONTROL DUST

STAGING

Staging is sometimes called phasing. With staging, grading and stabilization are finished in one area before proceeding to the next. Staging allows the contractor to take advantage of the existing vegetation on the site which acts as a wind barrier.

Plan the stages or phases of development so that only areas which are actively under construction are exposed.

WIND BREAKS

Trees or other tall vegetation along the perimeter or intermittently across the site must be left in place to serve as wind barriers. The proper use of seeding and planting of grasses in open areas must be encouraged.

WATERING

Another temporary measure for controlling dust is to keep the bare soil moist by watering. New roadways from Tetteh Quarshie to Mallam or Accra /Kumasi road especially at Achimota and Dome areas may have to be watered continuously.

CHEMICAL BINDERS5

In addition to watering, chemical binders or surfactants can be sprayed on the soil surface. The chemical (emulsified asphalt, or bond coat or asphalt cement) penetrates in the soil and bonds the individual soil particles.

CONTROL OF VEHICLE SPEED

In a construction site, or on un-tarred roads in urban areas, it is imperative to control vehicular speed to reduce dust emissions.

2b. SMOG

CARBON MONOXIDE

Carbon Monoxide (CO) is a toxic gas produced in gasoline engines as a result of incomplete combustion of fuel. It is also a component of tobacco smoke. Its toxic effect occurs because it combines with haemoglobin (pigment of red blood cells responsible for the transport of oxygen) more effectively than oxygen. Furthermore, carbon monoxide does not dissociate readily from the haemoglobin. Thus, when a person breathes carbon monoxide, increasing quantities of haemoglobin become unavailable for oxygen transport, and the body cells soon suffer.

CARBON DIOXIDE (CO2))

Carbon dioxide is nontoxic gas which is produced in greater quantities from complete combustion of gasoline or diesel fuel engines.

A second important source of additional atmospheric carbon dioxide is global deforestation, the cutting of tens of millions of acres of forests each year.

A third source of carbon dioxide emission is coal burning or diesel power plants

Carbon dioxide is known as a major contributor to the greenhouse effect or global warming because it traps heat. Atmospheric carbon dioxide allows energy in the form of sunlight to enter but absorbs and holds that energy once it is converted to heat.

ACID RAIN

Acid rain is a pollution problem resulting from the oxidation of pyrite (FeS2)

6

Present in anthracite coal. When coals are burned to generate electricity, sulphur dioxide gases are produced and escape from stack exhausts to the atmospheric air.

SULPHUR DIOXIDE

Sulphur Dioxide is a heavy, colourless gas with an odour like a struck match. The gas combines easily with water vapour, forming aerosols of sulphurous acid H SO, a colourless, mildly corrosive liquid. This liquid may combine with oxygen in the air, forming the even more irritating and corrosive sulphuric acid (H SO).

Sulphur dioxide not only has a bad order, it can irritate the respiratory system. Exposure to high concentration for short period of time can constrict the bronchi and increase mucous flow, making breathing difficult for the elderly and asthmatics. Increased sulphur dioxide contributes to impaired visibility.

Oxidized Sulphur dioxide in the form of sulphuric acid easily injures many plant species and varieties.

Sulphur dioxide concentration accelerates the corrosion of metals. Sulphur oxides may also damage stone and masonry, paint,

STACK GAS DESULFURIZATION

Stack gas desulfurization is a collective term used to describe the processes involving removal of sulphur dioxide from stack exhausts.

IN-FLAME CLEAN-UP: In –flame clean-up, also called in-situ clean-up, involves desulfurization of the coal gas as the combustion takes place. In flame clean-up is accomplished by bringing the coal and limestone sorbent into intimate contact with one another to achieve desulfurization and sulphur capture as the combustion gases are being produced.

NITROGEN OXIDE

Short term exposure of medium to high concentration of nitrogen oxide can measurably decrease lung function. Long term lower level exposures can destroy lung tissue, leading to emphysema. Other effects are damaging the vegetation by killing plant tissue, deterioration of fabrics and corrosion of metals and reduction in visibility.

7

EROSION & SEDIMENTATION CONTROL

INTRODUCTION:

The problem of erosion and sediment control has plagued society since civilization. Early land clearing, logging and farming damaged many streams and rivers. Recently, construction activities such as vast networks of highways, sprawling subdivisions, massive shopping centres have caused serious erosion and sedimentation problems. Damage from erosion and sediment affects every citizen in Ghana. Erosion and sedimentation result in:

Loss of Fertile topsoil

Clogged ditches, culverts, and storm sewers that increase flooding

Muddy or turbid lakes and streams

Damage to plant and animals life

Structural Damage to buildings, roads and other structures.

Damage to aquatic habitats

Suspended sediments require costly filtration for municipal water supply.

What is Erosion?

Erosion is the process by which the particles of land surface are dislodged or detached and put in motion by the action of wind, water, ice, or gravity

Types of Erosion

8

GEOLOGIC EROSION

• Geologic erosion or natural erosion is the action of the wind, water, ice, and gravity in wearing away rock to form soil and shape the ground surface. It is a slow process that often goes unnoticed.

ACCELERATED EROSION

• Accelerated erosion is a speeding up of erosion due to human activity. Farming, construction, logging and mining are the principal causes of accelerated erosion. Construction removes protective natural vegetation and replaces it with impermeable surfaces like paving, concrete slabs and rooftops on the soil.

Types of Erosion

• Four types of soil erosion which can occur on exposed terrain:

SPLASH EROSION

• Splash erosion results when the force of raindrops falling on bare or sparsely vegetated soil detaches soil particles.

SHEET EROSION

• Sheet Erosion occurs when a uniform layer of soil are removed from the land surface and are easily transported in a thin layer, or sheet, by flowing water.

RILL EROSION

• Riling is another form of overland erosion. Evidence of rill erosion is the development of small grooves spaced fairly uniformly along the slope. It is caused when runoff is heavy and water concentrates in rivulets.

GULLIES

• Gullies form whenever ground or paved surfaces concentrate water into an area that cannot handle the flow

MAJOR CATEGORIES OF EROSION

Wind Erosion

• The amount of soil lost from wind erosion may not be realized because the soil particles disperse over a large area where they are not visible. Occasionally, sand dunes are formed in desert areas. In an urban area, the most damaging aspect of wind erosion is dust. Dust creates traffic

9

hazards, adds to cleaning costs, is abrasive to plant tissue, and blights the appearance of structures and other surfaces.

Water Erosion

• The effects of water erosion are usually more visible than wind erosion. One can readily see gullies, turbid or muddy water and sediment build-up. Runoff causes both stream channel erosion and overland erosion

PHYSICAL FACTORS AFFECTING EROSION

• Erosion is affected by several physical factors, the common ones are:

• Climate

• Vegetative Cover

• Slope Characteristics

• Soil

CLIMATE

• The climatic factors that influence erosion are rainfall amount, intensity, and frequency. The infiltration rate is the rate that water is absorbed into the soil. When rainfall exceeds the infiltration rate, runoff occurs.

• Temperature is another climatic factor influencing erosion.

SLOPE STEEPNESS AND LENGTH

• Slope steepness, length and roughness affect erodibility.

• Generally, the longer the slope the greater the potential for erosion. The greatest erosion potential is at the base of the slope, where runoff velocity is greatest and runoff concentrates.

• Slope Steepness, along with surface roughness, and the rainfall amount and intensity control the speed at which runoff flows down a slope. THE STEEPER the slope, the faster the water will flow and the greater potential for erosion.

SOILS

• Soils

• Physical characteristics of soil have a bearing on erodibility. Soil properties influencing erodibility include, texture, structure, and

10

cohesion. Texture refers to the size or combination of the individual soil particles.

• Three broad soil size classifications, ranging from small to large are clay, silt, and sand. Soils having a large amount of silt-sized particles are most susceptible to erosion from both wind and water. Soils with clay or sand-sized particles are less prone to erosion.

VEGETATIVE COVER

Vegetation is probably the most important physical factor influencing soil erosion. A good cover of vegetation shields the soil from the impact of raindrops. It was binds the soil together, making it more resistant to runoff. A vegetative cover provided organic matter, slows runoff, and filters sediment.

CONTROLLING RUNOFF AND EROSION ON CONSTRUCTION SITES

Storm water runoff is rain that does not infiltrate when it comes in contact with the soil. Runoff can carry several pollutants, including sediment, nutrients, oil, salt and toxic materials.

SCHEDULING

The first construction practice is scheduling. Scheduling is a planning process that provides a basis for implementing all control measures in a timely and logical fashion during construction.

SEEDING AND MULCHING AND VEGETATIVE BUFFERS

• Seed and mulch all areas that have no vegetative cover.

• Preserve vegetated buffer areas above and below the graded area.

SURFACE ROUGHENING & DIVERSIONS

• Decrease the rate of runoff by surface roughening. Horizontal grooves tend to spread runoff over the slope, slowing it down and allowing more of it to infiltrate into the soil.

• Diversions (channel) intercept runoff and divert the flow onto vegetation, or into a basin

What is Sedimentation?

11

• Sedimentation is the process whereby the detached particles generated by erosion are deposited elsewhere on the land or in our lakes, streams and wetlands.

SEDIMENTATION GENERATION

Sedimentation is the process in which particulate matter carried from its point of origin by either natural or human-enhanced processes is deposited elsewhere on land surfaces or in water bodies.

Sediment is a natural product of water erosion; however, the sediment load may be increased by human practices. Such enhanced sources of sediment in a watershed include vegetated stream banks and uncovered soil regions, including construction sites, deforested areas, and croplands. (Tarbuck et al, 1998)

Agent of Erosion CAUSING SEDIMENTATION

• Ice

• Wind.

• Water.

1. Activities that speed up sedimentation process2. Construction projects e.g. Sand winning, at Weija3. Poor practice of desilting e.g. Odawna4. Deforestation e.g. Charcoal production 5. Erosion e.g. uncovered water banks

EFFECTS OF SEDIMENTATION ON THE ENVIRONMENT

Ecological and Economic Impacts

• Excessive erosion can reduce the soil's inherent productivity, whereas the associated sedimentation can damage young plants and fill drainage ditches, lakes, and streams.

• Increased costs of removing sediment from roadways, roadside ditches, and surface-water supplies.

• One of the principal causes of degraded water quality and aquatic habitat is the depositing of eroded soil sediment in water bodies. Excessive amounts of sediment resulting from natural or human-induced causes can result in the destruction of aquatic habitat and a reduction in the diversity and abundance of aquatic life. Diversity and population size of fish species, mussels, and benthic (bottom-dwelling)

12

macro invertebrates associated with coarse substrates can be greatly reduced if the substrates are covered with sand and silt.

• Suspended sediment causes the water to be cloudy (turbid). Increased turbidity reduces light transmission (and hence photosynthesis), thereby polarizing the equilibrium of the ecosystem.

• Increased sediment in surface-water bodies (e.g., rivers, lakes, and reservoirs) may have an economic impact on public water systems that use them as a source of drinking water. High turbidity not only is aesthetically displeasing, but also interferes with disinfection of the water prior to it being pumped to customers. Communities whose water-supply source has become more turbid often invest millions of Ghana Cedis to upgrade their treatment facilities in order to remove the increased sediment load.

IMPORTANCE OF SEDIMENTATION

Safety Importance

• Eroded soils can enter water bodies and channels, raising water levels and blocking culverts. This can increase the chances for inundation of surrounding land.

• Sediment (soil that has been eroded) can get deposited onto streets and roads by vehicles leaving the site or by storm water runoff. When wet, these sediments can be dangerous for drivers and other users of the road.

ENVIRONMENTAL IMPORTANCE

• Sediment in water bodies can cover the eggs of fish and other organisms, preventing them from reproducing.

• Excess sediment that is suspended in streams and rivers acts like sandpaper on fish and other organisms. Suspended sediment can also abrade the tissues of plants that live in the water.

• Sediment in water bodies can clog the gills of fish and other organisms that have gills, making breathing difficult.

• Sediment reduces light penetration, making photosynthesis more difficult for water plants.

13

• While blocking light penetration, the soil particles absorb the heat from sunlight and later release it, thereby raising the temperature of the water and driving off desirable fish populations.

Aesthetic & Recreational Reasons

• Clear water is more desirable for swimming, boating, canoeing and fishing than mud-filled water.

• Excess sediments build up in lakes and rivers. This raises the water level but reduces water depth, which decreases canoeing and fishing opportunity

Economic Reasons

• Excess sediment can increase the cost of treating drinking water and negatively affect the equipment used in the drinking water treatment process. This increases the cost of treating drinking water.

• Other pollutants such as pesticides, herbicides and oil, can become attached to eroded soils and enter water bodies along with the soil. These contaminants can making swimming unhealthy for children and adults.

PREVENTIVE MEASURE FOR REDUCING EXCESSIVE SEDIMENT LOAD IN STREAMS INCLUDE:

• Proper repair and maintenance of drainage ditches and levees;

• Minimal disturbance of the stream banks;

• Avoidance of structural disturbance of the river;

• Reduction of sediment excesses arising from construction activities;

• Application of artificial and natural means for preventing erosion; and

• Use of proper land and water management practices on the water-shed.

REMEDIAL MEASURES INCLUDE:

• Construction of detention reservoirs, sedimentation ponds, or settling basins;

• Development of side-channel flood-retention basins; and

14

• Removal of deposited sediment by dredging.

WATER SUPPLY QUALITY AND TESTING

EQUIVALENT WEIGHT

The equivalent weight (i.e. an equivalent) is the amount of substance (in grams) that supplies one gram-mole (i.e. 6.02 * 10 23) of reacting units.

The equivalent weight can be calculated as the molecular weight divided by the change in oxidation number experienced in a chemical reaction.

Equivalent Weight (EW) = MolecularWeight (MW )OxidationNumber (valency)

Question

What are the equivalent weights of the following compounds?

a) Al in the reaction Al+++ + 3e- ______Alb) H2SO4 in the reaction H2SO4 + H2O ------ 2H+ + SO4-- + H2Oc) NaOH in the reaction NaOH + H2O -------Na+ + OH- + H2O

Solution

a) The atomic weight of aluminium is approximately 27. Since the oxidation number is 3, the equivalent weight is 273 = 9

b) The molecular weight of sulphuric acid is approx. 98. Since the acid changes from a neutral molecule to ions with 2 charges each, the equivalent weight is 982 = 49

c) Sodium hydroxide has a molecular weight of approximately 40. The originally neutral molecule goes to a singly charged state. Therefore, the equivalent weight is 40÷1 = 40

Cations and Anions in Neutral Solutions

For the water to be electrically neutral, the sum of anion equivalents must equal the sum of cation equivalents.

Concentrations of dissolved compounds in water are usually expressed in mgl

15

However, anionic and cationic substances can be converted to their equivalent concentrations in milli-equivalents per litre (Meq/L) by dividing their concentrations in mg/L by their equivalent weights.

Question

A water analysis reveals the following ionic compounds in solution:

Ca++29.0mgl ; mg++, 16.4

mgl ; Na+, 23

mgl ; K+, 17.5

mgl ;

HCO3-, 171

mgl ; SO4

--, 36.0 mgl ; Cl- , 24.0

mgl .

Verify that the analysis is reasonably accurate?

Use equivalent weights provided to complete the following table.

compound Concentration (mgl )

Equivalent weight

Meq\L

CationsCa++ 29.0 20.0 1.45

Mg++ 16.4 12.2 1.34

Na+ 23.0 23.0 1.00

K+ 17.5 39.1 0.45Total 4.24

AnionsHCO3

- 171 61.0 2.81

SO4-- 36.0 48.0 0.75

Cl- 24.0 35.5 0.68

Total 4.24The sums of the cation equivalent and anion equivalent are equal. The analysis is presumed to be reasonably accurate.

16

ACIDITY

Acidity is a measure of acids in solution. Acidity in surface water is caused by the formation of carbonic acid (H2CO3) from carbon dioxide in the air

Carbonic acid is aggressive and must be neutralized to eliminate potential water pipe corrosion.

ALKALINITY

Alkalinity is a measure of the ability of a water to neutralize acids (i.e. to absorb hydrogen ions without significant pH change) The principal alkaline ions are OH-,, CO3

--, and HCO3- and rarely NO3-

The measure of alkalinity is the sum of concentrations of each of the substances measured as equivalent weight of CaCO3.

Question

Water from a city well is analysed and found to contain 20 mgl as

substance of HCO3- and 40 mgl as substance of CO3

--. What is the alkalinity of the water expressed as CaCO3?

Solution

The equivalent weight of HCO3- = 61 g. The equivalent weight of CO3

-- =30gmol , the equivalent wt of CaCO3 =50gmol .

M (mgl of CaCO3) ¿( 20mg

l)(50 gmol

)

61 gmol

) + ¿)(50g /mol30g /mol) = 83.1 mgl as CaCO3 .

HARDNESS

Hardness in natural water is caused by the presence of any polyvalent but not singly charged metallic cations. Principal cations causing hardness in water and the major anions associated with them are tabulated below

17

Cations AnionsCa++ HCO3

-

Mg++ SO4--

Sr++ Cl-Fe++ NO3

-

Mn++ SiO3--

Total hardness is defined as the sum of the concentration of the divalent cations of calcium and magnesium and is expressed in terms of milligrams per litre as CaCO3.

Carbonate hardness is caused by cations from the dissolution of calcium or magnesium carbonate and bicarbonate in the water.

Carbonate hardness is hardness that is chemically equivalent to alkalinity, where most of the alkalinity in natural water is caused by the bicarbonate and carbonate ions.

Noncarbonated hardness is caused by cations from calcium and magnesium compounds of sulphate, chloride, or silicate that are dissolved in the water.

Noncarbonated hardness is equal to the total hardness minus the carbonate hardness. Although high values of hardness do not present a health risk, they have impact on the aesthetic acceptability of water for domestic use. Hardness reacts with soap to reduce its cleansing effectiveness and to form scum on the water surface.

Water containing bicarbonate (HCO3-) can be heated to precipitate carbonate (CO3

--) as a scale.

Noncarbonated hardness, also called permanent hardness cannot be removed by heating. It can be removed by precipitation softening processes or by ion exchange processes’

QUESTION

A water sample is found to contain sodium (Na+, 15mgl ), magnesium (mg+

+, 70 mgl ) and calcium (Ca++ , 40 mgl ) . What is the hardness?

Solution

18

Sodium is singly charged, so it does not contribute to hardness.

Equivalent weights: Mg: 12.2 gmol , Ca: 20.0 g

mol , CaCO3: gmol

The equivalent hardness = (70mgl )¿¿) + (40mgl )(5020 g/mol) =386.9mgl

HARDNESS AND ALKALINITY

Hardness is caused by multi-positive ions. Alkalinity is caused by negative ions. Both positive and negative ions are present simultaneously. Therefore, alkaline water can also be hard.

If hardness and alkalinity (both as CaCO3) are the same, then there are no SO4- Cl-, or nitrate NO3

- ions present. That means, there is no non-carbonate (permanent) hardness. If hardness is greater than alkalinity, however, then non-bicarbonate hardness is present. If hardness is less than the alkalinity, then all hardness is carbonate hardness and the extra HCO3- comes from other sources such as NaHCO3).

QUESTION

A water treatment plant will treat 28 million gallons per day (average flow) of water with the following raw water characteristics:

Chlorides: 92 mgl Calcium: 94mg\l

Potassium: 31 mgl Magnesium: 28 mg\L

Sodium: 14 mgl Alkalinity: 135mg\l as CaCO3

Sulphates: 134mgl pH: 7.8

Total solids: 720 mgl Temperature: 21oC

a) Perform the ion balance analysis for the raw water (use milli-equivalents\litre)

b) Total hardness and non-carbonate hardness.

Solution

19

Ion balance is expressed as milli-equivalents/litre (m−eql )

Milli-equivalent/litre = (milligramslitre ) per equivalent weight.

CATIONS:

Na 1423 = 0.61m−eql , K 31\39 = 0.79 m-

eq\l

Mg 2812.2 = 2.29 m−eql , Ca 94\20 = 4.70

Total cations = 8.39m−eql ,

ANIONS

SO4-- 134/48 = 2.79 m−eql , Cl- 92/35.5 = 2.59

m−eql ,

As CaCO3

HCO3- + CO3-- alkalinity/m-eq. calcium carbonate =13550 = 2.70

Total anions =8.1m−eql ,

b) Total hardness and non-carbonate hardnessTotal hardness = (Ca++) + (Mg++) as CaCO3

94*50\20 + 28*50\12.2 = 350 mg\l as CaCO3

Total hardness >AlkalinityTherefore Non-carbonate hardness = Total hardness – Alkalinity 350mgl - 135mgl = 215 mgl

SAFE DRINKING WATER ACT

EPA (USA) has established standards which set limits on the amounts of various substances in drinking water. Every public water supply serving 25 or more people must ensure that its water meets these minimum standards.

20

The standard establishes various contaminant levels and its effects as tabulated below

CONTAMINANT SUGGESTED LEVELS

EFFECTS

Aluminium 0.05 to 0.2 mglDiscoloration of water

Chloride 250 mglSalty taste & pipe corrosion

Colour 15 colour units Visible tints

Copper 1.0 mglMetallic taste & staining

Corrosivity noncorrosive Taste, staining & corrosion

Fluoride 2.0 mgl Dental fluorosis

Foaming agents 0.5 mglFroth, odour, and bitter taste

Iron 0.3 mglTaste, staining and sediment

Manganese 0.05 mglTaste and staining

Odour Rotten egg musty & chemical odour

pH 6.5 to 8.5 Low pH – metallic taste , & Corrosion; High pH –Slippery feel; soda taste and deposits

Silver 0.1 mgl Discoloration of skin & greying of eyes

Sulphate 250 mglSalty taste and laxative effect

Total dissolved solids (TDS 500 mgl

Taste, corrosivity, soap interference

Zinc 5 mglMetallic taste

21

Phosphorus

Phosphorus can enter water supplies in large amounts from runoff. Excessive phosphate discharge contributes to aquatic plant (phytoplankton, algae and macrophyites) growth and subsequent eutrophication. Eutrophication is an ‘over-fertilization’ of receiving waters.

Nitrogen

Compounds containing nitrogen are not abundant in virgin surface waters. However, nitrogen can reach large concentrations in ground waters that have been contaminated with animal waste runoff or that have percolated through heavily fertilized fields.

Nitrogen can exist in various oxidation states such as nitrates (NO3--), nitrites (NO2-), ammonia (NH3) and organic nitrogen

Excessive amounts of nitrates in water can contribute to fatigue and convulsion in children, liver and colon cancer, blue baby syndrome and early pregnancy termination (miscarriages).

Nitrates also stimulate aquatic plant growth.

Un-ionized ammonia is a colourless gas at standard temperature and pressure. A pungent odour is detectable at levels above 50mgl . Ammonia is very soluble in water at low pH

Ammonia levels in zero-salinity surface water increase with increasing pH and temperature rise

TURBIDITY

Turbidity is a measure of the light transmitting properties of water, and is comprised of suspended and colloidal material.

Viruses and bacteria become attached to these particles, where they can be protected from bactericidal and viricidal effects of chlorine, ozone and other disinfecting agents.

SOLIDS

22

Solids present in a sample of water can be classified in several ways

a) Total solids (TS): Total solids are the material residue left in the vessel after the evaporation of the sample at 105 o C. Total solids include total suspended solids and total dissolved solids.

b) Total suspended solids (TSS): The material retained on a standard glass fibre filter disk is defined as the suspended solids in a sample.

c) Total dissolved solids (TDS): These solids are in solution and pass through the pores of the standard glass-fibre filter. Dissolved solids are determined by passing the sample through a filter, collecting the filtrate in a weighed drying dish and evaporating the liquid at 180o C. The gain in weight represents the dissolved solids.

d) Total volatile solids (TVS): If the total suspended solids is ignited to a constant weight in an electric furnace at 550o C, the loss in weight during the ignition process equals the total volatile solids

WATER SUPPLY TREATMENT AND DISTRIBUTION

Water Treatment Plant Location

The location chosen for a water treatment plant is influenced by many factors. The most common factors include availability of resources such as

a) Local water, b) power c) sewerage services and economic factors such as land costs, annual taxes, other considerations are environmental factors

It is imperative to locate water treatment plants above the flood plain at least 4.5 to 6 meters high. This requirement also eliminates the need to pump the water between processes. The average operational life of the equipment is 25 to 30 years when properly maintained.

PROCESS INTEGRATION

The processes and sequences used in water treatment plant depend on the characteristics of the incoming water.

Conventional water supply treatment involves the following sequences 1) Storage

2) Screening 3) rapid mixer 4) flocculator 5) settling tank

6) Filter 7) storage 8) high lift pumps to distribution

23

PRELIMINARY TREATMENT

Preliminary treatment is a general term that usually includes the following: screening, pre-sedimentation, micro straining, aeration and chlorination.

SCREENING

Screens are used to protect pumps and mixing equipment from large objects. The degree of screening required will depend on the nature of solids expected. Screens can be either manually or automatically cleaned.

MICROSTRAINING

Micro-strainers are effective at removing 50 to 95 % of the algae in incoming water. Micro-strainers are constructed from woven stainless steel fabric mounted on a hollow drum that rotates at 4 to 7 rpm.

ALGAE PRETREATMENT

Biological growth in water from impounding reservoirs, lakes, storage reservoirs, and settling basins can be prevented or eliminated with an algaecide such as copper sulphate. Such growth can produce unwanted taste and odours, clog fine-mesh filters, and contribute to the build-up of slime.

Note: copper sulphate is toxic so it should not be used without considering and monitoring the effects on aquatic life such as fish.

24

PRE-SEDIMENTATION

The purpose of pre-sedimentation is to remove easily settled sand and grit. This can be accomplished by using pure sedimentation basins, sand and grit chambers.

Trash racks may be integrated into sedimentation basins to remove leaves and other floating debris.

AERATION

Aeration is used to reduce taste- and odour –causing compounds, to reduce dissolved gases (e.g. hydrogen sulphide), to increase dissolved CO2 i.e. re-carbonation or decrease CO2, to reduce iron and manganese,

Various types of aerators are used. The best transfer efficiencies are achieved when the air-water contact areas are large, the air is changed rapidly, and the aeration period is long.

SEDIMENTATION TANKS

Sedimentation tanks are usually concrete, rectangular, or circular in plan, and are equipped with scrapers or raking arms to periodically remove accumulated sediment.

Water containing suspended sediments can be held in a plain sedimentation tank (basin) that allows the particles to settle out. Settling velocity and settling time for sediment depends on the water temperature, viscosity, particle size, and particle specific gravity

COAGULANTS

Various chemicals can be added to remove fine solids. There are two main categories of coagulating chemicals namely hydrolysing metal ions such as aluminium sulphate commonly called alum and ionic polymers.

Since the chemical work by agglomerating particles in the water to form floc, they are known as coagulants. Floc is the precipitate that forms when the coagulant allows the colloidal particles to agglomerate.

FLOCCULATION ADDITIVES

Flocculation additives improve the coagulation efficiency by changing the floc size. Additives include weighting agents (e.g. bentonite clays), adsorbents e.g. powdered activated carbon and oxidants (chlorine)

MIXERS

25

Coagulants and other water treatment chemicals are added in mixers. If the mixer adds a coagulant for the removal of colloidal sediment, it may be known as a flocculator.

If the basin volume is small, so that time for mixing is low, the tank is known as a flash mixer or rapid mixer.

Flocculation

After flash mixing, the floc is allowed to form during a 20 to 60 min. period of gentle mixing.

Flocculation is followed by sedimentation for 2 to 8 hours in a low –velocity portion of the basin. A good settling process will remove 90 % of the settle-able solids.

SLUDGE QUANTITY

Sludge is the watery waste that carries off the settled floc and water softening precipitates.

FILTRATION

Non-settling floc, algae, suspended precipitates from softening, and metallic ions (iron and manganese) are removed by filtering.

Sand filters are commonly used for this purpose. Sand filters are beds of gravel, sand, and other granulated materials.

GROUNDWATER

Groundwater is all water below the surface of the earth. It includes saturated and unsaturated zones.

Facts on Groundwater

• 75 % of all freshwater is groundwater. Groundwater is renewable, clear, bacterially pure, constant temperature and constant quality.

• Groundwater is a valuable resource as drinking water and for irrigation.

• As part of hydrologic cycle

• Geologic process

• Geotechnical problem

• Feature of the environment

26

Aquifers, Aquiclude & Water table

Aquifer is a geologic formation through which water flows easily (e.g. sand, gravel, porous sandstone and limestone.

Aquiclude or aquitard is a geologic formation through which water does not flow easily (clay, shale, massive igneous and metamorphic rocks. Typically K1/K2 >1/1000. Where K1 & K2 are the hydraulic conductivities of the aquiclude and aquifer

Water Table is the top of the saturated zone where pressure equals atmospheric. Level of water in shallow wells.

Sources of Groundwater Pollution

Sanitary landfills Hazardous waste (warfare chemicals) disposal sites Saline (salt) water intrusion Dumping raw sewage & Bacteriological contamination (cholera,

diarrhoea, yellow fever) Garbage dumps, vegetable and animal waste Pesticides, Insecticides, herbicides and fertilizers Acid mine drainage, chemical spills, lead paints Septic tanks & buried storage tanks at filling stations Industrial plant effluent (cancer causing e.g. leukaemia

STORM SEWER DESIGN

STORM RAINFALL

Storm rainfall can be classified as a large amount of precipitation falling at a particular place in a short period of time.

Storm rainfall characteristics include the duration, total volume, intensity, and areal distribution of the storm. Storms are also characterized by their recurrence intervals.

The duration of storms is measured in hours and days. The volume of rainfall is simply the total quantity of precipitation dropping on the watershed.

Precipitation data on rainfall can be collected in a number of ways, but the use of an open precipitation rain gauge is quite common. This type of gauge measures only the volume of rain collected between readings, usually 24 hr.

RAINFALL INTENSITY

27

Effective design of storm sewer depends on its geographical location and the degree of surface protection. Once the location of the feature is known, the design storm must be determined based on some probability of recurrence.

Rainfall intensity is the amount of precipitation per hour. The instantaneous intensity changes throughout the storm. However, it may be averaged over short time intervals or over the entire storm duration. Average intensity will be low for most storms, but it can be high for some. These high intensity storms can be expected infrequently, say every 20, 50, or 100 years. The average number of years between storms of a given intensity is known as the frequency of occurrence or recurrence interval.

In general, the design storm may be specified by its recurrence interval. For example, a 100 –year storm, its annual probability of occurrence is 1 % storm. A 1% storm is a storm that would be exceeded in severity only once every hundred years on the average.

The average intensity (I) of a storm over a time period t can be calculated using the STEEL FORMULA as follows

I =K\ (tc + b); K and b are constants.

Establish the intensity-duration-frequency curve.

Take the reciprocal of the Steel equation and convert the equation to a straight line.

1\I = (tc + b)\K = tc\K + b\K = C1tc + C2

Once C1 and C2 have been found, K and b can be calculated.

K = 1\C1; and b = C2\C1

Note: K and b are derived from rainfall data for the area at some frequency of storm. i.e. western region (Tarkwa); 25 year storm

I = 360(t+26) t = time of duration (concentration) of the storm in minutes

RUNOFF

Runoff refers to the water that runs off the land as a result of rainfall. Estimating runoff volumes and rates is necessary for proper design of many erosion, sedimentation and storm water control structures such as culverts, diversions, storm water ponds and sediment basins. Runoff is primarily influenced by soil texture, surface characteristic, the intensity and duration

28

of the rain event, the slope and flow length of the drainage area, and the size of the drainage area.

The surface characteristics of a site greatly influence the volume and rate of water running off the land. For example, runoff will range from less than five or ten per cent of the total rainfall on heavily vegetated areas like forests, to nearly 100 per cent of the rainfall for impervious surfaces like pavement.

FLOODS

A flood occurs when more water arrives than can be a carried away. When a watercourse i.e. a river or a creek is too small to contain the flow, the water overflows the banks.

The flooding may be categorized as nuisance, damaging or devastating.

Nuisance floods result in inconveniences such as wet feet, tyre spray and soggy lawns. Damaging floods soak basements and ground floor furniture while Devastating floods wash buildings, vehicles and livestock downstream.

Although rain causes flooding, large storms do not always cause floods. The size of a flood depends not only on the amount of rainfall, but also on the conditions within the watershed before and during the rain. Controlling the discharge from communities just developed prevents downstream flooding brought on by urbanization of the watershed or wetlands and makes diversion dykes and storage of storm water runoff imperative.

PEAK RUNOFF FROM THE RATIONAL METHOD

Although total runoff volume is required for reservoir and dam design, the instantaneous peak runoff is needed to size culverts and storm drains.

The rational formula for peak discharge is given by

QP =CIAd where Qp = peak discharge; I = rainfall intensity;

Ad = drainage area; and C= constant

Values of “C”

Asphaltic pavements 0.85 --- 0.90

Parks and grass fields 0.10 ---0.25

29

Accra Central 0.70----0.95

Neighbourhood area 0.50 ----0.75

Problem

Calculate the peak discharge at a Tarkwa neighbourhood if the development area is 2.5 acres, Inlet concentration time = 10 minutes, C=75%. Use 25 year storm.

Solution:

I25 = 360(10+26) = 10.0

1 acre = 43560 sf/ac

Qp = 0.75 x 10 x 2.5 acres = 18.75 cfs

Problem

Two adjacent fields, as shown, contribute runoff to a collector whose capacity is to be determined. The storm intensity after 25 is 3.9 in\hr. Use the rational method to calculate the peak flow.

Ad = 2 ac C1 =0.35 t1 = 15 min

A2 =4 acC2 = 0.65 t2 =10 min

( )

Solution

The overland flow time is given for both areas. The time for water from the farthest corner to reach the collector is

tc = 15 min + 10 min = 25 min.

30

The runoff coefficients are given for each area. Since we want to size the pipe carrying the total runoff, the coefficients are weighted by their respective contributing areas.

C =¿¿ = 0.55

The intensity after 25 minutes was given as 3.9 in/hr.

The total area is (4+2) acres.

The peak flow (Qp) = CIA = 0.55* 3.9 in\hrx6 ac. =12.9 ac. In/hr. (ft3/s)

HYRAULIC RADIUS

The hydraulic radius is defined as the area in flow divided by the ‘wetted perimeter’. The hydraulic radius is not the same as the radius of a pipe. The area in flow is the cross sectional area of the fluid flowing. The wetted perimeter is the length of the line representing the interface between the fluid and the pipe or channel. It does not include the ‘free surface’ length (i.e., the interface between fluid and atmosphere.

Rh = Area of flowWetted perimeter = AP

Consider a circular pipe flowing completely full. The area in flow is πr2. The wetted perimeter is the entre circumference 2πr =2 x 227 x r. The hydraulic

radius of the pipe =πr 22πr=22/7 r22x 22/7 xr = r2 = D4

SIZING TRAPEZOIDAL AND RECTANGULAR CHANNELS

Trapezoidal and rectangular cross sections are commonly used for artificial surface channels. The flow through a trapezoidal channel is easily determined from the Manning equation when the cross-section is known. However, when the cross-section or uniform depth is unknown, a trial-and-error solution is required.

MOST EFFICIENT CROSS SECTION

The most efficient open channel cross-section will maximize the flow for a given Manning coefficient, slope, and flow area. Accordingly, the Manning

31

equation requires that the hydraulic radius be maximum. For a given flow area, the wetted perimeter will be minimum.

Semi-circular cross sections have the smallest wetted perimeter; therefore, the cross section with the highest efficiency is the semicircle. Although such a shape can be constructed with concrete, it cannot be used with earth channels

The most efficient cross section is also generally assumed to minimize construction cost. Rectangular and trapezoidal channels are much easier to form than semi-circular channels.

The most efficient rectangle is one having depth equal to one-half of the width.

w/2

w

most efficient rectangle

d

d = w2 (most efficient rectangle)

Area = dw = w x w2 = w2/2

Perimeter = d + w + d = w2+w +w2=¿2w =4d

Wetted perimeter (Rh) = d+ w + d = w2 +w+ w2

=¿2w

The most efficient trapezoidal channel is always one in which the flow depth is twice the hydraulic radius. If the sides slope is adjustable, the sides of the most trapezoid should be inclined at 600 from the horizontal. Since the surface width will be equal to twice the sloping side length, the most efficient trapezoidal channel will be half of a regular hexagon (i.e. three adjacent equilateral triangles of side length 2d\3.5). If the side slope is any other angle, only the d=2R is applicable.

32

yy

60° 32

1 1

2

60°

x

3d

3d

32d

32d

d

60o

by pythagoras

dx = tan 60⁰

X= d

tan 60

X= d√3

Sin 60⁰ =dy

Y=d

sin 60

Y= 2d√3

Top width = d√3 +

2d√3 +

d√3

=4 d√3

Perimeter=2d√3 +2d√3 +

2d√3

=6d√3

Area of half the hexagon = Area of a trapezium

=12 (a+b )h , where h= d, a = 2d√3 and b= top width

Thus, area = =12 ( 2d√ 3+ 4 d√ 3 )d

33

= 12 ( 6 d√ 3 )d =3d2/√3

Wetted perimeter Rh= 3d2/√3 divided by 6d√3

=3d2/√3 x √36d = 3d2/6d =d2

d = 2R (most efficient trapezoid)

b = 2d\3-5

A = 3.5d2

P = 3b = 2*3.5d (most efficient)

R = d\2

Question

A masonry open channel is being designed to carry 14 m3\s (500 ft3\sec) of water on a 0.0001 slope. Using n= 0.017, find the most efficient dimensions for a rectangular channel.

Solution

Let the depth and width be d and w respectively.

For an efficient rectangle d =w/2

A = dw = w* w/2 = w2/2

P = d +w + d = w/2 +w + w/2 =2w

Rh = A/P = (w2/2)/2w = w/4

Using Manning’s Equation

Q = (1.00/n)AR2/3S.5

14 m3/s = (1.00/0.017)(w2/2)(w/4)2/3(0.0001).5

14 m3/s = 0.1167w8\3

w = 6.02 m

d = w/2 =6.02/2 ==3.01 m

34

MANAGEMENT OF MUNICIPAL SOLID WASTE (MSW)

Source reduction, Recycling, Incineration and Landfill

Sources and Types of solid waste

Municipal solid waste affects our quality of life regardless of where we live, work or play because the disposal of municipal waste has been a problem since the dawn of civilization. The recent population explosion has also led to tremendous generation of solid waste. For example, Ghana Environmental Protection Agency, reported that the cities of Accra and Kumasi generates about 44800 metric tons of muncipal solid waste per month.

• Residential : food wastes, yard wastes, plastics, textiles, paper, glass, electronics etc

• Industrial & commercial: housekeeping waste, metal pieces, glass, paper, cardboard, plastics.

• Construction and demolition: wood, steel, concrete, dirt

• Municipal services: street sweepings, landscape and tree trimmings, wastes from parks, beaches and sludge.

Source Reduction, Recycling, Incineration & Landfilling

• Source reduction:: Keeping the amount of waste generated to a minimum. Reduction is accomplished through process modifications, raw material quantity reduction, substitution of materials, improvements in material quality, and increased efficiencies. Avoid disposable items such as plastic bottles paper cups and plates.

• Recycling: Recycling reduce municipal solid waste, it saves kilowatts of electricity(energy). It saves natural resources such as trees and mineral deposits. It reduces global warming.

• Incineration: Burning waste to ashes and sometime generate energy. Disadvantages: Methane & carbon dioxide responsible for the greenhouse effect or global warming .

• Landfilling: common method of dealing with municipal solid.

35

RECYCLING OF SOLID WASTE

• Recycling is processing used materials (waste) into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution (from incineration) and water pollution (from landfills)

• Recyclable materials are many and varied. They include varieties of glass, paper, metal, plastics, textiles, and electronics components and recycled asphalt pavements (rap).

RECYCLING PROCESS

• Collection: ‘Drop-off’ and ‘Buy Back’ centers

• ‘Drop-off’ centers require the waste producer to carry the solid waste to a central location, which can be either a mobile or installed center or reprocessing plant itself.

• ‘Buy-back’ centers as the name implies rewards people for returning specified materials items for cash. It ensures a stable supply of that material.

• SORTING: Early sorting of recyclable materials are important step in recycling and this involves a series of manual or automated processes.

• RECYCLING PLANT: Different Recycling plants are set up for different materials such as papers, glass and metals.

BENEFITS OF RECYCLING

• Energy: Recycling saves a lot of energy; however the amount of saved energy depends on the recyclable material. For example, recycling aluminum cans, save 95 percent of the energy required to make the same amount of aluminum from its virgin source, bauxite. Also, a paper mill uses 40 percent less energy to make paper from recycled paper than it does to make paper from fresh lumber.

• Conservation of Natural Resources: Recycling of solid waste materials into new products helps to conserve many natural resources. Metals such as steel and aluminum are very costly to manufacture, so they are the world’s most recycled materials. About 67 percent of the steel is recycled. Steel cans and scraps are melted and annealed at recycling plants to make the steel new again. The conserved bauxite and iron ores also saves the environmental terrain from surface mining and mine wastes tailings.

36

• Recycling reduces amount of garbage going to the landfill thereby saving landfill space for other developmental projects.

• Deforestation is reduced since fewer trees are felled down to make newspapers. More trees in the forest reduces global warming, prevents erosion and runoff.

• Employment : Recycling creates employment opportunities

• Education: people should be educated about the importance of recycling to the environment and economy.

INCINERATION

• Definition: Incinerate is to burn completely or to reduce to ashes.

• An incinerator is a unit or facility used to burn all kinds of waste materials such as gas, liquid, solid, sludge until it is converted to ash, flue gas and heat.

• Types of incinerators: Rotary kiln, fluidized bed, catalytic bed, liquid injection, waste gas flare and direct flame.

• Incineration is a high-efficiency process. When incinerators are properly designed, destruction efficiency can be as high as 99.9 %. Critical design variables include combustion–chamber temperature, turbulence (degree of mixing), residence time, concentration and type of contaminants

• How does it work?: Waste is fed in. The furnace is ignited and the temperature is raised to suite the waste material to be burned. Waste materials are allowed to combust with the aid of air (oxygen). After the process is complete, ash and flue gas generated are disposed of appropriately.

ADVANTAGES & DISADVANTAGES OF INCINERATORS

• Advantages: When designed and operated properly, removal of combustible pollutants such as toxins and pathogenically contaminated material is essentially complete; emission is quite clean and safe. Reduction of waste volume is 90 %. And mass reduction of75%.

• Performance is constant and predictable.

• Production of thermal energy.

37

• Disadvantages: High operating and capital costs.

• Formation of secondary products during incineration of compounds containing elements other than carbon, hydrogen, and oxygen (such as chlorine and sulfur) causing production of acidic gases that result in corrosion problems. Potential emissions include CO, Nox, Sox, HCl, heavy metals, and aldehydes.

• Public opposition due to concern about emissions.

Hazardous Waste Management

1. Nuclear & chemical Waste2. Insitu Vitrification3. Deep well injection of liquid waste

Hazardous waste (soilids, liquids & gas)

• Definition: Hazardous waste is defined as solid or liquid or gas which is in large quantity, or concentration, or has physical, chemical, or infectious characteristics which may either a) cause an increase in mortality or serious illness or b) pose a present or future hazard to health or the environment when improperly treated, stored, transported, disposed of, or managed.

• Two notable ‘rules’ pertain to hazardous wastes. “The mixture rule” states that any solid waste mixed with hazardous waste becomes hazardous. “The derived from rule” states that any waste derived from the treatment of a hazardous waste (e.g. ash from the incineration of hazardous waste) remains a hazardous waste.

Characteristics of hazardous waste

• A waste is considered hazardous if it exhibits one or more of the following characteristics: ignitability, corrosivity, reactivity, and toxicity.

• Ignitable: wastes whose flash point is less than 60 degrees Celsius. Eg. Flammable liquids such as solvents, waste oils, brake fluids.

38

• Corrosive: if the pH is less than 2 or greater than 12.5. eg. Wastes from acids and alkaline liquids.

• Reactive: a substance which reacts violently with water to create explosions, toxic fumes or gases. Eg, lithium-sulfur batteries and explosives

• Toxic: Wastes which are harmful or fatal when ingested or absorbed. Eg. Lead, mercury, arsenic, chromium, benzene, and chlorinated hydrocarbons, herbicides and pesticides.

NUCLEAR WASTE

• Nuclear waste is the radioactive waste left over from nuclear reactors, nuclear research projects, and nuclear bomb production. Nuclear waste is classified as low, medium, and high-level waste depending on the amount of radioactivity the waste produces.

• All substances are slightly radioactive from the decay of naturally occuring isotopes such as carbon-14, uranium-238 and thorium-232.

• SOURCES OF NUCLEAR WASTE:

• A) The largest source of nuclear waste is naturally occurring radioactive material (NORM) eg radon gas

• B) The other primary source of nuclear waste is human-built nuclear reactors and leftover depleted uranium from the enrichment process.

• Harmful effects of nuclear wastes: nuclear wastes emit harmful radiations which damage our tissues, cells and red blood corpuscles and may cause cancer and leukemia.

• Disposal of Nuclear waste: while nuclear materials represent some of the highest levels of technological development, they also present huge hurdles in terms of their safe processing, use, maintenance, and disposal.

• When in a molten state, glasses tend to be highly corrosive and dissolve other oxides readily.

Disposal of nuclear waste

• Glasses are nonselective in this dissolution because their non-crystalline nature permits them to incorporate other atoms without much regard for size, valence or crystal form. One way to take

39

advantage of this characteristic is to use particularly durable glasses as a matrix material for disposal of high-level nuclear waste.

• Nuclear waste is combined with glassmaking ingredients and fed to the top of as aqueous slurry. The water evaporates and the ingredients combine to form a homogeneous black glass, in which the radioactive elements (waste) are dissolved at the molecular level.

• All nuclear wastes must be identified before disposal.

• The nuclear waste must be sealed and packaged appropriately for storage and disposal.

Harmful effect of Chemical waste

• Chemical waste includes solvents, acids, alkalis, toxic materials, photographic chemicals, and paints, laboratory chemicals whose shelf life has expired and has deteriorated with age.

• Hazardous chemical waste pollutes rivers, lakes, ground waters and destroys aquatic life and terrestrial animals.

• Compounds such as dichlorodiphenyltrichloroethane (DDT) and dioxins, PCB are more soluble in fats than in water and therefore tend to build up in the fats within plants and animals.

Disposal of Hazardous Liquid waste in Deep wells.

• Hazardous liquid waste are toxic, corrosive, reactive and ignitable

• Injection of liquid wastes, mainly of industrial origin, into a deep underground formation, (injection zones) is to isolate hazardous substance from the biosphere.

• Injection zones used for chemical waste disposal characteristically are permeable saline-bearing sandstone and carbonate rocks. These injection zones are at a depth of 400 to 1500 meters below the surfaces. The pumping liquid should be compatible with the subsurface rocks and fluids. Also the pressure must be sufficient to displace the native fluids, but not so great to cause fracturing of the strata or excessive migration of the waste.

Geological considerations

• A suitable formation should meet the following criteria:

40

• It should have no value as a resource- for example, as a source of drinking water, hydrocarbons, or geothermal energy.

• It must have sufficient porosity and volume to accept the anticipated volume of liquids.

• It should be located in an area with little seismic activity, to minimize both the risk of the earthquake to the well and the triggering of seismic events.

• It must be sealed above and below by formations with sufficient strength, thickness and low permeability to prevent migration of the waste from the disposal zone.

Advantages & Disadvantages

• Advantages: Deep well injections are presently the cheapest method of waste disposal.

• Negligible waste treatment occurs to injection

• There are virtually no restrictions on the type of wastes that may be injected.

• Disadvantages : there is the tendency of the wastes to contaminate underground source of drinkable water

Engineered Remediation Processes

• In situ remediation schemes are introduced for the treatment of both groundwater and the vadose zone. The vadose zone is the unsaturated zone between the land surface and the water table,

• Air-sparging and pump-and—treat technologies are used to remediate groundwater.

• Soil vapour extraction and bioventing are popular treatment schemes used for vadose zone. Another process is In situ vitrification

Remediation process

• Containment::

• PHYSICAL: Groundwater contamination can be contained physically by using an underground barrier of clay, cement or steel.

• HYDRAULICS: Extraction wells are installed to keep contaminants from moving past the wells.

41

• CHEMISTRY: known reactive chemicals are used to either immobilize or detoxify the contaminant.

• REMOVAL: (PUMP & TREAT TECHNOLOGY) The most common way of removing a full range of contaminants ( including metals, volatile organic compounds (VOC), herbicides and pesticides from an aquifer is by capturing the pollution with extraction wells and then treating the contaminant water above ground and the resulting clean water is discharged back into the aquifer or a river.

• Air sparging: Small diameter wells are used to pump air into the aquifer. As the air moves through the aquifer, it evaporates the volatile chemicals. The contaminant air that rises to the top of the aquifer is then collected using vapor extraction wells.

ACID MINE DRAINAGE

DEFINITION

ACID Mine Drainage refers to acidic water that drains from coal or metal mines.

• Causes Acid mine drainage is a pollution problem resulting from the oxidation of pyrite (FeS2) present in mine wastes.

• Specifically, acid mine drainage is water with a high concentration of sulphuric acid which can create extremely low pH conditions.

• The acid is produced by a simple weathering reaction when sulfide minerals associated with coal or a metal such as zinc, gold, lead or copper come into contact with oxygen-rich water near the surface, the sulfide minerals oxidize.

Sources of water

• Surface water that infiltrates into mines

• Shallow groundwater that moves through mines

• Surface and shallow groundwater that come into contact with mining waste, called tailings.

Damaging effects of AMD

• The leachate (acid discharge) kills vegetation and fish.

• Contaminates ground water

42

• Negatively affects the environment for many years following cessation of mining operations.

Acid mine drainage abatement

• Lime treatment

• Lime treatment of process water is a common method of treatment in anthracite coal washing plants.

• Treatment neutralizes the acidity and removes heavy metals, especially iron.

• High purity limestone or a combination of lime and pulverized limestone (a split limestone-lime treatment) are used.

Two step treatment process

• Step one: treat acid mine drainage waters with finely ground limestone to raise the pH to between 5 and 6.

• Ferric iron precipitates out.

• Step two: add lime to complete neutralization process by raising the pH to about 9.

• Ferrous iron precipitates out.

Hazards of lime treatment

• Lime is a high cost material

• Produces large volume of fine sludge

• Streams and aquatic life may be adversely affected by accidental over treatment

Advantages of limestone

• Limestone is less caustic so it poses fewer hazards for operating personnel to handle the material.

• Most effective as an acid neutralizing agent in a pH range of up to 6.0

• Produces lower volumes of fine sludge.

Bio-reclamation

43

• Bio-reclamation can be used to abate acid mine drainage environmental hazards.

• Desulfovibrio desulfurican bacteria are capable of raising the pH of natural acidic wetland soil from 4.4 to 7.4. The bacteria reduce Sulphates concentration under anaerobic conditions and produces hydro-oxides.

• These microbial activities can be enhanced by constructing anaerobic wetland to accelerate the biochemical reactions.

• This biochemical reactions are known to abate the acid mine drainage problem.

BIORECLAMATION

Bio-reclamation or the treatment of contaminated soil and water by

biological means. Biodegradable materials

• These materials are able to be broken down into harmless substances by microorganisms such as aerobic and anaerobic bacteria, fungi, and algae. Sun, water, heat are essential factors.

• Environmental factors affecting microbial metabolism

• Important variables that affect microbial activity include the system temperature and pH, soil moisture content, availability of a suitable electron acceptor and required nutrients, and an appropriate and adequate bacteria population. The site must also exhibit monotonic conditions for the organisms, and there should be an absence of competitive organisms.

• Aerobic bacteria require oxygen for respiration.

• Anaerobic bacteria’s respiration does not require oxygen.

Bio-reclamation technology: Enhancing the natural biodegradation processes

• Three main approaches:

44

• A). Enhancing oxygen delivery to the microorganisms

• B). Enhancing the amount or kinds of nutrients available to the microorganisms

• C). Enhancing the amount, kind or characteristics of the microorganisms themselves

Enhanced oxygen delivery Bioventing

• Bioventing is in-situ treatment

• Advantages of bioventing

• Bioventing is pumping air into contaminated soil to physically remove volatile hydrocarbons in unsaturated soils.

• Bioventing also enhances biodegradation by providing oxygen source to the microorganisms to accelerate biological degradation processes.

• Disadvantages of bioventing

• The off-gas resulting from the bioventing process itself must be treated and is half the cost of associated with bioventing processes in field applications.

Enhancing nutrients availability

• Enhancing moisture to the contaminated soil accelerates the rate of biodegradation

• The nutrient enhancement accelerates the growth and activity of the microorganism by supplying them with nutrients such as nitrogen and phosphorus.

• This nutrient enhancement approach to biodegradation is helping bio-reclamation research and practice.

• A classic case is 11 million gallons of crude oil spill in Alaska by Exxon Valdea Company in 1988.

• Three types of nutrients were selected to enhance biodegradation on contaminated beaches. These were: solid, slow-release fertilizer, oleophilic fertilizer, and water based nutrient solutions.

• biodegradation was occurring through direct decomposition and the production of biochemical products (bio-emulsifiers)

45

Anaerobic biodegradation

• The depletion of available oxygen by natural biological processes can lead to anaerobic conditions.

• Polychlorinated biphenyls (PCB) have dielectric and flame resistance properties, chemical and thermal stability and its usage include hydraulic fluids, solvent extenders, organic diluents and plasticizers. PCB undergoes biological magnification, a process by which toxic substances accumulate in increasing high concentrations in progressively higher trophic levels. PCB is fat soluble but not water soluble.

• Anaerobic reductive process is a biological process capable of transforming a highly chlorinated polychlorinated biphenyls (PCB) to lightly chlorinated ortho-enriched congeners. This reduces the potential risk of PCB’s exposure and reduced dioxin like toxicity and carcinogenicity. There is also reduction in Bioaccumulation in the food chain.

• Anaerobic bacteria are able to breakdown chlorinated aliphatic compounds. Chlorinated aliphatic compounds are widely used as solvents and degreasing agents and they are irresponsibly disposed.

Microbial strain development

• Biotechnology is industrial or commercial use or alteration of organisms, cell DNA, or biological molecules to achieve specific practical goals

• Biotechnology can be used to isolate, select, or genetically engineer new microorganism’s strains for different situations.

• Desulfovibrio desulfurican bacteria are capable of raising the pH of natural acidic wetland soil from 4.4 to 7.4. The bacteria reduce Sulphates concentration under anaerobic conditions and produces hydro-oxides. These microbial activities can be enhanced by constructing anaerobic wetland to accelerate the biochemical reactions. These reactions are known to abate acid mine drainage problems.

• Thiobocillus ferro-oxidans aerobic bacteria are responsible for the oxidation of ferrous ions to ferric ions.

Myths about Biodegradation

46

• If some biodegradable materials such as newspaper, packaging boxes, clothing biodegrades, they release ink, dye and paint that can pollute the groundwater resource.

• Some biodegradable plastics (hydrocarbon plastics) contain many elements and additives such as chlorine, formaldehyde, dyes and metals.

• If ideal conditions do not exist, for example adequate moisture and oxygen, biodegradation proceeds at a snail’s pace. For example, old newspapers which were buried in a landfill for over twelve years were still readable.

IN SITU VITRIFICATION

• What is In Situ Vitrification ?• The process of In Situ Vitrification .• The Advantages of In Situ Vitrification . • Value of In Situ Vitrification to Soil & Groundwater

Remediation.

What is In Situ Vitrification? 

• In Situ Vitrification is a new technology developed for a new nastier breed of contaminants and pollutants.  "In Situ" means to work in place.  "Vitrification" is the process to make glass out of something.  The relevant meaning of "In Situ Vitrification" in respect to soil and groundwater pollution is to turn the soil containing the pollutant into a large block of glass.  The pollutant can then be left in place forever encased inside of the glass.  A normal site undergoing in Situ Vitrification looks like the following.

47

THE PROCESS OF IN SITU VITRIFICATION.

• The first part of the procedure for using In Situ Vitrification is determining the type of pollutants in the ground.  After the determination of what type of pollutant is involved the decision to use in situ vitrification can be made.  In Situ Vitrification utilizes 4 large graphite electrodes that are inserted into the ground in a square pattern.  The Vitrification depth is limited by the length of the graphite electrodes and the availability of power.  As the electrodes are driven into the ground, powerful generators or a direct line to a city power grid are activated.  The electricity arcs from one electrode to another.  As the electricity passes through the soil great heat is produced.  This heat reduces the soil into a molten form.  As the ground liquefies the electrodes move deeper, increasing the amount of molten soil.  When the graphite electrodes have reached the maximum possible depth the electricity is shut off and the electrodes are disconnected from the system.  As the molten soil solidifies into glass the graphite electrodes become entombed. The temperatures achieved by In Situ Vitrification

48

have reached temperatures ranging from 1,600 to 1,800 degrees Celsius. Individual blocks of glass have been formed as large as 1,400 tons and depths exceeding 20-ft have been achieved. Adjacent processes can fuse the vitrified blocks together to form a single contiguous monolith.

• The pollutants react in various ways to this remediation technique.  Organic pollutants are paralyzed and are generally reduced into gasses. 

• The gasses rise to the surface where they are collected by a gas hood over the affected site.  The gases are then transported to an off-gas treatment center.  This is a treatment system for the rendering volatile or dangerous gasses from the vitrification process inert.  The inorganic pollutants or heavy metals are encased in the glass formed by the vitrification process.  Radioactive materials are also encased in the glass and the glass formed by the soil also helps to limit the radiation leakage.   During the molten phase of the process almost all of the void spaces in the soil are removed and therefore there is a volume reduction of 20-50%.  This results in a very dense block of glass.

THE ADVANTAGES OF IN SITU VITRIFICATION (1)  

49

• There are many advantages to In Situ Vitrification over other conventional remediation techniques.

• Vitrification can deal with multiple types of contamination at once is the largest advantage of this remediation technique.  The process of vitrification does not care if the contaminants are organic, inorganic, or radioactive materials.

• Vitrification deals with the site on location not requiring expensive waste removal processes that spread out the contamination zone.  After the vitrification process is completed, the fused glass block can even be left in place.  This gives the owner of the project a large saftey benefit as there is less risk of exposure in the cleanup.  The blocks can weigh as much as 1,400 tons and are not subject to breakdown or other decomposition from the environment.

• In a comparison of In Situ Vitrification and other remediation methods, in situ vitrification is a more comprehensive remediation technique.  The remeditation is extremely effective, destroying or immobilizing almost all of the contaminants.  A side effect of this is the formation of the fused soil block.  The block represents a compaction of the soil from 20-50% of the original soil volume.  In the case of the contamination

VALUE OF IN SITU VITRIFICATION TO SOIL AND GROUNDWATER REMEDIATION.  

The Insitu vtrification process can have several advantages over other remediation processes or the removing of the pollutant in question.  Below is a list of these advantages:

Single step Process

Quicker -> This process takes only about 24 to 36 hours as opposed to weeks or possibly years. Permanent containment

50

Requires no cleaning of soils An on-site problem solver Fixes problem with no transport You get a proper disposal of pollutant Waste is contained Allows biodegradation of waste depending on half-life Protects soil from possible leaching or leaking of waste

THE ADVANTAGES OF IN SITU VITRIFICATION (2)  

1. Must be removed after treatment, the reduced volume of the block and it solid nature make the transportation easier.

2. The cost of In Situ Vitrification depends on the availability of the electricity for the melting process.  Where the price of electricity is around $.07KW, the price of In Situ Vitrification ranges from $250/ton - $750/ton.  Some information that affects this is the depth of the contamination,  for deeper projects the price is generally lower.  Soil conditions can also affect the price of the process.

VALUE OF IN SITU VITRIFICATION TO SOIL AND GROUNDWATER REMEDIATION.  

• The Insitu vtrification process can have several advantages over other remediation processes or the removing of the pollutant in question.  Below is a list of these advantages:

Single step Process

Quicker -> This process takes only about 24 to 36 hours as opposed to weeks or possibly years.

Permanent containment

Requires no cleaning of soils

An on-site problem solver Fixes problem with no transport

51

You get a proper disposal of pollutant Waste is contained

Allows biodegradation of waste depending on half-life

Protects soil from possible leaching or leaking of waste

References

• Hanson, James.  "Geosafe In Situ Vitrification Site Demonstration"  Geosafe Corporation, 31 Mar 95. http://128.6.70.23/html_docs/rrd/hansen.html

• Tixier, John.  "In Situ Vitrification"  Pacific Northwest Corporation,  13 Apr 96.  http://www.em.doe.gov/rainland/land49.html

• Nemeth, John. "Environmental Applications Research and Future Plans in Plasma Arc Technology at the Georgia Institute of Technology" Georgia Tech Research Corporation, 26 Sep 96. http://eoeml-www.gtri.gatech.edu/lab/nemeth_paper.html

• Richardson, Terry. "In Situ Vitrification Treats Organics and Inorganics" Risk Reduction Engineering Laboratory of the U.S. Environmental Protection Agency, November 1995.  http://clu-in.com/ttvitrif.htm

ANALYSIS AND DESIGN OF LANDFILLS

Introduction

A sanitary landfill is an engineered facility that requires detailed planning, specification, design, construction and efficient operation.

Landfill Facility phases

• Siting

• Design

• Construction

• Operation

• Closure

• Post-closure care

SELECTING THE “IDEAL” LANDFILL SITE

52

• Deep soil with low hydraulic conductivity. Soils with a clay-rich matrix would minimize the risk of leachate into the groundwater in the event of liner failure.

• Abundant workable soils to cover daily or at least twice a week of deposited garbage.

• Adequate deposits of final cover of low permeability soils to act as a ‘cap’ for the landfill to minimize the infiltration of rainfall at the site

• Deep occurrence of ground water table. At least there should be minimum vertical separation of 3 meters between the landfill liner and the seasonally high water table.

TECHNICAL AND NON-TECHNICAL CRITERIA

• Proximity to populated areas and transportation routes

• Potential impacts on ecologically sensitive areas such as lakes, rivers, streams, parks, wetlands and lagoons

• Wind direction and speed , including ordor, dust , and erosion considerations

• Dry climate and low infiltration rates

• Social and political concerns

• Proximity to airport FAA, USA restricts new landfill development near airports b’cos of the potential hazards that birds cause to aircraft.

• ‘Not My Backyard but in someone’s else town’

DESIGN GOALS

• Protection of groundwater quality by minimizing discharge\leakage of leachates from landfill.

• Protection of air quality and conservation of energy by installing a landfill gas recovery system

• Minimizing impact on adjacent wetlands by controlling and diverting or impounding surface runoff

• minimizing transport time for site users

• provision for miximum use of land upon site completion

CONSTRUCTION OF AN ENGINEERED LANDFILL53

• The selected landfill site is excavated into a trapezoidal shape and divided into cells. The excavated area is lined with compacted clayey soil.

• On top of the clay is a liner called geo-textile membrane (a non-biodegradable plastic) which prevents the leachate (leaked waste water from the solid waste) from seeping into the ground to contaminate the ground water.

• Installed perforated pipes on top of the geo-membrane help drain away the leachate from the geo textile membrane surface. Vertical pipes are also installed to collect built up gases.

• Underground monitoring wells are installed around the landfill to ensure that the liner and leachate collection system are operating properly.

• Bulldozers are used to spread the wastes at the landfill site and then compacted using steel wheeled rollers (compactors) to reduce the volume of wastes..

• After the compaction, laterite is used to spread over the compacted wastes to control odors and vectors. This process continues until the targeted height of a cell is reached.

• A low permeability cap is installed to prevent water infiltrating into the closed land fill.

VECTORS, LANDFILL GAS & LEACHATE

• VECTORS : In landfill parlance, a vector is an insect or rodent,or other animals of public health significance capable of causing human discomfort or injury, or capable of harboring or transmitting the causative agent of human disease. Vectors include flies, mice, mosquitoes, cockroaches and vultures.

• LANDFILL CAS: Once covered, the organic material within a landfill cell decomposes. Aerobic conditions prevail for approximately the first month. Gaseous products of the initial aerobic decomposition include carbon dioxide and water. After the first month or so, the decomposing waste will have exhausted the oxygen from the cell. Digestion continues anaerobic producing a low-heating value landfill gas consisting of approximately 50 % methane, 49 % carbon dioxide, and other trace amounts carbon monoxide, nitrogen and hydrogen sulfide. Decomposition occurs at temperatures of 40 to 60 degrees. These

54

gases are collected and destroyed or a gas collection system collects these gases to generate electricity to supply energy to local communities. This helps avoid any explosion under the wastes.

• LEACHATE: Leachate are liquid wastes containing dissolved and finely suspended solid matter and microbial waste produced in landfills. Leachate becomes more concentrated as the landfill ages. Leachate forms from liquids brought into the landfill, water runoff, and precipitation. Leachates contaminate the surrounding soils and groundwater.

BASAL STABILITY ANALYSIS OF LANDFILL EXCAVATIONS

• The basal stability analysis is to ensure the stability against heave of the bottom of an excavation destined for a landfill. It consists of comparing the ‘weight of a column of soil’ between bottom of excavation and a confined aquifer to the hydrostatic pressure or head in confined aquifer. A factor of safety is then used.

• An exploratory drill hole in saturated stiff clay. It was observed that the sand layer underlying the clay was under artesian pressure. Water in the drill hole rose to a height of 10 meters. If an open excavation is to be made in the clay, how deep can the excavation proceed before the bottom heaves? Use a factor of safety of 1.2. unit weight of clay is 18.48.0 kN\m

• Solution: 18.48*t = 9.81*10; t =5.3 m* 1.2 =6.36 m

55