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Summary

Lecture 1: Air & Noise PollutionAir Pollution Presence in atmosphere of one / more pollutants in quantities that can injure human, plants, animals or interfere with the enjoyment of life / conduct of business Point & Area Sources of Pollution Common gaseous pollutants Sulfur Oxides &...

Description

Lecture 1: Air & Noise Pollution Air Pollution -

Presence in atmosphere of one / more pollutants in quantities that can injure human, plants, animals or interfere with the enjoyment of life / conduct of business

Point & Area Sources of Pollution

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Common gaseous pollutants - Sulfur Oxides & Hydrogen Sulfide - Nitrogen Oxide - Carbon Monoxide - Carbon Dioxide - Volatile Organic Compounds - Ozone - Chlorofluorocarbons Common particulate air pollutants - Dusts - Fumes - Smoke / soot - Mist / fog - Smog

Primary & Secondary Air Pollutants -

Primary → pollutants that exist in same form as source emissions - E.g. CO, SO 2 & total suspended particulates Secondary → pollutants formed in atmosphere as a result of reactions - E.g Acidic mists, photochemical oxidants

Health Effects -

Particulates → obscure vision, cause grime on belongings, aggravate acute / chronic lung illness Carbon Monoxide → binds with haemoglobin and reduce oxygen carrying capacity of the bloody → impairs central nervous system / brain function Sulfur Dioxide → constricts the bronchi, aggravates other health conditions, suppresses immune system & increases bronchitis Nitrogen Dioxide → pulmonary irritant; causes asthmatics and pulmonary edema; longterm exposure causes necrosis, interferes with alveolar function Lead → toxic metal & damages central nervous system, attacks a number of different target organs

Smog -

Smog = noxious mixture of air pollutants (NOx, VOCs, SO2, CO) that can be seen as haze in the air - Sunlight causes the combination of VOCs & NOx to produce photochemical smog & increase the ground-level ozone

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Ozone → strong oxidiser that affects the respiratory system, damages cilia and alveioli cells, as well as immune system

Effects on Vegetation -

Necrosis (collapse of leaf tissue) Chlorosis (bleaching or other colour changes) Alterations in growth

Global Air Pollution Issues -

Three principal issues of global concern are - Acid rain - Climate change - Ozone layer depletion

Land - Sea Breezes

Lapse Rates -

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Dry Adiabatic Lapse Rate (DALR) - Ratio for expressing temperature change against altitude under ideal-gas law Environmental (ambient) lapse rate (ELR) - Normal lapse rate measured with a thermometer, but varies widely depending on location & time of day

Temperature Inversions - Extreme case of atmospheric stability, creating virtual lid on upward movement of pollution 1. Radiation Inversions a. Occurs when Earth’s surface cools rapidly → formation of fog & create concentration of pollutants 2. Subsidence Inversion a. Associate with high-pressure system and affects the dispersion of pollutants over large regions i. Interaction between warm air and cool air. 3. Frontal Inversion

Removal of Dry Particulate Matter -

Most common devices - Gravity settlers - Removing

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solid

and

liquid

waste

from

gaseous

streams

Cyclones (centrifugal) - Large particulates - Use centrifugal principals to collect dust on bottom, gas rises to top Electrostatic precipitators - Electrical forces to move particles out of the flowing gas stream (99% removal for small particles) Wet scrubbers - Remove mid-sized particulates and gaseous pollutants - Employ principle of interior impingement and interception of dust particles by droplets of water

Baghouse - Most commonly used and capable of removing small particles

Noise Pollution Nature of Sound -

Loudness has relationship with sound pressure Sound needs media to transmit

Sound Pitch & Frequency -

Young man→ 20 - 16,000 Hz Children & women → 20,000 Hz, Speech zone → 500 - 2,000 Hz Ear is most sensitive to range of 2,000 - 5,000 Hz

Unit of Sound -

Perceptible sound pressure is 20uPa to 20 Pa Sensation of loudness of sound is not proportional to energy intensity - Logarithmic function

Sound Power Level (PWL) -

Waves of sound pressure transmit energy in direction of propagation of wave

Sound Pressure Level (SPL) -

Sound = variation in pressure

Relation Between PWL & SPL -

Perceived sound is related to noise source’s environment (spherical / hemispherical radiation)

Sources of Noise

Types of Noise -

Continuous / steady - Cause fatigue / hearing impairment Variable Intermittent - Annoying and cause accidents Impulsive / impact

Hearing Impairment

Hearing Loss -

Important variables in development of hearing loss - Sound level

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Frequency distribution of sound Duration of sound Temporal distribution of sound expose Individual differences in tolerance Type of sound

Ambient Noise Standards

Reducing Noise Pollution -

Reducing sound produced Interrupting path of sound Protecting recipient

Lecture 2 - Water Pollution Water Cycle

Water Pollution -

Water Pollution → change in natural state of water caused by man-made activities - Concentration of substances in water to a level that adversely effect any organism & ecosystem

Sources of Pollution

Effects of Water Pollution

Types of Pollutants 1. Organic Pollution -

Organics = any material can be oxidised in water with dissolved oxygen Sources → food, paper industries, domestic wastewater etc… Dissolved Oxygen [DO] is great threat to aquatic life

Effect of Organic Pollution on DO levels in River

Oxygen Sag Curve

Photosynthesis -

Converts CO2 into organic compounds using sunlight

2. Nutrient Pollution -

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Nutrient concentrations allow excessive growth of aquatic plants - Pollutants Eutrophication → process of nutrient enrichment

Sources of Nitrogen (N) & Phosphorus (P)

Effect of Eutrophication -

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Algae bloom - Eventually die and decompose - Depletion of DO in water Objectionable colour, turbidity Reduce the water acceptability

Control of Eutrophication

2. Pathogens -

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Pathogen → organism that creates disease Sources - Garbage - Compost - Sewerage - Industry Effect - Infectious disease - Human / animal carrier - Cause death

Classifications

Pollution Indicator

4. Toxic Compounds -

A toxin is only toxic once absorbed at high levels

LC50 Toxicity Test -

Concentration of the toxicant to kill 50% of testing animals during exposure

Heavy Metals

Pesticides

Impact of Heavy Pesticide Exposure

Toxic Chemicals

Variation in Dioxin Toxicity

Bioaccumulation / Biomagnification

Biophysical Alteration

5. Thermal Pollution -

Sources - Industrial wastes (steam electric power plant) Effect - Rise in temperature of receiving water - Reduce density of water - Reduce dissolved oxygen in water - Increase metabolism - Effect aquatic life - Alter ecology of water

Cooling Tower / Pond

6. Oil Pollution -

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Toxic compounds - Benzene, toluene, PCBs, lead - Floating oil Effect - Acute effects on birds, fish, micro-organisms

Cleaning of Oil from beaches -

Mechanical cleaning - Sandy / pebble beaches - Pump ashore into tank

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Adsorption - Using straw Dispersants

6. Non-Toxic Salts -

Accumulation of salts / dissolved solids - Effect on usefulness of water uses - Major impacts on irrigated lands

Variation in Water Quality due to Sewage Pollution

Relationship between Water Uses & Water Quality Standards

Lecture 2B - Water & Wastewater Quality Indicators Physical Parameters Solids -

Suspended solids Dissolved solids

Conductivity -

Ability of water to conduct electricity Measure of concentration of dissolved salts / salinity of water

Turbidity -

Measure of the extent to which light is absorbed / scattered by suspended solids Impacts - Bad taste / odour - Disinfection level - Interfere with light penetration and photosynthetic reaction in water

Colour -

Apparent colour → colored by colloids / suspended solids True colour → coloured by dissolved substances Impacts - Unaesthetic - Unsuitable to laundering, dyeing, paper making, food processing … - Reduce effectiveness of chlorine as disinfectant - Carcinogenic products formed by combination of chlorine and other organics

Odor & Taste -

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Sources - Minerals, metals, salts from the soil and product from biological reactions of wastewater Impacts - Aesthetically displeasing - Some odour producing substances may be caused by a carcinogenic Measurements

Temperature

Chemical Parameters pH

Alkalinity -

Measure of concentrations of HCO3, CO3 & OH- Measured by titrating with HCl to certain end point pH values

Hardness -

Caused by salts of Ca & Mg Water hardness → water contacting soil and rock formations - Causes deposition of scale in boilers, damage in industrial processes

Hardness Measurements

Heavy Metals -

Most common = Iron, Nickel, Chromium, Copper, Zinc, Lead Measurement → Atomic Absorption Spectrometer (AAS)

Organic Pollution Dissolved Oxygen (Secondary Indicator) -

Secondary water quality parameter affected by actual pollutants Measure of free oxygen dissolved in water

DO Measurement -

Winkler

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DO Electrode Method

Titration

Method

Biochemical Oxygen Demand (BOD) -

Measure of oxygen requirement of a mixed population of aerobic, heterotrophic bacteria in oxidising the biodegradable organic carbon matter present in a water sample

BOD5 -

Is an indirect measure of concentration of biodegradable organic matter - Assumed that in 5 days, only carbonaceous matter is oxidised

NBOD & CBOD

Theoretical Oxygen Demand (ThOD) -

ThOD → amount of oxygen required to oxidise a known compound by theoretical calculation based on mass contaminant in the water

Chemical Oxygen Demand (COD) -

COD → measure of oxygen required to chemically (potassium permanganate / dichromate) oxidise organic matter present in wastewater

Total Organic Carbon (TOC) -

Measure of total organic carbon content in water

Nitrogen & Phosphorus Nitrogen

Phosphorus

Bacteriological Parameters Indicator Bacteria

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Equivalent weight = molecular weight divided by number equivalent in substance

Lecture 3 - Water Treatment Objectives of Water Treatment - Reducing microbiological contaminants - Removing physical constituents e.g. suspended solids

Common Steps in Water Treatment

Typical Water Treatment Processes:

Water Screening: 1. Removes coarse debris like logs, dead animals, trees etc. 2. Protects pumping units 3. Facilitates hydraulic flow in open channels Two types of screens: - Coats screens or bar racks - Fine screens A.K.A Fixed screens (racks and bars) or Moving screens (drums, belts)

Head Loss of Cleaning of Screening:

Micro Strainer - Removes algae, aquatic plants - Increase sand filtration efficiency - Stainless steel fabric or woven screens - Typical opening = 10 - 60 microns Limitations: - Unable to remove all algae - No effect on dissolved solids - Need UV light to limit biological growth - Unable to be a substitute for filters

Coagulation and Flocculation

Coagulation and Flocculation process is used to increase the particle size for efficient sedimentation. Flocculation can only operate where the particles are already destabilised. Two coagulant types: 1. Mineral - Mainly based on iron salta - Cationic charge is brought by the metallic ions - Universal range of application and low price 2. Organic - Cationic charge is brought by a quaternary ammonium function Factors affecting Coagulation: - Dose and type - PH level - Characteristics of particles e.g. size, shape

Common primary coagulant:

Jar test (Flocculation Test) To optimize the coagulation and flocculation process by determining the optimum pH,coagulant dose and mixing conditions (e.g. mixing speed (intensity) and mixing time etc.) 1. Prepare coagulatns 2. 1L sample is placed on jar test apparatus and impeller speed set to max 3. Inject coagulant, maintaining speed 4. Set timer 5. Settlement Secondary Coagulant:

Rapid Mixing Hydraulic mixing = more economical due to absence of moving parts and power Mechanical mixing = more widely used easy operation

Slow Mixing

Hydraulic = baffle type Mechanical = paddle, turine, propeller

Design Consideration -

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Mixing intensity - Very quick in rapid - Very slow in flocculation Mixing time - Short duration for rapit - Longer for flocculation

Velocity gradient (G) = degree of mixing - Higher G = more violent

Typical G and t for Rapid Mixing

Typical G and t for Flocculation

Examples Design a rapid mixing unit for a flow of 300 L/s. Assume that the period of rapid mixing is 30 s and respective G is 800 s1. What is the volume of the rapid mixer and what is the power required to drive the motor? (μ = 10 X 10-3 Pa.s (Ns/m2) and 1 HP = 0.746 kW)

A flocculator tank is 2m high, 2m wide and 6m long. The tank consists of one mechanical mixer. The diameter of the impeller is 1.5 m and the rotational speed is 50 rpm. If the impeller constant k = 0.9, determine the power required in HP and the velocity gradient achieved in the flocculator. Discuss what type of raw water can effectively be treated using this flocculator. Assume μ = 10 10-3 Ns/m2 ( Pa.s) and ρ = 1000 kg/m3 (1 HP = 0.746 kW)

Settling

Stoke’s Law: Settling velocity of a particle in a sedimentation tank:

Design Parameters for Sedimentation:

Example: A rectangular settling tank with a length: width ratio of 3 treats water at 850 m3/d. The retention time is 2.4h and depth 4m. What would the overflow rate be and the horizontal velocity assuming an even velocity distribution through the settler?

Water Softening Influent water passes downward through the bed of ion exchange material to the effluent

Hardness = Carbonate hardness + non-carbonate hardness

Benefits of water softening: Protects hair and skin Less scaling and stains Saves money -

Reduced energy consumption Protects lenient Makes dishes cleaner Retains beneficial minerals

Lime-Soda Softening

Ion Exchange Softening

Filtration -

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Raw water is passed through a porous medium to remove undesirable characteristics - Biological - Physical - Chemical - Bacteriological Slow sand filtration and rapid sand filtration

Slow Sand Filtration:

Example: Design slow sand filter for the following details • Population: 100,000 people • Per Capita Demand: 150 l/day • Total maximum demand: 1.5 times average Indicate general arrangements of filter bed.

Slow vs Rapid Sand Filter

Disinfection Good disinfectant should be - Toxic to microorganisms - Fast kill rate - Prevent regrowth of organisms

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Produce no or minimal harmful by products

Rate of Kill of Organisms:

Type of disenfection: - Free chlorine - Chloramines - Chlorine dioxide - Ozone - UV - irradiation

Lecture 4 - Prelim. & Primary Wastewater Treatment Chemical Constituents of Wastewater -

Organic matters → such as carbohydrates, fats, oils, grease, proteins, surfactants, volatile organic compounds and toxic chemicals Inorganic matters → heavy metals, nutrients, pH, alkalinity, chlorides, sulfur Gases → CO2, N2 etc..

In Domestic Raw Wastewater -

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Typical total nitrogen = 25 - 85 mg/L - Ammonia + nitrate, nitrite + organic nitrogen - Ammonia nitrogen = 12 - 50 mg/L - Organic nitrogen = 8 - 35 mg/L Phosphorus - Typical = 2 - 20 mg/L - Organic = 1 - 5 mg/L - Inorganic = 1 - 15 mg/L BOD5 = 100 - 250 mg/L

Biological Wastewater -

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Characteristics

of

Microorganisms - Bacteria - Fungi - Protozoa - Microscopic plants & animals - Viruses Most microorganisms (bacteria, protozoa) are beneficial for biological treatment and others (viruses, fungi, bacteria) are of public concern Indicator bacteria - Total fecal coliform (TC) - Fecal coliform (FC) - Fecal streptococci (FS)

Wastewater Treatment Plant

Removal Efficiencies

Preliminary & Primary Treatment -

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Removing solid particles - Sewage is filtered through screens to take out solid matters (cotton buds, paper) and heavy particles (sand) sinks and is removed - Sewage then flows to the primary sedimentation tanks - Human waste (sludge) settles to bottom - Oils float and are skimmed off Municipal wastewater treatment - Only settling of particles by sedimentation - 60-70% of SS removal - 20-30% BOD removal

Grit Removal -

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Constant velocity grit chambers - Flow controlled by special influent distribution gates and weir sections at effluent end - Remove all grit particles > 0.2mm - Retain organic particles suspended in flow Spiral flow grit chambers - Type of spiral flow grit - No washing of grit - Transverse rolling motion to the flow - Air is injected - Grit collection and removal is facilitated by sloping the tank floor to allow grit to settle

Design of Constant Velocity Grit Chambers

Sedimentation Tank

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Sedimentation tank vs. water treatment - More suspended solids - Wastewater suspended solids are lower specific gravity - No chemical are employed - Effluent contains more suspended solids - Sludge has to be removed continuously to prevent septic condition

Types of Sedimentation Basins

Rectangular sedimentation Tank - 4 Zones

Lecture 5 - Current Status of Wastewater Treatment in Sydney Degree of Wastewater Treatment

Determination of Water Quality Parameters -

Overall waste characterisation is not sufficient - Need to characterise the individual waste streams (daily / monthly)

Solids -

SS such as TSS & VSS and settleable solids - affect the operation and sizing of treatment units

Turbidity -

A measure of the extent to which light is absorbed / scattered by suspended materials Impacts - Undesirable taste & odor - Disinfection level - Interfere with light penetration

ColoSorryur -

Industrial wastes (textile dye, mining, paper production etc..) cause various colours Impacts - Aesthetically unacceptable & toxic - Reduce effectiveness of chlorine as disinfectant

Odor -

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Sources - Minerals, metals, salts and product from biological reactions and constituents of wastewater Impacts - Aesthetically displeasing - Some odor producing may be carcinogenic

Temperature -

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