Wastewater treatment

Water & Wastewaters Treatment
10/9/2014 Waste treatment and cleaner Technologies

Distribution of water on earth
• Ocean and sea - 97%
• Snow and ice caps - 2%
• Rivers, lakes, Ground water - 1%

Safe drinking water
• Free from pathogenic organisms
• Clear
• Not saline
• Free from offensive taste or smell
• Free from compounds that may have adverse effect on human health
• Free from chemicals that cause corrosion of water supply systems

WATER QUALITY PARAMETERS
• Physical parameters
• Chemical
• Bacteriological

BUREAU OF INDIAN STANDARDS
IS 10500 -1991
Parameters Disirable limit Permissible limit
Colour Hazen unit 5 25
Turbidity- NTU 5 10
pH 6.5 - 8.5 6.5 -8.5
Hardness (as CaCO3)mg/l 0.3 1
TDS 500 22000

BUREAU OF INDIAN STANDARDS
IS 10500 -1991
Parameters Desirable limit Permissible limit
Nitrate mg/l 45 45
Chloride mg/l 250 1000
Flouride mg/l 1 1.5
Arsenic mg/l 0.05 0.05
Aluminium mg/l 0.03 0.2

Colour
• May be due to the Presence of organic matter, metals(iron, manganese) or
highly colored industrial waste
• Aesthetically displeasing
• Desirable that drinking water be colourless
• Desirable limit, 5 Hazen unit
• Permissible limit 25 Hazen Unit

Taste and Odour
• Mainly due to organic substances, ,Biological activity, industrial pollution
• Taste buds in the oral cavity specially detect inorganic compounds of metals like
magnesium, calcium, sodium, copper, iron and zinc
• Water should be free from objectionable taste and odour.

Turbidity
• Caused by suspended matter
• High level turbidity shield and protect bacteria from the action of disinfecting agents
• Desirable limit-5 NTU should be below 1 NTU when disinfection is practiced
Permissible limit-10 NTU

pH
• It is the measure of hydrogen ion concentration
• Neutral water pH-7
• Acidic water has pH below 7
• Basic water has pH above 7
• Desirable limit 6.5-8.5 Beyond this limit the water will affect the mucous membrane and
water supply system

Substances that change pH of water
Acidic Industries Basic industries
Sugar 5-6 Paper 8-10
Distillery 3-4 Textile 8.5-11
Electroplating unit 2.5-4 Fertilizer 6.5 - 9
Pickle 2-3 Oil Refineries 6.5- 9
Battery acids <1.0 Milk 6.7
Carbonated Beverages 2 – 4 Rain water 6.5
Lemon juice 2.3 Blood 7.5
Orange juice 4..2 Sea water 8.0
Vinegar 3 Ammonia solution 11.3
Domestic sewage 6.5-8.5 Ground water 7.5-8.5

HARDNESS
• Capacity of water for reducing and destroying the lather of soap
• It is total concentration of calcium and magnesium ions
• Temporary hardness – Bicarbonates of Calcium and Magnesium
• Permanent hardness – Sulphates, chlorides and nitrates of calcium and
magnesium
• 0 – 5 0 mg/ l - soft
• 50 – 15 0 mg/l - moderately hard
• 150 – 3 00 mg/l - hard
• 300 above - very hard
• Surface water is softer than ground water
• Causes encrustations in water supply structures

ALKALINITY
• Capacity to neutralize acid
• Presence of carbonates, bi-carbonates and hydroxide compounds of Ca, Mg, N a and K
• Alkalinity = hardness, Ca and Mg salts
• Alkalinity > hardness - presence of basic salts, N a, K along with Ca and Mg
• Alkalinity < hardness – neutral salts of Ca & Mg present

IRON
• One of the earth’s most plentiful resource
• High iron causes brown or yellow staining of laundry, household fixtures
• Metallic taste, offensive odour, poor tasting coffee
• Cause iron bacteria
• Acceptable limit – 0 .3 mg / l

CHLORIDE
Causes
• Dissolution of salt deposit
• Discharge of effluents
• Intrusion of sea water
• Not harmful to human beings
• Regarding irrigation – most troublesome anion
• Acceptable limit – 250 mg/l

NITRATE
Increasing level of nitrate is due to
• Agricultural fertilizers, manure, animal dung, nitrogenous
material ,sewage pollution
(blue baby diseases to infants)
• Maximum permissible limit 45 mg / l

FLOURIDE
• Occurs naturally
• Long term consumption above permissible level can cause – dental flurosis
(molting of teeth) and Skeletal flurosis
• Acceptable limit – 1 mg / l
• Maximum permissible limit – 1.5 mg / l
• Remedy – 1) Deflouridation
2) Mixing Fluoride free water
3) Intake of vitamin C, D, calcium, antioxidants

FLOURID E CAUSES
Three types of flurosis
1. Dental flurosis
2. Skeletal flurosis
3. Non-skeletal flurosis

A R S E N I C
• Occur in ground water from arseniferous belt
• Industrial waste, agricultural insecticide
• High arsenic causes 1) various type of dermatological lesions, muscular
weakness, paralysis of lower limbs, can also cause skin and lung cancer
• Acceptable limit – 0.05 mg / l

Heavy Metals
• Present as mineral in soil and rocks of earth
• Human activities
Battery – Lead & Nickel
Textile - Copper
Photography – Silver
Steel production – Iron

Pesticides
• Cancer
• Birth defects
• Blood disorder
• Nervous disorder
• Genetic damage

Common problems
Visible effects Reasons
Iron taste, change in colour after exposure to atmosphere, change in
colour of cloths, utensils Oily appeal- rance on top of water body Iron
Soap not lathering hardness
Brownish black streaks on teeth Fluoride
Growth of Algae Nitrate, phosphate
Fish kills Low pH less DO
water turns black, smell Waste water
Acidic taste Low pH
Alkaline taste High pH
Boiled Rice hard and yellow High Alkalinity
White deposits on boiling Hardness

Water
Quality DO (ppm) at 20°C
Good 8 –9
Slightly
polluted 6. 7 – 8
Moderately
polluted 4.5 – 6. 7
Heavily
polluted 4 – 4.5
Gravely
polluted
Below 4

• Dilution
• Biodegradation of wastes by
bacteria takes time
• Oxygen sag curve

Major Water Pollutants Have Harmful Effects
• Infectious disease organisms: contaminated drinking water
• The World Health Organization ( WHO)
– 3 Million people die every year, mostly under the age of 5

IMPORTANT WASTEWATER CONTAMINANTS
Contaminant Source Environmental significance
Suspended solids Domestic use, industrial wastes,
erosion by infiltration/inflow
Cause sludge deposits and anaerobic conditions in aquatic
environment
Biodegradable organics Domestic and industrial waste Cause biological degradation, which may use up oxygen in
receiving water and result in undesirable conditions
Pathogens Domestic waste Transmit communicable diseases
Nutrients Domestic and industrial waste May cause eutrophication
Refractory organics Industrial waste May cause taste and odor problems, may be toxic or
carcinogenic
Heavy metals Industrial waste, mining, etc. Are toxic, may interfere with effluent reuse
Dissolved inorganic solids Increases above level in water supply
by domestic and/or industrial use
May interfere with effluent reuse

Unit operations, unit processes, and systems for wastewater treatment
Contaminant Unit operation, unit process, or treatment system
Suspended solids Sedimentation
Screening and comminution
Filtration variations
Flotation
Chemical-polymer addition Coagulation sedimentation
Land treatment systems
Biodegradable organics Activated-sludge variations
Fixed-film: trickling filters
Fixed-film: rotating biological contactors
Lagoon and oxidation pond variations
Intermittent sand filtration
Physical-chemical systems
Pathogens Chlorination
Hypochlorination
Ozonation

Nutrients: Nitrogen Suspended-growth nitrification and denitrification variations
Fixed-film nitrification and denitrification variations
Ammonia stripping
Ion exchange
Breakpoint chlorination
Phosphorous Metal-salt addition
Lime coagulation; sedimentation
Biological-chemical phosphorus removal
Refractory Organics Carbon adsorption
Tertiary Ozonation
Land treatment system
Heavy Metals Chemical precipitation
Ion exchange
Dissolved inorganic solids Ion exchange
Reverse osmosis
Electrodialysis

Microorganisms
Classification:
 Heterotrophic- obtain energy from
oxidation of organic matter
(organic Carbon)
 Autotrophic- obtain energy from
oxidation of inorganic matter
(CO2, NH4, H+ )
 Phototrophic- obtain energy from sunlight

Biochemical Pathways
 oxidation of organic molecules inside the
cell can occur aerobic or anaerobic manner
 generalized pathways for aerobic &
anaerobic fermentation

Biochemical Pathways
C6H12O6 + 6O2 +38 ADP + 38 Pi 6 CO2 +38 ATP + 44 H2O
 aerobic pathways contains- EMP(Embden–Meyerhof–Parnas) pathways,
TCA(tricarboxylic acid cycle) cycle, respiration
 anaerobic pathways contains- EMP pathways
 released energy stored as ATP molecules
 excess food is stored as Glycogen

Embden-Meyerhof-Parnas pathway (EMP pathway), which was first
discovered by Gustav Embden, Otto Meyerhof and Jakub Karol Parnas.

Tricarboxylic acid cycle (TCA cycle), the Krebs cycle, or the
Szent-Gyorgyi–Krebs cycle

Biological growth
- exponential growth (batch)
- Monod kinetics
- Haldane kinetics
under toxic conditions

Biological growth...
 exponential growth
dX
dt
= X
Log No. of
Cells
Time
Lag phase
Log growth phase
Stationary phase
Death phase

Biological growth...
 Monod kinetics
Substrate Concentration (S)
Specific growth rate ( μ)
μ Max. rate m
μm/2
ks
S
m 
K S
μ μ
s


Treatment stages - Secondary
treatment
• Degrade biological content (dissolved organic
matter) of the sewage
– Ex: human waste, food waste, soaps, detergent
• Added bacteria and protozoa into sewage
• 3 different approaches
– Fixed film system
– Suspended film system
– Lagoon system

Biological Carbonaceous Removal
 aerobic
- oxidation
bacteria
CHONS + O2 + Nutrients CO2 + NH3 + C5H7NO2 + other end products
(organic matter) (new bacterial cells)
- endogenous respiration
bacteria
C5H7NO2 + 5O2 5CO2 + 2H2O + NH3 + energy (cells)

Biological Carbonaceous Removal
 anaerobic
Hydrolysis
Acidogenesis
Methenogenesis
Complex Organics
100%
20% 5%
60% 15%
Intermediates 15%
Propionate
35% 17% 10% 13%
H2 Acetate
72% 28%
Schematic of the Anaerobic Process
CH4

Biological treatment
– Trickling bed filter
– Activated sludge

• Fixed Film Systems
– grow microorganisms on substrates such as rocks,
sand or plastic
– wastewater is spread over the substrate
– Ex: Trickling filters, rotating biological contactors

Trickling filters bed
• Spread wastewater over microorganism
• made of coke (carbonized coal), limestone
chips or specially fabricated plastic media
• Optimize their thickness by insect or worm
grazing

Advantages
• Simple, reliable, biological process.
• Suitable in areas where large tracts of land are
not available for land intensive treatment
systems.
• May qualify for equivalent secondary discharge
standards.
• Effective in treating high concentrations of
organics depending on the type of medium
used.
• Appropriate for small- to medium-sized
communities.
• Rapidly reduce soluble BOD5 in applied
wastewater.
• Efficient nitrification units.
• Durable process elements.
• Low power requirements.
• Moderate level of skill and technical expertise
needed to manage and operate the system.
Disadvantages
• Additional treatment may be needed to meet
more stringent discharge standards.
• Possible accumulation of excess biomass that
cannot retain an aerobic condition and can
impair TF performance (maximum biomass
thickness is controlled by hydraulic dosage rate,
type of media, type of organic matter,
temperature and nature of the biological
growth).
• Requires regular operator attention.
• Incidence of clogging is relatively high.
• Requires low loadings depending on the
medium.
• Flexibility and control are limited in comparison
with activated-sludge processes.
• Vector and odor problems.
• Snail problems.

• Suspended Film Systems
– stir and suspend microorganisms in wastewater
– settled out as a sludge
– pumped back into the incoming wastewater
– Ex: Activated sludge, extended aeration

Activated sludge
• mixed community of microorganisms
• Both aerobic and anaerobic bacteria may exist
• Biological floc is formed

physical components of activated sludge process
• Aeration tank
– oxygen is introduced into the system
• Aeration source
– ensure that adequate oxygen is fed into the tank
– provided pure oxygen or compressed air
• Secondary clarifiers
– activated-sludge solids separate from the surrounding wastewater
• Activated sludge outflow line
– Pump activated sludge back to the aeration tank
• Effluent outflow line
– discharged effluent into bay or tertiary treatment plant

• Lagoon Systems
– hold the waste-water for several months
– natural degradation of sewage

Treatment stages – Tertiary treatment
• remove disease-causing organisms from wastewater
• 3 different disinfection process
– Chlorination
– UV light radiation
– Ozonation

What can effluent use for?
• discharged into a stream, river, bay, lagoon or wetland
• used for the irrigation of a golf course, green way or park
• If it’s sufficiently clean, it can be used for groundwater
recharge

Advanced Treatment
• Nitrogen removal
-)→ nitrate (NO3
– Ammonia (NH3) → nitrite (NO2
-)
• Phosphorous removal
– Precipitation with iron or aluminums salt
• Lead to eutrophication
• May cause algae bloom

Sludge treatment
• Primary sludge usually have strong odors
• Secondary sludge have high
concentration of microorganism
• Goals of treatments are:
– Reduce odors
– Remove water reduce volume
– Decompose organic matter

3 different sludge treatments
• Aerobic digestion
• Anaerobic digestion
• composting

Aerobic digestion
• Bacterial process
• Need oxygen
• Consume organic matter
• Convert into carbon dioxide (CO2)
Anaerobic digestion
• Bacterial process
• Do not require oxygen
• Consume organic matter
• Produce biogas, which can be used in generators for
electricity

Composting
• aerobic process
• requires the correct mix of carbon,
nitrogen, oxygen and water with
sludge
• Generate large amount of heat

Sludge disposal
• Superheat sludge and convert into small
granules that are rich in nitrogen
– Sell it to local farmer as fertilizer
• Spread sludge cake on the field
• Save landfill space

Water Quality Parameters and Definitions
Temperature it affects the amount of dissolved oxygen
Temperature also affects the rate of photosynthesis of plants, the
metabolic rate of aquatic animals, rates of development, timing and
success of reproduction, mobility, migration patterns and the
sensitivity of organisms to toxins, parasites and disease. Life cycles
of aquatic organisms are often related to changes in temperature.
Salinity Salinity is a measure of the dissolved salts in the water
pH pH is a measure of the acidity or alkalinity of water.
Turbidity a measure of the water’s murkiness. Turbidity is measured in
Nephelometric Turbidity Units (NTU’s).
Dissolved oxygen (do) The amount of oxygen in water
Conductivity Conductivity indicates the presence of ions within the water
Colour (Hazen) Colour is vital as most water users, be it domestic or industrial,
usually prefer colourless water
Total Suspended Solids, TSS
Total Dissolved Solids, TDS The total dissolved solids (TDS) in water consist of inorganic salts
and dissolved materials.
Biochemical Oxygen Demand, BOD BOD is a measure of organic pollution to both waste and surface
water
Chemical Oxygen Demand, COD
Ammoniacal Nitrogen
Potassium
Microbiological Total Coliform Count
Faecal Coliform Count
Pesticides Chlorinated, Glyphosphate, Paraquat ,Methamidaphos

Wastewater treatment

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