Water Quality

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Water Quality

• 1. Physical quality
• 2. Chemical quality
• 3. Biological quality

Physical parameters - temperature -
turbidity - taste and odor - color
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Chemical parameters - pH range 6-8 -
Acidity CO2, HCO3-, H2CO3- - Alkalinity
OH-, CO32-, HCO3- - Hardness carbonate and
non- carbonate - Chloride -
Conductivity - Dissolved oxygen - Fe, Ca,
Cu, Zn, Na
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Chemical parameters (cont.) - Nitrogen NH3 ,
NO2-, NO3- - Sulfate - Solids -
Fluoride, Silica - Phenolic cpd. - Toxic
metals e.g. Cd, As, Cr - Detergents -
Organochlorine cpd., PCB - Radioactive -
Oxygen demand e.g. BOD, COD, PV
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Biological parameters - Total plate count -
Coliform bacteria (MPN) - E. coli - Enteric
pathogen
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Surface water quality
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Surface water quality
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Surface Water Quality Standards
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Bottled Drinking Water Quality Standard
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Bottled Drinking Water Quality Standard (cont.)
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Pathogen and Parasites found in Wastewater

• Bacterial pathogens
• Salmonella Yersinia
• Shigella E. coli
• Vibrio cholerae Bacteroides fragilis
• Leptospira
• Legionella pneumophila
• Campylobacter

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• Viral pathogens
• Hepatitis
• Viral Gastroenteritis
• Protozoan parasites
• Giardia lamblia
• Cryptosporidium
• Entamoeba histolytica
• Helminth parasites
• Taenia spp.(tapeworm)
• Ascaris lumbricoides (roundworms)

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Water Treatment

• 1. Type
• Slow sand filter for small community
• Rapid sand filter generally use especially
• for big community
• Water softening plants when raw water has
  hardness higher than standard
• - Zeolite softening plants
• - Lime soda plants
• - Combined lime and Zeolite softening plants

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Coagulants
Cl2 and/or F2
Lake or Reservoir Supply
Rapid Flocculator mix
Settling tank
Filter
Distibution System
Coagulants
Prechlorination
Sedimentation tank
Rapid Flocculator mix
Presedi- mentation
Filter
River Supply
Postchlorination
Clear well
Distibution System
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• 2. Pretreatment
• Presedimentation Raw water storage
• Screening bar screen
• drum screen

3.Coagulatiuoun Flocculation factors affected
coagulation and flocculation - pH - salts -
turbidity - coagulants - mixing - physical
condition e.g. temp.
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• Alum or Aluminum Sulfate (Al2(SO4)3 .18 H2O)
• ?????????????????????????????????????????????
  ?????????????????????????? ??????????????????????
  ??

Al2(SO4)3. 18 H2O 3 Ca(HCO3)2
2Al(OH3) 3CaSO4 6CO2 18 H2O
Al2(SO4)3.18 H2O 3Na2CO3 2Al(OH)3
3Na2SO4 3H2O 3CO2 18 H2O
Al2(SO4)3.18 H2O 3Ca2(OH)2
2Al(OH)3 3CaSO4 18H2 O
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• Ferrous Sulfate (FeSO4 . 7H2O)
• ??????????????????????? ????????????????????????
  ?????????

????
????
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• Ferric Sulfate (Fe2(SO4)3)
• ????????????????????????????? pH 4.0 - 11.0
  ???????????????????
• ???? pH ??? ??????????? Fe ??? Mn
  ?????????????????????????? pH ???

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• Ferric Chloride (FeCl3)
• ?????????ferric chloride ????????????????????????
  ???????????? ??????????????????????

Coagulant Aid - lime, quick lime
(CaO),Ca(OH)2 - Na2CO3 - H2SO4 - NaOH -
Activated silica
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• 4. Rapid Mixing
• ????????????????????????????????????????????????
  ?????????????
• 5. Flocculation
• ????????????????????????????????????????????????
  ??????????????????? ? ??????????????????????????
  ?????????????
• ??????????????????????????????????
• 6. Sedimentation
• - discrete settling
• - flocculant settling
• - zone settling
• 7. Filtration
• - Slow sand filter
• - Rapid sand filter
• - Pressure filter

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Water Disinfection

• Chlorination

100
0
Cl2 H2O HOCl H Cl-
HOCl H OCl-
OCl -
HOCl
HOCl, OCl- free available chlorine HOCl NH3
or org.cpd. Chloramine
100
0
pH
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• the effectiveness for the inactivation of m.o. in
  water and wastewater
• HOCl gt OCl - gt NH2Cl
• Chlorine can injure the bacterial cells
• disruption of cell permeability
• damage to nucleic acids and enzymes
• killing action of free Cl2 can be potentiated by
  adding salts e.g. KCl, NaCl, or CsCl
• the disinfecting ability of chlorine can be
  enhanced in the presence of heavy metal

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• Disinfection efficiency of Chlorination relate to
  the residual chlorine and contact time

Y/Yo (1 0.23 ct)-3
Y residual coliform bact after contact with
chlorine,MPN/100 ml Yo
coliform bact before contact with chlorine,
MPN/100 ml c chlorine residual, mg/l t
contact time, min
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• effect of Cl2 and Cl2 by products
• - risk of colon and bladder cancers
• - Trihalomethane (THM) produced by
  Cl2 suspected carcinogens

THM - Chloroform, Dichloromethane, Bromoform,
1,2-Dichloroethane, Carbontetrachloride
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• Chloramination

NH3 HOCl NH2Cl H2O
NH2Cl HOCl NHCl 2 H2O
NHCl2 HOCl NCl3 H2O
chloramine do not react with organics to form
Trihalomethane proportion of the three forms of
chloramines depends on the pH of the water
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• Monochloramine is predominant at pH gt 8.5
• Monochloramine and dichloramine coexist at pH
  between 4.5 and 8.5
• Trichloramine is formed at pH lt 4.5
• The mixing of chlorine and ammonia produces a
  chlorine dose-residual curve

Zero chlorine demand curve
Chlorine Residual (mg/l)
Breakpoint
Mostly free Cl2
Chlorine Dose (mg/l)
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• at breakpoint, chloramine is oxidized to N2 gas
  when ratio Cl2 NH3 is between 7.5-11 1
• 2NH3 3HOCl N2 3H2O 3HCl
  
• the bactericidal activity of chloramine increases
  with temperature and H concentration
• Mycobacteria, some enteric viruses, and protozoan
  cysts are quite resistant to chloramine

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• Dichloramine and trichloramine have offensive
• odors (threshold concentration 0.8 0.02 mg/l,
• respectively)
• Chloramines cause hemolytic anemia in kidney
• hemodialysis patients
• Chloramines are toxic to fish and invertebrates

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• Chlorine dioxide (ClO2)

not appear to form THM, nor react with NH3
must be on-site generation, because it cannot be
stored in compressed form in tank used as
preoxidant (organic matter, color, Fe, Mn) and 1o
disinfectant (followed by addition of chlorine)
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• fast-acting and effective equal or superior to
  Cl2
• in inactivating bacteria and viruses in water and
  
• wastewater
• ClO2 disrupt the protein synthesis in bacterial
• cell and protein coat in viruses
• Chlorite is of great health concern than chlorate
• both may combine with hemoglobin to cause
• methemoglobinemia

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Ozone (O3)

• use as 1o disinfectant to inactivate patho. m.o
• oxidation of Fe, Mn, color, taste and odor
  causing compounds, refractory organic and THM
  precursor
• effectiveness varies greatly with temp. and not
  controlled by pH
• much more powerful than chlorine but more
  expensive

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• m.o. resistant to O3
• Mycobacterium fortuitum gt Poliovirus type 1 gt
  Candida parapsilosis gt E. coli gt S. typhimurim
• Peroxone process (H2O2 O3 0.3 or less) is
  similar to O3 alone
• O3 produce free radicals in aqueous media that
  inactivate m.o
• O3 affects permeability, enzyme activity, and DNA
  of bacterial cell and damage nucleic acid core in
  viruses

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• Ultraviolet light

use low-pressure mercury lamps enclosed in quartz
tubes tubes are immersed in flowing water in a
tank and allow passage of UV radiation at the
germicidal wavelength of 2,537 A UV damages the
viral genome and viral coat UV damages microbial
DNA and causes thymine dimerization
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• microbial inactivation is proportional to
• the UV dose (micro-watt-seconds per cm2)
• the resistance of m.o. to UV follows the
• same pattern as with chemical disinfectants
• protozoan cysts gt bact. spores gt viruses
• gt vegetative bact
• Many variables (SS, COD, color) and org.
• compounds (humic substances, phenolic cpds
• ferric ion) affect UV transmission in water

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• Advantages of UV disinfection
• - efficient inactivation of bacteria and viruses
  in potable water
• - no production of any known undesirable
  carcinogenic or toxic by-products
• - no taste and odor problem
• - no need to handle and store toxic chemicals
• - small space requirement

Disadvantages - no disinfectant residual in
treated water - difficulty in determining UV
dose - problems in maintenance and cleaning of
UV lamps - higher cost of UV disinfection than
chlorination