environment Flashcards
layers of atmosphere
higher limit of layers troposphere - 7~16 km stratosphere - 50 km mesosphere - 80 km thermosphere - 500 km
types of domestic solid waste and their densities
garbage - 90~450 kg/cum (Biodegradable)
rubbish - 50~400 kg/cum
ashes - 700~850 kg/cum
disposal methods of refuse
sanitary land filling composting incineration and thermal pyrolysis dumping into the sea pulverization and shredding autoclaving
what is lechate
acid + alcohol+ RUbbish +water
points on sanitary land filling method
- refuse is dumped in low lying areas of approx 1.5m
- each layer is being properly compacted to left for
at-least 7 days - sealants (rubber, p.v.c, butylechloride, clay, asphalt) for lechate
- DDT sprayed to avoid insect or flies
- aerobic and anaerobic decomposition occur
- moisture content > 60%
- time taken 2~12 months, height will be reduced by 40%
- disadvantages - lechate and gas formation
incineration vs thermal pyrolysis
incineration - high calorific value , burning in presence of oxygen
thermal pyrolysis - absence or limited availability of oxygen
wind velocity at any height Z
Vz = U *(Z/Z0)^k
k =~ 1/9 for large lapse
= 1/3 for marked inversion
=~ 1/7 for avg NORMAL
why chlorine is used in skimming tank
to destroy the colloidal effect of proteins that hold the oil and grease in form of emulsion
settling type 1
points
- no change in shape and size
- velocity can be calculated via stokes law or transition law
- takes place in plane sedimentation tank and grit chamber
type 2 settling
points
- flocculent setteling
- lower concentration < 1000 mg/l
- in clarifloculators and PST
type 3 settling
points
- zone or hindered settling
- intermediate concentration ~ 1500 mg/L
- after activated sludge process
type-4 settling
points
- compression settling
- high concentration 1800~2000 mg/L
- used after trickling filter
primary sedimentation tank design parameters
OFR = 25-30 m/day depth = 2.5-3.5 m detention = 2-2.5 hr horizontal vel < 0.3 m/min minimum width = 6m L/B = 4~5
ambient noise pollution levels permissible
Area - day- night industrial - 75 - 70 commercial - 65 - 55 residential - 55 - 45 silence zone- 50 - 40
coagulation aided sedimentation in sewage water
- not generally used because it impact the health of microorganisms
- can be used in hilly areas because of low area available
- can be used to remove nitrogen and phosphorus from wastewater , and avoid eutrophication
anaerobic sludge digestion microorganisms involved process key points
acid formers- facultative bacteria which ferment waste water into acids and alcohols , these microorganisms responds very quickly
methane formers- strictly anaerobic micro-organism which utilizes acid and alcohols, very delicate against shock loading , narrow pH (6.5-7.5)
standard rate sludge digestor anaerobic (SRSD) design parameters
dia = 6-18m depth = 6-12 m dia/depth = 1.5~4 V = 1/3 V1 + 2/3 V2
factors affecting sludge digestion process
temperature - thermophillic and mesophilic
pH = 6.5~7.5
nuisance causing bacteria - they reduces sulphates into sulphide which is disastrous for bacteria , this can be avoided by introducing fe, feS will form
radius of influence (R) in aquifer well according to Sichardt equation
R = 3000Ssqrt(K)
daracontiasis disease
gunia worm disease, parasite
hydraulic loading rate and recirculation ratio of SRTF, HRTF, S-SRTF
m/day
1~4 :: 0
10~40 :: 0.5~3
40~200:: 1~40
re-circulation factor related to recirculation ratio
(1+R) / (1+0.1R)^2
Aerobic suspended growth system phases
Aerobic suspended growth system
-Phase1 -Lag phase
mic-org gets accustomed to food and environment
cell division occur
-phase2- Log phase
ASP is tried to be maintained in this phase
-phase3 -stationary phase
-Phase4 -Endogenous phase
aeration types in ASP
complete mix regime-
machenical aerators can be used
F/M ratio can be kept constant
for < 25MLD
plug flow regime-
long channel moving progressively
F/M decreases along length
for Q > 300MLD
extended aeration process, key points
extended upto phase4- endogenous
PST is avoided in this
SEPTIC tank
detention time= 12~36 hrs
cleaning time = 6~12 months
rate of accumulation of sludge is 30-50 L/c/y
anaerobic reaction
SST secondary sedimentation tank
concentration of biological solids
after ASP or trickling filter
sanitary sewage and sullage
sanatarty sewage- mix of domestic and industrial sewage
sullage- kitchen and bathroom
how to measure COD
by adding K2Cr2O7 (potassium dichromate) and H2SO4
and noting the oxygen used
po-dicr decomposes some inorganic compounds also so it will report higher cod
it can also be called as dichromate demand
de oxygenation and re-oxygenation constant depend upon temperature
Kd = K20 * [1.047]^(T-20) Kr = K20 * [1.016]^(T-20)
Relative stability of sewage
S= 100* [1- 0.794^t], for t = time at 20 Celsius
S= 100* [1- 0.630^t] for t = time at 37 celcius
t = time required to decolorize standard methelene blue solution at particular temp
decolorisation happens due to anaerobic bacteria
zones of pollution in river stream
zone I - clear water
zone II - degradation zone
dark and turbid
no algae, but fish survive
zone III - active decomposition darker and heavy pollution D.O may fall zero- anaerobic conditions dirty scum layer fish cant survive
zone IV - zone of recovery
being decomposed upto nitrate level
fish and algae reappear
stratification in lakes
epilimnion - upto 1 m
0.5m= thermolline or metalimnion
1m = hypolimnion
classification of lakes according to productivity
oligotropic lakes- least productive
freshwater, full sunlight penetration, fully aerobic
mesotropic lakes- medium productive
eutropic lakes - highly productive
high algae , anaerobic conditions
senescent lakes- old lakes that are converted into marshy land
physical water quality parameters and limits
suspended solids= 500 mg/L, 2000 mg/L turbidity = 1 NTU, 10 NTU color = 5TCU, 25 TCU taste and odour , 1 TON, 3 TON Temprature = 10~25 deg. Celsius
suspended solids impact and measurement of concentration
it can provide carbon it can provide adsorption surface measurement -can be separated by heating at 104°C for total and 600°C for inorganic - graviometric technique limit= 500 and 2000 mg/L
chemical water quality parameters and limits
Alkalinity = 200 mg/L and 600 mg/L
pH = acceptable limit ( 7.0-8.5) and (6.5-9.2)
Hardness = MgSO4 (50 mg/L), total 200 and 600 mg/L
for domestic supply 75~115 mg/L
Free Ammonia (0.15mg /L)
organic ammonia = (.3 mg/L)
Nitrite = zero
Nitrate = 45 mg/L
Fluride content = (1 - 1.5 mg/L)nitrogen related bacteria
NH3 – notrosomonous– NO2– nitrobacter– NO3— paracocuous Denitrificants – N2
metal content limits
Na = 5g/day Fe = (0.1 - 1 mg/L) Mn = (0.05-0.5 mg/L) Cu = (0.05 mg/L, 1.5 mg/L)
disease caused by bacteria, virus
Bacteria = typhoid, Cholera, Dysentry Virus = Hepatitis ,(Jaundice), polio protozoa = Amoebic DYsentry
pH measurement
phenopthelene indicator
methyl orange
calomel electrode pH meter
measurement of hardness
Versanate solution = 0.01M EDTA[ethelene di-amine tetra acetic acid]
indicator = EBT erichrome black-T
measurement of ammonia and organic ammonia
free ammonia by boiling and noting the ammonia gas released
organic + free = KJHELDHA’S Ammonia
by adding KMnO4
measurement of Nitrite and Nitrate
color matching technique
sulphonic acid + KOH (Nitrite)
Phenol di-sulphonic acid & KOH. (Nitrate)
measurement of fluride
color matching technique
zirconioum ion and Alezarin (Reddish brown)
measure dissolved oxygen
winklers method MnS04 + NaOH + KI added I is released in water measured by titrating with 0.01 Na2S2O3 Blue color Iodide until decolorise
testing of pathogen
MPN method
Membrane filter technique
CI
sludge bulking and its remedies
happen in ASP caused by filamentous micro organisms and sludge settling characteristics are very poor in this case can be controlled by -adjusting F/M -raising or lowering D.O -using disinfectant (chlorine)
water treatment process chain
screening aeration coagulation and floculation sedimentation filtration softening fluoridation De-fluoridation De-salination De-ferrization disinfection
head loss through screening
HL = k/2g * (V^2 - U^2) k/2g= 0.0729
quiescent type sedimentation tank
detention time 24hr
cleaning time 6~ 12 hrs
minimum 3 units
types of water sedimentation tank
quiescent type
horizontal flow type
vertical flow type
horizontal flow type sedimentation tank
overflow rate
plane sedimentation =12-18 m/day, T= 4-8 hr
coagulated sedimen = 24-30 m/day, T= 2-4 hr
horizontal flow velocity = (0.15-0.9) m/min
generally v= 0.3 m/min
vertical flow type sedimentation tank
VOlume = D^2 (0.011D +0.785*H)
Alum key points
Al2.(S04)3 *18H2O =666 g react with 3 Ca.(HCO3)2 = 3*[162] = 486 g make 2 moles of sticky gelatinous Al.(OH)3 = 2*[78] = 156 g --1g alum+ .73g Ca.(HCO3)2[0.45g alk] = .234 Al(OH)3
normal dose of alum = 10-30 mg/L
pH range = 6.5~8.5
copperas
FeSO4 *7H20 pH >8.5 always used with lime Fe(OH)3 formed same dose as alum but cheaper generally not used in water treatment or colored water
chlorinated copperas
Fe2.(S04)3 + fe.Cl3
pH range (4-7) and above 9 when alone
pH (3.5 to 6.5) and >8.5 with Fe.Cl3
sodium alluminate coagulant
reacts with Ca and Mg present in water and make gelatinous precipitate
no alkalinity required
removes temporary and permanent hardness also
costly then alum
can be used for boiler feed water
pH (6-8.5)
G value for coagulation and floculation
Gc = 300, T =30-60 sec Gf = (10-75),
removal of impurity in filter by mechanisms as follow
mechanical straining sedimentation biological changes (SCHMUTZDECKE) Electrolytic changes
slow sand filter
depth = 2.5 - 3.5 m (sand+gravel) rate of filtration = 0.1 to 0.3 m/s area of each unit = 100-200 m^2 Cu[D60/D10] = (3-5) BOD removal 98-99 % effluent free from (C,N,S,P,Fe) if turbidity > 50 NTU, dont use
operational troubles of rapid sand filter
Air binding - due to negative pressure
head loss increases
dont let HL >(2.5-3.5)
Mud ball formation - Inadequate washing
medium particles get removed due to turbulence generated and efficiency decreased
Cracking of filter - alternate wetting and drying
shrinkage cracks
chlorine disinfection chemical forms
Cl2 + water = HOCl + HCL pH >5
HOCl = OCl + H+ [pH >8]
chloroamenes
Cl2 - [pH>7.5] NH2Cl – [pH<6.5] NH.CL2 –[pH<4.4] N.CL3
Normal dose = 0.2mg/L residual
types of chlorine added to water
Free chlorine [T (32-48 C)]
Hypochlorite (HOCl) & Bleaching powder (CaOCl2)-
1g OCl = Ca(OCl)2 [0.72g] = CaOCl2 [0.4 g]
CHloroamines
Chlorine Dioxide - 2.5 times effective then free chlorine
pH (8-10)
different types of chlorination methods (quantity)
Break point chlorination [0.2mg/L resid.]
Plane chlorination [(0.5-0.6 mg/L), turbidity<30NTU,]
pre chlorination [5-10 mg/L(coag.), 0.1-0.5 mg/L(filtration) ]
post chlorination [0.2mg/L , 10 min]
double chlorination [post + pre]
super chlorination [5-15mg/L, 1-2mg/L(residual)]
testing of chlorine
Orthotolidine test
Starch Iodide test
DPD & CHlorotex test
De-chlorination
[sodium thiosulphate, sodium meta bi sulphate, sodium bi-sulphate, Ammonium hydroxide, Activated carbon]
Softning methods
Lime soda
Zeolite process
air pollution impacts on surrounding environment
ozone depletion
acid rain
global warming
discharge consideration for self cleansing and maximum design discharge
Q.min =1/3 *Q.avg
and
Q.des =3 *Q.avg
free-board of septic tank and oxidation pond & Sedimentation tank
septic tank = 0.3 m
Sedimentation tank = 0.5m
oxidation pond = 1 m
good settling sludge SVI
50-150 mg/L
settling formula according to temperature
Vs = 418 (G-1) d^2 *(3.T+70)/100
speed and size in mm, T in °C
Vs =[ρ.g(G-1)d^2] /(18.μ)
in S.I units
μ = 8.90 × 10−4 Pa·s at 25 °C
removing fluorides from water
(i) Absorption by activated alumina (AA), commonly known as Prashanti Technology.
(ii) Nalgonda technique.
(iii) Ion exchange adsorption method.
(iv) Reverse osmosis process
Prashanti Technique
In this method raw water containing high contents of fluoride, is passed (percolated) through the insoluble
granular beds of activated alumina (AA), or activated carbon; which adsorbs fluoride from the percolating
water, giving out defluoridated water.
Activated alumina is an excellent medium for removal of excess fluoride than other adsorption media.
The adsorption process is best carried out under slightly acidic condition (pH = 5 to 7).
Nalgonda Technique
Mainly used in rural areas, ground water containing excess fluoride.
Nalgonda technique uses aluminium salt (alum) for removing fluoride.
The raw water is firstly mixed with adequate amount of lime (CaO) or sodium carbonate (Na2CO3) and
throughly mixed.
Alum solution is then added, and water is stirred slowly for about 10 min, and allowed to settle for nearly
one hour.
The precipitated sludge is discarded, and the clear supernatant containing permissible amount of fluoride
is withdrawn for use.
