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Civil Eng Formulas + Buildings Short > environment > Flashcards

environment Flashcards

1
Q

layers of atmosphere

A 
higher limit of layers
troposphere - 7~16 km
stratosphere -     50  km
mesosphere -    80 km
thermosphere - 500 km
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2
Q

types of domestic solid waste and their densities

A

garbage - 90~450 kg/cum (Biodegradable)
rubbish - 50~400 kg/cum
ashes - 700~850 kg/cum

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3
Q

disposal methods of refuse

A 
sanitary land filling 
composting
incineration and thermal pyrolysis
dumping into the sea
pulverization and shredding 
autoclaving
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4
Q

what is lechate

A

acid + alcohol+ RUbbish +water

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5
Q

points on sanitary land filling method

A
  • 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
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6
Q

incineration vs thermal pyrolysis

A

incineration - high calorific value , burning in presence of oxygen
thermal pyrolysis - absence or limited availability of oxygen

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7
Q

wind velocity at any height Z

A

Vz = U *(Z/Z0)^k
k =~ 1/9 for large lapse
= 1/3 for marked inversion
=~ 1/7 for avg NORMAL

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8
Q

why chlorine is used in skimming tank

A

to destroy the colloidal effect of proteins that hold the oil and grease in form of emulsion

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9
Q

settling type 1

points

A
  • 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
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10
Q

type 2 settling

points

A
  • flocculent setteling
  • lower concentration < 1000 mg/l
  • in clarifloculators and PST
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11
Q

type 3 settling

points

A
  • zone or hindered settling
  • intermediate concentration ~ 1500 mg/L
  • after activated sludge process
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12
Q

type-4 settling

points

A
  • compression settling
  • high concentration 1800~2000 mg/L
  • used after trickling filter
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13
Q

primary sedimentation tank design parameters

A 
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
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14
Q

ambient noise pollution levels permissible

A 
Area             - day- night
industrial     - 75   - 70
commercial - 65   - 55
residential   - 55  - 45
silence zone- 50 -  40
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15
Q

coagulation aided sedimentation in sewage water

A
  • 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
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16
Q

anaerobic sludge digestion microorganisms involved process key points

A

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)

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17
Q

standard rate sludge digestor anaerobic (SRSD) design parameters

A 
dia = 6-18m
depth = 6-12 m
dia/depth = 1.5~4
V = 1/3 V1  + 2/3 V2
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18
Q

factors affecting sludge digestion process

A

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

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19
Q

radius of influence (R) in aquifer well according to Sichardt equation

A

R = 3000Ssqrt(K)

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20
Q

daracontiasis disease

A

gunia worm disease, parasite

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21
Q

hydraulic loading rate and recirculation ratio of SRTF, HRTF, S-SRTF

A

m/day
1~4 :: 0
10~40 :: 0.5~3
40~200:: 1~40

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22
Q

re-circulation factor related to recirculation ratio

A

(1+R) / (1+0.1R)^2

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23
Q

Aerobic suspended growth system phases

A

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

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24
Q

aeration types in ASP

A

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

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25
Q

extended aeration process, key points

A

extended upto phase4- endogenous

PST is avoided in this

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26
Q

SEPTIC tank

A

detention time= 12~36 hrs
cleaning time = 6~12 months
rate of accumulation of sludge is 30-50 L/c/y
anaerobic reaction

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27
Q

SST secondary sedimentation tank

A

concentration of biological solids

after ASP or trickling filter

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28
Q

sanitary sewage and sullage

A

sanatarty sewage- mix of domestic and industrial sewage

sullage- kitchen and bathroom

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29
Q

how to measure COD

A

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

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30
Q

de oxygenation and re-oxygenation constant depend upon temperature

A 
Kd = K20 * [1.047]^(T-20)
Kr = K20 * [1.016]^(T-20)
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31
Q

Relative stability of sewage

A

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

32
Q

zones of pollution in river stream

A

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

33
Q

stratification in lakes

A

epilimnion - upto 1 m
0.5m= thermolline or metalimnion
1m = hypolimnion

34
Q

classification of lakes according to productivity

A

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

35
Q

physical water quality parameters and limits

A 
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
36
Q

suspended solids impact and measurement of concentration

A 
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
37
Q

chemical water quality parameters and limits

A 
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)
38
Q

nitrogen related bacteria

A

NH3 – notrosomonous– NO2– nitrobacter– NO3— paracocuous Denitrificants – N2

39
Q

metal content limits

A 
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)
40
Q

disease caused by bacteria, virus

A 
Bacteria = typhoid, Cholera, Dysentry
Virus = Hepatitis ,(Jaundice), polio
protozoa = Amoebic DYsentry
41
Q

pH measurement

A

phenopthelene indicator
methyl orange
calomel electrode pH meter

42
Q

measurement of hardness

A

Versanate solution = 0.01M EDTA[ethelene di-amine tetra acetic acid]
indicator = EBT erichrome black-T

43
Q

measurement of ammonia and organic ammonia

A

free ammonia by boiling and noting the ammonia gas released
organic + free = KJHELDHA’S Ammonia
by adding KMnO4

44
Q

measurement of Nitrite and Nitrate

A

color matching technique
sulphonic acid + KOH (Nitrite)
Phenol di-sulphonic acid & KOH. (Nitrate)

45
Q

measurement of fluride

A

color matching technique

zirconioum ion and Alezarin (Reddish brown)

46
Q

measure dissolved oxygen

A 
winklers method
MnS04 + NaOH + KI added
I is released in water
measured by titrating with 0.01 Na2S2O3 
Blue color Iodide until decolorise
47
Q

testing of pathogen

A

MPN method
Membrane filter technique
CI

48
Q

sludge bulking and its remedies

A 
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)
49
Q

water treatment process chain

A 
screening
aeration 
coagulation and floculation
sedimentation
filtration
softening
fluoridation
De-fluoridation
De-salination
De-ferrization
disinfection
50
Q

head loss through screening

A 
HL = k/2g  * (V^2 - U^2)
k/2g= 0.0729
51
Q

quiescent type sedimentation tank

A

detention time 24hr
cleaning time 6~ 12 hrs
minimum 3 units

52
Q

types of water sedimentation tank

A

quiescent type
horizontal flow type
vertical flow type

53
Q

horizontal flow type sedimentation tank

A

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

54
Q

vertical flow type sedimentation tank

A

VOlume = D^2 (0.011D +0.785*H)

55
Q

Alum key points

A 
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

56
Q

copperas

A 
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
57
Q

chlorinated copperas

A

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

58
Q

sodium alluminate coagulant

A

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)

59
Q

G value for coagulation and floculation

A 
Gc = 300, T =30-60 sec
Gf = (10-75),
60
Q

removal of impurity in filter by mechanisms as follow

A 
mechanical straining
sedimentation
biological changes (SCHMUTZDECKE)
Electrolytic changes
61
Q

slow sand filter

A 
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
62
Q

operational troubles of rapid sand filter

A

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

63
Q

chlorine disinfection chemical forms

A

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

64
Q

types of chlorine added to water

A

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)

65
Q

different types of chlorination methods (quantity)

A

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)]

66
Q

testing of chlorine

A

Orthotolidine test
Starch Iodide test
DPD & CHlorotex test

67
Q

De-chlorination

A

[sodium thiosulphate, sodium meta bi sulphate, sodium bi-sulphate, Ammonium hydroxide, Activated carbon]

68
Q

Softning methods

A

Lime soda

Zeolite process

69
Q

air pollution impacts on surrounding environment

A

ozone depletion
acid rain
global warming

70
Q

discharge consideration for self cleansing and maximum design discharge

A

Q.min =1/3 *Q.avg
and
Q.des =3 *Q.avg

71
Q

free-board of septic tank and oxidation pond & Sedimentation tank

A

septic tank = 0.3 m
Sedimentation tank = 0.5m
oxidation pond = 1 m

72
Q

good settling sludge SVI

A

50-150 mg/L

73
Q

settling formula according to temperature

A

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

74
Q

removing fluorides from water

A

(i) Absorption by activated alumina (AA), commonly known as Prashanti Technology.
(ii) Nalgonda technique.
(iii) Ion exchange adsorption method.
(iv) Reverse osmosis process

75
Q

Prashanti Technique

A

 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).

76
Q

Nalgonda Technique

A

 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.

Civil Eng Formulas + Buildings Short (16 decks)

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