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January Revision > Water > Flashcards

Water Flashcards

1
Q

Typical lowland river/reservoir flowsheet

A

Reservoir, pre-ozone, coagulation and flocculation, clairifer, ASG filter, post-ozone, activated carbon, chlorination

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2
Q

Typical upland catchment reservoir flowsheet

A

Reservoir, coagulation and lime rapid mix, flocculation, flotation, rapid gravity filter, manganese contactors, contact tank

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3
Q

Typical groundwater flowsheet

A

Pump, ozone contacter, activated carbon, contact tank, membranes phosphoric acid

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4
Q

Brackish water treatment

A

Screen, cartridge filters or microscreens, membrane filtration, reverse osmosis, pH control, disinfectant, clearwell storage

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5
Q

Water Characteristics

A

Universal solvent

Physical, chemical and biological

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6
Q

Water chemical pollutants

A

Nitrate, arsenic, mercury, fluoride, synthetic organic compounds

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7
Q

Wastewater Treatment in and out values

A 
In:
BOD 150-400mg/L
TSS 150-400mg/L
P 5-15mg/L
N 40-80mg/L
Out:
BOD 20mg/L
TSS 30mg/L
P 1-2mg/L
N 10-15mg/L
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8
Q

Domestic Wastewater Definition

A

Sewage only - no rain runoff

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9
Q

Urban/municipal Wastewater Definition

A

Domestic (and industrial) wastewater plus rain runoff

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10
Q

DWF

A

DWP=LP+I+E

Roughly equivalent to 225L/head per day
Standard wastewater site designed for 3DWF + holding tanks 3DWF

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11
Q

4 components of wastewater flow

A

Domestic, industrial, infiltration/inflow, stormwater

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12
Q

Elementary rational method (estimate flowrate)

A

Qp=0.278CIA

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13
Q

Peak hourly flowrate

A

PHF=Avg flowrate * peaking factor

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14
Q

Sewer Types

A

Separate, combined, partially combined

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15
Q

Charges for trade effluent

A

Mogden formula

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16
Q

BOD Definition

A

Amount of O2 consumed by bacteria stabilising decomposable organic matter under aerobic conditions. Oxidation, synthesis, engogenous respiration.

Sample incubated at 20C for 5 days.

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17
Q

BOD equation (wastewater contains a number of bacteria)

A

BOD5 = (D1-D2)/P

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18
Q

BOD equation (wastewater does not contain adequate number of bacteria)

A

BOD5 = ((D1-D2)-(B1-B2)*f))/P

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19
Q

BOD at time t

A

BOD(t) = UBOD(1-e^-kt)

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20
Q

COD Definition

A

Measure of the oxygen equivalent of the organic material in wastewater that
can be oxidised chemically using a strong chemical oxidant (e.g. dichromate) in an acid solution

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21
Q

BOD COD relationship

A

BOD5 = 0.6COD

BODu = COD

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22
Q

TOC

A

Total organic carbon

Works by oxidising the organic carbon to CO2 and H2O and measuring the CO2 gas

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23
Q

Total Nitrogen

A

Organic N + NH3 + (NH4+) + (NO2-) + (NO3-)

TIN, TAN, TKN

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24
Q

Eutrophication

A

The enrichment of water with nutrients, usually phosphorous and nitrogen, which stimulates
the growth of algal blooms and rooted aquatic vegetation

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25
Q

Conventional Sewage Treatment Process

A

Influent>Overflow>Screens or Commutators>Grit removal>Overflow>Primary Sedimentation>Activated Sludge Aeration or Trickling Filters>Activated Sludge Secondary Sedimentation or Humus Tank>Tertiary Treatment>Effluent

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26
Q

Primary Treatment

A

Screens>Grit Removal>Settling Tank

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27
Q

Secondary Treatment

A

AS Aeration and sedimentation or trickling filter and sedimentation or ponds/lagoons

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28
Q

Tertiary/Advanced Treatment

A

Phosphorous/Nitrogen removal > Filter > Disinfection

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29
Q

Sludge Treatment

A

Anaerobic Digestion, Dewatering, Thickening, Disposal

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30
Q

Equalisation Basin Definition and Types

A

Maintains constant flowrate to reduce the effect of toxic shocks on biological processes

In-line and off-line

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31
Q

Equalisation Basin Equation

A 
ds/dt = Qin-Qout
Veq = Sum(Change in S)
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32
Q

Equalisation Basin Design Procedure

A
  1. Qin flow rates
  2. Daily average Qin
  3. Cumulative Qin curve (based on 1.)
  4. Cumulative avg. Qin curve
  5. Volume required = vertical distance from point of tangency (low point on Qin) and Qin Avg straight line. Max diff between cumulative V and cumulative avg. V
  6. Add contingency of 10-20%
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33
Q

Principal objective of preliminary treatment

A

To protect subsequent treatment processes (prevent blockage and damage to plant. Increase the reliability and efficiency of the treatment)

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34
Q

Coarse screens

A

6 to 150mm

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35
Q

Fine screens

A

2.3-6mm

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36
Q

Bar Screen Headloss Calculation

A

hL=(1/C)((V^2/v^2)/2g)

C = 0.7 clean 0.6 clogged

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37
Q

Fine Screen Headloss Calculation - Common Orifice Formula

A

hL=(1/C2g)(Q/A)^2

38
Q

Screenings Handling

A

Washing, maceration, dewatering, compaction

39
Q

Grit removal

A

Aearated Grit Chamber - uses spiral current of diffused compressed air

40
Q

Types of settling

A

Discrete (free) - no interaction between particles as they settle
Flocculent Settling - Interaction between particles as they settle
Hindered Settling -
Compression Settling -

41
Q

Discrete Particle Settling

A

Terminal velocity calculations and Stokes’ Law

42
Q

Designing a sedimentation tank

A

Select a particle with Uc, design tank that removes all particles with Uc equal to or greater than Uc

43
Q

Sedimentation tank overflow rate

A

Uc = Q/L*W = Q/A

44
Q

Fraction removed of particles by settling tank

A

(1-Xc) + integral between 0 and Xc of (Ut/Uc)dX

45
Q

Different types of microorganisms

A

Aerobic, anaerobic, facultative

46
Q

Biological wastewater treatment options

A

Attached growth or suspended growth

47
Q

Biomass yield

A

Yx/s = mass of biomass produced (VSS) / mass of substrate utilised (BOD or COD)

48
Q

Cell Growth

A

Xt = X0 * e^ut

49
Q

Substrate Limited Growth

A

Monod Equation

50
Q

Biodegradability

A

=BOD/COD

51
Q

Kinetics of Biological Growth - well mixed aerobic suspended growth process

A

Microorganism mass balance
Substrate mass balance
Microorganism and substrate concentrations

52
Q

Aerobic suspended growth process important factors

A

Food to mass ratio
Sludge age
Oxygen transfer rate

53
Q

Activated sludge process flowsheet

A

WW>Aeration tank>Secondary clarifier>

  1. Liquid effluent
  2. 1 RAS recycle (maintain F/M ratio)
  3. 2 SAS (waste to control sludge age)
54
Q

Activated sludge mean system HRT

A

HRT = (Vt/Q0) = (V+Vs)/Q0

55
Q

Activated sludge mean reactor HRT

A

HRT = V/Q0

56
Q

Activated sludge mean cell residence time (sludge age)

A

Sludge Age = mass organisms in reactor/mass organisms removed from the system = VX/(QwXw)+(QcXc)

57
Q

Activated sludge process equations

A

F/M = S0/thetaX
Specific substrate utilisation rate U = ((F/M)E)/100
Process efficiency E = (S0-S)/S0 * 100
Observed yield
3 equations for X (biomass conc in reactor)
Waste sludge production = Px = YobsQ*(S0-S) kg/day
Oxygen requirements O2 = Q(S0-S) - 1.42Px

58
Q

Minimum oxygen supply for AS aerobic reactor

A

1-2mg/L

59
Q

Alternative bioreactors

A

Sequencing batch reactors

Membrane bio reactor

60
Q

Applications of constructed wetlands

A 
Secondary treatment 
Tertiary treatment
Diffuse pollution treatment
Landfill leachate
Sludge dewatering
61
Q

Different types of CWL flow direction

A

FWS, SSF-h/HF, SSF-v/VF

62
Q

CWL Net pollutant decrease rate

A

J = K(C -C*)

63
Q

HF CW Design

A

Kadlec and Knight equations

64
Q

FWS CW Water flow

A

Manning’s equation

65
Q

Main purpose of clarification processes

A

To reduce turbidity

66
Q

Two basic principles of clarification

A

gravity settlement

Buoyancy flotation

67
Q

DAF air to solids ratio

pressurised recycle

A

A/S = (1.3a(fP-1)R)/SQ

68
Q

DAF air to solids ratio all flow pressurised

A

A/S = (1.3a(fP-1))/S

69
Q

Aggregation

A

Coagulation followed by flocculation

70
Q

Coagulation

A

chemical addition to destabilise colloidal particles (charge neutralisation)
in water so that floc formation can result

71
Q

Coagulant Types

A

Inorganic - aluminium sulphate, ferric chloride, calcium/magneisum hydroxides, prepolymerised metal salts
Organic - poylmers

72
Q

Flocculation

A

Particle size increase due to particle collisions

73
Q

Filtration mechanisms

A

Mechanical straining, sedimentation and adsorption, biological metabolism, electrolytic action

74
Q

Filtration pressure drop

A

Carmen-kozeny relationship

75
Q

Chemical oxidation

A

Converts dissolved metals to less soluble oxidation states
Removes some hazardous synthetic organic compounds and pesticides
Destroy taste, odour and colour-causing compounds

76
Q

Oxidation chemicals

A

Oxygen, Chlorine, Chlorine Dioxide, Ozone

77
Q

Disinfection definition

A

Removal or inactivation of pathogenic micro-organisms

78
Q

Disinfection processes

A

Chemical - chemicals used to inactivate or destroy micro-organisms
Physical disinfection - processes remove or deactivate pathogenic mico-organisms (e.g. UV, fine -membrane filtration)

79
Q

Chemical disinfection important parameters

A

Concentration and reaction time (contact time)

80
Q

Residual disinfectant outcomes

A

Controls regrowth of bacteria

Provides residual protection in the case of accidental contamination of water distribution system

81
Q

Common residual disinfectants

A

Chlorine or chloramines

82
Q

Indicators of microbiological/faecal contamination

A

Coliforms/faecal coliforms

83
Q

Conventional Disinfectants

A 
Chlorine or hypochlorous acid
Chloramines
Chlorine dioxide
Ozone
Ultraviolet
84
Q

Optimum chlorine conditions

A 
Low PH (6-7)
20-25C
Long contact time (>30mins)
Dose 0.5-1.0mg/L
Residual concentration at the point of use 0.1-0.2mg/L
85
Q

Chlorine and ammonia react to produce

A

Chloramines eventually oxidise to N2 or variety of N products

86
Q

Chlorine dioxide

A

•A compound of chlorine in the +IV oxidation state;
•Stronger disinfectant than chlorine and chloramines for inactivation of
viruses and Giardia;
•but as it is a stronger oxidant it reacts with more non-target substances;
•It can be used as a primary or secondary disinfectant;
•It is effective over a wide pH range
•retains disinfectant power at higher pH
•expensive;
•possible toxicity of ClO2
- and ClO3
-; controlled by regulation
•maintains a residual
•produced on site from sodium chlorite (NaClO2)

87
Q

DBPs

A

Disinfection by-products e.g. THMs

88
Q

DBP control

A

Control at source
Membrane technology
Soption (PAC, GAC, synthetic resins-ion exchange)
Oxidation/reduction - ozone

89
Q

Disinfection kinetics

A

Chick-Watson relationship

90
Q

To avoid DBPs

A

UV disinfection of well clarified secondary/tertiary treatment

91
Q

Ozone flowsheet

A

Feed gas>ozone generator>ozone contacter>off-gas ozone destructor>discharge to atmosphere

92
Q

BOD K equation

A

k=kT0*q(T-T0)

January Revision (5 decks)

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