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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
Conventional Sewage Treatment Process
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
26
Primary Treatment
Screens>Grit Removal>Settling Tank
27
Secondary Treatment
AS Aeration and sedimentation or trickling filter and sedimentation or ponds/lagoons
28
Tertiary/Advanced Treatment
Phosphorous/Nitrogen removal > Filter > Disinfection
29
Sludge Treatment
Anaerobic Digestion, Dewatering, Thickening, Disposal
30
Equalisation Basin Definition and Types
Maintains constant flowrate to reduce the effect of toxic shocks on biological processes In-line and off-line
31
Equalisation Basin Equation
``` ds/dt = Qin-Qout Veq = Sum(Change in S) ```
32
Equalisation Basin Design Procedure
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%
33
Principal objective of preliminary treatment
To protect subsequent treatment processes (prevent blockage and damage to plant. Increase the reliability and efficiency of the treatment)
34
Coarse screens
6 to 150mm
35
Fine screens
2.3-6mm
36
Bar Screen Headloss Calculation
hL=(1/C)((V^2/v^2)/2g) | C = 0.7 clean 0.6 clogged
37
Fine Screen Headloss Calculation - Common Orifice Formula
hL=(1/C*2g)*(Q/A)^2
38
Screenings Handling
Washing, maceration, dewatering, compaction
39
Grit removal
Aearated Grit Chamber - uses spiral current of diffused compressed air
40
Types of settling
Discrete (free) - no interaction between particles as they settle Flocculent Settling - Interaction between particles as they settle Hindered Settling - Compression Settling -
41
Discrete Particle Settling
Terminal velocity calculations and Stokes' Law
42
Designing a sedimentation tank
Select a particle with Uc, design tank that removes all particles with Uc equal to or greater than Uc
43
Sedimentation tank overflow rate
Uc = Q/L*W = Q/A
44
Fraction removed of particles by settling tank
(1-Xc) + integral between 0 and Xc of (Ut/Uc)dX
45
Different types of microorganisms
Aerobic, anaerobic, facultative
46
Biological wastewater treatment options
Attached growth or suspended growth
47
Biomass yield
Yx/s = mass of biomass produced (VSS) / mass of substrate utilised (BOD or COD)
48
Cell Growth
Xt = X0 * e^ut
49
Substrate Limited Growth
Monod Equation
50
Biodegradability
=BOD/COD
51
Kinetics of Biological Growth - well mixed aerobic suspended growth process
Microorganism mass balance Substrate mass balance Microorganism and substrate concentrations
52
Aerobic suspended growth process important factors
Food to mass ratio Sludge age Oxygen transfer rate
53
Activated sludge process flowsheet
WW>Aeration tank>Secondary clarifier> 1. Liquid effluent 2. 1 RAS recycle (maintain F/M ratio) 2. 2 SAS (waste to control sludge age)
54
Activated sludge mean system HRT
HRT = (Vt/Q0) = (V+Vs)/Q0
55
Activated sludge mean reactor HRT
HRT = V/Q0
56
Activated sludge mean cell residence time (sludge age)
Sludge Age = mass organisms in reactor/mass organisms removed from the system = VX/(QwXw)+(QcXc)
57
Activated sludge process equations
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 = Yobs*Q*(S0-S) kg/day Oxygen requirements O2 = Q(S0-S) - 1.42Px
58
Minimum oxygen supply for AS aerobic reactor
1-2mg/L
59
Alternative bioreactors
Sequencing batch reactors | Membrane bio reactor
60
Applications of constructed wetlands
``` Secondary treatment Tertiary treatment Diffuse pollution treatment Landfill leachate Sludge dewatering ```
61
Different types of CWL flow direction
FWS, SSF-h/HF, SSF-v/VF
62
CWL Net pollutant decrease rate
J = K(C -C*)
63
HF CW Design
Kadlec and Knight equations
64
FWS CW Water flow
Manning's equation
65
Main purpose of clarification processes
To reduce turbidity
66
Two basic principles of clarification
gravity settlement | Buoyancy flotation
67
DAF air to solids ratio | pressurised recycle
A/S = (1.3a(fP-1)R)/SQ
68
DAF air to solids ratio all flow pressurised
A/S = (1.3a(fP-1))/S
69
Aggregation
Coagulation followed by flocculation
70
Coagulation
chemical addition to destabilise colloidal particles (charge neutralisation) in water so that floc formation can result
71
Coagulant Types
Inorganic - aluminium sulphate, ferric chloride, calcium/magneisum hydroxides, prepolymerised metal salts Organic - poylmers
72
Flocculation
Particle size increase due to particle collisions
73
Filtration mechanisms
Mechanical straining, sedimentation and adsorption, biological metabolism, electrolytic action
74
Filtration pressure drop
Carmen-kozeny relationship
75
Chemical oxidation
Converts dissolved metals to less soluble oxidation states Removes some hazardous synthetic organic compounds and pesticides Destroy taste, odour and colour-causing compounds
76
Oxidation chemicals
Oxygen, Chlorine, Chlorine Dioxide, Ozone
77
Disinfection definition
Removal or inactivation of pathogenic micro-organisms
78
Disinfection processes
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
Chemical disinfection important parameters
Concentration and reaction time (contact time)
80
Residual disinfectant outcomes
Controls regrowth of bacteria | Provides residual protection in the case of accidental contamination of water distribution system
81
Common residual disinfectants
Chlorine or chloramines
82
Indicators of microbiological/faecal contamination
Coliforms/faecal coliforms
83
Conventional Disinfectants
``` Chlorine or hypochlorous acid Chloramines Chlorine dioxide Ozone Ultraviolet ```
84
Optimum chlorine conditions
``` 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
Chlorine and ammonia react to produce
Chloramines eventually oxidise to N2 or variety of N products
86
Chlorine dioxide
•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
DBPs
Disinfection by-products e.g. THMs
88
DBP control
Control at source Membrane technology Soption (PAC, GAC, synthetic resins-ion exchange) Oxidation/reduction - ozone
89
Disinfection kinetics
Chick-Watson relationship
90
To avoid DBPs
UV disinfection of well clarified secondary/tertiary treatment
91
Ozone flowsheet
Feed gas>ozone generator>ozone contacter>off-gas ozone destructor>discharge to atmosphere
92
BOD K equation
k=kT0*q(T-T0)

January Revision (5 decks)

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