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Water and Wastewater Engineering > WWE > Flashcards

WWE Flashcards

1
Q

Purpose of Ridge regression

A

Reduce variance

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2
Q

Purpose of Lasso regression

A

Encourage sparsity

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3
Q

Sequence of SCP

A
  1. Define trust region.
  2. Solve approximation.
  3. Check and update trust region.
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4
Q

A11(Q)

A

Head loss relationship

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5
Q

A12

A

Link-junction incidence matrix

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6
Q

A21

A

Junction-link incidence matrix

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7
Q

A10

A

Link-known head node incidence matrix

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8
Q

MPC optimisation formulation

A

Objective function: min. average zonal pressure
Subject to:
- Energy conservation
- Mass conservation
- Minimum regulatory pressure
- Control valve operations

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9
Q

Benefits of pressure management

A
  • Frequency and flow rates of reported leaks reduced
  • Rate of rise of unreported leakage reduces
  • Frequency and cost of economic intervention reduces
  • Background leakage reduces
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10
Q

Leak general equation

A

L = CdA(2gP)^0.5

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11
Q

Leak power equation

A

L = CP^N1

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12
Q

Effect of increasing sludge age

A

More efficient process, but increased Xv (which has a practical limit)

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13
Q

Effect of increasing tank volume

A

Increased hydraulic retention time, but fewer organisms

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14
Q

Nitrification

A
  1. Oxidation of ammonia –> nitrite
  2. Oxidation of nitrite –> nitrate
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15
Q

Denitrification

A

Nitrate + organic matter –> nitrogen gas (under anoxic conditions)

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16
Q

Anammox

A

Ammonia + nitrite –> nitrogen gas
Under anoxic conditions

17
Q

Process of phosphorus removal

A
  • Fatty acids taken by the PAOs and stored as PHA
  • Energy required to store PHA is supplied by breaking down the poly-P into ortho-phosphate
  • Ortho-phosphate released increasing soluble P concentration
  • P uptake to produce poly-P in new cells
  • More P uptake in aerobic reactor than release in anaerobic reactor –> net removal
  • P transfer from liquid to solid
  • P removal via wastage of excess sludge
18
Q

Favorable Conditions Stimulating PolyP

A
  • Anaerobic - aerobic sequence
  • VFAs in the influent
  • No oxygen and nitrate recycling to anaerobic zone
19
Q

P removal configurations

A
  • 3-stage PHOREDOX
  • 5-stage PHOREDOX
  • UCT system
  • Modified UCT system
20
Q

What is the limitation of the PhoRedox systems?

A

Performance is affected if the underflow contains high level of nitrate. Hence, if ammonium/COD ratio is high, there is little flexibility.
N-removal limited by internal recycle ratio.

21
Q

UCT system

A
  • Additional recycle from anoxic to anaerobic.
  • Settling tank underflow recycle to anoxic reactor
22
Q

MUCT system

A
  • Anoxic reactor subdivided into two anoxic reactors
  • First anoxic reactor receives underflow and recycles to anaerobic reactor.
  • Second reactor receives recycling from the aerobic tank.
  • Benefit is no need to control of recycle from aeration tank.
23
Q

Advantage of anammox

A
  • No organics carbon needed
  • No free oxygen needed
  • Less sludge yield (90% less)
24
Q

Globe valve

A

Consists of:
- movable disk-type element
- stationary ring seat in a generally spherical body

25
Q

Diaphragm valve

A
  • flexible diaphragm to control, obstruct, isolate flow
26
Q

Automatic valve control operations

A
  • Pressure from inlet applied to cover chamber –> valve closes.
  • Pressure in cover chamber relieved –> pressure inlet opens valve.
27
Q

Benefits and limitations of MPC

A

Benefits:
- well-suited for multi-feed DMAs
- can adapt to changing critical points
- can incorporate other operational objectives
Limitations:
- needs accurate hydraulic model
- computationally expensive

28
Q

Network Models diagram

A

Steady state simulation ———————Extended period simulation
Low detail
| Strategic planning Pump scheduling
| Design Contingency planning
|
|
|
| Main rehabilitation Water quality
| Minor reinforcements Pressure control
High detail

29
Q

Obtaining flow modulation curve

A
  • Monitor flow and pressure at control valve
  • Monitor pressure at critical point
  • Record elevation at control valve and critical point

head loss between control valve and critical point:

hL = (p + z)outlet - (p + z)critical

define flow modulation curve by setting pmin = pcritical:

poutlet = hL + pmin + (zcritical - zoutlet)

30
Q

Solving hydraulic equations steps

A
  1. Formulate system using hydraulic principles
  2. Estimate initial flows and heads, apply Newton-Raphson and derive linear system corresponding to the NR-update.
  3. Introduce Schur complement to simplify computations.
  4. Solve for h_k+1 first, then get q_k+1.
31
Q

Energy conservation

A

A11(q)q + A12h + A10h0 = 0

32
Q

Mass conservation

A

A21q - d = 0

33
Q

Preserving convexity

A
  • Multiplication by non-negative constant
  • Sum of convex functions
  • Combination with affine function (f(affine function))
  • pointwise maximums
34
Q

Control valve operations constraint

A

A13T q_t >= 0
eta_t >= 0

35
Q

e- donors and acceptors in nitrogen cycle

A

Nitrification: e-donor = ammonia; e-acceptor = O2
Denitrification: e-donor = organic matter; e-acceptor: nitrate/nitrite
Anammox: e-donor = ammonia; e-acceptor: nitrite

36
Q

Nitrogen cycle diagram

A

See drawing

37
Q

Sharon & Annamox

A

Step 1: Partial nitrification (Sharon) convert 50% of ammonium to nitrite
Step 2: annamox
Result: 70-95% N removal

38
Q

P removal diagram

A

See drawing

39
Q

3 stage-PhoRedox diagram

A

see drawing

Water and Wastewater Engineering (1 decks)

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