WWE

Question 1

Purpose of Ridge regression

Answer 1

Reduce variance

Question 2

Purpose of Lasso regression

Answer 2

Encourage sparsity

Question 3

Sequence of SCP

Answer 3

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

Question 4

A11(Q)

Answer 4

Head loss relationship

Question 5

A12

Answer 5

Link-junction incidence matrix

Question 6

A21

Answer 6

Junction-link incidence matrix

Question 7

A10

Answer 7

Link-known head node incidence matrix

Question 8

MPC optimisation formulation

Answer 8

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

Question 9

Benefits of pressure management

Answer 9

• 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

Question 10

Leak general equation

Answer 10

L = CdA(2gP)^0.5

Question 11

Leak power equation

Answer 11

L = CP^N1

Question 12

Effect of increasing sludge age

Answer 12

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

Question 13

Effect of increasing tank volume

Answer 13

Increased hydraulic retention time, but fewer organisms

Question 14

Nitrification

Answer 14

1. Oxidation of ammonia –> nitrite
2. Oxidation of nitrite –> nitrate

Question 15

Denitrification

Answer 15

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

Question 16

Anammox

Answer 16

Ammonia + nitrite –> nitrogen gas
Under anoxic conditions

Question 17

Process of phosphorus removal

Answer 17

• 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

Question 18

Favorable Conditions Stimulating PolyP

Answer 18

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

Question 19

P removal configurations

Answer 19

• 3-stage PHOREDOX
• 5-stage PHOREDOX
• UCT system
• Modified UCT system

Question 20

What is the limitation of the PhoRedox systems?

Answer 20

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.

Question 21

UCT system

Answer 21

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

Question 22

MUCT system

Answer 22

• 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.

Question 23

Advantage of anammox

Answer 23

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

Question 24

Globe valve

Answer 24

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

Question 25

Diaphragm valve

Answer 25

- flexible diaphragm to control, obstruct, isolate flow

Question 26

Automatic valve control operations

Answer 26

- Pressure from inlet applied to cover chamber --> valve closes. - Pressure in cover chamber relieved --> pressure inlet opens valve.

Question 27

Benefits and limitations of MPC

Answer 27

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

Question 28

Network Models diagram

Answer 28

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

Question 29

Obtaining flow modulation curve

Answer 29

- 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)

Question 30

Solving hydraulic equations steps

Answer 30

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.

Question 31

Energy conservation

Answer 31

A11(q)q + A12h + A10h0 = 0

Question 32

Mass conservation

Answer 32

A21q - d = 0

Question 33

Preserving convexity

Answer 33

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

Question 34

Control valve operations constraint

Answer 34

A13T q_t >= 0 eta_t >= 0

Question 35

e- donors and acceptors in nitrogen cycle

Answer 35

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

Question 36

Nitrogen cycle diagram

Answer 36

See drawing

Question 37

Sharon & Annamox

Answer 37

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

Question 38

P removal diagram

Answer 38

See drawing

Question 39

3 stage-PhoRedox diagram

Answer 39

see drawing