WWE Flashcards
Purpose of Ridge regression
Reduce variance
Purpose of Lasso regression
Encourage sparsity
Sequence of SCP
- Define trust region.
- Solve approximation.
- Check and update trust region.
A11(Q)
Head loss relationship
A12
Link-junction incidence matrix
A21
Junction-link incidence matrix
A10
Link-known head node incidence matrix
MPC optimisation formulation
Objective function: min. average zonal pressure
Subject to:
- Energy conservation
- Mass conservation
- Minimum regulatory pressure
- Control valve operations
Benefits of pressure management
- 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
Leak general equation
L = CdA(2gP)^0.5
Leak power equation
L = CP^N1
Effect of increasing sludge age
More efficient process, but increased Xv (which has a practical limit)
Effect of increasing tank volume
Increased hydraulic retention time, but fewer organisms
Nitrification
- Oxidation of ammonia –> nitrite
- Oxidation of nitrite –> nitrate
Denitrification
Nitrate + organic matter –> nitrogen gas (under anoxic conditions)
Anammox
Ammonia + nitrite –> nitrogen gas
Under anoxic conditions
Process of phosphorus removal
- 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
Favorable Conditions Stimulating PolyP
- Anaerobic - aerobic sequence
- VFAs in the influent
- No oxygen and nitrate recycling to anaerobic zone
P removal configurations
- 3-stage PHOREDOX
- 5-stage PHOREDOX
- UCT system
- Modified UCT system
What is the limitation of the PhoRedox systems?
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.
UCT system
- Additional recycle from anoxic to anaerobic.
- Settling tank underflow recycle to anoxic reactor
MUCT system
- 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.
Advantage of anammox
- No organics carbon needed
- No free oxygen needed
- Less sludge yield (90% less)
Globe valve
Consists of:
- movable disk-type element
- stationary ring seat in a generally spherical body
Diaphragm valve
- flexible diaphragm to control, obstruct, isolate flow
Automatic valve control operations
- Pressure from inlet applied to cover chamber –> valve closes.
- Pressure in cover chamber relieved –> pressure inlet opens valve.
Benefits and limitations of MPC
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
Network Models diagram
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
Obtaining flow modulation curve
- 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)
Solving hydraulic equations steps
- Formulate system using hydraulic principles
- Estimate initial flows and heads, apply Newton-Raphson and derive linear system corresponding to the NR-update.
- Introduce Schur complement to simplify computations.
- Solve for h_k+1 first, then get q_k+1.
Energy conservation
A11(q)q + A12h + A10h0 = 0
Mass conservation
A21q - d = 0
Preserving convexity
- Multiplication by non-negative constant
- Sum of convex functions
- Combination with affine function (f(affine function))
- pointwise maximums
Control valve operations constraint
A13T q_t >= 0
eta_t >= 0
e- donors and acceptors in nitrogen cycle
Nitrification: e-donor = ammonia; e-acceptor = O2
Denitrification: e-donor = organic matter; e-acceptor: nitrate/nitrite
Anammox: e-donor = ammonia; e-acceptor: nitrite
Nitrogen cycle diagram
See drawing
Sharon & Annamox
Step 1: Partial nitrification (Sharon) convert 50% of ammonium to nitrite
Step 2: annamox
Result: 70-95% N removal
P removal diagram
See drawing
3 stage-PhoRedox diagram
see drawing
