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M.Sc. Urszula GabrielInstitute of Chemical Engineering and Environmental Protection Processes
WATER NETWORKS OPTIMISATION TO MINIMISE WATER USE AND
WASTEWATER GENERATION
Plan of presentation
1. Introduction2. Evolution of water network structures3. Principles of water minimisation4. Review of design procedures for water networks5. Scheme of elaborated algorithm6. Example of algorithm application7. Conclusions
IntroductionBenefits of water network optimisation:
• lower costs of fresh water intake and wastewater disposal
• lower environmental hazard• solving problems of fresh water shortage
One of the main strategies:• maximizing the reuse of water within the plant and seeking opportunities to use the outlet water from one operation to satisfy the water requirement of another or the same operation
Evolution of water network structures
P1DISPOSAL
P3
P2 T1 T2 T3
1) BASIC „INPUT – OUTPUT”STRUCTURE (CENTRAL FEEDING ANDTREATMENT SUBSYSTEM)
WATER
P1 DISPOSAL
P3
P2T1 T2 T3
2) WATER STREAMS ALLOCATION(DECENTRALISED FEEDING,CENTRAL TREATMENT)
WATER
P1
DISPOSALP3
P2
T1
T3
3) REUSE, REGENERATION + REUSE,REGENERATION + RECYCLING(DECENTRALISED BOTH FEEDING ANDTREATMENT SUBSYSTEMS)
WATERT2
P1SOLID
DISCHARGE
P3
P2T1
T3
4) ZERO WATER DISCHARGE(SYSTEM CLOSURE)
FRESHWATER
MAKEUP T2
Principles of water minimisation
• Contamination present in the water doesn’t have to be totally removed but should be reduced to the level enabling reuse of the stream
• water streams of different contamination level, which are supposed to be reused, shouldn’t be merged before sending them to treatment unit
• water slightly contaminated should be directly reused and the most contaminated water streams should be regenerated
Review of main procedures
Method Advantages Disadvantages
Graphical - visual representation - insight into design
- necessity of graph construction
Algorithmic - easy to perform without charts plotting
- rigorous solution
Genetic algorithm
- global optimum guarantee
- necessity of structure encoding
Mathematical programming
- possibility of including additional constraints
- rigorous solution - no global optimum guarantee
Scheme of algorithm
EXPERT SYSTEM
WATER STREAMS ALLOCATION
4) Selection of treatment option
1) direct
2) including mixing
FEEDING SUBSYSTEM TREATMENT SUBSYSTEM
3) including regeneration
Water streams allocation algorithm
The developed method is based on „nearest neighbour algorithm”: to satisfy a particular water demand, the source streams to be chosen are the nearest available neighbours to the demand in terms of contaminant concentration.
If the solution given above requires mixing with fresh water, the most contaminated stream is chosen for regeneration to replace the raw water.
start
ns , nd arrCs(ns, 3)arrCd(nd, 3)
indCs= ns
indCd= nd
CSCD
Y
indCs=indCs-1
N
YCs= CnFSFD
stop
Y
indCs= indCs-1
indCd= nd
N
FS<>0Y N
Nmix./regen.
results_tab
Expert system
The expert system enables selection of the optimal scheme for the treatment of contaminated water according to its characteristic (type of contaminant), required purification level and efficiency of treatment option.
Treatment schemes
• Sedimentation -> D• Chemical treatment (Al) – sand filter ->
C• Chemical treatment (Al) – trickling filter –
activated carbon – ultrafiltration -> B• Chemical treatment (Al) – trickling filter –
activated carbon – ultrafiltration – RO -> A
A, B, C, D – water quality
Efficiency matrix of treatment modulesMethode SS BOD CH3OH Heavy
MetalsBacteria
Sedimentation
55 30 15 - -
Biological treatment
71 88 62 15 -
chemical treatment
70 40 25 84 -
Treackling filter
68 28 16 - -
Activated carbon
60 63 50 60 95
UF 96 - - - 99RO - 10 32 - 99
Example of algorithm application
- Problem statement
Sources Demands
Number CH3OH(ppm)
SS(ppm)
FS
(Mg/h)Number CH3OH
(ppm)SS
(ppm)FD
(Mg/h)S1 0 100 20 P1 10 0 20S2 20 100 100 P2 10 50 100S3 15 800 40 P3 0 50 40S4 0 800 10 P4 0 400 10S5 0 0 170
170
P1
P2
P3
a) 20
10P4
40
T1100170 90
P1
P2
P3
b)20
50
20
90
P4
40T1
40
5010
40
P1
c)P3
P2
T2
P4
T120
20
- Schemes of obtained water networks
- Simulation results
Water network Fresh water intake
[Mg · h-1]
Spare of water [%]
a) “input – output” 170
-
b) direct streams allocation
90
47
c) allocation + regeneration
40
76
As an optimum treatment method the activated carbon is chosen.
methode SS BOD CH3OH Heavy Metals
Bacteria
Sedimentation
55 30 15 - -
Biological treatment
71 88 62 15 -
chemical treatment
70 40 25 84 -
Treackling filter
68 28 16 - -
Activated carbon
60 63 50 60 95
UF 96 - - - 99RO - 10 32 - 99
Conclusions
Applied algorithm:- Indicates water structure for water streams
allocation (giving 45% lower freshwater intake in above case) and for decentralised water regeneration (giving 75% lower freshwater intake)
- proposes an efficient water treatment method.
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