1Challenge the future
Cake layer characteristics in long time ceramic MF filtration for surface water treatment
Mingyang LiMaster defence presentation
2Challenge the future
Contents
• Background • Research objective• Experiments• Results• Conclusions• Recommendations & Futre work
3Challenge the future
Background
• Good & stable water quality• Low energy use (low pressurized)• Easily operated
Ceramic microfiltrationMicrofiltration
4Challenge the future
Background
Compared to conventional polymeric membranes:• Low fouling tendency• Higher permeability• Resistance to pH, heat and chemical conditions• Price becoming cheaper
Ceramic membranes
5Challenge the future
Background
Membrane Fouling
Alternative solutions:• Pretreatment used: Pre-coagulation
Solid wastes• Frequent backwash used Low recovery High maintenance costHigh energy consumption
Ceramic Microfiltration problem
6Challenge the future
Research objective
Increase the filtration time in ceramic microfiltration with in-line coagulation
Highlights:• In-line coagulation, no flocs removed• Long filtration time, TMP increase controlled
Practical Support: • MBR installations• Sludge layer on surface• effective fouling control
7Challenge the future
ExperimentsCake layer importance
• Important cause for TMP increase (constant flux)• 80% resistance percentage in total resistance (PACl)
• Controlled by coagulation mechanisms (pH, dosage)
8Challenge the future
ExperimentsCoagulation mechanisms
Figure 1 Coagulation zones• Three zones divided by pH and dosage• Cake layer formations membrane
performances
9Challenge the future
ExperimentsFlow scheme
Figure 2 Experimental scheme• pH=4, 6 and 8,Dosage=8 and 16mg/L• Flux 60 L/(m2*h)
10Challenge the future
ExperimentsExperimental setup
11Challenge the future
ExperimentsExperimental setup
12Challenge the future
Results
Figure 3 TMP curve with BW and without BW
• Recorded by data logger (Dataq, DI710)• Constant flux 60 (L/m2*h)• Slow TMP increase in cake filtration
TMP
13Challenge the future
Results
Figure 4 TMP curve under coagulant dosage of 8 and 16 mg/L
• In cake filtration, TMP increased differently• pH=4 leads to slow TMP increase (Restabilization
coagulation)• pH=6 leads to rapid TMP increase (Adsorption
coagulation)
TMP
14Challenge the future
Results
• Blank membrane filtered by demi-water Rm
• Recorded data of final TMP Rtot
• Frozen cake layer removed, membrane filtered by demi-water Rm+Rp
• Rc, Rp can be calculated from the above components
Resistance
15Challenge the future
Results
Table 1 Resistance components
• Rc is the largest resistance component• pH=4 leads to the smallest resistance• pH=6 leads to largest resistance
Resistance
R (1012m-
1)
Fe3+=8mg/L Fe3+=16mg/L
Rm Rp Rc Rm Rp Rc
pH=4 0.48
0.48
1.37
0.54
0.42
1.61
pH=6 0.54
0.72
3.7
0.48
0.78
3.15
pH=8 0.54
0.60
2.15
0.54
0.42
1.91
16Challenge the future
ResultsCake layer density & water content
17Challenge the future
Results
Table 2 Cake layer density
Table3 Cake layer water content
• pH=4 leads to smallest density, but largest water content
• pH=6 leads to largest density, but smallest water content
Cake layer density & water content
Density (kg/m3*103)
Fe3+=8mg/L Fe3+=16mg/L
pH=4 1.025 1.018
pH=6 1.070 1.083
pH=8 1.045 1.050
Water content Fe3+=8mg/L Fe3+=16mg/L
pH=4 0.973 0.967
pH=6 0.921 0.928
pH=8 0.937 0.937
18Challenge the future
Results
Cake layer thickness
19Challenge the future
Results
Table 4 Cake layer thickness
• Higher chemical dosage, higher the cake layer• pH=4 leads to largest cake thickness, pH=6 leads to
the smallest cake thickness
Cake layer height
Thickness (mm)
Fe3+=8mg/L Fe3+=16mg/L
pH=4 0.35 0.56
pH=6 0.11 0.24
pH=8 0.15 0.28
20Challenge the future
Results
Kozeny-Carmen equation for cake filtration:
Cake layer thickness
21Challenge the future
Results
Table 5 Cake layer particle size
• pH=4 leads to largest cake particles• pH=6 leads to the smallest cake particles
Cake layer particle size
Particle size (m)
Fe3+=8mg/L Fe3+=16mg/L
pH=4 0.41 0.37
pH=6 0.10 0.13
pH=8 0.16 0.20
22Challenge the future
Results
Empirical equation:
• The membrane and cake layer filtered by demi-water at 20, 30 and 45 L/(m2*h)
Cake layer compressibility
23Challenge the future
Results
Table 6 Cake layer compressibility factor
• pH=4 leads to large compressibility factor, loose structure
• pH=6 leads to the small compressibility factor, dense structure
Cake layer compressibility
Compressibility factor
Fe3+=8mg/L Fe3+=16mg/L
pH=4 0.57 0.70
pH=6 0.33 0.48
pH=8 0.52 0.60
24Challenge the future
Results
Table 7 DOC removal efficiency
• Higher chemical dosing, higher removal efficiency (first stage)
• DOC remove shows no clear tendency with pH
DOC removal
Fe3+=8mg/L Fe3+=16mg/L
S1 S2 Total
S1 S2 Total
pH=4 40%
17%
58%
42%
8% 50%
pH=6 25%
7% 32%
37%
15%
52%
pH=8 4% 15%
20%
10%
31%
41%
25Challenge the future
Conclusions
• Membrane performance can be controlled by various pre-coagulation zones
• It is possible to achieve a long filtration time by applying cake filtration
• Cake layer plays an important role in fouling control process
• pH=4 leads to loose cake structure, shown as slow TMP increase, low cake layer density, high cake layer water content, thickness, particle size and compressibility
• pH=6 leads to dense cake structure, shown as rapid TMP increase, high cake layer density, low cake layer water content, thickness, particle size and compressibility
• DOC remove shows no clear tendency with pH
26Challenge the future
Recommendations & Future work
• pH=4, Dos=8 is good pre-coagulation condition in ceramic microfiltration
• More experiments about the explanations between coagulation mechanisms and cake layer structure
Mechanism cake layer structure phenomenon
• More experiments about low chemical, for instance Dos=4mg/L