Waste Management 2014
7 th International Conference on Waste
Management and the Enviroment
May 12 - 14 2014
Ancona, Italy
The use of membrane technology for the formulation of spent anaerobic digester effluents as nutrient source for bacterial growth

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http://www.h2wales.org.uk/
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• Low Carbon Research Institute (LCRI)
Project “Cymru H
2
Wales”
• Swansea University Group is involved in Liquid/Solid Separations from
Complex Effluent Sources
Development of a number of process to recover useable materials in solid or liquid form and chemical intermediates from waste sources .
Swansea University Group
SPEC
C WATER

• Anaerobic digestion (AD), or acidogenic fermentation
,
– Traditional treatment, it can be performed on various solid or liquid substrates, such as silage or manure leading to the production of biogas, methane CO
2 generation.
used in energy
– Acidogenesis represents one of the stages towards methanogenesis. VFA are the main soluble compounds generated
– VFA, ammonia, phosphate could represent a sources of valuable materials for chemicals products provided they can be recovered economically.
Fig.1. Schematic diagram of AD process
Zacharof & Lovitt, Waste and Biomass Valorisation, 2013

• The reduced demand on waste treatment plants as reduced carbon is extracted so reducing costs and energy requirements of oxidation and the release of
CO
2
• The extraction of reduced carbon (as VFA) for reuse and substitution of acetate and other VFA’s derived from petrochemicals reducing reliance on fossil carbon for chemicals of favourable nutrients
• Ammonia recovery would save CO
2 production and enhance the formation of a potentially valuable product if in a concentrated form
• Phosphate is a finite resource is becoming increasingly expensive (800% rise between 2006 to
2008, $50 to $400) with a current value of over
$500 per tonne
• Although its production is carbon neutral it’s been achieved by mining causing environmental and social issues.
Fig.2. Schematic diagram of advantages of the process
Zacharof &Lovitt, Water Science &Technology, Under review, 2014

Organic
Waste
Anaerobic
Digester Separator
Methanogenic
Reactor Biogas
Waste
Biomass
VFA
NH
4
P
CaCO
3
Recycle
Fig.3. Overview of the project
Zacharof & Lovitt, WIT Transactions on Ecology & the
Environment, 2012

Membrane Filtration was the chosen recovery methodology
Suitable technology for pre-treatment and separation
Technology quite well developed but not widely industrially applied for waste processing
Benefits of membrane filtration include:
•Physical separation (water does no change phase)
•No additives (chemicals and/or other materials) are added other than when membranes are manufactured
•There is a wide range of membrane process based on the membrane pore size
•Filtration allows manipulation of the nutrient content, when combined with leaching and acidification using MF or selective separation and concentration using subsequent NF and RO processes
Fig.4.Processing and recovery scheme for VFA and nutrients
Zacharof &Lovitt, Water Science &Technology, Under review, 2014

• Membrane separation is a Pressure driven process
• Microfiltration (MF) 0.2μm pore size
• Membranes used are ceramic made of ultrapure alumina (Pall Membralox) able to separate particles in a range of different sizes varying from 0.2μm(MF)
Fig .5. Ceramic membrane w/t housing Fig.6. Cross flow filtration diagram
Transmembrane pressure
(N m̄²̄)
Osmotic Pressure
(iMRT)
• The large solids are successfully removed through the use of a ceramic microfiltration unit , simultaneously with the recovery of the nutrients of interest
• The flow was configured as cross flow mode
Flux (J, m3/s) J




( R m

P *


R c
) *




Membrane resistance (Rm,m̄ ¹)
Cake resistance(Rc, m̄¹)
Viscocity
(μ, Pa/s )
Zacharof &Lovitt, Desalination, 2014

Permeate
Flux:
134.28
L/m 2 h
Cross Flow
Velocity :
2.05 m/s
Fig.7. Pilot scale sludge processing unit
Fig.8. Pilot scale sludge processing unit diagram
Gerardo et al., Water research, 2013

(a)
(b)
Fig .9. : a)Diafiltration Treatment Strategy b)Dewatering Treatment strategy the measurements were made at a constant sludge volume during the concentration stage, for each dilution step
Zacharof &Lovitt, Desalination, 2014

Parameters Agricultural Sludge
Untreated
Sludge
Treated
Sludge
Total Solids (TS, g/L) 15.13
Total Suspended Solids (TSS, mg/L) 612.50
Total Dissolved Solids (TDS, mg/L) 7965 pH 8.13
Conductivity (mS/cm)
Alkalinity (mg CaCO
3
/L)
Zeta Potential (mV)
9.37
7500
-33.25
Sizing (μm)
Optical Density (580nm 1 )
Concentration
Acetic Acid
Butyric Acid
Ammonia
Phosphate
27.17
0.86
mmols/L
27.48
19.22
2030.30
336.02
11.99
21 %
252.60
59 %
7743
8.43
9.11
5000
-30.06
13.97
48.6 %
0.34
60.5 % mmols/L
24.38
18.91
144.96
10.85
Microfiltered
(0.2μm)Sludge
Retentate
10.40
258.00
7659
8.38
9.01
2500
-29.60
13.49
0.27
mmols/L
18.04
13.21
788.67
55.74
Microfiltered
(0.2μm)Sludge
Permeate
5.15
26.35 %
190.00
50.5 %
7055
8.25
8.3
1875
-24.2
4.93
63.5 %
0.10
70.6 % mmols/L
21.08
15.81
56.31
1.80
Table 1 The effect of pretreatement and microfiltration on the physical characteristics and chemical composition of the anaerobically digested agricultural sludge. The collected samples were diluted 100 times with deionised water and measured in a 1 cm light path 1
Zacharof &Lovitt, Water Science &Technology, 2013

Treatments Time
(min)
Diafiltration Ammonia
-N
L -1 )
Nutrients extracted to the permeate
(mmols
1 fractions
Phosphate Acetic
-P
(mmols L
)
acid
(mmols
L -1 )
Butyric acid
(mmols L -1 )
48.99
1.35
21.08
15.81
Dewatering
Step
25.00
Treatments Time
Dewatering
Dewatering
Step 1
(min)
25.42
Ammonia
-N
(mmols
L -1 )
Nutrients extracted to the permeate fractions
Phosphate Acetic
-P
(mmols L -
1 ) acid
(mmols
L -1 )
Butyric acid
(mmols
L -1 )
53.61
1.31
22.11
16.71
23.10
26.00
1.44
10.54
7.91
Washing step 1
Washing step 2
21.50
12.75
1.10
5.27
3.96
Dewatering
Step 2
26.00
Dewatering
Step 3
27.43
20.01
11.70
0.82
2.64
1.98
Washing step 3
Washing step 4
Depleted
Sludge
-
18.00
3.13
9.00
0.29
1.58
-
1.32
-
0.98
Dewatering
Step 4
29.16
Depleted
Sludge
-
Table 2 The effect of diafiltration and dewatering on the chemical composition of the anaerobically digested agricultural sludge
Zacharof & Lovitt ,Desalination, 2014

Fig.10. Schematic representation of the high pressure stirred cell unit [1] nitrogen cylinder, [2] pressure regulator valve, [3] pressure indicator, [4] stirred cell unit equipped with membrane disc, [5]stirrer, [6] stirring plate, [7]
permeate collection vessel, [8] electronic scale, [9] personal computer.
Zacharof &Lovitt, Water Science & Technology, 2013

Characteristics
Manufacturer
Membranes
General Electric -Osmonics USA Dow FilmTech USA
Model
Distributors
Material
HL DL DK
Sterlitech Corporation http://www.sterlitech.com
Thin film composite piperazine
–based polyamide microporous polysulfone
NF 270
Desal Supplies http://www.desal.co.uk
Thin film composite-
Aromatic polyamide
Nitto Denko Japan
LF10
SOMICON AG WKL http://www.somicon.com
Thin film composite Polyvinyl alcohol-aromatic cross linked polyamides
Applications
Geometry
Effective Membrane area (cm 2 )
Flux rate (L / m 2 h) @689 kPa
Charge (at neutral pH)
Water Softening, Acid Purification, Detergent removal, Heavy metal removal
66.3
pH
Ion rejection (%)
2-10
98
MWCO 150-300
Maximum Operating Temperature ( ° C) 50
52.7
96
37.4
2-11
98
122.0
3-10
97
150-200
45
Flat Sheet
14.60
Negative
11.9
2-10
99.5
<150
40
Table 3 Membranes characteristics provided by the manufacturers
Zacharof &Lovitt, Water Science & Technology, 2013

• Further processing of the effluents was achieved using Nanofiltration, enrichment process of salts additions and pH adjustment were made
Flux (L/m 2 h) Nutrients Acetic acid
(mmols/L)
Butyric acid
(mmols/L)
Ammonia (NH
4
(mmols/L)
-N) Phosphate
(PO
4
-P)
(mmols/L)
Initial
Concentrations
21.08
15.81
48.99
1.35
Treatment : pH 8.5
Membranes
NF270
Ratio
LF10
Ratio
NF270
Ratio
LF10
Ratio
29.56
53.94
52.62
48.27
26.54
1:0.89:2.65:1.23
78.47
28.38
168.37
1.82:0.96: 5.69: 1.35
Treatment :NaCl addition (100mM)
69.74
1.78:2.35
Treatment :NaHCO
3 addition (100mM)
72.23
1.63:2.44
36.60
40.06
15.40
06.00
17.30
11.78
Table 4 Formulation of different composition solutions using nanofiltration
Zacharof et al.,Under preparation, 2014

• Preliminary energy cost studies in un-optimized MF systems have indicated that the energy cost per cubic meter of sludge (11.9 g/l dry solids containing 56.31 mmols/L N,
1.31 mmols/L of P and 22.11 acetic acid and 16.71 butyric acid mmols/L VFA) processed in
£0.91
, 1.02 kWh (using potable water £ 0.75
m 3 )
• The cost of recovery per kg of ammonia, phosphate and VFA was calculated as £1.4
• Diafiltration has produced four different effluents of varying N:P composition i.e. 36.6,
33.8, 27.3 and 22.8, varying metals and VFA content
• Dewatering is producing three different fractions of similar N:P composition of 40.92 , metals and VFA content
• Acidification has been tested, elevating the level of phosphate and metals N:P ratio 8.4
• Manipulation of nutrient content is feasible using this methodologies
Gerardo et al., Water Research, 2013

Growth media Nutrient
(in vitro) media
Minimised (in vitro) media
Treated sludge
(N:P 36.6:1)
Enriched treated sludge
(0.11M glucose)
Micro/sms
L.plantarum
E.coli
μ
(h -1 )
DT (h) μ
(h -1 )
DT (h) μ
(h -1 )
DT (h)
0.18
0.6
3.83
1.15
0.02
0.02
31.1
38.2
-
0.65
-
1.06
μ
(h -1 )
0.45
0.37
DT (h)
1.52
1.81
Table 5 Comparative table of growth of 5 microorganisms on different nutrient sources

• Microorganisms whose end products are susceptible to genetic mutations such as enzymes or proteins might not be suitable for such applications, bacteria or fungi though with metabolic products such as acids or biofuels like ethanol can be used safely.
• Decolourisation was observed when E.coli was grown of the treated effluents resulting to an optical density of 0.02, a reduction of 80%, suggesting that this microorganism might serve as a bioremediation agent.
Fig. 11. Absorbance of four differents nutrient sources inoculated with
E.coli and treated sludge

• This study investigates spent digester fluids and developing a recovery strategy solely devoted on the recovery of VFA, phosphate, ammonia from anaerobic digestates, might not be as easy as from an acidogenic digester where the VFA concentration will be substantially higher, up to 100 mM.
• It has been pointed out that farming waste effluents do represent an environmental hazard as well as a good source virtually in abundance of useful nutrients and metals. Developing a complete recovery strategy for these substances, with a waste treatment system placed in situ could be of great benefit for the industry.
• NF can be used as a method of isolation and recovery of nutrients from complex effluent streams, provided a pretreatment scheme that will remove coarse particles, so the effluents can be easily filtered.
• These findings show potential and could be applied to the biotechnological production of VFA and their recovery.
Zacharof &Lovitt, Water Science & Technology, 2013

• Dr. Stephen Mandale
• Dr. Paul Williams
• Dr. Darren Oatley
• Dr. Sandra Estevez
• Prof. Alan Guwy
M.Zacharof@swansea.ac.uk
R.W.Lovitt@swansea.ac.uk