Engineering

Optimum Configuration of SkyJuice Membranes for Humanitarian Applications

Adam HalmyA/Prof Pierre Le-Clech, Dr. Raquel García-Pacheco

Objectives

Background

Results and Discussion

Conclusion• Dead end configuration modules have the highest permeability values as well as the highest flux rates.• The positive head driving force was the optimum configuration for all the modules. Although all fibres were the same and hence

should have similar permeability values, further investigations should be done to identify the causes of these differences.• Fouling testing should also be undertaken to observe differences in the rate of fouling and rejection rates.

Methodology

1 SkyJuice Foundation ‘Squirt’ Information https://www.skyjuice.org.au/squirt/

Characterise six newly developed SkyJuice modules to identify theoptimum membrane for filtering drinking water in rural areas.

Compare the differences between positive head and suction drivenconfiguration and discuss the benefits and disadvantages of each method.

Fig. 2 An image of the commercial ‘Squirt’ module. Dimensions: 38.5cm x 6cm

ObjectivesCharacterise six newly developed SkyJuice modules to identify the

optimum membrane for filtering drinking water in rural areas.Compare the differences between positive head and suction driven

configuration and discuss the benefits and disadvantages of each method.

Fig. 2 An image of the commercial ‘Squirt’ module. Dimensions: 38.5cm x 6cm

Set up of positive head apparatus with three modules.

200LTank

Module

SplitterPT

1.67

25m

Fig. 3 Diagram of the positive head apparatus set up

Flushing out of preservative solution in modules using RO water at constant head until permeability is stabilised.

Using five different water levels, permeability values were calculated at five heads making sure at each level the values had stabilised.

Steps and were repeated with the suction driven apparatus set up. To alternate the suction pressure, the tubing in red (Fig. 5) were raised.

200LTank

Module

Splitter

PT

1.67

25m

Fig. 5 Diagram of the suction apparatus setup

All preceding steps were repeated with the other three membranes. Additionally, Step was repeated with alternate pipe diameters for suction tubing highlighted in red on Fig. 5.

Fig. 4 Image of the lower portion of the positive

head set up

Conclusion• Dead end configuration modules have the highest permeability values as well as the highest flux rates.• The positive head driving force was the optimum configuration for all the modules. Although all fibres were the same and hence

should have similar permeability values, further investigations should be done to identify the causes of these differences.• Fouling testing should also be undertaken to observe differences in the rate of fouling and rejection rates.

Background

Module Summary

Fig. 6 Image of the suction set up

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700 800 900

Flux

(L/m

2 /h)

Time (min)

Calculating Flux and Permeability

Varying HeadConstant Head

Fig. 8 Experimental Flux for Module A. The red lines indicate times of paused operationwhen bubbles were removed. The black lines indicate periods of relaxation overnight.Observation of the permeability trend showed there was a steady increase as thepressure decreased. The initial data was adjusted using pressure loss models and isshown in Fig. 9, however, it made a difference of <1% as the permeability is intrinsicallylinked to the pressure. Most modules experienced an increase in permeability of around10% over the pressure range tested in this experiment.

Positive Head vs. Suction

Why?

Fig. 9 The permeability of Module A and F for both before and after pressure modelling.The solid line is a linear fit to the post pressure model and the dotted line represents theexpected trend.

Fig. 10 Estimated permeability results forall six modules at a transmembranepressure of 11kPa for positive head andsuction driven conditions.• Positive-head configurations for these

modules performs approximately 25%better than suction at high fluxes and7% at low fluxes as shown in Fig. 10.

• With 12mm tubes, the permeabilityimproved for module A, but was reducedin Module F. This is likely due to theinefficient suction force that often had airentering the tube was observed due toF’s low flux.

2

4

6

8

10

12

6 8 10 12 14 16Perm

eabi

lity

(L/m

2 /h/k

Pa)

Pressure (kPa)

Module A

Module F

0

2

4

6

8

10

12

A B C D E F

Perm

eabi

lity

(L/m

2 /h/k

Pa)

Module

12mm Positive Head6mm Suction12mm Suction

Fig. 1 Current guide to operating the Squirt Modules

Fig. 7 The two configurations of the fibres in themodules are ‘looped’ (a) or ‘dead end’ (b).

Feed Stream FlowModule Shell

FibrePlate

Hollow Fibres (Semi-Permeable)

• Research into drinking water treatment methodsfor rural areas or humanitarian relief is importantto enable everyone to have access to water thatis at appropriate standards for consumption

• Globally, 2.1 billion people do not have accessto safe water (WHO, 2017)

• SkyJuice Foundation1 have developed a low-cost, zero power and portable ultrafiltrationmodule called ‘Squirt’. These need to becharacterised and compared againstcommercial options.

• In previous studies, a positive head filtrationwas utilised and is currently the recommendedprocedure for consumers.

• Investigations into an alternative configurationof suction driven filtration will be explored todetermine if this configuration enhances thedaily capacity or quality of the treated water.

(b)(a)

Module Configuration Area (m2)

Capacity (L/h) Permeability (L/m2/h/kPa)

PH Suc. PH Suc.

A Dead End 0.75 90.4 66.8 10.95 8.09

B Dead End 0.75 79.3 57.5 9.62 6.97

C Looped 0.75 40.6 34.3 4.92 4.15

D Looped 0.75 41.6 37.0 5.05 4.49

E Long Looped 1.4 48.0 35.1 3.11 2.28

F ½ Fibre Dead End 0.37 25.9 24.2 6.37 5.95

Hollow Fibre Ultrafiltration

Tab. 1 A table outlining the configuration and permeability for positive-head (PH) and Suction (Suc.) filtration at a transmembrane pressure of 11kPa.

The membrane’s flux during the wetting is shown in Fig. 8. The initial steady increase isdue to the removal of salt preservatives which eventually stabilises as expected.

Taste of Research Summer Scholarship Program

Research Theme: Resources and Infrastructure for the Future - Water and Wastewater Engineering

• The difference in suction and pressurehead can be explained through thedifference in flow dynamics between thetwo configurations.

• Looped modules are performing less dueto the reduced active membrane areadue to the alternate configuration.

Pre Pressure ModelPost Pressure Model