This document summarizes pilot scale trials of spiral wound membranes conducted by Cranfield University and Scottish Water. Membrane performance was assessed in terms of permeate water quality and removal of natural organic matter (NOM). Six membrane configurations were tested and measured for parameters like flux, permeability, trihalomethane (THM) formation potential, and NOM fraction removal. The tests found that all membranes except one outperformed the current membrane configuration in reducing THM formation. One membrane in particular achieved the highest flux and permeability while maintaining lower THM levels than the other membranes. Further testing is recommended using conditioned membranes and more realistic temperature conditions.

1. Pilot Scale Spiral Wound Membrane Trials
at Gorthleck
Mr. Dan Golea1,2 , Mr. Stewart Sutherland2 Dr. Peter Jarvis1 Prof. Simon Judd1, and
Mr. Graeme Moore2
1 Cranfield University
2 Scottish Water
For further information please contact Dan Golea.
Email: dan.golea@stream-idc.net or d.m.golea@cranfield.ac.uk or dan.golea@SCOTTISHWATER.co.uk
Postal address: B52a Vincent Building, 1st floor, Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL.
www.stream-idc.net
Conclusions
6 mm
Basket
strainer
Sand filter
10 µm
Cartridge
Sewer or
Sewage
management
High energyOver-reliance on
membranes
High replacement
rate
Potential water quality issues
due to DBP formation
No available sewerage at
remote sites
Unmanned DISTRIBUTION
Service
reservoir
Disinfection
ClO
Membrane fouling issues
Chloroform
Bromoform
Dibromochloromethane
Bromodichloromethane
Aims/Objectives
Assess the performance of current and four commercially available spiral
wound membranes against a benchmark in terms of permeate water THM
formation propensity and total NOM removal, as well as that of the NOM
fractions.
Membrane rig set up at Gorthelck
Normalised flux and permeability at 20°C for the 6 membrane configurations
All candidate membranes ,
apart from membrane C
outperformed the current
configuration in terms of total
THM formation, though only
membrane C sustained a
higher flux.
STREAM IDC Challenge Week: Sheffield University 28th June – 3rd July 2015
Results
Since retentate and permeate were recirculated on a close loop, the feed water temperature increased to
>34 °C due to friction. Therefore , membranes’ flux and permeability were normalised for 20°C using a
viscosity correction formula . The normalised flux and permeability performance revealed membrane C as
the top permeate producer with a mean flux of 85.7 LMH and a permeability of 14.34 LMH/bar .
Introduction
Scottish Water uses membrane technology to purify raw waters, and
specifically remove natural organic matter (NOM). The NOM produces
trihalomethanes (THMs) in the treated water following chlorination; there
strict regulatory limits on THM levels in drinking water. The NOM also fouls
the membrane, reducing the flux of water through it and so increasing
running costs.
NOM composition varies dramatically geographically, seasonally and
diurnally. The screening process has identified 5 membrane configurations
(one of which was a benchmark widely covered by literature) that may
outperform the current one. A test rig was set up to compare the
membranes’ performance mainly for THM precursor rejection. The 5
candidate membranes together with a surrogate of the current configuration
were tested against a worst case scenario of high TOC and temperatures
(>30°C). However, a 10% or less permeate recovery was achieved since
only one element was used per module. Two separate 9 days trials were
conducted due to time restrictions and since the rig only featured 4 modules.
Drain
Permeate
overflow
Variable speed
pump 36 m3/hr, 15
KW Permeate
discharge
Flow meter (L/hr)
Feed
Bleed
Y
Y
Y
Pressure gauge (bar)
Blend tank
1.5 m3
Y
On-off valve
Leaver valve
Throttle valve
Stage I A Stage I B
Sample Yield Stdev DOC % Yield tTHM Yield Stdev DOC % Yield tTHM
µg/mg mgC/L % pass tTHM/OC mg/L µg/mg mgC/L % pass tTHM/OC mg/L
Raw 127.49 18.9 4.15 12.7 0.529 134.4 19.949 7.39 13.44 0.9932
Filtrate 108.78 23 4.02 10.9 0.437 127.7625 14.217 7.2 12.78 0.9199
Blend 112.39 18.7 16.91 11.2 1.9 152.8625 25.895 17.58 15.29 2.6873
Benchmark 25.25 15.4 1.05 6% 2.5 0.027 24.075 2.9168 0.66 4% 2.41 0.0159
Current 70.163 21.4 3.92 23% 7.0 0.275 82.0375 15.295 2.38 14% 8.20 0.1952
Membrane A 57.375 11.8 2.27 13% 5.7 0.13
Membrane B 39.325 9.88 1.59 9% 3.9 0.063
Membrane C 73.025 32.293 2.76 16% 7.30 0.2015
Membrane D 52.425 4.2203 1.33 8% 5.24 0.0697
1 The reproducibility for %yield in the permeate samples is good for the two duplicated membranes
2 The reproducibility for %OC passage is poor for the two duplicated membranes
3 The %yield in the permeate across all membranes varies from 2.4 to 8.2%, roughly according to selectivity
4 Only NF membranes provide low tTHM levels, associated with low OC passage
All trialled membranes, apart from Membrane C, outperformed the current configuration in terms of DOC
passage, THM:DOC ratio (reactivity or yield) and total THM formation.
0
2
4
6
8
10
12
DOC(mg/L)
HPI TPI HPO
NOM fractionation by adsorption
revealed a relatively high
hydrophobic component in the
permeate from the current and
membrane C configurations
(54.53% and 51.06 % respectively).
Benchmark and membrane A
presented a high hydrophilic
fraction (51.46% and 52.10%,
respectively). However, overall
recovery was low (48.89% to 70.
53%) due to the low DOC in the
permeate; hence a higher sample
volume (+3L should be used in the
future).
0
5
10
15
20
25
0
10
20
30
40
50
60
70
80
90
100
Benchmark Current Membrane A Membrane B Membrane C Membrane D
Normalisedpermeabilityat20°C
(LMH/bar)
Normalisedfluxat20°C(LMH)
Membrane product
Mean normalised flux
Mean normalised permeability
Relationship between DOC passage and THM formation propensity.
NOM characterisation by fractionation by adsorption of raw, filtered, blend
and permeate samples.
Further testing required using
non-virgin, fully conditioned
membrane materials, i.e. having
gone through a number of
cleaning cycles, to provide more
representative data.
Whilst the high temperatures
arising helped identify best
performing membrane in the
worst case, regarding permeate
water quality, further tests are
required at more realistic
temperatures
Example of WTW based on
membrane technology
THMs