RO/NFUFMBR

ChemicalsC A S E S T U DY
RO | UF | MBR |Drinking Water
Delaware, Ohio, USA

Toray's Durable PVDF Hollow-fiber Ultrafiltration Membranes Selectedfor Plant Upgrade at the City of Delaware
OVERVIEW

Figure 1: Specific flux versus temperature

The City of Delaware's Water Treatment Plant ( WTP) started
operating in 1889. The plant's raw water source is a blend ofsurface water from the Olentangy River and groundwater from alimestone aquifer. Under the EPA's Long Term 2 Enhanced SurfaceWater Treatment Rule (LT2), the WTP's feedwater is classified
as Bin 2, which requires a 4-log removal of Cryptosporidium.
As a result, the City would convert its 6.0 MGD lime softening
plant to a 7.2 MGD membrane treatment facility utilizing a 4.5
MGD ultrafiltration (UF) system to comply with LT2. A total ofseven proposals were initially submitted during the UF system'sbidding phase, narrowed down to three showing the best interms of projected capital and operating costs and membrane
performance. The three selections would be piloted for further
evaluation, including UF modules by Toray.
PILOT EVALUATION
The pilot's objective was to determine the full-scale facility's
operating parameters and meet Ohio's EPA drinking waterrequirements. The shortlisted UF modules were piloted for 2,000
hours during the colder months, where the raw water temperature
ranged from 1°C to 18°C, and the feed water turbidities were ashigh as 45 NTU. Figure 1 shows the change in specific flux withincreasing temperature, where Toray demonstrated to have thehighest sustainable flux.
Toray's polyvinylidene fluoride (PVDF) membranes have highresistance to chemicals, allowing for consistent flux rates
after cleaning. As a result, Toray UF modules required only one
clean-in-place (CIP) every two months and used less air during
backwash (3.5 scfm for Toray vs. 9.0 scfm for Brand "A"). The
consultant further noted that "membrane strength and reliability
are the most important criteria and based on manufacturer'stesting data and published studies, Toray also has the strongest
membrane fiber on the market today." (Cook 2013). Also, Bin 2classification of the City's water source requires higher pressure(20 psi) for membrane integrity tests, increasing the likelihood offiber breaks. Thus, membrane fiber integrity played an essential
role in UF module selection for the City's plant upgrade, where
Toray performed well in the pilot and assessments.
To help operators check for membrane integrity during pressure
decay tests (PDT ), Toray provided modules with transparent
filtrate site tubes, as shown in Figure 3. The full-scale plant would
also incorporate clear tubes on the drainage and backwash
overflow lines to provide additional information to the operators.
DECISION MATRIXPost-pilot, the membranes were further evaluated against nonmonetary factors. As illustrated in Table 2, a decision matrix
chart helped determine the best UF system for the City, where
Toray scored the most points and recommended for the WTP's
improvement plans.

Table 1 — Quick Facts

Pre-treatment

200 µm strainers

No. of trains

3

Max. capacity / train

2.25 MGD

Modules per train

48

Configuration

4 rows of 12 modules

Max. net flux (gfd)

60.5

Recovery>95%

Start-up

1Q 2015“Toray has the strongest membrane fiber on themarket today.” URS (now AECOM)
03-US-MB2-OH-202108

1 of 2Figure 2: UF system designed and constructed by H2O Innovation, Inc.
(www.h2oinnovation.com)

Toray's Durable PVDF Hollow-fiber Ultrafiltration Membrane Selectedfor Plant Upgrade at the City of DelawareC A S E S T U DY
RO | UF | MBR |TABLE 2 — CITY OF DELAWARE UF EQUIPMENT SELECTION DECISION MATRIX

868881088Brand "B"

6101010888108Toray897881081010

Overall Pilot
Performance

10Organics Removal

Brand "A"

Volume of ChemicalsUsed102468988108101088Cleaning Interval

734678108868878

10Trans-membrane
Pressure

6

Reduction in
Winter Flux

Customer Service

8Flux Conservatism

Financial Strength

Membrane Strength

Membrane Pore Size

Experience

Skid Size / Flexibility

Operational Costs
5Reliability

Capital Cost
5

Importance Factor (1–10, with 10 being the most important)
528

3Score (1–10, with 10 being the best)

Weighted Score

Total

80

50

1664

212440

48

1636

48

685

56

80

40

2064

241832

48

1640

48706

56

100

40

2080

2124

40

60

2032

48730

Brand "A"5040484856

Brand "B"

30508060

Toray

40455648

This decision matrix was intended to be used as a tool for aiding the City in determining the best system; however, the City was open to making the final decision
based on other criteria as well and was not obligated by this decision matrix.

Table 3 — Design data of UF membrane modules
Manufacturer brand

Toray

Brand "A"

Brand "B"

Pore size, microns

0.01

0.03

0.02

Area (sq.ft.) of each MF module

775

829

550

Peak Flux (gfd) with N-1 skids

68.12

62.3

53.25Net flux with N-1 skids

60.48

56.54

47.85

Net Capacity (N-1) required

4,500,000

4,500,000

4,500,000

Overall Recovery

95.0%

94.9%

95.0%

Normalized Average TMP, psig

12.0

13.0

14.0

Peak Flux (gfd) with N-1 skids

49.95

45.69

33.13

Net flux with N-1 skids

44.35

47.47

29.77

Net Capacity (N-1) required

3,300,000

3,300,000

2,800,000

Overall Recovery

95.0%

94.2%

95.0%

Transmembrane Pressure, psig

12.0

12.0

18.5

Summer Conditions (17°C)

Winter Conditions (3°C)

REFERENCE
Cook. Jeremy. "Design and Permitting of UF/NF System with Surface Water andGroundwater Supplies." 2013 Membrane Technology Conference & Exposition.
San Antonio, TX. February 2013.

Figure 3: filtrate site tubes

TORAY INDUSTRIES, INC.
Head Office: Nihonbashi Mitsui Tower 24th Floor, 1-1, Nihonbashi-Muromachi 2 chome, Chuo-ku,
Tokyo, 103-8666, JAPANwww.water.toray+81 3 3245-4540

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All information presented herein is believed reliable and in accordance with accepted engineering practices. Toray makes nowarranties as to the completeness of this information. Users are responsible for evaluating individual product suitability forspecific applications. Toray assumes no liability whatsoever for any special, indirect or consequential damages arising from thesale, resale or misuse of its products. © 2021 Toray Industries, Inc. Subject to change without notice.
03-US-MB2-OH-202108

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