RO/NF

UFMBR

ChemicalsC A S E S T U DY
RO | UF | MBR

Wastewater Treatment
California, USA

Cost-effective Sludge Thickening Processor using Toray MBR
at Valley Center
OVERVIEWThe Valley Center Municipal Water District (VCMWD) operates twowastewater treatment facilities in Valley Center, which is located in thenorthern part of San Diego County, California. These two sites are theLower Moosa Canyon and the Woods Valley Ranch Water Reclamation
Facilities (WRF). Both WRF's incorporated an in-house membranethickener (MBT) design and selected Toray's Membrane Bioreactor(MBR) modules for the process. VCMWD's objectives were to conserve
water and meet the Regional Water Quality Control Board's effluent
standards (Title 22), so the reclaimed water can be used for irrigationand other reuse applications. The Toray MBR modules helped the local
utility achieve these goals.
ADVANTAGES
Using MBT has several economic advantages compared to otherconventional methods of sludge thickening (i.e., rotary drums,
belt press or filters). Chart 1 below compares the overall capitaland operating expenditures between different sludge thickeningprocesses. The MBT process has a number of significant
advantages:•Reduced footprint with the use of smaller tanks;•Longer sludge retention time (greater than 100 days) leading
to fewer costs associated with labor, energy consumption,
chemicals for maintenance (cleaning is by air scouring for
MBT and no need for polymers), and dewatering;•Production of higher permeate quality and less reliance on
additional treatment to meet water quality standards.
Chart 1
Cost Comparison of Sludge Thickening Processes

Toray MBR TMR140-050S andTMR140-100S MBR modules are operating atValley Center MWD.
Pictured here is TMR140-100S.

TORAY MBR AT VALLEY CENTER

Unit: K$•

The MBT tank is filled with Waste Activated Sludge (WAS) andwith a pore size of 0.08 microns, Toray MBR is an effective
physical barrier while producing high-quality filtrate.

•The solids concentration in the MBT tank increases from 1%(10,000 mg/L) up to 3% (30,000 mg/L).

•Higher solids concentrations allow for longer retention time,
which improves solids digestion.

•Improved digestion reduces bio-solids to be hauled, whichtranslates into less labor and transportation costs.

•The Lower Moosa Canyon WRF required a centrifuge with a 40 hp
motor to thicken solids. By integrating Toray MBR modules, only
a 1.5 hp motor was required and considerably reducing energy
costs.

200

150

More than 90%
in savings

100500Rotary drum

Belt press

03-US-MB2-VallayCenterCA-202108

Filters

MBT
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Cost-effective Sludge Thickening Processor using Toray MBRat Valley CenterC A S E S T U DY
RO | UF | MBR |Table 1 — Combined savings at Valley Center
Total projected annual savings with membranethickening processor using Toray MBR

RESULTS
Toray MBR modules helped each of VCMWD's wastewater treatment facilities to improve
CAPEX and OPEX in the following areas:
Reduced electrical use of up to 32% or 167,820 kWh per year;•

Reduced equipment run-time (centrifuge, chemical pumps, and aerator) by86%;•Less dependence on chemical usage;•

Reduced bio-solids hauling.

Woods Valley Ranch WRF•

Reduced sludge hauling by 80%;•

Reduced energy and chemical consumption by 53%;•

Reduced equipment run-time eliminating the need for one aeration blower;•

Increased reclaimed water sales (1 acre-foot per year);•Annual savings of $20,000.

$22,000

Chemicals$6,000

Hauling$8,000Total savings$36,000

ADVANTAGES OF TORAY MBR•

Incorporates Toray's PVDF (polyvinylidenefluoride) technology that gives themembrane superior physical strength andchemical resistance;•The distribution of numerous and uniform
pore sizes (0.08 µm) produces high-quality
filtrate and less fouling of the membrane;•Th e f l at- s h e e t co n s t r u c t i o n d o e s n o trequire a backwash system to operatereliably. It incorporates a simple design thatallows for easier maintenance and costsavings compared to hollow-fiber MBRs.

The Lower Moosa Canyon WRF•Energy

Furthermore, as Table 1 shows, the combined annual savings at both facilities for
VCMWD is $36,000.
As a result of the cost-effective operation of the membrane thickening process using
Toray MBR modules, the Woods Valley WRF was awarded the 'Outstanding Energy
Management Award' in 2012 by the Cal-Nevada Section of the American Water Works
Association (AWWA).

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.
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