18 INDUSTRIAL WATERWORLD March/April 2012 www.industrialww.com

The earth has plenty of water but most of it (97.5%) is too salty for human use. The remaining 2.5% is fresh water but only <1% of this

fresh water is available for direct human use. Due to continual population growth, agricultural and industrial developments, and climate change effects, water resourc-es scarcity has become a critical issue in

many parts of world. Water reclamation and reuse in municipalities and industries is becoming an important part of the wa-ter supply portfolio as wastewater is a reli-able and sustainable water source.

One of the major factors in the accel-eration of water reuse is the advent of ad-vanced membrane treatment technolo-gies and their cost reductions in the last 10 to 15 years. Membrane technologies include microfiltration (MF), ultrafiltra-tion (UF), nanofiltration (NF) and re-verse osmosis (RO).

The petro processing facilities, includ-ing refineries and petrochemical plants,

usually consume a large quantity of wa-ter, and the resultant wastewater is well-treated prior to being discharged to the environment. For the last 12-13 years the worldwide petro industry has joined the bandwagon in making use of membrane technologies in water reuse. However, ex-cept for some cases of reusing recycled municipal effluent in California refineries

for cooling and boiler feed, petro facili-ties in the U.S. are slow in adopting mem-brane technologies for reusing industrial wastewater effluent.

However, the recent population growth and long-term drought in Texas has caused some petro facilities to serious-ly consider reuse of industrial effluent to improve the long-term reliability of wa-ter supply.

Background

Using MF or UF in municipal wastewa-ter reuse, especially for RO pretreatment, started to multiply in the late 1990s. To

date, the integrated use of MF or UF with RO has become a standard in municipal advanced recycled water projects, espe-cially for indirect potable water reuse cas-es where the recycled water is re-injected to the groundwater aquifer to augment existing water sources. Good examples include the 270,000 m3/d Groundwater Replenishment System of the Orange

County Water District in South-ern California, and several sig-nificant NEWater plants in Sin-gapore.

Historically, petrochemical plants and refineries have used RO as pretreatment for ion ex-change demineralizers to pro-duce pure water for boiler feed and process uses. Since 1999, more than 10 UF (ZeeWeed®) systems have been installed as pretreatment for RO in petro facilities for boiler feedwater demineralization. RO, in the form of VSEP (Vibratory Shear Enhancing Processing), has also been used in the full-scale for re-moving selenium from stripped sour water to help a large refin-ery meet stringent discharge re-quirements. More recently, sev-eral refineries in California have started using highly treated mu-nicipal effluent as cooling tower

makeup and boiler feed water. The first reported successful full-scale

use of integrated membranes of UF/RO

BY JOSEPH M. WONG

Product Processing IndustriesWater Reuse for Petroleum Oil,

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Design flow rate 7,200 m3/d

Average flow rate 5,280 m3/d

Benzene 2,260 µg/L

Toluene 1,760 µg/L

Ethylbenzene 360 µg/L

Xylene 600 µg/L

MTBE 2,220 µg/L

NH3 330 mg/L

TDS 8,000 mg/L

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for in-plant water reclamation in a pet-rochemical plant is the China American Petrochemical Company (CAPCO) puri-fied terephthatic acid (PTA) plant in Tai-wan. The 9,000 m3/d CAPCO UF/RO sys-tem was commissioned in 2000 and has been successfully operated for more than 10 years.

The second reported large-scale use of UF/RO for a petro facility is for treat-

ing effluent from a biological treat-ment system at the PEMEX refinery in Minatitlan, Vera-cruz, Mexico. The 26,000 m3/d UF/RO system was commis-sioned in 2001 and is part of the zero liq-uid discharge sys-tem at the refinery. PEMEX also has two other refineries that use RO for wa-

ter reclamation but without UF as pre-treatment.

Since 2000, a total of more than 20 UF or UF/RO systems have been installed at petro facilities throughout the world for water reuse. More of the UF systems are used in Membrane Bio-Reactors (MBRs) than in tertiary filtration. The MBRs are either with or without RO. Out of the 20+ UF systems, five are of the pressure

type; the rest are of the submerged type.

With the exception of one small MBR installation (190 m3/d) at Marathon Oil’s barge cleaning and maintenance terminal in Ken-tucky all the signif-icant installations are outside of the United States.

Case Studies

The following presents three rep-resentative case studies of using membrane tech-nologies for water reuse in petro fa-cilities throughout the world. Some significant similar upcoming projects are also listed.

Case Study No. 1

– CAPCO UF/RO Wastewater Recla-mation System

The CAPCO

(wastewater reclamation project near Kaohsiung, Taiwan, is the first reported successful reuse project using integrated membranes of UF/RO in a petro facility. It was commissioned in April 2000. The Kaohsiung CAPCO plant is one of the largest purified terephthalic acid (PTA) producing plants in the world. PTA was one of the most profitable petrochemicals for many years.

The feasibility study for the wastewater reclamation project that started in 1993 and the subsequent two-year pilot-testing program were completed in 1996. Figure 1 shows a block flow diagram of the re-lationship of the wastewater reclamation system with the plant water systems.

The PTA plant uses approximate-ly 48,000 m3/d of fresh water supplied from the water company -- 52 percent as cooling tower makeup and 40 percent as feed to the deionization (DI) system to produce highly purified water for PTA process and boiler feed. Approximately 20,000 m3/d of wastewater, including pro-cess wastewater, cooling tower blowdown, DI system regeneration waste and miscel-laneous wastewater, is generated for treat-ment and disposal to a central industrial effluent management system for com-bined ocean discharge.

Figure 2 shows a block process flow diagram of the recycled water treatment system. The treatment system treats a combination of biological treatment sys-tem effluent and cooling tower blow-down. The two streams had complemen-tary characteristics in minerals content so that the combined stream would have a decent RO recovery.

The treatment train includes a blend feed tank, oxidation by sodium hypochlo-rite (NaOCl) for manganese and copper removal, dual media filtration, granular activated carbon (GAC) for organics re-moval, cartridge filtration, ultrafiltra-tion (UF), ultraviolet (UV) disinfection, reverse osmosis (RO) with acid feed, and degasification to remove carbon dioxide.

The purified water, which has a TDS much lower than that of the municipal-supplied water, is recycled to the PTA plant’s DI system as feedwater. Using the recycled water as DI feedwater can save a major portion of the DI regeneration cost. Together with the reductions in wa-ter purchase cost, wastewater discharge

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www.industrialww.com March/April 2012 INDUSTRIAL WATERWORLD 21

fees and precipitation chemical costs, im-plementing and operating a 15,000 m3/d (influent) reclamation system can yield a simple payback of four to five years.

During construction, however, CAP-CO only constructed a 9,000 m3/d (influ-ent) system, which made the actual pay-back significantly longer. Construction was completed in 1999, but due to start-up problems the system was not commis-sioned until April 2000.

The UF/RO system has achieved an overall 73 to 75 percent recovery, higher when cooling tower blowdown was not used in the influent to the system. With the exception of a 6-month shutdown in 2008 due to business decisions, the sys-tem has been operated continuously for more than 10 years and has saved a huge amount of fresh water for the commu-nity. The average replacement intervals for UF and RO membranes were five and four years, respectively, which were com-parable to the useful lives guaranteed by membrane vendors.

Case Study No. 2 – PEMEX Minatit-lan Refinery UF/RO Water Reuse System

The recycled water project in PEMEX’s refinery located in Minatitlan, Mexico, has been described previously in the lit-erature. This case study is worthy of men-tioning as it is the first refinery to use UF/RO technologies in its recycled water sys-tem which has been operating successful-ly for over 10 years.

The refinery is one of Mexico’s largest refineries (20,325 m3/d or 173,200 bbl/d). As shown in Figure 3, the refinery’s waste-water treatment processes include prima-ry clarifier, dissolved air flotation (DAF), activated sludge aeration basin, second-ary clarifier, membrane filtration (UF), and RO. The RO permeate is reused in the refinery for high quality uses, such as boiler feed. The treatment system is de-signed for a peak flow of 26,000 m3/d. The overall water recycle efficiency is approxi-mately 70 percent based on RO permeate production.

The UF system uses the submerged ZeeWeed® 500b membranes config-ured in seven parallel trains such that one could be taken off-line for cleaning while others remained in production.

22 INDUSTRIAL WATERWORLD March/April 2012 www.industrialww.com

Each train has 11 membrane cassettes with room for four additional cassettes in case of future plant expansion. The UF system provides excellent protection for the RO membranes, and yields turbidi-ty <0.1 NTU, oil and grease <0.2 mg/L, and SDI<3. The UF system recovery is between 90 percent and 95 percent.

Case Study No. 3 – ENI Gela Refinery, Sicily, Italy, MBR/RO System

The ENI Gela Refinery located in Sic-ily has a refining capacity of 11,735 m3/d or 100,000 bbl/d. It processes the heavy crude oil from the ENI fields in offshore Sicily and the extracted oil from the neighboring soil to produce automotive fuels, residential heating oils and petro-chemical feedstocks.

The refinery installed and commis-sioned a 7,200 m3/d MBR/RO system

in March 2007 to treat contaminated groundwater and produce 5,040 m3/d of recycled water to feed the demineraliza-tion system in the refinery for reuse. Ap-proximately 4,800 m3/d of groundwater heavily contaminated with hydrocarbons and arsenic is pretreated by oil/water sep-aration, oxidation, coagulation, high-rate clarification (DensaDeg®), sand filtration, and granular ferric hydroxide adsorption (for arsenic removal).

The pretreated groundwater combines with 2,400 m3/d of contaminated ground-water for feed to the 7,200 m3/d MBR treatment system, which includes pre-de-nitrification, nitrification and post-deni-trification tanks, and four ZeeWeed® 500d

trains. Table 2 shows the water quality characteristics of the MBR influent. The MBR effluent is fed directly to a three-train RO system with a water recovery of 70 percent. The TDS of the groundwater is reduced from 8,000 mg/L to 80 mg/L in the RO permeate; other constituent con-centrations are insignificant. The 2,160 m3/d RO reject stream is treated by a GAC system prior to discharge to the ocean and meets all discharge requirements.

Other Reuse Projects

The case studies described above are only representative installations of the 20+ successful projects since 2000. There are also new projects currently being planned, designed or constructed. Some of the reported projects include a 5,300 m3/d ZeeWeed® MBR system in the

CCRL Refinery in Regina, SK, Canada, to be commissioned in 2012; a 33,000 m3/d UF/RO system in the Shell Pearl Gas-to-Liquid Refinery, Qatar; a 10,800 m3/d Petro MBR system in the Repar Re-finery in Araucaria, Parana, Brazil, to be commissioned in 2012; a 100,900 m3/d ZeedWeed® MBR/EDR/RO system in the Teneco Refinery in Nizhnekamsk in Rus-sia, to be commissioned in 2012; a 15,000 m3/d ZeeWeed® MBR system in the Lu-koil Volgograd Refinery in Russia, to be commissioned in 2013; and finally a 6,000 m3/d MBR/RO systems in the CPC Lin Yuan Petrochemical Plant near Kaohsi-ung, Taiwan, to be commissioned in 2012.

There are also potential membrane

projects that had gone through pilot testing to evaluate the feasibility of wa-ter reuse in refineries and petrochemical plants. Examples include the MF/MBR pilot testing at the Coffeyville Resources Refining & Marketing Refinery in Kan-sas and the MBR/HERO™ pilot testing at a Middle East petrochemical plant. There are probably many more projects in the study or planning stage and many small projects that have been implemented without being reported in the literature. It is impossible to include every project in this review.

Conclusion

Based on the review of the case studies and other successful installations, it ap-pears that using membranes for treating and reusing petro wastewater has gained considerable experience and is general-ly feasible; however, there are some un-successful installations due to problems of fouling by oil and organics, scaling by metals, high-temperature effects on membrane and bonding materials, and very expensive and rapid membrane re-placements. These are usually not report-ed in the literature.

It is recommended that prior to imple-menting full-scale projects, longer-term pilot tests be conducted for each appli-cation unless there is considerable op-erating experience available from other facilities where the water quality char-acteristics and operating conditions are quite similar.

It is expected that water scarcity will continue to be a problem in many parts of the world, especially with climate change effects, and membranes will play greater roles in water reuse in the petro industries in the future. IWW

About the Author:Joseph M. Wong is Chief Engineer

of Brown and Caldwell, with more than 30 years of ex-

perience in industrial and municipal water/wastewater

treatment and reuse. He developed and designed the

world’s first major water reuse project in the petro-

chemical industry using membrane technologies of UF/

RO. He has BS and MS degrees in Chemical Engineer-

ing from University of Washington, and is a registered

professional engineer in California, Florida, and Wash-

ington. He is also a Board Certified Environmental Engi-

neer. He may be contacted at JMWong@brwncald.com

Circle No. 165 on Reader Service Card

Reverse Osmosis System at CAPCO Plant