Jess Brown, Ph.D., P.E.CRG Director

Welcome to the Winter 2013 issue of Research Solutions. This issue highlights how Carollo is

working to bridge the gap between good ideas and engineering solutions in ????:

• Bullet 1• Bullet 2• Bullet 3• Bullet 4

COMMENTARY

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Bridging the Gap

IntroductionThe high salinity or high concentrations of select ions (e.g., sodium, chloride, boron, phosphors, nitrate) in wastewater pose challenges for water reuse and effluent disposal for the southwest region of United States. Advanced treatment technologies, such as reverse osmosis (RO), are often used to improve the quality of the reclaimed water. These technologies are effective and well established, but feasible and sustainable solutions for disposing of the resultant concentrate are limited, especially for inland communities. Current solutions are either unsustainable (i.e., sewer discharge), land-consuming (i.e., large-scale evaporation ponds), energy-intensive (i.e., brine concentrators), or unavailable (i.e., deep well injection for Arizona).

Carollo recently completed a concentrate management demonstration testing study co-funded by the Sub-regional Operation Group (SROG, including Glendale, Mesa,

Phoenix, Scottsdale and Tempe, AZ), the WateReuse Research Foundation, and the U.S. Bureau of Reclamation (USBR). This study demonstrated the feasibility of reducing tertiary reclaimed water RO concentrate volumes and improving overall RO recovery from 85 to 94.3 percent by using electrodialysis reversal (EDR) with organic matter pretreatment (ozone [O3] and biologically-activated filtration [BAF]), and to 98.2 percent with the addition of inorganic pretreatment as well (e.g., ion exchange [IX] or lime softening).

Organic Pretreatment for EDROzone and BAF were tested and optimized for over 5,500 hours. This pretreatment removed about 40 percent of the DOC and 70 percent of the UV absorbance at 254 nanometers (UV254). Ozone alone removed 60 percent of the UV254, but <10 percent of the DOC, indicating that ozone played an important role in transforming the organic matter rather than in mineralizing it (i.e.., converting DOC into carbon dioxide). The process reliably controlled organic fouling on the downstream EDR membrane. No membrane cleaning was conducted for organic fouling during the 1-year testing. An optimized ozone dosage of 75 mg/L (~1.75 mg/L of ozone per mg/L of DOC)

Reshaping Inland Concentrate Management Using Pretreatment

and Electrodialysis ReversalBy Charlie He, P.E., LEED AP (che@carollo.com), Jun Wang, E.I.T., Guy Carpenter, P.E.

WHAT’SNEWof Carollo’s social media juggernaut and stay in touch with what we’re doing!

1. “Like” our Facebook page (www.facebook.com/CarolloEngineers) and follow us on Twitter (@CarolloTweets). As a “friend of Carollo,” you’ll receive updates whenever we post a news story, a helpful piece of information, or even conference and symposium details. Maybe you’ll see a story you can share with a colleague, or maybe you’ll be at a power lunch with General Managers and Engineering Directors and be able to look casually at your phone and brag to the group, “Yeah, Carollo just tweeted their booth number for WEFTEC. I’ll hit ‘em back after I’m done with my curly fries.”

2. Suggest something for the aforementioned Facebook or Twitter feeds. The social media pool is deep and wide, and must be replenished constantly. If you have a story, picture, event, or bit of news that would be of interest to your fellow Facebook friends, email it to pflick@carollo.com.

3. Check out the new Carollo.com. Our completely redesigned website is full of very cool information on Carollo’s technologies, innovative solutions, and national experts. We also have job openings listed by office and discipline, if you are looking for a career change.

Simply put, our colleagues, clients, and even competitors make up the “social” element of social media, and Carollo’s swan dive into the social media waters is just one more demonstration of our commitment to good communication and helping out however we can.

KEY TEAM MEMbERPaul Flick (pflick@carollo.com)

It turns out that engineering school really never covered the finer points of poking, kiking, tubing, tweeting, pinning, and other improbable gerunds. Yet with the growing reliance and popularity of social media tools in our world, we recognized that Carollo’s communication methods need to adapt and change to handle increased information and decreased attention spans.

Therefore, after some years of cautiously dipping our collective toes in the social media pool, Carollo has recently jumped in the deep end with a redesigned web page, a Facebook page, Twitter account, and even a LinkedIn profile to aid our recruiting efforts.

Now, one important thing we’ve learned from watching others splash and play in the social media pool is that “content is crucial.” Let your Facebook page go stale, let old news languish on your website, fail to Tweet responsibility, and your pool of followers will dry up quickly. So, here are three things you can do to take advantage

Carollo Takes the Social Media Plunge

+EDR, for both regular EDR membranes and monovalent EDR membranes). To compare these alternatives on a common basis, it was assumed that water recovered from the concentrate using both secondary RO and EDR would be blended with partial stream reclaimed water and primary RO permeate to meet common irrigation water quality requirements (e.g., 110-125 mg/L sodium or 750 mg/L TDS). In a second blending scenario, a partial stream of the primary RO permeate would also be further treated to potable reuse quality. The overall recovery and the total water costs associated with concentrate management system are presented in Figure 2. As shown in this figure, the demonstrated concentrate management solution (i.e., O3 +BAF+IX+EDR with regular membranes) provided a 41-percent savings in total water costs compared to the brine concentrator options, with only 0.7 percent difference in overall recovery. Compared to secondary RO with organic pretreatment and lime softening, which was the best available proven technology known prior to this study, the demonstrated solution offers 31-percent cost reduction while achieving a slightly higher overall recovery.

SummaryThe SROG concentrate minimization demonstration project delivered new brine management solutions that have reshaped the inland desalination and concentrate management. As illustrated in Figure 1 and by the yellow highlighted trend line in Figure 2, the typical cost:recovery curve, showing the total project costs associated with concentrate management technologies increasing exponentially with the increasing recovery, has now been significantly improved. This approach provides an affordable, fully-engineered, and ready-to-implement solution to inland desalters, with great potential for further improvements through continuing innovation (e.g., additional testing of resin regeneration scheme and the use of monovalent selective membranes).

Carollo Leads WaterRF Project 4459, Development of a Biofiltration Knowledge Base

KEY TEAM MEMbERsChance Lauderdale, Ph.D., P.E. (clauderdale@carollo.com) Jess brown, Ph.D., P.E. Jennifer Nyfennegger, P.E.

Although there are a wide variety of design, operational, and monitoring strategies that can be considered for biofiltration, knowledge of these strategies is disperse and unorganized, and links need to be established between these strategies and treatment performance. A Carollo/Arcadis Team was recently awarded Water Research Foundation (WaterRF) Project 4459, which seeks to begin assimilating our industry’s

biofiltration experience and to develop these links. This project will catalog

and summarize the design, operation, and monitoring strategies and experiences of North American biofiltration facilities. The

Continued on page 8

Reshaping Inland Concentrate ManagementContinued from page 3

Figure 1. Typically, the total project costs associated with concentrate management technologies increase exponentially with the increasing recovery (Sethi, 2005).

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was established by testing a wide range of ozone doses with and without hydrogen peroxide (H2O2) addition. An empty bed contact time (EBCT) of 10 minutes was recommended for the BAF. The testing concluded that continuous addition of H2O2 may not be necessary for DOC removal. However, intermittent use of H2O2 is recommended for improving operational flexibility (i.e., enhancing biological filter hydraulics and bromate formation control).

For post-ozone treatment with granular media filteration using 10-inches of pool filter sand, the proposed organic pretreatment produced an effluent suitable for EDR feed, with turbidity less than 0.2 NTU and 90th percentile 15-minute Silt Density Index of less than 6.

The demonstrated organic pretreatment effectively reduced emerging contaminants, such as endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs). Twenty of 26 monitored EDCs/PPCPs compounds were removed to below their detection limits. Most of the remaining compounds were also reduced over 90 percent. The raw RO concentrate contained 400 ng/L N-nitrosodimethylamine (NDMA) and had the potential to form over 700 ng/L. The ozone process did not form NDMA, but neither did it significantly remove it. BAF was the major contributor to NDMA reduction. However, ozone showed better removal for NDMA formation potential than the BAF process. In summary, ozone removed 5 to 15 percent NDMA and 50 to 60 percent of formation potential. BAF removed 70-90 percent NDMA and 20-30 percent of formation potential. The formed NDMA in the BAF effluent was less than 10 ng/L.

Bromate formation during ozonation is a concern. Ozone and BAF cannot remove bromate effectively. As a large ion, it was expected that bromate could be rejected by 80-90 percent using RO or EDR and further diluted to concentrations lower than 10 µg/L (i.e., the MCL) by blending with reclaimed water or primary RO permeate.

Inorganic Pretreatment for EDRA conventional IX process using NaCl alone for resin regeneration was tested and evaluated as a baseline. An IX product water with a calcium concentration of less than 50 mg/L and a barium concentration

of less than 0.07 mg/L could support a 90-percent EDR recovery. As a proven and mature technology, a conventional IX system could be designed to reliably meet the EDR feed quality requirement by the manufacturer. Demonstration testing was recommended but not required.

Due to the high divalent ion concentration in the raw RO concentrate, the conventional IX system broke through frequently and required a significant amount of pure sodium chloride (NaCl) for resin regeneration at approximately once every 70 bed volumes (BV). This is equivalent to a NaCl usage of 25 kg/1,000-gallon concentrate treated. An innovative concept was proven at bench-scale to use IX to pretreat the EDR feed and use the EDR brine to regenerate the resins. Demonstration-scale testing was conducted and showed that <50 mg/L calcium, <0.07 mg/L barium, and 90-percent EDR recovery can be achieved using EDR concentrate to regenerate IX resins. NaCl regeneration was still needed every 152 BV. The equivalent NaCl usage was reduced to 14.8 kg /1,000-gallon concentrate treated, saving about 41 percent in salt costs.

Concentrate Volume Reduction by EDR or ROThis study demonstrated that EDR reliably recovered 62 percent of the RO concentrate with organic pretreatment alone, and 89 percent with both organic and inorganic pretreatment. This means that the proposed

concentrate treatment schemes could improve the overall recovery from 85 to 94.3 and 98.2 percent, respectively.

Based on modeling, secondary RO with similar pretreatment can achieve 44-percent recovery with organic pretreatment, and 83 percent with both organic and inorganic pretreatment. These are equivalent to 91.6 and 97.6 percent total recovery, respectively.

Because EDR membranes are more tolerant of organic fouling than secondary RO, the required ozone dose and BAF EBCT for the EDR pretreatment would be lower than those for the RO pretreatment, resulting in savings in both capital and O&M costs. Because silica scaling is critical for RO but not an issue for EDR, the appropriate inorganic pretreatment for RO would be lime softening, which uses a significant amount of chemicals and generates a large quantity of residuals. In comparison, an IX+EDR combination would be much more automated and less messy.

Blending and Cost AnalysisThe study report presented a cost analysis for eight concentrate management alternatives for two blending scenarios. These alternatives include two baseline options (evaporation pond and brine concentrators), two RO options (O3+BAF +RO and O3+BAF+lime+RO), four EDR options (O3+BAF+EDR and O3+BAF+IX

PROJECTUPDATEs

Secondary treatment is achieved at the City of Woodland’s Water Pollution Control Facility (WPCF) with oxidation ditches. Carollo is currently designing modifications to convert the oxidation ditches to a Modified Ludzack-Ettinger (MLE) biological nitrogen removal process to meet future nitrate limits. The conversion requires retrofitting the ditches with mechanical mixers to ensure that there is sufficient mixing in the anoxic zone and the first aerobic zone (Zone 1), which can also be operated as an anoxic zone. Because the tank geometry is unconventional, having sloped sides and 180° bends, computation fluid dynamic (CFD) modeling was used to investigate the performance and system mixing achieved with two types of mechanical mixers, horizontal propeller mixers and hyperboloid mixers.

The mixer geometry was modeled as close as possible from shop drawings and discussions with the manufacturers. The rotating mixer components were modeled at the speeds provided by the manufacturers. Initial efforts focused on optimizing horizontal mixer orientation to keep solids in suspension in the Anoxic Zone, and Zone 1 when air mixing was off. The modeling incorporated a custom user-defined function (UDF) to simulate suspended solids settling and transport as

a scalar within the tank. These UDF also simulate the impact of density changes resulting from the solids concentration profile on fluid momentum. Simulations were initiated with an assumed uniform concentration of 4,000 mg/L mixed liquor suspended solids (MLSS) throughout the tank. Settling velocities were calculated using the revised Daigger equation, and were based on an assumed sludge volume index (SVI) value of 150 mL/g.

Results were compared using several methods, including visually comparing graphics of velocity and solids concentrations. The figures below were developed by calculating the percentage of area that fell within certain velocities and by calculating the coefficient of variation (CoV) of the solids in the zones. Figure 1 shows an example of the velocity distribution in the anoxic zone and the solids concentration profile in Zone 1 with horizontal mixers installed in the ditch. Figure 2 shows similar results with

CFD Modeling of Mechanical Mixers in Activated Sludge Allows Selection of More Efficient Mixers

hyperboloid mixers installed in the ditch. The solids CoV noted in the figures shows that both types of mixers keep all solids in suspension and relatively uniform. In both cases, the CoV is slightly higher in the anoxic zone, with the CoV of the hyperboloid configuration being slightly greater than that of the horizontal mixer configuration. This result is likely due to the 180° bend and influent pipe, which is expected to have a greater influence on the hyperboloid mixers. The hyperboloid mixers are designed to create a vertical roll pattern sweeping the floor. The influent pipe interferes with this, dampening their mixing impact. Table 1 summarizes the velocity range in the zones for both types of mixer. In the Anoxic Zone both types of mixers produce similar velocity ranges, in Zone 1 the horizontal mixer produce higher overall velocities.

Both mixer types provided adequate mixing of solids. As a final comparison,

the horsepower (hp) required to run the mixers were determined based on the modeled torque on the mixers. The horizontal mixers required a total of 34.5 hp, whereas the hyperboloid mixers required 26.3 hp. These results have been useful in selecting mixing equipment that will most effectively achieve the mixing requirements of the project.

ReferenceDaigger, G.T. (1995) Development of Refined Clarifier Operating Diagrams Using Updated Settling Characteristics Database, Water Environment Research, 67, 95.

KEY TEAM MEMbERsEd Wicklein, P.E.(ewicklein@carollo.com) Andre Gharagozian, P.E. Rob Hunt, P.E. Katy Rogers, P.E.

Velocity Range (ft/s)

Anoxic Zone Zone 1

Horizontal Mixer

HyperboloidHorizontal

MixerHyperboloid

0 to 0.5 64.8 63.9 16.6 59.2

0.5 to 1 24.5 22.8 46.2 27.2

> 1 10.7 13.3 37.3 13.6

Figure 1. Horizontal propeller mixers keep velocity high in take, keeping solids in suspension.

Figure 2. Hyperboloid mixers create higher velocity near floor creating a rolling pattern that keeps solids in suspension.

Table 1. Summary of the Velocity Range in the Zones for Both Types of Mixer

Figure 2. Overall recoveries and total water costs of the concentrate management solutions evaluated.

Note:Ion exchange alternatives conservatively include costs for constructing and operating tworegeneration systems (brine and NaCl) and chemical costs for using NaCl for all regeneration.No credits of the potential savings by using EDR concentrate were taken.

$500

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RecoveryCost�A�F ($)

�imilar to Figure 1

Continued on page 7

Jess Brown, Ph.D., P.E.CRG Director

Welcome to the Winter 2013 issue of Research Solutions. This issue highlights how Carollo is

working to bridge the gap between good ideas and engineering solutions in ????:

• Bullet 1• Bullet 2• Bullet 3• Bullet 4

COMMENTARY

2

rese

arch

solu

tion

s

7

rese

arch

solu

tion

s

Bridging the Gap

IntroductionThe high salinity or high concentrations of select ions (e.g., sodium, chloride, boron, phosphors, nitrate) in wastewater pose challenges for water reuse and effluent disposal for the southwest region of United States. Advanced treatment technologies, such as reverse osmosis (RO), are often used to improve the quality of the reclaimed water. These technologies are effective and well established, but feasible and sustainable solutions for disposing of the resultant concentrate are limited, especially for inland communities. Current solutions are either unsustainable (i.e., sewer discharge), land-consuming (i.e., large-scale evaporation ponds), energy-intensive (i.e., brine concentrators), or unavailable (i.e., deep well injection for Arizona).

Carollo recently completed a concentrate management demonstration testing study co-funded by the Sub-regional Operation Group (SROG, including Glendale, Mesa,

Phoenix, Scottsdale and Tempe, AZ), the WateReuse Research Foundation, and the U.S. Bureau of Reclamation (USBR). This study demonstrated the feasibility of reducing tertiary reclaimed water RO concentrate volumes and improving overall RO recovery from 85 to 94.3 percent by using electrodialysis reversal (EDR) with organic matter pretreatment (ozone [O3] and biologically-activated filtration [BAF]), and to 98.2 percent with the addition of inorganic pretreatment as well (e.g., ion exchange [IX] or lime softening).

Organic Pretreatment for EDROzone and BAF were tested and optimized for over 5,500 hours. This pretreatment removed about 40 percent of the DOC and 70 percent of the UV absorbance at 254 nanometers (UV254). Ozone alone removed 60 percent of the UV254, but <10 percent of the DOC, indicating that ozone played an important role in transforming the organic matter rather than in mineralizing it (i.e.., converting DOC into carbon dioxide). The process reliably controlled organic fouling on the downstream EDR membrane. No membrane cleaning was conducted for organic fouling during the 1-year testing. An optimized ozone dosage of 75 mg/L (~1.75 mg/L of ozone per mg/L of DOC)

Reshaping Inland Concentrate Management Using Pretreatment

and Electrodialysis ReversalBy Charlie He, P.E., LEED AP (che@carollo.com), Jun Wang, E.I.T., Guy Carpenter, P.E.

WHAT’SNEWof Carollo’s social media juggernaut and stay in touch with what we’re doing!

1. “Like” our Facebook page (www.facebook.com/CarolloEngineers) and follow us on Twitter (@CarolloTweets). As a “friend of Carollo,” you’ll receive updates whenever we post a news story, a helpful piece of information, or even conference and symposium details. Maybe you’ll see a story you can share with a colleague, or maybe you’ll be at a power lunch with General Managers and Engineering Directors and be able to look casually at your phone and brag to the group, “Yeah, Carollo just tweeted their booth number for WEFTEC. I’ll hit ‘em back after I’m done with my curly fries.”

2. Suggest something for the aforementioned Facebook or Twitter feeds. The social media pool is deep and wide, and must be replenished constantly. If you have a story, picture, event, or bit of news that would be of interest to your fellow Facebook friends, email it to pflick@carollo.com.

3. Check out the new Carollo.com. Our completely redesigned website is full of very cool information on Carollo’s technologies, innovative solutions, and national experts. We also have job openings listed by office and discipline, if you are looking for a career change.

Simply put, our colleagues, clients, and even competitors make up the “social” element of social media, and Carollo’s swan dive into the social media waters is just one more demonstration of our commitment to good communication and helping out however we can.

KEY TEAM MEMbERPaul Flick (pflick@carollo.com)

It turns out that engineering school really never covered the finer points of poking, kiking, tubing, tweeting, pinning, and other improbable gerunds. Yet with the growing reliance and popularity of social media tools in our world, we recognized that Carollo’s communication methods need to adapt and change to handle increased information and decreased attention spans.

Therefore, after some years of cautiously dipping our collective toes in the social media pool, Carollo has recently jumped in the deep end with a redesigned web page, a Facebook page, Twitter account, and even a LinkedIn profile to aid our recruiting efforts.

Now, one important thing we’ve learned from watching others splash and play in the social media pool is that “content is crucial.” Let your Facebook page go stale, let old news languish on your website, fail to Tweet responsibility, and your pool of followers will dry up quickly. So, here are three things you can do to take advantage

Carollo Takes the Social Media Plunge

+EDR, for both regular EDR membranes and monovalent EDR membranes). To compare these alternatives on a common basis, it was assumed that water recovered from the concentrate using both secondary RO and EDR would be blended with partial stream reclaimed water and primary RO permeate to meet common irrigation water quality requirements (e.g., 110-125 mg/L sodium or 750 mg/L TDS). In a second blending scenario, a partial stream of the primary RO permeate would also be further treated to potable reuse quality. The overall recovery and the total water costs associated with concentrate management system are presented in Figure 2. As shown in this figure, the demonstrated concentrate management solution (i.e., O3 +BAF+IX+EDR with regular membranes) provided a 41-percent savings in total water costs compared to the brine concentrator options, with only 0.7 percent difference in overall recovery. Compared to secondary RO with organic pretreatment and lime softening, which was the best available proven technology known prior to this study, the demonstrated solution offers 31-percent cost reduction while achieving a slightly higher overall recovery.

SummaryThe SROG concentrate minimization demonstration project delivered new brine management solutions that have reshaped the inland desalination and concentrate management. As illustrated in Figure 1 and by the yellow highlighted trend line in Figure 2, the typical cost:recovery curve, showing the total project costs associated with concentrate management technologies increasing exponentially with the increasing recovery, has now been significantly improved. This approach provides an affordable, fully-engineered, and ready-to-implement solution to inland desalters, with great potential for further improvements through continuing innovation (e.g., additional testing of resin regeneration scheme and the use of monovalent selective membranes).

Carollo Leads WaterRF Project 4459, Development of a Biofiltration Knowledge Base

KEY TEAM MEMbERsChance Lauderdale, Ph.D., P.E. (clauderdale@carollo.com) Jess brown, Ph.D., P.E. Jennifer Nyfennegger, P.E.

Although there are a wide variety of design, operational, and monitoring strategies that can be considered for biofiltration, knowledge of these strategies is disperse and unorganized, and links need to be established between these strategies and treatment performance. A Carollo/Arcadis Team was recently awarded Water Research Foundation (WaterRF) Project 4459, which seeks to begin assimilating our industry’s

biofiltration experience and to develop these links. This project will catalog

and summarize the design, operation, and monitoring strategies and experiences of North American biofiltration facilities. The

Continued on page 8

Reshaping Inland Concentrate ManagementContinued from page 3

Figure 1. Typically, the total project costs associated with concentrate management technologies increase exponentially with the increasing recovery (Sethi, 2005).

1

10

1,000

0 10 20 10030

Recovery (%)

7040 50 60 9080

100

Improved Recovery (for Brackish Water RO)

2 3

1. Current Seawater RO (SWRO)2. Current Brackish RO (BWRO)3. “BWRO with Improved Recovery”4. Current BWRO with near-Zero Liquid Discharge (ZLD)5. Current BRWO with ZLD

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