Membrane Bioreactor and i - MICRODYN-NADIR...TECHNICAL PAPER FORM NO.: TP-001 REVISION DATE: 02/05/2020 Membrane Bioreactor and i CHANGING THE CALCULUS OF WASTEWATER TREATMENT & REUSE

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FORM NO.: TP-001 REVISION DATE: 02/05/2020

Membrane Bioreactor and i

CHANGING THE CALCULUS OF WASTEWATER TREATMENT & REUSE

Dennis Livingston, P.E. 1 and Mike Snodgrass 2 Originally published by American Membrane Technology Association (AMTA) for the 2015 Membrane Technology Conference &

Exposition 1 Ovivo USA, LLC, 2404 Rutland Drive, Austin, TX 78758 2 TriSep Corporation, 93 South La Patera Lane, CA 93117 Abstract In 2010, a pilot test was conducted to demonstrate the use of a spiral wound polymeric ultrafiltration (UF) membrane system (i -bed media filtration, for the treatment of raw wastewater during storm events. The test was successful (AMTA, -month full-scale demonstration test, regulators approved a version of the storm-flow management process (SFMP), as side-stream treatment, for reuse applications in the state of California. In fact, it is the first physical-chemical treatment process using membranes approved for reuse in the state. In 2013, two satellite plants, each capable of treating roughly 120,000 gpd were built using the technology and now, in 2014, a 2.2 MGD plant is under design in the Pacific Northwest. In each case the main process is a membrane bioreactor (MBR) where the peaking factor is more than three times the average dry weather flow capacity. Historically, such high peaking factors would have made an MBR solution cost prohibitive, but for these three projects, this novel UF application resulted in a favorable total cost of ownership comparison. The SFMP is a stand-alone side stream system designed to treat fine-screened plant influent during periods of high flow where treated effluent is intended, and required, to comply with all permit limits without blending. In the absence of a biological oxidation process, adsorption media is employed for additional treatment depending on effluent quality requirements. For removal of soluble biochemical oxygen demand (BOD), activated carbon is used while zeolite is used for ammonia (nitrogen) removal. Both media types are naturally occurring, readily available and well understood. In fact, the use of zeolite for the removal of reduced nitrogen was explained in the Nitrogen Control Report issued by the EPA circa 1970. None of the technologies included in the SFMP are novel in and of themselves and it is only their combination and applied use that is novel to the wastewater treatment industry, and therefore underwent extensive validation. In 2011, a collaborative study was conducted using a demonstration system at the Santa Lucia Preserve near Carmel, CA to validate the process and gain Title 22 approval for the SFMP. Over an 8 month period, raw wastewater was directly filtered by ultrafiltration followed by activated carbon. Membrane effluent quality test results were extensively reviewed and accepted by the California Department of Public Health. SFMP system performance data was reviewed by the Regional Water Board for permitting purposes. Data from the test also verified the ability of the SFMP to be cycled on and off, as needed, on an hourly, daily or weekly schedule, without impacting performance. Three case studies utilizing the SFMP are reviewed in this paper. Two plants in California recently implemented full scale SFMP systems while a third plant in the Northwest is entering the construction phase. The site of the demonstration test (Santa Lucia),

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elected to implement a MBR + SFMP system to upgrade its existing trickling filter treatment plant. A second MBR + SFMP was installed at a resort near Lake Berryessa in Northern California. Both of these plants are designed to treat roughly 120,000 gallons per day with the storm flows intermittently expected to reach about 70,000 GPD. The MBR + SFMP treatment approach reduced total plant costs by as much as 20% for the two California plants. In 2014 the headworks of an existing activated sludge plant,

e plant to a high-rate 0.48 MGD MBR equipped with a 1.7 MGD SFMP. SFMP Development Over the past ten (10) years, the implementation of membrane bioreactor technology has become widely accepted in both the municipal and industrial sector. While MBRs are often considered Best Available Technology (BAT), there are still several concerns over energy consumption and total installed plant costs, slowing more widespread acceptance and growth. Since plant costs and realized efficiencies are greatly impacted by system size, it is imperative to provide an optimized design to minimize life cycle costs to plant owners.

Biological treatment systems are limited in their ability to address storm water flows due to poor food to microorganism (F/M) ratios. Combined with lower temperatures, biological activity is drastically lower in storm flows, leading to capacity restrictions and/or poor operating efficiencies. Using a combination of screening, coagulation, ultrafiltration (UF), and media filtration, the SFMP process is designed as a physical-chemical bypass treatment system for biological treatment processes (e.g., membrane bioreactors) to produce on-demand tertiary filtered recycled water during transient periods of peak flow. This membrane-based treatment process produces an effluent with low turbidity and organic content, to complement biological processes during intermittent periods of rapidly changing hydraulic loading and water quality conditions associated with storm-related flows.

MBR plants that experience high transient peak flows begin to lose their technical and economic advantage as it becomes impractical for a single plant to treat such highly varying flow rates. Plants designed to handle high peak flows are often equipped with oversized biological systems, excess process equipment, and insufficient equipment turndown efficiencies. An MBR becomes much more efficient when designed for a narrow operating window in terms of flow variation. A two-stream approach can solve many of the design, operational, and economical challenges associated with MBR plants that experience high peak flows.

The proposed two-stream approach employs a conventional MBR along with a side-stream physical-chemical treatment system using ultrafiltration (UF) for solids removal, activated carbon for BOD removal, and zeolite for ammonia removal. The combined unit operations produce high quality effluent that exceeds typical regulatory permit requirements. A process flow diagram (PFD) of the MBR peak flow system is shown in Figure 1.

Figure 1. Storm Flow Management Process (SFMP).

Direct low-pressure filtration of raw wastewater is generally viewed as a non-viable application due to the high propensity of fouling by organic material. Raw wastewater has extremely high levels of soluble organic matter and fat, oils, and greases (FOG) that aggressively foul polymeric membranes. Small organic compounds can easily penetrate the membrane pores, narrowing the pore diameter and creating much greater hydraulic resistance compared to cake layer formation. This type of membrane fouling

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results in rapid flux and permeability decline and requires chemical cleaning to restore membrane transport properties. Unlike MBR plants, direct filtration is directly exposed to the hourly variations in feed water chemistry, making stable operation an even greater challenge

A pilot study was conducted at the Brushy Creek Wastewater Treatment Plant (WWTP) in Round Rock, TX for the purpose of determining treatment feasibility as well as establishing design guidelines for the SFMP. During typical storm related peak flow events, raw wastewater is diluted at ratios greater than two to one. However, for the purpose of the pilot study, the UF membranes were operated directly on full strength raw wastewater (i.e. dry weather conditions) to ensure the system could operate under worst case scenarios. Typical wastewater characteristics seen during the pilot study are shown in Table 1.

TABLE 1. PILOT STUDY INFLUENT CHARACTERISTICS

Parameter Value Units

Turbidity 242 NTU

TSS 328 mg/L

COD 409 mg/L

BOD 190 mg/L

FOG 50 100 mg/L

pH 6.5 7.0 -

Since the use of zeolite and activated carbon to remove ammonia and BOD, respectively, are well established and accepted technologies, the pilot study heavily focused on UF membrane performance. Since peak flow events are short term it was not necessary to target continuous operation. As most peak flow events typically last less than 24 hours, the goal of the pilot study was to show stable operation over that time period while providing a significant safety factor of one week.

It was immediately obvious that fouling was very rapid and severe as a 50% decrease in membrane permeability was observed shortly after start-up. The rapid decline in permeability was also independent of operating flux, suggesting the main fouling mechanism was due to organic matter and/or FOG. It was decided that coagulant should be added to the feed to help bind up organic matter, making it easier to clean the membranes using mechanical methods (i.e. backwashing). Alum was added directly to the raw wastewater (UF feed) downstream of the 3 mm screen at a target rate of 175 mg/l and was based on the BOD levels reported by the WWTP.

With the coagulation process optimized, UF performance stabilized as the resulting floc helped bind up organic material. Initially, it was assumed that air scouring would have been a critical component of membrane operation due to the large amount of particulate matter and debris present in raw sewage. However, the coagulation process was highly effective at binding up organic material, negating the need for membrane air scouring.

A continuous operating flux rate of 25-30 gfd was observed in the pilot study. A list of operating parameters for the UF pilot are shown in Table 2 while a plot of operating performance is shown in Figure 3. At the end of the pilot study, the membrane showed no signs of solids (i.e. hair, paper) accumulation, showing that a 3 mm screen was adequate pre-treatment to the UF. Based on the pilot results, a high degree of confidence was obtained and the next phase of the process/product development was initiated.

TABLE 2. UF DESIGN PARAMETERS.

Parameter Value Units

Operating Flux 25 30 gfd

TMP 2 5 psi

Backwash Hz 10 min

Backwash Duration 1 min

Recovery 75 90 %

Air Scour None -

Alum Addition 175 mg/L

pH Adjustment 7.0 7.5 -

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Title 22 Testing Regulatory approval for the SFMP, just like any other wastewater treatment process, was critical and required additional testing and operational data. Regulatory focus was on California Title 22, one of the most widely accepted standards in wastewater treatment today. A 71,000 gpd demonstration system was installed at the Santa Lucia Communities Service District (SLCD) in Carmel, CA. SLCD was in need of an upgrade to its existing plant due to several notices of violations due to peak flow events, so there was tremendous interest in an MBR + SFMP solution.

The State of California Water Recycling Criteria (Title 22) specifies water quality objectives that must be attained in order for recycled water to be used in various reuse applications. To produce tertiary disinfected recycled water, the Water Recycling Criteria require that the water be:

• Well oxidized: organic matter has been stabilized, is nonputrescible, and contains dissolved oxygen; • Filtered: either through granular media or a membrane; and • Disinfected prior to reuse.

nanofiltration, or a reverse osmosis membrane so that the turbidity of the filtered wastewater does not exceed any of the following:

• 0.2 NTU more than 5 percent of the time within a 24-hour period; and •

The SFMP, which is a physical-chemical process, faced greater regulatory scrutiny due to its lack of biological oxidation processes. If successful, the SFMP would be the first of its kind granted Title 22 approval.

The SFMP demonstration facility drew water from the SLCSD WWTP primary equalization basin, which contains primary influent that has been pretreated with a 0.03 inch perforated screen. The water is passed through a fine screen followed by alum addition and ultrafiltration (UF). The waste stream from the UF membrane unit was fed to the SLCSD digester, while the permeate from the demonstration system is fed to the SLCSD full-scale wastewater treatment facility, upstream of the trickling filters. The process flow diagram of the fully automated UF demonstration system with remote access is shown in Figure 2. Detailed specifications of the SFMP demonstration plant are shown in Table 3.

Figure 2. Flow Diagram SFMP UF Demonstration System.

TABLE 3. SPECIFICATIONS FOR THE SFMP UF MEMBRANE SYSTEM

Parameter Specification

Testing Skid Dimensions (L x W x H) 8 x 10 x 7.7 ft

Membrane iSep 500-PVDF

Active Membrane Area 2,950 ft2 (274.1 m2)

Membrane Configuration 10 spiral-wound modules

Flow Direction Outside-In

Required Feed Pressure 1 10 psi vacuum

Pretreatment

Feed Flow Rate 65 70 gpm (dry weather); 55 gpm (wet weather)

Chemicals NaOCl, acid, detergent (optional)

Target Flux Rate 25 gfd

Nominal Pore Size 0.03 µm

Primary influent taken from SLCSD WWTP was used for all experiments related to the demonstration testing. While the actual SFMP process is designed for intermittent operation exclusively for the treatment of wet-weather peak-flows the demonstration

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unit was operated more frequently and treated mostly dry weather flows (i.e., full-strength wastewater) and limited wet weather flows (i.e., wastewater diluted by storm water). Testing with undiluted (full-strength) wastewater provided a conservative evaluation of the SFMP system. Influent water quality data at SLPCSD during the demonstration testing are presented in Table 4.

TABLE 4. FEED WATER QUALITY FOR DEMONSTRATION STUDY.

Water Quality Parameter Units Primary Influent Water Quality (from SLCSD WWTP)

Average* Minimum Maximum

Biological Oxygen Demand (BOD) mg/L 118 68 212

Chemical Oxygen Demand (COD) mg/L 598 377 1216

Total Organic Carbon (TOC) † mg/L 23 17 34

Dissolved Organic Carbon (DOC) mg/L 9.9 7.3 16

Total Suspended Solids (TSS) mg/L 576 20 1720

Ammonia-N mg/L 9.5 4.6 16

Orthophosphate-P mg/L 0.1 ND 0.35

Alkalinity-CaCO3 mg/L 208 128 274

Total Coliform Bacteria MPN/100 mL 4.6 x 106 4.7 x 105 5.5 x 107

E. Coli Bacteria MPN/100 mL 6.7 x 105 1.0 x 105 1.4 x 107

Male Specific Bacteriophage PFU/mL 1.7 x 101 <1 x 100 1.3 x 102

Somatic Bacteriophage PFU/mL 1.1 x 101 2 x 100 1.2 x 102

* Geometric means are presented for pathogen indicator organisms (bacterial and bacteriophage); all other averages are arithmetic means. † TOC data for influent water is not considered reliable due to the large organic material inherent to raw wastewater. In general, SLCSD receives approximately 12,000 gallons of domestic wastewater per day (gpd) in dry weather conditions; during storm events, however the wet weather flows can be in excess of 30,000 gpd. Historical flow data from the SLPCSD WWTP are plotted versus the total rainfall from the previous 7-days (Figure 4). The SFMP system would typically be operated when the total plant flow is approximately twice the average non-storm flow. Although the WWTP exceeded twice the average flow with little or no rainfall, the largest WWTP flows occurred when the 7-day total rainfall exceeded 3 inches.

Figure 4. Daily wastewater flows at the SLCD vs. the total rainfall (2002-2004).

Even though the SFMP system is intended for use in treating wet weather flows, i.e., when the wastewater is diluted with infiltrated and intercepted storm water, the demonstration testing was conducted regardless of storms and plant flows. The winter in central California was particularly dry in 2012 and the highest 7-day rainfall during the SFMP testing period was 3 inches. As shown in Figure 5, there were a total of only five rainfall events that had more than trace amount of rain during the testing period, and the

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rainfall exceeded 1 inch only twice (March 18th through 19th and April 1st). The cumulative rainfall experienced over the 5 months of testing was approximately 6 inches. Due to the limited rainfall, all data can be considered non-storm flows.

Figure 5. 24-hour total rainfall totals during the SFMP testing.

The minimum specific flux during each run dropped slowly over the testing period, and was restored after the first citric clean (Figure 6). A second citric flux was performed on July 24, 2012, which signifies the start of the additional turbidity data collection period.

Figure 6. The minimum specific flux during each run over the demonstration period. Citric cleans are indicated by the vertical lines.

Aluminum sulfate (alum) was added to the raw feed water for the entire duration of the testing. The purpose of the alum addition was to coagulate colloidal material that would otherwise rapidly foul the membrane. The alum dose was empirically selected by the plant operator and, on average, was 147 mg/L. Lower alum doses are expected when the system is operated to treat storm flows due to lower organic concentrations.

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As expected, effluent water quality from the SFMP was excellent throughout the demonstration test. Effluent from the SFMP was compared with the quality of the existing system at SLCD. Summaries of water quality for both treatment systems are shown in Tables 5 and 6. Removal efficiencies of both systems in shown in Table 7.

TABLE 5. SUMMARY OF WATER QUALITY DATA FROM THE SFMP TEST AND EXISTING SLPCSD GRANULAR MEDIA FILTER (GMF) EFFLUENT (VALUES SHOWN ARE ARITHMETIC MEAN).

Parameter Units Primary Influent UF Permeate GAC Effluent GMF Effluent a

BOD mg/L 118 7.9 3.9 21

COD mg/L 598 123 111 n/a b

TSS mg/L 576 <2 <2 10

TOC mg/L n/a 8.99 0.76 n/a

UV Transmittance % n/a n/a 99.2% 74.9%

a Includes reduction through secondary biological treatment (trickling filter) b n/a = parameter not measured

TABLE 6. WATER QUALITY DATA FROM THE SFMP TEST (UF AND GAC EFFLUENT) AND THE SLPCSD GRANULAR MEDIA FILTER (GMF) EFFLUENT (VALUES SHOWN ARE GEOMETRIC MEAN).

Parameter Units Primary Influent UF Permeate GAC Effluent GMF Effluent a

Total Coliform Bacteria MPN/100 mL 106.7 <1 1 105.4

E. Coli MPN/100 mL 105.8 <1 <1 104.5

Native Phage (male-specific) PFU/mL 17 <0.002 n/a b n/a

Native Phage (somatic) PFU/mL 11 <0.001 n/a n/a

a Includes reduction through secondary biological treatment (trickling filter) b n/a = parameter not measured

TABLE 7. REMOVAL EFFICIENCIES OF SFMP AND SLCD GMF.

Parameter UF Only UF + GAC GMF Removal a

BOD 93% 97% 82%

COD 79% 81% n/a b

TSS >99% >99% 98%

Total Coliforms >6.7-log 6.5-log ~1.3-log

E. Coli >5.8-log >5.8-log ~1.3-log

Native Phage (male-specific) >4.0-log n/a n/a

Native Phage (somatic) >3.9-log n/a n/a

a Includes reduction through secondary biological treatment (trickling filter) b n/a = parameter not measured Case Study 1: Santa Lucia, CA (3Q Peak Flow) Background (Problem) The Santa Lucia Preserve (SLP) is a private residential community located in Carmel, CA. In March of 2009, the Santa Lucia Community Services District received a Notice of Violation from the California Regional Water Quality Control Board due to excessive I&I in the wastewater collection system. This violation notice and fluctuating water quality issues led SLP to begin the process of evaluating what type of system would be best to use to upgrade their plant. The 50,000 GPD Rancho San Carlos Wastewater Reclamation Plant (WRP), located on the premises, struggled for years to meet discharge requirements. Some of the factors that would upset the failing trickling filter (attached growth) facility included:

• water-conserving fixtures (increased organic load concentration) • fluctuating occupancy rates (varying load) • inflow and infiltration (I&I)

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During the winter months, I&I was particularly problematic as it diluted wastewater strength and washed out media. However, reduced flowrates during dry summer months had the reverse effect, increasing organic loading to levels higher than the WRP was designed to handle. Solution (Project Details) MBR technology was an obvious choice to replace the existing three-stage trickling filter and sand filtration system because the existing tankage could be reused and the effluent would meet Title 22 requirements and allow for irrigation of golf courses. However, the initial options for treating peak flows were cost prohibitive. At the SLP, Annual Dry Weather Flow (ADWF) rates average 31,000 GPD with Peak Week Flow (PWF) rates reaching 102,000 GPD. Designing an MBR to handle PWF events would essentially double, or even triple, the size of the biological MBR process. Only after an MBR with an SFMP system was proposed did the overall economics become feasible. Taking this approach, the MBR was designed to treat 50,000 GPD and the SFMP 71,000 GPD. Since the SFMP concept was in the preliminary development stage, SLP chose to host a demonstration study to validate the treatment concept. Based on the successful validation test results, SLP elected to proceed with a full scale MBR + SFMP installation. The combined MBR + SFMP approach (shown in Figures 7 and 8) reduced the total constructed cost of the upgrade by approximately 20% and allows for full reuse of all treated effluent (sent to ponds and then used to irrigate golf courses).

Figure 7. The SLP MBR + SFMP

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Figure 8. The SFMP Membranes at SLP

Case Study 2: Lake Berryessa, CA (3Q Peak Flow) Background (Problem)

Located in northeastern Napa County, the Napa Berryessa Resort Improvement District (NBRID) includes 11 recreational areas and 630 residential lots. The NBRID Sewer System serves roughly 920 people and, before recent renovations, included:

• 5.2 miles of VCP collection lines • 1.2 miles of force mains • 4 lift stations • Sewage Treatment Plant (STP) 63,000 GPD • Treated Effluent Storage 1.6 MG • Sprayfield disposal on hillside above lake

For several years, NBRID had experienced problems managing severe sewer inflow and infiltration (I/I), which led to numerous problems. Flow limits were often exceeded, wastewater runoff from the spray fields into the lake were frequent, and discharges of partially treated wastewater into the lake were common during storm events. Finally, in 2012, a plan was put into place to address both water and wastewater infrastructure problems, including high I&I that historically exceeded the capacity of old extended aeration WWTF. Solution (Project Details)

In August of 2012, NBRID contracted with a delivery team as part of a Design Build Finance Operate Maintain (DBFOM) project based on a guaranteed maximum price of $10.9M to improve the:

1. Ponds and I & I 2. Water Treatment Plant 3. Wastewater Treatment Plant

The itemized budget for the Wastewater System Improvement portion of the project, with financing from a combination of private and public funding sources, was as follows:

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TABLE 8. LAKE BERRYESSA WWTP PROJECT BUDGET

Project Component Cost

Storage Pond Expansion $3,431,886

Wastewater Plant Improvements $2,996,111

Collection System Upgrades $212,959

age

plant capable of treating 27,300 GPD with a peak capacity of 134,000 GPD. However, the design was deemed inadequate to handle known I&I problems, meet future permit requirements, and accommodate expansion. The delivery team then settled on an alternate MBR + SFMP design with a rated maximum month flow (MMF) capacity of 60,000 GPD and a combined peak capacity of 191,000 GPD. The approach simplified operations, reduced the overall footprint of the facility and minimized total cost of ownership. The final equipment price was $1,034,864 or about 33% of the total installed cost. The footprint of the system, shown Figure 9, is roughly 20 ft x 80 ft. The MBR + SFMP System was commissioned in October, 2013 and has been operating successfully ever since. Some technical highlights of the SFMP include:

TABLE 9. NBRID SFMP SPECIFICATIONS

Design Capacity 71,000 GPD

Effluent BOD <5 mg/L

Effluent TSS <5 mg/L

Effluent Turbidity <0.2 NTU

Qty. Elements 10

Element Membrane Area 295 ft2

Net Flux 24.1 gfd

Reject Flow 16.4 gpm

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Figure 9. The NBRID MBR + SFMP System

Case Study 3: Pacific Northwest (4Q Peak Flow) An activated sludge plant in the Pacific Northwest, originally built in the 1970s, is being upgraded to a 0.48 MGD MBR system combined with a 1.7 MGD SFMP. Before selecting MBR, other conventional options were considered: 1.) SBR, 2.) Expansion of the CAS, and 3.) Oxidation ditch. A preliminary, high level analysis quickly eliminated four of the possibilities including an expansion of the existing activated sludge process as well as an oxidation ditch. However, before a decision could be made, a fairly detailed comparative cost analysis between a continuous flow SBR and MBR was made. Initially, when evaluating a traditional MBR, the SBR option appeared more cost effective. However, after reevaluating MBR with the SFMP option a net present worth analysis showed the SBR to be the more expensive option, as shown in Table 10. The cost savings of an MBR + SFMP coupled with a smaller footprint and higher effluent quality resulted in the selection of the MBR + SFMP solution. Construction of the MBR and SFMP system is expected to begin in 2015.

TABLE 10. SBR VS. MBR + SFMP COST COMPARISON

Treatment Option Construction Cost ($) Project Cost ($) Annual O&M Cost ($) Net Present Value ($)

SBR 7,507,800 9,836,800 351,330 14,278,793

MBR + SFMP 7,650,400 10,023,400 246,330 13,122,200

Conclusion Performance and cost data from a Title 22 validation study and from three full-scale projects suggest that a solution is now

technology. Utilizing a SFMP to trim peak flows during wet weather events can make MBR Systems cost effective even when compared to conventional treatment systems such as SBRs for peak factors greater than 3:1. In fact, it may be that the combination of MBR plus SFMP has changed the calculus of wastewater treatment and reuse.

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Originally published by American Membrane Technology Association for:

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Membrane Bioreactor and i - MICRODYN-NADIR...TECHNICAL PAPER FORM NO.: TP-001 REVISION DATE: 02/05/2020 Membrane Bioreactor and i CHANGING THE CALCULUS OF WASTEWATER TREATMENT & REUSE