Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 1 of 19 

## Analysis of Organic Nitrogen Removal in Municipal Wastewater by

Reverse Osmosis

Rion Merlo 1* , Joe Wong 1

, Victor Occiano 2

, Kyle Sandera 2 , Anil Pai 2 , Seval Sen 2

, Jose Jimenez 3

, Denny Parker 1 and John Burcham 4

1 Brown and Caldwell, 201 N. Civic Drive, Suite 115, Walnut Creek, CA 94596

2 Brown and Caldwell, 9665 Chesapeake Drive, Suite 201, San Diego, CA 92123

3 Brown and Caldwell, 850 Trafalgar Court, Suite 300, Maitland, FL 32751

4 City of Escondido, 1521 S. Hale Avenue, Escondido, CA 92029

* To whom c orrespondence should be addressed. Email: rmerlo@brwncald.com

ABSTRACT

Organic nitrogen (N
org ) removal by the reverse osmosis (RO) process is not well documented in

the literature. Unlike inorganic nitrogen (i.e. ammonia, nitrate, nitrite), which is consistently

removed across a RO membrane as a function of process operation (i.e. flux and recovery), pH

and membrane type; the N org r emoval will vary depending on its charac teristics . Characteristics

of N
org that could affect its removal include size, charge and hydrophobicity. The results of a

pilot study that was conducted to determine the total nitrogen (TN) removal possible with the RO

process are presented. The N
org remo val rates are compared with removals observed from three

full

- scale RO facilities and four pilot studies. The results of this analysis suggest that RO may

not consistently produced TN levels less than 1.0 mg/L without additional treatment. Biological

nutri ent removal (BNR) followed by RO treatment would be necessary to meet stringent TN

limits. Additional processes such as coagulation or ac tivated carbon may be necessary as well

.

INTRODUCTION

The TN content of secondary effluent will consist of ammonia, n itrate, nitrite, and N
org . The N
org fraction contains particulate , colloidal and soluble species

. D issolved organi c nitrogen (DON) is

defined as the N org that passes through a 0.45

- micron membrane filter . T his definition means that

both soluble and colloidal species will be in the sample filtrate and the sum will be reported as

DON

. If the RO process is used, a microfilter (MF) or ultrafilter (UF) is typically employed

upstream of the RO as a pretreatment st ep. This means that the majority, if not all, of the N
org in

the RO feed will be DON.

For the most part, the secondary effluent DON will consist of organic material present in

drinking water

, material excreted from the activated sludge biomass (termed so luble microbial

products, SMP) , and trace materials introduced in the collection system

. Pehlivanoglu

- Mantas

and Sedlak (2008) characterized the effluent of three municipal wastewater treatment plants and

concluded that less than 30 percent of the DON was amino acids and e thylenediaminetetraacetic

acid ( EDTA ) while 70 percent was unidentified. Their results suggest that mo st of the DON in

secondary effluent is low molecular weight and hydrophilic.Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 2 of 19 Pagilla et al. (2006) reported the results of a survey of United States plants that showed that

DON accounted for greater than 20 percent of secondary effluent TN. Their survey showed DON

could account for 2 to 85 percent of effluent TN in the plants surveyed. Bratby et al. (2008)

presented th e results of a survey of secondary effluent DON that showed values ranging from 0.4

mg/L to 2.2 mg/L and an average value of 1.18 mg/L. Ik enberry et al. ( 2002 ) reported secondary

effluent DON values ranging from 1.0 mg/L to 1.5 mg/L at the Truckee Meadows Water

Reclamation Facility in Reno, Nevada. Brown et al. (2007) reported an average N org concentration of 2.9 mg/L in the secondary effluent of a biological nutrient removal ( BNR ) plant

in Stamford, Connecticut.

DON content has been shown to increase across the activated sludge process by several authors

and is attributed to SMP production

. Bratby et al. (2008) reported an increase in DON at

different points in an oxidation ditch designed for nitrogen removal. The soluble organic

nitrogen, where the colloidal fraction is removed by enhanced coagulation prior to filtration,

increased from app roximately 0.3 mg/L to approximately 0.9 mg/L. Sat t ayatewa et al. (20 09)

measured an increase in DON in the primary anoxic zone of a 4

- stage Bardenpho process and

concluded this was a result of either anoxic biological activity or heterotrophic denitrifica tion.

Parkin and McCarty (1981 ) reported that secondary effluent DON from laboratory

- scale

activated sludge reactors fed with synthetic wastewater was higher during non

- steady

- sta te

conditions than during steady

- state conditions.

N org removal was of particular importance at the Hale Avenue Resource Recovery Facility

(HARRF) in the City of Escondido (City) , California. The HARRF is an activated sludge plant

that produces 5 million gallons per day (mgd) of recyc led water and discharges a pproximately 12

mgd of treated effluent to the ocean via an outfall pipeline. Discharge of treated effluent during

wet weather is an important factor in the operation of the HARRF. While the influent wastewater

flow is the greatest during wet weather, the demand for recycled water is lowest during the same

time period . One infrequently used option is disposal of tertiary

- treated effluent to the

Escondi do Creek (live stream discharge )

.

The Intermittent Wet Weather Discharge permit issued by the San Diego Regional Water Quality

Control Board (RWQCB) places stringent re quirements on such discharges. The permit limits

are aimed at protecting water quality in the creek by preventing discharge of excessive amounts

of nutrients. Although the permit st ipulates many conditions and discharge limits on several

analytical constituents typically found in treated effluent, TN and total phosphorus (TP) are of

key importance. The permit currently in effect stipulates the following limitations for the key

analyt es listed below:

**•** TN not to excee d 35 mg/L

**•** TP not to exceed 3 mg/L

**•** 5

- day carbonaceous biochemical oxygen demand (CBOD 5 ) not to exceed 25 mg/L; and

**•** Total suspended solids (TSS) not to exceed 30 mg/L

L imitations on TN and TP may be subjected to more stringe nt criteria in the future; the discharge

limits could be reduced to 1 .0 mg/L TN and 0.1 mg/L TP. The RO process was identified as a potential means to reduce effluent TN and TP to meet these levels . A reduction in thesePreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 3 of 19 constituents would provide the City more flexibility for increasing reuse options. This paper will

report the results of the HARRF pilot study and compare the N
org removal to other RO pilot

projects and full

- scale RO facilities

.

MATERIALS AND METHODS

Pilot Site

Pilot testing of UF and RO was performed at the HARRF using three different feed waters:

secondary effluent, pilot

- scale cloth media filter (CMF) effluent and full

- scale tertiary effluent

(from existing continuous backwash filters). The HARRF secondary system is a conve ntional

activate d sludge system with secondary clarification. The system is operated at a solids retention

time (SRT) between 3 and 5 days and partially nitrifies.

Ultrafilter Pilot Unit

The UF was a pilot

- scale GE

- Zenon system

. The UF was a submerged membrane system that

u tilizes a vacuum pump for fi ltration. The UF system performed a daily tank dr ain after every

other backwash cycle (approximately every 90 minutes) to remove material that accumulated in

the process tank. The system was operated at a f lux rate ranging from 20 to 2 5 gallons per square foot per day (gfd) during the study

.

Reverse Osmosis Pilot Unit

Prior to the pilot study, a review of RO membrane technologies was performed to identify the

membrane type that would provide the highest nitrogen removal. In general, data specific to N
org removal on real world applications are limited

. T he TML

- 10 membrane manufactu red by Toray

w as selected for the pilot study based on available data . Details of the TML

- 10 membrane are

provided in Table 1. The RO skid was operated in a 3

- stage configuration. During the pilot

study, the RO was operated at a n average flux ranging from 10 gfd to 12 gfd and 80 percent

recovery. Sulfuric acid was used for pH adjustment of the RO feed t o optimize ammonia

removal . A proprietary anti

- scalant chemical was added to mitigate inorganic fouling.

Table 1. Summary of TML

- 10 Membrane Manufactured by Toray Used

for the HARRF Pilot Study

Parameter Value

Material Cross

- Linked Fully Aromatic

Polyamide Composite

Diameter 4 inch

Surface Area 73 square feet

Salt Rejection 99.7 percent

Production Flow Rate 1,850 gallons per day

Maximum Operating Pressure 600 pounds per square inch (psi)

Maximum Feed Water Temperature 45 degrees C

Acceptable Feed Water pH Range 2

- 11Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 4 of 19 Analytical Methods

Samples were collected from the UF influent and RO effluent throughout the test period.

R efrigerated composite sample rs were used for sample collection . The composite samplers were

time based; since the pilot systems were operated at a constant flow there was no need for flow

paced sampling. Table 2 summarizes the methods and detection limits that were p erformed

during the pilot study

. For purposes of data analysis of pilot data and survey results , data points

that were reported as below the detection limit were assumed to be half the detection limit value

for calculation and reporting purposes. N org is determined by subtracting the mea sured ammonia

concentration from the measured total Kjeldahl nitrogen (TKN) content.

Table 2 . Summary of Analytical Methods to Determine N org Removal Used for the

HARRF Pilot Study

Parameter Sample Location Method Detection Limit

TKN UF Influent/RO Effluent SM4500

- N(org) B 0.13 mg/L

Ammonia UF Influent/RO Effluent SM4500

- NH3 B, C 0.13 mg

- N/L

Nitrate UF Influent/RO Effluent EPA 300 0.015 mg

- N/L

Nitrite UF Influent/RO Effluent EPA 300 0.02 mg

- N/L

Pilot Schedule

The pilot study consisted of three operating periods. During Period 1, the UF/RO system was fed

with water from a pilot

- scale CMF (Aqua Aerobic

- Systems , Inc. , Rockford, IL) . The CMF

treated secondary effluent. During Period 2, the UF/RO system was fed with secondary effluent.

During Period 3, the UF/RO system was fed with tertiary effluent from the full

- scale continuous

backwash filters. Operating the UF/RO system on the continuous backwash filter effluent was

performed last because there was concern with potential irreversible fouling of the UF and RO

membranes that may be caused by the coagulant and polymer that is used prior to filtration.

Figure 1 presents a process flow diagram of the different operating periods.

Figure 1. Process flow diagram of illustrating each operating period during pilot study. HARRF

Secondary

Effluent UF/RO Pilot

System CMF Pilot

System

Tertiary Filter Period 1

Period 3 Period 2Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 5 of 19 RESULTS OF PILOT STUDY

Table 3 summarizes the UF influent nitrogen species for each of the periods and the total of all

periods. The TN content of the UF influent did not vary significantly throughout the testing

period; the average for all periods was 19.4 mg/L. For all periods, the s econdary system partially

nitrified, which is evidenced by the presence of ammonia, nitrate and nitrite in the UF influent.

The high amounts of nitrite (2.12 mg

- N/L, average) indicates the nitrification process is

incomplete in the secondary system. This i s because the secondary process is operated at a

relatively low SRT (approximately 3 to 5 days) and the dissolved oxygen (DO) concentration in

the aeration basins is approximately 1.0 mg/L. The N
org content of the UF influent was 1.97

mg/L when averaged fo r all periods. The highest N
org value measured was 2.57 mg/L. The N
org content was similar for all periods, whether or not filtration was performed upstream of the UF.

This is attributed to the low TSS content of the secondary effluent during the testing p eriod ( <10

mg/L); most of the N
org was assumed to be soluble.

Table 4 summarizes the RO effluent data collected during the pilot study. The average RO

effluent TN concentration was 1.88 mg/L. A significant fraction of the RO effluent TN consisted

of N
org (0.61 mg/L, average). Table 5 summarizes the rejection of each nitrogen species by the

UF/RO system. The average TN removal was 91 percent and the inorganic nitrogen average

rejection rates ranged from 89 to 95 percent. The N
org removal was the lowest of all nitrogen

species with an average rejection of 68 percent. There was not a significant difference in UF/RO

performance during each operation period; effluent nitrogen concentrations and rejection rates

were relatively consistent.Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 6 of 19 T able 3 . Summary of UF /RO Influent Data from HARRF Pilot Study

Parameter Unit Count Average Min Max

Period 1

TKN mg/L 5 6.82 5.43 7.50

Ammonia mg

- N/L 5 4.95 3.43 5.44

Nitrate mg

- N/L 6 8.63 7.99 9.29

Nitrite mg

- N/L 6 2.81 1.99 4.11

N org mg/L 5 1.86 1.57 2.06

TN mg/L 5 18.3 16.2 19.4

Period 2

TKN mg/L 5 13.6 9.48 15.4

Ammonia mg

- N/L 5 11.7 7.29 14.3

Nitrate mg

- N/L 9 6.39 3.44 8.77

Nitrite mg

- N/L 9 1.73 0.81 2.50

N org mg/L 5 1.93 0.81 2.54

TN mg/L 5 20.9 19.4 23.6

Period 3

TKN mg/L 5 11.9 8.11 18.4

Ammonia mg

- N/L 5 9.73 6.38 16.0

Nitrate mg

- N/L 6 4.79 3.93 6.04

Nitrite mg

- N/L 6 2.17 0.29 3.17

N org mg/L 5 2.12 1.73 2.57

TN mg/L 5 19.1 17.3 22.6

All Periods

TKN mg/L 15 10.8 5.43 18.4

Ammonia mg

- N/L 15 8.78 3.43 16.0

Nitrate mg

- N/L 21 6.57 3.44 9.29

Nitrite mg

- N/L 21 2.17 0.29 4.11

N org mg/L 15 1.97 0.81 2.57

TN mg/L 15 19.4 16.2 23.6Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 7 of 19 T able 4 . Summary of UF/RO Effluent Data from the HARRF Pilot Study

Parameter Unit Count Average Min Max

Period 1

TKN mg/L 7 0.99 0.83 1.15

Ammonia mg

- N/L 7 0.47 0.35 0.54

Nitrate mg

- N/L 7 0.53 0.35 0.75

Nitrite mg

- N/L 7 0.20 0.10 0.55

N org mg/L 7 0.52 0.41 0.66

TN mg/L 7 1.72 1.40 2.04

Period 2

TKN mg/L 10 1. 27 0.82 2. 1 1

Ammonia mg

- N/L 10 0. 6 7 0.37 1. 5 6

Nitrate mg

- N/L 11 0.48 0.18 2.06

Nitrite mg

- N/L 11 0.19 0.01 0.89

N org mg/L 10 0.60 0.32 1.35

TN mg/L 10 1.96 1.34 5.06

Period 3

TKN mg/L 5 1. 46 1.36 1.6 4

Ammonia mg

- N/L 5 0.71 0.61 0. 75

Nitrate mg

- N/L 5 0.29 0.14 0.49

Nitrite mg

- N/L 5 0.19 0.14 0.28

N org mg/L 5 0.75 0.61 1.03

TN mg/L 5 1.94 1.66 2.16

All Periods

TKN mg/L 22 1.2 2 0.82 2.1 1

Ammonia mg

- N/L 22 0.61 0.35 1. 5 6

Nitrate mg

- N/L 23 0.45 0.14 2.06

Nitrite mg

- N/L 23 0.19 < 0.0 2 0.89

N org mg/L 22 0.61 0.32 1.35

TN mg/L 22 1.88 1.34 5.06Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 8 of 19 Table 5. Summary of UF/RO Rejection Data from the HARRF

Pilot Study

Parameter Count Average Min Max

Period 1

Ammonia 5 89.3% 85.7% 91.2%

Nitrate 6 93.8% 91.3% 95.6%

Nitrite 6 92.7% 84.3% 95.6%

N org 5 71.4% 67.0% 80.1%

TN 5 90.4% 88.7% 91.7%

Period 2

Ammonia 5 94.5% 93.3% 95.8%

Nitrate 7 95.3% 94.4% 96.3%

Nitrite 7 91.5% 77.1% 99.4%

N org 5 66.1% 32.1% 78.0%

TN 5 92.4% 91.7% 94.0%

Period 3

Ammonia 4 91.7% 89.0% 95.3%

Nitrate 5 94.2% 91.8% 96.3%

Nitrite 5 82.6% 47.6% 95.4%

N org 4 66.9% 59.2% 75.2%

TN 4 89.9% 87.5% 92.7%

All Periods

Ammonia 14 91.8% 85.7% 95.8%

Nitrate 18 94.5% 91.3% 96.3%

Nitrite 18 89.4% 47.6% 99.4%

N org 14 68.2% 32.1% 80.1%

TN 14 91.0% 87.5% 94.0%

RESULTS OF SURVEY OF FULL

- SCALE FACILITIES

Data from three full

- scale facilities using the RO process to treat municipal wastewater were

analyzed and compared with the HARRF pilot study results.

Groundw ater Replenishment System

The Groundwater Replenishment System (GWRS), located in Fountain Valley, California

purifies secondary effluent wastewater for groundwater injection and for spreading basins. The

GWRS system treats secondary effluent wastewater from the Orange County Sanitation District

(OCSD) Plant Number 1. Plant Number 1 effluent con sists of a combination of effluent from a

non

- nitrifying activated sludge process and a trickling filter process.

The treatment process at GWRS consists of MF (Siemens

- Memcor ) , RO (Hydranautics ESPA2

membranes), advanced oxidation, decarbonation and lime addition . The RO membranes arePreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 9 of 19 operated at a 12

- gfd average flux and a n 85

- percent recovery. Sodium hypochlorite is added

upstream of the RO to form chloramines from the ammonia present in the wastewater at a target

of 3 mg/L total chlorine

. The RO influent pH is adjusted to 6.8 using sulfuric acid. The MF

backwash is discharged back to Plant Number 1 upstream of the primary clarifiers.

Table 6 summarizes the TKN, ammonia and N
org values for MF/RO influent and effluent for the

GWRS from February 2008 through February 2010. For N org samples where the difference

between TKN and ammonia is zero, a value of 0.05 mg/L is assumed for reporting and

calculations. The MF influent average TKN wa s 23.0 mg/L and the average ammonia

concentration was 21.0 mg/L. These values are higher than the values measured during the

HARRF pilot test because Plant Number 1 does not produce a nitrified effluent, whereas the

HARRF produces partially nitrified secondary effluent. The average N
org concentration for the

MF influent is 2.03 mg/L, which is si milar to the average value measured during the HARRF

pilot test (1.97 mg/L). It is interesting to note that the GWRS shows a much lower N
org value in

the RO effluent (0.10 mg/L) compared to the value determined for the HARRF pilot study (0.61

mg/L).

Table 7 summarizes the ammonia and N
org removal through the MF/RO system. The average

ammonia removal for GWRS (93%) is similar to the value measured for the HARRF data (92%).

There is a large difference in N
org removal bet ween the two data sets where GWRS produces

94% average N org removal and the HARRF pilot study only had 68%.

T able 6 . Summary of MF/RO Influent and Effluent Data for the GWRS
(February 2008 through February 2010)

Parameter Unit Count Average Min Max

MF Influent

TKN mg/L 115 23.0 2.50 33.0

Ammonia mg

- N/L 115 21.0 1.20 30.8

N org mg/L 115 2.03 0.30 4.20

RO Effluent

TKN mg/L 116 1. 32 0.20 2. 1 0

Ammonia mg

- N/L 116 1.24 0.20 1. 90

N org mg/L 116 0. 10 < 0. 05 0.80

Table 7. Summary of M F/RO Rejection Data for GWRS
(February 2008 through February 2010)

Parameter Count Average Min Max

Ammonia 115 93.3 % 72.7 % 96.0 %

N org 115 94.4 % 73.3 % 98.4 %

Water Replenishment District of Southern California

The Water Replenishment District (WRD) of Southern California owns and operates the Vander

Lans Facility that treats tertiary effluent from the Long Beach Wat er Reclamation PlantPreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 10 of 19 (LBWRP). The LBWRP i s a BNR plant and has tertiary filtration. The Leo J. Vander Lans

Advanced Water Treatment Faci lity (AWTF) consists of MF, RO, advance oxidation,

decarbonatoin, and sodium hypochlorite addition. The MF is a Pall Microza system and the RO

membrane is Hydra nautic ESPA2 . The RO process is operated at a n 85

- percent recovery and a n

average flux of 9.9 gfd. Sulfuric acid and threshold inhibitor are added upstream of the RO unit

. Treated effluent is pumped to the Alamitos Barrier Blend Station.

Table 8 summarizes final effluent data from the LBWRP effluent and AWTF effluent for 2009

and Table 9 summarizes the rejection rates . The average influent N org wa s 1.91 mg/L, which is

similar to the values reported at GWRS and the measured values for the HARRF pilot study.

Similar to GWRS, the N
org in the AWTF effluent is low (<0.2 mg/L). Howe ver, the a verage TN

is 1.47 mg/L.

T able 8 . Summary of WRD Data (January 2009 through December 2009)

Parameter Unit Count Average Min Max

LBWRP Final Effluent (January 2008 through December 2009)

Ammonia mg

- N/L 12 1. 07 0.58 1.72

Nitrate mg

- N/L 12 5. 85 3.92 7.71

Nitrite mg

- N/L 12 0.08 0.03 0.18

N org mg/L 12 1.91 0.90 2.79

TN mg/L 12 8. 91 6.82 11.51

AWTF Effluent (January 2009 through December 2009)

Ammonia mg

- N/L 74 0.17 <0.025 0.52

Nitrate mg

- N/L 74 1.22 0.43 3.00

Nitrite mg

- N/L 73 0.06 <0.005 0.18

N org mg/L 72 <0.2 <0.2 0.26

TN mg/L 72 1.47 0.61 3.40

Table 9. Summary of M F/RO Rejection Data for WRD

( January 2009 through December 2009 )

Parameter Count Average Min Max

Ammonia 6 81.2 % 69.7 % 88.7 %

Nitrate 6 89.8% 87.4% 94.3%

Nitrite 6 26.3% 0.00% 91.7%

N org * 6 93.5% 86.9% 96.4%

TN 6 89.5% 82.6% 94.7 %

* Calculated using half the detection limit to represent RO effluent (half of 0.2 mg/L

or 0.1 mg/L)

Scottsdale Water Campus

The Scottsdale Water Campus located in Scottsdale, Arizona is an advanced treatment facility

that produces high

- quality effluent using MF/ RO treatment. The secondary process consists of anPreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 11 of 1 9 activated sludge process operated in a Modified Lud zack

- Ettinger (M LE) configuration for

nitrogen removal. Table 10 summarizes the nitrogen specie s measured in the MF feed and RO

effluent for January 2009 through June 2010. The average N
org concentration for the MF feed

was 1.05 mg/L, which is the lowest value measured co mpared to t he HARRF pilot results,

GWRS and WRD . The average RO effluent N
org concentration was 0.14 mg/L

, which is similar

to the results obtained from the other full

- scale facilities. Table 11 summarizes the ammonia and

N org removal through the MF/RO process. T he average N
org removal was 81 percent , which is

lower than the other full

- scale facilities, but higher than the HARRF pilot results

. However, the

lower N
org removal measured at the Scottsdale Water Campus is attributed to the low MF feed

N org concentration (1.05 mg/L, average) and the RO effluent N
org detection limit. In reality, the

N org removal may be similar to the other full

- scale facilities if lower detection limits were

employed.

T able 10 . Summary of Scottsdale W ater Campus MF Feed and RO

Effluent (January 2009 through June 2010 )

Parameter Unit Count Average Min Max

MF Feed

Ammonia mg

- N/L 12 0.88 0.49 1.99

N org mg/L 12 1. 05 0.14 1.93

RO Effluent

Ammonia mg

- N/L 13 0.1 6 <0. 1 0.5 1

N org mg/L 13 0.14 <0. 1 0. 39

Table 11. Summary of M F/RO Rejection Data for Scot t sdale
Water Campus (January 2009 through June 2010)

Parameter Count Average Min Max

Ammonia * 12 78.6 % 49.9 % 95.7 %

N org * 12 80.7 % 17.1 % 98.6 %

* Calculated using half the detection limit to represent RO efflu ent

(half of 0.1 mg

- N/L or 0.05 mg/L for ammonia; half of 0.5 mg/L or

0.25 mg/L for TKN )

RESULTS FROM OTHER PILOT STUDIES

Data from four pilot studies where the RO process was used to treat municipal wastewater were analyzed and compared with the HARRF pilot study results and full

- scale facilities

.

Miami

- Dade Pilot Study

Miami

- Dade County , Florida conducted a pilot study evaluating several RO pilot processes as a part of a nutrient removal study (Botero et al., 2010) . The results of the pilot study for each of the

systems tested are presented in Table 12 . With the exception of the Hydranautics RO, all RO

systems were operated in a sing le

- stage configuration ; the Hydranautics RO was operated as

both single

- stage and 3

- stage configurations

. For the single

- stage systems

, which were conducted

mainly for performance comparison of RO membranes from various vendors, the average ROPreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 12 of 19 effluent N
org concentrations ranged from 0.32 mg/L to 0.54 mg/L. It is interesting to note that the

3

- stage system had a higher N
org concentration (0.66 mg/L) than when it was operated in a

single

- stage configuration (0.39 mg/L). This is expected since the higher recov er y will result in

higher N
org concentration at the membrane surface. The lowest average TN concentration was

1.49 mg/L for all systems. These results are similar to the results obtained from the HARRF pilot

study.

Table 12 . Summary of Miami Dade Pilot R O Effluent

TN N org

RO Pilot Process Average Minimum Maximum Average Minimum Maximum

CSM 1.49 0.20 2.10 0.34 0.10 0.60

Koch 1.51 0.90 2.10 0.32 0.10 0.80

Toray 2.01 1.20 2.80 0.38 0.10 0.90

Dow 2.30 0.12 3.60 0.54 0.10 1.50

Hydranautics 1.81 0.87 2.60 0.39 0.10 1.10

Hydranautics (Three Stage) 2.67 1.10 4.20 0.66 0.10 2.10

Luggage Point Advanced Water Treatment Plant

Schimmoller et al. (2008) presented results from a seven month pilot study. The pilot sy stem was

designed to represent the performance of the Luggage Point Advanced Water Treatment Plant in

South East Queensland, Australia. The final effluent objectives for TN were less than 0.8 mg/L.

The pilot system treated secondary effluent wastewater using flocculation and sedimentat ion,

MF, RO and advanced oxidation. Ferric chloride was added to the flocculation and

sedimentation at an average dose of approximately 100 mg/L. Ferric chloride was added to

mitigate RO fouling by removing phosphorus (to reduce calcium phosphate scaling) and

organics. An average total organic carbon (TOC) removal of 24 percent was reported during the

study. The MF system was a Pall pilot system and the RO membra nes were Toray TML

- 4040.

Table 13 summarizes the nitrogen removal reported by Schimmoller et al. (2008). Usin g the

values reported in Table 13 for TN removal, the MF/RO feed TN value must be less than 6.67

mg/L in order to meet the treatment objective of less than 0.8 mg/L of TN. The N
org removal rate

reported in Table 13 is similar to the removal de termined from the full

- scale facilities.

Table 13 . Summary of Nitrogen Removal (25

Samples) Reported by Schimmoller et al. (2008)

Parameter Value

Ammonia 83%

TKN 88%

Nitrate 87%

Nitrite 94%

N org 92%

TN 88%Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 13 of 19 Bureau of Reclamation

– Membrane Bioreactors for Water Reclamation

Adham et al. ( 2000 ) presented the results of a pilot study where MBR effluent was fed to a single

pass RO system. Table 14 summarizes the nitrogen species measured in the MBR effluent and

RO effluent. The results in Table 14 were collected from a GE

- Zenon pilot MBR and a single

stage Dow RO (BW30

- 4040) operated with a 50

- percent recovery. It is important to note that

chloramines were fed to the RO feed to mitigate biofouling on the RO membrane. The average

N org concentration in the MBR effluent was 0.76 mg/L. The average N
org concentration in th e RO

effluent was 0.10 mg/L; the average N org removal across the RO was 86.6 percent. These values

are similar to the full

- scale facilities.

Table 14

. Summary of Bureau of Reclamation Data (Adham et al., 2000)

Zenon MBR Effluent RO Effluent

Date Ammonia,

mg

- N/L TKN,

mg/L Nitrate,

mg

- N/L 1 N org , mg/L Ammonia,

mg

- N/L 2 TKN,

mg/L Nitrate,

mg

- N/L N org , mg/L N org Rem

. 08/09/99 2.08 3.04 0.96 0.96 0.54 0.65 0.50 0.10 89.2%

09/07/99 0.11 0.94 4.23 0.83 0.21 0.31 0.30 0.10 88.1%

09/21/99 0.31 1.18 2.67 0.87 0.13 0.27 0.12 0.13 84.6%

11/09/99 0.56 1.24 12.07 0.68 0.10 0.22 0.58 0.13 81.1%

01/04/00 1.28 1.91 10.85 0.63 0.07 0.11 0.63 0.04 93.2%

02/14/00 0.38 0.99 20.00 0.61 0.16 0.26 0.71 0.10 83.2%

Average 0.79 1.55 8.46 0.76 0.20 0.30 0.47 0.10 86.6%

1 MBR was operated with anoxic zone for nitrogen removal (8/9/99 through 9/21/99).

2 Chloramines were added downstream of the MBR permeate sample and upstream of the RO feed to control biological fouling

during the study.

Aqua 2000 Pilot Summary

The City of San Diego pilot tested the RO process at the San Pasqual Water Reclamation Plant

from 1996 to 1997 (Montgomery Watson, 1997) . At this time, the City considered implementing

a reuse program to supplement the drinking water supply. This initiative has not been

implemented in San Diego to date. As a part of the pilot study, several RO pr oces ses were tested

at pilot scale in conjunction with UF and MF. The UF and MF systems were fed effluent from

water hyacinth ponds (fed with municipal primary effluent) followed by ferric chloride

coagulation, sedimentation and granular filtration. The pi lot units were operated in a two

- stage

configuration at an approxim ate 75

- percent recovery. Table 15 summarizes the results of this

study. The membrane types were kept anonymous for the testing results. Table 15 shows that the

MF/UF influent N org concentration was 0.67 mg/L and the average RO effluent ranged from

<0.18 mg/L to 0.25 mg/L. These effluent values are similar to the values measured at the full

scale facilities.Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 14 of 19 Table 15 . Summary of Aqua 2000 Pilot Results for N org

RO Pilot Process Average

, mg/L Minimum

, mg/L Maximum

, mg/L

MF/UF Influent 0.67 0.1 8 2.80

MF

- RO

- A Effluent 0. 25 0.1 8 0. 77

MF

- RO

- B Effluent < 0. 18

--- ---

MF

- RO

- C Effluent < 0. 18

--- ---

MF

- RO

- D Effluent 0. 20 <0.18 0.27

UF

- RO

- A Effluent < 0. 18

--- ---

UF

- RO

- B Effluent < 0. 18

--- ---

UF

- RO

- C Effluent < 0. 18

--- ---

DISCUSSION

Figure 2 presents a summary of the average N
org concentration measured in RO effluent from the

HARRF pilot study results and the survey results. The Miami

- Dade and HARRF pilot studies

, which treated partially nitrified effluent, had the highest RO effluent N
org concentrations. In

general, the full

- scale plants had relatively low N
org content (<0.1 mg/L) in the RO effluent. It is

not possible to draw any significant conclusions regarding the di fferences in RO performance

between data sets since the nature of the N
org has not been characterized at each site . The N
org concentration in the secondary effluent will consist of material present in the drinking water,

SMP produced in the secondary syste m and trace materials introduced in the collection system.

This means that not only the influent wastewater, but also the secondary process operation, will

affect the N
org con centration and characteristics. Figure 3 summarizes the N
org removal measured

by the MF/RO (or UF/RO, depending on the data set) process. The removals rates determined

from these data sets vary from less than 70% to greater than 90%.Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 15 of 19 Figure 2

. S ummary of average RO effluent N org values (values that were less than the

detection limit are expressed as half the detection limit value)

Figure 3

. Summary of average N
org Removal through UF/RO or MF/RO

. 0.01 0.10 1.00Average RO Effluent NorgConcentration, mg/L

0 10 20 30 40 50 60 70 80 90 100

GWRS WRD Luggage Point Scottsdale Water

Campus HARRF Pilot StudyNorgRemoval, percentPreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 16 of 19 Table 16 presents the results of a sensitivity analysis designed to evaluate the impact of upstream

nitrogen removal on the final TN concentration after RO. The average effluent TN

concentrations for the two nutrient removal processes that would feed the RO were assumed to

be 10 mg/L and 4 mg/L. Representative technolo gies that could achieve a TN of 10 mg/L would

be the MLE or step feed BNR processes. Representative technologie s that could achieve a TN of

4 mg/L would be the Bardenpho process, or the MLE ( or step feed ) process followed by

denitrifying filters. A range o f secondary effluent N
org (1.0 mg/L to 3.0 mg/L) and a range of N
org removal by RO (50 percent to 90 percent) were used for the analysis. The average ammonia and

nitrate removals by RO measured during the HARRF pilot study were assumed.

Table 16 shows tha t significant nitrogen removal upstream of the RO process would be

necessary to achieve a TN concentration of less than 1.0 mg/L . As the level of nutrient removal

increases, the RO process is more likely to achieve a TN concentration of less than 1.0 mg/L.

L ess upstream nutrient removal could result in the necessity of additional treatment to remove

nitrogen species in addition to RO. In addition, higher concentrations of N
org in the secondary

effluent could result in the necessity for additional treatment.

In order to meet an annual average limit for TN of less than 1.0 mg/L, a safety factor would need

to be assumed using the results in Table 16 to reduce the likelihood of a violation occurring in a

permit cycle. It is important to note that the analysis p resented in Table 16 only considers the

average removal rates and assumed average nitrogen content in the secondary effluent. If permit

requirements were written such that monthly or daily maximum TN value of less that 1.0 mg/L

were necessary, additional n itrogen removal will be necessary.

The results presented in Table 16 agree with the data presented by Schimmoller et al. (2008) who

showed that RO effluent could produce TN less than 1.0 mg/L. This required nutrient removal in

the secondary system to remo ve the majority of the inorganic nitrogen. In addition, it is possible

that the FeCl 3 addition used to mitigate phosphorus reported in Schimmoller et al. (2008) could

have contributed to a significant reduction in N
org .

There are other processes that could be used to remove N
org in addition to RO. Bratby et al.

(2008) presented results of survey that showed that enhanced coagulation removed, on average,

31 percent of DON in secondary effluent wastewater. Arnaldos and Pagi lla (2010) performed

batch coagulation and microfiltration experiments using secondary effluent from a full

- scale

wastewater plant. Their results showed that DON could be reduced from approximately 1.2 mg/L

to approximately 0.3 mg/L using aluminum sulfate at a molar ratio dose of 1.4 Al(III)/initial

DON. They attributed most of the removal to the coagulation, rather than the microfiltration.

Parkin and McCarty (1981) showed that activated carbon could be effective for DON removal

with an average measured va lue of 72 percent.Preprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 17 of 19 Table 16. TN Removal Sensitivity Analysis Using Different Nutrient Removal Processes and a Range of Secondary Effluent N org

Nutrient

Removal

Process Sec. Eff.

N org Conc.,

mg/L Sec. Eff.

Ammonia

Conc.,

mg

- N/L Sec. Eff.

Nitrate

Conc.,

mg/L Norg

Removal,

percent Ammonia

Removal,

percent Nitrate

Removal,

percent RO Eff.

N org Conc.,

mg/L RO Eff.

Ammonia

Conc.,

mg

- N/L RO Eff.

Nitrate

Conc.,

mg

- N/L RO Eff.

TN Conc.,

mg/L Add. N org Removal,

mg/LTN = 10 mg/LRepresentative Technologies: MLE, Step FeedBNR 1.0 0.2 8.8 65 91.8 94.5 0.35 0.02 0.48 0.85 NA

1.0 0.2 8.8 75 91.8 94.5 0.25 0.02 0.48 0.75 NA

1.0 0.2 8.8 85 91.8 94.5 0.15 0.02 0.48 0.65 NA

1.0 0.2 8.8 95 91.8 94.5 0.05 0.02 0.48 0.55 NA

2.0 0.2 7.8 65 91.8 94.5 0.70 0.02 0.43 1.15 0.15

2.0 0.2 7.8 75 91.8 94.5 0.50 0.02 0.43 0.95 NA

2.0 0.2 7.8 85 91.8 94.5 0.30 0.02 0.43 0.75 NA

2.0 0.2 7.8 95 91.8 94.5 0.10 0.02 0.43 0.55 NA

3.0 0.2 6.8 65 91.8 94.5 1.05 0.02 0.37 1.44 0.44

3.0 0.2 6.8 75 91.8 94.5 0.75 0.02 0.37 1.14 0.14

3.0 0.2 6.8 85 91.8 94.5 0.45 0.02 0.37 0.84 NA

3.0 0.2 6.8 95 91.8 94.5 0.15 0.02 0.37 0.54 NATN = 4 mg/LRepresentative Technologies: Bardenpho, MLE(or step feed)with dentrifying filters 1.0 0.2 2.8 65 91 .8 94.5 0.35 0.02 0.15 0.52 NA

1.0 0.2 2.8 75 91.8 94.5 0.25 0.02 0.15 0.42 NA

1.0 0.2 2.8 85 91.8 94.5 0.15 0.02 0.15 0.32 NA

1.0 0.2 2.8 95 91.8 94.5 0.05 0.02 0.15 0.22 NA

2.0 0.2 1.8 65 91.8 94.5 0.70 0.02 0.10 0.82 NA

2.0 0.2 1.8 75 91.8 94.5 0.50 0.02 0.10 0.62 NA

2.0 0.2 1.8 85 91.8 94.5 0.30 0.02 0.10 0.42 NA

2.0 0.2 1.8 95 91.8 94.5 0.10 0.02 0.10 0.22 NA

3.0 0.2 0.8 65 91.8 94.5 1.05 0.02 0.04 1.11 0.11

3.0 0.2 0.8 75 91.8 94.5 0.75 0.02 0.04 0.81 NA

3.0 0.2 0.8 85 91.8 94.5 0.45 0.02 0.04 0.51 NA

3.0 0.2 0.8 95 91.8 94.5 0.15 0.02 0.04 0.21 NAPreprint, Nutrient Recovery and Management 2011, January 9

- 12, 2011, Miami, FL Page 18 of 19 CONCLUSIONS

The RO process is designed to remove charged species. Manufacturer reported rejection rates for

ammonia, nitrate and nitrite can be used to estimate the removal of these parameters at full

- scale.

However, the nature and concentration of N
org in secondary effluent will vary dependin g on the

wastewater. Therefore, it is not possible to know the actual N
org concentration in RO effluent

without testing. The N
org in secondary effluent can consist of low molecular weight and

uncharged species that may not be removed through the RO process . In short, the RO process is

not designed to effectively remove N
org , it is designed to removed charged ionic species

.

For municipalities that are evaluating processes to achieve low TN levels, the concentration and

characteristics of N org is crucial and may require additional treatment

. Upstream BNR to target

inorganic nitrogen coupled with a physical/ chemical process (i.e. coagulation or activated

carbon ) to target N org could be potential solutions.

ACKNOWLEDGEMENTS

The authors wish to acknowledg e the HARRF operations, maintenance and laboratory staff who

contributed to the pilot study. Specifically , we would like to acknowledge Dennis Sperino, James

Larzalere

, Pete Klein, and Vasana Vipatapat

. The authors would like to acknowledge all of the

people who contributed data to this effort. These include: Mehul Patel (GWRS), Paul Fu (WRD)

, Binga Talabi (Scottsdale Water Campus) and David Faber (Woongjin CSM)

.

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