Biological Treatment and Downstream Processing of Perchlorate

Subject Area:High-Quality Water

Biological Treatment andDownstream Processing ofPerchlorate-ContaminatedWater

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Prepared by:Patrick J. Evans CDM11811 N.E. First Street, Suite 201, Bellevue, WA 98005and

Bruce E. LoganDepartment of Civil and Environmental EngineeringThe Pennsylvania State University, University Park, PA 16802

Jointly sponsored by:Awwa Research Foundation6666 West Quincy Avenue, Denver, CO 80235-3098

U.S. Environmental Protection AgencyWashington D.C.and

East Valley Water DistrictSan Bernardino, CA

Published by:


mailto:[email protected]

Copyright © 2004by Awwa Research Foundation

All Rights Reserved

Printed in the U.S.A.

DISCLAIMER

This study was jointly funded by the Awwa Research Foundation (AwwaRF), the U.S. Environmental ProtectionAgency (USEPA), and East Valley Water District (EVWD) under Cooperative Agreeement No. R-82642201.AwwaRF, USEPA, and EVWD assume no responsibility for the content of the research study reported in thispublication or for the opinions or statements of fact expressed in the report. The mention of trade names for

commercial products does not represent or imply the approval or endorsement of AwwaRF, USEPA, or EVWD.This report is presented solely for informational purposes.

Printed on recycled paper


v

CONTENTS

LIST OF TABLES....................................................................................................................... vii

LIST OF FIGURES ...................................................................................................................... ix

FOREWORD ............................................................................................................................... xi

ACKNOWLEDGMENTS .......................................................................................................... xiii

EXECUTIVE SUMMARY .......................................................................................................... xv

CHAPTER 1: INTRODUCTION.................................................................................................. 1

Background......................................................................................................................... 1

Approach and Objectives.................................................................................................... 2

CHAPTER 2: METHODS ............................................................................................................ 5

Texas Street Wellhead Facility ........................................................................................... 5

Pilot Test Equipment Design .............................................................................................. 6

Pilot Test Equipment Startup and Operation ...................................................................... 9

Culture Medium and Pilot Plant Feed Solutions..................................................... 9

Packed Bed Reactor Startup ................................................................................. 10

Pilot Plant Operation ............................................................................................ 11

Sampling and Analysis ..................................................................................................... 11

CHAPTER 3: RESULTS.............................................................................................................. 13

Packed Bed Reactor Operation ......................................................................................... 13

Aerator and Anthracite Filter Operation ........................................................................... 14

Steady State Pilot Plant Operation.................................................................................... 17

CHAPTER 4: CONCLUSIONS ................................................................................................... 21

APPENDIX ................................................................................................................................23

REFERENCES ............................................................................................................................. 29

ABBREVIATIONS ...................................................................................................................... 31


vii

TABLES 2.1 Representative Redlands groundwater composition.............................................................. 5

2.2 Sampling and analysis procedures ......................................................................................... 12

3.1 Final steady state operating conditions .................................................................................. 17

3.2 Average steady state performance results for days 83 through 92 ........................................ 18

3.3 Air scour and backwash performance.................................................................................... 19


ix

FIGURES 2.1 Existing Texas Street Wellhead Facility process flow diagram ............................................ 5

2.2 Existing Texas Street Wellhead Facility................................................................................ 6

2.3 Pilot test equipment process flow diagram for normal operation .......................................... 7

2.4 Pilot test packed bed reactor prior to startup ......................................................................... 8

2.5 Rauschert Bioflow 9 medium ................................................................................................ 9

3.1 Perchlorate concentrations and flow rate data for the packed bed reactor ............................ 14

3.2a Effects of Rauschert medium and ferric chloride in aerator on effluent turbidity and

headloss in the anthracite filter .............................................................................................. 15

3.2b Effects of Rauschert medium and ferric chloride in aerator on effluent turbidity and

turbidity removal by the anthracite filter .............................................................................. 16

3.3 Steady state differential pressure accumulation in the packed bed reactor and the

anthracite filter ....................................................................................................................... 20


xi

FOREWORD

The AwwaRF is a nonprofit corporation that is dedicated to the implementation of a

research effort to help utilities respond to regulatory requirements and traditional high-priority

concerns of the industry. The research agenda is developed through a process of consultation

with subscribers and drinking water professionals. Under the umbrella of a Strategic Research

Plan, the Research Advisory Council prioritizes the suggested projects based upon current and

future needs, applicability, and past work; the recommendations are forwarded to the Board of

Trustees for final selection. The foundation also sponsors research projects through the

unsolicited proposal process; the Collaborative Research, Research Applications, and Tailored

Collaboration programs; and various joint research efforts with organizations such as the U.S.

Environmental Protection Agency, the U.S. Bureau of Reclamation, and the Association of

California Water Agencies.

This publication is a result of one of these sponsored studies, and it is hoped that its

findings will be applied in communities throughout the world. The following report serves not

only as a means of communicating the results of the water industry's centralized research

program but also as a tool to enlist the further support of the nonmember utilities and individuals.

Projects are managed closely from their inception to the final report by the foundation's

staff and large cadre of volunteers who willingly contribute their time and expertise. The

foundation serves a planning and management function and awards contracts to other institutions

such as water utilities, universities, and engineering firms. The funding for this research effort

comes primarily from the Subscription Program, through which water utilities subscribe to the

research program and make an annual payment proportionate to the volume of water they deliver

and consultants and manufacturers subscribe based on their annual billings. The program offers

a cost-effective and fair method for funding research in the public interest.

A broad spectrum of water supply issues is addressed by the foundation's research

agenda: resources, treatment and operations, distribution and storage, water quality and analysis,

toxicology, economics, and management. The ultimate purpose of the coordinated effort is to

assist water suppliers to provide the highest possible quality of water economically and reliably.

The true benefits are realized when the results are implemented at the utility level. The

foundation's trustees are pleased to offer this publication as a contribution toward that end.


xii

Edmund G. Archuleta, P.E. James F. Manwaring, P.E. Chair, Board of Trustees Executive Director Awwa Research Foundation Awwa Research Foundation


xiii

ACKNOWLEDGMENTS The authors are grateful for the funding provided by the Awwa Research Foundation and

the U.S. Environmental Protection Agency, which was obtained by the East Valley Water

District through efforts of Robert Martin and Congressman Jerry Lewis (CA).

The authors of this report are indebted to the following individuals and water utility for

their cooperation and participation in this project: Douglas Headrick, David Commons, and the

City of Redlands, California for providing access and assistance at the Texas Street facility; and

David Jones for chemical analysis conducted at PSU. In addition, we thank Frank Blaha and the

members of the PAC for their comments and guidance during the course of this project.


xv

EXECUTIVE SUMMARY

A cost-effective process for potable water production from perchlorate-contaminated

groundwater is a pressing need. Biological treatment is one such process that has the potential to

be more cost effective than currently used physical processes such as ion exchange. Biological

treatment has been used for perchlorate treatment but not for potable water generation from

perchlorate-contaminated water. Previous project work focused on determination of

requirements for successful biological treatment of perchlorate-contaminated water. This

supplemental study was undertaken to test, at pilot scale, processes downstream of biological

treatment needed to produce water suitable for potable uses. In particular this phase of the work

was designed to test new downstream processes capable of removing turbidity and nutrients.

Pilot-scale testing was conducted at the Texas Street Wellhead Facility in Redlands,

California where groundwater contains 59 to 120 µg/L of perchlorate. Groundwater was

pumped from groundwater extraction wells to the packed bed reactor. Solutions of acetic acid

and nutrients (i.e., monobasic ammonium phosphate) were pumped into the groundwater stream

prior to entering the reactor. The amended groundwater flowed upward through the reactor and

then overflowed by gravity into the aerator. Ferric chloride solution was added to the aerator as

a coagulant in selected tests. Oxygenated water was then pumped to the top of the flooded

anthracite filter at a rate slightly less than the packed bed reactor flow rate to maintain a constant

level in the aerator via overflow to waste. Water flowed out of the anthracite filter through a

siphon break designed to maintain flooded conditions in the filter.

The following conclusions were made based on the results of this testing:

• Complete removal of perchlorate from Redlands water was achieved in the packed bed

reactor with an empty bed contact time of 40 minutes.

• Shutdown of the packed bed reactor for two weeks because of groundwater extraction

equipment failure did not adversely affect packed bed reactor operation.

• An influent acetate concentration of 38 mg/L was more than sufficient for complete

perchlorate removal and resulted in 16 mg/L acetate in the packed bed reactor effluent.


xvi

• An aerobic biotreatment process is required between the packed bed reactor and the

anthracite filter to remove excess acetate and provide acceptable performance of the

anthracite filter.

• Addition of 2 mg-Fe/L of ferric chloride in the aerator plus use of a 32-inch bed of 1-

mm anthracite was capable of turbidity removal to less than 0.3 NTU.

• Air scouring and backwashing of the packed bed reactor at least weekly and of the

anthracite filter at least twice weekly appears to be sufficient for stable operation.

• Steady-state operation of an anaerobic biological packed bed reactor in combination

with a downstream aerobic bioreactor-anthracite filter combination was capable of

successfully treating Redlands groundwater to potable water standards.


1

CHAPTER 1

INTRODUCTION

BACKGROUND

A cost-effective process for potable water production from perchlorate-contaminated

groundwater is a pressing need. Biological treatment is one such process that has the potential to

be more cost effective than currently used physical processes such as ion exchange (AwwaRF

2004). Biological treatment has been used for perchlorate treatment but not for potable water

generation from perchlorate-contaminated water.

Potable water must meet a number of requirements. These requirements have been

reviewed previously (AwwaRF, 2004) and include various rules under the Safe Drinking Water

Act (SDWA). An example of such a requirement that is directly applicable to biological

treatment is the U.S. Environmental Protection Agency (US EPA) secondary maximum

contaminant level (MCL) on turbidity of 0.3 nephalometric turbidity units (NTU). Additionally,

local requirements can be imposed such as those outlined in the April 2, 2002 California

Department of Health Services (DHS) conditional acceptance letter on a biological perchlorate

treatment process (see Appendix). These requirements vary and can be process-specific.

Finally, engineering design of potable water generation systems typically imposes additional

requirements on various unregulated parameters such as total organic carbon and ammonia.

Thus, successful removal of perchlorate is only part of the challenge with respect to

potable water generation using biological treatment. Downstream processing is also necessary to

meet regulatory requirements and engineering standards. Previous work addressed perchlorate

removal and culminated in the successful pilot-scale demonstration of a packed-bed biological

perchlorate removal process at the Texas Street Wellhead Facility in Redlands, California.

These results are described in detail in a report describing this previous work (AwwaRF 2004).

These results indicated that an acetate-fed packed bed reactor was capable of removing nitrate

and perchlorate to nondetectable concentrations. Use of a plastic packing medium was

determined to be superior to a sand packing medium with respect to operability and

dependability. Air scouring and backwashing of the packed bed reactor was determined to be

critical and resulted in successful reactor operation when conducted weekly. This report


2

presented a conceptual design of a potable water generation system employing a biological

packed bed reactor. The following lists the process elements identified in the conceptual design

based on implementing a process at the Texas Street Wellhead Facility:

• Groundwater extraction and pumping (existing)

• Granular activated carbon adsorption of volatile organic compounds (existing)

• Anaerobic biological packed bed reactor removal of nitrate and perchlorate (new)

• Aeration (new downstream process)

• High rate biological sand filtration for removal of organic carbon and turbidity (new

downstream process)

• Booster pumping (new downstream process)

• Ultraviolet light disinfection (new downstream process)

• Chlorination (existing downstream process)

• Storage (existing)

• Booster pumping (existing)

An economic evaluation was conducted based on this conceptual design and comparisons

were made to a biological fluidized bed reactor and a nonbiological ion exchange processes. The

biological processes were determined to be significantly less expensive than the ion exchange

processes (AwwaRF 2004).

APPROACH AND OBJECTIVES

This supplemental study was undertaken to test, at pilot scale, processes downstream of

biological treatment needed to produce water suitable for potable uses. This work was designed

to test the packed bed reactor in combination with new downstream processes capable of

removing turbidity and nutrients. It was assumed the disinfection process, using ultraviolet light,

could be designed using available information. Additionally, this supplemental work also

included further optimization of the anaerobic biological packed bed reactor process. The

objectives of this supplemental work were as follows:


3

• Achieve continuous perchlorate removal in the pilot scale reactor to test downstream

potable water production processes.

• Determine if the hydraulic residence time in the perchlorate removal process can be

reduced using a higher specific surface area medium compared to that used in the

previous pilot test.

• Characterize the performance of the selected downstream processes with respect to

nutrient and turbidity removal and headloss accumulation.

• Evaluate the impact of the pilot-scale results on conceptual design and operations and

maintenance of full-scale potable water systems.

• Show stable operation of the system under conditions determined from the above

studies for achieving complete perchlorate removal, nutrient removal, and target

turbidity values of less than 0.3 NTU.


5

CHAPTER 2

METHODS

TEXAS STREET WELLHEAD FACILITY

Pilot-scale testing was conducted at the Texas Street Wellhead Facility in Redlands,

California. Figure 2.1 illustrates a process flow diagram for the facility that has a capacity of 10

million gallons per day (mgd) of potable water. Figure 2.2 is a photograph of the existing

granular activated carbon vessels with the one-million gallon storage tank in the background.

Existing granular carbon adsorption vessels are used to remove chlorinated volatile organic

compounds from groundwater. Table 2.1 lists the representative concentrations of chlorinated

volatile organic compounds, perchlorate, nitrate, and dissolved oxygen in Redlands

groundwater.

EXISTING WELLSGAC UNITS(24 TOTAL)

TEXAS STREET RESERVOIR(1 MILLION GALLONS) BOOSTER PUMPS

CHLORINEINJECTION

TO DISTRIBUTIONSYSTEM

Figure 2.1 Existing Texas Street Wellhead Facility process flow diagram

Table 2.1

Representative Redlands groundwater composition

Parameter Units Concentration range

Perchlorate µg/L 59 - 120

Nitrate mg-N/L 4.0 - 4.5

Dissolved oxygen mg/L 8 - 10

Trichloroethene µg/L 3 - 5

1,1-Dichloroethene µg/L 1 - 2


6

Figure 2.2 Existing Texas Street Wellhead Facility

PILOT TEST EQUIPMENT DESIGN

Figure 2.3 illustrates a process flow diagram of the pilot test equipment showing major

equipment, flow paths for water and air, and sampling locations and designations. Groundwater

was pumped from the groundwater extraction wells to the packed bed reactor. Solutions of

acetic acid and nutrients (i.e., monobasic ammonium phosphate) were pumped into the

groundwater stream prior to entering the reactor. The amended groundwater flowed upward

through the reactor and then overflowed by gravity into the aerator. Ferric chloride solution was

added to the aerator as a coagulant in selected tests. Oxygenated water was then pumped to the

top of the flooded anthracite filter at a rate slightly less than the packed bed reactor flow rate to

maintain a constant level in the aerator via overflow to waste. Water flowed out of the anthracite

filter through a siphon break designed to maintain flooded conditions in the filter. Figure 2.3

does not show the backwash and air scour systems used for both the reactor and the filter. These

systems were identical to those used in the previous pilot test work (AwwaRF 2004).


7

Figure 2.3 Pilot test equipment process flow diagram for normal operation

Figure 2.4 is a photograph of the packed bed reactor that was modified prior to startup of

this supplemental work. The pilot test equipment comprised two side-by-side compartments

each having a 2-ft2 cross-sectional area to flow and a 7-ft height. One side was used as the

packed bed reactor and the other side was used as the anthracite filter.

The packed bed reactor was filled with random packing medium (about 8 ft3; Rauschert

Bioflow 9). The Rauschert Bioflow 9 medium had a surface area of 195 ft2/ft3 and was selected

based on earlier results. During this earlier work, the tested sand medium had a high particle

surface area (estimated at 1,800 ft2/ft3) and was found to have a higher unit rate of biological

activity than the plastic media (Jaeger Tripack 1.25-inch plastic medium, 70 ft2/ft3 surface area).

The empty bed contact time needed for the sand medium was less than 30 minutes compared to

at least 60 minutes needed for plastic medium. However, the sand medium was prone to

plugging and other operational problems. Therefore, the Rauschert Bioflow 9 medium was used

because it had a higher specific surface area than the Jaeger Tripack medium and would be less

prone to plugging than the sand medium. In addition, the Rauschert Bioflow 9 medium was

chosen to have a higher particle specific gravity (1.15) compared to the Jaeger Tripack medium

(less than 1) that floated in water. The greater specific gravity of the Rauschert Bioflow 9

Groundwater

Acetate

Nutrients

Ferric chloride

Air

Air Exhaust

Effluent

Sample A

Anaerobic Biological Packed Bed Reactor

Anthracite Filter

Aerator

Pump Sample

B

Sample C

Sample D

Sample E

Siphon Break

Overflow


8

medium still required it to be mechanically held down in the bioreactor during operation in part

because of gas bubble formation associated with denitrification. The Rauschert Bioflow 9

medium was selected as a compromise between the sand and plastic medium used in earlier

work. Figure 2.5 is a photograph of the Rauschert Bioflow 9 medium.

Figure 2.4 Pilot test packed bed reactor prior to startup

The aerator was a 55-gallon plastic drum modified to contain a fine-bubble sparging

element in the bottom to promote efficient oxygenation. Some of the recent tests involved

addition of Rauschert Bioflow 9 medium to the aerator to promote attached growth of aerobic

bacteria. In these tests a coarse screen was attached to the aerator outlet to keep the Rauschert

medium in the aerator.


9

Figure 2.5 Rauschert Bioflow 9 medium

The anthracite filter was filled with about 8 ft3 of anthracite obtained from Unifilt Corp.

(Zelienople, Pennsylvania) with an effective size of 0.95 to 1.05 mm, a uniformity coefficient

equal to or less than 1.4, and a particle specific gravity equal to or greater than 1.6. The

anthracite was supported by 6 inches each of 1/4" x #6 gravel and #6 x #14 gravel. A fine screen

was used to retain the anthracite in the filter during backwash and air scouring.

PILOT TEST EQUIPMENT STARTUP AND OPERATION

Culture Medium and Pilot Plant Feed Solutions

The culture medium used for growing the perchlorate-degrading microorganism

Dechlorosoma sp. KJ (AwwaRF 2004) was prepared with 300 mg/L NaClO4, 450 mg/L

NaCH3COO, buffer solution, and trace metal solution. Solutions were prepared with deionized

water in the laboratory and with Redlands groundwater at the pilot plant. The buffer solution

consisted of 1.92 g K2HPO4, 0.98 g NaH2PO4H2O, and 0.5 g NH4H2PO4 per liter of medium.

The metal solution contained the following constituents per liter of a medium: 55 mg

MgSO47H2O, 0.6 mg H3BO3, 1 mg CaCl26H2O, 0.4 mg CoCl26H2O, 0.2 mg CuSO46H2O, 3 mg

EDTA, 4 mg FeSO47H2O, 1 mg MnCl24H2O, 0.1 mg NiCl26H2O, 0.4 mg NaMoO42H2O, 0.15

mg NaSeO35H2O, and 2 mg ZnSO47H2O. Culture medium used in the laboratory was

autoclaved using a steam sterilizer before it was inoculated with bacteria. Culture medium

prepared at the pilot plant site was not sterilized.


10

Feed to the reactors consisted of diluted glacial acetic acid (10 percent by volume) that

was pumped into the reactor feed line to serve as a carbon source and electron donor for bacteria.

The initial targeted influent acetic acid concentration was 40 mg/L. Twenty percent monobasic

ammonium phosphate (NH4H2PO4) solution was used as a source of nitrogen and phosphorous

nutrients. The initial influent concentration of monobasic ammonium phosphate was 8.2 mg/L

for an initial targeted influent nitrogen concentration of 1 mg-N/L.

Ferric chloride solution at a concentration of 6.6 g/L as ferric chloride was used as a

flocculant starting on May 23, 2003 (Day 57). The ferric chloride solution was pumped into the

aerator for a final concentration of 2.0 mg/L as iron.

Packed Bed Reactor Startup

A perchlorate-reducing bacterium, Dechlorosoma sp. KJ, isolated from a perchlorate-

degrading bioreactor, was used to inoculate the packed bed reactor (AwwaRF 2004). The isolate

KJ was enriched in an Erlenmeyer flask containing the culture medium described below. The

pure culture (1 mL) was transferred weekly into freshly prepared medium (200 mL) in an

anaerobic glove box in the PSU Kappe laboratories. On March 25, 2003 (Day 0), 1 gal of the

culture was poured into the packed bed reactor that had previously been filled with the Rauschert

Bioflow 9 medium, and culture medium prepared with Redlands groundwater and containing

sodium perchlorate and sodium acetate in the same concentrations as those used for culture

growth. The groundwater was circulated through the packed bed reactor for several minutes in

order to distribute the bacteria over the Rauschert Bioflow 9 medium and then the pump was

turned off. The culture grew in the reactor over the next two days as indicated by increased

turbidity and decreased dissolved oxygen. On March 27, 2003 (Day 2) flow through conditions

were initiated with a flow rate of 5 gal/min through the packed bed reactor and 4 gal/min through

the anthracite filter. Ammonium phosphate and acetic acid solution flow rates were initiated at

this time to target influent (i.e., at sample point B shown on Figure 2.3) acetic acid and nitrogen

concentrations of 40 mg/L and 1 mg-N/L, respectively. Air flow in the aerator was initiated at 3

cfm.


11

Pilot Plant Operation

The pilot plant was operated continuously (except as noted) and sampled Monday

through Friday with periodic weekend visits. Typical operation involved measurement of flow

rates and pressures and adjustment flow rates as necessary to maintain desired operating

conditions. Measurements were always recorded prior to any adjustments made each day.

Samples were collected and analyzed as described below. Air scouring and backwashing were

conducted on an as needed basis determined by visual observation of the reactor and filter beds

and pressure drops across the beds. Various conditions were evaluated and air scouring for 5

minutes followed by backwashing for 5 minutes was found to have acceptable performance. Air

scour flow rates were 4 cfm and 3 cfm for the packed bed reactor and anthracite filter,

respectively. Backwash flow was 40 gal/min each for the reactor and filter. Maintenance

included cleaning fouled lines and instruments and was conducted on an as-needed basis. The

general pilot testing approach involved the following elements:

• Startup, establishment of biofilm, and troubleshooting of analytical methods

• Determination of optimal packed bed reactor flow rate for perchlorate destruction

• Determination of downstream processing modifications and operations required to

obtain satisfactory effluent characteristics

• Determination of optimal air scour and backwash operations

• Operation of the pilot plant at steady state conditions and collection of associated

performance data

SAMPLING AND ANALYSIS

Samples were collected from sample ports A, B, C, D, and E as shown in Figure 2.3. The

sampling frequency varied depending on whether testing was in the optimization phase or the

steady state data collection phase as shown in Table 2.2. Analytical methods included a

combination of fixed laboratory methods implemented at PSU and field-testing methods also

shown in Table 2.2. Further details on laboratory methods and quality assurance/quality control

procedures are presented in the previous report on this work (AwwaRF 2004).


12

Table 2.2

Sampling and analysis procedures

Minimum sample frequency Measurement Optimization Steady state Preservation Analytical method

Perchlorate (influent and effluent)

3 per week 3 per week Filtration, 4○C Ion

chromatography

Acetate (influent and effluent)

3 per week 3 per week Filtration, 4○C,

H2SO4

Ion

chromatography

Nitrate (influent and effluent)

3 per week 3 per week None Chemetrics field

test kit

Nitrite (influent and effluent)


test kit

Phosphate 0 per week 5 per week Filtration, 4○C Ion

chromatography

Ammonia 5 per week 5 per week None Chemetrics field

test kit

Ultraviolet absorbance 0 per week 5 per week Filtration, 4○C,

HCl

Spectrophotometry

at 254 nm

Total organic carbon, dissolved organic carbon

0 per week 5 per week Filtration, 4○C,

HCl

Standard Method

5310B

pH (influent and effluent)

3 per week 3 per week None pH probe

Dissolved oxygen (influent and effluent)


test kit

Turbidity (effluent)

3 per week 3 per week None Hach tubidometer

Water and air flow rates

3 per week 3 per week NA Rotameters

Nutrient flow rates

5 per week 5 per week NA Graduated cylinder

Pressure

5 per week 5 per week NA Pressure gauge


13

CHAPTER 3

RESULTS

PACKED BED REACTOR OPERATION

Figure 3.1 shows packed bed reactor influent and effluent perchlorate concentrations and

flow rates. During the first 62 days of operation various flow rates ranging from 1 gal/min to 5

gal/min were evaluated. During this time a biofilm was being established on the Rauschert

medium and significant perchlorate removal was not observed until Day 32. At this time a

decision was made to decrease the flow rate from 5 gal/min because analytical data were being

obtained several days after samples were collected and acceptable perchlorate removal at 5

gal/min was not expected. Nevertheless, continued operation at a flow rate of 2.5 gal/min

resulted in 76 to 93 percent, but incomplete, perchlorate removal. Decreased perchlorate

removal of 22 percent was observed on Day 42 and was attributable to a power interruption on

Day 41 and resultant low acetic acid concentrations in the packed bed reactor on Day 42. The

flow rate was reduced to 1 gal/min subsequently and complete perchlorate removal was

observed. The varying effluent perchlorate concentrations following Day 42 are attributable to

variable analytical detection limits. On Day 63 an “optimal” flow rate of 1.5 gal/min was

selected for continued operation and collection of steady state data. This flow rate represented

an empty bed contact time of 40 minutes. A flow rate of 2.0 gal/min was not evaluated but

might be sufficient for complete perchlorate removal. This flow rate would represent a 30 min

empty bed contact time.

On Day 65 the facility groundwater extraction pumps failed and replacement parts were

not obtainable by the City of Redlands for 14 days. During this time the pilot plant was

inoperable and was allowed to remain filled with groundwater so as to not expose the

perchlorate-reducing bacteria to oxygen. The outages and other experiences during the pilot

testing highlight the importance of providing redundancy and reliability into the design of a full-

scale system. The performance of the pilot plant significantly depended on the consistency of

operations.

On Day 76 the water supply was restored and the pilot plant was restarted. The first

sample that was collected on Day 82 demonstrated 81 percent perchlorate removal and an


14

effluent concentration of 9.8 µg/L. Complete perchlorate removal was observed the next day

(detection limit 3 µg/L). While samples for perchlorate analysis were not collected on Day 76,

samples were collected on Day 78 and analyzed for dissolved oxygen and nitrate. These

analyses indicated complete removal indicating fast recovery of the packed bed reactor following

2 weeks of shutdown. Complete perchlorate removal (based on variable analytical detection

limits) was achieved for the final 10 days of steady state operation until the pilot plant was shut

down.

Figure 3.1 Perchlorate concentrations and flow rate data for the packed bed reactor

AERATOR AND ANTHRACITE FILTER OPERATION

One focus of the pilot plant study was to demonstrate that water could be produced with a

turbidity of less than 0.3 NTU. Figures 3.2a and 3.2b show influent and effluent turbidity of the

anthracite filter and differential pressure across the filter. The effluent turbidity was variable

during startup and visual observation of the anthracite filter indicated that bacterial growth in the

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80 90 100

Time (days)

Perc

hlor

ate

(µg/

L) .

0

1

2

3

4

5

6

Flow

(gal

/min

) .

InfluentEffluentEffluent at MDLFlow Rate


15

filter was excessive and difficult to manage. Various air scouring and backwashing procedures

did not appear to solve this problem.

Figure 3.2a Effects of Rauschert medium and ferric chloride in aerator on effluent turbidity and

headloss in the anthracite filter

To improve performance of the filter for turbidity removal, the aerator was converted into

an attached growth aerobic bioreactor by addition of about 1 ft3 of Rauschert Bioflow 9 medium

on Day 37. The hypothesis was that the Rauschert medium would provide increased surface area

for microbial attachment and growth and excess acetic acid and nutrients in the packed bed

reactor would be removed in the aerator/aerobic bioreactor rather than in the anthracite filter.

Figure 3.2a shows the differential pressure, or headloss, across the anthracite filter media

following this modification. The headloss decreased with the new media; however, the filter

continued to fail the turbidity removal objective as shown in Figures 3.2a and 3.2b.

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100

Time (days)

Turb

idity

(NTU

) .

0

10

20

30

40

50

60

Filte

r Hea

dlos

s (in

ches

) .

Effluent TurbidityHeadloss

Rauschert Added

Ferric Chloride Added

Regulatory Limit 0.3 NTU


16

On Day 57, 2 mg-Fe/L of ferric chloride was added continuously to the aerator as a

coagulant. This modification resulted in increased turbidity removal and effluent turbidity less

than 0.3 NTU for the remainder of the pilot test [Days 58 to 92] as shown in Figure 3.2b. Thus,

it was concluded that the process required the use of an aerobic biological treatment to the

anthracite filter plus the use of a flocculant. A simple aeration step prior to the anthracite filter

was not effective. The aerobic biological treatment step during this pilot test involved the use of

a sparge vessel containing Rauschert Bioflow 9 medium. Other aerobic bioreactor

configurations would likely serve the same purpose of reducing the acetic acid concentration

prior to anthracite filtration. The ferric chloride flocculant was critical and resulted in the

anthracite filter being able to reduce the turbidity to less than 0.3 NTU to be effectively air

scoured and backwashed.

Figure 3.2b Effects of Rauschert medium and ferric chloride in aerator on effluent turbidity and

turbidity removal by the anthracite filter

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50 60 70 80 90 100

Time (days)

Turb

idity

(NTU

) .

0

10

20

30

40

50

60

70

80

90

100

Turb

idity

Rem

oval

(%)

.

Effluent Turbidity

Turbidity Removal

Rauschert Added

Ferric Chloride Added

Regulatory Limit0.3 NTU


17

STEADY STATE PILOT PLANT OPERATION

Table 3.1 presents pilot plant design and operating parameters that were selected based

on results of earlier testing and the first 62 days of testing described in this report.

Table 3.1

Final steady state operating conditions

Parameter Units Value

PBR flow rate gal/min 1.5

PBR bed height inches 48

PBR face velocity gal/min/ft2 0.75

PBR empty bed contact time min 40

Aerator residence time min 30

Aerator air flow rate scfm 3.5

Aerator Rauschert medium loading ft3 bulk media/ft3

water

0.2

Ferric chloride concentration mg-Fe/L 2

Filter flow rate gal/min 1.2

Filter face velocity gal/min/ft2 0.6

Filter bed depth inches 32

Steady state operation was defined as stable perchlorate, acetate, nutrient, and turbidity

removal and was observed for the ten-day period from Days 83 through Day 92. Table 3.2

summarizes the analytical results for data and samples collected from the steady state operational

period. These data indicate that the packed bed reactor was capable of consistent perchlorate and

nitrate removal and the downstream processing operations were capable of consistent acetate,

organic carbon, nutrient, and turbidity removal sufficient to meet SDWA regulatory limits and

engineering standards.

Table 3.3 and Figure 3.3 summarize the steady state air scour and back wash operational

results. In addition, Table 3.3 presents statistics on all air scour and backwash events conducted

during the pilot test. These data indicate that the packed bed reactor can be operated steadily if


18

air scoured and backwashed at least once per week. The anthracite filter needs to be cleaned

with an air scour and backwash at least twice per week and based on increasing differential

pressures observed at the end of the test (see Figure 3.3). Further optimization of the air scour

and backwash procedures appears to be warranted.

Table 3.2

Average steady state performance results for Days 83 through 92

Sample port location

Parameter

Units

A (Raw water)

B (Reactor

inlet)

C (Reactor outlet)

D (Filter inlet)

E (Filter outlet)

Goal Perchlorate µg/L 53.5

(3.8) 54.0 (4.2)

3.3 (1.4)

3.3 (1.4)

3.3 (1.4)

<4

Nitrate mg-N/L NA 3.5 (0.0)

0.0 (0.0)

NA NA <10

Nitrite mg-N/L 0.0 (0.0)

0.006 (0.017)

0.0 (0.0)

0.006 (0.017)

0.0 (0.0)

<1

Dissolved oxygen

mg/L NA 8.0 (0.7)

1.0 (0.0)

7.0 (0.0)

2.2 (0.8)

NA

Ammonia mg-N/L 0.10 (0.00)

1.44 (0.53)

0.39 (0.38)

0.19 (0.16)

0.16 (0.19)

<0.2

Phosphate mg/L 1.4 (0.2)

3.5 (0.5)

3.6 (0.5)

3.1 (0.4)

3.0 (0.4)

NA

Acetate mg/L 3.7 (0.4)

37.9 (7.7)

15.7 (7.3)

6.0 (2.0)

4.5 (1.3)

<5

Total organic carbon

mg/L 0.5 (0.2)

17.4 (2.5)

5.4 (2.5)

2.3 (1.1)

0.9 (0.4)

<2

Dissolved organic carbon

mg/L 0.6 (0.26)

17.7 (3.6)

6.7 (3.2)

2.0 (0.8)

0.9 (0.4)

<2

Turbidity NTU NA NA NA 1.04 (0.26)

0.18 (0.07)

<0.3

UV absorbance - 0.065 (0.048)

0.072 (0.051)

0.058 (0.076)

0.060 (0.067)

0.040 (0.053)

Low

pH - NA 6.8 (0.2)

7.0 (0.2)

7.6 (0.3)

7.6 (0.1)

6.5 – 8.5

Notes 1. See Figure 2.3 for sample port locations. 2. Data shown are averages with standard deviations in parentheses. 3. Perchlorate detection limit varied from 1.8 to 5.4 µg/L. 4. NA – Not analyzed or not applicable. 5. Detection of acetate at Port A is considered to be an analytical interference but is nevertheless

reported here.


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Table 3.3

Air scour and backwash performance

Parameter Units Perchlorate bioreactor Anthracite filter

Minimum time between

backwash/air scour

days 4 2

Maximum time between

backwash/air scour

days 9 9

Average time between

backwash/air scour

days 6.3 (2.0) 4.7 (2.4)

Steady state headloss inches 23 (12) 24 (16)

Steady state headloss

accumulation rate

inches/day 6.0 (3.9) 8.8 (4.2)

Notes 1. Standard deviations are shown in parentheses 2. Minimum, maximum, and average data are based on all air scour and backwash events 3. Steady state operation data were collected from Day 83 through 92 and are based on the last 3

air scour/backwash events

The results from this project phase indicate that fixed film biological processes can be

used to remove perchlorate and address concerns about the use of the final product as a drinking

water source. The process, albeit more complex than most drinking water treatment processes,

can be designed to meet industry standards for overall performance and reliability. This pilot-

plant testing period, however, could not be extended to address long-term operation because of

budget and schedule constraints. Nevertheless, previous work showed that stable perchlorate

removal for extended periods of time was possible. Additionally, the downstream filtration

process tested here is standard in the drinking water industry and is known to be reliable. If, at a

later date, more operational information is needed, the pilot equipment can be readily mobilized

and upgraded.


20

0

10

20

30

40

50

60

76 78 80 82 84 86 88 90 92 94

Time (days)

Filte

r Hea

dlos

s (in

ches

) .

Packed BedReactorAnthraciteFilter

Backwash

Figure 3.3 Steady state differential pressure accumulation in the packed bed reactor and

anthracite filter


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CHAPTER 4

CONCLUSIONS

The following conclusions were made based on the results of this supplemental testing:

• Complete removal of perchlorate from Redlands water was achieved in the packed bed

reactor with using 195-ft2/ft3 (Rauschert Bioflow 9) plastic medium with an empty bed

contact time of 40 minutes. Further optimization of the feeding and backwashing

processes may reduce the necessary empty bed contact time to 30 minutes.

• Shutdown of the packed bed reactor for two weeks due to groundwater extraction

equipment failure did not adversely affect packed bed reactor operation. Complete

dissolved oxygen and nitrate removal was observed 2 days following restart (first

sampling event). High perchlorate removal (81 percent) was observed 6 days (first

sampling event) following restart and complete perchlorate removal was observed 7

days following restart.

• An influent acetate concentration of 38 mg/L was more than sufficient for complete

perchlorate removal and resulted in 16 mg/L acetate in the packed bed reactor effluent.

The acetate influent concentration should be further reduced to improve the efficiency

of the process and make downstream processing requirements easier. However, even

at this high effluent concentration water with a turbidity of less than 0.3 NTU was

achieved.

• An aerobic biotreatment process is required between the packed bed reactor and the

anthracite filter to remove excess acetate and provide acceptable performance of the

anthracite filter. This aerobic treatment process was accomplished using an aeration

basin containing Rauschert Bioflow 9 medium.

• Addition of 2 mg-Fe/L of ferric chloride in the aerator plus use of a 32-inch bed of 1-

mm anthracite was capable of turbidity removal to less than 0.3 NTU.


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• Air scouring and backwashing of the packed bed reactor at least weekly and of the

anthracite filter at least twice weekly appears to be sufficient for stable operation.

• Steady-state operation of an anaerobic biological packed bed reactor in combination

with a downstream aerobic bioreactor-anthracite filter combination was capable of

successfully treating Redlands groundwater to remove perchlorate to less than

analytical detection limits and meet SDWA regulatory limits and engineering

standards.


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APPENDIX

CALIFORNIA DHS CONDITIONAL ACCEPTANCE OF BIOLOGICAL TREATMENT


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REFERENCES

AwwaRF (American Water Works Association Research Foundation). 2004. Final Report on

Bioreactor Systems for Treating Perchlorate-Contaminated Water. Phase I and II

Results. AwwaRF, Denver, Colorado.

APHA, Awwa, and WEF (American Public Health Association, American Water Works

Association, and Water Environment Federation). 1998. Standard Methods for the

Examination of Water and Wastewater. 19th ed. Washington, D.C.

Evans, P., A. Chu, S. Liao, S. Price, M. Moody, D. Headrick, B. Min, and B. Logan. 2002. Pilot

Testing of a Bioreactor for Perchlorate-Contaminated Groundwater Treatment. In:

Remediation of Chlorinated and Recalcitrant Compounds – 2002. Edited by A.R.

Gavaskar and A.S.C. Chen. Columbus, Ohio: Battelle Press. Electronic Paper 2H-03.

Min, B., P. J. Evans, A. K. Chu, and B. E. Logan. 2004. Perchlorate Removal in Sand and Plastic

Media Bioreactors. Water Res.38:47-60.


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ABBREVIATIONS

cfm cubic feet per minute DHS California Department of Health Services ft foot ft2 square foot ft3 cubic foot g gram GAC granular activated carbon gal gallon gal/min gallon per minute g/L gram per liter MDL minimum detection limit mg milligram mgd million gallons per day mg-Fe/L milligrams iron per liter mg/L milligrams per liter mg-N/L milligrams nitrogen per liter min minute mL milliliter mm millimeter µg microgram µg/L micrograms per liter NA Not analyzed or not applicable

NTU nephalometric turbidity units

PBR packed bed reactor

SDWA Safe Drinking Water Act

US EPA United States Environmental Protection Agency

UV ultraviolet


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