EPA910-R-07-002
&EFA
United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue
Seattle WA 98101
Alaska
Idaho
Oregon
Washington
Office of Water and Watersheds
April 2007
Advanced Wastewater
Treatment to Achieve Low
Concentration of Phosphorus
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Acknowledgements
EPA is very grateful to the operators and managers of the wastewater treatment plants included
in this evaluation. Without their time and assistance this project would not have been possible.
A special thank you goes to Magali Prevost who donated her time to help EPA Region 10 staff
conduct the evaluation and complete this report. EPA also expresses appreciation to the
following individuals who assisted by providing facility information or review of the project
report:
Dave Pincumbe, EPA-Region I
Ken Merrill, Washington Department of Ecology
Laurie Mann, EPA-Region 10
Ken Kosinski and Robert Wither, New York Department of Environmental Conservation
Jon Gasik and Tim McFetridge, Oregon Department of Environment Quality
Dr. Remy Newcome, University of Idaho, Moscow and Bluewater Technologies Inc.
Bonnie Beavers, Center for Justice
Kathleen Suozzo, Delaware Engineering
Project Manager And Report Writer
David Ragsdale, Engineer
EPA Region 10, Office of Water & Watersheds
Web Posting
Jeff Philip, Webmaster
EPA, Region 10
Cover Page
Christopher Moffett, Graphic Designer
EPA Region 10
Photos
All photos by report writer unless otherwise noted
For Additional Information About This Report:
David Ragsdale, Engineer
EPA Region 10, Office of Water & Watersheds
(360)407-6589
Email: ragsdale.dave@epa.gov
-2-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Abstract
In this report, EPA Region 10 presents observations of advanced wastewater treatment installed
at 23 municipalities in the United States. These facilities employ chemical addition and a range
of filtration technologies which have proven to be very effective at producing an effluent
containing low levels of phosphorus.
Observations from this evaluation include:
Chemical addition to wastewater with aluminum- or iron-based coagulants followed by
tertiary filtration can reduce total phosphorus concentrations in the final effluent to very low
levels. The total phosphorus concentrations achieved by some of these WWTPs are consistently
near or below 0.01 mg/1.
The cost of applying tertiary treatment for phosphorus removal is affordable, when
measured by the monthly residential sewer fees charged by the municipalities that operate these
exemplary facilities. The monthly residential sewer rates charged to maintain and operate the
entire treatment facility ranged from as low as $18 to the highest fee of $46.
There appeared to be no technical or economic reason that precludes other dischargers
from using any of the tertiary treatment technologies that are employed at these WWTPs. Any
of these technologies may be scaled as necessary to fulfill treatment capacity needs after
consideration of site specific conditions.
Other pollutants that commonly affect water quality such as biochemical oxygen demand,
total suspended solids, and fecal coliform bacteria are also significantly reduced through these
advanced treatment processes.
WWTPs which utilize enhanced biological nutrient removal (EBNR) in the secondary
treatment process can often reduce total phosphorus concentrations to 0.3 mg/1 or less prior to
tertiary filtration. While employing EBNR is not essential to achieving high phosphorus removal
rates, EBNR enhances the performance and reduces operating costs (especially chemical use) of
the subsequent tertiary filtration process. Recently published studies report that the longer solids
retention times used in BNR processes also removes a significant amount of other pollutants
contained in municipal wastewater, including toxics, pharmaceuticals, and personal care
products.
The low effluent turbidity produced by tertiary filtration allows for efficient disinfection of
final effluent without chlorination through the use of ultraviolet treatment.
The treatment processes and quality of the final effluent produced by tertiary filtration for
phosphorus removal typically meet state criteria for wastewater reclamation. Reuse of this high
quality effluent can be an attractive alternative to direct discharge into surface waters in
situations where restrictive NPDES permit limitations apply.
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Table of Contents
Acknowledgements 2
Abstract 3
Nutrients and Water Quality Problems 5
Evaluation considerations 6
Summary of Observations 6
City of Aurora, Sand Creek Wastewater Reuse Plant 11
Breckenridge Sanitation District, Iowa Hill Wastewater Reclamation Plant 13
Breckenridge Sanitation District, Farmers Korner Wastewater Treatment Plant 17
Snake River Wastewater Treatment Plant 19
Pinery Wastewater Reclamation Facility 22
Clean Water Services, Rock Creek Advanced Wastewater Treatment Plant 26
Clean Water Services, Durham Advanced Wastewater Treatment Plant 30
Stamford Wastewater Treatment Plant 34
Walton Wastewater Treatment Plant 39
Milford Wastewater Treatment Plant 44
Alexandria Sanitation Authority (ASA) Advanced Wastewater Treatment Plant 47
Upper Occoquan Sewage Authority (UOSA) 51
Fairfax County Wastewater Management, Noman M. Cole Jr. Pollution Control Plant 57
Blue Water Technologies, Inc - Pilot facility at the Hay den Wastewater Treatment Plant 62
CoMag Technology - Pilot testing at the Concord Wastewater Treatment Plant 66
LOTT Budd Inlet Wastewater Treatment Plant 69
-4-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Nutrients and Water Quality Problems
Phosphorus and nitrogen are nutrients that are essential for aquatic plant and algae growth. Most
waters naturally contain enough of these nutrients to support native aquatic life. However, an
over-abundance of these nutrients can over-stimulate plant and algae growth such that they
create water quality problems. Over 1,000 waterbodies in Idaho, Oregon and Washington are
identified as being impaired due to excessive nutrient loading and are included on state Clean
Water Act 2004 §303(d) lists for water quality problems. The problems caused by nutrient
enrichment of lakes, stream, and rivers are not unique to the Northwest states as many other
waterbodies across the United States have also been identified as impaired by nutrients. Nutrient
impairments affect the survival of many aquatic species such as salmon; affect the safety of
drinking water supplies; affect the aesthetics of recreational areas, and the ability to navigate
through rivers and lakes.
In freshwater systems, phosphorus is typically the nutrient that is in short supply relative to
biological needs, which means that the productivity of aquatic plans and algae can be controlled
by limiting the amount of phosphorus entering the water. Many streams and lakes in the
Northwest are documented to have very little capacity to assimilate phosphorus loading during
the "critical" warm and dry summer period without significant water quality degradation. Large
diurnal swings in pH and dissolved oxygen may occur as excessive amounts of nutrients are
metabolized by aquatic plants and algae. The range of these swings is often measured to exceed
the state water quality criteria established to protect fish and other aquatic organisms in their
various life stages. Therefore, the amount of phosphorus currently entering these waters exceeds
the seasonal loading capacity and must be reduced if these water quality problems are to be
resolved.
The sources of phosphorus loading vary depending on the human activities and conditions in a
specific watershed. In the Northwest, phosphorus loading into streams and lakes from nonpoint
sources (e.g. agriculture, pet waste) is often minimal during the summer months because there is
typically very little rainfall runoff to flush pollutants into receiving waters. The discharges of
treated wastewater can be the most significant source of phosphorus loading during these critical
summer months. To address these water quality problems, state environmental agencies and the
Environmental Protection Agency (EPA) are requiring dischargers to reduce the amount of
phosphorus in their effluent.
Achieving very low phosphorus levels in treated wastewater will require the installation of
additional treatment. A number of water quality studies in Northwest states have determined
waste load allocations which will require dischargers to achieve total phosphorus effluent
concentrations that range from as low as 0.009 to 0.05 mg/1. Even as WWTP operators in the
Northwest consider installing additional treatments to address water quality problem, they are
also planning to upgrade capacity of their plants to accommodate rapid population growth. With
many other interests competing for limited public and private resources, resolving water quality
problems is often contentious and slow. Implementation of water quality improvement plans
(called Total Maximum Daily Loads (TMDLs)) have been significantly delayed by arguments
about the availability and cost of treatment technologies capable of achieving very low
phosphorus targets.
-5-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
In response to these discussions, EPA - Region 10 initiated a project to evaluate municipal
wastewater treatment plants which have demonstrated exemplary phosphorus removal through
their treatment processes. The primary goal of this project was to obtain and share information
about the technology, performance and costs of applying advanced wastewater treatment for
phosphorus removal.
Evaluation Considerations
The WWTPs included in this project were selected because monitoring results have
demonstrated their treatment to be very effective at removing phosphorus. The reported
performance at each of these facilities has been well documented by monitoring conducted over
periods of several years. EPA attempted to include a variety of treatment technologies and
facilities of different sizes in this evaluation. However, not all facilities that achieve exemplary
phosphorus removal nor all filtration technologies could be presented in this report. A number of
the WWTPs that are currently achieving good phosphorus removal are planning treatment
upgrades that will allow them to also meet a total nitrogen limitation of 3 mg/1. Some
information about treatment to remove nitrogen is presented in the description of the LOTT,
Budd Inlet WWTP.
Treatment performance is characterized by discharge monitoring information required by the
National Pollutant Discharge Elimination System (NPDES) permits which authorize these
facilities to discharge treated wastewater. Monitoring of the final effluent per NPDES permit
requirements is conducted and reported in accordance with EPA approved analytical methods
and quality control procedures. This monitoring information provides the best readily available
information with which to characterize WWTP performance. EPA presents the average and
range of reported monthly average phosphorus concentrations to indicate long term treatment
performance. These monthly average values may not be representative of daily fluctuations in
effluent quality experience by these WWTPs. Effluent concentrations are sometimes reported as
zero or less-than values on discharge monitoring reports when the monitored concentrations are
well below permit limitations or laboratory reporting limits for phosphorus. The actual effluent
phosphorus concentration in the final effluent of these facilities may be significantly better than
characterized in discharge monitoring reports.
Although each of the WWTPs are very well maintained and operated, very few are being pressed
by stringent NPDES limitations to optimize treatment to achieve the best phosphorus removal
possible. The table under Summary of Observations lists the applicable NPDES permit
phosphorus limitations for each of the facilities evaluated. The lowest phosphorus limitation
established for any of these WWTPs was a monthly average limitation of 0.05 mg/1. Operators
at many of these WWTPs conveyed that if necessary, even better phosphorus removal
performance could be achieved through operational changes to the existing treatment system.
This is a consideration that should not be overlooked by dischargers, consultants and regulators
as they consider treatment options.
Summary of Observations
Information about treatment technology, performance and residential sewer treatment fees for
each of the 23 WWTPs evaluated is summarized in the following table.
-6-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Facility Name
and Location
Sand Creek WWRP
Aurora, CO
Breckenridge S.D.,
Iowa Hill WWRP,
CO
Breckenridge S.D.,
Farmers Korner
WWTP, CO
Summit County
Snake River WWTP,
CO
Pinery WWRF
Parker, CO
Clean Water Services,
Rock Creek WWTP,
OR
Clean Water Services,
Durham WWTP, OR
Stamford WWTP
Stamford, NY
Walton WWTP
Walton, NY
Milford WWTP
Milford, MA
Alexandria Sanitation
Authority AWWTP,
Alexandria, VA
Upper Occoquan
Sewerage Authority
WWTP, VA
Fairfax County,
Noman Cole WWTP,
VA
NPDES
Permit
Number
CO0026611
CO0045420
CO0021539
CO0029955
CO0041092
OR0029777
OR0028118
NY0021555
NY0027154
MAO 100579
VA0025160
VA0024988
VA0025364
Capacity
5 mgd
1.5 mgd
3 mgd
2.6 mgd
2 mgd
39 mgd
24 mgd
0.5 mgd
1.55 mgd
4.8 mgd
54 mgd
42 mgd
67 mgd
Advanced Phosphorus
Treatment Technology
BNR,filtration
BNR, chemical addition,
tertiary settlers and filtration
BNR, chemical addition,
tertiary settlers and filtration
BNR, chemical addition,
tertiary settlers and filtration
BNR, chemical addition, two-
stage filtration
Chemical addition, filtration
BNR, chemical addition,
filtration
Chemical addition, two-stage
filtration
Chemical addition, two-stage
filtration
Multi-point chemical addition,
filtration
BNR, Multi-point chemical
addition, tertiary settling and
filtration
Chemical (high lime) and
tertiary filtration
BNR, chemical addition,
tertiary clarification and
filtration
NPDES Permit
Limitation for
Phosphorus
None
0.5 mg/1 daily max
& 225 Ibs/year
0.5 mg/1 daily max
& 225 Ibs/year
0.5 mg/1 daily max
& 340 Ibs/year
0.05 mg/1 & 304
Ibs/year
0. 1 mg/1 (monthly
median limitation)
0.11 mg/1
(monthly median
limitation)
0.2 mg/1
0.2 mg/1
0.2 mg/1
0.18 mg/1
0.10 mg/1
0.18 mg/1
*Average
Effluent
Phosphorus
Concentration
0.1 to 0.2 mg/1
0.055 mg/1
0.007 mg/1
0.015 mg/1
0.029 mg/1
0.07 mg/1
0.07 mg/1
0.011 mg/1
O.01 mg/1
0.07 mg/1
0.065 mg/1
O.088 mg/1
O.061 mg/1
Range of Monthly
Average
Phosphorus
Concentrations
N/A
0.017 to 0.13 mg/1
0.002 to 0.036 mg/1
O.01 to 0.04 mg/1
0.021 to 0.074 mg/1
0.04 to 0.09 mg/1
0.05 to 0.1 mg/1
O.005 to < 0.06
mg/1
O.005 to <0.06 mg/1
0.04 to 0.16 mg/1
0.04 to 0.1 mg/1
0.023 to O.282 mg/1
<0.02to<0.13mg/l
Monthly
Residential
Sewer Rate
$2.38 + $4.50 /
1,000 gal used
$19
$19
$36
$18
$16.07 +
$l.ll/ccf
$16.07 +
$l.ll/ccf
$10**
$10**
$27.50
$4.17 + $4.49 /
1,000 gal used
$3.03 to
$4.09/1,000 g
$3.28/1,000 g
-7-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Facility Name
and Location
BluePro Treatment
Pilot results at
HaydenWWTP, ID
CoMag Treatment
Pilot results at
Concord WWTP, MA
NPDES
Permit
Number
N/A
N/A
Capacity
N/A
N/A
Advanced Phosphorus
Treatment Technology
Iron coated sand in two-stage
Centra-Flo Filters.
Chemical addition, ballast
sedimentation, magnetic
polishing
NPDES Permit
Limitation for
Phosphorus
N/A
N/A
*Average
Effluent
Phosphorus
Concentration
0.013 mg/1
0.04 mg/1
Range of Monthly
Average
Phosphorus
Concentrations
N/A
N/A
Monthly
Residential
Sewer Rate
N/A
N/A
WWTPs not visited for this evaluation :
Delhi, NY
Pine Hill WWTP, NY
NYC DEP-Grand
Gorge STP, NY
Hobart-VPCF, NY
Snyderville Basin
Water Reclaimation
District, UT
Ashland WWTP
Ashland, OR
McMinneville
WWTP
McMinneville, OR
Facility Name
and Location
LOTT WWTP
Olympia, WA
NY0020265
NY0026557
NY0026565
NY0029254
UT0020001
OR0026255
OR0034002
NPDES
Permit
Number
WA0037061
0.82 mgd
0.5 mgd
0.5 mgd
0.18 mgd
4 mgd
2.3 mgd
ADWF
5.6 mgd
ADWF
Capacity
28 mgd
Activated sludge, chemical
addition, filtration
RBC, sand filters, chemical
addition, microfiltration
RBC, sand filters, chemical
addition, microfiltration
Activated sludge, sand filters,
chemical addition,
microfiltration
BNR, chemical addition,
filtration
Oxidation Ditch, chemical
addition, membrane filtration
Oxidation Ditch (BNR),
Chemical addition, multi-media
traveling bed filtration
Advanced Nitrogen
Treatment Technology
Biological Nutrient Removal
O.llmg/1
0.2 mg/1
0.2 mg/1
0.5 mg/1
0.1 mg/1
1.6 Ib/day
(= 0.083 mg/1)
0.07 mg/1
NPDES Permit
Limitation for
Total Inorganic
Nitrogen (TIN)
3 mg/1
0.04 mg/1
0.06 mg/1
< 0.04 mg/1
< 0.05 mg/1
0.04 mg/1
0.07 mg/1
0.058 mg/1
*Average
Effluent TIN
Concentration
2.2 mg/1
O.02 to 0.085 mg/1
0 to 0.12 mg/1
0 to 0.05 mg/1
0.026 to 0.07 mg/1
0.03 to 0.06 mg/1
0.05 to 0.12 mg/1
0.036 to 0.092 mg/1
Range of Monthly
Average TIN
Concentrations
1.23 to 2.81 mg/1
$10**
$10**
$10**
$10**
$30
$11.55 + $1.73
per 100 cf used
$46.15 (average
based on 700 cf
used)
Monthly
Residential
Sewer Rate
$25.50
* This is the average of monthly average measurements achieved as reported by the facility on NPDES discharge monitoring reports. The period for which these
averages were determined is identified in the discussion about each facility. Many facilities have seasonal water quality-based limitations for phosphorus.
** The costs of construction, operation and maintenance of WWTPs discharging into the Delaware River watershed are partially subsidized by the City of New York.
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Summary of Observations (continued)
Tertiary filtration aided by chemical addition can reduce total phosphorus concentrations in
the final effluent to very low levels. This treatment is employed at all but one of the
WWTPs included in this evaluation. To achieve very low phosphorus concentrations,
chemicals must be added to wastewater to associate phosphorus with solids that can then be
successfully removed through filtration. Aluminum- or iron-based coagulants and polymer
are the chemicals most commonly used for this purpose.
Traveling sand bed filters, mixed- media gravity filters, Dynasand filters and variations of
these filtration technologies are used by all of the WWTPs evaluated. Filtration has been
employed for many years to treat drinking water and more recently applied to treat
wastewater. Filtration technologies for treating wastewater are rapidly evolving as water
quality agencies and dischargers strive to protect sensitive receiving waters from potential
impacts of pollutants in the treated effluent. With proper design, there are no apparent
reasons why any of these filtration technologies may not be installed in either small or large
scale applications. Selection of a filtration technology includes the usual considerations
such as: desired effluent quality; reliability of treatment equipment; capital, operating and
maintenance costs; equipment footprint, and future expandability.
Application of two-stage filtration processes produced the lowest phosphorus levels
observed in this evaluation. Two-stage treatment may be achieved through use of a first
and second stage filter or by providing tertiary clarification prior to filtration. The Walton
and Stamford WWTPs achieved the lowest measured phosphorus concentration in their
effluent (about 0.01 mg/1 or less) by utilizing two-stage Dynasand filters from Parkson
Corporation. Excellent treatment results were also obtained by Breckenridge WWTPs,
the Snake River WWTP and the Alexandria AWWTP using a two-stage treatment process
consisting of chemical addition with tertiary settling in advance of their sand bed filters.
Modular two-stage filters from US Filter Corporation installed at the Pinery WWTP
employs a synthetic media in the first stage and sand media in the second stage. The
Fairfax County, Noman Cole WWTP utilizes large tertiary clarifiers followed by filtration
through sand beds.
Table 1 identifies which of the WWTPs include in this evaluation have also incorporated
enhanced biological nutrient removal (EBNR) into their secondary treatment processes to
remove phosphorus. An EBNR treatment system promotes the production of phosphorus
accumulating organisms which utilize more phosphorus in their metabolic processes than a
conventional secondary biological treatment process. The average total phosphorus
concentrations in raw domestic wastewater is usually between 6 to 8 mg/1 and the total
phosphorus concentration in municipal wastewater after conventional secondary treatment
is routinely reduced to 3 or 4 mg/1. Whereas, EBNR incorporated into the secondary
treatment system can often reduce total phosphorus concentrations to 0.3 mg/1 and less.
Facilities using EBNR significantly reduced the amount of phosphorus to be removed
through the subsequent chemical addition and tertiary filtration process. This improves the
efficiency of the tertiary process and can significantly reduce the costs of chemicals used to
remove phosphorus. Staff at the Fairfax County WWTPs reported that their chemical
dosing was cut in half after EBNR was installed to remove phosphorus.
-9-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
The treatment provided by these WWTP also removes other pollutants which commonly
affect water quality to very low levels. Biochemical oxygen demand (BOD) and total
suspended solids are routinely less than 2 mg/1 and fecal coliform bacteria less than 10
feu/100 ml. Turbidity of the final effluent is very low which allows for effective
disinfection using ultraviolet light, rather than chlorination. Recent studies report finding
that WWTPs using EBNR also significantly reduce the amount of pharmaceuticals and
health care products from municipal wastewater, as compared to the removal accomplished
by conventional secondary treatment.
Only four of the WWTPs included in this evaluation utilize anaerobic digesters to stabilize
removed solids. Facilities which utilize anaerobic digesters need to consider the potential
that a significant phosphorus load might be released from the removed solids and thereafter
returned to the wastewater being treated. The Clean Water Services WWTPs manages the
phosphorus loading associated with the use of anaerobic digesters by equalizing the flow of
these return streams (supernatant and centrate) over time. Other studies indicate that
phosphorus removed with alum does not resolubilize in anaerobic digesters, whereas
phosphorus removed with iron salts may solubilize in the absence of adequate iron.
Operators have identified the amount of alum or iron necessary to control resolubilization
of phosphorus in anaerobic digesters to be a cost consideration.
Applying advanced water treatment to remove phosphorus is affordable for most
municipalities as demonstrated by the monthly residential sewer fees charged by the
WWTPs included in this evaluation. These fees are listed in the Summary of Observations
Table and are typically less than $30. EPA intended to identify in more detail the costs
incurred by these WWTPs to install and operate tertiary treatment for phosphorus removal.
However, it was soon determined that separating the costs of the tertiary treatment from
overall facility operating costs was beyond the resources and time available to complete
this project. EPA instead presents the monthly residential sewer fees charged by each of
these WWTPs as an indicator of the costs to construct, maintain and operate these facilities,
including the tertiary treatment for phosphorus removal.
-10-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
City of Aurora - Sand Creek Wastewater Reuse Plant
Contact Information:
Mailing address:
18301 EAST QUINCY AVENUE
Aurora, Colorado 80010
303-326-8807
NPDES permit No. CO0026611, expiration date December 31, 2002
Receiving water: Sand Creek or reclaimed for irrigation use
Sand Creek WWRP Treatment:
Raw Primary Biological Secondary Effluent Filtration UV
Wastewater -> Clarification -> Nutrient -> Clarification -> (Parkson Dynasand -> Disinfection
Removal Filters)
Treatment capacity: 5 mgd average daily flow
Aurora WWRP Performance Information:
Parameter
TSS
N-NH3
BOD
Phosphorus
Limitation
30/45 mg/1
None
30/45 mg/1
none
Avgof
monthly
averages
1.0 mg/1
*<0.14mg/l
* <2.3 mg/1
Range of monthly
averages
0.5 to 1.84 (6/04)
*<0.1to<0.33mg/l
<2.2 to <4.0 mg/1
**0.1to0.2mg/l
Maximum
individual
measurement
7.0 mg/1
1.7 mg/1
6.1 mg/1 (6/05)
Reporting
period
4/01 to 5/06
8/03 to 5/06
4/01 to 5/06
4/01 to 5/06
* Most of these measurements were reported as less than (<) values
Monthly Sewage Service Charge: $2.16 plus a usage fee of $1.99 per 1,000 Gallons water
used.
Facility description:
The City of Aurora is east of the City of Denver in Colorado. This facility began operation in
2001 and either discharges treated effluent to Sand Creek or the wastewater is reused for
irrigation on public lands, such as parks and golf courses. Some of the irrigation sites are as far
as 17 miles away from the WWTP. Although this is a long distance to pump water, the high
demand for the water in this arid area causes the value of reclaimed wastewater to be nearly the
price of potable water!
Treatment at this WWTP involves screening and grinding; primary clarification; biological
nutrient removal (BNR) in the contact basins; secondary clarification; filtration through single
pass Dynasand filters (four cells with 4 filters per each cell); UV disinfection. Solids removed
-11-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
during the course of treatment are routed back into the sewer main where they are ultimately
treated at the Denver, Metro WWTP. BNR is accomplished by exposing wastewater through
sequential anoxic, anaerobic and aerobic zones maintained in the contact basins.
Direct discharge from this WWTP is into the Cherry Creek watershed. The Cherry Creek
watershed includes a reservoir that is currently impaired due to excessive loading of nutrients.
The Aurora WWTP currently does not have any effluent limitation for phosphorus. At the time
of this visit, the NPDES permit for this facility was expired and WWTP operators expected that
phosphorus limitations might be included in the proposed permit reissuance. Monitoring for
total phosphorus is conducted weekly and analyses achieve an analytic reporting level of 0.05
mg/1.
No chemicals are currently used at the plant to enhance phosphorus removal. Nevertheless, the
final effluent typically contains between only 0.1 to 0.2 mg/1 total phosphorus. Influent BOD
and ammonia nitrogen were reported to be approximately 200 to 300 mg/1 and 30 mg/1,
respectively. Effluent BOD concentrations average about 2.2 mg/1 and ammonia nitrogen is less
than 0.1 mg/1.
Operational considerations:
The single pass Dynasand filters used as tertiary treatment at the Aurora WWTP include
four cells, each with four continuous backwashing upflow sand media filters. The
surface area of each filter measures seven by seven feet and the filters are 16 feet deep.
Plant operators state they had encountered no serious maintenance or operational
problems with the DynaSand filters. WWTP operators also responded that they were
unaware of any reason why application of these filters could not be "scaled-up" to
accommodate a much larger treatment capacity than the 5 mgd currently being treated
through the Aurora facility. Additional filters will likely be added in the future to
accommodate increasing treatment capacity needs in the service area.
-12-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Breckenridge Sanitation District - Iowa Hill Wastewater Reclamation Plant
Contact Information:
District Office:
1605 Airport Road
Breckenridge, CO 80424
Phone: 970-453-2723
Fax: 970-453-2013
Mailing Address:
POBox 1216
Breckenridge, CO 80424
NPDES Permit No. CO0045420, expiration date 31 December 2004
Receiving water: Blue River (tributary to Dillon Reservoir)
Iowa Hill WWTP Performance Information:
Parameter
BOD
TSS
N-NH3
Phosphorus
NPDES
Limitation
30mg/l
30 mg/1
10 mg/1
0.5 mg/1 daily
max & 225
Ib/year
Avgof
monthly
averages
1.55 mg/1
2.07 mg/1
0.41 mg/1
0.55 mg/1
Range of
monthly
averages
0.64 to 3. 02 mg/1
0.49 to 6.2 mg/1
0.16 to 1.8 mg/1
0.017 to 0.13 mg/1
Maximum
individual
measurement
(date)
12.6 mg/1 (4/00)
18.1 mg/1 (4/00)
8.2 mg/1 (4/00)
0.13 mg/1 (6/00)
Reporting
period
4/00 to 12/02
4/00 to 12/02
4/00 to 12/02
5/00 to 12/02
Iowa Hill WWTP Process:
Influent-^ Screening-^ Activated-^ Biological -^ Chemical -^Mixing -> Filtration-^ Disinfection
(Scalping & Grit Sludge Aerated Addition & Settling (Parkson
Plant) Removal Biological Filter (Alum) (Densadeg) DynaSand
Treatment (IDI "BioFor") Filter)
Design Treatment Capacity: 1.5 MGD average dry weather flow
Monthly household sewer use fee: $19/month
-13-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
Facility description:
April 2007
The Breckenridge Sanitation District collects wastewater from the town of Breckenridge and the
surrounding area. The District operates three (3) wastewater treatment facilities including the
Iowa Hill WWTP and the Farmers Korner WWTP which were visited as part of this evaluation.
A small package plant is also operated by the district. The Iowa Hill WWTP was newly
constructed in 1999 and has since been widely cited for its quality of effluent, especially its low
effluent total phosphorus. Influent flow to the plant is "scalped" from the main District
interceptor in the Blue River Valley. Solids removed during treatment at the Iowa Hill WWTTP
are routed back into the interceptor for treatment at the Farmers Korner WWTP.
Discharge from both of these facilities enters Dillon reservoir which is used to supply drinking
water to the Metropolitan Denver area. To prevent eutrophication of Dillon reservoir, an annual
maximum mass loading limitation of 225 pounds per year and daily maximum concentration of
0.5 mg/1 for total phosphorus were established. Facility operators target achieving an effluent
concentration of 0.01 to 0.02 mg/1 total phosphorus to meet the annual loading limitation.
Treatment at this WWTP is accomplished by screening and grit removal in the headworks;
activated sludge biological treatment; biological aerated filter (IDI "BioFor" for nitrification);
chemical coagulation using alum; flocculation and clarification using tube settler (IDI
"Densadeg"); filtration (single stage Parkson "Dynasand" filters); disinfection and
dechlorination. The Dynasand filter reject rate is reported to be about 15 to 20%. The Dynasand
filters are configured in four, two-cell units for a total of 8 filters beds which are each 8 feet
deep.
-14-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Influent concentrations of total phosphorus were measured to be about 6 mg/1 during the time of
this visit (winter) which is very a typical value for untreated domestic wastewater. The aeration
basins are operated with an anoxic zone to provide for biological removal of phosphorus. About
sixty percent of the influent phosphorus was reported to be removed through the biological
treatment process.
Sodium sulfate is added to maintain alkalinity through the treatment process for phosphorus
removal. Approximately 100 to 120 mg/1 sodium sulfate is applied to the wastewater just
upstream of where alum is added. Alum is used to precipitate phosphorus. The alum dose at the
time of this visit was approximately 135 mg/1 and is used with 0.5 to 1.0 mg/1 cationic polymer.
Operational considerations:
The District representative indicated that construction to double the current 1.5 mgd
treatment capacity at this plant is being considered to accommodate growth in the service
area.
It was reported that the airlift tube in the Parkson (Dynasand) filters had to be replaced
because of wear caused by sand abrasion.
Backwashing of the BioFor unit and improved hydraulic controls in the Densadeg unit
presented some operational difficulties.
-15-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Fecal coliform levels in the final effluent are so low (0 to 10 colonies/100 ml) that they
typically meet permit limitations without disinfection. Accordingly, the use of chlorine
and sodium bisulfite (for dechlorination) are minimal.
Facility operators prefer the more conventional flocculation-clarification units with tube
settlers and bed filters that are installed at the Breckenridge Sanitation District, Farmers
Korner WWTP. The Farmers Corner WWTP effluent quality is reported to be as good as
that produced by the Iowa Hill WWTP with less operational attention.
-16-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Breckenridge Sanitation District - Farmers Korner Wastewater Treatment
Plant
Contact Information:
District Office:
1605 Airport Road
Breckenridge, CO 80424
Phone: 970-453-2723
Fax: 970-453-2013
Mailing Address:
PO Box 1216
Breckenridge, CO 80424
NPDES permit No. CO0021539 expiration date 31 July 2008
Receiving water: Blue River (tributary to Dillon Reservoir)
Design Treatment Capacity: 3.0 MGD average dry weather flow
Farmers Korner Treatment Processes:
Influent-^Screening-^Activated-^Secondary-^Chemical-^ Tertiary-^ Filtration-^ Disinfection
& Grit Sludge Clarification Addition Clarification
Removal (with BNR) (tube settlers)
Residential sewer use fee: $19/month
Farmers Korner WWTP Performance Information:
Parameter
BODS
TSS
NH3-N
Total
Phosphorus
NPDES
Limitation
30mg/l
30mg/l
10mg/l
225 Ib/yr &
0.5 mg/1 daily
max
Avgof
monthly
averages
1.0 mg/1
1.07 mg/1
3.36 mg/1
0.007 mg/1
Range of
monthly
averages
0.57 to 2.40 mg/1
0.3 to 3. 10 mg/1
0.31 to 16.66
mg/1
0.002 to 0.036
mg/1
Maximum
individual
measurement
5.78 (Dec 03)
5.2 (Dec 05)
2 1.88 (May 05)
0.06 (Dec 05)
Reporting
period
Aug 03 thru
Apr 06
Same
Same
Same
-17-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Facility Description:
The Breckenridge Sanitation District collects wastewater from the town of Breckenridge,
Colorado and the surrounding area. The District operates three wastewater treatment facilities
including the Iowa Hill and Farmers Korner WWTPs which were visited as part of this
evaluation. Facilities at the Farmers Korner WWTP were upgraded in 1999 to the present
treatment configuration. Influent flow to this plant includes municipal wastewater from the
service area and removed solids from the District's Iowa Hill WWTP.
Discharge from the Farmers Korner WWTP enters Dillon reservoir which is used to supply
drinking water to the Metropolitan Denver area. To prevent eutrophication of Dillon reservoir,
the NPDES permit established an annual maximum mass loading limitation of 225 pound/day
and a daily maximum concentration of 0.5 mg/1 for total phosphorus. Facility operators target
achieving an effluent concentration of 0.01 to 0.02 mg/1 total phosphorus to ensure meeting the
annual loading limitation.
Treatment at Farmer Korner WWTP consists of screening and grit removal; biological nutrient
removal; chemical coagulation and flocculation using polymer and alum; clarification via tube
settlers; filtration though mixed media bed filters; disinfection with chlorine and dechlorination
(using sodium bisulfite). Solids removed during treatment are routed to an aerated storage tank,
dewatered by centrifuge; and the solids utilized at a mine reclamation site. Caustic soda is added
to maintain alkalinity though the treatment process.
Operational Considerations:
Ten operators are employed to run the three Breckenridge District wastewater treatment
plants and also maintain 20 pump stations in the collection system.
Fecal coliform levels in the final effluent are so low (0 to 10 colonies/100 ml) that they
typically meet permit limitations without disinfection. Accordingly, the amount of
chemicals used for disinfection are minimal.
The alum dose applied at the time of this visit was approximately 135 mg/1 and is used
with 0.5 to 1.0 mg/1 cationic polymer.
-18-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Snake River Wastewater Treatment Plant
Contact information:
Summit County Board of Commissioners
Snake River Wastewater Treatment Plant
4344 Swan Mountain Road
Dillon, Colorado 80435-8474
970-468-5794
Chuck Clause, Utility Director
Stoner Turner, Chief Operator
NPDES Permit No. CO0029955, expiration date JanAN-31-2008
Receiving water: Dillon Reservoir
Snake River WWTP Process:
Influent -^Screening ->Aeration -> Secondary -> Chemical -^ Flocculation -^Clarification ->
Basins Clarifiers Coagulation
Disinfection
Snake River WWTP Performance Information:
Parameter
BOD
TSS
N-NH3
Phosphorus
NPDES
Limitation
30/45 mg/1
30/45 mg/1
5.8 mg/1
340 Ib/year total
& 0.5 mg/1 daily
max
Avgof
monthly
averages
0.7 mg/1
0.6 mg/1
0.25 mg/1
0.015 mg/1
Range of monthly
averages
0.3 to 2 mg/1
0.2 to 2 mg/1
O.Olto 1.82 mg/1
<0.01 to 0.04 mg/1
Maximum individual
measurement (date)
3 mg/1 (8/03)
4 mg/1 (8/04)
9.85 mg/1 (7/04)
0.08 (2/84)
Reporting
period
2/03 to 5/06
2/03 to 5/06
2/03 to 5/06
Design Treatment Capacity: 2.6 MOD
Residential sewer use fee: $36/month ($108 quarterly)
-19-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Facility Description:
The Snake River WWTP treats domestic wastewater collected from a service area that is south
and east of the Dillon Reservoir. Treated effluent is discharged into Dillon Reservoir which is
used as a drinking water supply for the Denver Metropolitan area. Water quality-based effluent
limitations for phosphorus have been established in the NPDES permit issued to this WWTP and
other dischargers into the reservoir to prevent eutrophication. Construction to upgrade treatment
and capacity of the plant was completed in 2002.
Treatment at the Snake River WWTP includes screening and grit removal; aeration basins;
secondary clarification; chemical coagulation and flocculation using with alum and polymer;
tertiary clarification (rectangular conventional with inclined plate settlers); mixed media bed
filters (5 feet deep); and disinfection (the filtration process removes enough fecal coliform so that
conventional disinfection is not normally required). The average alum dose is 70 mg/1 in the
wastewater and is reported to vary from 50 to 180 mg/1. A greater dose of alum is applied during
the winter period. The operator reported the polymer dose concentration to be about 0.1 mg/1.
Removed solids are routed to an aerobic digester from which waste solids are dewatered by
centrifuge and utilized for mine site reclamation.
-20-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Empty rectangular clarifier with inclined plate settlers at Snake River WWTP
Operational considerations:
Air supplied to the aerobic digesters is turned off for 2 hours three times a day to raise the
pH.
Recycle streams that are routed to the headworks make up about 40 percent of the total
plant flow, including grit screenings wash water, WAS thickener decant mixed-media
filter backwash waste water, aerobic digester decant and centrate.
Plant operators are very pleased with operation of the upgraded plant. Good phosphorus
removal is achieved through the aeration basins without EBPR. Total phosphorus
concentrations measured in the secondary effluent range from 0.5 to 3.0 mg/1. Facility
operators speculated the variability of phosphorus in the secondary effluent is possibly
because chemical sludge that is recycled to head of plant aids removal of phosphorus
through the biological process and secondary clarification. Return streams include WAS
thickener decant, aerobic digester decant and centrate.
Essentially complete nitrification of wastewater is achieved in the aeration basins.
The filtration process removes enough fecal coliform so that conventional disinfection is
not normally required.
-21-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Pinery Wastewater Reclamation Facility
Contact Information:
Pinery Water and Wastewater District
6516 North State Highway 83
Parker, Colorado 80134
Mailing address:
P.O. Box 1660
Parker, Colorado 80134
Telephone: 303-841-2797
NPDES Permit No. CO0041092, expiration date Sept 30, 2010
Receiving water: Groundwater in Cherry Creek Reservoir subbasin
Design Treatment Capacity: 2.0 MOD
Treatment Processes:
Influent -^Screening -> EBNR -^ Secondary -> Chemical -^Filtration -> UV
& Grit (BardenPho Clarification Addition "Memcor" Disinfection
Removal 5 stage)
Pinery WWTP Treatment Performance:
Parameter
BOD
TSS
Phosphorus
NPDES
Limitation
(monthly average)
30mg/l
30mg/l
0.05 mg/1 &
304 Ibs/year
Average of
monthly
averages
1.1 mg/1
2.2 mg/1
0.029 mg/1
Range of monthly
averages
0.36 to 5.2 mg/1
0.6 to 13.3 mg/1
0.021 to 0.074 mg/1
Maximum
measurement
(date)
6.4 mg/1 (8/05)
33.3 mg/1 (4/04)
0.234 mg/1 (11/05)
Reporting
period
1/03 to 9/05
1/03 to 9/05
1/03 to 9/05
Monthly residential sewer use fee: $18 month ($36 bimonthly, plus additional fee for water
usage over 6,000 gallons)
Facility Description:
The Pinery Wastewater Treatment Plant was originally constructed in 1990 and upgraded in
2005. The plant treats domestic wastewater from a service area located south of Parker
-22-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Colorado. Discharge from the treatment plant is directed into Cherry Creek. Water quality-based
limitations for phosphorus and other pollutants have been established in the NPDES permit to
protect the shallow Cherry Creek aquifer and the reservoir. The enhanced biological nutrient
removal process utilized at the Pinery Plant is recognized as being very well operated and has
been studied and cited numerous times as an example of exemplary application of this
technology.
Treatment consists of screening and grit removal; BNR Activated Sludge (BardenPho 5 Stage
[Anaerobic Basin, Anoxic Basin, Oxidation Ditch Aeration Basin, Anoxic Basin, Reaeration
Basin]); Clarifiers [2 parallel rectangular]; Chemical addition using alum and polymer; Effluent
Polishing and filtration [using 4 US Filter Memcor filter modules] ; and UV disinfection. The
US Filter units utilize two-stage filtration in which the first stage is upflow through a plastic
media with air scour. The second stage filtration is through a downflow, mixed media with
backwash cleaning. The concentration of alum used for coagulation was reported to be 95 mg/1.
Residuals solids removed during treatment are routed to aerobic digester tanks. These solids are
dewatered on a belt filter press and dried/composted for land application.
Operational Considerations:
The concentration of total phosphorus in the plant influent is high (8 to 10 mg/1) because
phosphoric acid is used in the District's water supply for corrosion control.
Ortho-P is monitored by on-line instrumentation (Hach series 5000 Low-Range) in the
influent to the chemical treatment system and the final filter effluent. This equipment is
capable of measuring phosphorus to concentrations as low as 0.01 mg/1.
The Memcor filters used for effluent polishing are upflow through plastic media
(adsorption) and downflow through an anthracite sand media filter. Backwash of the
filter unit components is automatically initiated when a preset head loss is measured. The
total flow of backwash water used to clean the filters is about 15%. Flushing and
backwash water is equalized and introduced to the reaeration basin ahead of the
secondary clarifiers.
Sulfuric acid is used for pH control in the treatment process as optimum A1PO4
precipitation occurs when the pH = 6.0.
-23-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Modular Memcor Filter (US Filter Company) at Pinery WWRP. Each of these modules has a
treatment capacity of approximately 0.5 mgd.
Metering equipment used for chemical addition at Pinery WWRP
-24-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Memcor filter module at Pinery WWRP undergoing backwash
The laboratory TP and Ortho-P procedures use a Hach DR4000 colorimeter with 1"
cuvettes which can achieve total phosphorus detection levels to less than 0.01 mg/1.
Chemical sludge does not settle well in the secondary clarifiers at the Pinery WWTP, so
a portion goes over the weirs and is removed again in effluent filter system.
Water conservation measures and the progressive water and sewer use fee are working in
the District. The result is that water consumption is decreasing and the concentration of
influent wastewater is increasing.
Operators have found measuring the oxidation-reduction potential (ORP) of wastewater
in the plant to be an effective parameter for managing the biological treatment system.
-25-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Clean Water Services, Rock Creek Advanced Wastewater Treatment Plant
Contact Information:
Clean Water Services
Rock Creek Advanced Wastewater Treatment Plant
3235 SW River Road
Hillsboro, OR 97123
503-648-8774
NPDES Permit No. OR0029777, expires 31 -JAN-2009
Design capacity: 39 mgd dry weather treatment
Receiving water: Tualatin River
Clean Water Services, Rock Creek AWWTP Performance Information:
Parameter
CBOD
TSS
Phosphorus
NPDES
Limitation
(monthly avg)
8 mg/1 (seasonal)
8 mg/1 (seasonal)
*0. 10 mg/1
*Avg of
monthly
averages
1.4 mg/1
1.2 mg/1
0.07 mg/1
^ange of monthly
averages
1.3 to 1.5 mg/1
0.9 to 1.8 mg/1
0.04 to 0.09 mg/1
1Maximum
individual
measurement
(date)
1.6 mg/1 (5/05)
1.8 mg/1 (8/05)
0.09 mg/1 (9/05)
Reporting
period
5/05 to 10/05
5/05 to 10/05
5/05 to 10/05
* Limitation established as a monthly median concentration
1 Monitoring information from dry season when nutrient limitations apply (May through October
Rock Creek AWWTP Treatment Processes:
alum
lime polymer
Wastewater
Influent
45 MOD
headwork
Primary
clarifier
i i
i i
* »>
'-v.'.'.'.'.'.'.'.'.'.'.'.'.'.
Secon
lary 1
Aeration basin
clarifier
alum polymer
i i
i i
i i
T ,
^^
Sodium Sodium
hypochlorite i_:~~ i^*-
i i
i i
i i
Final effluent
claricone
- Zt> -
Mixed media filter
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Primary, secondary
And tertiary sludge
landfill
Anaerobic digester
centrifuge
Monthly residential sewer use fee: $16.07 plus $1.11/ccf/month. The average monthly
residential fee is $27.
Facility Description:
Clean Water Services Rock Creek AWWTP (from CWS informational publication)
Clean Water Services operates four wastewater treatment plants with a service area that includes
over 800 miles of collection system piping in Washington County, Oregon. The largest of these
WWTPs is the Rock Creek facility which discharges into the Tualatin River. These Clean
Water Services plants are staffed by well trained operators with support from knowledgeable
operations analysts. Numerous upgrades to treatment have been installed at the Rock Creek
WWTP over time. The most recent upgrade to improve phosphorus removal was installed in
1993. The Tualatin River contains natural background levels of phosphorus that are
significantly higher than observed in many other northwest watersheds. Because the water
quality of the Tualatin River was impaired by excessive nutrient loading from various sources in
the watershed, a TMDL was established which includes a wasteload allocation for phosphorus
loading from the Rock Creek AWWTP. The wasteload allocation is equivalent to the natural
background concentration of phosphorus in the River at the point of discharge. This wasteload
allocation is expressed in the NPDES permit as a monthly median limitation of 0.1 mg/1 which
applies seasonally from May through October.
-27-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Wastewater flow is divided for treatment through the east and west side treatment trains.
Treatment at the Rock Creek WWTP consists of screening and grit removal; alum addition;
primary clarification; extended aeration; secondary clarification; flocculation using alum and
polymer; tertiary clarification; filtration; disinfection (with chlorine) and dechlorination. Four 60
foot diameter ClariCone tertiary clarifiers are used on the east treatment train to provide contact
time and settling after addition of polymer and alum. Filtration on the east train is accomplished
with six monomedia anthracite gravity flow bed filters. The west treatment train uses
conventional clarifiers for tertiary settling followed by filtration through four dual media gravity
flow bed filters.
Phosphorus is removed in four locations within the Rock Creek treatment system: alum
enhanced removal in the primary clarifiers; biological removal in the aeration basins; chemical
flocculation and removal in the tertiary clarifiers; and removal through filtration. Treatment
upgrades to install enhanced biological nutrient removal of phosphorus are being considered as a
means for reducing the current cost of chemicals used for phosphorus removal. Clean Water
Services maintains an informative website
(http ://www. cl ean water servi ces. org/Ab outUs /Waste water/TreatmentProce ss. aspx) which
provides additional information about current treatment and planned upgrades of this facility.
Operational Considerations:
The average concentration of total phosphorus in the raw plant influent is 6 mg/1.
Lime is added to maintain pH and alkalinity through the treatment process. The cost of
lime used for treatment is about $150,000 per year.
System analysts have determined that the phosphorus limitation will usually be met if the
total suspended solids concentration is 1.5 mg/1 or less in the final effluent. A strong
empirical relationship has also been observed that when the aluminum to total
phosphorus ratio is 5:1 to 7:1 in the secondary effluent, that the total phosphorus
concentration in the final effluent will be less than 0.1 mg/1.
A ratio (not stoichametric) of about 50:1 dry alum to phosphorus is the target dose rate in
the tertiary clarifiers. Alum use during May through October (when phosphorus
limitations apply) costs about $250,000, based on acquiring alum at $172 per dry ton.
This usage of alum equates to a cost of approximately $1,500 per day, or about $50 per
mgd of waste water treated.
The formation of struvites (ammonium, magnesium, phosphorus crystals) has been an
operational problem in some of the slow velocity piping, such as in the heat exchanger
recirculation.
Resolubization of phosphorus in return streams from anaerobic handling of removed
solids represents about 20 percent of the phosphorus and ammonia-nitrogen loading to
the plant. The loading from these return streams is managed by storage and flow
equalization back into the treatment system.
-28-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
The secondary effluent that goes to tertiary treatment typically has the following
characteristics: total phosphorus < 0.5 mg/1; orthophosphorus <0.1 mg/1; TSS < 10 mg/1;
COD < 50 mg/1 and N-NH3 <0.01 mg/1.
-vth
Performance records kept by Clean Water Services staff document that the 50 percentile
of monthly average total phosphorus concentrations achieved over the previous eight
years is 0.071 mg/1. Concentration of total phosphorus in the final effluent have been
reduced to as low as 0.032 mg/1. CWS systems analysts expect that better phosphorus
removal could be achieved if more effective final filtration equipment were installed.
They estimate that if a final effluent TSS concentration of 0.5 mg/1 were achieved, the
total phosphorus concentration would be about 0.03 mg/1.
Aeration basin at Clean Water Services, Durham AWWTP. The basins at the Rock Creek
WWTP may be modified in the future to also provide enhanced biological phosphorus removal.
-29-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Clean Water Services, Durham Advanced Wastewater Treatment Plant
Contact Information:
Clean Water Services
Durham Advanced Wastewater Treatment Plant
16580 SW 85th Street
Tigard. OR 97224
Phone No. 503.831.3600
NPDES Permit No. OR0028118, expiration date JAN-31-2009
Design capacity: 24 mgd average dry weather treatment flow
Receiving water: Tualatin River
Durham AWWTP Treatment Process:
(alum)
lime
VFA
Wastewater
Influent
24 MGD
headwork
Primary
clarifier
Anaerobic
zone
Anoxic
zone
Aerated zone
Secondary
clarifier
alum
(polymer)
i
_*_
Tertiary
clarifier
Sodium
Sodium
hypochlonte hisll,fite
Final effluent
Mixed media filter
-30-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Primary
sludge
Secondary and
Tertiary sludge
landfill
Anaerobic digester
Clean Water Services, Durham AWWTP DMR information:
Parameter
CBOD
TSS
Phosphorus
NPDES
Limitation
(monthly avg)
8 mg/1 (seasonal)
8 mg/1 (seasonal)
*0.11 mg/1
*Avg of
monthly
averages
2.2 mg/1
1.8 mg/1
0.07 mg/1
^ange of monthly
averages
1.7 to 2.6 mg/1
1.7 to 2. 8 mg/1
0.05 to 0.1 mg/1
1Maximum
individual
measurement
(date)
4.2 mg/1 (6/05)
2.8 mg/1 (5/05)
0.1 mg/1 (9/05)
Reporting
period
5/05 to 10/05
5/05 to 10/05
5/05 to 10/05
* Limitation establishes as a monthly median concentration
1 Monitoring information from period when seasonal nutrient limitations apply (May through October)
Monthly sewer use fee: $16.07 plus $1.11/ccf/month. The average monthly residential fee is
$27.
Facility Description:
Clean Water Services operates four wastewater treatment plants with a service area that includes
over 800 miles of collection system piping in Washington County, Oregon. These Clean Water
Services plants are staffed by well trained operators with support from knowledgeable operations
analysts. The Durham Advanced Wastewater Treatment Plant is the second largest of the four
WWTPs and discharges treated effluent into the Tualatin River. This plant was constructed in
1976 and upgraded to the existing treatment configuration in 1989. Maximum daily wet weather
treatment capacity is about 80 mgd.
The Tualatin River reportedly contains natural background levels of phosphorus that are
significantly higher than observed in many other northwest watersheds. Because the water
quality of the Tualatin River was impaired by excessive nutrient loading from various sources in
the watershed, a TMDL was established which includes a wasteload allocation for phosphorus
loading from the Durham AWWTP. The wasteload allocation is equivalent to the estimated
natural background concentration of phosphorus in the River. This wasteload allocation is
expressed in the NPDES permit for this facility as a monthly median limitation of 0.11 mg/1
which applies seasonally from May through October.
Treatment at the Durham AWWTP consists of screening and grit removal; primary clarification;
biological treatment with enhanced biological nutrient removal; secondary clarification:
-31-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
chemical addition of alum and polymer for phosphorus removal; tertiary clarification; filtration
through dual media gravity bed filters and disinfection. Lime is added to the biological process
to maintain pH and alkalinity. Removed solids are anaerobically digested, dewatered by
centrifuge, and utilized as fertilizer. A two-stage fermenter is operated to produce volatile fatty
acids which are added to the biological contact basins. The enhanced biological nutrient removal
process at times reduces total phosphorus to levels that are less than the 0.11 mg/1 permit
limitation. However, this performance is not achieved during the entire period when the seasonal
phosphorus limitations are in effect. The tertiary treatment with chemical addition and filtration
provides assurance that the final effluent is of consistently good quality. Some of the treated
effluent is reclaimed for irrigation.
Operational considerations:
Nitrate-nitrogen may interfere with biological phosphorus removal if sufficient volatile
fatty acids (VFAs) are not maintained. Therefore, creation of volatile fatty acids (VFAs)
is necessary for the enhanced biological phosphorus removal process to work properly.
Operators route solids from the primary clarifier to a two-stage fermenter system. The
fermenter produces 500 mg/1 VFAs when provided a two and one half day solids
retention time. For good biological removal of phosphorus, the optimal relationship for
VFAs to phosphorus in the contact basins is about 5:1.
Operators have determined that orthophosphorus comprises about 75 to 80 percent of the
total phosphorus. Automatic sampling equipment provides continuous, low level
orthophosphorus information that can be used to adjust treatment as necessary. A target
of 0.02 mg/1 orthophosphorus was identified as representing optimal treatment
performance by the current treatment configuration.
Secondary effluent quality information is used to operate the biological phosphorus
removal process. Operators target achieving a final effluent concentration of 0.07 mg/1
by reducing total phosphorus in the secondary effluent to 0.50 mg/1 or less.
The amount of biosolids generated by biological phosphorus removal is somewhat more
than would be produced by using only chemical treatment for phosphorus removal.
Return streams from anaerobic handling of removed solids (supernatant from digesters
and centrate from centrifuges) comprises about 20 percent of the total phosphorus loading
to the plant. The loading from these return streams is managed by storage and
equalizing its flow back into the treatment system.
-32-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Empty tertiary clarifier at Clean Water Services, Durham AWWTP
Empty gravity flow bed filter at Clean Water Services, Durham AWWTP
-33-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Stamford Wastewater Treatment Plant
Contact Information:
Village of Stamford Wastewater Treatment Plant
Railroad Avenue
Stamford, New York 12167
Telephone: 607-652-3172
Operated by: Delaware Operations
NPDES Permit No. NY0021555, expiration date JUL-01-2009
Receiving water: West Branch Delaware River Watershed
Stamford WWTP Treatment Process:
Stamford WWTP Performance Information:
Parameter
Phosphorus
N-NH3
TSS
CBOD
NPDES
Limitation
0.2 mg/1
2.5 mg/1
30 mg/1
25 mg/1
Average of
monthly
averages
*<0.011mg/l
*<0.98 mg/1
*<3.3 mg/1
*<4.5 mg/1
Range of monthly
averages
<0.005to < 0.06 mg/1
O.03 to 0.63 mg/1
< 2 to 8 mg/1
<3.5 to 8 mg/1
Maximum
individual
measurement
0.06(11/05)
0.63 (7/05)
8 (3/03)
8.5 (8/04)
Reporting
period
2/03 to 5/06
7/04 to 5/06
2/03 to 5/06
7/04 to 5/06
-34-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
* Almost all measurements were reported as less than (<) values
Design Treatment Capacity:_ 0.5 MGD (requested certification for 0.7 mgd pending @ New
York State Department of Environmental Conservation (NYSDEC)
Monthly household sewer use fee: $10 /month
Note about sewer fees: The costs of construction, operation and maintenance of any and all unit
processes (which are in excess of New York State standards at this and other WWTPs
discharging into the Delaware River watershed) are subsidized by the City of New York. The
Stamford WWTP unit processes funded by the City of New York include the chemically-
enhanced tertiary filtration, redundant disinfection, dechlorination systems, emergency stand-by
power generation, telemetry and alarm systems, and sludge dewatering. The incremental O&M
cost increase of these unit processes, as well as additional operations staffing and accounting
personnel, are funded annually by the City of New York.
Facility Description:
The Village of Stamford wastewater treatment plant (Stamford) receives municipal wastewater
from residences and a number of businesses in this community. Delaware Operations is
contracted to operate this facility for Stamford. Discharge of treated effluent from Stamford is
into the 2,000 square mile New York City Watershed, including the Delaware River watershed,
which is a primary drinking water supply for the City of New York. To protect the quality of
this receiving water, the City of New York provides funding for municipal dischargers in the
watershed to construct and operate advanced wastewater treatment. In return for this financial
assistance, these municipalities must maintain and operate their facilities to produce high quality
effluent. Design criteria for tertiary treatment and NPDES permit limitations are established by
the New York State Department of Environmental Conservation.
Wastewater treatment at the existing Stamford WWTP was upgraded and became fully
operational in 2003. Treatment consists of grit removal and screening; extended aeration and
secondary clarification (in combined aeration basin/clarifier); chemical addition for flocculation
using PASS and filtration through two-stage Dynasand filters. Removed solids are routed to an
aerobic digester. Waste solids are dewatered in a belt press and sent to a landfill. There are also
large equalization basins available to which raw wastewater may be routed for storage during
times of high influent flow.
-35-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Combined aeration basin and clarifier (in center of unit) at Stamford WWTP
The DynaSand filters installed at Stamford were obtained from the Parkson Corporation. Both
the first stage and the second stage filters operate as continuous backwashing, upflow, sand
media filters. There are nine sets of first and second stage filters, each with an approximate
surface area of fifty square feet. The sand media in the two meter deep first stage filter has an
average diameter of 1.3 millimeters. The second stage sand media is 0.9 millimeters. Secondary
treated wastewater is pumped to a distribution header from which it flows by gravity through the
first and then the second stage filters. Influent to the first stage filters is chlorinated to inhibit
biological growth. Because PASS hydrolyzes so quickly, this flocculant is added to the influent
of each first stage filter, rather than being mixed in the distribution header. The reject stream
from the filters is routed to a small clarifier and the overflow is returned mixed with influent to
the first stage filter. Solids removed in the reject clarifier are routed to a new aerobic digester,
into which secondary solids are also mixed, and then dewatered in a newly installed 1.0 meter
belt press.
-36-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Lamella?
Gravity Settler
Inline mixer
x>0<
DynaSand*
Deep Bed Filter
DynaSand*
Standard Bed Filter
Generic diagram of two stage DynaSand filtration system (courtesy of Parkson Corporation).
Note: the Stamford WWTP uses a concrete clarifier in lieu of a lamella settler.
Operational Considerations:
Analyses for phosphorus, BOD and TSS in the final effluent are conducted using EPA-
approved testing methodologies by a NYS-certified laboratory. For data quality control
purposes, samples of final effluent are routinely split and sent to a state certified contract
laboratory which specializes in achieving extremely low reporting levels for phosphorus.
Nevertheless, most of the sample results are reported as less than values (<) on the
monthly discharge monitoring. These results routinely demonstrate the effluent as being
significantly below permit limitations but do not necessarily accurately characterize the
very low phosphorus concentrations in the effluent.
A correlation between pathogens and turbidity in the effluent was established for
municipal dischargers in the watershed. Continuous monitoring of turbidity is a closely
watched NPDES permit requirement. Treatment plant operation is optimized to achieve
very low effluent turbidity. The excellent removal of other pollutants such as
phosphorus, is primarily a by-product of WWTP operation focused on maintaining low
turbidity in the final effluent.
The design hydraulic loading rate specified by New York City for the Parkson Dynasand
filters is 3.36 gallon/square foot/minute (g/ft2/min). Operators report the best
performance has been achieved at Stamford with a filter loading rate of between 4.0 and
-37-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
4.5 gpm/sq. ft. but stated that the filters continue to perform very well up to loading rates
of over 5.0 gpm/sq.ft.
The filters in use are routinely rotated based on the amount of time they have been in
service. There are nine (9) filter trains at the Stamford WWTP; under typical operating
conditions, only 2 filters are running.
PASS is obtained from the Eaglebrook Company (phone number 450.652.0665) at an
approximate cost of $4/gallon. Stamford operators say the addition of PASS is flow
paced at a rate of about 30 gallons per one half mgd of wastewater treated. This equates
to a cost of approximately $240/day/per mgd for flocculant.
There is essentially no sand lost from the DynaSand filters during operation.
The reject rate from the filters is designed and operated to be about 10 percent of the total
flow. The percent reject decreases at higher loading rates.
The overflow rate from each DynaSand filter can easily be adjusted by inserting different
size plastic weirs.
Plastic weirs used for adjusting overflow rate from DynaSand Filters
The turbidity of the effluent was 0.053 NTU at the time of EPA's site visit. Turbidity is
closely monitored as it has been determined to be a good surrogate for measuring
pathogens potentially present in the discharge. The NPDES permit limit for turbidity is
0.5 NTU.
-38-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Walton Wastewater Treatment Plant
Contact Information:
Walton Wastewater Treatment Plant
54 South Street
Walton, New York 13856
Phone Number (607) 865-6993
Operated by: Delaware Operations
NPDES Permit No. NY0027154, expiration date Feb 2008
Receiving water: Delaware River Watershed
Design Treatment Capacity: 1.55 mgd (average daily flow)
Treatment Process Diagram:
Influent
Headwork
v
;<;<;<; ;<;<;<;<;
*«*<*<* *<*<*<* * t
^^~-^
i Chlorine
i
T * »
Gravity thickener
Coagulant DualSand Dechlorination
A1C1 filters ,
Plant
Effluent
equalization tank
Secondary clarifier
i
Aerobic digester
y sludge
^ \^>
^^~~^ '
Landfill
Belt filter press
-39-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Walton WWTP Performance Information:
Parameter
Total P 1
N-NH32
TSS
CBOD
NPDES
Limitation
0.2 mg/1
8.8 mg/1
30 mg/1
25 mg/1
Average of
monthly
averages
<0.01 mg/1
0.24 mg/1
<3.5 mg/1
<3.7 mg/1
Range of monthly
averages
<0.005to < 0.06 mg/1
O.05 to 1.4 mg/1
<2.6 to <4.9 mg/1
<2.5 to <4.5 mg/1
Maximum
individual
measurement
0.06 mg/1 (3/06)
1.4 mg/1 (6/05)
<4.9 mg/1 (12/05)
<21 mg/1 (7/04)
Reporting
period
2/03 to 3/06
6/03 to 6/06
2/03 to 3/06
2/3 to 3/06
1 Almost all phosphorus measurements were reported as less than (<) a specified detection value.
The reported detection value was used for summarizing performance, although the actual
concentration is lower.
2 There are seasonal limitations for ammonia nitrogen and performance is summarized for the
period when this limitation applies.
Monthly household sewer use fee: $10 month plus charges based on water usage.
(Note: the costs of construction, operation and maintenance of this and other WWTPs
discharging into the Delaware River watershed are subsidized by the City of New York.)
Facility Description:
The Walton Wastewater Treatment Plant (WWTP) receives municipal wastewater from
residence and a number of businesses in this community plus a significant amount of wastewater
from a nearby dairy creamery. Wastewater from the creamery constitutes about 80 percent of the
organic loading and 40 percent of the flow into the WWTP. The influent to the WWTP would
be characterized as high strength with an average BOD concentration of 350 mg/1. Discharge of
treated effluent from Walton is into the 2,000 square mile Delaware River watershed, which is a
primary drinking water supply for the City of New York. To protect the quality of this receiving
water, the City of New York provides funding for municipal dischargers in the watershed to
construct and operate advanced wastewater treatment. In return for this financial assistance,
these municipalities must maintain and operate their facilities to produce high quality effluent.
Design criteria for tertiary treatment and NPDES permit limitations are established by the New
York Department of Environmental Conservation.
Wastewater treatment at the existing Walton WWTP was upgraded and became fully operational
in 2003. Treatment consists of grit removal and screening; extended aeration and secondary
clarification; chemical addition for flocculation using aluminum chloride (added to the
wastewater at both the secondary clarifiers and the distribution header for the DynaSand filters);
and filtration through two-stage Dynasand filters; disinfection with chlorine and dechlorination
with sulfur dioxide. Chlorine is added to the filter influent to control biological growth in the
filters. Removed solids are routed to an aerobic digester. Waste solids are dewatered in a belt
press and sent to a land fill.
The DynaSand filters installed at the Walton WWTP were obtained from the Parkson
Corporation. Both the first stage and the second stage filters operate as continuous backwashing,
upflow, sand media filters. There are five sets of first stage and second stage filter modules.
-40-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Each module contains four DynaSand filters which have an approximate surface area of two
hundred square feet (or eight hundred square feet per module). So, there is total of 40,000 square
feet surface area of primary filters and the same amount of secondary filter surface area. The
sand media in the two meter deep first stage filters has an average diameter of 1.3 millimeters.
The second stage filters are one meter deep and contain sand media of 0.9 millimeter average
diameter. The number of filters in use is adjusted as needed to accommodate flow through the
plant. The filter modules in use are routinely rotated according to time in service.
Secondary treated wastewater is pumped to a distribution header where aluminum chloride and
chlorine is added and from which it flows by gravity through the first and then the second stage
filters. The reject stream from the filters is routed to the headworks of the plant.
DynaSand Filters at
Walton WWTP
The above picture shows a side view of the distribution header (far right), first stage and second
stage DynaSand filters installed at the Walton WWTP. Flow through the filters is by gravity
from the distribution header. The people shown in this picture are standing on grating above the
second stage filters. This building houses twenty (2 meter deep) first stage and twenty (1 meter
deep) second stage DynaSand filters which have a combined total surface area of about 80,000
square feet. The installation is configured to create five banks of filters which are rotated into
-41-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
use on a time basis. At the time of this visit, two of the five filter banks were being used to treat
the entire wastewater flow at this plant.
View into top of DynaSand filter at Walton WWTP. This picture shows sand being returned
from washer at top of lift tube in a second stage filter. These filters are designed to wash sand
continuously (without any backwash cycle).
Operational Considerations:
About 80 percent of the loading and 40 percent of the wastewater flow into the Walton
WWTP comes from the Kraft Dairy operation.
Analyses for phosphorus, BOD and TSS in the final effluent are conducted using EPA
approved testing methodologies. For data quality control purposes, samples of final
effluent are routinely split and sent to a state certified contract laboratory which
specializes in achieving extremely low reporting levels for phosphorus. Nevertheless,
most of the sample results are reported as less than values (<) on the monthly discharge
monitoring. These results routinely demonstrate the effluent as being significantly below
permit limitations but do not necessarily characterize the excellent quality of the effluent.
-42-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
The turbidity of the effluent was 0.062 NTU at the time of EPA's site visit. Turbidity is
closely monitored as it has been determined to be a good surrogate pollutant for
measuring the pathogens potentially present in the effluent. The NPDES permit limit for
turbidity is 0.5 NTU.
The maximum treatment capacity of the plant is 3 mgd. The DynaSand filters are not the
limiting factor as this flow can be treated by using only 3 of the 5 filter modules.
Total phosphorus concentrations in the secondary effluent typically range between 1 to 2
mg/1.
The cost of aluminum chloride to the Walton WWTP was reported to be $4.64/gallon. A
streaming current meter (which measures the negative charge of particles in the water) is
used to control aluminum chloride dosing. Approximately 50 to 60 gallons of aluminum
chloride are used each day which equates to a daily cost of about $250/day at this 1.5
mgd facility.
The filter press is operated 3 times a week to dewater solids from the aerobic digester.
Solids are sent to a landfill and removed liquid is returned to the plant headworks.
Operators reported observing no changes in treatment plant performance caused by the
solids handling return streams.
The design hydraulic loading rate specified by New York City for the Parkson DynaSand
filters is 3.36 gallon/square foot/minute (g/ft2/min). Operators report they typically run
filters at hydraulic loading rate of between 4.0 and 4.5 g/ft2/min but stated the filters
would continue to perform very well up to loading rate of 5.0 g/ft2/min.
The filters in use are routinely rotated based on the amount of time they have been in
service.
There is essentially no sand lost from the DynaSand filters during operation.
The reject rate from the filters is designed and operated to be about 10 percent of the total
flow.
The overflow rate from each DynaSand filter can easily be adjusted by inserting different
size plastic weirs (pictured in Stamford WWTP description).
-43-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Milford Wastewater Treatment Plant
Contact information:
Mailing address:
Milford Wastewater Treatment Plant
P.O. Box 644
Milford, MA 01757
Phone Number: 508-478-0059
NPDES Permit No. MA0100579, expiration date 31-MAR-2010
Receiving water: Headwaters of Charles River
Permitted flow: 4.8 mgd (monthly average)
Milford WWTP Process Diagram:
' I» ' I»
»feAj&A^
1,1,1,1,1,1
i
Primary.
secondary and
tertiary sludge
To incineration
-44-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Milford WWTP Performance Information:
Parameter
BOD
TSS
N-NH3*
Phosphorus*
NPDES
Limitation
30/45 mg/1
30/45 mg/1
1.0 mg/1
0.2 mg/1
Avgof
monthly
averages
3. 7 mg/1
1.7 mg/1
0.26 mg/1
0.07 mg/1
Range of
monthly
averages
1.3 to 7. 4 mg/1
0.48 to 8.0 mg/1
0.05 to 0.48 mg/1
0.04 to 0.16 mg/1
Maximum
individual
measurement(date)
9.1 mg/1 (4/05)
13.6 (2/03)
0.19 mg/1 (6/03)
0.16 mg/1 (6/04)
Reporting
period
7/03 to 4/06
1/03 to 4/06
6/03 to 10/05
6/03 to 10/05
* NPDES limitations for phosphorus and ammonia are seasonal. The 0.2 limit for phosphorus
applies April 1 - October 31. The ammonia limitation for the month of May is 5.0 mg/1 only and
is 1.0 mg/1 for the period from June 1 - October 31. The performance information shown is for
the periods of each year when these seasonal water quality-based limitations apply.
Monthly residential sewer use fees: $27.50 ($330/year)
Facility Description:
Wastewater treatment facilities were originally constructed to serve the local community in
1902. Remnants of that original facility and some of the subsequent treatment upgrades may still
be observed. The current treatment facility was constructed in 1985 and treats domestic
wastewater from the surrounding service area. Discharge is into the headwaters of the Charles
River. During the dry period of the year, the discharged effluent constitutes the entire flow at
this point of the river. The collection system suffers from inflow and infiltration problems which
cause influent flow to the WWTP to be quite high in response to significant rain events. As a
result, influent BOD concentrations are sometimes diluted to below 80 mg/1. Severe rainfall
during the preceding week resulted in influent flows being greater than 8 mgd at the time of the
site visit. Although the permit limitation for flow is 4.8 mgd, the plant has demonstrated the
ability to treat these high flows and still produce an excellent quality effluent.
Treatment at the Milford WWTP consists of screening and grit removal; primary clarification;
trickling filters; intermediate clarification (with polymer addition to aid settling); rotating
biological contactors; secondary clarification; chemical addition using poly-aluminum chloride;
filtration through mixed media traveling bed filters; ultraviolet disinfection. The final effluent is
discharged down a cascading outfall to achieve reaeration prior to mixing in the receiving water.
Approximately 1 mgd per day of the final effluent is utilized by the local power company for
cooling water.
-45-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Operational considerations:
A colorimetric method is used for analyzing total phosphorus. The reportable level
achieved in the Milford laboratory using this testing methodology is typically about 0.02
mg/1 total phosphorus.
Approximately 17 to 20 gallons of polymer are added prior to the intermediate clarifiers.
Approximately 300 to 400 gallons per day of PAC1 are used to flocculate phosphorus.
Facility representatives stated the cost of PAC1 to be $1.50/gallon. So, the total daily cost
of PAC1 ranges from about $450 to $600.
Removed solids are routed to an aerobic thickener. The concentration of thickened solids
coming out of the thickener is only about 3%. Having to haul so much water with these
solids represents the largest single cost ($350,000/year) of operating this WWTP.
The trickling filters and rotating biological contactors appear to be very resilient to
increase flows caused by inflow and infiltration. However, the record setting rainfall
during the winter months of 2006 had affected treatment removal of ammonia-nitrogen.
ffr
Trickling filters at Milford WWTP
ffl'
Cascading discharge structure into Charles River at Milford WWTP
-46-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Alexandria Sanitation Authority (ASA) Advanced Wastewater Treatment
Plant
Contact Information:
Alexandria Sanitation Authority
1500 Eisenhower Avenue
Alexandria, VA 22314 1987
Phone: 703-549-3381
Aerial View on ASA Advanced Wastewater Treatment Facility (from ASA staff)
NPDES Permit: No. VA0025160 , expires 20-JAN-2009
Receiving water: Hunting Creek (a tributary to the Potomac River)
Design Treatment Capacity: 54 mgd (average dry weather)
Phosphorus treatment technology: Triple point chemical addition in which ferric chloride is
added to primary and secondary settling tank influents and alum is added to the tertiary settling
tank influent.
-47-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Alexandria AWWTP (provided by ASA staff)
Schematic of New Liquid Treatment Processes
Ra*
WiBteiratH
Tten»*rt
Funps
Alexandria Advanced WWTP Performance Information:
Parameter
Phosphorus
N-NH3
TSS
CBOD
'NPDES
Limitation
(monthly avg)
0.18mg/l
8.4 mg/1
6 mg/1
5 mg/1
Average of
monthly
averages
0.065 mg/1
*<0.1 mg/1
1.5 mg/1
*<0.1 mg/1
Range of monthly
averages
0.04 to 0.1 mg/1
0 to 0.2 mg/1
<0.1to5.4mg/l
0 to 0.5 mg/1
Maximum
individual
measurement
0.15 mg/1 (4/05)
0.6 mg/1 (1/06)
9.2 mg/1 (2/04)
1.0 mg/1 (12/05)
'Reporting
period
9/04 to 5/06
9/04 to 5/06
9/04 to 5/06
9/04 to 5/06
* Monitoring results during this period were typically reported as zero or less than detection
1 The summarized monitoring data is inclusive of all values submitted during the reporting period regardless of
when seasonal water quality based effluent limitations apply
Monthly household sewer use fee: $4.17 plus $4.49 per 1,000 gallons water used
Facility Description:
The ASA Advanced WWTP treats wastewater with combined storm sewers from a service area
of approximately 51 square miles including the City of Alexandria and portions of Fairfax
County. The population served is approximately 400,000 people. ASA began construction to
upgrade the 54 mgd design flow facilities in 1999 to meet the water quality requirements of the
Potomac Embayment Standards and the Chesapeake Bay Agreement. Initial operation of the new
Biological Nutrient Removal (BNR) system was achieved in December 2002.
-48-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Treatment consists of screening; grit removal; primary settling with possible addition of ferric
chloride and polymer; methanol or volatile fatty acid added to biological reactor basins to aid
BNR; ferric chloride and polymer addition prior to secondary settling; alum addition and
mixing; tertiary clarification with inclined plate settlers; dual media gravity bed filtration; UV
disinfection and post aeration. Removed solids are dewatered in centrifuges and the centrate is
returned to the primary clarifiers. Then sludge is pre-pasteurized; anaerobically digested;
centrifuged again and sent to land application as Class A biosolids. The moisture content of the
biosolids after treatment is about 70 percent.
Operational Considerations:
High influent flows during rain events often exceed 80 mgd. The plant has treated peak
influent flows of 108 mgd during extreme storm events.
The average influent concentration of total phosphorus was reported to be about 4.5 mg/1.
Operators reported an observed trend of increasing influent concentrations while influent
flow has remained steady. Speculation about the cause of these phenomena is that the
ASA progressive sewer rates (which are based in part on water usage) have promoted
water conservation.
The facility is currently considering treatment upgrades necessary to achieve a required
monthly average effluent target for total nitrogen of 3.0 mg/1.
Multiple point chemical addition is utilized for phosphorus removal. Ferric chloride is
added to primary and secondary settling tank effluents. Alum is mixed into the influent
to the tertiary settling tanks. The alum contained in the return stream was reported to aid
in phosphorus removal through the plant processes.
Sodium hydroxide is added to the primary effluent, the secondary effluent and after the
gravity filters to increase pH and maintain alkalinity.
The concentration of total phosphorus in the secondary effluent is typically about 0.4 to
0.5 mg/1. Facility representatives reported that the average concentration of phosphorus
in the final effluent during 2005 was approximately 0.05 mg/1.
The approximate annual cost for chemicals used in treatment is $2.4 million. This
includes $1.4 million for sodium hydroxide, $300,000 each for alum and polymer, and
$300,000 for ferric chloride and methanol.
The plant is equipped with custom-made computerized controls (supervisory control data
acquisition system) to enhance the efficiency of operation.
Biological treatment at ASA includes methanol fed to sequential anoxic and aerobic
zones in the secondary process. Primary wastewater is 'step fed' into the secondary
basins. A portion of the wastewater from each aerobic zone is recycled back to the
preceding anoxic zone.
-49-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Chemical mixing paddles in front portion of sedimentation tanks at Alexandria AWWTP
Bed filter undergoing backwash at Alexandria AWWTP
-50-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Upper Occoquan Sewage Authority (UOSA)
Millard H. Robbins Regional Wastewater Reclamation Facility
Contact information:
Upper Occoquan Sewage Authority
Millard H. Robbins Regional Water Reclamation Plant
14631 Compton Road
Centreville, VA 20121-2506
Phone No. 703-830-2200
NPDES Permit: No. VA0024988, expiration date FEE-19-2007
Treatment capacity: 42 mgd annual average flow, 128 mgd instantaneous peak flow
Receiving water: Unnamed Tributary of Bull Run Creek (Bull Run is a major tributary of the
Occoquan Reservoir)
UOSA WRF Treatment Performance Information:
Parameter
Total
Phosphorus
TSS
NPDES
Limitation
0.10mg/l
1 mg/1
Average of
monthly**
averages
*<0.088 mg/1
*<0.549 mg/1
Range of monthly**
averages
0.023 to <0.282mg/l
0 to 2 mg/1
Maximum
individual
measurement
0.580 mg/1 (2/03)
NA
Reporting
period
3/02 to 12/04
3/02 to 9/03
2/05 to 6/06
* estimated average because many measurements were reported as less than (<) values or below
detection limit
** Weekly averages for Total Phosphorus
Monthly residential sewer use fees: (of the 4 four UOSA member jurisdictions):
- Fairfax County sewer rates: $3.03/1000 gallons (FY 2004)
- Prince William County sewer rates: $3.75/1000 gallons (FY 2003)
- City of Manassas sewer rates: $4.09/1000 gallons (FY 2004)
- City of Manassas Park sewer rates: $35.00 as monthly Water and Sewer Service Charge
(FY 96 through FY 2004)
-51-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
UOSA Treatment plant schematic (provided by UOSA):
Millard H. Rabbins Regional Water Reclamation Plant
Capacity
42 MOD Annual Average flow
54 MOD Peak Month (30-day rolling)
128.4 MOD Peak Instantaneous influent
90 Million gallons on-site emergency storage
7.5 MW emergency generator capacity
Key Permit Requirements
Chemical Oxygen Demand (COD)
Total Phosphorus (TP)
Total Suspended Solids (TSS)
Total Kjeldall Nitrogen (TKN)
Turbidity
< lOmg/L
<0.1 mg/1
<1.0mg/L
<1.0mg/L
<0.5 NTU
Conventional Treatment
Advanced Treatment
Gfavily Filters
Screenings and Gril
-52-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Facility Description:
For nearly 30 years, the Upper Occoquan Sewage Authority (UOSA) has provided advanced
wastewater treatment water reclamation for a service area in Virginia that includes portions of
Fairfax County, Prince William County, and the cities of City of Manassas, and the City of
Manassas Park. Nineteen miles downstream from the UOSA discharge is a drinking water
withdrawal from the Occoquan Reservoir that serves approximately 1.3 million people. Around
1972 UOSA selected a biological, physical, chemical treatment process (high lime treatment
system) that could reliably produce a high quality reclaimed wastewater that would both protect
the quality and augment the amount of water in the reservoir.
The 10 mgd treatment capacity of the original plant has been upgraded in several stages to about
54 mgd since it began operation in 1978. Continuing rapid development and population growth
in the service area is again prompting consideration of treatment plant expansion to
accommodate the need for additional wastewater treatment capacity. In 1972, the high lime
treatment process represented the best technology for consistently achieving the necessary high
quality effluent. However, since that time other treatment technologies have evolved that also
produce high quality effluent. The next plant expansion may include use of a technology other
than high lime treatment.
UOSA maintains and operates this facility with well- qualified staff that routinely provides
educational tours of their treatment facility. EPA greatly appreciates that UOSA allowed use of
their educational materials for describing the treatment process in this report.
UOSA liquid treatment process is composed of:
A conventional treatment that removes 90% of most incoming pollutants: screening; grit
removal; primary clarification; aerobic biological selectors; activated sludge aeration
basins with nitrification/denitrification processes; secondary clarification.
A chemical advanced treatment - high-lime process - to reduce phosphorus to below
0.10 mg/1, to capture organics from secondary treatment, to precipitate heavy metals and
to serve as a barrier to viruses : lime slurry added to rapid mix basins (to achieve pH of
11); anionic polymer added in flocculation basins; chemical clarification; first stage
recarbonation to lower pH to 10; recarbonation clarifiers to collect precipitated calcium
carbonate; second stage recarbonation to lower pH to 7; storage in ballast ponds.
Physical advanced treatment to meet stringent limits for TSS (1 mg/1) and COD (10 mg/1)
including alum and/or polymer addition; multimedia filters; activated carbon contactors.
Disinfection by chlorination/dechlorination process.
-53-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
UOSA Water Reclamation Facility (WRF) - in the forefront are fine bubble diffuse aeration
basins constructed during the plant expansion to 27 mgd which are off-line in this picture.
Secondary Clarifiers with lime handling buildings in background at UOSA WRF
-54-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Removed solids processing at UOSA WRF:
Primary sludge and waste activated sludge are screened, digested, blended, dewatered by
centrifuge and ultimately dried to produce fertilizer pellets.
- Chemical and recarbonation sludge are concentrated by gravity thickeners, filter press
and then transported to a UOSA owned captive landfill.
Lime slurry being mixed into wastewater at UOSA WRF
Operational Considerations:
The UOSA WRF experiences significant increased influent flows as the result of inflow
and infiltration into the collection system. Although the annual average design flow into
the plant is approximately 42 mgd, peak hourly influent flows of 120 mgd have been
experienced during extreme storm conditions.
Handling and mixing (slaking) lime is "messy". Scaling in the treatment system after
lime addition also presents a maintenance problem.
Operators believe the existing treatment system could achieve even lower levels of
phosphorus in the final effluent with additional chemical addition.
The 2006 operating budget was $21,227,800 to operate and maintain this facility.
Over half of this cost is for UOSA staff wages. Electrical power and chemical costs are
approximately $2,691,000 and $1,562,000, respectively.
-55-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Lime scaling on chemical clarifier weirs at the UOSA WRF
-56-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Fairfax County Wastewater Management, Noman M. Cole Jr. Pollution
Control Plant
Contact Information:
Wastewater Treatment Division
Noman M. Cole Jr. Pollution Control Plant
9399 Richmond Highway
Lorton, VA 22079
Phone No. 703.550.9740
NPDES Permit: No. VA0025364, expiration date APR-13-2008
Design capacity: 67 mgd
Receiving water: Pohick Creek, tributary of Potomac River and Chesapeake Bay
Noman Cole WWTP Performance Information:
Parameter
Total
Phosphorus
Ortho-
phosphorus
NH3-N
BOD
TSS
NPDES
Limitation
0.18mg/l
none
**1 mg/1
5mg/l
6 mg/1
Average of
monthly averages
*<0.061 mg/1
*<0.057 mg/1
*<0.040 mg/1
below detection
limit
*<1.21 mg/1
Range of monthly
averages
<0.02to <0. 13 mg/1
<0.05to<0.11mg/l
0 to 0.20 mg/1
Non detectable to <2
mg/1
0 to 3.5 mg/1
Maximum
individual
measurement
0.20 mg/1 (10/05)
0.20 mg/1 (10/05)
0.64 mg/1 (10/05)
2 mg/1 (4/03)
4.1 mg/1 (12/04)
Reporting
period
4/03 to 6/06
4/03 to 6/06
4/03 to 6/06
4/03 to 6/06
4/03 to 6/06
* Many measurements were reported as less than (<) values or below detection limit
** Seasonal limitation : from April to October (2.2 mg/1 from November to March)
Monthly sewer use fee: $ 3.28/1000 gallons used. The average monthly residential fee is $21.
-57-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
RPl
PROCESS FLOW DIAGRAM
NOMAN M. COLE.JR.. POLLUTION CONTROL PLANT . COUNTY OF FAIRFAX . VIRGINIA
PROCESS LEGEND
PRELIMINARY/PRIMARY TREATMENT
BNR
AWT
SOLIDS HANDLING
INCINERATION
ODOR CONTROL
SUPPORT S ANCILLARY
(Diagram provided by Fairfax County WWTP staff)
DUAL-MEDIA I 1I _-^ |
GRAVITY | i-i [ V
FILTERS (10) y ^
MONO-MEDIA
GRAVITY
FILTERS (8)
GFE
P.S.
FF
CHLORINATION /
DECHLORI NATION
TANK
HH
5
DEFOAME
FT V-i
>DIUM l^/ uui
ULFITE Htli
APW
PP P.S.
PLANT EFFLUEN
TO POHICK CREE
-58-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
Facility Description:
April 2007
Fairfax County is one of 15 counties and cities in Virginia and Maryland that comprise the
Washington D.C. Metropolitan Statistical Area. Fairfax County owns and operates the Noman M.
Cole Jr. Pollution Control Plant. This facility receives mostly domestic wastewater from over
3,200 miles of sewer lines in the service area and currently treats an average influent flow of 45
mgd. This and other municipal dischargers to the Potomac River and Chesapeake Bay are
required to achieve monthly and weekly average permit limitations for total phosphorus of 0.18
and 0.27 mg/1, respectively. A monthly average limitation of 3 mg/1 for total nitrogen will
become effective in the year 2010.
Treatment at the Noman Cole Plant consists of screening; primary clarification (covered for odor
control); biological treatment with enhanced biological nutrient removal (BNR); polymer
addition as needed; secondary clarification; equalization and storage in retention ponds; tertiary
clarification with ferric chloride addition to remove phosphorus; disinfection with sodium
hypochlorite; filtration through dual/mono media gravity bed filters. Tertiary sludge is routed to a
gravity thickener to create volatile fatty acids (VFAs) which are added to aid the biological
phosphorus removal process. Removed solids from the primary and secondary clarifiers are
dewatered by lime addition, filter presses and centrifuge, and then incinerated in multiple hearth
incinerators. The inert ash is hauled by truck to a landfill.
Baffles installed in wastewater contact basin (empty) to achieve anoxic and aerobic conditions for
enhanced biological nutrient removal at Noman Cole PCP.
-59-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Wastewater contact basin in operation at Noman Cole PCP
Operational considerations:
The combination of biological nutrient removal, chemical addition with tertiary clarification
and filtration effectively reduces total phosphorus concentrations to well below the 0.18 mg/1
permit limitation. Other pollutants such as BOD, TSS and fecal coliform are also reduced to
very low levels through these treatment processes.
The amount of ferric chloride added in the tertiary clarifier to remove phosphorus has been
reduced since biological phosphorus removal was implemented. The ferric chloride dosage
before installation of biological nutrient removal was 18 to 20 mg/1. The concentration used
now is down to 9 to 10 mg/1.
The treatment processes are continuously being evaluated and optimized by staff with the goal
of consistently meeting permit limitations in the most cost effective manner.
Treatment upgrades necessary to meet the new nitrogen limitation are currently being
considered. It is likely that methanol addition and other changes to the biological treatment
train will be made to enhance nitrogen removal from wastewater.
Opportunities to reuse the high quality final effluent for irrigation or as cooling water are
being considered.
The Noman Cole annual operating budget is reported to be approximately $18 to $20 million.
Ferric chloride costs in 2005 were about $180,000.
-60-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Empty tertiary clarifier at Noman Cole PCP
-61-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Blue Water Technologies, Inc- Full scale pilot facility installed at the Hayden
Area Regional Wastewater Treatment Plant
Contact Information:
Hayden Area Regional Wastewater Treatment Plant
10108 North Atlas Road
Hayden, ID 83835
Blue Water Technologies, Inc:
10108 10450 North Atlas Airport Road
Hayden, ID 83835
Phone No 208-209-0391
Website: www.blueh2o.net
NPDES Permit: No. ID0026590, expiration date 02-NOV-2004
Design capacity of Hayden WWTP: 1.65 mgd
Receiving water: Spokane River
Monthly sewer use fee: Company representatives estimate that were the Blue PRO phosphorus
removal system added to the existing Hayden WWTP as tertiary treatment, the residential sewer
use fee would increase by only $1.20 / month to cover all costs of construction and operation.
Company representatives estimate the capital cost for the Blue PRO phosphorus removal system
as tertiary treatment is $178,000 for a 1-mgd treatment plant and $494,000 for a 3-mgd treatment
plant.
Facility Description:
The Hayden WWTP is operated by the Hayden Area Regional Sewer Board, serving the greater
Hayden, Idaho, area. The permitted plant flow is 1.65 mgd. All of the treated wastewater is
utilized for silvacultural irrigation during the warm, dry summer period. During the other times
of the year, WWTP effluent is discharged into the Spokane River. The quality of the Spokane
River and Long Lake are documented as being impaired by excessive loading of nutrients during
the summer period. An intensive water quality evaluation effort by the State of Washington
determined that phosphorus loading from the point source dischargers must be significantly
reduced to restore water quality. A TMDL is currently being developed by the state which will
specify very low wasteload allocations for discharges into the river.
Treatment at the Hayden WWTP consists of screening and grit removal; oxidation ditches (2)
with mechanical mixers; secondary clarification (3); and chlorine disinfection. Removed solids
are aerobically stabilized and dewatered by a belt filter press. Although the Hayden WWTP is
capable of providing treatment to nitrify ammonia, it is typically not operated in a nitrification
mode during the summer months when the effluent is land applied.
-62-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Blue Pro filtration at the Hayden Wastewater Research Facility:
In 2004, Blue Water Technologies, Inc and the University of Idaho, in conjunction with the
Hayden Area Regional Sewer Board constructed a full scale wastewater research facility to
develop and test their treatment system. This installation is called the Hayden Wastewater
Research Facility (HWRF). HWRF uses secondary effluent from the WWTP prior to chlorine
addition and has the capacity to treat about one fourth of the total plant discharge.
Concentrations of phosphorus in the Hayden WWTP influent are typically about 7 to 9 mg/1.
After secondary treatment the concentration of total phosphorus in the Hayden secondary effluent
(without Blue PRO in operation) is typically about 4 mg/1. Since one purpose for testing this
technology was to demonstrate how well it would perform as an add-on tertiary treatment to a
secondary WWTP, the Hayden facility represented a good choice to test this technology.
Movina Bed Sand Filters
Water enters at the top left
of the diagram and is fed to
distribution arms at the
bottom of the bed. It then
moves upflow through the
sand bed. After filtration
clean water leaves from the
top of the filter.
Sand moves down by
gravity. An airlift returns
the sand to the top of the
filter through a central
assembly.
A washbox at the top of the
filter separates sand from
waste particles. The sand
falls back to the top of the
bed. The waste leaves in a
reject line.
Cutaway diagram of Centra-Flo filter at Blue PRO installation at Hayden HWRF
-63-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
The Blue PRO technology combines co-precipitation and sorption to remove both particulate and
soluble phosphorus. Through these processes, some phosphorus is precipitated and removed from
water as it moves upward though the sand media. At the same time, some phosphorus is adsorbed
onto the hydrous ferric oxide coated sand. This adsorption mechanism allows the process to
achieve very low concentrations of phosphorus in the effluent. The phosphorus is then removed
from the sand through abrasion and separated in the sand washer at the top of the filter. The
treatment process installed at the HWRF is composed of:
- a pre-reactor where coagulant (ferric sulfate) is added and mixed with the secondary
effluent;
two continuous backwashing, upflow sand bed filters. The size of each filter is 14 feet
deep, with a surface area of 50 square feet. The filters can be operated as single-pass or
sequentially as a two-stage filtration system. The reject stream (around 7-8% of the flow
to the filters) is recycled to the headworks of the Hay den WWTP.
A long-term, steady-state study was conducted from December 2005 through February 2006
using 0.25 mgd of the Hay den secondary effluent. Blue PRO was operated as a two-single-pass
stage filtration system in December and as a two-stage filtration system in January and February
during the study, although the second stage was not optimized until halfway through December.
The reject stream (containing phosphorus and solids removed in the filters) returned to the
WWTP headworks were observed to cause the phosphorus removal efficiency through the
secondary process to improve significantly. This is likely the result of dosing the WWTP influent
with the ferric compound used in the Blue PRO process. Concentrations of total phosphorus in
the secondary effluent were observed to drop from 4 mg/1 to about 1 mg/1 during the steady state
study. The monthly averages of total phosphorus in the Blue PRO effluent obtained during this
steady-state study are:
- 0.036 mg/1 in December (second stage filtration not optimized)
0.009 mg/1 in January
0.016 mg/1 in February
The average effluent TSS concentration using two-stage filtration during the study was about 1
mg/1. Considering all data from 2005 through 2007, the average phosphorus result was 0.014
mg/L TP, with a standard deviation of 0.006 mg/L. Based on the results of long term testing,
Blue Water representatives state their phosphorus removal system can consistently achieve an
effluent quality of less than 0.030 mg/1 total phosphorus. This performance may vary when
applied to the effluent of a different WWTP. Mobile pilot treatment facilities have been
constructed and deployed to test the Blue PRO treatment process at other WWTPs. Results
similar to those demonstrated at the HWRF have been achieved in these pilot studies.
A next-generation technology termed "Blue CAT" is currently in operation at HWRF. This
patent-pending process adds an advanced oxidation component to the base Blue PRO process,
achieving oxidation potentials up to 875 mV. In addition to improving phosphorus and solids
removal over Blue PRO, this new technology adds disinfection to <2 cfu/100 mL and destructive
removal of emerging micropollutants, such as endocrine disrupters, pharmaceuticals, and
pathogens. The Blue PRO long-term, steady-state study report and other information about the
Blue PRO phosphorus removal system are available from the Blue Water Technologies, Inc.
website: www.blueh2o.net. Attributes claimed by this treatment system include:
-64-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
high efficiency, removing 99%+ of TP from municipal wastewater,
low chemical dose, typically 6-10 mg/L Fe
continuously flowing filtrate - no interruption for backwashing,
low capital, operating, and maintenance costs (total for 1 MOD and 1 pass : less than
$34.7300/lb of P removed),
minimal sludge production, may improve sludge quality and reduce handling costs,
works effectively without pH adjustment,
highly tolerant of interfering water chemistry - wide usage
significantly lowers turbidity and BOD (40% BOD removal and 80% TSS removal during
the steady-state study),
does not affect transmissivity for UV disinfection,
mobile treatment units available,
arsenic, selenium, and heavy metals such as zinc may also be removed.
the Blue PRO tertiary treatment may also be adapted to denitrify through the filter(s).);
installations achieve <3 mg/L total nitrogen.
-65-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
CoMag Technology - Concord Wastewater Treatment Plant
Contact Information:
Concord Public Works Water/Sewer Division
135 Keyes Road
Concord, MA 01742
CoMag Process
Ray Pepin, Senior Engineer
Cambridge Water Technology (CWT)
Suite 100
41 Hutchins Drive
Portland, Maine 04102
207-774-2112x3349
NPDES Permit: No. MA0100668, expiration date 28-FEB-2011
Design capacity: 1.2 MGD as average daily flow and 4.0 maximum daily flow
Receiving water: Concord River
Facility Description:
The existing Concord WWTP was built in 1986 and has a 1.2 mgd monthly average annual
permitted discharge flow and discharges to the Concord River. Treatment through this WWTP
currently consists of headworks, primary settling; trickling filters; secondary clarification; sand
filters; and chlorine disinfection. Water quality of the Concord River is impaired, partially
because of excessive amounts of nutrients entering the river. The seasonal total phosphorus
effluent limitation which applies from April to October was lowered from 0.75 to 0.2 mg/1. The
existing facility could only produce an effluent with a TP concentration of 0.6 to 0.7 mg/1 by
adding alum in advance of the secondary clarifiers. Therefore, a plant upgrade was needed to
meet the proposed phosphorus limit and restore the quality of the receiving water.
The Concord WWTP is currently undergoing upgrade construction which, in addition to installing
tertiary treatment for phosphorus removal (CoMag), will improve the headworks, provide a
new sludge dewatering process and switch from chlorine to UV disinfection. The tertiary process
specification also required that the process be capable of meeting permit limits with one
CoMag clarifier offline at maximum daily flow. The budget cost for the entire upgrade is $9.7
million, of which the CoMag process itself is less than 1/3 of the installed cost. The CoMag
process supplier has certified that its treatment process will be capable of consistently achieving
an effluent total phosphorus concentration of <0.05 mg/1.
-66-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
CoMag Treatment Process:
Polymer
it Water
Polishing
Magnet
Magnetite
Recovery
Drum
To Sludge
Processing
CoMag is a "magneto-chemical" wastewater treatment process that incorporates the use of finely
divided magnetic ballast to bind precipitated phosphorus and other fine particulates. The
technology evolved from the minerals processing industry and all unit operations have been
utilized for many years. Magnetite provides a "magnetic ballast seed" that when mixed with alum
and polymer increases both flocculation and settling rates. These properties reduce the tank sizes
necessary to remove the floe from wastewater. Since the floe particles are attracted to a magnet,
High Gradient Magnetic Separation (HGMS) is used for final effluent "polishing filtration" rather
than traditional sand filtration or membrane systems. The unit area flow rates that can be treated
through the HGMS are claimed to be 50 times greater than those of traditional filters. The ballast
seed is recovered from removed solids and from the effluent.
The CoMag process was selected for installation at the City of Concord because long-term pilot
testing demonstrated its ability to achieve high phosphorus removal efficiencies at comparatively
low costs. Other factors that prompted the Concord WWTP decision to install CoMag
included:
-67-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Reduced chemical doses are required to achieve low effluent total phosphorus
concentrations, resulting in lower operational costs.
CoMag utilizes simple clarifiers that are one-tenth the size of conventional clarifiers and
does not require lamella style tubes which can plug or foul, thereby reducing capital costs
and footprint requirements.
The magnetic separator has a footprint 2 to 5 percent of the size required for conventional
filtration processes.
- Ballasted sludge is very dense and cohesive, with little carry over of pin floe from the
clarifier, even at high overflow rates, thereby allowing CoMag to handle wide variations
in flows and loads.
- Ballasted sludge settleability is dependable and predictable.
- Ballast recycling and recovery is highly efficient and minimize ballast usage.
The CoMag process has proven to be effective in removing TSS, metals, color,
turbidity, pathogens and other pollutants.
- The process is simple and robust. All maintenance items are easily accessible and readily
available. No specialized tools or training are required to operate or maintain the process.
* Information about CoMag was provided by company representatives at the Concord WWTP
or extracted from the article "CoMag Process Achieves Low Effluent Total Phosphorus Levels
While Reducing Footprint and Cost" by Steve Woodard.
-68-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
LOTT Budd Inlet Wastewater Treatment Plant
Contact Information:
LOTT Budd Inlet Treatment Plant
500 Adams Street N.E.
Olympia Washington 98501-6911
NPDES Permit No. WA0037061, expiration date SEP-30-2010
Design capacity: 28 mgd
Receiving water: Budd Inlet (South Puget Sound)
LOTT Budd Inlet Treatment Performance Summary:
Parameter
Total Inorganic
Nitrogen
BOD
TSS
NPDES
Limitation
* 3 mg/1
* 9 mg/1
30 mg/1
Average of
monthly
averages
2.2 mg/1
4. 17 mg/1
7. 15 mg/1
Range of monthly
averages**
1.23 to 2.81 mg/1
2. 14 to 8.66 mg/1
2.75 to 12.3 mg/1
Maximum reported
measurement (date)**
2.81 mg/1 (4/04)
16.5 mg/1 (5/06)
21.3 mg/1 (3/06)
Reporting
period
4/03 to 9/06
4/03 to 9/06
1/03 to 9/06
* Seasonal limitation
** Data from period when seasonal limitations apply
Monthly residential sewer fee: $25.50
LOTT Budd Inlet WWTP Treatment Schematic:
-
2nd Anoxic
/ Final Air
^r=
1st Anoxic Basin
Primary
Effluent
-69-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
Facility Description:
The LOTT Budd Inlet Treatment Plant provides advanced treatment of wastewater collected from
a service area that includes the cities of Lacey, Olympia and Tumwater plus portions of Thurston
County. These entities form the LOTT Alliance which operates the regional WWTP. Treated
effluent is discharged into the marine waters of Budd Inlet which is located at the southern end of
Puget Sound. This part of Puget Sound is poorly flushed and is very sensitive to nutrient loading,
especially during the late spring through fall period. Excessive nutrient loading is blamed for
low dissolved oxygen and excessive aquatic plant and algae growth in these waters. A TMDL is
currently under development by Washington State for this water body which is expected to
establish wasteload allocations (WLAs) for the Budd Inlet Treatment Plant as well as for other
sources of nutrient loading. Although these WLAs have not yet been determined, it is a fact that
Budd Inlet does not have any capacity for additional nutrient loading during the critical warm
weather season.
The LOTT facility has undergone many changes since it was upgraded to provide secondary
treatment in 1982. During this time most of the storm water collection systems have been
separated from the sewage collection system, although a small portion in the downtown Olympia
sewer is still a combined system. The original UNOX wastewater treatment basins were
converted and additional tankage built to provide anoxic, aerobic; second anoxic and final aerobic
wastewater contact areas necessary to accomplish enhanced biological nutrient removal (EBNR)
of nitrogen. A high internal recycle rate of about 4:1 is maintained to provide adequate contact
time for wastewater treatment through EBNR. This recycle rate means that for every 10 mgd of
wastewater influent treated about 50 mgd is routed through the treatment system. The mixed
liquor suspended solids concentration is maintained at about 1800 mg/1 in the contact basins.
This represents a solids retention time of about 20 days. Many other improvements to improve
treatment efficiency at the LOTT plant are currently under construction or are being planned.
-70-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
Secondary clarifiers undergoing upgrade construction at LOTT's Budd Inlet Treatment Plant
(2006)
In addition to primarily domestic wastewater, LOTT received high strength wastewater from the
Olympia brewery until that facility closed about three years ago. The resulting changes to the
character of the influent wastewater required significant adjustment in operation of the WWTP.
One associated change was that LOTT began adding methanol to provide food for the bacteria
necessary to accomplish denitrification of the wastewater. Additional adjustments to wastewater
recycling within the treatment system and to operation of the aeration basins have maintained
excellent nitrogen removal efficiency. With the operation experience gained over time, these
adjustments have significantly reduced the need to add methanol. At the time of the EPA visit to
the LOTT WWTP, continuous monitors indicated that the total inorganic nitrogen level of the
final effluent was less than 1 mg/1 (0.1 mg/1 NH3-N + 0.59 mg/1 NO3-N + 0.1 mg/1 NO2-N = 0.79
mg/lTIN).
Treatment at LOTT consists of: flow into an influent equalization basin (2.25 mgd); screening;
grit removal; primary clarification; EBNR (methanol is added to the second anoxic basin);
secondary clarification and ultraviolet disinfection. Removed solids are routed to dissolved air
flotation thickeners, stabilized in anaerobic digesters, and dewatered by centrifuge before being
disposed by land application. Centrate from the centrifuge is metered back into the primary
effluent.
A portion of the LOTT effluent is reclaimed and utilized for irrigation of public lands. The final
effluent destined for reuse is provided filtration through single-stage, continuous back-washing
Parkson sand filters. These filters are each 14 feet deep and configured in three banks of two
-71-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus April 2007
EPA Region 10
filters. Polyaluminum chloride (PAC1) is added to aid filtration effectiveness. Additional
disinfection is provided by chlorination.
Planning for the Future:
The rapid development and population growth in the South Puget Sound service area required the
LOTT partners to carefully plan to meet future wastewater treatment needs. The marine waters of
Budd Inlet are already impaired by excessive loading of nutrients and this situation precludes the
option of simply increasing treatment capacity and discharge at the main plant. Although the
existing LOTT plant already achieves about the best nitrogen removal that current biological
treatment technology can accomplish, there is simply no assimilative capacity in South Puget
Sound for additional nutrient loading during the critical period.
LOTT implemented numerous water conservation programs in the service area and began
promoting use of reclaimed wastewater for irrigation and groundwater recharge. LOTT also
decided to meet the need for additional wastewater treatment capacity by constructing 'satellite'
facilities. These satellite wastewater treatment plants are located in areas needing sewer service
where land is still available to accommodate reuse of the effluent. Advanced treatment is
provided at the satellite WWTPs to meet state requirements for reclaimed wastewater such that it
may be utilized for groundwater recharge and/or irrigation during the dry summer months. The
first of the planned satellite treatment plants is a two mgd membrane bioreactor treatment plant
that was placed in operation in 2006. The membranes are hollow fiber filaments produced by
U.S. Filter Corporation. Treated effluent from this satellite WWTP is reclaimed and used for
groundwater recharge. Solids removed during treatment at the satellite plant are returned to the
sewer main for handling at the Budd Inlet WWTP. Land was recently purchased by LOTT for
construction of a second satellite plant.
Operational Considerations:
The five trains of aeration basins have excess capacity and only two of the five basins are
typically needed to treat wastewater flows during normal dry weather. The aeration
delivery system installed in these basins is somewhat limiting to operational control.
Adjusting aeration (DO setpoints) has significantly reduced the need to add methanol as
supplemental feed for bacteria necessary for nitrogen removal. Methanol is only fed
during nighttime hours. Methanol currently costs about $1.60 per gallon (delivered to the
plant).
Nitrate concentration measured in the aeration basin effluent is used for process control
for determining how much food additive (methanol) to use.
Oxidation/reduction meters are installed and connect to the SCADA system to assist with
operational control.
A high internal recycle rate (4 gallons recycled: 1 gallon treated) is necessary to achieve
the desired effluent quality. The electricity and maintenance costs associated with internal
recycle pumping are quite expensive.
-72-
-------
Advanced Treatment to Achieve Low Concentration of Phosphorus
EPA Region 10
April 2007
24 inch internal recycle piping at LOTT's Budd Inlet WWTP
There have been some problems with filamentous bacteria (Microthrix parvicella).
Operators are experimenting with polyaluminumchloride (PAX) to control this organism.
Sludge collectors in the secondary clarifiers are being upgraded.
An operational goal is to keep total inorganic nitrogen levels in the final effluent under 2
mg/1 to insure that the 3 mg/1 permit limitation is met consistently.
-73-
------- |