Washington State Department of Ecology Agreed Order to Conduct Nitrogen Discharge Reduction Pilot ProjectSTATE OF WASHINGTON
DEPARTMENT OF ECOLOGY
Northwest Regional Office • 3190160th Avenue SE • Bellevue, Washington 98008-5452 • (425) 649-7000
711 for Washington Relay Service • Persons with a speech disability can call (877) 833-6341
October 26, 2020
The Honorable Michael Nelson, Mayor
City of Edmonds
121 5th Avenue North
Edmonds, WA 98020
Re: Agreed Order
Dear Mayor Nelson:
Order Docket #
18226
Site Location
City of Edmonds Wastewater Treatment Plant
200 2nd Ave. South
Edmonds WA 98020-3578
Enclosed is a copy of the signed and effective Agreed Order number 18226. The enclosed Order
may not be appealed. The Order is effective as of October 26, 2020.
If you have any questions concerning the content of the document, please contact Stephanie
Allen at (425) 295-5760 or by email at sa11461 ec .wa. ov.
Sincerely,
:F0helMc'CLrea'
Water Quality Section Manager
Northwest Regional Office
Enclosure: Agreed Order # 18226
Sent by Certified Mail: 9171 9690 0935 0233 2083 79
ecc: Pamela Randolph, Plant Manager, City of Edmonds
Phil Williams, Public Works & Utilities Director, City of Edmonds
Stephanie Allen, Facility Manager, Ecology
Laura Fricke, Municipal Unit Supervisor, Ecology
Greg Lipnickey, Municipal Compliance Specialist, Ecology
Central Files: City of Edmonds WWTP; Permit No. WA-0024058; WQ 6.4
STATE OF WASHINGTON
DEPARTMENT OF ECOLOGY
IN THE MATTER OF AN
ADMINISTRATIVE ORDER
WITH:
City of Edmonds
The Honorable Michael Nelson
To: The Honorable Michael Nelson, Mayor
City of Edmonds
121 5th Ave. N.
Edmonds, WA 98020
AGREED ORDER
DOCKET # 18226
Order Docket # 18226
Site Location City of Edmonds Wastewater Treatment Plant
200 2nd Avenue South
Edmonds, WA 98020-3578
I. INTRODUCTION
This is an Agreed Order between the Department of Ecology (Ecology) and the City of Edmonds
(City) to conduct a pilot project in compliance with the City's NPDES Permit No. WA-0024058
(Permit), Chapter 90.48 Revised Code of Washington (RCW) and Chapter 173-220 Washington
Administrative Code (WAC) by taking certain actions which are described below to reduce
nitrogen discharged at the City's Wastewater Treatment Plant (WWTP).
II. RECOGNITION OF ECOLOGY'S JURISDICTION
This Agreed Order is issued pursuant to the authority vested in Ecology by the Federal Water
Pollution Control Act (FWPCA), 33 U.S.C. sec 1311, et seq. and Chapter 90.48 Revised Code of
Washington (RCW).
RCW 90.48.030 provides that Ecology shall have the jurisdiction to control and prevent the
pollution of streams, lakes, rivers, ponds, inland waters, salt waters, water courses, other surface
and underground waters of the state of Washington.
RCW 90.48.120 authorizes Ecology to issue administrative orders requiring compliance
whenever it determines that a person has violated or created a substantial potential to violate any
provision of Chapter 90.48 RCW or fails to control the polluting content of waste to be
discharged to waters of the state
The City agrees to undertake all actions required of it by the terms and conditions of this Agreed
Order and not to contest Ecology's jurisdiction and authority to administer this Agreed Order.
The City agrees not to appeal this Agreed Order.
Agreed Order Docket # 18226
City of Edmonds Wastewater Treatment Plant
Page 2 of 7
Nothing in this Agreed Order shall in any way relieve the City of its obligations to comply with
the requirements of its Permit. Nor shall anything in this Agreed Order limit Ecology's authority
to enforce the provisions of the aforementioned Permit.
.III. FINDINGS OF FACT
Ecology's determination to issue an Agreed Order is based on the following facts.
The City operates a conventional secondary wastewater treatment plant consisting of a
headworks with screening, primary clarifiers, aeration basins for biological treatment,
secondary clarifiers, and chlorine disinfection. Treated and disinfected effluent flow into
the main basin of Puget Sound through an outfall. The City's WWTP treats flow from
the City of Edmonds, King County, Olympic View Water and Sewer District, Ronald
Sewer District and the City of Mountlake Terrace (collectively called `partners'). The
plant has a design capacity of 11.8 MGD average monthly flow. While the City of
Edmonds operates the WWTP, the design capacity is owned by the partners.
2. The Salish Sea Model has shown that nutrients discharged from wastewater treatment
plants contribute to low dissolved oxygen (D.O.) levels, below state water quality criteria,
in the Salish Sea. Nitrogen is the limiting nutrient in the Salish Sea waters. More
specifically, total inorganic nitrogen (TIN), the sum of nitrate -nitrite and total ammonia,
is the form of nitrogen more available for algal growth that drives eutrophication and the
dissolved oxygen impairment. Early model runs ("Bounding Scenarios") confirmed that
circulation within the inner basins of Puget Sound distributes a portion of pollutants
throughout the waters of the Puget Sound. Discharges in one basin may affect the water
quality in other basins.
The City's discharge contains inorganic nitrogen. The inorganic nitrogen in the City's
discharge has reasonable potential to contribute to far -field water quality impacts. At this
time, including a numeric water quality based effluent limit (WQBEL) for nitrogen in the
City's NPDES permit is infeasible. This is due to the additional modeling necessary to
quantify both the City's far -field water quality effect and the corresponding effluent limit
necessary to prevent an exceedance of the D.O. standard.
4. The City's NPDES Permit expired on October 31, 2019 and remains in effect under
administrative extension (WAC 173-220-180). Ecology is developing a Nutrients
General Permit applicable to nearly 70 domestic WWTPs discharging to marine and
estuarine waters of Puget Sound. The Nutrients General Permit will focus on controlling
nutrients and will work in conjunction with the WWTPs' existing individual permits.
5. Prior to the issuance of the Nutrients General Permit, the City plans to conduct a pilot
project to evaluate potential nitrogen reduction at the WWTP. The City's WWTP faces
limitations incorporating nutrient control into its process. The City constructed the
existing facility using the entire available footprint, so options for expanding treatment at
the existing site are limited. In good faith, the City decided to evaluate retrofitting
existing processes with an in -situ nitrogen reduction technology. The City will conduct a
pilot project of a mobile organic biofilm (Nuvoda MOB) process with a biofilm media, as
Agreed Order Docket # 18226
City of Edmonds Wastewater Treatment Plant
Page 3 of 7
a new and developmental technology. The duration of the pilot project will run
concurrently with the development of the Nutrients General Permit, with final results
reported in 2021. See project schedule below.
6. Ecology intends to administratively extend the conditions of the City's current NDPES
permit until the pilot project is complete and Nutrients General Permit issued. If
Ecology does not issue a Nutrients General Permit before October 31, 2024, Ecology
will incorporate appropriate nutrient controls into a reissued individual Permit.
7. Ecology accepted the City's Technical Memo dated May 1, 2020 for the WWTP
Nuvoda MOB Process Evaluation and Trial on June 4, 2020. The document includes the
sampling and analysis program, which complies with provisions of G1-5.4 of Ecology's
Criteria for Sewage Works Design (Orange Book).
8. The pilot project will be carried out in one of the plant's three treatment trains. The City
anticipates that one train will be capable of treating dry weather flows up to 5 MGD.
Limiting the project to a single train provides greater flexibility to stress the MOB process
but can temporarily limit hydraulic capacity. Stress testing likely won't be possible until the
wet weather months when flow reaches above 5 MGD. If, during the trial period, the City
anticipates exceeding the hydraulic capacity of the pilot treatment train, the City will route
the excess flows through the plant's conventional active sludge process.
9. The pilot project began July 2020 and has an anticipated end date of April 30, 2021.
IV. ACTIONS REQUIRED
IT IS AGREED that the City of Edmonds shall take the following actions by the dates set forth
below and notify Ecology as early as practicable. These actions are necessary to satisfy the
requirements of Chapters 173-220 WAC, 173-50 WAC, and 173-240 WAC. The City of
Edmonds has participated in defining these actions and the dates by which they shall be
completed.
The pilot project has an anticipated duration of approximately nine months. The project may need
to conclude earlier if unforeseen problems are encountered. Similarly, given the experimental
nature of the pilot project, the project schedule may require adjustment in the event of unforeseen
developments. The City of Edmonds shall notify Ecology as early as practicable of adjustments
that may impact the below deliverable.
No later than August 31, 2021, the City shall submit a final report to Ecology presenting
the results of the project and verifying the developmental or new technology complies
with provisions of G 1-5.4 of Ecology's Criteria for Sewage Works Design (Orange
Book). The final report may be submitted as a Technical Memo or Engineering Report, or
both. "Engineering Report" refers to a single preliminary engineering document
developed for the City that thoroughly examines the technical and administrative aspects
of the project while meeting the minimum requirements of WAC 173-240-060.
Submit the final report through the Water Quality Permitting Portal -Permit Submittals
application by the date specified in this Agreed Order.
Agreed Order Docket #18226
City of Edmonds Wastewater Treatment Plant
Page 4 of 7
Lab Accreditation and Data Quality:
Provisions of G l -5.4 of the Criteria for Sewage Works Design "Orange Book" require
that all monitoring data except flow, temperature, settleable solids, conductivity and pH
shall be prepared by a laboratory registered or accredited under the provisions of
Chapter 173-50 WAC. The City's lab is accredited for several parameters being
monitored during the pilot project. Those include Total Suspended Solids (TSS), pH,
and Carbonaceous Biological Oxygen Demand (CBOD). The City's lab is not
accredited for the following parameters to be monitored during the pilot project:
Chemical Oxygen Demand COD, Ammonia, Nitrate (NO3) and Nitrite (NO2).
Table 8 of the City's Technical Memo, W WTP Nuvoda MOB Process Evaluation and
Trial, presents testing methods for the analysis of COD, Ammonia, NO3 and NO2. The
City has decided to use Hach methods and products for the monitoring program. Hach
methods for COD, Ammonia, NO3 and NO2 are accepted by the EPA as equivalent to
EPA methods (40 CFR 136.6) for use in compliance monitoring:
httos://www.hach.com/epa.
Until the City's lab is accredited for these parameters, IT IS AGREED the City will split
samples weekly, at the influent and effluent, for COD, Ammonia, NO3 and NO2
(effluent only). Consistent with Ecology's Information Manual for Treatment Plant
Operators, a week is defined as a seven-day period beginning on Sunday and ending on
Saturday. The City will send the split samples to an accredited lab, compare the City's
lab results with the accredited lab results and report this to Ecology. AmTest is the lab
currently contracted, but an accredited laboratory of the City's choice is acceptable. For
each parameter, if three consecutive comparisons are within 10%, Ecology will accept
the City -only lab results for the subject parameter, for the remainder of the pilot project.
If the difference in results are greater than 10%, the City will submit to Ecology the
following for the subject parameter:
• Method procedures
■ QC/QA procedures
• Bench sheets
• Raw data, calculations and computer data entry
The City will continue with the split sample comparisons, until the results of 3
consecutive samples -are within- I0%,-or--until-Ecology-provides-written-approval based
on a review of the above submittals, whichever comes first. If the City reports split
sampling comparisons at a frequency greater than once per week, a comparison of
weekly averages will replace a comparison of single sampling events for that week.
The City will submit the lab comparison results to the City's NPDES Permit manager,
Stephanie Allen, within one week of the City's receipt of the data from the external lab,
following the effective date of this Agreed Order.
Agreed Order Docket # 18226
City of Edmonds Wastewater Treatment Plant
Page 5 of 7
Attachment A is the City's Technical Memo dated May 1, 2020 for the WWTP Nuvoda MOB
Process Evaluation and Trial.
V. PROGRESS REPORTING
The City of Edmonds shall provide progress reports to Ecology on a monthly basis for the below
items:
• Summary of any changes to project scope.
• Summary of any NPDES permit reporting resulting from the pilot project.
■ Monthly monitoring data for parameters sampled at the influent and effluent consistent
with S2.A of the NDPES permit.
Progress reports shall include applicable dates, attachments and/or references. The first report
must be submitted by the 15th day of the month following the effective date of this Agreed Order
and monthly for the duration of the project. Submit the progress reports through the Water
Quality Permitting Portal -Permit Submittals application.
VI. FORCE MAJEURE
If a milestone set forth in the Project Schedule is not met or is likely not to be met, the City shall
submit to Ecology, in writing, any reasons for failing to meet the specific milestone as soon as
they are reasonably aware of the delay. The City shall not be held responsible for a delay if the
City has demonstrated a good faith effort to meet the deadline and the delay is attributable to
delays outside of the City's control ("force majeure"). For purposes of this Agreed Order, force
majeure shall mean only those occurrences or events beyond the control of the City, including
acts of God, natural disasters, or action or lack of action by government agencies or third parties
on permit, right-of-way, or other requests for required authorizations timely submitted by the
City.
VII. EFFECTIVE DATE
This Order is effective on the date the agreement has been signed by both parties.
Vill. TERMINATION OF THE AGREED ORDER
Upon completion by the City of Edmonds of the actions identified in Section IV of this Agreed
Order and issuance of a Notice of Compliance by Ecology, the requirements of this Agreed
Order shall be deemed to be fulfilled and shall have no further effect on the City of Edmonds.
IX. DISPUTE RESOLUTION
If a dispute arises between Ecology and City of Edmonds regarding any noncompliance with
this Agreed Order, the parties shall attempt to resolve the dispute by informal resolution. A
dispute shall be considered to have arisen when one party notifies another, in writing, that there
is a dispute. If the parties cannot resolve the dispute informally within thirty (30) days, City of
Edmonds shall serve on Ecology a written Statement of Position. Within thirty (30) days after
Agreed Order Docket # 18226
City of Edmonds Wastewater Treatment Plant
Page 6 of 7
receipt of City of Edmonds Statement of Position, Ecology shall provide City of Edmonds with
a final administrative decision.
X. ENFORCEMENT --►-
Failure to comply with this Agreed Order may result in the issuance of civil penalties or other
actions, whether administrative or judicial, to enforce the terms of this Agreed Order. Ecology
may consider enforcement discretion if the City has demonstrated a good faith effort to meet the
terms of the agreement.
XI. THIRD PARTY RIGHT TO APPEAL
By signing this Agreed Order, City of Edmonds may not appeal this Agreed Order, however, a
third party may.
A party other than City of Edmonds has a right to appeal this Order to the Pollution Control
Hearing Board (PCHB) within 30 days of the date of receipt of this Order. The appeal process is
governed by Chapter 43.2113 RCW and Chapter 371-08 WAC. "Date of receipt" is defined in
RCW 43.21 B.001(2).
To appeal you must do both of the following within 30 days of the date of receipt of this Order:
« File your appeal and a copy of this Order with the PCHB (see addresses below).
Filing means actual receipt by the PCHB during regular business hours.
■ Serve a copy of your appeal and this Order on Ecology in paper form - by mail or in
person. (See addresses below.) E-mail is not accepted.
You must also comply with other applicable requirements in Chapter 43.21B RCW and Chapter
371-08 WAC.
Your appeal alone will not stay the effectiveness of this Order. Stay requests must be submitted
in accordance with RCW 43.21B.320.
XII. ADDRESS AND LOCATION INFORMATION
Street Addresses I Mailina Addresses I
Department of Ecology
Attn: Appeals Processing Desk
300 Desmond Drive SE _
Lacey, WA 98503
Pollution Control Hearings Board
1111 Israel Road SW
STE 301
Tumwater, WA 98501
Department of Ecology
Attn: Appeals Processing Desk
PO Box 47608 _ _-
Olympia, WA 98504-7608
Pollution Control Hearings Board
PO Box 40903
Olympia, WA 98504-0903
Agreed Order Docket # 18226
City of Edmonds Wastewater Treatment Plant
Page 7 of 7
XIII. CONTACT INFORMATION
Please direct all questions about this Order to:
Greg Lipnickey
Department of Ecology
Northwest Regional Office
3190-160th Ave. SE
Bellevue, WA 98008
Phone: 425-449-6560
Email: glin461(wecy.wa.gov
X1V. MORE INFORMATION
-W �
• Pollution Control Hearings Board Website
http://www.eluho,wa.gov/Board/PCHB
• Chapter 43.21B RCW - Environmental and Land Use Hearings Office — Pollution
Control Hearings Board
h ttp ://aMs.l eg. wa. go v/RCW /defau It. aspx?cite=43.21 B
• Chapter 371-08 WAC — Practice And Procedure
http://anos.leg.wa.gov/WAC/default.aspx?cite=371-08
• Chapter 34.05 RCW — Administrative Procedure Act
littp://apps.leg.wa.gov/RCW/default.aspx?cite=34.05
• Ecology's Laws, rules, & rulemaking website
https://ecology.wa.gov/About-us/How-we-operate/Laws-rules-rts 1 emaking
XV. SIGNATURES
M' hael Nelson
Mayor
City of Edmonds
Rachel McCrea
Water Quality Section Manager
Northwest Regional Office
Washington State Department of Ecology
10/21 /20
Date
10/26/2020
Date
SIAN S
TECHNICAL MEMORANDUM
Date: May 1, 2020
To: Pamela Randolph, City of Edmonds
From: Tom Giese, PE; Greg Mockos, PE; Casey Bryant, EIT, BHC Consultants, LLC
Subject: WWTP Nuvoda MOBTM' Process Evaluation and Trial
ti ppUL C:
�a x■ �
Thomas Paul Giese Jr., PE
BHC Consultants, LLC
This technical memorandum discusses the nitrogen removal potential of the Edmonds
Wastewater Treatment Plant (WWTP) with the addition of the Mobile Organic BiofilmTM
(MOB1m) process from Nuvoda. This investigation was done as a proof of concept using
Envirosim's BioWin process modeling software. As part of the ongoing Puget Sound Nutrient
Reduction Project, the Washington State Department of Ecology (Ecology) has begun work on a
new general permit that will require WWTPs discharging directly to Puget Sound to achieve
nitrogen removal to a level yet to be determined. Because the Edmonds WWTP discharges
directly to Puget Sound, it will be included in the forthcoming general permit and required to
remove nitrogen in the foreseeable future. The City of Edmonds (City) has decided to
proactively start exploring possible alternatives for achieving nitrogen removal, of which the
Nuvoda MOBTM' process is one such alternative. This alternative is particularly attractive
because of its relatively low cost and overall ease of implementation. This technical
memorandum also discusses how the City will conduct a trial of the Nuvoda MOBM technology
to further assess its effectiveness and how it could be integrated into the existing WWTP.
1. Base Model Calibration
To produce a relatively accurate representation of the Nuvoda MOB'rM process, a baseline
BioWin process model representing current conditions and operations was first prepared and
calibrated to check influent characterization and model assumptions. The baseline process
TECHNICAL MEMORANDUM 1 BHC Consultants, LLC
WWTP Nuvoda MOBTm Process Evaluation and Trial
influent
CC?Nc411 il�i' i `�
model (see Figure 1) was created using record drawings and process operating data provided
by the City from January 2019 to January 2020. The process data was sorted to only consider
time periods in which two aeration basins and two final clarifiers were in use to ensure
consistency with the process model representation.
RAS Nxing Box1 AB1 Z1a ABt Z1bI A81 Z2+ AB7 Z3 AB 1 Ef11uentChannel
Effluent
RASNWng Box2 A82Z1a AB2Z1b A92Z2 A02Z3 AB 2 EBNen(Channel
Blend Tank
Dewafered Sludge
�r
Figure 1 — Baseline BioWin Process Model Diagram
Influent wastewater characterization was based on influent flow and loading data provided by
the City from January 2019 to January 2020, as well as ratios defined in the 2007 Process
Control Improvements Study by Brown and Caldwell (Brown and Caldwell Report). Typical
assumptions were made where these sources did not have applicable or representative
information, such as raw influent chemical oxygen demand (COD) fractions. The ratios in the
Brown and Caldwell Report were based on primary effluent. A comparison of the solids balance
and total solids inventory (inventory in the aeration basins and final clarifiers) from actual data
provided by the City and process model predictions was made to confirm the assumptions and
influent characterization. A summary of the model calibration results are provided in Table 1.
Table 1
Model Calibration Results and Comparison with Actual Values
Parameter
1/1/19 - 4/22/19,
6/27/19 - 9/8/19,
10/11/19 - 10/29/19
BioWin
Values
A
Notes
Effluent
CBOD (mg/L) =
9.2
7.58
-1.6
TSS (mg/L) =
10.7
11.80
1.1
pH =
7.2
6.72
-0.5
Ammonia-N (mg/L) =
20.2
20.42
0.2
Nitrate+Nitrite-N (mg/L) =
I1.0
5.30
4.3
TKN (mg/L) =
1 32.1
21.7
1 -10.4
TECHNICAL MEMORANDUM 2 BHC Consultants, LLC
WWTP Nuvoda MOBT11 Process Evaluation and Trial
'1 -1 *
s
CONSULTANTS
Solids Balance
Primary Effluent TSS (mg/L) =
81
122
50%
See discussion
below
Primary Effluent COD (mg/L) =
333
369
10.8%
_
Per COD data from _
City
3.4
3.44
1.2%
3.4% per Carbon
Primary Sludge TSS (%)
Recovery
SRT =
3.7
3.65
-1.4%
Measured SRT
recalculated
MLSS =
1,555
1,460
-6.1 %
Total Solids Inventory Mass (Ibs) =
19,328
19,607
1.4%
Sec. Clarifier RAS TSS (mg/L) =
6,813
5,411
-20.6%
1 Average RAS TSS
WAS (Ibs/d) =
4,926
4,924
0.0%
As indicated in Table 1 above, there is a significant variation between the model predicted
primary effluent TSS and the measured primary effluent TSS. This is based on the assumed
removal rate of TSS in the primary clarifiers. However, increasing the removal rate yields large
discrepancies in the model predicted solids balance versus measured data. Although primary
effluent TSS can vary substantially from day to day and the April 2007 Process Control
Improvements Study (Brown and Caldwell) suggested higher primary effluent TSS
concentrations, the City collects composite samples four times a week to test for primary
effluent TSS. This would suggest the primary effluent TSS data should be representative. It is
possible that reported values of mean -cell residence time (MCRT) are calculated differently than
in the solids retention time (SRT) in the model. However, the model calculated SRT accounts
for both wasted solids and effluent solids, which is typically representative of MCRT. Because
the source of the discrepancy is currently not known and a higher primary effluent TSS is
conservative with respect to analysis of the secondary process, further changes were not made
to the model calibration at this time. This question will be revisited during the trial period when
more data is available and there is an opportunity to analyze the solids balance further. Further
data on other parameters may impact assumptions that could also affect primary effluent
parameters predicted by the model. For instance, assumptions of influent COD fractions may
account for discrepancies in the primary effluent COD, which are still considered reasonably
close for this level of analysis. Additionally, inclusion of recycled solids from the incinerator ash
scrubber in the model could also impact the solids balance.
Effluent Total Kjeldahl Nitrogen (TKN) values also differed significantly between measured data
and predicted values. Given the small data set, it is difficult to determine if the few higher
TECHNICAL MEMORANDUM 3 BHC Consultants, LLC
WWTP Nuvoda MOB"' Process Evaluation and Trial
measurements of effluent TKN were unusual or assumptions of refractory dissolved organic
nitrogen need to be revisited. These considerations can be verified with collection of additional
data, but do not significantly impact the conclusions of the analysis herein.
Generally, a reasonable calibration with respect to the solids balance is achieved when
predicted values are within 10% of measured values. This criterion is met for all parameters
except for primary effluent TSS (as discussed above) and return activated sludge (RAS) TSS.
Due to uncertainties related to assumptions for COD fractions and TSS removal in the primary
clarifiers, the fact that the rest of the predicted values compare well with observed values, and
because RAS TSS concentration is not a critical parameter, the differences in BioWin process
model predictions and observed data are considered acceptable for this level of analysis, but
will be revisited in more detail after more data has been collected from the Nuvoda trial.
2. MOBTM Modeling
Modeling of the Nuvoda MOB TM process is meant to examine how a trial might perform under
current average flow and loading and how a full-scale installation might perform under design
maximum month flow and loading. Information gained from the technology trial will be used to
update these models to improve accuracy of predictions and help determine how this process
could be integrated into the existing WW'fP.
The MOB TM process was modeled in BioWin based on parameters provided by Nuvoda. BioWin
predicted a slightly thicker biofilm than Nuvoda indicated as typical. Past observations by
Jacobs has indicated recirculation of the kenaf can reduce the biofilm thickness, which suggests
the typical thickness indicated by Nuvoda may be more accurate. Biofilm thickness and mass
can be examined more closely during the trial. The parameters recommended by Nuvoda and
the values used in BioWin are summarized in Table 2. Per Nuvoda, multiple recommended
parameters are estimates and will need to be confirmed during the trial.
Table 2
MOB TM Modeling Parameters
Parameter
Fill Percentage
Nuvoda
Recommendation
Input to
BioWin
1.26%
1.26%
Specific Volume (ft3/ft3)
Specific Area (ft2/ft3)
1
1
6,092
6,092
Number of Layers (through film)
N/A
3
TECHNICAL MEMORANDUM 4 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
Boundary Layer Thickness (um)
N/A
1 50
Biofilm Thickness (mm)
0.30
0.36
Min. Biofilm Concentration for streamer formation (gTSS/m2)
10
1 10
The Nuvoda MOB TM process is configured as an integrated fixed film activated sludge (IFAS)
system within the BioWin process model, such that the carrier media is contained within each
basin. As a result, the effect of the kenaf particles on the clarifier is not modeled, as the IFAS
system assumes the biofilm carriers do not leave the basins. However, due to rapid settling of
the kenaf particles, this was still considered to be reasonably representative, since the kenaf
particles should have no adverse effect on settling of mixed liquor suspended solids (MLSS).
Therefore, the settling of suspended growth MLSS will still be the controlling factor with respect
to clarifier loading. In fact, Nuvoda indicates that the presence of the kenaf particles should
improve settling characteristics of the MLSS.
Settling of MLSS in the BioWin process model was based on 30-minute settleometer and sludge
volume index (SVI) data provided by the City. The 90th percentile of SVI values for the
calibration period is approximately 400 mL/g. This was converted to a diluted sludge volume
index (DSVI) to differentiate between poor sludge settleability due to a low settling velocity or
hindered settling (i.e., too much sludge). The 90th percentile of DSVI values for the calibration
period is approximately 270 mL/g. This DSVI value was used to determine the maximum
Vesilind settling velocity and the Vesilind hindered zone settling parameter, which can be input
into the BioWin process model to generate a state point analysis for settling of the solids in the
final clarifiers.
Nuvoda has indicated a positive change in settling characteristics is expected with the
implementation of the MOB TM process. This includes the sweeping action of the fast settling
kenaf particles and agglomeration of MLSS with the kenaf particles due to production of
extracellular polymeric substance (EPS) acting as a cationic polymer. Data for the MoorField
Case Study was provided by Nuvoda, which observed an average SVI of about 460 mL/g before
implementation of the MOB TM process. Once the process was installed and the treatment
process acclimated, average SVI values were typically around 50 mL/g. Therefore, in addition
to considering current SVI values, settling parameters associated with an SVI of 100 mL/g were
also considered in the BioWin process model. Based on SVI data collected during the trial, any
improvement in SVI can be correlated to settling parameters within the BioWin process model to
help determine actual final clarifier capacity with the Nuvoda MOBT"" process.
TECHNICAL MEMORANDUM 5 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
3. MOBTm Results
3.1 Current Average Flaw and ,Loading (Trial Period)
A diagram of the BioWin process model representing the Nuvoda MOB TM process trial utilizing
one aeration basin and one final clarifier is shown in Figure 2.
807E NaOH
Influent RASMixing Box Zia Zib Z2 Z3
BlandTank
Dewatarad Sludge
Figure 2 — Nuvoda Trial BioWin Process Model Diagram
E4WentChannal EMuwnt
The predicted performance of the Nuvoda MOB TM process during the trial at current average
flow and loading is summarized in Table 3. This data is preliminary, meaning it is based on
several assumptions that need to be confirmed. Data from the trial will aid in confirming or
modifying assumptions and validating the BioWin model for the Nuvoda MOB TM process.
Table 3
BioWin Results with MOB TM Process at Current Average Flow
Parameter
Quantity
Unit
Influent Flow
4.5
MGD
Waste Activated Sludge
4,820
Ibs/day
SRT
5
days
Effluent Ammonia-N
0.2
mg/L
Effluent TIN
28.1
mg/L
Mixed Liquor Recycle (MLR)
N/A
%Q
Supplemental Alkalinity (50% NaOH)
500
gpd
MLSS
3,580
mg/L
_
RAS Rate
2.44
MGD
TECHNICAL MEMORANDUM 6 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
The SRT in Table 3 is representative of the total solids inventory (aeration basin and final
clarifier) and loss of solids through both wasting and effluent. Nuvoda typically recommends a
suspended growth SRT of around 5 days for the MOB TM process, though has indicated
processes have run at an SRT of up to 8 days. This correlates with past observations by
Jacobs that indicate a 4 to 5 day SRT (avoiding growth of nitrifying bacteria in the suspended
biomass) appears to achieve the best results. Even a 5-day SRT is significantly higher than
what the \NWTP typically operates at currently. As a result, it is expected that sludge production
will be reduced and MLSS will increase, resulting in increased solids loading to the final clarifier,
However, as discussed previously, improvements in sludge settleability and SVI should allow
the final clarifier to handle the increased load.
Because the current configuration of Aeration Basin No. 1 does not allow the formation of
anoxic zones, all zones (except the small RAS mixing box) are aerated. This helps achieve
complete nitrification, but does not allow for significant denitrification. During the trial, tapered
aeration (stepping dissolved oxygen down sequentially through the zones) will be utilized in an
attempt to achieve some level of simultaneous nitrification/denitrification. However, it is
expected that a dedicated anoxic zone will be necessary to reach the levels of denitrification
that will be necessary to achieve a total inorganic nitrogen (TIN) concentration of less than
8 mg/L in the effluent.
The lack of denitrification also prevents recovery of alkalinity, which generates low effluent pH
that can inhibit complete nitrification and violate the NPDES permit. Based on model
predictions, it is estimated that a dose of about 500 gpd of 50% sodium hydroxide would be
needed to maintain effluent pH above 6.5 during the trial to avoid inhibiting nitrification.
Aeration Basin No. 1 has a total diffuser area of 1,298 square feet. The diffuser design for
Aeration Basin No. 1 was based on an average diffuser flux rate of 1.35 standard cubic feet per
minute per square foot (scfm/sf) for average summer conditions and 2.11 scfm/sf for peak
summer conditions. Although product literature for the diffusers suggests a maximum flux rate
of 4 scfm/sf, this may be just for periodic peak conditions. The operation and maintenance
manual suggests a maximum flux rate of 2.15 scfm/sf, which would equate to a total airflow of
about 2,800 scfm. The BioWin model predicts an air demand on the order of 3,000 scfm, which
equates to a flux rate of 2.3 scfm/sf. This potentially slightly higher flux rate is likely not be an
issue for the diffusers, particularly given that the design had diffusers in particular zones
TECHNICAL MEMORANDUM 7 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
CONSULTANTS
operating at higher flux rates. So, it appears there should be enough diffuser capacity in
Aeration Basin No. 1 for the trial. As a single blower has a capacity of about 2,600 scfm, there
should also be sufficient blower capacity.
3.2 Design Maximum Month Flow and Loading
A separate BioWin process model was utilized to predict performance of a full-scale installation
at the design maximum month flow and loading. For this scenario, the BioWin process model
was simplified to depict all three aerations basins as a single basin and all three final clarifiers
as a single clarifier, as shown in Figure 3 below. It is assumed that for all three aeration basins,
Aeration Zone 1 (Zones 1A and 1 B) is operated as anoxic volume to allow for denitrification and
Aeration Basin No. 3 is configured for plug flow similar to Aeration Basins No. 1 and 2. The
Influent
L� Y
filtered BOD concentration entering Zones 1A and 1 B is low, suggesting that these zones are
carbon limited. Supplemental carbon could be added to achieve higher levels of nitrogen
removal. Supplemental carbon could be added in the form of chemicals (e.g., Micro-C or
methanol), or potentially from within the facility (e.g., diverting some influent directly to the
aeration basins), as a significant portion of carbon is removed in the primary clarifiers.
Alkalinity
RAS Mixing Box Zia Zib Z2 Z3
Figure 3 — Full -Scale BioWin Process Model Diagram
Eflluentchannei Effluent
1
A summary of predicted effluent quality and operating parameters for the design maximum
month flow and loading scenario is provided in Tabled This data is preliminary, meaning it is
based on several assumptions that need to be confirmed. Data from the trial will aid in
confirming or modifying assumptions and validating the BioWin model for this scenario.
TECHNICAL MEMORANDUM 8 BHC Consultants, LLC
WWTP Nuvoda MOBT"' Process Evaluation and Trial
Table 4
BioWin Results with MOBT11 Process at Design Maximum Month Flow
Parameter 1 Quantity Unit
Influent Flow
11.87
MGD
Sludge Production
14,330
Ibs/day
SRT
Effluent TIN
5
days
16.2
mg/L
Effluent Ammonia
MLR
MLSS
2.59
mg/L
300
%Q
3,650
mg/L
RAS Rate
7.32
MGD
The BioWin model did not quite predict complete nitrification at a 5-day SRT. However, it is
quite possible that with current assumptions the model is underpredicting the biofilm mass and
associated nitrification. Data collected during the trial will allow refining the model parameters
and could very well yield better nitrification performance than currently predicted.
A potential limiting factor under the maximum month design conditions is the final clarifiers.
Figure 4 illustrates a state point analysis for the final clarifiers based on current SVI values
(using a DSVI of 270 mL/g). The final clarifiers clearly do not have capacity to under these
conditions without some improvement in SVI.
32-..-_.--- --
30
26-
�+ 26
1�
22 - - ---- -
O Y0 -...
'a 18 .�._ ..... .r_- -...
N 16 ..
E _
14 _._
Y_
12
X
10
J
6
4
0 -
0 1 2 3 4 6 6 7 8 9 10 11 12 13 14
SOLIDS CONCENTRATION (kglm3)
Secondary Clarifier 1 Overflow Secondary Clarifier 1 Underflow
Secondary Clarifier 1 Flux Secondary Clarifier 1 Feed
Figure 4 — Design Maximum Month State Point Analysis w/ Current SVI (5-day SRT)
TECHNICAL MEMORANDUM 9 BHC Consultants, LLC
WWTP Nuvoda MOBT11 Process Evaluation and Trial
In comparison, Figure 5 illustrates a state point analysis for the final clarifiers based on an
assumed SVI of 100 with the Nuvoda MOB TM process. In this case, the intersection of the
overflow and underflow lines fall below the flux curve, indicating that there is some excess
capacity within the clarifier. As this scenario is for maximum month conditions, some capacity is
necessary to allow for increases over maximum month flows (peak day, diurnal peaks, etc.).
657-
60
55 _._._----- _ .................... ........ _
660 ..
- 40. .......... _.
O
35 -
N
E 30
j 20
J
LL 15 .. .. .� _ ..
0
O 1 2 3 4 5 6 7 6 9 10 11 12 13 14
SOLIDS CONCENTRATION ftlm3)
Secondary Clarifier 1 Overflow Secondary Clarifier 1 Underflow
Secondary Clarifier 1 Flux Secondary Clarifier 1 Feed
Figure 5 — Design Maximum Month State Point Analysis w/ Reduced SVI (5-day SRT)
For comparison, the BioWin model for design maximum month conditions was also ran using an
SRT of 8 days. A summary of predicted effluent quality and operating parameters at this higher
SRT is shown in Table 5.
Table 5
BioWin Results with MOB TM
Process at Maximum Month Flow and Reduced SVI
Parameter
Quantity
Unit
-lnfluenfflow-
1-18-7
-MGD-
Sludge Production
10,920
Ibs/day
SRT
8
days
Effluent TIN
17.7
m /L
Effluent Ammonia
0.3
mg/L
MLR
300
%Q
5,020
mg/L
MLSS
RAS Rate
7.4
MGD
TECHNICAL MEMORANDUM
10
BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
��NsU�fiAN S
The BioWiin model predicts complete nitrification at this higher SRT, though denitrification is not
improved. This again suggests that the anoxic zones are likely carbon limited. The increase in
MLSS associated with the higher SRT increases loading on the clarifiers. However, assuming
an SVI of 100, the state point analysis show in Figure 6 suggests there might still be sufficient
clarifier capacity. Although the intersection of the overflow and underflow lines are just below
the flux curve, the underflow line is over the trailing end of the flux curve, indicating a higher
RAS flow is likely necessary than assumed in the model.
66so
60
O
N
Of Y_
K
J
LL
0 1 2 3 4 6 6 7 6 9 10 11 12 13 14
SOLIDS CONCENTRATION (kglm3)
Secondary Clarifier 1 Overflow Secondary Clarifier 1 Underflow
Secondary Clarifier 1 Flux Secondary Clarifier 1 Feed
66
46
Figure 6 — Design Maximum Month State Point Analysis w/ Reduced SVI (8-day SRT)
If improvement in settling characteristics to the level suggested by Nuvoda are not observed
during the trial, such that substantial increases in MLSS are not practical, it is still possible to
further increase treatment capacity by increasing the fill percentage of kenaf. Nuvoda typically
applies a fill percentage of 1.26% and generally does not recommend increasing this
percentage for municipal applications, as it is rarely necessary. However, the fill percentage
could be increased if that were deemed appropriate for this application. It should also be noted
that the WVVfP is well short of the current design maximum month flow and so it is unlikely to
experience flows that high for quite some time, if ever. If it were determined that the Nuvoda
MOB TM process alone could not achieve the level of denitrification required under design
TECHNICAL MEMORANDUM 11 BHC Consultants, LLC
WWTP Nuvoda MOBT11 Process Evaluation and Trial
conditions, even with supplemental carbon, there are processes targeted for denitrification that
could be added in the future when necessary.
4. Initial Conclusions
Although the process modeling indicated that the Nuvoda MOB TM process may not achieve
sufficient nitrogen removal under design conditions, the assumptions made in conducting this
analysis are generally conservative. The above analysis indicates that this technology is a
viable method of gaining capacity for nutrient removal and could be found to perform better than
the conservative estimates herein. Even with the conservative assumptions herein, the
performance of the Nuvoda MOB TM process could still be a fundamental piece of the City's
strategy for achieving nitrogen removal, possibly on its own for some period of time before any
subsequent improvements are necessary. Therefore, it is recommended that the City proceed
with conducting a trial of the Nuvoda MOB TM process, as this will provide valuable data on the
process to more accurately assess the performance of a full-scale operation. For example,
improvements in settling may yield lower SVI values than assumed above, which would provide
greater final clarifier capacity. Additionally, there may be more biofilm mass than predicted by
the model, which could increase overall treatment capacity without increasing the suspended
growth MLSS.
5. Nuvoda MOBTm Technology and Trial
This section provides an overview of Nuvoda's Mobile Organic BiofilmTM (MOB TM) process, the
pilot system that will be utilized for a trial of the technology, identification of the trial objectives
and schedule, and a sampling and testing plan for data collection during the trial. An overview
of the responsibilities during the trial is provided in Table 6 below.
Table 6
Responsibilities for Nuvoda MOB TM Process Trial
Activft_or Item
Develop this Technical Memorandum
I City
R
_Nuvoda
R
BHC
Jacobs_
Notes
P
R
Submit Technical Memorandum to Ecology
P
1
Furnish Pilot System
P
Furnish Ancillary Items (e.g., piping, etc.)
P
Electrical and water connections
P
Temporary Supplemental Alkalinity System
P
Pilot System Setup
P
P
A
TECHNICAL MEMORANDUM 12 BHC Consultants, LLC
WWTP Nuvoda MOBTI Process Evaluation and Trial
C�A150111LTANTS
Table 6
Responsibilities for Nuvoda MOB TM Process Trial
Activity or Item j City Nuvoda BHC Jacobs Notes
Pilot System Startup, Troubleshooting, and
P
P
Training
Pilot System Operation
P
Sampling and Testing
P
2
Operate pilot system
P
A
Process Monitoring and Testing Data
P
Recordkeeping
Execute Trial Objectives
P
A
A
Assessment of Initial Trial Period
R
R
P
R
Decision on Trial Extension
P
A
A
A
Demobilization of Pilot System
P
P
Prepare Engineering Report
R
P
R
Notes:
P = Primary Responsible Party; R = Reviewer; A = Assist/Advise
1) Responsibilities and manner in which the trial is conducted may be impacted by input from Ecology.
2) The City will send some samples to an outside laboratory for testing of certain parameters.
5.1 Technology Overview
The Nuvoda MOB TM process is designed to oxidize organic matter and remove nitrogen using
both fixed film and suspended growth. The fixed film growth utilizes a media with a significantly
different size and consistency compared to traditional plastic media. The Nuvoda media
consists of processed kenaf, a renewable lignocellulosic material that is harvested from the
woody kenaf, a fast-growing fiber plant. In order to serve as a recoverable and sustainable
mobile biofilm media, the kenaf is machined to an effective size of approximately 1 millimeter.
This allows it to combine with suspended biomass thus form a hybrid matrix of suspended and
fixed biomass that acts similar to mixed liquor (i.e., free to circulate between process
basins/tanks). The kenaf material typically enhances the settleability of the MLSS and tends to
be completely captured in the final clarifier and thus retained within the process. Waste
activated sludge (WAS) is passed through a drum screen to separate the kenaf media from the
wasted suspended growth. The kenaf media is returned to the process and the wasted
suspended growth is handled as wasted sludge would be normally. The Nuvoda MOB TM
process is similar in concept to an integrated fixed film activated sludge (IFAS) process, but
does not require vigorous aeration/mixing (normal fine bubble aeration is sufficient to keep the
kenaf media suspended), utilizes a simpler media retention system that does not impact the
TECHNICAL MEMORANDUM 13 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
hydraulic profile, and uses an organic media that positively impacts settleability in the final
clarifiers.
5.2 P►lot System Layout and Configuration
The pilot system provided by Nuvoda will consist of a rotating wedge wire drum screen with 0.5
millimeter perforations and enough kenaf media to achieve a fill of 1.26% one aeration basin.
The drum screen will be located in the Blower Building. There is available space between two
existing blowers where the drum screen can be temporarily installed (see Figure 7), which will
allow it to dump kenaf directly into Aeration Basin No. 1. Therefore, the City will be using
Aeration Basin No. 1 for the trial along with Final Clarifier No. 1. Although the City had originally
planned to replace the drive in Final Clarifier No. 1 this summer and thought about using Final
Clarifier No. 2 instead, the City has some concerns additional stress on the spiral scraper
collector mechanism in Final Clarifier No. 2 compared to the traditional plow -type scrapers in
Final Clarifier No. 1, since the spiral scrapers are designed to move more material faster.
Although there should not any significant additional stress imparted on the collectors due to the
low specific gravity of the kenaf, to be safe the City decided to defer the drive replacement for
Final Clarifier No. 1 until after the completion of the trial period. However, the City will still drain
Final Clarifier No. 1 before the start of the trial to replace the scrapers on the plows to ensure
proper tolerance such that a significant amount of kenaf is not stranded at the bottom of the
clarifier. If the City extends the trial into the wet weather months, there could be an opportunity
to switch operation from Final Clarifier No. 1 to Final Clarifier No. 2. Additionally, if more
capacity is required during wet weather, the City may still run their conventional activated sludge
process in a parallel train. Typically, the City does not utilize more than two aeration basins and
clarifiers at a time, even during the wet weather months.
TECHNICAL MEMORANDUM 14 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
CONS;L A[ 5
Figure 7 — Photos of the Proposed Drum Screen Location Looking East and West
As shown in Figure 8 below, existing WAS Pump No. 1 will be used to convey WAS from the
Final Clarifier No. 1 RAS pipeline to the drum screen. A temporary flexible pipe will be routed
from the discharge of the WAS pump to the inlet of the drum screen. The flexible pipe will pass
through an opening in the floor of the Blower Building connecting it to the WAS pump on the
level below. Similarly, a flexible line will be routed from the drain of the drum screen through the
same opening to existing sump pumps on the lower level. The WAS drained from the drum
screen will flow by gravity to the sump pumps. Valves on the discharge from the sump pumps
can be arranged to direct the WAS to the existing WAS storage tank. The City has confirmed
that the existing sump pumps have sufficient capacity to convey the drainage flow from the
drum screen.
TECHNICAL MEMORANDUM 15 BHC Consultants, LLC
WWTP Nuvoda MOBT°" Process Evaluation and Trial
N-D!7'
r
C SULTANTS
DRUM SCREEN
Figure 8 - Nuvoda MOB TM Process Pilot System Configuration
The City had given consideration to potentially running two trains with kenaf during the wet
weather months, assuming the duration of the trial is extended. There was some concern that
returning the kenaf only to Aeration Basin No. 1 would likely yield some imbalance in the
distribution of kenaf between two aeration basins. Nuvoda did not think the imbalance would be
a concern for the duration of the trial and the imbalance could be partially offset by opening the
isolation valve on discharge header between RAS Pumps No. 1 and 2 to allow mixing of RAS
flow and modifying RAS pumping and wasting rates to maintain a relatively even balance.
However, after further di`scussion,-it-wasdecided that the addedcostto purchase -the additional
kenaf would likely not yield significant benefits to the information gained. Furthermore, having a
single train with kenaf provides greater flexibility to stress the MOB TM process to determine the
limits of nitrification.
TECHNICAL MEMORANDUM 16 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
10
JWS;LT;N t'5
Because the existing configuration and equipment within the aeration basins does not allow the
creation of anoxic zones, the trial of the Nuvoda MOB process will focus on achieving complete
nitrification and the conditions (e.g., volume, MLSS, SRT, etc.) needed to maintain complete
nitrification. Knowing this will help determine how much of the existing aeration basin volume
could be freed up for use as anoxic zones.
5.3 Pilot System Requirements and Monitoring Equipment
Based on the information provided by Nuvoda, the drum screen will require a 480-volt, 3-phase
power feed and a 1-inch water connection. The 0.75 horsepower motorized drive for the drum
screen will require a 15A breaker to feed the drum screen control panel, which contains the
motor starter and overload relays. The City will need to run a temporary conduit and wire from a
spare MCC bucket that has or can be fitted with a 15A breaker to the control panel. Optionally,
a 20A would probably be work as well, but a breaker larger than 20A is not recommended.
The drum screen requires a 1-inch waterline to connect in two locations on the drum screen for
external washing of the drum. The waterline connection must be able to supply 14 to 45 gpm at
70 psi. The wash water could utilize either plant effluent or non -potable water.
The City plans to install a temporary flow meter along the pipeline feeding the drum screen to
monitor and control the WAS flow. The City is also considering installing a temporary density
meter to monitor the concentration of solids in the WAS drained from the drum screen. These
two measurements will allow calculation of the wasted mass. Alternately, the City could utilize
routine grab samples to monitor solids in the drained WAS flow.
To gather more complete and accurate information on the primary effluent that is feeding into
the Nuvoda MOB TM process, a composite sampler will be added temporarily to sample primary
effluent.
As discussed in Section 3.1 above, the model predicts that pH will become depressed to the
point that it could limit nitrification and violate the NPDES permit limit without the addition of
supplemental alkalinity. The City currently uses sodium hydroxide for their odor control
scrubber. Sodium hydroxide could be fed from the existing sodium hydroxide storage tank using
one of the existing feed pumps. Alternatively, the City could use a separate temporary storage
TECHNICAL MEMORANDUM 17 BHC Consultants, LLC
WWTP Nuvoda MOB"' Process Evaluation and Trial
tank provided by the chemical supplier that is dedicated for supplemental alkalinity, thereby
providing greater storage and allowing more time between refills. Although totes would be
another option, the estimated quantities required likely make the use of totes impractical.
5.4 Testing Objectives and Schedule
Major milestones for the Nuvoda trial are as follows:
• May 18, 2020 — Nuvoda is set to deliver the drum screen to the'V VV� ii P.
June 1, 2020 — Nuvoda will begin installation of the drum screen. This may be delayed
due to restrictions or requirements associated with the COVID-19 pandemic. Kenaf will
be delivered no later than 1 week after installation of the drum screen.
a June 1, 2020 — Earliest start of the trial period. The start of the trial may be adjusted
based the screen installation date.
• September 30, 2020 — Earliest end of the initial trial period. The end of the initial trial
period may be extended based on the trial start date.
• February 28, 2021 — End of the extended trial period. Extension of the trial is optional
and will be determined based on the level of success during the initial trial period.
The goals of the Nuvoda MOB TM process trial are to demonstrate the following:
Consistently achieve the following effluent quality:
o BOD5 < 10 mg/L (30-day running average, minimum 1 sample per week)
o TSS < 10 mg/L (30-day running average, minimum 1 sample per week)
o Ammonia-N < 0.5 mg/L (30-day running average, minimum 3 samples per week)
o Ammonia-N not exceeding 1.5 mg/L in any sample
• Assess improvements to sludge settleability and its impact on performance of the final
clarifier and allowable loading.
Assess the minimum hydraulic retention time to sustain complete nitrification.
Assess the capability to achieve simultaneous nitrification/denitrification at reduced
dissolved oxygen levels, while maintaining essentially complete nitrification.
A schedule of the objectives to achieve the goals of the trial is as follows:
1. Step 1 — Startup, training, troubleshooting and acclimation of the process. Generally,
about 3 times the SRT is necessary to ensure a stabilized process. Although the SRT of
suspended growth will initially be targeted for 5 days, the SRT of the biofilm will be much
longer. Therefore, it is expected that the acclimation period to establish the biofilm could
TECHNICAL MEMORANDUM 18 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
be about 2 months following an initial week for startup, training and troubleshooting.
During the acclimation period, all zones within Aeration Basin No. 1 will be operated as
fully aerobic (no tapered aeration) to facilitate complete nitrification, which should be
confirmed by the end of the acclimation period.
2. Ste 2 — Determine Lowest SRT Necessa for Complete Nitrification. The next step will
be to reduce the SRT of the suspended biomass based on maintaining complete
nitrification. A reduced SRT will decrease MLSS and solids loading on Final Clarifier No.
1, but increase wasting. To start, the suspended growth SRT will be reduced from 5
days to 4 days. Although the suspended growth may acclimate more quickly, it could
over a month for the biofilm to fully acclimate. Depending on how the process operates
at an SRT of 4 days, a second adjustment to the SRT may be made. During this period,
all zones will continue to be operated as fully aerobic.
3. Step 3 — Examine Simultaneous Nitrification/Denitrifcation. Investigate the impacts of
decreasing dissolved oxygen (DO) concentrations with respect to achieving
simultaneous nitrification/denitrification. Taper the dissolved oxygen concentrations
among the different aeration basin zones, starting at a higher value in the first zone and
lowering DO incrementally in each subsequent zone. Assess how lower DO may
enhance denitrification within the biofilm. How low the DO may be reduced in each zone
may be limited by a minimum level of aeration to keep the biomass and MOB
suspended. Although the process may respond relatively quickly to changes in DO, it
may take several weeks to for the biofilm to fully acclimate. Therefore, once minimum
DO settings are established, the process will continue to operate at these levels for at
least a month to determine if changes there are subsequent changes in the biofilm that
impact the results.
4. Ste 4 -- Determination for Extended Testing. It is expected that the initial trial period will
at most carry through Step 3 (maybe only Step 2) and that the extended trial period will
be necessary to complete the rest of the testing outlined herein. However, before
proceeding with the extension, results from the initial trial period will be reviewed to
confirm that further testing is warranted. If the initial results are disappointing, further
testing may not be pursued.
5. Step 5 — Reduce HRT_in the Aeration Basin. The MOB TM process would be stressed at
higher flows to help determine how HRT impacts the ability of the process to meet the
effluent quality goals (e.g., no significant bleed through of ammonia). Because it is
TECHNICAL MEMORANDUM 19 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
■r
C �JLTAN S
expected that one train will be capable of treating dry weather flows, stress testing likely
won't be possible until the wet weather months when influent flows increase. It is
anticipated that the City may need to bring a second process train online (operated
separately with their current activated sludge process) when flows reach around 5 MGD.
6. Ste 5 — Examine Impact of increased Organic Load. To simulate increased organic
load, all flow could be passed through a single primary clarifier. This would help
determine the impact of reduced removal in the primary clarifiers on the MOB TM process
and whether or not the process could effectively maintain the effluent quality goals. This
may be examined most effectively during wet weather months when multiple primary
clarifiers are most likely to be needed to meet current typical levels of performance. If
the process reacts well initially, the increased load could be continued for a month or
more to see if there are changes in the biofilm that impact process performance.
7. Step 6 — Demobilization. The final week of the trial, after all the above steps have been
completed to the satisfaction of the City, the pilot system will be decommissioned and
demobilized.
As stated previously, it does not appear possible to create a temporary anoxic zone that
would allow operating the secondary treatment system as an MLE process. Although the air
could be turned off to one or more zones in an aeration basin, there would then not be
sufficient mixing energy to keep the kenaf and other solids suspended. Furthermore, it
would be difficult to implement an internal mixed liquor recycle. For example, installing a
submersible pump and piping would require significant time to procure, place and power the
equipment. Therefore, rather than directly assessing denitrification in a separate anoxic
zone, the focus will be on understanding the requirements needed for nitrification and the
potential for simultaneous nitrification/denitrification. These will subsequently help
determine how much of the existing aeration basins volume is required for nitrification and
how much could be made available for denitrification.
5.5 Sampling and Testing
A summary of the sampling and laboratory testing to be implemented for collection of data to
evaluate performance and efficiency of the Nuvoda MOB TM process in relation to achieving
the goals of the trial is provided in Table 7 below. All laboratory analyses will be performed
TECHNICAL MEMORANDUM 20 BHC Consultants, LLC
VWVTP Nuvoda MOB TM Process Evaluation and Trial
; m)
S; A N S
in accordance with the latest version of the Standard Methods for the Examination of Water
and Wastewater or established EPA methods, unless noted otherwise.
TABLE 7
SAMPLING AND LABORATORY TESTING SCHEDULE
Sample
Location
Sample
Type
Analysis
Frequency
Notes
Influent
Metered
Flow
Continuous
1
Grab
Sodium Hydroxide Dose
5 / week
5
Temperature
5 / week
24-Hour
Composite
CBOD5
3 / week
1,2
TSS
3 / week
1,2
pH
3 / week
2
VSS
1 / week
2
COD
3 / week
2
Filtered CBOD5
1 / week
2, 3
Filtered COD
1 / week
2,3
Filtered -Flocculated COD
1 / week
2,4
TKN
1 / week
2,6
Ammonia
3 / week
2
Nitrate
1 / week
2
Alkalinity
1 / week
2,6
Primary Effluent
24-Hour
Composite
Metered
TSS
1 / week
2
CBOD5
1 / week
2
COD
1 / week
2
TKN
1 / week
2,6
Aeration Basin
No. 1
Airflow
Continuous
Zone 1A DO
Continuous
Zone 2 DO
Continuous
Zone 3 DO
Continuous
Grab
MLSS (w/o kenaf)
5 / week
7
MLVSS (w/o kenaf)
5 / week
7
Biofilm Mass
1 / week
7
Kenaf % Fill
1 / week
7
RAS
Metered
Flow
Continuous
Grab
TSS
5 / week
WAS
Metered
Flow
Continuous
Grab
TSS
5 / week
Final Clarifier
No. 1
Grab
Sludge Blanket Depth
5 / week
SVI (w/ kenaf)
5 / week
8
SVI (w/o kenaf)
5 / week
7
Final Effluent
Metered
Flow
Continuous
1
TECHNICAL MEMORANDUM 21 BHC Consultants, LLC
WWTP Nuvoda MOB"' Process Evaluation and Trial
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CONSULTANTS
Grab
pH
Daily
1
Temperature
Daily
24-Hour
Composite
CBOD5
3 / week
1, 2
TSS
5 / week
1,2
COD
1 / week
2
TKN
1 / week
2,6
Ammonia
3 / week
2
Nitrate
3 / week
2
Nitrite
3 / week
2
Screw Press
Filtrate
Grab
TSS
1 / week
1 / week
2
2
Ash Scrubber
Drainaae
Grab
TSS
Notes:
1) Sampling and testing already required per the NPDES permit.
2) Take all of these samples on the same day(s) as one another so that they may be correlated.
3) Filter the sample using a 1.2 micron glass fiber "C" filter. Run the test on the filtrate.
4) Measurement of filtered -flocculated COD is not a Standard method, but is documented in the
1999 WERF publication on Methods of Wastewater Characterization in Activated Sludge
Modeling and is as follows:
a) 1 mL of 100 g/L zinc sulfate solution is added to 100 mL of wastewater.
b) The sample is mixed vigorously for approximately 1 minute.
c) The sample pH is adjusted to approximately 10.5 using 2 M sodium hydroxide solution with
slow mixing for 5 minutes.
d) The sample is then allowed to settle for a few minutes and a volume of clear supernatant is
withdrawn for filtration through a 0.45 micron membrane filter.
e) The filtrate COD is measured. Filtrate COD can be measured using spectrophotometry.
5) Sodium hydroxide dose as measured in gallons per day or mg/L delivered into the wastewater.
6) Samples for analysis of alkalinity and TKN will be sent to AmTest for testing.
7) Filter sample through a 0.5 mm sieve. See Attachment A for further detail.
8) Note the settled sludge volume at the 10 minute mark. See Attachment A for further detail.
A list of test methods to be used and the associated method detection limit (MDL) is
provided in Table 8 below.
TECHNICAL MEMORANDUM 22 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
IGL.IA
TABLE 8
SAMPLE TESTING METHODS
Parameter Tested EPA/Standard Method MDL
Alkalinity SM 2320 B 1 mg/L
TSS
SM 2540 D
5 mg/L
VSS
SM 2540 E
2 mg/L
Temperature
SM 2550 B
N/A
Settled Sludge Volume
SM 2710 C
N/A
Sludge Volume Index
SM 2710 D
N/A
2 - 14
pH
SM 4500-H+ B
Ammonia -Nitrogen
EPA 350.1
0.1 mg/L
Nitrite -Nitrogen
SM 4500-NO2- B
0.02 mg/L
Nitrate -Nitrogen
EPA 353.2
0.3 m /L
Dissolved Oxygen
SM 4500-0 G
0.2 mg/L
TKN
EPA 351.2
0.19 mg/L
CBOD5
SM 5210 B
2.0 mg/L
COD
SM 5220 D
As required by the NPDES permit, the City will submit monthly the available test results from
the pilot study to Ecology as an attachment to the monthly discharge monitoring report.
In addition to the sampling and testing listed in Table 7, the City is looking into engaging with
Dr. Mari Winkler at the University of Washington who is a specialist in the study of
biofilm/granular sludge. Nuvoda has worked with Dr. Winkler in the past to evaluate samples
of kenaf and biofilm growth and provide information on the structure and makeup of the
biofilm. Dr. Winkler could also run nitrification and denitrification tests separately on the
biofilm and suspended growth.
6. Next Steps
Following completion of trial, this technical memorandum will be amended and expanded into an
engineering report that summarizes observations and data from the trial, discusses operation of
the Nuvoda MOB TM process during the trial to fulfill the objectives, assesses performance of the
technology with respect to established goals, and updates predictions for performance at
current and design flows and loads.
TECHNICAL MEMORANDUM 23 BHC Consultants, LLC
WWTP Nuvoda MOB TM Process Evaluation and Trial
ATTACHMENT A
Nuvoda Testing Methods
NUVODA
Innovative Wastewater Solutions
Nuvoda US Testing Methods
SVI & MLSS
Using a 1000 mL graduated cylinder, collect a well -mixed sample of mixed
liquor in a 1-gallon container. Keep the sample mixed and fill the graduated
cylinder to the 1000 mL mark. Allow for the sample to settle for 30 minutes
and take note of the top of the sludge blanket. For granular sludge/fixed film
systems, the SVI10 — SV13o. Make note of the sludge depth at the 10-minute
mark to evaluate if the MOB process has started to grow biofilm.
The testing method is the same as with Kenaf, but you will use a 0.5 mm
screen to filter the mixed liquor sample to ensure the Kenaf particles are not
in the sample.
MLSS Testing Method Wth KenaM-
Collect a well -mixed sample of mixed liquor in a 500 mL beaker. Remove two
filter papers from a desiccator and record the weight of each. Place the filter
holder on a vacuum flask and then place a filter on top of the filter holder by
using a pair of tweezers. Stir the sample of mixed liquor in order to get a
good mixture for the experiment. After sample is mixed, pour 25 mL into a
graduated cylinder. Turn on the vacuum pump and pour the sample into the
filter holder. After all the mixed liquor has gone through, run three portions
of 30 mL distilled water through the filter holder to rinse any particles that
may have stuck to the glass. Allow the vacuum pump to run an additional
three minutes. This will help remove any extra water from the filter before
drying. Switch the vacuum pump off and remove the filter from the filter
holder and place in the corresponding weighing dish. Repeat above process
for as many trials as needed. Place the filter(s) into a drying oven, which is
set to 103°-105° C, for one hour. Upon drying, replace filters into a desiccator
for 30 minutes. After 30 minutes in the desiccator, the filters are to be
weighed.
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+ 1 919 615 1205 www.nuvodaUS.com
Suite 200, Raleioh, NC 27603 `
NUVODA
Innovative Wastewater Solutions
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The testing is the same as the previous MLSS testing with the Kenaf. Using a
sample from the original 500 mL sample pulled, screen the 25 mL through a
0.5 mm screen. The Kenaf can be rinsed lightly with DI water to help remove
any particulates that are not a part of the Biofilm. The collected screened
sample, although slightly more volume than the 25 mL poured, will be tested
for TSS to give the MLSS without the Kenaf.
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Collect a well -mixed sample of mixed liquor in a 500 mL beaker. Use a
0.5 mm screen to filter the sample of the Kenaf particles. Rinse the Kenaf
particles with DI water. Resuspend the Kenaf with biofilm particles in DI
water that were collected from the 500 mL sample. Remove two filter papers
from a desiccator and record the weight of each. Place the filter holder on a
vacuum flask and then place a filter on top of the filter holder by using a pair
of tweezers. Stir the sample of Kenaf with biofilm and DI water in order to
suspend the Kenaf with biofilm in solution. Turn on the vacuum pump and
pour the sample into the filter holder. After all the solution has gone through,
run three portions of 30 mL distilled water through the filter holder to rinse
any particles that may have stuck to the glass. Allow the vacuum pump to run
an additional three minutes. This will help remove any extra water from the
filter before drying. Switch the vacuum pump off and remove the filter from
the filter holder and place in the corresponding weighing dish. Repeat above
process for as many trials as needed. Place the filter(s) into a drying oven,
which is set to 103°-105° C, for one hour. Upon drying, replace filters into a
desiccator for 30 minutes. After 30 minutes in the desiccator, the filters are
to be weighed and the mass of the Kenaf with biofilm to be recorded.
After the mass is recorded, resuspend the Kenaf particles in DI water and
screen Kenaf again through a 0.5 mm screen. Rinse the particles with DI
water, to ensure all sluffed biofilm is not attached to Kenaf, and resuspend
rinsed Kenaf particles without the biofilm in a DI solution. Remove two filter
papers from a desiccator and record the weight of each. Place the filter
holder on a vacuum flask and then place a filter on top of the filter holder by
using -a -pair oftwuezers.-Stir the sample -of Kenaf and -DI -water -in order -to
suspend the Kenaf in solution. Turn on the vacuum pump and pour the
sample into the filter holder. After all the solution has gone through, run
three portions of 30 mL distilled water through the filter holder to rinse any
particles that may have stuck to the glass. Allow the vacuum pump to run an
additional three minutes. This will help remove any extra water from the
L ® G
+ 1 919 615 1205 www.nuvodaUS.com 733 W. Johnson Street
Suite 200, Raleioh, NC 27603
NUVODA
Innovative Wastewater Solutions
filter before drying. Switch the vacuum pump off and remove the filter from
the filter holder and place in the corresponding weighing dish. Repeat above
process for as many trials as needed. Place the filter(s) into a drying oven,
which is set to 103°-105° C, for one hour. Upon drying, replace filters into a
desiccator for 30 minutes. After 30 minutes in the desiccator, the filters are
to be weighed.
The mass of the filters with Kenaf without biofilm should be subtracted from
the mass of the filters with Kenaf with biofilm to give a close estimate of the
mass of biofilm growth on the Kenaf. Since the Kenaf is porous, it will be
difficult to have 100% accuracy with this test.
Pgrgent Fill of Kenaf.-
1. Using Mass (best method after biofilm forms)
From the previous testing determining the Mass of Biofilm on Kenaf, the
weight of the Kenaf without the biofilm can be recorded as (Mass of Kenaf g)
and using the density of raw dry Kenaf (0.263 g/mL) the total volume of
kenaf can be determined in (mL).
The percent fill of Kenaf is calculated as:
(Volume of Kenaf mL) / (500 mL Sample)
2. Using Volume (easiest method with fresh Kenaf addition)
Using a 1000 mL graduated cylinder, collect a well -mixed sample of mixed
liquor in a 1-Liter container. Screen the mixed liquor sample through a 0.5
mm screen. Lightly rinse the screened Kenaf particles with DI water to
remove any particulates that may have attached to the Kenaf.
Resuspend the Kenaf particles in a solution of DI water (The volume of the
solution should be no less than 500 mL and no greater than 1 L). Mix the
solution of DI water and Kenaf particles and pour into the 1000 mL
graduated cylinder. Allow the sample to settle for 30 minutes and take not of
the top of the Kenaf blanket in (mL).
The percent fill of the Kenaf is calculated as:
(Volume of Kenaf mL) / (1000 mL Sample)
t. ® 0
+ 1 919 615 1205 www.nuvodaUS.com 733 W. Johnson Street
Suite 200, Raleiah, NC 27603