HomeMy WebLinkAboutW-2024-0716_Oshkosh_Ozone and SCADA Replacements_Approval
October 8, 2024
DIANE BARTLETT CLERK
CITY OF OSHKOSH
215 CHURCH AVE
PO BOX 1130
OSHKOSH WI 54903-1130
Project Number:
PWSID#:
DNR Region:
County:
W-2024-0716
47104574
NER
Winnebago
SUBJECT: WATER SYSTEM FACILITIES PLAN AND SPECIFICATION APPROVAL
Dear Ms. Bartlett:
The Wisconsin Department of Natural Resources, Division of Environmental Management, Bureau of Drinking
Water and Groundwater, is conditionally approving plans and specifications for the following project. An
engineering report or information of sufficient detail to meet the requirements of s. NR 811.09(3), Wis. Adm.
Code, was submitted along with the plans and specifications.
Water system name: Oshkosh Waterworks
Date received: 07/26/2024
Engineering firm: Jacobs Engineering Group
Professional Engineer: Linda Mohr
Regional DNR Contact: Jamie Douglas, 3369 West Brewster Street, Appleton WI 54914-1602, (920)362-6629,
jamie.douglas@wisconsin.gov
DNR Plan Reviewer: McCrea Baker, 101 South Webster Street, Madison WI 53707, (608) 220-6987,
mccrea.baker@wisconsin.gov
Project description: On behalf of the City of Oshkosh (City), Jacobs Engineering Group has submitted plans
and specifications for the replacement of the existing ozone disinfection system equipment and SCADA system
upgrades at the water treatment plant. The plans and specifications are hereby approved subject to the conditions
below.
Background: The water supply system for the City of Oshkosh presently includes a surface water treatment plant
drawing raw water from Lake Winnebago, three finished water clearwells, four elevated storage tanks, and the
distribution system composed of two pressure zones. The water treatment plant includes two treatment trains that
each include rapid mix, flocculation, sedimentation, dual media gravity filtration, ozone contactors, and granular
activated carbon contactors. Chemical addition consists of gas chlorine and ammonia to form chloramines for
disinfection purposes, fluorosilicic acid for community dental health purposes, phosphoric acid for distribution
system corrosion control purposes, and sodium hydroxide for pH adjustment and distribution system corrosion
control purposes.
Ozone is utilized to provide 1.0-log giardia inactivation and 2 log virus inactivation downstream of dual media
filtration. The water treatment plant can also utilize free chlorine contact time (CT) to provide 0.5-log giardia
State of Wisconsin
DEPARTMENT OF NATURAL RESOURCES
101 S. Webster Street
Box 7921
Madison WI 53707-7921
Project Number: W-2024-0716 Page 2 of 6
inactivation and 4.0-log virus inactivation if the ozone equipment is out of service. The existing ozone treatment
system equipment is approximately 25 years old, and many components have become obsolete. Additionally,
many hardware components of the SCADA system are outdated. The proposed project will replace outdated
equipment to improve system performance.
Ozone System Replacements: The existing ozone equipment will be replaced with new equipment of similar
design and capacity. The existing equipment will be removed and replaced in phases so interruptions in operation
of the ozone equipment can be minimized. The existing ozonation system was designed for 20 million gallons per
day (MGD), though operational issues have limited the current systems capacity. The proposed ozone
replacement system is designed to treat the maximum water system flow rate, which was determined to be 13.7
MGD. The proposed ozonation system will have a maximum ozone generating capacity of 1,200 pounds per day
(ppd). The major components of the ozone system replacements include the liquid oxygen (LOX) storage and
gaseous oxygen (GOX) delivery system, nitrogen supply, ozone generators, diffusers, quenching system,
sampling system, and ozone destruction system.
LOX Storage and GOX Delivery System: The two existing 9,000-gallon LOX storage tanks will be replaced with
two new 9,000-gallon LOX storage tanks. The existing LOX system is installed outdoors in a recessed concrete
sump. The existing sump will be filled with concrete to match surrounding grade prior to the new LOX equipment
being installed. While the existing LOX storage tank and GOX delivery system is being replaced, a temporary,
trailer mounted LOX system will be provided by AirGas. The temporary system will connect to the existing GOX
piping prior to the piping extending through the east wall of the treatment plant building. AirGas will have
automatic tank level and pressure alarms, which will be connected to a remote monitoring system. Treatment
plant operators will also have monitoring capabilities for the temporary LOX system.
The new, permanent LOX storage tanks will be manufactured by Chart Industries, Inc. and be constructed of type
304L stainless steel with an outer vacuum jacket. A new LOX fill connection will be provided north of the LOX
storage tanks. Each LOX storage tank will discharge to a LOX header, which will connect to three new LOX
vaporizers.
The three existing LOX vaporizers will be replaced with three new Thermax vaporizers. The new vaporizers will
each have a capacity of 26,800 standard cubic feet per hour at 75 psi. Two of the vaporizers will be utilized during
normal operations with the third available for standby operation. The two existing electric trim heaters will be
replaced with new Thermax electric trim heaters of similar capacity.
Four-inch diameter Type 316L stainless steel GOX headers will be provided downstream of the trim heaters. Each
of the GOX headers will include a flow meter, pressure relief valve, pressure transducers, and shut off valves. A
1-micron particulate filter will be provided downstream of the trim heaters. The GOX piping will extend through
the east wall of the water treatment plant. One of the existing GOX pipes will remain in place and the other will
be replaced with new 4-inch diameter stainless steel GOX piping routed in parallel with the existing GOX piping
through the treatment plant to the ozone generator room.
Nitrogen Supply: The proposed ozone feed system will include a supplemental nitrogen feed system to efficiently
produce ozone. The existing air compressor system will be replaced with a duplex 1-horsepower oilless scroll air
compressor. The air compressor will include a nitrogen gas membrane to dry and concentrate nitrogen gas in the
30-gallon tank. A filtered water separator, a 1-micron particular filter, and a 0.01-micron coalescing filter will be
provided between the air compressor air tank and the nitrogen gas membrane. The air compressor and nitrogen
gas concentrator system will have a capacity of 5 cubic feet per hour of pure nitrogen gas at 100 psi. The nitrogen
gas will be connected to the GOX piping through 1/2-inch and 3/4-inch diameter stainless steel piping.
Project Number: W-2024-0716 Page 3 of 6
Reportedly, the nitrogen supply system is not required for the operation of the ozone generation system, though
the ozone system would operate less efficiently without the supplemental nitrogen. Spare nitrogen boost system
components will be available to minimize downtime in the event of a nitrogen boost system failure.
Ozone Generators: The three existing ozone generators will be replaced with three new Wedeco ozone generators,
each with a capacity of 600 pounds per day at a 12% ozone concentration. The new generators will be horizontal
shell and tube design with Type 316L stainless steel shells. The new ozone generators will utilize borosilicate
glass dielectric tubes and a sight glass will be provided to observe the dielectrics. Four medium frequency inverter
power supply units will be provided and the ozone generators will be water cooled.
Cooling water will be provided through a closed loop system for the ozone generator and an open loop system for
the power supply unit. The cooling water systems will be provided water from the filter effluent piping and the
open loop cooling system discharge water will be recycled to the head of the plant by discharging through the
filter to waste piping. The open loop cooling water system will be powered by three centrifugal booster pumps,
each with a capacity of 115 gpm at 50 feet total dynamic head (TDH). The open loop cooling water system will
consist of ANS/NSF standard 61 certified components. The closed loop cooling water system will be powered by
three centrifugal booster pumps, each with a capacity of 150 gpm at 50 feet TDH.
Ozone Diffusers: Ozone gas will be routed from the ozone generators to the ozone gas manifold in the ozone
gallery room, and then discharged to Cell 1 and Cell 3 of each ozone contractor through welded or flanged Type
316L stainless steel piping. The existing porous stone dome ozone diffusers will be replaced with new 7-inch
diameter porous stone dome diffusers. A total of 104 diffusers will be installed in each ozone contactor (2 total
ozone contactors) with 52 diffusers installed in Cell 1 and 52 diffusers installed in Cell 3. Each of the ozone
diffusers will have a minimum capacity of 0.1 cubic feet per minute and a maximum capacity of 0.8 cubic feet per
minute.
Ozone Quenching System: A new ozone quenching system will be installed which will utilize calcium thiosulfate
to prevent ozone off-gassing in the GAC contactor room downstream of ozone treatment. A skid with three new
Watson Marlow Qdos 20, maximum 58 gallon per day peristaltic feed pumps will be used to feed a solution of
23.5% active calcium thiosulfate into either Cell 7 or 9 of each ozone contactor. One pump will be dedicated to
each ozone contactor and the third pump will be a standby pump. At the average 6.1 million gallon per day (4,230
gpm) treatment plant discharge rate and the anticipated average 0.5 mg/L dose, the anticipated chemical feed
pump setting will be 18% of the overall capacity of the pump. The estimated average calcium thiosulfate daily use
will be 10.6 gallons.
The chemical feed pumps will be flow paced by a 4 to 20 mA signal from the ozone contactor influent flow
meters. A backpressure valve, pressure gauge, a pressure relief valve, and a check valve near the point of injection
will be installed on the chemical feed pump discharge piping. Each chemical feed pump discharge piping will
include a calibration column and a ball valve.
The chemical feed pumps will take suction from a chemical supplier provided 330-gallon polyethylene chemical
storage tote. The tank will not be vented to the outside of the building. The chemical solution tank will rest on a
scale capable of measuring in 10-pound increments to determine the daily chemical usage. The chemical solution
tank will be located within a 350-gallon spill containment pallet to provide the required chemical leakage
containment.
The calcium thiosulfate will be injected into carrier water piping to transport the calcium thiosulfate from the
chemical storage area of the water treatment plant to the ozone contactors. The carrier water system will take
suction from finished water. The 44-gpm centrifugal carrier water pump will take suction through 2-inch diameter
SCH 80 PVC piping and discharge through 3/4-inch diameter SCH 80 PVC piping to the calcium thiosulfate
chemical feed skid. The calcium thiosulfate will be injected directly into a tee on the 1-inch diameter carrier water
Project Number: W-2024-0716 Page 4 of 6
piping. Individual 1-inch diameter SCH 80 PVC calcium thiosulfate carrier water lines will be routed to each of
the ozone contactors and will discharge through new diffusers installed in either Cell 7 or 9 of each ozone
contactor.
Ozone Sampling and Monitoring: The existing Hach Orbisphere Model C1100 ozone sampling residual monitors
will continue to be utilized. New ozone sampling pumps will boost water from the 10 existing ozone sampling
locations through the existing analyzer and discharge the water back to the head of the ozone contactor inlet.
Ozone Destruction System: The existing ozone off-gas destruction system will be replaced. The new ozone off-
gas destruction system will include two demisters and three low temperature catalytic ozone destruction units.
The ozone destruction system will have a capacity of 100 cubic feet per minute and utilize CARULITE200
manganese dioxide based catalyst. A Watlow 1-kW heater will be provided for the ozone destruction unit.
Ozone Gallery Piping Modifications: The existing piping manifolds along the ceiling of the ozone gallery will be
modified. New piping will be installed to accommodate the ozone system upgrades, including 4-inch diameter and
6-inch diameter Type 304L stainless steel cooling water supply and return piping, 4-inch diameter Type 316L
stainless steel GOX piping, 4-inch diameter Type 316L stainless steel ozone piping, and calcium thiosulfate
carrier water piping (see above).
Ozone CT Disinfection Credits: Ozone is fed for primary disinfection with a minimum target residual of 4.0
mg/L. The two ten-cell ozone contactors operating in parallel are provided with equipment to monitor the ozone
residuals at the effluent of Cell Nos. 1, 3, 5, 7, and 10. For the purposes of calculating the concentrations of the
remaining cell, the ozone levels used for Cell Nos. 2, 4, 6, and 8 are the average residuals measured in the
upstream and downstream cells. No inactivation credit is granted for Cell Nos. 9 and 10.
The CT values for Cell No. 1 in each contactor are calculated separately from the remaining cells. Based on
Appendix O (Guidelines to Evaluate Ozone Disinfection) of the US EPA’s Surface Water Treatment Rule
Guidance Manual the department grants 1-log virus and 0.5-log giardia inactivation for the first cell, provided the
outlet ozone residual from Cell No. 1 exceeds 0.1 mg/L and 0.3 mg/L, respectively. The normal ozone
concentration leaving Cell No. 1 is typically greater than 0.3 mg/L. An additional 1-log of virus inactivation is
required in the subsequent ozone cells.
The ozone CT for Cell Nos. 2 through 8 in each contactor are calculated by multiplying the sum of the recorded
or calculated ozone residual in each cell by the contact time (T10), which is calculated with the maximum daily
flow rate, contactor volume, and baffle factor of 0.7 as determined by tracer testing completed in 2000. The
department grants a 2.0-log virus and 1.0-log giardia inactivation credit provided that the inactivation ratio, based
on 2.0-log virus CT values and 1.0-log giardia CT values, are always greater than 1.0 in the ozone contactors.
Oshkosh reports the total inactivation ratio on the monthly report.
SCADA Upgrades: Components of the existing SCADA system will be replaced with modern equipment and
programing. The existing water treatment plant programable logic controllers (PLCs) will be replaced with similar
equipment. The new SCADA equipment will include operational controls, monitoring, and alarms for the water
treatment plant.
Other Upgrades: A new emergency eyewash and shower station will be installed adjacent to the new calcium
thiosulfate storage area. The 6 existing emergency eyewash and shower stations will be connected to the building
tempered water system.
Temporary Operations: During the ozone system replacement project, the ozone system will need to be
temporarily removed from service for a period of time. While the ozone disinfection system is temporarily out of
Project Number: W-2024-0716 Page 5 of 6
service, the water treatment plant will utilize free chlorine CT to provide 0.5-log giardia inactivation and 4.0-log
virus inactivation. Please contact Jamie Douglas prior to switching to free chlorine CT for disinfection.
Approval conditions related to Chapters NR 810 and NR 811, Wis. Adm. Code:
1. A resident project representative shall be designated by the water supply owner or by the agent retained
by the owner. The resident project representative shall be knowledgeable regarding the proposed
construction and be able to ensure the improvements are being constructed in accordance with the
department approved plans, specifications, and conditions of the approval. The project representative
shall be present on the work site as needed to assure proper construction and installation of the
improvements. (s. NR 811.11, Wis. Adm. Code)
2. After construction, maintenance, repair or modification, waterworks facilities shall be disinfected by
procedure outlined in the applicable AWWA standards for wells, water mains, storage facilities or
treatment facilities. Waterworks may not be placed in service until bacteriological samples have
established that the water is bacteriologically safe. (s. NR 810.09(4), Wis. Adm. Code)
3. The maximum allowable air ozone concentration in the destruction unit discharge is 0.1 ppm by volume.
(s. NR 811.54(5)(c), Wis. Adm. Code)
4. A positive closing plug or butterfly valve and a leak-proof backflow prevention check valve system shall
be provided in the piping between the generator and the contactor. (s. NR 811.54(7)(c), Wis. Adm. Code)
5. Ozone monitors shall be installed and maintained to measure ozone concentrations in both the feed-gas
and the off-gas from the contactor and the off-gas from the destruct unit. (s. NR 811.54(8)(g), Wis. Adm.
Code)
6. A dew point alarm and shutdown shall shut down the generator in the even the system dew point exceeds
-60°C. (s. NR 811.54(9)(a), Wis. Adm. Code)
7. An ozone generator cooling water flow alarm and shutdown shall shut down the generator in the even that
cooling water flows decrease to the point that generator damage could occur. (s. NR 811.54(9)(c), Wis.
Adm. Code)
8. A sign shall be posted indicating “no smoking, oxygen in use” at all entrances to the treatment plant. In
addition, no flammable or combustible materials shall be stored within the oxygen generator areas. (s. NR
811.54(10)(f), Wis. Adm. Code)
9. The owner or owner’s agent shall provide notification to Jamie Douglas from the department’s Appleton
office upon completion of the improvements so that she can inspect the completed improvements and
issue written authorization prior to placing the improvements in service, if she deems necessary. (s. NR
810.26 (1), Wis. Adm. Code)
Approval constraints: The project was reviewed in accordance with ss. 281.34 and 281.41, Wis. Stats., for
compliance with Chapters NR 108, NR 810, NR 811 and NR 820, Wis. Adm. Code and is hereby approved in
accordance with ss. 281.34 and 281.41, Wis. Stats., subject to the conditions listed above. This approval is valid
for two years from the date of approval. If construction or installation of the improvements has not commenced
within two years the approval shall become void and a new application must be made and approval obtained prior
to commencing construction or installation.
This approval is based upon the representation that the plans submitted to the department are complete and
accurately represent the project being approved. Any approval of plans that do not fairly represent the project
because they are incomplete, inaccurate, or of insufficient scope and detail is voidable at the option of the
department.
Project Number: W-2024-0716 Page 6 of 6
Be advised that this project may require permits or approvals from other federal, state or local authorities. For
example, a certificate of authority from the Public Service Commission of Wisconsin may be required per s.
196.49, Wis. Stats. and ch. PSC 184, Wis. Adm. Code.
Appeal rights: If you believe that you have a right to challenge this decision, you should know that the
Wisconsin Statutes and administrative rules establish time periods within which requests to review department
decisions must be filed. To request a contested case hearing pursuant to s. 227.42, Wis. Stats., you have 30 days
after the decision is mailed, or otherwise served by the department, to serve a petition for hearing on the Secretary
of the Department of Natural Resources. Requests for contested case hearings must be made in accordance with
ch. NR 2, Wis. Adm. Code. Filing a request for a contested case hearing does not extend the 30 day period for
filing a petition for judicial review. For judicial review of a decision pursuant to ss. 227.52 and 227.53, Wis.
Stats., you must file your petition with the appropriate circuit court and serve the petition on the department
within 30 days after the decision is mailed. A petition for judicial review must name the Department of Natural
Resources as the respondent.
STATE OF WISCONSIN
DEPARTMENT OF NATURAL RESOURCES
For the Secretary
McCrea J. Baker, P.E.
Public Water Engineering Section
Bureau of Drinking Water and Groundwater
cc: Steve Gohde – Assistant Director of Public Works/ City Engineer, City of Oshkosh
Robert Dreikosen – Treatment Plant Operations Supervisor, City of Oshkosh
Brad Rokus – OIC, City of Oshkosh
Linda Mohr – Jacobs Engineering, Milwaukee
Todd Elliot – Jacobs Engineering, Minneapolis, MN
Jamie Douglas – DNR, Appleton
JaNelle Merry – DNR, Green Bay
PSC – Madison