Performance of a Carbon Dioxide Injection System at a Navigation Lock to Control the Spread of Aquatic Invasive Species

Zolper, Thomas J.; Smith, David L.; Jackson, P. Ryan; Cupp, Aaron R.

doi:10.1061/(ASCE)EE.1943-7870.0001987

Open access

Technical Papers

Feb 10, 2022

Performance of a Carbon Dioxide Injection System at a Navigation Lock to Control the Spread of Aquatic Invasive Species

Authors: Thomas J. Zolper [email protected], David L. Smith, P. Ryan Jackson https://orcid.org/0000-0002-3154-6108, and Aaron R. CuppAuthor Affiliations

Publication: Journal of Environmental Engineering

Volume 148, Issue 4

https://doi.org/10.1061/(ASCE)EE.1943-7870.0001987

PDF

Abstract

Natural resource agencies need effective strategies to control the spread of aquatic invasive species (AIS) such as invasive fish, which can expand their range using rivers as hydrological pathways to access new areas. Lock and dam structures within major rivers are prospective locations to deploy techniques, such as carbon dioxide (

{CO}_{2}

) infusion into lock water, that could impede upstream AIS migration without disrupting vessel passage and lock operation. The current pesticide label for

{CO}_{2}

in the United States allows injections of

100 - 150 mg / L {CO}_{2}

as a behavioral deterrent treatment for invasive carps. This research describes the first operationalizing and testing of a

{CO}_{2}

injection and manifold distribution system at a 1,548,000-L navigation lock chamber on the Fox River near Kaukauna, Wisconsin, USA. Two chemical distribution manifolds located on the floor and wall of the chamber were independently tested to quantify mixing time, mixing homogeneity, injection efficiency, and operational power requirements under a range of operating parameters. Both manifold configurations were able to meet most performance benchmarks established during previous fish behavior studies. Certain limitations were exhibited and quantified for both manifold configurations in terms of mixing homogeneity and operational power. This research details the design and performance of

{CO}_{2} - to - water

infusion systems that could be used to deter the spread of AIS at navigation pinch-points. These results may inform future

{CO}_{2}

system designs and operating conditions to support natural resource management plans to limit the spread of AIS.

Introduction

Invasive carps, including silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis), have migrated throughout the Mississippi River Basin since the 1970s and are now expanding into other large rivers basins in the United States. Recent expansion toward the Great Lakes Basin has raised conservation and economic concerns related to how invasive carps could adversely affect the $7-billion Great Lakes fishing industry (Conover et al. 2007). Lock and dam structures positioned throughout these interconnected waterways have been identified as key management locations to limit or block the upstream migration of invasive carps toward the Great Lakes. Permanent lock closure was one possible solution to block fish passage, but this approach was not considered a viable option to many stakeholders due to the negative economic consequences of limiting waterway access (Schwieterman 2010, 2015). Therefore, researchers and resource managers have focused on the development of other fish deterrents that could be implemented at lock structures to reduce upstream migration of invasive carps while maintaining a fully operational waterway.

Several technologies have been explored to prevent fish passage through locks (Noatch and Suski 2012; Zolper et al. 2019). For example, invasive carp deterrent systems such as underwater acoustics and electric barriers have shown promise under various scenarios (Cooper et al. 2021; Jones et al. 2021; Noatch and Suski 2012). Underwater speakers can be used to broadcast acoustics in certain areas to elicit strong behavioural responses from invasive carps (Bzonek et al. 2021; Vetter et al. 2015, 2017). Similarly, electric barriers create an electrified field that deters and immobilizes fish as they attempt to move upstream (Egly et al. 2021). Each deterrent method has benefits and challenges related to target species responsiveness, acclimation to the deterrent stimulus, variable efficacy with fish size, human safety concerns, and operational costs. Consequently, supplementing existing control methods and further developing additional methods would be beneficial in deterring upstream movements of invasive carps.

Chemosensory stimuli, such as carbon dioxide (

{CO}_{2}

) infused into water, offer an alternative approach to deter carp movements. The concept is to infuse

{CO}_{2}

into water at specific areas (e.g., lock structures) to repel or immobilize invasive carps. Research has already demonstrated that invasive carps respond strongly to localized

{CO}_{2}

plumes (Cupp et al. 2017a, 2021; Donaldson et al. 2016; Tix et al. 2018), and infusion into water could be accomplished at lock structures with minimal expected effects to navigation or lock operation (Zolper et al. 2019). Aspects of

{CO}_{2}

deterrents may also address limitations with other deterrent technologies due to its nonselectivity across species and taxa, efficacy across most life stages, limited evidence of acclimation to the chemical stimulus, low cost, wide availability, and low risk to human health (Suski 2020). Pesticide registration with the US Environmental Protection Agency in 2019 has further facilitated continued development and created a legal pathway to apply

{CO}_{2}

as an approved pesticide for invasive carp control in the United States (USEPA 2019). However, much of the previous research has been limited to relatively small scales and controlled environments where

{CO}_{2}

applications were accomplished using crude gas injection methods. The next important step is to determine the feasibility of

{CO}_{2}

applications at a management scale in navigation lock structures using more purposefully engineered gas injection systems.

The transition of

{CO}_{2}

testing from controlled settings (e.g., laboratory tanks, outdoor ponds) into full-scale environments (e.g., navigation lock structures) requires additional engineering considerations that were not addressed during previous biological research. Several gas-to-liquid infusion methods, including mechanical and fluid dynamic mixers, have been developed for chemical, mechanical, and environmental engineering applications that could potentially be adapted for this new application (Bumrungthaichaichan et al. 2016; Chen et al. 2017; Fossett 1951; Fossett and Prosser 1949; Fox and Gex 1956; Lane and Rice 1982). Jet mixing stands out as a highly effective nonphysical method of mixing. It generally uses a pump to draw liquid from a chamber, pressurizes it, and reinjects it through a nozzle as a high velocity jet. The momentum of a fluid jet entrains surrounding fluid and induces efficient mixing within the chamber. Jet driven liquid-gas mixing also produces multiphase flow that can alter fluid properties, resulting in cavitation, efficiency losses, and other phenomena (Freudigmann et al. 2017; Liu et al. 2017; Loeb 2017; Tian and Van de Ven 2017).

The performance of machinery used in mixing applications is often gauged by the uniformity, concentration, and efficiency of the processes. Mixing performance can be quantified in two ways: (1) “mixing homogeneity” describes the uniformity of

{CO}_{2}

concentrations within the lock using the variance in measured

{CO}_{2}

at all monitoring points; and (2) “injection efficiency” is the ratio of dissolved

{CO}_{2}

to injected

{CO}_{2}

, an indicator of gas-to-liquid infusion ability. Both mixing homogeneity and injection efficiency are affected by many factors, including the chamber volume, injection velocity, fluids being mixed, jet injection angles, nozzle geometry, manifold configurations, operating pressure, and Reynolds number (Bumrungthaichaichan et al. 2016; Dinsmore et al. 2017; Fox and Gex 1956; Grenville and Tilton 2011; Lane and Rice 1982; Maruyama 1986; Patwardhan and Gaikwad 2003).

Nozzle geometry also directly affects mixing time, operating pressure, and flow rate, and a variety of nozzle designs have been evaluated with circular apertures (Cui et al. 2015; Yang et al. 2013), noncircular apertures (Majamaki et al. 2003; Nikitopoulos et al. 2003; Quinn 2005; Smith et al. 1997; Yu et al. 2004; Zaman et al. 1994; Zhdanov and Hassel 2012), and vortex-inducing nozzle covers (Bradbury and Khadem 1975; Foss and Zaman 1999; Reeder and Samimy 1996; Samimy et al. 1993; Zaman et al. 1994; Zhdanov and Hassel 2012). Fox and Gex (1956) demonstrated that good mixing performance can be attained by maximizing a nozzle’s “momentum flux,” the product of velocity and mass flow rate through an aperture (Bumrungthaichaichan et al. 2016; Fox and Gex 1956). Manifolds are used to divide a single fluid stream into multiple outflow streams, and detailed studies of diverse manifold designs, including customized designs, are available in the scientific literature (Bajura and Jones 1976; Bajura 1971; Gandhi et al. 2012; Hassan et al. 2014; Majumdar 1980; Pathapati et al. 2016; Subaschandar and Sakthivel 2016; Tong et al. 2009).

The goal of this research is to evaluate the performance of a

{CO}_{2}

injection system at a navigation lock structure on the Fox River near Kaukauna, Wisconsin, USA. System performance was evaluated based on several metrics that characterized the efficiency and timing of this engineered system to reach target concentrations. A target concentration range of

100 - 150 mg / L {CO}_{2}

was established based on previous fish behavior testing and discharge allowances on state and federal permits (USEPA 2019). Two manifold distribution types were tested that were designed as possible options to treat the lock without obstructing lock operation. Previous testing in outdoor ponds detailed the mixing performance of singular floor-based and wall-based

{CO}_{2} - to - water

injection manifolds in a closed simulated lock chamber (Zolper et al. 2019). The present research uses a system of manifolds, activated in different combinations, to generate a uniform vertical and lateral

{CO}_{2}

field with the intent to prevent fish from entering the lock chamber or force resident fish downstream. This research introduces several new factors to previous research, including full-scale commercial injection equipment, multiple combinations of manifolds, and operation in a management applicable setting in a lock structure.

Experimental Setup and Methods

The

{CO}_{2}

infusion experiments were designed to simulate, as closely as possible but without vessels, the treatment of a lock chamber with

{CO}_{2}

during an upstream lock operation. In a typical upstream passage of a vessel through a navigational lock, the lock must be at tailwater level (downstream water level) with the downstream miter gates open to allow the vessel to enter. Once the vessel is moored in the lock, the downstream gates are closed and the chamber is filled to the head-water level. Upon attaining the head-water level, the upstream miter gates are opened and the vessel can continue upstream. To prevent upstream migration of aquatic invasive species during this process, the lock water can be infused with

{CO}_{2}

before the vessel enters the lock to (1) drive fish out of the chamber and into the downstream pool; and (2) to deter any fish from entering the lock with the vessel. In these experiments, we simulate the pretreatment of the lock chamber with

{CO}_{2}

without the complication of vessel passage.

The objective of these experiments was to evaluate the ability of the

{CO}_{2} - to - water

infusion system to attain a uniform target concentration of

100 mg / L

throughout a lock chamber. Multiple combinations of operating parameters using wall-based and floor-based distribution manifolds were tested to generate diverse flow fields. This resulted in a greater number of operating parameters in comparison to the earlier research (Zolper et al. 2019) and substantially increased overall complexity. Certain parameters were constrained by the greater scope of activities and regulations of the participating agencies, including the US Army Corps of Engineers (USACE), US Geological Survey (USGS), and Wisconsin Department of Natural Resources (WDNR). The maximum allowable

{CO}_{2}

concentration of

150 mg / L

in a lock chamber was established by the WDNR under an approved National Pollutant Discharge Elimination System (NPDES) permit based on state requirements in compliance with Federal Clean Water Act standards.

A temporary

{CO}_{2} - infusion

system with water distribution manifolds was constructed and tested at Kaukauna Lock #2 on the Fox River located in Kaukauna, Wisconsin, as shown in Fig. 1. The test site was entirely on property that was owned and operated by the Fox River Navigational System Authority (FRNSA). Site access approval was gained from FRNSA, and all necessary local, state, federal and historical permits were obtained prior to construction and testing. Construction was completed by a private firm that specialized in water distribution systems. Experiments were performed from August 5, 2019, through September 6, 2019.

Fig. 1. Research and equipment location in Kaukauna, Wisconsin (N 44.283° W 88.258°).

The lock chamber was approximately 51.82 m (170 ft) long and 11.12 m (36.5 ft) wide at the top, tapering down to 10.72 m (35.2 ft) wide at the bottom (Fig. 2). The upstream (west) miter gates were closed during the experiments, and each gate was 5.7 m (18.7 ft) long and met in the middle. The downstream (east) miter gates were open during the experiments: the line between their hinges divided the lock chamber from the downstream reservoir. The Kaukauna Lock #2 measurements (Fig. 2) were accurate to ± 50.8 millimeters (mm) (

\pm 2 in.

). Thus, the volume enclosed by the chamber and upstream miter gate was about

2,920,000 \pm 47,000 L

(

771,000 \pm 12,400 gal.

) at head-water level (5.08 m or 16.7 ft) and

1,548,000 \pm 37,000 L

(

409,000 \pm 9,700 gal.

) at tail-water level (2.64 m or 8.7 ft). For reference, a typical 183-m (600-ft)-long commercial navigation lock has a tailwater volume of approximately 20 times that of Kaukauna Lock #2.

Fig. 2. Dimensions and major equipment in Fox River Lock #2 in Kaukauna, Wisconsin.

An open-loop

{CO}_{2}

injection system was designed for these experiments (Fig. 2). A diesel-powered pump drew near-bottom water from the northwest corner of the chamber at the upstream end of the lock, lifted it approximately 6.1 m (20 ft), passed it through a filter and into parallel mixing chambers where

{CO}_{2}

was added to carrier water under a prescribed pressure differential, and then distributed the

{CO}_{2} - enriched

carrier water in the lock chamber using a series of manifolds that were adjusted for each experiment. The pump intake was positioned approximately 203.2 mm (8 in.) above the floor of the lock, the same height as the discharge of the wall and floor manifolds, resulting in a net pumping height of 0 mm. The piping networks, pressurized solution feed (PSF), manifolds, and nozzles were the primary causes of the system head losses. All treatments occurred with the chamber at tail-water level and downstream (east) miter gates open. After each experiment, the downstream miter gates were closed and the lock was filled to dilute excessive

{CO}_{2}

concentrations before discharging the treated water downstream in preparation for the next experiment.

The pump produced water flow rates (

{\dot{V}}_{H 2 O}

) from 6,810 to

12,110 L / \min

(1,800 to

3, 200 gal . / \min

) in accordance with the requirements for the experiment. A

{TOMCO}_{2}

Systems (Loganville, Georgia) PSF was used to infuse

{CO}_{2}

into the carrier water from the pump at mass flow rates of

{\dot{m}}_{CO 2} = 1,134

to

1,588 kg / h

(2,500 to

3,500 lb / h

). The

{CO}_{2} - infused - water

was mixed into the lock chamber using either a series of wall-based or floor-based manifolds, shown in Fig. 2.

High-density polyethylene (HDPE) was used for all piping except for the floor manifold, which used polyvinyl chloride (PVC). The pump intake and outflow pipes were made of 304.8-mm (12-in.) HDPE. Downstream from the PSF, 406.2-mm (16-in.) HDPE pipe was used to divide the flow into two streams (Fig. 2). The downstream (east) pipes provided flow to four wall manifolds. The upstream (west) pipes provided flow to four wall manifolds and included a valve to provide flow to the floor manifold. The floor manifold was made of 203.2-mm (8-in) schedule 40 PVC and was affixed to the bottom using distributed weights. The wall manifold branches used 406.4-mm to 203.2-mm (16-in. to 8-in.) T-fittings and elbows to connect to the eight wall manifold dropdowns (Figs. 2 and 3). Several gate valves were used to control the water flow to the full floor manifold or a maximum of four wall manifolds at a time. The pump intake and discharge pipes were placed on one side of the chamber to minimize obstructions to lock personnel.

Fig. 3. Overhead view of wall manifold showing six nozzles each.

The wall manifolds were designed to use the kinetic energy and turbulence of a series of jets to induce mixing and diffusion of

{CO}_{2}

into the water. The design is also adaptable to flush-mounted scenarios that would not physically interfere with lock operation or vessel passage. Each wall manifold was constructed from 203.2-mm (8-in.) HDPE and designed to produce six equal-discharge jets from TOMCO2 Systems (Loganville, Georgia) using cast 304 stainless steel nozzles spaced 762 mm apart, as shown in Figs. 3 and 4.

Fig. 4. Cross-section of the ${TOMCO}_{2}$ Systems nozzles used on the eight wall manifolds.

Converging nozzles were selected to maximize momentum flux, which has been shown to enhance long-range mixing (Fox and Gex 1956). The nozzles had 76.2-mm (3-in.) inlets and 23.4-mm (

59 / 64 - in.

) outlets to allow the necessary back-pressure for proper

{CO}_{2}

dissolution and water flow rate. All nozzles discharged horizontally toward the south wall and were located approximately 203.2 mm (8 in.) above the bottom of the lock chamber. In total, eight wall manifolds (designated A–G) were evenly spaced at 5.33 m (17.5 ft) on center along the north wall of the lock chamber (Fig. 5). Combinations of two, three, and four manifolds were variously activated for individual experiments during the test period.

Fig. 5. Overhead view of lock showing the eight wall manifolds alphabetized from upstream (west) to downstream (east) and the floor manifold depicting the main branch and four evenly spaced branches running parallel to the length of the lock.

The floor manifold was composed of a 406.4-mm (16-in.) HDPE main branch that equally distributed the

{CO}_{2} - infused

water into four 203.2-mm (8-in.) PVC side branches with center-to-center spacing of 2.67 m (105 in.), as shown in Fig. 5. Each 48.77-m (160-ft)-long side branch ran parallel to the length of the lock, and branches were connected to one another at the downstream end of the lock by a 203.2-mm (8-in.) PVC pipe. Seventy-two 6.35-mm (

1 / 4 - in.

) holes (

d_{H 2 O}

) were drilled into the tops of the four side branches at a spacing of 508 mm (20 in.) each (288 total). The main branch also had twelve 6.35-mm (

1 / 4 - in.

) holes spaced at 609.6 mm (24 in.) over its 8-m (26.25-ft) length. Thus, a total of 300 orifices in the floor manifold distributed

{CO}_{2} - enriched

water throughout the lock chamber approximately 203.2 mm above the floor of the lock.

Flow meters, pressure gauges, and control valves allowed the system to be configured and operated for a variety of experimental conditions. The pump was fitted with a vacuum pressure gauge at the intake port and an operating pressure gauge at the outlet port (Fig. 2), both with accuracies of

\pm 6.9 kPa

(

\pm 1 psi

). The pressure gauge readings at the pump intake port

P_{in}

and pump outlet port

P_{out}

were used to determine the operating pressure of the system

P_{oper}

[Eq. (1)]

P_{oper} = P_{out} - P_{in}

(1)

A Fluid Components International (San Marcos, California)

{CO}_{2}

mass flowmeter (accuracy

\pm 1 %

of reading [

lb / h

]) was used to measure

{CO}_{2}

flow rate into the PSF every minute during experiments (Fig. 2). A Hach sc200 (Loveland, Colorado) pH and temperature sensor measured the acidity and temperature, respectively, of the incoming and outgoing water of the PSF to

\pm 0.1 %

of full scale at 25°C. Two Bourdon pressure gauges measured the PSF of incoming and outgoing water pressure with an accuracy of

\pm 6.9 kPa

(

\pm 1 psi

). The volume flow rate of water was measured at three points in the system (Fig. 2) using Greyline Instruments (Largo, Florida) Doppler Flow Meters (DFM 6.1) with an accuracy of

\pm 75.7 L / \min

(±20 gal./min). The primary flowmeter, located on the 406.4-mm (16-in.) HDPE pipe between the pump and the PSF, measured the total flow through the piping system. Two additional flowmeters were also placed on the 406.4-mm (16-in.) lines feeding each bank of manifolds (Fig. 2). A portable Greyline Doppler Flow Meter (DFM 6.1) calibrated to 203.2-mm (8-in.) pipes was used to assess the flow rate of the dropdowns to individual manifolds. Flow rates were logged every 10 s on all meters.

The distribution of dissolved

{CO}_{2}

in the lock chamber was measured during each experiment using an array of pH sensors on multiparameter sondes with real-time telemetry. Ten YSI (Yellow Springs, Ohio) multiparameter sondes (eight YSI Model 600XLM and two YSI/Xylem EXO2) were divided between five Ocean Science (North Falmouth, Massachusetts) tethered boats positioned on taglines throughout the lock chamber (Fig. 6). Each tethered boat was equipped with two sondes positioned at depths of 0.914 m (3 ft) and 1.828 m (6 ft) below the free surface, a Campbell Scientific (Logan, Utah) CR6 data logger, a RF407 high-speed 900-MHz spread-spectrum radio, a 12-volt battery, and a 10-W solar panel and regulator. The radios allowed wireless transmission of real-time data at 5-s intervals from all instruments to a single laptop computer with custom display for real-time feedback during the experiments. A pulley driven hand line attached to each boat allowed the boat to be positioned at any point along the static tagline by a single person. During testing, the boats were simultaneously repositioned from south (S), center (C), and north (N) stations at carefully timed intervals to assess the variation of the

{CO}_{2}

field and other basic water-quality properties (temperature, specific conductance, and dissolved oxygen). Tethered boat #3, located near the center of the lock chamber (Fig. 6), was equipped with the EXO2 sondes, which included additional sensors not found on the 600XLM sondes (optical dissolved oxygen, turbidity, total algae, and phycocyanin sensors).

Fig. 6. Diagram of the positions and spacing of five tethered boats carrying two pH sensors each in Fox River Lock #2 in Kaukauna, Wisconsin. Yellow lines indicate the taglines for the tethered boats and the north, south, and central stations occupied by each boat.

Dissolved

{CO}_{2}

concentration (mg/L) was computed from pH measurements using a

{CO}_{2} - pH

regression equation [Eq. (2)] and water samples collected from the Fox River Lock #2 in Kaukauna, Wisconsin, at the beginning and end of the experiments (July 26, 2019, and September 5, 2019, respectively). Details of the development of Eq. (2) are given in the appendix

C_{CO 2} = 3.361 \cdot 10^{8} \cdot e^{- 2.323 \cdot pH}

(2)

The multiparameter sondes were three-point calibrated using pH 4, 7, and 10 standards at the beginning of every week, and all sensors (except temperature) were calibrated. The thermistors on the sondes do not require calibration but are checked annually in a thermal bath. During calibration, sonde clocks were synchronized with the master clock for the experiments.

Design of Experiments—Test Plan

Previous research showed that water flow rate

{\dot{V}}_{H 2 O}

and

{CO}_{2}

mass flow rate

{\dot{m}}_{CO 2}

have the greatest influence on the performance of the floor and wall manifolds (Zolper et al. 2019). A design of experiments (DOE) full-factorial approach was used to extricate their respective influences on the performance of the manifold systems (Box et al. 2005). Sixteen experiments were identified using four manifold configurations at four flow rates each, as shown in Table 1. The pump provided stable water flow rates at pump speeds of

ω = 1,200

and 1,800 RPM, which corresponded to different water flow rates whether using floor manifolds or combinations of two, three, or four wall manifolds. The PSF was set to steady

{CO}_{2}

mass flow rates of

{\dot{m}}_{CO 2} = 18.9

and

26.5 kg / \min

(2,500 to

3,500 lb / h

) with negligible effects on water flow rates. It was found that operating four wall manifolds at low pump speed produced insufficient operating pressure to allow the PSF to efficiently infuse

{CO}_{2}

; therefore, those experiments were not pursued.

Table 1. Design of experiments factorial design settings showing water volume flow rates (

{\dot{V}}_{H 2 O}

) and

{CO}_{2}

mass flow rates (

{\dot{m}}_{CO 2}

) of the floor manifold and three configurations of wall manifolds

Manifold	Operating parameters	Units	DOE factorial design settings
Manifold	Operating parameters	Units	1	2	3	4
Floor	Volume flow rate ${\dot{V}}_{H 2 O}$	( $L / \min$ )	8,330	8,330	11,360	11,360
	Volume flow rate ${\dot{V}}_{H 2 O}$	( $gal. / \min$ )	2,200	2,200	3,000	3,000
	Mass flow rate ${\dot{m}}_{CO 2}$	( $kg / \min$ )	18.9	26.5	18.9	26.5
	Mass flow rate ${\dot{m}}_{CO 2}$	( $lb / h$ )	2,500	3,500	2,500	3,500
Wall 2 manifolds	Volume flow rate ${\dot{V}}_{H 2 O}$	( $L / \min$ )	6,810	6,810	10,600	10,600
	Volume flow rate ${\dot{V}}_{H 2 O}$	( $gal. / \min$ )	1,800	1,800	2,800	2,800
	Mass flow rate ${\dot{m}}_{CO 2}$	( $kg / \min$ )	18.9	26.5	18.9	26.5
	Mass flow rate ${\dot{m}}_{CO 2}$	( $lb / h$ )	2,500	3,500	2,500	3,500
Wall 3 manifolds	Volume flow rate ${\dot{V}}_{H 2 O}$	( $L / \min$ )	8,330	8,330	11,360	11,360
	Volume flow rate ${\dot{V}}_{H 2 O}$	( $gal. / \min$ )	2,200	2,200	3,000	3,000
	Mass flow rate ${\dot{m}}_{CO 2}$	( $kg / \min$ )	18.9	26.5	18.9	26.5
	Mass flow rate ${\dot{m}}_{CO 2}$	( $lb / h$ )	2,500	3,500	2,500	3,500
Wall 4 manifolds	Volume flow rate ${\dot{V}}_{H 2 O}$	( $L / \min$ )	9,080^a	9,080^a	12,110	12,110
	Volume flow rate ${\dot{V}}_{H 2 O}$	( $gal. / \min$ )	2,400^a	2,400^a	3,200	3,200
	Mass flow rate ${\dot{m}}_{CO 2}$	( $kg / \min$ )	18.9^a	26.5^a	18.9	26.5
	Mass flow rate ${\dot{m}}_{CO 2}$	( $lb / h$ )	2,500^a	3,500^a	2,500	3,500

Note: The wall manifolds were operated in various combinations of letters A–G, as shown in Fig. 5.

a

Not completed due to insufficient operating pressure.

Test configurations are identified by the following nomenclature: manifold type [floor (F) or wall (W)], wall–manifold combinations (e.g., A-B-C-D; for W manifold type only), water volumetric flow rate (

{\dot{V}}_{H 2 O}

), and

{CO}_{2}

mass flow rate (

{\dot{m}}_{CO 2}

) in US customary units. Therefore, a test configuration using wall manifolds A, C, E, and G at

{\dot{V}}_{H 2 O} = 3,200 gal. / \min

, and

{\dot{m}}_{CO 2} = 2,500 lb / h

is designated “W A-C-E-G 3200-2500”. Meanwhile, a test configuration of the floor manifold at

{\dot{V}}_{H 2 O} = 3,000 gal. / \min

, and

{\dot{m}}_{CO 2} = 2,500 lb / h

is designated “F 3000-2500”.

General Experimental Procedures

The full scope of the research also includes fish behavioral studies, which largely dictated the duration for each trial. Therefore, nearly 2 h were allocated for each experiment to perform baseline pH measurements and track tagged fish using acoustic fish telemetry. Baseline measurements of

{CO}_{2}

concentration were collected prior to injection (

t < 0 \min

). At about

t = - 10 \min

, the pump was set to the nominal water flow rate to allow enough time to develop a stable flow field. At the beginning of

{CO}_{2}

injection (

t = t_{0} = 0 \min

), the PSF was set to the nominal

{CO}_{2}

mass flow rate. The

{CO}_{2}

injection was stopped when the measured

{CO}_{2}

reached a threshold concentration of

150 mg / L

at any sensor on the tethered boats. This was a requirement to comply with issued permits from WDNR for conducting this research project. In practical administration, injection would continue until all locations within the lock reached the desired concentrations and not just at any one sensor. Measurements continued for up to 90 min after the

{CO}_{2}

injection began (

t > 0 \min

). The five tethered boats with pH sensors simultaneously measured for 3 min at each station in the lock (north, center, south) throughout the trial period. The following sequence of activities were undertaken to simulate upstream lock changes:

1.

At

t = - 40 \min

: Baseline testing: Tethered boats start at center stations of lock, then move to north stations (

t = - 37 \min

), back to center stations (

t = - 34 \min

), to south stations (

t = - 31 \min

), and return to center stations (

t = - 28 \min

).

2.

At

t = - 10 \min

: Pump starts and attains desired flow rate.

3.

At

t = - 1 \min

: Lower miter gates open.

4.

At

t = t_{0} = 0 \min

:

{CO}_{2}

injection begins.

5.

Over the course of the test, the tethered boats are moved to the following positions:

•

(

0 < t < 3 \min

) center

•

(

3 < t < 6 \min

) north

•

(

6 < t < 9 \min

) center

•

(

9 < t < 12 \min

) south

•

(

12 < t < 15 \min

) center

•

(

15 < t < 18 \min

) north

•

(

18 < t < 21 \min

) center

•

(

21 < t < 24 \min

) south

•

(

24 < t < 27 \min

) center

•

(

27 < t < 30 \min

) north

6.

At

t = t_{inj} = Δ t

(variable):

{CO}_{2}

injection ends when a concentration of

150 mg / L

is reached. Injection times ranged from about 3:00 min to 13:00 min.

7.

Upon completion of each test, downstream (east) miter gates are closed, the lock is filled to dilute the

{CO}_{2}

, and the lock is drained to prepare for another test.

The

{CO}_{2}

concentration increased continually during the injection period, an inherently transient process, under the WDNR restrictions. The pump was deliberately started before the

{CO}_{2}

injection to generate a quasisteady flow field and thereby prevent confounding of steady-state water flow with transient

{CO}_{2}

injection in the data analysis. After completion of each test, the treated lock was filled with water from upstream to dilute the

{CO}_{2}

before release. Afterward, the lock chamber was drained to tail-water level and prepared for the next trial. Only two trials per day were permitted by WDNR. Several tests were undertaken over the course of 6 weeks with several replications to assess consistency.

Results and Discussion

Measurements of floor and wall manifolds across various water and

{CO}_{2}

flow rates were used to quantify the mixing and injection efficiency of each configuration. Comparisons of the performance were used to identify considerations for the best manifolds and operating parameters for a permanent full-scale installation. A leakage rate of about

220 L / s

(

53 gal. / s

) was measured through the upstream miter gate by an acoustic Doppler current profiler. This introduction of untreated water from the upper reservoir appears to be present in some of the following figures as lower

{CO}_{2}

concentrations near the upstream region.

Acidity and ${CO}_{2}$ Content

Fig. 7(a) depicts typical water acidity measurements (pH) of the wall manifolds A-B-C-D operating at

12,110 L / \min

(

3,200 gal. / \min

) and

{CO}_{2}

flow rate of

18.9 kg / \min

(

2,500 lb / h

). Fig. 7(b) shows the corresponding

{CO}_{2}

concentration calculated from the acidity measurements using

pH - {CO}_{2}

calibration curve [Eq. (2)]. Data from the near-bed (bottom) pH sensors on tethered boats 1, 3, and 5 are shown in the figures. The bottom sonde measurements are areas of concern with respect to

{CO}_{2}

treatment. Floor–wall interfaces inhibit mixing, and

{CO}_{2}

bubbles rise, resulting in lower

{CO}_{2}

concentrations at lower edges of the chamber. Fish behavior studies show that these could become passages for invasive fish. Data collected in the lock by tethered boat 1 using the bottom sensor 1.828 m (6 ft) below the free surface were designated “Line 1 Bottom” and abbreviated as “L1B.” Data collected in the lock at the top sensors 0.914 m (3 ft) below the free surface are omitted for clarity in the figures. Figs. 7(a and b) show the stable baseline pH and

{CO}_{2}

concentration in the 10-min interval preceding the commencement of

{CO}_{2}

injection. They also show a clear delay in treatment of the downstream (east) end of the lock until about 12 min after injection began (

t_{0} = 0 \min

). This is attributed to the concentration of manifolds and the circulation field generated by the pump intake near the upstream (west) miter gate.

Fig. 7. Measurements of (a) water acidity; and (b) corresponding ${CO}_{2}$ concentration in the lock chamber for trial W A-B-C-D 3200-2500 from the tethered boats on lines (“L”) 1, 3, and 5 (bottom “B” sensors), as shown in Fig. 5.

Fig. 7(a) shows a precipitous drop in pH as soon as

{CO}_{2}

injection began (

t = 0

), and Fig. 7(b) shows the corresponding increase in

{CO}_{2}

concentration. Both figures also show the minimum pH measurement [Fig. 7(a)] and corresponding peak

{CO}_{2}

concentration [Fig. 7(b)] when

{CO}_{2}

injection was ended (

Δ t = t_{inj} - t_{0} = 8 : 38 \min

), having reached the maximum permissible concentration of

150 mg / L

. The occurrence of this peak has an effect on injection time and the overall mass of

{CO}_{2}

injection into the lock. After

{CO}_{2}

injection began, the pump continued to run for 15–20 min in order to mix the

{CO}_{2} - infused

water throughout the chamber. The turbulence created by the pump enhances diffusion of

{CO}_{2}

throughout the lock while also increasing the rate of off-gassing in comparison to quiescent water (Leung et al. 2014).

The upper-axis

{CO}_{2}

concentration is set at

250 mg / L

for ease of comparison between Figs. 7–12. The uncertainty in the

{CO}_{2}

concentration was so small that it could not be clearly presented in the plots. However, the error bars shown in Fig. 18 are equally applicable to all

{CO}_{2}

concentration plots in this paper. The combination of uncertainty in acidity (

\pm 0.02 pH

) and

{CO}_{2}

concentration (± 1% of reading) increases the total uncertainty in

{CO}_{2}

concentration (

mg / L

) as acidity increases. The absolute uncertainty in

{CO}_{2}

concentration at 7.5 pH is

2.85 \pm 0.15 mg / L

, and the uncertainty at 6.5 pH is

93 \pm 5 mg / L

, giving consistent proportional uncertainty of about 5.3%.

Fig. 8. Measurements of dissolved ${CO}_{2}$ in water for the floor manifold at: (a) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 9. Measurements of dissolved ${CO}_{2}$ in water for the wall manifolds A-B at: (a) ${\dot{V}}_{H 2 O} = 10,600 L / \min$ ( $2,800 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 10,600 L / \min$ ( $2,800 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 10. Measurements of dissolved ${CO}_{2}$ in water for the wall manifolds A-B-C at: (a) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 11. Measurements of dissolved ${CO}_{2}$ in water for the wall manifolds A-C-E-G at: (a) ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 12. Approximate dissolved ${CO}_{2}$ in water at $t = 15 \min$ for wall manifolds A-B-C-D at: ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ).

Floor Manifold: Concentration versus Time

Fig. 8 depicts the

{CO}_{2}

concentrations generated by the floor manifold at the four operating conditions listed in Table 1. Figs. 8(a and b) show water flow rates of

11,360 L / \min

(

3,000 gal . / \min

) and

{CO}_{2}

flow rates of 18.9 and

26.5 kg / \min

(2,500 and

3,500 lb / h

). The repositioning of the tethered boats (every 3 min) accounts for discontinuities in the data, and some points shown in the figures were data collected during the transitions; however, repositioning the boats took less than 10 s, so multiple measurements during a transition are unlikely. Although movement of the boats created a visual discontinuity with time-series plots, this spatial interval sampling approach was important to characterize the full lock chamber relative to simply taking static measurements at a single location.

All figures exhibited a steady increase in

{CO}_{2}

concentration during the injection periods. Afterward, the readings stabilized for several minutes and then began to decrease toward the end of the test. All figures also exhibited low

{CO}_{2}

concentrations on the south (S) side of the lock at around the 10-min sampling time. The major shortcoming of the prototype floor manifold is the inadequate mixing in the stagnation regions, especially along the south wall of the lock. The south discharge pipe of the floor manifold was 1.37 m (54 in.) from the lock wall with holes drilled to eject vertically, which provided little horizontal momentum flux. This allowed for regions of low

{CO}_{2}

concentration to occur in the corners of the lock that could host undesirable fish trying to avoid the high concentrations. This can be remediated by placing the pump intake more centrally in the lock and placing some side branches or directing the nozzle direction nearer to the outside walls to provide a more uniformly mixed treatment.

Wall Manifolds: Concentration versus Time

The wall manifold system, like the floor manifold, was designed to operate at the water and

{CO}_{2}

flow rates listed in Table 1. However, unlike the floor manifold, which treated the entire lock chamber at one time, wall manifolds could be operated in combinations of 2–4 manifolds during testing, which affected the possible water volume flow rates and operating pressures. We evaluated combinations of manifolds to generate

{CO}_{2}

infusion zones that would flush fish from the upstream (west) region of the lock through the downstream (east) miter gates. This scenario is likely most applicable to fish control applications within lock chambers. Therefore, the results depict combinations of both upstream concentrated manifolds (A-B-C: Figs. 9 and 10) and alternating (distributed) manifolds (A-C-E-G: Fig. 11), referring to Fig. 5.

Fig. 9 depicts the

{CO}_{2}

concentrations generated by the wall manifold combination A-B operating at the parameters listed in Table 1. Figs. 9(a and b) show water flow rates of

10,600 L / \min

(

2,800 gal. / \min

) and

{CO}_{2}

flow rates of 18.9 and

26.5 kg / \min

(2,500 and

3,500 lb / h

). Shortly after injection started, the figures clearly showed high

{CO}_{2}

concentrations on the upstream (west) end of the lock (L1B) and low concentrations at the downstream (east) end of the lock (L5B). Near the end of the test,

{CO}_{2}

approached nearly uniform concentrations around

50 mg / L

. This

{CO}_{2}

gradient would likely push any fish within the lock downstream to prevent entry into the upstream regions of the river. The large

{CO}_{2}

spike in the first few minutes of each trial shows why the injection times were short because the high

{CO}_{2}

mass flow rate (

{\dot{m}}_{CO 2} = 26.5 kg / \min

) attained a concentration (

\frac{26.5 \frac{kg}{\min}}{6,810 \frac{L}{\min}} = 3,891 \frac{mg}{L}

) that quickly exceeded target thresholds. The lower

{CO}_{2}

flow rate shown in Fig. 9(a) allowed the injection to continue about 50% longer than the comparatively high flow rate in Fig. 9(b), but both were substantially shorter than the injection times for the floor manifold, resulting in lower injected and dissolved

{CO}_{2}

masses.

Fig. 10 depicts the

{CO}_{2}

concentrations generated by the wall manifold combination A-B-C operating at the parameters listed in Table 1. Figs. 10(a and b) show water flow rates of

11,360 L / \min

(

3,000 gal. / \min

) and

{CO}_{2}

flow rates of 18.9 and

26.5 kg / \min

(2,500 and

3,500 lb / h

). Figs. 10(a and b) show early

{CO}_{2}

concentration peaks similar to those shown in Fig. 9, which generally correspond to

{CO}_{2}

injection times. However, because the

{CO}_{2}

was divided among three manifolds, the injection was able to continue nearly twice as long before exceeding regulatory limits. This means that a greater mass of

{CO}_{2}

was able to be injected with three manifolds. Fig. 10 also shows the same upstream-to-downstream (west-to-east) flushing field as Fig. 9. This could be used to flush fish downstream from the lock. At the end of the trial, Fig. 10(b) shows a higher average

{CO}_{2}

concentration than Fig. 10(a) due to the higher

{CO}_{2}

mass flow rate over a similar injection time. It will be shown that the

{CO}_{2}

flow rate was excessive, and the water flow rate was insufficient for this manifold configuration.

Fig. 11 depicts the

{CO}_{2}

concentrations generated by the wall manifold combination A-C-E-G operating at

12,110 L / \min

(

3,200 gal. / \min

) and

{CO}_{2}

flow rates of (1)

18.9 kg / \min

(

2,500 lb / h

); and (2)

26.5 kg / \min

(3,

500 lb / h

). The wall manifolds were more evenly distributed across the lock rather than being concentrated on the upstream (west) half as in Figs. 9 and 10, resulting in more uniform

{CO}_{2}

concentrations throughout the tests. However, Fig. 11(b) shows a substantial decrease in

{CO}_{2}

concentration on the upstream (west) end of the lock (L1B) after the injection ended. This was likely caused by the leakage through the upstream miter gate and could allow fish to become trapped near the upstream (west) gate by higher

{CO}_{2}

concentrations downstream, an undesirable outcome for nuisance fish control.

In general, the mixing from the floor manifolds (Fig. 8) produced sharp discontinuities in concentration as the tethered boats traversed the lock, representing nonhomogeneity laterally across the lock (north to south). Meanwhile, the wall manifolds (Figs. 9–11) showed decreasing

{CO}_{2}

concentration from upstream (west) to downstream (east), indicating the generation of a

{CO}_{2}

concentration gradient that would drive invasive fish downstream, preventing upstream migration.

The wall manifolds’ performance depended on the number and distribution of operating manifolds as well as the

{CO}_{2}

mass flow rate. Two-wall manifolds (Fig. 9) produced the greatest disparity in

{CO}_{2}

concentrations (e.g., strong flushing fields) early in the test but were prone to localized

{CO}_{2}

concentrations that exceeded WDNR regulatory limits (

> 150 mg / L

), thus foreshortening

{CO}_{2}

injection times and dissolved

{CO}_{2}

masses. Three-wall manifolds (Fig. 10) produced good flushing fields at the start of tests and nearly uniform

{CO}_{2}

concentrations at the end of tests. Concentrated wall manifolds (Figs. 9 and 10) produced stronger flushing fields than four distributed manifolds (Fig. 11). However, distributed manifolds (Fig. 11) were less likely to produce localized

{CO}_{2}

concentrations that may exceed WDNR regulatory limits (

> 150 mg / L

), thus allowing longer injection times and greater dissolved

{CO}_{2}

masses.

Treatment time and fish exposure periods are important considerations relative to fish biology and effective fish control treatments. Commercial shipping endeavors to minimize locking time but longer treatment duration ensure that localized

{CO}_{2}

concentrations can be distributed in the lock to more uniform levels. Additionally, fish must encounter the

{CO}_{2}

plume for a certain length of time to make favorable cognitive and behavioral responses. It is likely that prolonged injection times across larger treatment volumes would result in a more effective outcome. Regardless, the testing showed that floor manifolds and several (3–4) wall manifolds can effectively reach target concentrations and could be used to conduct lock treatments.

Performance at 15 Minutes

The previously described

{CO}_{2}

concentration versus time plots (Figs. 8–11) show the variation of dissolved

{CO}_{2}

for the duration of the trials. Details of the comparative performance of the manifolds at a specific time (e.g., 15 min) can be obtained by interpolation of the data from the 10 sondes at each position [south (S), center (C), and north (N)]. Fig. 12 shows the four-wall manifolds A-B-C-D operating at

c = 12,110 L / \min

(

3,200 gal. / \min

) and

{\dot{m}}_{CO 2} = 18.9 kg / \min

(

2,500 lb / h

). The data for the center of the lock are taken as the mean of five measurements at time 14:30 to 14:50 min. The data for the north wall of the lock are taken as the mean of five measurements at time 15:10 to 15:30 min. The data for the south wall of the lock use interpolation between five measurements at times 11:30 to 11:50 and five measurements at 21:10 to 21:30 min.

Data from each of the tests were used to generate

{CO}_{2}

concentration arrays corresponding to each of the sonde locations shown in Fig. 5 for the upper (top) and lower (bottom) sondes on each boat. The data were imported into MATLAB version 9.10 R2021a, and a grid was generated with 40 subdivisions in the

x - direction

(west–east),

y - direction

(south–north), and

z - direction

(bottom–top). Linear interpolation was used to assign values to grid points from the measured data points (sondes).

Fig. 13 shows the interpolated dissolved

{CO}_{2}

field from Fig. 12 as contour plots divided into arrays of lower sondes (bottom) to focus on the performance concerns discussed earlier. The field is contained within the rectangular chamber created by the pH sensors as depicted in Fig. 5. The positions of the connecting pipes to the active wall manifolds (A-B-C-D) are depicted by black circles in the upper region of relevant figures. The figures graphically and numerically illustrate the expected

{CO}_{2}

concentration gradient from the upstream (west) to downstream (southeast) portions of the chamber. Based on fish response to

{CO}_{2}

in previous studies, such a gradient is expected to drive fish from the lock through the downstream (east) gates and out of the lock.

Fig. 13. Dissolved ${CO}_{2}$ concentrations at the lower (bottom) sonde arrays at $t = 15 \min$ for the wall manifold A-B-C-D at ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ). Black circles denote open wall manifold valves.

Fig. 14 shows the dissolved

{CO}_{2}

concentrations at time = 15 min for the floor manifolds depicted in Fig. 8. Each figure shows the bottom sensor arrays corresponding to trials F 3000–2500 [Fig. 14(a)] and F 3000–3500 [Fig. 14(b)]. In general, all trials show a decreasing concentration gradient from north to south. This is attributable to the south-to-north flow field generated by the pump intake in the northwest corner. The lower

{CO}_{2}

concentrations at the upstream end of the lock in the southeast corner (lower left) are believed to be caused by leaks in the upstream miter gates combined with the water circulation pattern induced by south branch pipe position and the pump intake. Aside from minimizing leakage, this lateral asymmetry may be able to be somewhat alleviated by placing the manifold branches closer to the lock walls and placing the pump intake centrally within the chamber.

Fig. 14. Dissolved ${CO}_{2}$ concentrations at the lower (bottom) sonde arrays at $t = 15 \min$ for the floor manifold at: (a) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 11,360 L / \min$ ( $3,000 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 15 shows the dissolved

{CO}_{2}

concentrations at the lower sondes at time = 15 min for the wall manifolds A-B depicted in Fig. 9 under the test names W A-B 2800-2500 [Fig. 15(a)] and W A-B 2800-3500 [Fig. 15(b)]. In general, all trials showed a decreasing concentration gradient from upstream to downstream (west to east). This was caused by the activation of the wall manifolds only on the upstream (west) section of the lock as shown by the black circles. Although the position of the manifolds generated the desired deterrence field gradient, it also caused

{CO}_{2}

spikes (Fig. 9) that foreshortened the injection time and thereby reduced the available

{CO}_{2}

for dissolution. Similar conditions occurred for the W A-B-C manifolds (Fig. 10) where an early spike in

{CO}_{2}

caused shorten injection times and less overall

{CO}_{2}

injection. Thus, the

{CO}_{2}

concentrations attained by two-wall and three-wall manifolds were not able to meet the

{CO}_{2}

concentration requirements due to the short injection times to meet WDNR limits on dissolved

{CO}_{2}

(

< 150 mg / L

).

Fig. 15. Dissolved ${CO}_{2}$ concentrations at the lower (bottom) sonde arrays at 15 min for the wall manifolds A-B at: (a) ${\dot{V}}_{H 2 O} = 10,600 L / \min$ ( $2,800 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 10,600 L / \min$ ( $2,800 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

Fig. 16 shows the dissolved

{CO}_{2}

concentrations at the lower sondes at time = 15 min for the distributed wall manifolds A-C-E-G depicted in Fig. 11. Each figure shows the bottom sensor arrays corresponding to trials (1) W A-C-E-G 3200-2500; and (2) W A-C-E-G 3200-3500. The uniform distribution of manifolds, shown by the black circles, gives a uniform

{CO}_{2}

distribution that nearly attained target concentrations in both cases. Additionally, the absence of high

{CO}_{2}

regions allowed

{CO}_{2}

injection to continue for 10–12 min and approach the desired concentration. These trials also exhibit a more subtle form of the upstream–downstream (west–east) concentration gradient that was sought in the W A-B, W A-B-C, and W A-B-C-D trials.

Fig. 16. Dissolved ${CO}_{2}$ concentrations at the lower (bottom) sonde arrays at 15 min for the wall manifolds A-C-E-G at: (a) ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 18.9 kg / \min$ ( $2,500 lb / h$ ); and (b) ${\dot{V}}_{H 2 O} = 12,110 L / \min$ ( $3,200 gal. / \min$ ) and ${\dot{m}}_{CO 2} = 26.5 kg / \min$ ( $3,500 lb / h$ ).

In general, the floor manifolds and the combinations of four-wall manifolds (W A-B-C-D and W A-C-E-G) most nearly approached the target

{CO}_{2}

concentrations and generated rather uniform fields. This is due to the greater distribution of water injection points and the need to carry less

{CO}_{2}

per unit volume of water. Meanwhile, the high momentum flux of combinations of two-wall and three-wall manifolds (W A-B and W A-B-C) produced good mixing and strong upstream-to-downstream (west-to-east)

{CO}_{2}

gradients, but the resulting high

{CO}_{2}

concentration quickly approached the WDNR limits (

150 mg / L

) and foreshortened the injection times, thereby reducing the total volume of water treated. These results indicate that multiple concentrated manifolds can meet performance requirements for unidirectional lockages, whereas distributed manifolds are better suited for bidirectional lockages.

Manifold Performance: Concentration and Injection Efficiency

The injection efficiency is a composite of the PSF’s ability to infuse

{CO}_{2}

into water (gas–liquid mixing) and the manifolds’ ability to distribute the treated water uniformly through the lock chamber. Previous research in a concrete test pond at USGS Upper Midwest Environmental Sciences Center allowed the authors to study floor and wall manifolds under highly controlled conditions of injection times (

Δ t = 40 \min

), flow rates, and treatment volume (Zolper et al. 2019). This ensured that accurate calculations of injection efficiency were feasible. The present studies, representative of actual field installations subject to regulatory conditions, pose greater challenges to consistent calculations of injection efficiency due to greater variation in injection times (

3 : 01 < Δ t < 13 : 37

). These challenges are further compounded by the effect of water flow rate on mixing homogeneity and off-gassing rates.

In an effort to reconcile the challenges presented previously with the need to quantify the performance of each manifold configuration, the authors took an approach similar to previous work (Zolper et al. 2019) with slight modifications. The mass of

{CO}_{2}

dissolved in the lock water at 15 min after

{CO}_{2}

injection began was approximated by the product of the average

{CO}_{2}

concentration

C_{CO 2}

in the water and the water volume of the lock (

V_{H 2 O} = 1,459, 700 \pm 18,000 L

), as shown in Eq. (3). The average

{CO}_{2}

concentration

C_{CO 2}

at 15 min was obtained from the sum of individual concentrations

C_{CO 2 i}

, divided by the total number of sensors (30) shown in Eq. (3). Thus, average concentration used the same 30 data points that were interpolated to generate the

{CO}_{2}

concentration fields in Figs. 13–16

m_{CO 2}^{D} = C_{CO 2} \cdot V_{H 20} = \frac{\sum_{i = 1}^{30} C_{CO 2 i}}{30} \cdot V_{H 20}

(3)

Table 2 lists the average

{CO}_{2}

concentration at 15 min and the calculated dissolved

{CO}_{2}

mass for each of the tests listed in Table 1, using the naming convention introduced after Table 1. It also lists the standard deviation of the

{CO}_{2}

concentration

C_{CO 2}

at 15 min, an indicator of mixing homogeneity, as well as the resulting uncertainty in dissolved mass. Only four experimental trials reached the target mean concentration of

100 mg / L

due to the requirement that tests be terminated when any sensor reached a

{CO}_{2}

concentration of

150 mg / L

. Nonetheless, the relative magnitude of the standard deviation with respect to concentration is an indicator of mixing homogeneity and the magnitude of any concentration gradients that formed in the chamber. For example, the minimum number of wall manifolds (W A-B) had relatively high standard deviations, whereas the maximum distributed wall manifolds (W A-C-E-G) had relatively small standard deviations due to the more uniform concentrations they produced.

Table 2. Average

{CO}_{2}

concentration at 15 min, standard deviation, and total dissolved

{CO}_{2}

mass with corresponding uncertainties

Test name ( $gal. / \min - lb / h$ )	Avg. ${CO}_{2}$ concentration ( $mg / L$ )	Standard deviation ( $mg / L$ )	Dissolved ${CO}_{2}$ mass (lb)	Dissolved ${CO}_{2}$ mass (kg)
F 2200-2500	118.2	54.1	$382.1 \pm 178.9$	$173.3 \pm 81.2$
F 2200-3500	58.5	34.3	$189.0 \pm 113.3$	$85.8 \pm 51.4$
F 3000-2500	71.2	31.6	$230.1 \pm 104.6$	$104.4 \pm 47.5$
F 3000-3500	120.2	43.0	$388.4 \pm 142.4$	$176.2 \pm 64.6$
W A-B 1800-2500	63.4	35.5	$204.9 \pm 117.5$	$92.9 \pm 53.3$
W A-B 1800-3500	32.1	15.2	$103.7 \pm 50.3$	$47.1 \pm 22.8$
W A-B 2800-2500	35.1	12.9	$113.4 \pm 42.8$	$51.5 \pm 19.4$
W A-B 2800-3500	35.3	15.0	$114.1 \pm 49.5$	$51.7 \pm 22.4$
W A-B-C 2200-2500	43.6	19.8	$140.9 \pm 65.4$	$63.9 \pm 29.6$
W A-B-C 2200-3500	52.3	23.6	$169.0 \pm 78.1$	$76.7 \pm 35.4$
W A-B-C 3000-2500	69.0	18.6	$223.0 \pm 61.6$	$101.1 \pm 28.0$
W A-B-C 3000-3500	76.5	28.4	$247.2 \pm 94.0$	$112.1 \pm 42.6$
W A-B-C-D 3200-2500	76.7	23.3	$247.9 \pm 77.2$	$112.4 \pm 35.0$
W A-B-C-D 3200-3500	Cancelled due to weather
W A-C-E-G 3200-2500	106.2	31.1	$343.2 \pm 103.0$	$155.7 \pm 46.7$
W A-C-E-G 3200-3500	118.3	26.9	$382.3 \pm 89.1$	$173.4 \pm 40.4$

Note: The mass of ${CO}_{2}$ injected was dependent on measured concentrations within the lock chamber to not exceed $150 mg / L {CO}_{2}$ at any location.

The mass of

{CO}_{2}

injected into the lock through the PSF was calculated as the product of the

{CO}_{2}

mass flow rate and the injection time, as shown in Eq. (4). The

{CO}_{2}

mass flow rate was measured at 60-s intervals and remained stable for the duration of the injection period, leading to relatively low uncertainty values. Injection time was limited by the WDNR criteria that the

{CO}_{2}

concentration must not exceed

150 mg / L

m_{CO 2}^{I} = {\dot{m}}_{CO 2} \cdot t_{inj}

(4)

The carbon dioxide injection efficiency

ε

was calculated from the quotient of the masses of

{CO}_{2}

dissolved in the water (

m_{CO 2}^{D}

) and

{CO}_{2}

injected through the PSF (

m_{CO 2}^{I}

), as shown in Eq. (5). The carbon dioxide injection efficiency serves as an indicator of the expected operational costs of each injection manifold. This method gives the composite performance of the PSF, injection manifolds, and off-gassing rates in addition to the limits imposed on

{CO}_{2}

injection time by WDNR

{CO}_{2}

limits. This is representative of operational and regulatory constraints of an actual installation

ε = \frac{m_{CO 2}^{D}}{m_{CO 2}^{I}} = \frac{C_{CO 2} \cdot V_{H 20}}{{\dot{m}}_{CO 2} \cdot t_{inj}}

(5)

Table 3 lists the injection times, total injected masses of

{CO}_{2}

, and calculated injection efficiencies corresponding to each of the trials in Table 2. The

{CO}_{2}

flowmeter was an accurate instrument, so the uncertainty was most affected by injection time. The efficiency represents the effects of many factors, including the level of

{CO}_{2}

saturation of water, turbulence of the water, injection time, operating pressure, Reynolds number, and manifold type (W or F) and combination (A-B, A-B-C, etc.). Most of the uncertainty in injection efficiency was propagated through dissolved

{CO}_{2}

mass from the standard deviation listed in Table 2.

Table 3. Injection times, total masses of

{CO}_{2}

injected, and injection efficiencies with corresponding uncertainties

Test name (gal./min-lb/h)	Injection time (m:s)	Injection time (s)	Injected ${CO}_{2}$ mass	Injected ${CO}_{2}$ mass	Injection efficiency
Test name (gal./min-lb/h)	( $\pm 1 s$ )	( $\pm 1 s$ )	(lb)	(kg)	(%)
F 2200-2500	13:37	817	$588 \pm 23$	$267 \pm 10$	$65 \pm 31$
F 2200-3500	06:13	373	$372 \pm 10$	$169 \pm 5$	$51 \pm 30$
F 3000-2500	09:36	576	$409 \pm 16$	$185 \pm 7$	$56 \pm 26$
F 3000-3500	11:41	701	$698 \pm 19$	$317 \pm 9$	$56 \pm 20$
W A-B 1800-2500	06:55	415	$296 \pm 12$	$134 \pm 5$	$69 \pm 40$
W A-B 1800-3500	03:01	181	$183 \pm 5$	$83 \pm 2$	$57 \pm 28$
W A-B 2800-2500	04:33	273	$193 \pm 8$	$88 \pm 3$	$59 \pm 22$
W A-B 2800-3500	03:01	181	$182 \pm 5$	$83 \pm 2$	$63 \pm 27$
W A-B-C 2200-2500	05:26	326	$235 \pm 9$	$107 \pm 4$	$60 \pm 28$
W A-B-C 2200-3500	04:22	266	$257 \pm 7$	$117 \pm 3$	$66 \pm 30$
W A-B-C 3000-2500	06:31	391	$278 \pm 11$	$126 \pm 5$	$80 \pm 22$
W A-B-C 3000-3500	06:25	385	$380 \pm 11$	$172 \pm 5$	$65 \pm 25$
W A-B-C-D 3200-2500	08:28	508	$361 \pm 14$	$164 \pm 6$	$69 \pm 22$
W A-B-C-D 3200-3500	Cancelled due to weather
W A-C-E-G 3200-2500	12:02	722	$508 \pm 20$	$231 \pm 9$	$68 \pm 20$
W A-C-E-G 3200-3500	10:33	633	$617 \pm 18$	$280 \pm 8$	$62 \pm 15$

Note: Injection times were based on any single location within the lock chamber reaching the upper threshold of $150 mg / L {CO}_{2}$ .

Design of Experiments: Injection Efficiency

Injection efficiency heavily depends on both

{CO}_{2}

mass flow rate and water volume flow rate. If the

{CO}_{2}

mass flow rate is too high for the water flow rate, there is substantial off-gassing when it is ejected from the manifolds. If

{CO}_{2}

mass flow rate is too low for the water flow rate, the carrier water does not maximize its carrying potential. The design of experiments outlined in Table 1 was used to assess the optimum operating parameters of

{CO}_{2}

mass flow rate and water volume flow rate. Efficiency optimization was addressed using four DOE trials for each of three manifold combinations: floor (F), wall manifolds A-B (W A-B), and wall manifolds A-B-C (W A-B-C). The resulting efficiencies at 15 min (Table 3) were subject to regression analysis using Minitab 18. Fig. 17 shows the optimum water and

{CO}_{2}

flow rates to maximize efficiency of three concentrated manifolds (W A-B-C) under the present constraints. The axes are labeled according to the convention established in Table 1. Fig. 17 shows that the

{CO}_{2}

flow rate was too high to maximize efficiency. In fact, there was visible off-gassing from the lock for some of the high

{CO}_{2}

flow rate trials. Fig. 17 also shows that configuration could accommodate even greater water flow rates.

Fig. 17. Optimum operating conditions to maximize injection efficiency at $t = 15 \min$ for three concentrated wall manifolds (W A-B-C).

For a given manifold configuration, high water flow rates result in higher turbulence and operating pressure. High turbulence generally helps entrain and dissolve gaseous

{CO}_{2}

, resulting in high injection efficiency (Gebhart 1993; Rolle 2016). Furthermore, the mass diffusivity for

{CO}_{2}

into water near the experiment temperature (

δ = 0.2 \times 10^{- 8} m^{2} / s

) and the target concentration (

100 mg / L

) renders high injection efficiency feasible (Rolle 2016). Although high operating pressure raises the amount of

{CO}_{2}

that can be dissolved into the water, when the pressure decreases after exiting the manifolds, the dissolved gases can come out of solution. These results can be used to further improve the design configurations and operating conditions of

{CO}_{2}

injection manifolds (e.g., floor versus wall) and related technologies (Shane 1996).

Operating Power and Costs

Operating power is an influential factor when selecting a large-scale

{CO}_{2} - to - water

injection system. Water flow rate

{\dot{V}}_{H 2 O}

, operating pressure

P_{oper}

, and pump efficiency all contribute to the operating costs of equipment. The operating power

{\dot{W}}_{oper}

of the pump-manifold system was calculated as the product of the operating pressure [Eq. (1)] and the water flow rate

{\dot{V}}_{H 2 O}

, as shown in Eq. (6)

{\dot{W}}_{oper} = {\dot{V}}_{H 2 O} \cdot P_{oper}

(6)

Table 4 provides the water volume flow rates, operating pressures, calculated operating power, and associated uncertainties for each of the manifold systems in this study. For each manifold system, the operating pressure increased with water volume flow rate. The compound effect can double the operating power, such as in the case of the trials of manifolds W A-B 1800-3500 in comparison to W A-B 2800-3500. Among the following systems, the two-wall manifold (W A-B) had the highest operating pressure for a given flow rate. Meanwhile, the floor (F) and three-wall manifolds (W A-B-C) had similar operating pressures and power at low flow rates, but the floor manifold operating power increased more substantially at higher flow rates. To treat larger volumes and keep operating power low, better results were obtained using a greater number of manifolds operating at low pressure than using a few manifolds operating at high pressure.

Table 4. Water flow rate, operating pressure, and operating power of manifolds

Test name ( $gal . / \min - lb / h$ )	Volume flow rate		Operating pressure		Operating power
Test name ( $gal . / \min - lb / h$ )	( $\pm 0.00126 m^{3} / s$ )	( $\pm 20 GPM$ )	( $\pm 6.9 kPa$ )	( $\pm 1 psi$ )	(kW)
F 2200-2500	0.140	2,218	337.8	49.0	$47.3 \pm 1.1$
F 2200-3500	0.140	2,224	379.2	55.0	$53.2 \pm 1.1$
F 3000-2500	0.184	2,924	668.8	97.0	$123.4 \pm 1.5$
F 3000-3500	0.189	2,992	675.7	98.0	$127.6 \pm 1.6$
W A-B 1800-2500	0.115	1,828	379.2	55.0	$43.7 \pm 0.9$
W A-B 1800-3500	0.116	1,845	386.1	56.0	$45.0 \pm 0.9$
W A-B 2800-2500	0.172	2,723	772.2	112.0	$132.7 \pm 1.5$
W A-B 2800-3500	0.175	2,770	779.1	113.0	$136.1 \pm 1.6$
W A-B-C 2200-2500	0.150	2,375	365.4	53.0	$54.7 \pm 1.1$
W A-B-C 2200-3500	0.147	2,322	358.5	52.0	$52.5 \pm 1.1$
W A-B-C 3000-2500	0.190	3,014	503.3	73.0	$95.7 \pm 1.5$
W A-B-C 3000-3500	0.191	3,021	537.8	78.0	$102.5 \pm 1.5$
W A-B-C-D 3200-2500	0.200	3,169	441.3	64.0	$88.5 \pm 1.5$
W A-B-C-D 3200-3500	Cancelled due to weather
W A-C-E-G 3200-2500	0.196	3,106	406.8	59.0	$79.7 \pm 1.4$
W A-C-E-G 3200-3500	0.198	3,135	427.5	62.0	$84.6 \pm 1.5$

Operating costs for the present manifold systems are a function of operating power

{\dot{W}}_{oper}

and the processes needed to obtain and infuse the

{CO}_{2}

to the required specifications. Under steady-state conditions, the energy needed to operate the pump

E_{oper}

was the product of the operating power and pump operating time, as shown in Eq. (7). The pump operating time was about 40 min (0.67 h) for each test. An estimated pump efficiency

ε_{pump} = 80 %

was selected as representative of a typical pump. The energy required to operate the

{TOMCO}_{2}

PSF was negligible because the ambient temperatures in August–September 2019 were ample to vaporize the liquid

{CO}_{2}

in the storage tank and provide the necessary

{CO}_{2}

flow rates

E_{oper} = \frac{{\dot{W}}_{oper} \cdot t_{pump}}{0.80}

(7)

Table 5 lists the pump energy, pump operating costs, and material (injected

{CO}_{2}

) costs using the data from Tables 3 and 4. The pump used diesel fuel, but these calculations project the case of an electric pump located at a permanent installation of similar size. The industrial electrical rates in Kaukauna, Wisconsin, were about

$ 0.10 / kWh

at the time of the experiments. The cost of

{CO}_{2}

delivered to Kaukauna, Wisconsin, was

$ 0.24 / kg

(

$ 0.11 / lb

).

Table 5. Pump energy, electricity costs,

{CO}_{2}

costs, and total costs for each trial in Kaukauna, Wisconsin

Test name ( $gal. / \min - lb / h$ )	$t = 40 \min$	Electricity costs ($)	${CO}_{2}$ costs ($)	Total cost ($)
Test name ( $gal. / \min - lb / h$ )	Pump energy (kWh)	$$ 0.10 / kWh$	$$ 0.24 / kg$ $$ 0.11 / lb$	Total cost ($)
F 2200-2500	39.4	3.94	64.66	68.60
F 2200-3500	44.3	4.43	40.92	45.36
F 3000-2500	102.8	10.28	44.94	55.22
F 3000-3500	106.3	10.63	76.78	87.40
W A-B 1800-2500	36.4	3.64	32.52	36.16
W A-B 1800-3500	37.5	3.75	20.13	23.88
W A-B 2800-2500	110.6	11.06	21.26	32.31
W A-B 2800-3500	113.5	11.35	20.01	31.36
W A-B-C 2200-2500	45.6	4.56	25.89	30.45
W A-B-C 2200-3500	43.8	4.38	28.29	32.67
W A-B-C 3000-2500	79.8	7.98	30.60	38.58
W A-B-C 3000-3500	85.4	8.54	41.82	50.36
W A-B-C-D 3200-2500	73.5	7.35	39.73	47.08
W A-B-C-D 3200-3500	Cancelled due to weather
W A-C-E-G 3200-2500	66.4	6.64	55.92	62.57
W A-C-E-G 3200-3500	70.5	7.05	67.88	74.92

Operating pressure and the resulting operating power clearly affect the electricity cost for each configuration of manifolds. However, the greater cost driver was the

{CO}_{2}

consumption required to treat the lock. This highlights the benefit of setting the water and

{CO}_{2}

flow rates at levels that optimize the injection efficiency and minimize off-gassing, as shown in Fig. 17. Ultimately, the combination of operating conditions and manifold configurations that meets the injection requirements (

100 mg / L < C_{CO 2} < 150 mg / L

), keeps the costs as low as possible, and provides the best performance are F3000-3500, W A-B-C-D 3200-2500, and W A-C-E-G 3200-2500. For larger lock installations, the wall manifolds can be treated as modular devices to be used at the operating pressures listed in Table 3. If the proposed installation is 10 times larger, then 10 times as many wall manifolds (on both walls) can be used, and 10 times as much

{CO}_{2}

would be required. Thus, the projected operating costs for such a lock would be approximately 10 times the costs listed in Table 5.

Conclusion

This research assessed the performance of floor-based and wall-based

{CO}_{2} - infused

water-to-water injection manifolds, using DOE to arrange a series of tests that can be used to optimize performance. Sixteen distinct trials were planned (15 were completed) with high and low flow rates applied to five different manifold configurations. The water acidity was measured and used to calculate

{CO}_{2}

concentration as a function of time and the shape of the dissolved

{CO}_{2}

fields within the sensor chamber. Additional measurements of operating pressure, injection time, and water and

{CO}_{2}

flow rate were used to calculate injected

{CO}_{2}

mass, dissolved

{CO}_{2}

mass, injection efficiency, and operating power.

The following test parameters are considerations based on the feasibility of floor, concentrated wall, and distributed wall manifolds for a given application:

1.

Floor Manifolds: The operating parameters for trial F 3000-3500 nearly attained the desired performance in terms of mixing homogeneity. However, the floor manifolds did not fully treat one wall of the lock. Future designs would benefit from having adequate fluid dynamic models, physical testing, and proper distribution configurations that ensure adequate mixing and uniform distribution. The floor manifolds had a relatively uniform upstream–downstream

{CO}_{2}

concentration gradient at 15 min. Future designs would benefit from having the pump intake moved to the downstream end of the lock to increase the generation of a downstream flushing field.

2.

Concentrated Wall Manifolds (W A-B, W A-B-C, and W A-B-C-D): The operating parameters for trial W A-B-C-D 3200-2500 nearly attained the desired performance in terms of mixing homogeneity, minimal

{CO}_{2}

spike, and operating power. Fewer manifolds may cause a brief

{CO}_{2}

spike that is localized in certain areas and potentially shorten injection time to avoid hot spots that exceed target concentration thresholds. This may also be improved by moving the water pump intake to the downstream end of the lock. The concentrated manifolds also generate a directional

{CO}_{2}

gradient that may drive fish through the downstream gate.

3.

Distributed Wall Manifolds (W A-C-E-G): The operating parameters for trial W A-C-E-G 3200-2500 attained the desired performance in field uniformity, injection efficiency, and power requirements. They did not cause an intermittent

{CO}_{2}

spike and were able to operate for much longer than many of the upstream concentrated wall manifolds. They also operated at a relatively low pressure despite the high flow rates, resulting in lower operating power. Their general distribution also makes them adaptable for preventing upstream and downstream migration of aquatic invasive species if the need arises, but the influence of a horizontal flow field on vessel navigation would warrant investigation.

Notation

The following symbols are used in this paper:

$C_{CO 2}$: carbon dioxide concentration;
$C_{target}$: target carbon dioxide concentration;
$d_{CO 2}$: diameter of carbon dioxide line;
$d_{H 2 O}$: diameter of floor or wall manifold nozzles;
$E_{oper}$: total energy to operate pump for test;
$g$: gravitational constant;
$m_{CO 2}^{D}$: dissolved carbon dioxide in lock;
$m_{CO 2}^{I}$: injected carbon dioxide into lock;
${\dot{m}}_{CO 2}$: mass flow rate of carbon dioxide;
$P_{in}$: pump inlet pressure;
$P_{oper}$: system operating pressure;
$P_{out}$: manifold outlet pressure;
$pH$: acidity of water at any sonde;
$T$: lock water temperature;
$t_{inj}$: duration of carbon dioxide injection;
$t_{mix}$: time to attain certain carbon dioxide concentration;
$t_{pump}$: duration of pump operation;
$t_{0}$: start of carbon dioxide injection;
${\dot{V}}_{CO 2}$ , $V_{CO 2}$: volume flow rate and velocity of carbon dioxide;
${\dot{V}}_{H 2 O}$ , $V_{H 2 O}$: volume flow rate and velocity of water;
$V_{enc}$: volume of water in lock chamber;
${\dot{W}}_{oper}$: power to operate pump;
$Δ t$: total carbon dioxide injection time;
$δ_{CO 2}$: diffusivity of carbon dioxide into water;
$ε_{inj}$: carbon dioxide injection efficiency;
$ε_{pump}$: pump operating efficiency;
$μ_{H 2 O}$: viscosity of water;
$ρ_{CO 2}$: density of carbon dioxide;
$ρ_{H 2 O}$: density of water; and
$ω$: angular velocity of pump.

Appendix. Acidity and Carbon Dioxide Measurements

Measurements of pH and dissolved

{CO}_{2}

were simultaneously made on several Fox River water samples at the start (July 26, 2019) and end (September 5, 2019) of the experiments. A HACH HQ40d sensor with a PHC20101 probe (HACH, Loveland, Colorado) was used to measure the acidity (pH) of water samples with an accuracy of

\pm 0.02

pH (Cupp et al. 2017b), shown by horizontal error bars (Fig. 18). A HACH 16900 digital titrator was used to measure the corresponding

{CO}_{2}

concentration (

mg / L

) with an accuracy of

\pm 1 %

of reading (Cupp et al. 2017b), shown by vertical error bars (Fig. 18) using HACH Method 8205 according to the Standard Methods for Examination of Water and Wastewater (Baird 2017). The upper and lower instrument uncertainty bounds are represented by dashed lines.

Fig. 18. Calibration curves (solid lines) and associated error ranges (dashed lines) relating measurements of acidity (pH) to ${CO}_{2}$ concentration of Fox River water on: (a) July 26, 2019; and (b) September 5, 2019.

The exponential equations of best fit at both dates matched quite well, so the mean values of the coefficients (336,140,000) and exponents (2.323) were used to calculate dissolved

{CO}_{2}

concentration

C_{CO 2}

from pH measurements as shown in Eq. (2). The temperature of the lock water varied between 19.5°C and 26.7°C (67.1°F and 80.1°F) over the course of the study. The authors investigated whether Eq. (2) required temperature compensation and found it had negligible effects on the uncertainty in

{CO}_{2} - pH

correlations (Zolper et al. 2019).

Data Availability Statement

All data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgments

This project was funded with a US Geological Survey Cooperative Agreement (G16AC00043) between the USGS Upper Midwest Environmental Sciences Center and the University of Wisconsin-Platteville. The authors thank personnel from the US Geological Survey, US Army Corps of Engineers, US Fish and Wildlife Service, Wisconsin Department of Natural Resources, University of Illinois, and University of Wisconsin-Platteville for their feedback and advice throughout this project. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US government.

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Information & Authors

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Published In

Journal of Environmental Engineering

Volume 148 • Issue 4 • April 2022

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This work is made available under the terms of the Creative Commons Attribution 4.0 International license, https://creativecommons.org/licenses/by/4.0/.

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Received: May 24, 2021

Accepted: Dec 13, 2021

Published online: Feb 10, 2022

Published in print: Apr 1, 2022

Discussion open until: Jul 10, 2022

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Thomas J. Zolper [email protected]

Associate Professor, Dept. of Mechanical Engineering, Univ. of Wisconsin-Platteville, 1 University Plaza, Platteville, WI 53818 (corresponding author). Email: [email protected]

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David L. Smith

Research Ecologist, US Army Corps of Engineers, Engineer Research and Development Center, 3909 Halls Ferry Rd., Vicksburg, MS 39180.

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P. Ryan Jackson https://orcid.org/0000-0002-3154-6108

Hydrologist, US Geological Survey, Central Midwest Water Science Center, 405 N. Goodwin Ave., Urbana, IL 61801. ORCID: https://orcid.org/0000-0002-3154-6108

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Aaron R. Cupp

Research Fish Biologist, US Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Rd., La Crosse, WI 54603.

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Performance of a Carbon Dioxide Injection System at a Navigation Lock to Control the Spread of Aquatic Invasive Species

Abstract

Introduction

Experimental Setup and Methods

Design of Experiments—Test Plan

General Experimental Procedures

Results and Discussion

Acidity and ${CO}_{2}$ Content

Floor Manifold: Concentration versus Time

Wall Manifolds: Concentration versus Time

Performance at 15 Minutes

Manifold Performance: Concentration and Injection Efficiency

Design of Experiments: Injection Efficiency

Operating Power and Costs

Conclusion

Notation

Appendix. Acidity and Carbon Dioxide Measurements

Data Availability Statement

Acknowledgments

References

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Abstract

Introduction

Experimental Setup and Methods

Design of Experiments—Test Plan

General Experimental Procedures

Results and Discussion

Acidity and CO2 Content

Floor Manifold: Concentration versus Time

Wall Manifolds: Concentration versus Time

Performance at 15 Minutes

Manifold Performance: Concentration and Injection Efficiency

Design of Experiments: Injection Efficiency

Operating Power and Costs

Conclusion

Notation

Appendix. Acidity and Carbon Dioxide Measurements

Data Availability Statement

Acknowledgments

References

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Acidity and ${CO}_{2}$ Content