Background

This monitoring plan is for the implementation of nanobubble equipment submitted to the Wisconsin Department of Natural Resources (DNR) for review under s. NR 109.09 (2) (a), (d), (e), (h), and (I) and s. NR 150.30 (3). Some components of the plan are waived due to the existing aquatic plant management mechanical harvesting plan last approved by the Department in 2022.

Goals and Objectives

The goal of the proposed management is to reduce nutrients and subsequent algal blooms in the littoral zone on Camelot Lake, Sherwood Lake, and Arrowhead Lake.

Literature Review

Nanobubble (NB) technology is a burgeoning field for water treatment, especially in natural environments, and thus there is limited peer reviewed research available (Jia, et al 2023). While the development of NB technology is still in the exploration stage, several review articles have documented the fundamental properties of NBs and their role in water treatment processes. Most of these articles have focused on the role of NBs in specific treatment processes, such as flotation (Kyzas et al., 2021), and anaerobic digestion (Chuenchart et al., 2021), or covered the applications of NBs in general water treatment processes (Atkinson et al., 2019) at a laboratory or bench scale.

There are case studies on the use of NB in aquacultural, industrial water treatment, and lakes spanning different scales, which are presented by NB practitioners. A summary of those projects is provided by Moleaer in Appendix A.

For Tri Lakes in particular, NB may be advantageous to provide sustained aeration of the sediments. From recent studies, NBs with a diameter <200 nm were promising in improving gaseous mass-transfer and associated bioprocessing (Patel, et al, 2021). In 2023 a small-scale short-term study was implemented in Arrowhead Lake which demonstrated increased oxygen saturation with the treatment area during the treatment.

Alternative Methods of Control

An alum treatment was completed on Sherwood Lake during the summer of 2023, Figure 1. The alum treatment was used to strip the water column of nutrients and other constituents, like algae. This alum treatment showed improvement in in-lake total phosphorus concentrations, Figure 2. It is also important to note that there were low flow conditions throughout the summer which also attributed to low inflow phosphorus load and low in lake phosphorus concentrations. Replication of this alum treatment will only remove the constituents in the water column at the time of application. It is not providing continuous treatment of constituents in the water column.

Figure 1: 2023 Alum treatment coverage map.

Figure 2: TP monitored at the outlet of Sherwood Lake.

Proposed Management

Nanobubble generators are proposed to treat 10% of the littoral zone in Sherwood Lake, Camelot Lake, and Arrowhead Lake, details included in Figures 3-5. The nanobubble (NB) generators are quoted to treat 1-2 acres per horsepower of the motor using aeration sizing conventions for diffusive pond aeration (Tucker, 2005). The NEO units, red and green dots, have less than 1 hp motors. In figures 3-5, the teal color represents 1 acre of treatment, and the dark blue color represents the extension to 2 acres of treatment. The container unit, yellow dot, has a 20 hp motor. The specifications for each unit are included in Appendix B. Exact installation specifics are forthcoming. Additionally, we are proposing to install five monitoring buoys in the Tri Lakes for continuous monitoring. Each of the buoy sites is the location of pre-treatment sediment cores.

On Camelot Lake (Figure 3), we are proposing ten NEO units with an anticipated treatment of 1 acre based on less than one hp motors, we included additional delineation of 2 acres per unit to demonstrate the uncertainty described above. We are also proposing one container unit which is estimated to treat 20 acres. The overall treatment area of Sherwood Lake is 30 acres, assuming 1 acre:1 hp treatment area ratio. We are proposing 3 continuous monitoring buoys will be placed on Camelot Lake. One buoy will be placed in the treatment area of the container unit. One buoy will be placed in the treatment area of a representative bay. The final buoy on Camelot Lake will be at a proposed control site.

On Sherwood Lake (Figure 4), we are proposing 10 NEO units with an anticipated treatment of 1 acre based on less than one hp motors, we included additional delineation of 2 acres per unit to demonstrate the uncertainty described above. The overall treatment area of Sherwood Lake is 10 acres, assuming 1 acre:1 hp treatment area ratio. One of the NEO units proposed is capable of ozone injection along with oxygen injection. The ozone injection will only be utilized on a trial basis if allowed by the DNR. We are proposing 1 continuous monitoring buoy will be placed on Sherwood Lake.

On Arrowhead Lake (Figure 5), we are proposing 10 NEO units with an anticipated treatment of 1 acre based on less than one hp motors, we included additional delineation of 2 acres per unit to demonstrate the uncertainty described above. The overall treatment area of Sherwood Lake is 10 acres, assuming 1 acre:1 hp treatment area ratio. We are proposing 1 continuous monitoring buoy will be placed on Arrowhead Lake at the marina at the same location as the buoy installed in 2023.

2024 Monitoring Plan

As requested, Table 1 is a monitoring plan to be implemented during NB treatment.

Note that the pre and post management monitoring is used to evaluate the performance of the management and efficacy and environmental impacts of the aquatic plant management activities. For pretreatment data we will compile historical data for the proposed parameters, as well as collect data before or at the ramp up period of the nano-bubble implementation.

Table 2: 2024 Monitoring Summary

Parameter	Timing	Frequency	Monitoring Depth	Station Location	Methodology
Submerged Aquatic Vegetation	Pre-treatment sub-sample point intercept surveys in May of 2024		NA	Treatment locations	Lake-wide point intercept survey · Relative frequencies of all submergent and emergent species · Floristic quality index · Simpson’s diversity index.
	Conduct focused post-treatment sub-sample point intercept surveys in July/August of 2024		NA	Treatment locations
	Conduct lake-wide point intercept survey in August of 2024		NA	Treatment locations
Bottom Hardness Survey	Pre and post management	Pre and post management	NA	Treatment locations	Boat method used in Arrowhead lake arena study coupled with lake level measurements
Ozone Profiles	Immediately pre and intermittent post control	Weekly	Every 0.5 m throughout the entire water column	Only one ozone unit proposed for test (green dot Figure 4)	On-site ozone analyzer
Dissolved Oxygen (DO) Profiles	Immediately pre and intermittent post control	Weekly	Every 0.5m from surface to bottom	Treatment locations	Multi-probe
Phytoplankton	Immediately pre and intermittent post control	Weekly	Integrated (0-1 m or 0-2 m depending on depth of site)	Treatment locations	Utermohl method for phytoplankton identification and enumeration.

Zooplankton	Immediately pre and intermittent post control	Weekly	Net tow (lowered to 1.0 m above the bottom of a lake and then pulled up slowly at a rate of about 3 s/m.)	Treatment locations	Vertical tow with a Wisconsin net (76 cm long, 80 µ mesh) Contents of the net were washed into 118 mL jars with 95% ethanol. (Black and Dodson, 2003)
Nitrogen series: NO2+NO3, TKN, NH4	Immediately pre and intermittent post control	Weekly	0.5 ft from the bottom and 1.0 ft below surface	Treatment locations	Water & Environmental Analysis Laboratory Wisconsin DNR State Certification #750040280, DATCP #115097
React P, Total P	Immediately pre and intermittent post control	Weekly	0.5 ft from the bottom and 1.0 ft below surface	Treatment locations
BOD5	Immediately pre and intermittent post control	Weekly	1.0 ft below surface	Treatment locations
TOC/DOC	Immediately pre and intermittent post control	Weekly	1.0 ft below surface	Treatment locations
Realtime Buoys (DO, Temperature, pH, ORP)	All growing season 2024	Continuous (Every 15 minutes)	Fixed depth at 1ft below the surface	6 proposed buoys (stars Figures 3-5)	Multi-probe

*For certain conditions where we do not have enough seasonal pre-treatment data, we will choose a control site to compare to the post management conditions. There is a possible control sites on Camelot, Figure 3.

TECHNICAL MEMO

References:

Atkinson, A. J., Apul, O. G., Schneider, O., Garcia-Segura, S., & Westerhoff, P. (2019). Nanobubble Technologies Offer Opportunities To Improve Water Treatment. Accounts of Chemical Research, 52(5), 1196–1205. https://doi.org/10.1021/acs.accounts.8b00606

Chuenchart, W., Karki, R., Shitanaka, T., Marcelino, K. R., Lu, H., & Khanal, S. K. (2021). Nanobubble technology in anaerobic digestion: A review. Bioresource Technology, 329, 124916. https://doi.org/10.1016/j.biortech.2021.124916

Jia, M., Farid, M. U., Kharraz, J. A., Kumar, N. M., Chopra, S. S., Jang, A., Chew, J., Khanal, S. K., Chen, G., & An, A. K. (2023). Nanobubbles in water and wastewater treatment systems: Small bubbles making big difference. Water Research, 245, 120613. https://doi.org/10.1016/j.watres.2023.120613

Kyzas, G. Z., Bomis, G., Kosheleva, R. I., Efthimiadou, E. K., Favvas, E. P., Kostoglou, M., & Mitropoulos, A. C. (2019). Nanobubbles effect on heavy metal ions adsorption by activated carbon. Chemical Engineering Journal, 356, 91–97. https://doi.org/10.1016/j.cej.2018.09.019

Patel, A. K., Singhania, R. R., Chen, C.-W., Tseng, Y.-S., Kuo, C.-H., Wu, C.-H., & Dong, C. D. (2021). Advances in micro- and nano bubbles technology for application in biochemical processes. Environmental Technology & Innovation, 23, 101729. https://doi.org/10.1016/j.eti.2021.101729

Tucker, C. 2005. Pond Aeration. Southern Regional Aquaculture Center Publication No. 3700, United States Department of Agriculture, Cooperative State Research, Education, and Extension Service. Mississippi State University, Mississippi State, Mississippi.