Oxygenation Demonstration Project

2024 Oxygenation Project Summary

SUMMARY:

In 2017, the Orleans Pond Coalition began a research project on Sarah’s Pond to test oxygenation to determine if a more sustainable alternative exists for remediating distressed freshwater ponds, especially from Harmful Algal Blooms (HABs).  

During the first two years of the project, OPC tested a nanobubble system, but it failed to meet the project goals. After that, OPC installed an Oxygen Saturation Technology system (known as OST^TM), making upgrades and improvements to the equipment and maintenance procedures each summer, and by 2023, it was producing better results. OPC concluded its demonstration project in November of 2023, and worked with the property owners abutting the pond to allow them to continue to operate the system. The equipment operated without issue the entire 2024 season.  In 2024, the good news was oxygen remained high in the target area throughout the summer (Figure 12 is an example of the oxygen data discussed within the report).  Also, clarity reached a maximum and the average phytoplankton biomass achieved the lowest value for the multi-year monitoring period (see Figure 22). 

Figure 12. Dissolved oxygen at four depths in Sarah’s Pond in 2024 (mg/L)

Figure 22. Average phytoplankton biomass for Sarah’s Pond samples from individual years

That said, there were some low oxygen readings in shallower areas of the pond that were outside the area that the OST system was designed to address. This portion of the pond experienced a mild cyanobacteria bloom in late August and September. 

According to Kenneth Wagner, Ph.D., president of Water Resources Services who consulted on the project, such conditions appear to be the result of prolonged hot, dry weather. Dr. Wagner suggests OST could be adapted or augmented to address these other areas of the pond, and recommends operating the OST system for at least three more years as ongoing improvement has been observed.

We extend our thanks to Dr. Wagner for preparing this highly informative report, and encourage all citizen scientists interested in learning more about the oxygenation project to read the entire report, below. Thank you to Judith Bruce for sample collection, Amy Costa at the Center for Coastal Studies for sample analysis, Keith Gazaille at SOLitude Lake Management for maintenance oversight, and to the abutting homeowners, Pleasant Bay Narrows Trust, Richard and Jeanne Berdik, and the Orleans Conservation Trust (OCT) for leading operations in 2024.

Complete Data Review for Sarah’s Pond 2018-2024

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2023 Oxygenation Project Summary

Non-Technical Executive Summary – by Ken Wagner, Ph.D. President,  Water Resource Services, Inc.

Sarah’s Pond, a 5.8-acre kettlehole pond located in Orleans, MA, has experienced algae blooms, especially potentially toxic summer cyanobacteria blooms. The Orleans Pond Coalition chose Sarah’s Pond to test oxygenation as a preventive means for controlling problem algae. Oxygenation provides other benefits as well, including odor control and habitat enhancement, but the focus of this evaluation is on nutrient and algae control. This report summarizes the past five years of this research. Overall, the oxygen saturation technology system currently installed in Sarah’s Pond has demonstrated its ability to enhance conditions. 

The first two years of experimentation with a nanobubble system did not achieve goals and indicated that the installed equipment was not adequate to counter the observed oxygen demand, thereby allowing phosphorus to be released from the sediment under low oxygen conditions and supporting continued cyanobacteria blooms. A sidestream supersaturation system (SSS), or oxygen saturation technology (OST) system, was installed in spring of 2021 and operated through 2022 with improved conditions, but the target conditions were not consistently achieved. When the system was operational it did maintain adequate oxygen in the target zone within the pond, but multiple problems led to system shutdown or suboptimal performance in each of the first two years of operation.

Effort to adjust the system for greater reliability at the end of the 2022 season and start of the 2023 season produced better results in 2023. Low oxygen occurred in late August and early September when oxygen delivery was limited by a clogged pipe header. Even so, conditions in the pond remained acceptable until late October when high concentrations of cyanobacteria were observed peripherally in the pond. It is not known if this was a direct but delayed result of the low oxygen in late summer or a “last gasp” effort by cyanobacteria at the end of the season, something common in many Cape Cod lakes. High cyanobacteria counts were only observed as a function of windblown accumulations along shore. Overall, the OST system was very successful in 2023 in preventing cyanobacteria blooms in Sarah’s Pond through summer.

Overall, the oxygen saturation technology system has demonstrated its ability to enhance conditions in Sarah’s Pond. Problems that prevent achievement of all project goals are largely operational challenges common to many such systems and requiring development of warning systems and implementation of rapid response to maintain successful operation. Adjustments each year improved the performance of the OST system in Sarah’s Pond and resulted in further development of OST, which is enjoying increased use in other waterbodies with new features.

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2022 Oxygenation Project Summary

Executive Summary  by Ken Wagner, Ph.D. President,  Water Resource Services, Inc.

Sarah’s Pond, a 5.8-acre kettle hole pond located in Orleans, MA, has experienced algae blooms, especially potentially toxic summer cyanobacteria blooms (HABs). The Orleans Pond Coalition chose Sarah’s Pond to test oxygenation as a preventive means for controlling problem algae. Two years of experimentation with a nanobubble system did not achieve goals and indicated that the installed equipment was not adequate to counter the observed oxygen demand, thereby allowing phosphorus to be released from the sediment under low oxygen conditions and supporting continued cyanobacteria blooms. A sidestream supersaturation system, or oxygen saturation technology system (OST), was installed in spring of 2021 and operated through 2022 with improved conditions, but the target conditions were not consistently achieved. When the system was operational it did maintain adequate oxygen in the target zone within the pond, but multiple problems led to system shutdown or suboptimal performance in each of the first two years of operation. Effort to adjust the system for greater reliability is ongoing.

The primary process of concern in Sarah’s Pond is the loss of oxygen near the sediment-water interface. Decaying organic matter consumes oxygen faster than it can be replenished from the water above, especially during summer when water at the bottom of the pond is distinctly colder than water near the top, which impedes vertical mixing and oxygen replenishment near the bottom. That loss of oxygen facilitates a set of chemical reactions that cause phosphorus to be released from the sediment. Phosphorus is a key nutrient for algae, and its presence at a low ratio of nitrogen to phosphorus promotes the growth of cyanobacteria. Cyanobacteria can grow throughout the water column but often start at the sediment-water interface where the phosphorus is most available when oxygen is low. Cyanobacteria subsequently develop gas pockets within cells and rise to form surface blooms. Disrupting this progression is a goal of the Sarah’s Pond project.

Oxygenation in 2022 was improved over 2021, but the very hot summer presented several challenges, including heat build-up in the pumphouse which lowered the amount of oxygen being delivered to the pond. There were also brief shutdowns due to electrical service interruptions and a crack in one pipeline limited oxygen delivery to the target zone within the pond. Despite impaired performance, the oxygenation system prevented low oxygen below a depth of about 15 feet throughout summer of 2022, a major accomplishment. However, the very hot weather resulted in low oxygen at depths as shallow as 10 feet, an area the system was not designed to treat, some phosphorus was released, and a cyanobacteria bloom developed in August. Additional improvements were made at the end of the season and several more adjustments will be made before the start of operation in 2023, all intended to improve system reliability and effectiveness. Overall, the oxygen saturation technology system has demonstrated its ability to enhance conditions in Sarah’s Pond. Problems that prevent achievement of all project goals to date are largely operational challenges common to many such systems and requiring development of warning systems and implementation of rapid response to maintain successful operation. The project will seek to achieve all project goals in 2023.

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2021 Oxygenation Project Summary

Sarah’s Pond

Background

Existing remediation alternatives include dredging, chemical treatments such as alum and traditional aeration systems such as floating fountains and submersed bubblers.  The thesis of our project ponders the question:  ‘Can the health a pond significantly improve by eliminating the hypoxic (extremely low oxygen) conditions at the bottom of a pond?’  Hypoxic conditions are known to trigger the release of reduced metals and nutrients such as phosphorus from sediments, often resulting in harmful algae blooms.

Our demonstration project began a little more than 3 years ago.  The first phase of the project focused on a nanobubble technology.  We found that whilst the technology shows promise, its efficiency of oxygen transfer was still low, unable to meet the oxygen demands of the pond.  The second phase began this spring 2021 when new equipment was installed.  It’s a technology which has become more affordable in recent years – called Oxygen Saturation Technology, or OST.

OPC is sponsoring this research with the support of SOLitude Lake Management, Gantzer Water and Vertex Aquatic Systems to test the technology in Sarah’s Pond.  OST is a patent pending innovation designed to deliver high concentrations of dissolved oxygen (not bubbles) to a pond’s lower basin, blanketing the sediment/water interface.  

Executive Summary

Spring 2021 results showed exceptional results with healthy concentrations of oxygen at the sediment/water interface and by early July, pond clarity had improved significantly, greater than anyone could recall in recent memory.  However, as with any new technology, we had a few hiccups later in the summer causing equipment down time.  During this downtime, oxygen levels in the basin dropped below 3mg/L. This combined with the very high iron concentrations caused a significant ‘rust-like’ precipitation within and around the equipment.

New OST discharge platform and examples of the sludge that results when iron precipitate forms

A reassessment and upgrade of all the equipment was made by early September, including more robust piping, a ballast system for the headers and copper tubing for the aeration system.  However, the downtime did result in algae blooms and low oxygen conditions during mid-July and August.   This season has shown us how to operate our equipment in the tough environment of Cape Cod’s kettle ponds.  We believe this learning will enable uninterrupted operation, a critical factor for long term pond remediation.

OST pump house at Sarah’s Pond

A Look Back at the Oxygenation Demonstration Project over 2021

The installed unit will pump approximately 60 gallons per minute and consume only about 1.5kwh power.

Installation and monitoring began in April 2021.

LINKS to Additional Articles and Reports

Here’s a link to: “Press Release: Monday, April 26th, 2021 – Side Stream Saturation come to Orleans”

Here’s a link to: “The December 2014 Report on the first successful use of Side Stream Saturation (SSS).

Here is a copy of: Season 1’s report on OPC’s Pond Oxygenation Project on Sarah’s Pond

Here is a copy of Season 2’s “Review of nanobubble experience at Sarah’s Pond, Orleans, MA – Two year summary”

Here’s a link to: The April 2020 Water, Water, Everywhere article on Nanobubbles.