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.
2021 Oxygenation Project Summary
The Orleans Pond Coalition has been sponsoring a multiyear pond remediation research program we call the Oxygen Demonstration Project.
The primary goal of our Oxygenation Demonstration Project is to determine if a more sustainable alternative to current remediation methods exists. Overall, we made good progress this past year, showing exciting potential for this new technology exists but much more is still needed to demonstrate success.
The attached report from our technical advisor, Dr. Ken Wagner, Water Resource Services, summarizes the detailed research data and learning for this 2021 season. We encourage all to review, especially those who seek a deeper understanding of this emerging new technology, commonly know as Side Stream Saturation (SSS) and now called by the inventor, Dr Paul Gantzer Oxygen Saturation Technology (OST).
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.
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
Can our project demonstrate oxygen blanketing the water sediment layer can help remediate anoxic ponds? We hope to learn more about this question in 2022. Plans for our 2022 start up are being finalized and we believe it’s shaping up to be a big year for our research. Stay tuned for more insights. It will be exciting.
A Look Back at the Oxygenation Demonstration Project over 2021
Summary: OPC shifted Demonstration Project to focus on a more promising new technology called Side Stream Saturation.
During the past two years, the primary focus of the Sarah’s Pond Oxygenation Demonstration Project was assessing the performance of nanobubble equipment. During these two years, despite the equipment being designed to deliver excess oxygen to the test basin, the oxygen levels failed to substantially increase, nor was it successful in eliminating or substantially decreasing hazardous algal blooms (HAB’s), (for a more background information on our research effort please the see the report written by our technical consultant D. Ken Wagner/ Water Resource Services Titled: Review of nanobubble experience at Sarah’s Pond, Orleans, MA – link below). The primary conclusion from this work is that the transfer efficacy from the nanobubble system was lower than expected. And whilst further improvements in nanobubble design will undoubtedly make it a promising future technology, our conclusion from our research is that it is not ready for ponds such as Sarah’s today. That said, there have been developments with an alternate oxygenation technology called Side Stream Saturation (SSS) that have lowered the capital cost of such systems, making it a very attractive approach for Sarah’s Pond. Testing of the system by SOLitude personnel in another location has provided promising results and the report of first successful use was published back in 2014 (Water Research, Vol 67, Dec 2014, pp 129-143).
With these developments, OPC has negotiated an agreement with SOLitude Lake Management to install new SSS equipment technology and monitor its performance in Sarah’s Pond over the next three years. Our goal remains unchanged: Provide sufficient oxygen to the test basin so that hazardous algal blooms (HAB’s) can be reduced or eliminated. For the demonstration research plan, we have chosen a 1hr power motor. The maximum dissolved oxygen capacity for this equipment is 18.1kg/D. This is well above our calculated target for success of 8-12kg O2/D.
How does SSS work:
SOLitude Lake Management has partnered with Vertex Aquatic Solutions for this research. The new patented Vertex oxygen system is equipped with a water pump specified for either freshwater or saltwater, an oxygen chamber, and plumbing to bring water from the target basin and return the water, oxygenated. The system has been designed to deliver the full capacity of oxygen, allowing Vertex to guarantee 100% oxygen transfer efficiency (OTE). The high oxygen water will be injected into the basin of Sarah’s Pond where it will be dispersed throughout the entire density layer. Injected oxygen behaves like coloring dye in a pool where it moves throughout the density layer shortly after injection. There are no bubbles made and no mixing to disturb bottom sediments or compromise thermal structure. This system allows the oxygen concentration in water and at the sediment interface to be far greater than what traditional aeration could provide, making, what Vertex Aquatic Solutions asserts, the best oxygenation system on the market.
A simplified schematic of the installation plan is below:
The installed unit will pump approximately 60 gallons per minute and consume only about 1.5kwh power.
Installation and monitoring began in April 2021.