Location and Acreage:
Centreville, VA | 1.5-Acres
David Riedl, Environmental Scientist
This an apartment and condo complex located in Centreville, VA. The property contains two stormwater facilities designed to help collect and filter the rainwater that falls onto the impervious surfaces of the community. Both facilities are retention ponds, which mean they retain or hold water until it flows through or over the outflow structure. Pond 1 is roughly 0.3-acre with an average depth of three feet and Pond 2 is 1.5-acres with an average depth of three feet.
Both ponds have been managed by SOLitude Lake Management for many years. Pond 2 originally had issues with Water Lilies and Water Chestnut, which were effectively controlled within a few years. More recently, Pond 2 has experienced an occasional filamentous algae bloom during the summer season, which is normal. On the other hand, Pond 1 has had both frequent and intense planktonic algae blooms since management began. Initially, these blooms could be successfully controlled through the careful application of environmentally-friendly algaecides, but the algae always returned. More recently, even at high rates, algaecide applications were becoming less effective and sometimes not effective at all. Typically, when algaecide applications become less effective, it is due to extremely poor water quality.
Water tests were collected and analyzed for Pond 1 and showed the pond to be hypereutrophic. This means that the total phosphorus (TP) levels in the water column were at or above 96ppb (parts per billion). Specifically, in 2015 the TP for Pond 1 was 186ppb. To help restore balance to the waterbody, nutrient remediation would be necessary. A remedy for phosphorus reduction was presented to the community but was declined due to budgetary reasons. After a few more years of frequent and intense planktonic algae blooms, another water sample was collected and analyzed. In early 2019 the TP for Pond 1 was 760ppb. This amount of TP is roughly 30x higher than the recommended levels. With frequent and unmanageable algae blooms and lack of funding for nutrient remediation, something different had to be done. Fortunately, a new technology stemming from wastewater treatment was being introduced to the stormwater industry.
Scope of Work:
This case study focuses on Pond 1, its history of algae blooms, and how the installation of a nanobubble system affected the pond’s water quality, sediment levels, and overall health. Nanobubble technology was first introduced in the wastewater industry to assist in the various aspects of water treatment. Given the success of the technology in that realm, it was then introduced to the stormwater industry.
Nanobubble units are on-shore compressors that introduce oxygen and other beneficial gases into a waterbody in the form of extremely fine bubbles. The bubbles produced by nanobubble units are thousands of times smaller than those produced by traditional submersed aeration systems. This large reduction in size gives the tiny gas particles unique properties. Nanobubbles do not float to the surface like regular bubbles. This allows for significantly more efficient oxygen diffusion into the water column, where they can remain for several months without popping. There is also a function of oxidation associated with nanobubbles that facilitates algae control.
These attributes made Pond 1 a prime candidate to test out this technology. In an ongoing effort of advancing innovation, SOLitude Lake Management was able to procure a nanobubble system to test in Pond 1.
The system, a Moleaer Clear 50 nanobubble generator, was installed in the spring of 2019. Given the novelty of the technology in the stormwater industry, there was a learning curve and technical hiccups. After many changes and some help from the manufacturer, the system started to become more reliable. The system trial ran for 5 months and another water sample was collected and analyzed in late October.
The results of the October water quality showed substantial improvement when compared to the results of the water test done previously. There was a large reduction in TP, free reactive phosphorus (FRP), and total nitrogen (TN). TP reduced from 760ppb to 160ppb, which equates to a 79% reduction. FRP reduced from 574ppb to 19ppb, which equates to a 97% reduction. TN reduced from 5.2ppm to 2.8ppm, which equates to a 47% reduction. Sediment depths were also collected. Based on the industry standard of 40 depth points per acre, there was 1.9-inch reduction in sediment, which equates to a favorable 25% reduction.
In addition to the vast improvements in water chemistry, SOLitude’s lake management team and the client agree that the pond looks better than it has in years. There is a great distinction between the nuisance planktonic algae and the healthy level of beneficial algae now present in the waterbody. It’s important to note that a pond can be balanced and healthy without looking crystal clear.
Overall, the improvement in water quality, sediment reduction, and visual observations was promising. Prior to the system installation, the pond was in a high rate of decline; and almost immediately after the system began to run more consistently, improvements were noted. Moving forward, a more consistent run time and continual water testing will help to further substantiate the positive effects of this technology in Pond 1. The results from this trial bode well for nanobubble application in the stormwater and small pond and lake management industry.
In support of our belief that lakes and ponds are a precious natural resource requiring protection, SOLitude is committed to providing sustainable and renewable solutions that maintain ecological balance in the workplace and beyond.
When you partner with SOLitude, a dedicated field technician visits your lake or pond twice a month, leveraging extensive knowledge and training to carefully maintain ecological balance and preserve the appearance of your aquatic property.
Utilizing the latest GPS aquatic mapping technology and our own proprietary lake and pond management software, the experts at SOLitude collect all the data necessary to provide comprehensive analysis and in-depth solutions.