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Town consultant releases report on A-Pod success and warns on sulfur overuse

Higgins Environmental Associates (HEA), the consultant hired by the Town of Concord to install and run the A-Pod technology for removing toxic algae blooms from White Pond, has issued their report on the 2022 season.

Some of the milestones achieved include:

  • A fifty one percent (51 %) reduction in cyanoHAB biovolume (e.g., cyanoHAB biomass by water body volume) was achieved for White Pond from October 2021 to October 2022.

  • Board of Health restrictions or advisories for water contact were not required or issued in Year 2022 when a total of four A-Pods were in-place and functioning to control and remove cyanoHABs and cyanotoxin health risks.

  • Water clarity improved to a Year 2022 (May to November) median of 24.2 feet versus the historic 30- year (1987-2017, typically June to August) median of 19.6 feet.

  • The phosphorus concentration in cyanoHAB solids removed from 2021 to 2022 decreased by 44%; the biogeochemically-active nutrient sulfur decreased by 27%; and total nitrogen increased by 310% in cyanoHABs removed over time which corresponded to a 75% (maximum of 0.5 mg/L) increase in total nitrogen concentration of surface water outside the A-Pod Trap and collection area from June to October 2022.

  • HEA documented the presence of “benthic meadows” of beneficial benthic macroalgae (Nitella) and moss from depths of approximately 5 to 45 feet throughout the pond. Walden Pond has similar benthic meadows. These would serve as a sink for nutrients and as habitat for benthic fauna.

HEA also noted that high levels of sulfur as a nutrient to toxic algae blooms should be on the town's priority list:

  • HEA recommends that the Town of Concord consider including the biogeochemically-active macronutrient sulfur into any existing or upcoming guidance for promoting judicious use of similar nutrients or alternate practices that use less nutrients including sulfur by Concord’s businesses, municipal services and residents. Sulfur is a component of many common residential and commercial use products and practices including within detergents, water quality additives, lawn care products and fertilizers.

The full HEA report is available below, as well as the laboratory data for 2022.

HEA 2022 White Pond Report Feb 8 2022 rs
Download PDF • 2.48MB

Laboratory Data for HEA 2022 White Pond Report rs
Download PDF • 2.51MB

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