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Daphnia

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Identification

  • Reddish-pink color
  • Flea-shaped
  • Macroscopically appear oval-shaped

Why Do I have It?

  • Low available BOD
  • Low levels of ammonia
  • Suspended bacteria and algae present

Associated Plant Conditions

Daphnia are found in final clarifiers, typically seen moving in pink or red clouds. They can also cause high effluent TSS issues. If you have Daphnia in your clarifier, it is an indication that you have a high-quality effluent.

Treatment

Daphnia is an indicator of a healthy wastewater plant and treatment is not typically required. If your plant is experiencing TSS issues, contact a technical rep for information and recommendations.

Under the Microscope and in Your Plant

Daphnia, commonly referred to as water fleas, are small crustaceans closely related to shrimp. They prefer water temperatures between 18-21°C (65-70°F), as well as fall or spring sunlight. These one-eyed crustaceans consume yeast, algae, bacteria, and protozoa. The most optimal temperature for their breeding is 21°C (70°F). Daphnia’s eggs can lie dormant for decades and scientists have used these eggs to see how Daphnia have evolved over time. Daphnia produce hemoglobin, causing their reddish-pink appearance. They will turn more pinkish in color if dissolved oxygen levels decrease. When present in abundance in final clarifiers or polishing lagoons, Daphnia will form pink clouds. They are typically used for whole effluent toxicity testing; their ability to thrive in a final clarifier is an indicator of an effective wastewater treatment process. The presence of Daphnia does not always indicate an issue occurring within the wastewater system, however, there are rare instances when an overabundance of Daphnia can cause high effluent TSS.

Interesting Facts

  • Daphnia were the first crustacean to have their genome sequenced and it was discovered that humans and Daphnia share many of the same genes

References
Crites, R.W., Middlebrooks, E.J., & Reed, S.C. (2005). Natural wastewater treatment systems. Taylor & Francis Group.

Meyer, M. (2018). Web exclusive: What water fleas say about your lagoon water quality. Water & Wastes Digest. https://www.wwdmag.com/wastewater-
treatment/web-exclusive-what-water-fleas-say-about-your-lagoon-water-quality

Wallitschek, J. (2019). A microscopic look at the role and life cycle of daphnia in wastewater lagoons. Wastewater Operator.
http://wateroperator.org/blog/PostId/1480/a-better-look-at-the-role-and-life-cycle-of-daphnia

Ward’s Science (2013). Daphnia. [PDF File]. https://media.vwr.com/emdocs/docs/scied/Daphnia.pdf