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A Microscopic Look at the Role and Life Cycle of Daphnia in Wastewater Lagoons

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Knowledge of lagoon microbiology can provide proactive insight into the present conditions of your wastewater treatment processes. Since we have already covered general wastewater microbiology in a previous featured video, this week’s blog post will highlight the specific roles of Daphnia in wastewater digestion.

Daphnia, also known as water fleas and Ceriodaphnia, are metazoan crustaceans that maintain a useful position in the wastewater digestion food chain if controlled by a limiting food source or the careful addition of hyacinths. These one-eyed crustaceans can consume yeast, algae, bacteria, protozoa and occasionally sludge during the winter. In the wild Daphnia are a food source for small fish, tad poles, and aquatic insects. General stressors for water fleas include cold temperatures, overcrowding, low dissolved oxygen (DO), high ammonia levels, and high pH.

To provide context for Daphnia's role in lagoon treatment requires a review of the wastewater food chain. Bacteria are at the heart of waste digestion breaking down organic material into settleable particles. Protozoa feed on these bacteria populations reducing the organic load. Metazoan organisms like Daphnia keep the populations of protozoa, bacteria, and algae in check.

Daphnia can be useful to wastewater operators under healthy lagoon conditions. These water fleas control green algae populations in the summer. As long as cyanobacteria weren't competing with those algae populations, overall pond health will improve by a reduction in total suspended solids (TSS), cloudiness, and turbidity. At the cost of growing Daphnia populations, dissolved oxygen levels decrease.

Water fleas are often indicators for low dissolved oxygen and water toxicity. Under low DO, Daphnia produce hemoglobin to increase oxygen efficiency. This hemoglobin turns water fleas reddish-pink causing red streaks to appear in your lagoon. When operators see red water fleas, they should consider treating the lagoon with aeration or mixing. Given their low tolerance to toxicity and short generational cycles, Daphnia are also used in the EPA's whole effluent toxicity tests (WET).

Now that we have a better understanding of water fleas, we can appreciate this microscopic view of Daphnia as told by Sacramento Splash. The video reviews the natural life cycle and anatomy of these helpful water crustaceans.

Featured Video: Using Decommissioned Wastewater Tanks for Fish Farming

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Just when you think you've seen it all, someone comes up with a crazy idea that holds some promise. This just might be true in the case of a local aquaculture businessman, who, along with a Kentucky State University researcher, looked at outdated wastewater treatment plants and source water reservoirs and envisioned profitable fish farms! 

This week's featured video explains how Steve Mims and Tim Parrott used a USDA grant a few years ago to turn decommissioned wastewater plants into working aquaculture farms (pg. 8) using treated effluent in digester tanks and daphnia (as fish food) from upgraded facilities that are often just next door. The tanks don't generate waste because the water cycles right back to the treatment plant.  

His big idea? To establish regional fish hatcheries through public-private partnerships, with young fingerlings sold to local farmers to raise in their own ponds all the while adding commercial-level fish and caviar production to the rural economies of Kentucky. So add fish farming to all the creative ways to recycle wastewater that people have been coming up with recently!