Preventing a Bloodworm Invasion

Midge fly infestations can pose considerable challenges for activated sludge systems and lagoons. Also known as Chironomids or bloodworms in their larvae stage, these insects resemble mosquitos without the blood sucking proboscis. Adult males can be distinguished from females based on their feather like antennae. After dormancy in the winter, midge flies emerge in the summer ready to lay between 100 and 3,000 eggs per female.

Though midge flies do not suck blood like mosquitos, they disrupt communities in other ways. Swarms annoy both local residents and operators by flying into unsuspecting mouths and flooding outdoor lighting. A study by Selden et al. (2013) found that wastewater operators can develop allergic reactions from midge fly exposure. Chironomids can also cause quite a startle to the public when bright red larvae make their way into drinking water systems.

When it comes to maintaining treatment systems, wastewater operators may be most concerned with the larvae stage of midge flies. Their sticky red bodies cling to suspended solids encasing them in a cocoon of decaying organic matter. Under the protection of these cocoons, they can consume considerable amounts of sludge, bacteria flocc, and nitrifying bacteria. An infestation will cause sludge clumping, rising solids, or foaming issues. In one small town a bloodworm invasion wreaked havoc on an activated sludge plant over a single weekend. The wastewater operator found sticky clumps of eggs had congested the system’s pumps while larvae had eaten away at his mixed liquor suspended solids (MLSS).

Facultative lagoons and secondary clarifiers are a favored breeding ground for these pests. Midge flies prefer to lay their eggs in still, high-nutrient water with fixed media, floating scum, or algae. Once the eggs hatch, larvae will likely sink to the bottom to feed on organic matter and sludge. The hemoglobin that gives bloodworms their red color also allows them to live in low dissolved oxygen (DO) conditions.

To avoid bloodworm infestations, operators should focus on encouraging circulation and limiting food sources. Systems can start midge fly control with mixing, limiting surface scum and algae, installing bug zappers, attracting bats and swallows, or turning off lights at night. Introducing a predatory fish can also help. Lagoon operators can encourage circulation by cutting back overgrown vegetation. Any dead spots in circulation should be addressed. When these methods don’t work, some systems will use larvicides and chemical agents as a last resort. Operators should check that the control methods they’ve selected are approved by their local regulatory authorities before use.

When summer starts make sure your treatment system is kept clean and free of obstructions to circulation. With good preventative maintenance, you can spare yourself the nightmares of a bloodworm invasion.

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

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: Smelly Lagoon? Diagnosing and Correcting Lagoon Odors

As weather begins warming up for spring, many lagoons system owners have to manage odor issues and water turnover. In this week’s featured video, an experienced “Lagoon-atic” describes what causes lagoon odors and the best practices to manage them.

The most dreaded odors from lagoons systems are caused by sulfur dioxide and hydrogen sulfide gases. These gases emit a rotten egg odor that often leads to complaints from locals in the area. Under oxygen-stressed conditions, insufficient dissolved oxygen (DO) levels favor anaerobic digestion of biological oxygen demand (BOD) and sludge by sulfur bacteria.

This video also discusses the earthy smell of a healthy lagoon and other odor causing problems a lagoon may experience. Grassy odors indicate high levels of algae favored by warming temperatures, long detention times, excess sunlight, and excess nutrients. As spring approaches the solubilization of solids from the sludge blanket can cause nutrient release. This issue can be corrected by a reduction in the sludge blanket. Fishy odors may result from cyanobacteria growth under conditions with warm temperatures, high nutrient levels, thermal stratification, and still water. The longer water remains still, potential for cyanobacteria growth increases. Cyanobacteria can be reduced with chemical control, aeration, circulation, and ultrasonic waves. 

Spring time has potential to pose many odor issues for lagoon systems. Operators can maintain a healthy lagoon by ensuring sufficient DO levels, controlling sludge buildup, and mixing.