Algae is one of the main complaint of pond owners. This abundant and unwelcome plant life in is often considered a nuisance for pond keeper and wastewater treatment plant operations. Algae forms in a pond in the presence of nutrients in the water, and sunlight. It is important to note that without photosynthesis, algae cannot exist. The nutrients they strive on are mostly comprised of Ammonia, Nitrate and Phosphorus, the main ingredients founds in fertilizer and wastewater treatment ponds. In clean water ponds, those nutrients result from the breakdown of debris such as leaves, grass, and other windblown organic matter as well as from fish waste and uneaten fish food. As these items decompose, the nutrients are released in the water and become the food for algae.
For many pond owners, algae can make pond and fish keeping a chore that is constant and difficult to deal with. Algae will cover rocks and clings to the surface of your pond and pond liner. It will also lead to as the usual green water also called pea soup effect. For wastewater plant operators, it may mean that permits are not met, with TSS concentration well in excess of what is allowed. In addition to other non-life-threatening challenges, algae obscure colorful fish and deplete valuable oxygen. This in turns can lead to fish death, insufficient water treatment, etc… In very high concentration, algae blooms can discolor the water and out-compete, asphyxiate and poison other life forms. In some case, excessive algae may also increase evaporation by providing wet, darker surfaces that absorb more sunlight energy and are dried out to the wind. Some algae, such as blue green algae, are toxic to humans and dogs. Excessive algae growth can indicate problems with water quality. Water can become unsuitable for fish, swimming, and toxic or lethal to other animals.
Algae growing in an aerated lagoon system will increase both the TSS and the CBOD5 of the effluent. In fact, most of the effluent CBOD5 is the result of algae that grows in the lagoon. In systems treating municipal wastewaters, the effluent TSS and CBOD5 will often be many times that which would occur if the algae had not been present. Effluent values of these parameters inflated by algae does not correctly measure how well the lagoon is removing the influent TSS and CBOD5. Since algae are a distinct liability and play no beneficial role in aerated lagoons, controlling algal growth should be a main focus to those responsible for the design and operation of these systems.