ALGAE | Activated Sludge Process | Wastewater Treatment Plant

ALGAE

Algae are photosynthetic plants that are microscopic and lack roots, stems, and leaves. They are mostly autotrophic, and as a byproduct of synthesis, they produce oxygen. The generation of oxygen is useful in wastewater treatment, but algae forms are long and filamentous, and they clog treatment plant discharge weirs. They also clog filters, clog pipes, and otherwise disrupt treatment plant operations.

Algae frequently indicate a nutrient-limiting situation, as a sudden excess of a specific nutrient will cause an algal bloom, or a burst of algae growth in a reactor or receiving water.

Blooms caused by nitrogen, for example, are said to occur in a nitrogen-limited environment that suddenly receives significant concentrations of available nitrogen. This is the primary cause of algae blooms in lakes and ponds during the summer, especially where residential properties line the shore and wastewater is disposed of through subsurface disposal fields near the shore. The wastewater discharged contains a high concentration of nitrogen compounds, which flow through the soil to the body of water and provide vast amounts of available nitrogen to the algae. Nonpoint source runoff from lawns, golf courses, farms, and other areas contributes more nutrients to rivers and streams than subsurface disposal.

Similarly, phosphorous, which is becoming more of a concern today, can be discharged to the soil via wastewater or, more commonly, fertilizers used for grass and plants throughout the watershed. When excess phosphorus reaches the receiving water, an algae bloom frequently occurs. In general, freshwater environments will be phosphorus limited, whereas marine environments will be nitrogen limited.