What Causes Green Surface Growth in Wastewater Lagoons?

Green surface growth is a common sight in many wastewater lagoons, especially during the warmer months of the year. While it can be alarming, it is often the result of natural biological processes occurring within the treatment system.

Several environmental factors work together to create conditions where green growth becomes more noticeable. Understanding these factors helps operators better interpret changes in water quality and make informed management decisions.

The Five Primary Factors

1. Sunlight

Like all plants and algae, aquatic organisms rely on sunlight to grow. As the days become longer during the spring and summer, increased sunlight provides more energy for biological activity.

2. Nutrient Availability

Phosphorus and nitrogen are two of the primary nutrients that support biological growth in water. Wastewater naturally contains these nutrients, making lagoons an environment where growth can occur if conditions are favorable.

3. Warm Water Temperatures

Warmer water accelerates biological processes. During summer, increased temperatures often result in faster nutrient cycling and greater biological activity throughout the lagoon.

4. Water Movement

Areas with limited circulation or mixing may allow biological material to accumulate near the surface, making green growth more visible.

5. Seasonal Conditions

Seasonal changes influence nearly every aspect of lagoon performance. Rainfall, temperature, sunlight, and biological activity all contribute to changing water conditions throughout the year.

Frequently Asked Questions

Is green surface growth always a sign of poor treatment?

Not necessarily. Seasonal changes can naturally increase biological activity without indicating an operational problem. Water quality testing provides a more complete picture of lagoon performance.

Can nutrient levels influence surface growth?

Yes. Phosphorus and nitrogen are essential nutrients for aquatic organisms. Monitoring nutrient concentrations helps operators understand changing conditions within the lagoon.

The Bottom Line

Green surface growth is usually influenced by multiple environmental factors rather than a single cause. By routinely monitoring water quality and understanding seasonal trends, operators can make informed decisions that support long-term lagoon performance.