Reducing nutrients in Puget Sound

Wastewater treatment plants are the largest source of human-caused nutrients to Puget Sound. Water is treated before discharged into the Sound, but nutrient removal is not part of the typical treatment process. A wastewater treatment plant can comply with their permit limits while still discharging nutrients to Puget Sound.

During wet seasons, rainwater can carry nutrients across lands into rivers. Nutrient-laden water that runs off the land into rivers is referred to as "runoff." This runoff is from human land-use activities, such as using too much fertilizer. Rivers then transport nutrients throughout watersheds and sometimes to Puget Sound. In the summer, rivers contribute lower levels of nutrients because their streamflow is lower due to less rain.    

During the spring and summer months when days are longer and the water is warmer, phytoplankton and algae have higher growth and reproduction rates. Animals eat the increased populations of phytoplankton and algae. While they eat, they consume oxygen — resulting in decreases in dissolved oxygen.

We are also seeing shifts in plankton communities away from species that photosynthesize and produce oxygen to greater numbers of species that consume oxygen rather than produce it.

Washingtonians need to work together to reduce nutrient contributions. The amount of nutrients brought into the system by humans is related to the number of people living in the region. As state populations continue to grow, so does human nutrient loading. Nutrients will cause a problem for Puget Sound unless we change the way we live on the land and treat our wastewater.