What role do microorganisms play in wastewater treatment?

Microorganisms play a crucial role in wastewater treatment primarily by breaking down organic materials and contaminants. In the treatment process, particularly in biological treatment methods like activated sludge systems and trickling filters, these microorganisms consume organic waste as their food source.

As microorganisms metabolize the organic matter, they convert it into simpler substances, releasing gases like carbon dioxide and water as by-products, along with more microorganisms. This biological degradation is essential for removing the bulk of organic pollutants from wastewater, thereby improving the overall quality of the effluent released back into the environment. The effectiveness of this process in reducing biochemical oxygen demand (BOD) is a key measure of wastewater treatment performance.

The other choices do touch on relevant aspects of wastewater treatment but do not represent the primary function of microorganisms in this context. For instance, while microorganisms contribute to sludge formation during their growth and reproduction processes, and while pH control and nutrient balancing are important in maintaining an optimal environment for these organisms, their most significant role remains in the breakdown and removal of contaminants and organic materials.