Tennessee Wastewater Operator Practice Exam

Mixed liquor suspended solids growth primarily occurs from what?

1. New cell production by the microorganisms

2. Loss of effluent through the outflow

3. Settling of solids in the clarifiers

4. Recycling of sludge

The correct answer is: New cell production by the microorganisms

The growth of mixed liquor suspended solids primarily results from new cell production by microorganisms. In wastewater treatment, microorganisms play a crucial role in breaking down organic matter. As these organisms metabolize the waste, they reproduce through cell division, leading to an increase in the total biomass present in the mixed liquor. This process of new cell production is essential, as it not only helps in the treatment of wastewater by degrading pollutants but also contributes significantly to the total concentration of suspended solids in the mixed liquor. This contrasts with other processes like loss of effluent through the outflow or settling of solids in the clarifiers, which do not contribute to growth. Loss of effluent would actually reduce the concentration of mixed liquor suspended solids, while settling mainly pertains to removing solids from suspension rather than contributing to growth. Recycling of sludge is more about reintroducing settled solids into the system rather than generating new biomass. Therefore, the primary mechanism for the growth of mixed liquor suspended solids is indeed the new cell production by the microorganisms within the system.