Which component of sewage systems helps to control backflow?

The correct answer is the swing check valve. This component is specifically designed to prevent backflow in sewage systems by allowing fluid to flow in only one direction. When the fluid attempts to flow backward, the swing check valve's disc swings closed under the influence of gravity and back pressure, effectively blocking any reverse flow. This mechanism is crucial in sewage systems, where backflow can lead to contamination and other issues.

The other components listed do serve various roles within a plumbing or sewage system, but they do not primarily focus on backflow prevention. For instance, a pump control valve is typically associated with regulating the flow and pressure of liquids within a pump. A float valve is designed to serve as a level control device, maintaining a predetermined liquid level in a tank or basin. A solenoid valve controls the flow of liquid in response to an electric signal but does not inherently prevent backflow. Thus, the swing check valve stands out as the appropriate answer for controlling backflow in sewage systems.