Pretreatment equipment typically consists of:

The pretreatment equipment is essential in the initial phase of wastewater treatment, focusing on removing large solids, debris, and grit that could damage or clog downstream processes. The correct combination of equipment for this purpose includes a bar screen, comminutor, and grit chamber.

A bar screen is designed to filter out large objects such as sticks, leaves, and plastic waste, allowing only smaller materials to pass through. Following this, a comminutor further reduces the size of the solids, such as food waste and other organic materials, preparing them for removal or further processing. The grit chamber captures heavier particles, such as sand and gravel, which ensures that these materials do not interfere with subsequent treatment processes.

The other options present equipment suited for different stages of wastewater treatment or different functions. For instance, primary and secondary clarifiers are used in the sedimentation stage, while sand filters are part of tertiary treatment. A screen and sedimentation tank are also used later in the treatment process, while a chlorinator is involved in disinfection, which is another step that occurs after pretreatment. Each piece of equipment has a specialized role in the treatment train, contributing to the overall efficiency and effectiveness of the wastewater treatment system.