Which statement is true about screening in preliminary treatment?

• A. It catches debris before entering the system
• B. It disinfects water
• C. It discharges to the environment
• D. It aerates

Answer: (A)

Screening in preliminary treatment is about removing large solids from the wastewater as it enters the treatment facility. Screens catch items like plastics, rags, and other debris, preventing them from moving further into the system. This protects pumps and piping, reduces blockages, and minimizes wear on downstream equipment, helping the rest of the treatment process run smoothly. Disinfection happens later in the treatment train, not at screening. The water isn’t discharged to the environment at this stage; it simply passes through the screens and continues on to the next treatment steps. Aeration isn’t part of screening either; aeration is used in later stages to introduce oxygen for microbial digestion.