ADEQ Water Treatment Grade 4 Practice Test 2026 – Comprehensive Exam Preparation

Detention time is the water’s stay in the sedimentation basin to allow suspended particles to settle by gravity. For a typical drinking water treatment process, the basin is designed to provide about two to four hours of detention. This duration gives enough time for most flocs to settle without making the system unnecessarily large or costly. If the time is too short, solids won’t settle well and removal efficiency drops; if it’s much longer, the basin becomes oversized and less economical. So, the common target range is roughly two to four hours. Options shorter than that don’t allow full settling, while much longer times are not practical for most plants.