Wastewater Collection System Operations and Maintenance
Collection system O&M is the day-to-day work that keeps gravity sewers and appurtenances flowing: routine cleaning, root and grease control, odor management, and condition monitoring. A Class IV candidate should understand why preventive maintenance beats reactive repair, how cleaning methods differ, and how maintenance records feed the asset management program.
Know the main cleaning tools and when each applies. Hydraulic cleaning (high-velocity jetting) scours grease, grit, and light debris and is the default for most lines. Mechanical cleaning (rodding, bucket machines, scrapers) is used for heavy roots and hard blockages where jetting alone stalls. Balling and pigging verify flow capacity and polish lines after jetting. Match the tool to the problem: jetting a root mass often just packs it tighter.
Traps
Questions often test the relationship between velocity, slope, and solids deposition. Self-cleansing velocity is commonly cited near 2 ft/s (0.6 m/s) at design flow; slower lines accumulate grit and grease. Another trap is confusing the purpose of a manhole inspection versus a CCTV inspection: the manhole inspection documents the structure and frame/cover; CCTV documents the pipe interior.
Rule of thumb
Schedule cleaning by measured need, not the calendar. Use a hotspot list built from repeat blockages, grease complaints, and low-velocity segments, and re-rank it each quarter. A line that plugs twice in a year is a candidate for root foaming, grease interceptor enforcement, or rehabilitation review.
Worked example
A 300-ft segment at 0.4% slope carries low dry-weather flow and plugs every spring. Jetting restores flow but the plug returns. The fix is not more jetting frequency alone: investigate root intrusion by CCTV, check upstream grease sources, and consider root foaming or lining. Document each event so the asset record justifies the capital decision.