Distribution and Collection System Operation
What you must know
Distribution: pressure management, storage (elevated, ground, hydropneumatic), water age and tank turnover, residual maintenance, nitrification control in chloraminated systems, DBP hotspots, main breaks and repair disinfection, cross-connection control and backflow devices, valve and hydrant exercise, flushing programs, meters and leak detection.
Collection: gravity sewers and slopes, manholes, lift stations and wet wells, inflow and infiltration, sanitary sewer overflows and combined sewer overflows, grease and root control, hydrogen sulfide generation and corrosion, CCTV inspection, smoke and dye testing, and cleaning by jetting, rodding and bucketing.
Traps
- Quoting pressure in feet of head when the question asks psi - and forgetting NJ's 20 psi minimum.
- Ignoring that low velocity deposits solids in sewers while long detention degrades water quality in tanks.
- Treating every main break identically; asbestos-cement pipe and any cross-connection risk change the repair and disinfection protocol.
Rules of thumb
1 psi equals 2.31 ft of water column; 1 ft of elevation equals 0.433 psi. A tank with 100 ft of water above a tap produces 100 / 2.31, about 43 psi. Keep self-cleansing sewer velocity near 2 ft/s, with an upper bound around 10 ft/s to limit scour and sulfide generation.