Safety, Regulations, and Recordkeeping
Regulatory content is largely memory work, but questions punish imprecision. Know the Safe Drinking Water Act structure: EPA sets national rules, states take primacy, and requirements arrive as maximum contaminant levels (MCLs) or treatment techniques. High-yield numbers: combined filter effluent turbidity 0.3 NTU in 95 percent of monthly samples and never above 1 NTU; TTHM 80 µg/L and HAA5 60 µg/L locational running annual averages; lead action level 0.015 mg/L and copper 1.3 mg/L at the 90th percentile; nitrate 10 mg/L as N; arsenic 10 µg/L. The Consumer Confidence Report goes to customers annually by July 1, and certain violations must reach the state within 24 hours.
Safety: chlorine gas is heavier than air - evacuate uphill and upwind, and use SCBA, never a dust mask or cartridge respirator, for potentially IDLH atmospheres. Never move a leaking cylinder unless it can be done without exposure. Confined spaces require a permit, atmospheric testing (oxygen roughly 19.5–23.5 percent), ventilation, an attendant, and a rescue plan. Know lockout/tagout, hazard communication and SDS, PPE, electrical safe work practices, and trenching rules.
Recordkeeping: operational logs, chemical feed records, calibration and maintenance sheets, sample results, and DMR or state reports must be complete, legible, and retained for the required period; falsifying a report is a serious violation.
Traps: quoting an MCL where a treatment technique applies; treating an action level as an MCL; mixing up the CCR deadline; and assuming a respirator alone protects against chlorine.