Safety, Regulations, and Laboratory Analysis
Safety
Confined spaces
A confined space has limited entry, is not designed for occupancy, and restricts egress; a permit space adds a hazard. Test the atmosphere before entry and monitor continuously: oxygen 19.5-23.5%, LEL under 10%, hydrogen sulfide under 10 ppm, carbon monoxide under 35 ppm unless the permit says otherwise. Ventilate; never rely on odor. Most sewer fatalities are would-be rescuers, so call a trained rescue team.
Chemical hazards
Chlorine gas is heavier than air and settles in low spots; ammonia vapor is lighter. Sodium hypochlorite releases chlorine when acidified, so never mix hypochlorite with acid. Know SDS locations, eyewash and shower locations, and proper PPE for each chemical.
Physical hazards
Lockout/tagout for pumps, mixers, and blowers, and verify zero energy. Trench protective systems are required at 5 ft depth (sooner if unstable), spoil 2 ft back from the edge, and a ladder within 25 ft of travel. Use high-visibility PPE and traffic control.
Worked example
A wet well reads 18.9% oxygen with 30 ppm H2S. Do not enter. Ventilate and re-test; if H2S stays above the permit limit, the entry requires supplied-air respiratory protection and full permit controls.
Traps
Assuming the meter is fine because it was calibrated last year. Entering to rescue without PPE. Using a dust mask for chlorine. Treating a gas reading taken at the top of the well as representative of the bottom.
Regulations
Framework
Three layers: the federal Safe Drinking Water Act and Clean Water Act, the Georgia EPD rules that implement them, and the permit or certification that applies to your facility. Drinking water rules are in Georgia Chapter 391-3-5 and cover turbidity, disinfection, disinfection byproducts, LT2, the revised total coliform rule, and the consumer confidence report. Wastewater rules are in Chapter 391-3-6, with NPDES permits setting effluent limits, monitoring, and reporting. Operator certification is handled through the Georgia Board of Examiners, with licenses classified by plant type and grade.
Reporting duties
Consumer confidence report by July 1 each year; sanitary surveys about every 3 years (5 for outstanding performers); coliform repeats within 24 hours; Tier 1 public notice within 24 hours for acute violations such as E. coli or nitrate. NPDES requires discharge monitoring reports, and a 24-hour oral report for noncompliance that may endanger health, followed by written notice. The operator in responsible charge signs and certifies reports.
Worked example
A routine sample is E. coli positive. Notify the state within 24 hours, issue Tier 1 public notice within 24 hours, collect repeat samples, and evaluate the cause. Missing the clock is itself a violation, separate from the contamination.
Traps
Mixing Tier 1, 2, and 3 timelines. Assuming limits may be averaged differently than the permit states. Forgetting recordkeeping and that falsifying a report is a separate offense.
Laboratory Analysis
Sampling integrity
Know grab versus composite, chain of custody, preservation, and holding time. Chlorine and pH are measured in the field immediately because they change in transit. Metals use nitric acid preservation; ammonia and nitrate use sulfuric acid; chlorine samples use thiosulfate. Cool samples to 4 degrees C unless the method says otherwise. BOD should be run within 48 hours.
Core methods
BOD5 is run at 20 degrees C for 5 days, seeded, with a nitrification inhibitor. TSS uses a glass fiber filter dried at 103-105 degrees C. Turbidity uses a nephelometer. Chlorine residual uses DPD. pH uses a meter calibrated with buffers bracketing the sample. Coliforms use membrane filtration or an enzyme substrate method.
QA/QC
Duplicates, matrix spikes, method blanks, calibration curves, control charts, and defined data quality objectives. Report no more significant figures than the method supports.
Worked example: BOD
300 mL bottle, 30 mL sample, initial DO 8.0 mg/L, final DO 4.0 mg/L, no seed correction. Dilution factor = 300/30 = 10. BOD = (8.0 - 4.0) x 10 = 40 mg/L. Depletion must be at least 2.0 mg/L and residual at least 1.0 mg/L, or the dilution is wrong and the test is repeated.
Traps
Using the bottle volume instead of the sample volume. Applying the seed correction with the wrong sign. Measuring chlorine after transport. Reporting a below-detection result as zero. Reading a buret or meter beyond its precision.