Wastewater Treatment Plant Gas Detection Solution: Protecting Personnel and Environmental Safety

Wastewater treatment plants are critical facilities for urban water management, but their operations generate various toxic, flammable, and irritant gases. Areas such as aeration tanks, anaerobic digesters, sludge tanks, sewage wells, and chlorination rooms carry risks of leaks of H₂S, NH₃, CH₄, Cl₂, and ClO₂. These gases can irritate the respiratory tract, cause dizziness, or at high concentrations, lead to acute poisoning, suffocation, or even explosions.

Recent incidents of poisoning and fatalities caused by H₂S or Cl₂ leaks in wastewater plants highlight the importance of safety. According to regulations such as GB 18918-2002, GBZ 2.1-2019, and GB 18218-2018, professional, continuous, and reliable gas detection systems must be installed in high-risk areas. The Nexisense SGA-501 is designed for the complex environments of wastewater plants, providing comprehensive safety protection.

Main Hazardous Gases and Their Risks

• H₂S: Produced in anaerobic digesters, sludge dewatering, and sewage wells; highly toxic and irritating; 10 ppm causes irritation, >100 ppm can be lethal.

• NH₃: Present in aeration tanks and sludge dewatering areas; high concentrations irritate respiratory tract and eyes; long-term exposure damages lungs.

• CH₄: Produced in digesters and biogas tanks; flammable and explosive, explosion limit 5–15% VOL.

• Cl₂ and ClO₂: Risk in chlorination rooms; highly corrosive and toxic, even small amounts can cause acute poisoning.

These gases tend to accumulate in low-lying areas, under manholes, or at tank bottoms. Traditional manual inspections are slow and may not detect early leaks. Fixed online monitoring is currently the most reliable protection method.

Advantages of SGA-501

• Detects multiple gases: H₂S, NH₃, CH₄, Cl₂, ClO₂, CO₂; single or multi-gas configurations.

• High accuracy and fast response: ppm-level resolution, T90 ≤ 45 seconds.

• Flexible power supply: DC 24V, plug & play.

• Multiple outputs: 4–20mA, RS485 Modbus RTU, integrates with PLC, DCS, or SGA-800 controller.

• High protection: IP65+, optional explosion-proof (Ex d IIC T6 Gb).

• Local display and alarm: LCD screen, ≥85dB audible and visual alarm.

• Anti-interference design: optimized for common cross gases in wastewater plants.

Compact and easy to install, suitable for humid, corrosive, and confined spaces.

Detection Points and Installation Guidelines

• Chlorination rooms and Cl₂/ClO₂ storage: heavier than air; install 30–50 cm above the ground near cylinders, injectors, and flanges.

• Aeration and equalization tanks (NH₃, H₂S): 1–1.5 m above walkways; avoid turbulent aeration areas.

• Anaerobic digesters and sludge tanks (CH₄, H₂S): CH₄ lighter than air, install in upper space; H₂S heavier, dual points top and bottom.

• Sewage and collection wells: above manholes or fixed on walls, prioritize low-lying zones.

  
  

Installation precautions:

• Avoid direct water or steam exposure.

• Use shielded, corrosion-resistant cables.

• Calibrate with standard gas before operation.

• Integrate multiple points via SGA-800 or central control system.

Integrated Alarm and Control System

• Connect multiple SGA-501 units to SGA-800 for centralized monitoring and zone display.

• Staged alarms: level 1 (H₂S 5 ppm), level 2 (H₂S 10 ppm).

• Automatic actions: activate fans, water sprinklers, shut off chlorine pumps.

• Data platform integration: cloud display, mobile app, SMS notifications.

• Emergency flow: detection → local alarm → control linkage → personnel with masks → record and post-event analysis.

  
  

FAQ

1. Priority gases: H₂S and Cl₂; CH₄ and NH₃ as per process coverage.

2. Installation height: H₂S 0.5–1.5 m; Cl₂ 30–50 cm from ground.

3. Stability in humid/corrosive environments: IP65+, sensor probes coated for corrosion, PCB protected; 2–3 years life with periodic cleaning.

4. Integration with PLC/SCADA: 4–20mA or RS485 Modbus RTU for real-time display, alarms, and control.

5. Chlorine leak response: local ventilation, sprinklers, shut off pumps, close valves, plant-wide alarm and SMS; SGA-800 supports flexible relay output.

6. Sensor life: 2–3 years; modular replacement, no need to send back, completed in 5 minutes on-site.

7. Coverage per detector: 5–10 m radius; large plants require grid layout with 2–4 detectors per key unit.

8. Data usage: local + cloud storage, concentration trends, alarm logs, calibration and maintenance records; supports inspection, hazard correction, drills, and regulatory compliance.

Conclusion

Safety in wastewater treatment plants is essential for urban water protection and public health. The SGA-501 provides reliable, fast detection, easy integration, and automated alarms, forming a complete defense from early warning to response. Implementing a professional gas detection system protects personnel, prevents accidents, and enhances intrinsic safety and corporate image. For monitoring upgrades or hazard inspections, practical and comprehensive solutions are available tailored to plant processes and conditions.