🏭 ETP & STP Monitoring Instrumentation

Countronics pH controllers, ORP meters, conductivity controllers, and TDS instruments are used in effluent treatment plants (ETP) and sewage treatment plants (STP) across India — for continuous parameter monitoring, automatic dosing control, and pollution control board compliance.

Quick Answer: Effluent and sewage treatment plants use dual-limit pH controllers and ORP controllers to automatically neutralise effluent to CPCB-compliant pH levels (6.5-8.5) and ensure adequate disinfection before discharge — without manual monitoring.

Why ETP and STP Need Continuous Monitoring

Industrial and municipal effluent must be treated to meet discharge standards set by CPCB (Central Pollution Control Board) and state pollution control boards before release into water bodies or municipal drains. Non-compliance attracts legal penalties, closure orders, and environmental liability. The key parameters monitored at every ETP and STP are pH, ORP (for disinfection), conductivity, and TDS.

Manual grab sampling and laboratory analysis — where a sample is collected, sent to a lab, and results returned hours or days later — is insufficient for real-time process control. Continuous online instruments provide real-time values and can automatically trigger corrective dosing the moment a parameter deviates.

pH Monitoring & Dosing Control

Industrial effluent from electroplating, textiles, chemicals, food processing, and pharmaceuticals can be highly acidic or alkaline. Neutralisation to pH 6.5–8.5 before discharge is mandatory under CPCB norms. The 112pH dual-limit controller automates this neutralisation process by activating acid or alkali dosing pumps automatically.

Two independent relays for acid and alkali dosing. Isolated 4-20mA output. Auto temperature compensation. For automatic pH neutralisation in ETP.
Display and transmit pH simultaneously. 4-20mA for SCADA. For monitoring inlet and outlet pH at different treatment stages.

ORP Monitoring for Disinfection

In STPs, treated water must be disinfected before discharge. ORP measurement confirms that the disinfectant (chlorine, ozone) is present at effective levels — it is a more reliable indicator of disinfection than chlorine dose alone.

Two independent relay outputs for disinfectant dosing control. Isolated 4-20mA output. For automatic chlorination and disinfection control in STP.
pH, ORP, conductivity, TDS, and temperature. For ETP/STP laboratory and inlet/outlet quality testing.

Conductivity & TDS Monitoring

Dual-limit conductivity control. Two relays. 4-20mA output. For monitoring and controlling dissolved solids in treated effluent.
TDS control in ppm. Dual relays. 4-20mA output. For monitoring total dissolved solids in effluent before discharge.

Key Applications

  • Industrial ETP — pH neutralisation control, conductivity monitoring
  • Municipal STP — pH control, ORP-based disinfection control
  • Common effluent treatment plants (CETP) — multi-parameter monitoring
  • Textile ETP — pH and conductivity control for colour removal processes
  • Pharmaceutical ETP — pH, conductivity, and TDS compliance monitoring
  • Electroplating ETP — heavy metal treatment pH control

Frequently Asked Questions

Why is pH control important in ETP?

Effluent must be neutralised to pH 6.5–8.5 as per CPCB norms before discharge. The 112pH dual-limit controller automates acid or alkali dosing to maintain pH within the permissible range continuously, eliminating manual monitoring gaps.

What is the permissible pH range for effluent discharge?

CPCB standards specify pH 6.5 to 8.5 for effluent discharged to surface water. The 112pH controller can be set to maintain pH automatically within this range with relay outputs for dosing control.

Which ORP instrument is used in STP disinfection?

Countronics ORP controllers monitor and control disinfectant levels in STP systems. ORP indicates how effectively chlorine or ozone is working. The controller activates or stops dosing automatically based on set ORP limits.

Is conductivity monitoring required for ETP compliance?

Yes. TDS and conductivity are key parameters in discharge compliance. The 160-COND and 160-TDS controllers monitor and control these automatically with relay outputs for treatment system activation.

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