Cl-100 Chloride Ion-Selective Electrode

Overview

The Cl-100 is a precision ion-selective electrode specifically designed for measuring chloride (Cl⁻) concentration in water and wastewater. This reliable sensor is essential for monitoring salt content, corrosion potential, and water quality in municipal water systems, industrial processes, and environmental applications.

Key Features

• High Selectivity: Specifically designed for chloride ion detection
• Wide Range: Measures from 1.8 to 35,500 mg/L (ppm)
• Digital Output: RS485 Modbus RTU for seamless integration with SCADA and IoT systems
• Fast Response: Results within 30 seconds
• Automatic Temperature Compensation: Integrated PT1000 sensor for accurate readings
• Direct Connection: Connect directly to computer or PLC without additional instrumentation
• High Protection: IP68 waterproof rating ensures reliable operation

Applications

• Municipal drinking water monitoring
• Wastewater treatment plants
• Seawater and brackish water analysis
• Cooling tower water treatment
• Boiler feedwater monitoring
• Food and beverage processing
• Pharmaceutical manufacturing
• Concrete corrosion assessment
• Environmental monitoring
• Aquaculture systems

Technical Specifications

The Cl-100 delivers precise chloride measurements from 1.8 to 35,500 mg/L with automatic temperature compensation via the integrated PT1000 sensor. The silver chloride membrane provides excellent selectivity for chloride ions in complex water matrices, from freshwater to full-strength seawater (~19,400 mg/L Cl⁻).

The fast response time of less than 30 seconds enables real-time monitoring and rapid process adjustments. The wide measurement range spans from trace-level freshwater monitoring to concentrated brine solutions.

Chloride in Water Systems

Chloride (Cl⁻) is one of the most common anions in natural water. Sources include:

• Natural dissolution: Halite (rock salt), sylvite, and other evaporite minerals
• Seawater intrusion: Coastal aquifers affected by saltwater ingress
• Road deicing: Rock salt and calcium chloride from winter maintenance
• Industrial discharge: Chemical manufacturing, oil and gas produced water
• Wastewater effluent: Human waste, water softener regeneration brine
• Agricultural practices: Irrigation return flow, potash fertilizers

Chloride Concentration Reference Values

Regulatory Standards:

Application	Chloride Level
US EPA secondary limit (drinking water)	250 mg/L
EU Directive (drinking water)	250 mg/L
WHO guideline	No health-based limit; 250 mg/L taste threshold
Freshwater aquatic life	< 230 mg/L (chronic), < 860 mg/L (acute)
Irrigation water (sensitive crops)	< 140 mg/L
Concrete mix water (EN 1008)	< 500-1,000 mg/L

Natural Water Ranges:

• Pristine freshwater: 1 - 20 mg/L Cl⁻
• Typical river water: 10 - 100 mg/L Cl⁻
• Brackish water: 1,000 - 10,000 mg/L Cl⁻
• Seawater: ~19,400 mg/L Cl⁻
• Brine: > 35,000 mg/L Cl⁻

Corrosion Monitoring Applications

Chloride is the primary driver of pitting corrosion in stainless steel and reinforced concrete:

Water Distribution Systems:

• Monitor chloride-to-sulfate mass ratio (CSMR) - values > 0.5 increase lead release from solder
• Track seasonal changes from road salt runoff entering source water
• Detect saltwater intrusion in coastal wellfields

Cooling Tower Water:

• Chloride concentrates during evaporative cooling (cycles of concentration)
• High chloride accelerates corrosion of heat exchangers and condenser tubes
• Monitor blowdown to maintain chloride below equipment tolerance limits

Concrete and Infrastructure:

• Chloride ingress causes rebar corrosion and structural degradation
• Critical threshold: 0.2-0.4% Cl⁻ by cement weight triggers corrosion initiation
• Monitor concrete pore water in bridges, parking structures, marine infrastructure

Aquaculture and Salinity Applications

Chloride is the dominant anion in salinity measurement:

Marine/Brackish Aquaculture:

• Monitor salinity stability in shrimp ponds and fish tanks
• Detect freshwater intrusion or evaporative concentration
• Track salinity gradients in estuarine systems
• Verify salt mixing in inland saline aquaculture

Freshwater Aquaculture:

• Low-level salt addition (1-3 g/L NaCl) reduces nitrite toxicity in fish
• Monitor chloride-to-nitrite ratio for fish health management
• Detect contamination from salt runoff or groundwater intrusion

Salinity Relationship:

• Salinity (ppt) ≈ Chloride (mg/L) × 0.0018 (approximation for NaCl-dominated waters)
• Seawater: ~35 ppt salinity ≈ 19,400 mg/L Cl⁻

Interference Factors

The Cl-100 silver chloride membrane is selective for chloride, but users should be aware of:

• Bromide (Br⁻): Cross-sensitivity exists; significant in seawater or brominated water systems
• Iodide (I⁻): Strong interference at concentrations above 0.1× the chloride level
• Sulfide (S²⁻): Can poison the membrane surface - avoid in anaerobic environments or pre-treat samples
• Cyanide (CN⁻): Interferes at high concentrations (industrial applications)

For most freshwater, drinking water, and aquaculture applications, these interferences are negligible.

Installation and Calibration

Positioning: Install in a representative flow area with consistent water contact. For distribution systems, install after any chemical injection points. For aquaculture, install in the main circulation path away from freshwater inlets.

Calibration: Two-point calibration using NaCl standard solutions:

• Freshwater applications: 10 mg/L and 250 mg/L standards
• Brackish/marine applications: 1,000 mg/L and 20,000 mg/L standards
• Recalibrate every 2-4 weeks depending on fouling conditions

Maintenance: Clean the membrane surface monthly with dilute HNO3 or a soft brush to remove deposits. Rinse thoroughly with deionized water. The silver chloride membrane typically lasts 12+ months under normal conditions.

Connectivity and Integration

The Cl-100 supports dual output for flexible system integration:

RS485 Modbus RTU:

• Connect to Agrinovo Omni Genesis or Exodus controllers
• Multi-drop bus networking (up to 32 sensors per bus)
• Standard Modbus registers for chloride concentration and temperature
• Compatible with SCADA, PLC, and IoT gateway systems

RS485 Modbus RTU Output:

• Direct connection to traditional controllers and data loggers
• Scalable output range mapped to measurement range
• Ideal for blowdown control, dosing systems, or alarm triggers

IoT Integration:

• Pair with Omni Genesis/Exodus for cloud-based chloride monitoring
• Set automated alerts for threshold exceedances
• Historical data logging for trend analysis and regulatory reporting
• Integrate with valve controls for automated blowdown or freshwater addition

Complementary Monitoring

For comprehensive water quality, pair the Cl-100 with:

• EC sensor (EC-100): Conductivity correlates with total dissolved solids including chloride
• Na-100: Sodium and chloride together characterize NaCl-dominated salinity
• pH sensor (PH-100): pH affects corrosion rates in combination with chloride
• ORP sensor (ORP-100): Oxidation potential plus chloride indicates corrosion risk
• NO2-100: Chloride-to-nitrite ratio management in freshwater aquaculture