The Challenge: Remote STP/WTP Monitoring
Sewage treatment plants and water treatment plants are often located in remote corners of buildings, industrial complexes, or office campuses - far from the main BMS or control room. Running cables to these locations requires expensive trenching, conduit, and installation work.
🏗️ Infrastructure Challenges
- STP located 500m to 2km away from main building
- Underground or rooftop locations requiring vertical cable runs
- No IT network infrastructure at STP site
- Trenching disrupts operations and landscaping
⚠️ Monitoring Gaps
- Manual checks lead to delayed fault detection
- Overflow/underflow conditions unnoticed until too late
- No real-time pH, flow, or level visibility
- Compliance reporting requires manual logs
The Solution: Wireless Modbus Connectivity
Link485 wireless Modbus gateways connect your STP/WTP sensors directly to the cloud or your existing BMS using LoRa (up to 2km) or 4G cellular - no cables required.
What You Can Monitor
Water Quality Parameters
- pH level (6.5-8.5 range for compliance)
- Turbidity (NTU)
- Dissolved Oxygen (DO) for aerobic treatment
- Total Dissolved Solids (TDS)
- Chlorine residual (for disinfection)
Flow & Level
- Inlet flow rate (m³/hr)
- Outlet flow rate
- Tank level (aeration, settling, storage)
- Sump level for pump control
- Overflow detection
Equipment Status
- Pump status (ON/OFF, runtime hours)
- Blower status for aeration
- Dosing pump for chemicals
- UV disinfection system status
- Motor current and overload protection
Common Modbus Registers for STP Equipment
// pH Meter (Typical Modbus Registers)
Holding Register 40001: pH Value (7.2 = 720)
Holding Register 40002: Temperature
Input Register 30001: Alarm Status (0=OK, 1=Alarm)
// Flow Meter
Holding Register 40101: Instantaneous Flow (L/min)
Holding Register 40102: Totalizer (m³)
Holding Register 40103: Flow Rate (m³/hr)
// Level Sensor
Holding Register 40201: Level (mm or %)
Input Register 30201: High Level Alarm
Input Register 30202: Low Level Alarm
// Pump Controller
Coil 00001: Pump Start/Stop (1=ON, 0=OFF)
Input Register 30301: Runtime Hours
Input Register 30302: Motor Current (Amps)
Wiring Diagram
Connect RS-485 A/B terminals from pH meter, flow meter, level sensor, and pump controller to the Link485 Zero/4G unit. The gateway transmits data wirelessly to the cloud or local BMS.
Step-by-Step Configuration
Connect RS-485 Devices
Wire all STP Modbus devices to the Link485 gateway using daisy-chain topology. Ensure proper 120Ω termination at both ends.
Power the Gateway
Link485 runs on 12-24V DC or PoE. Use existing STP panel power or a separate adapter.
Configure Wireless
Link485 Zero auto-pairs with the base station. Link485 4G uses pre-configured SIM - just power on.
Map Modbus Registers
Use Link485 Cloud to configure which registers to poll (pH, flow, level, pump status) and set polling intervals.
Set Alerts
Configure SMS/email/WhatsApp alerts for high pH, low flow, high level, or pump failures.
Integrate with BMS
Use Modbus TCP, REST API, or MQTT to forward data to your existing BMS or SCADA system.
Case Study: Office Campus Remote STP
120,000 sq ft Office Campus - Remote STP Monitoring
A corporate office campus in Pune had an STP located 800 meters from the main facility management office. Running cables would have required digging through landscaped areas and parking lots, which would be costly and disruptive.
"Link485 Zero connected our remote STP in 2 hours. We avoided expensive cable installation and now get real-time alerts on our phones when pH goes out of range. No more manual checks." — Facility Manager, Corporate Office