Case Study | Chunye Complete Water Quality Monitoring Equipment Successfully Accepted at a Sewage Treatment Plant in Shaoyang

Project Background

The Shaoyang Sewage Treatment Plant mainly treats domestic sewage and a small volume of industrial wastewater from surrounding areas. The aging legacy monitoring system has been in operation for years and brought numerous challenges in operation and regulatory compliance, driving the plant to pursue comprehensive intelligent upgrading:

• The original COD and ammonia nitrogen analyzers suffered severe aging and heavy measurement drift, failing to stably connect to environmental supervision platforms, which brought risks of excess discharge reports and environmental penalties.

• Dissolved oxygen, sludge concentration in biochemical tanks and sludge level in sedimentation tanks were measured manually via periodic sampling. Data lag caused aeration and sludge return to be adjusted empirically, leading to high consumption of chemicals and electricity.

• No online instruments for pH, ORP, effluent residual chlorine and nitrate nitrogen; real-time data was unavailable for disinfection and biochemical process regulation.

• Most suppliers in the market can only provide separate sensors or analyzers rather than complete monitoring hardware. Incompatible communication protocols resulted in complicated later commissioning and after-sales service.

 Project Challenges

Combined with on-site working conditions and mandatory environmental supervision requirements, four core difficulties existed for project implementation:

1. Numerous monitoring points and diversified product requirements: 8 monitoring locations including influent channel, biochemical tank, secondary sedimentation tank and disinfection outlet. Over 10 indicators needed simultaneous monitoring: COD, ammonia nitrogen, total phosphorus, total nitrogen, DO, sludge concentration, sludge level, pH/ORP, nitrate nitrogen, residual chlorine. Most manufacturers can only supply single-category instruments with poor compatibility for complete system integration.

2. Harsh sewage environment: Heavy sediment and biomass adhesion inside biochemical and sedimentation tanks easily caused scaling and blockage on conventional sensors, resulting in data distortion within short periods. Frequent manual cleaning raised maintenance workload significantly.

3. Constraints for station and tank construction: Compact space inside the monitoring station; all tank mounting ports adopt standard G3/4 thread. Limited water depth at some points imposed strict limits on sensor installation height and distance from tank walls.

4. Strict requirements for environmental data communication: All monitoring data must be uploaded simultaneously to the plant central control system and municipal environmental supervision platform. Communication protocol incompatibility between old and new systems brought heavy joint commissioning workload. Continuous stable operation for 72 hours is mandatory for acceptance.

 Solutions

Targeting pain points and construction difficulties, Chunye Technology delivered a customized integrated complete water quality monitoring solution with self-developed full-series equipment, deployed in four categories: cabinet-mounted online analyzers, submersible digital sensors, industrial controllers and ultrasonic auxiliary devices.

① Cabinet-mounted Automatic Online Analyzers

• CODcr Online Water Quality Analyzer: Potassium dichromate spectrophotometry, suitable for high-concentration influent sewage. Supports 5-year data storage, dual protocol compatibility (HJ212 & Modbus) for environmental platform data uploading.

• Ammonia Nitrogen Online Analyzer: Salicylic acid spectrophotometry, measuring range 0–300 mg/L. Automatic calibration and reagent dosing, optimized for municipal sewage applications.

• Total Phosphorus & Total Nitrogen Online Analyzers: Fully automatic digestion and analysis for nitrogen & phosphorus indicators, fully meeting discharge standard monitoring requirements for sewage treatment plants.

② Industrial Online Controllers

• Online ORP Transmitter: Compact panel-mounted controller with 2 relay outputs and 4–20mA signal, for real-time oxidation-reduction potential measurement.

• Online pH Transmitter: Large display, 3 relay outputs and historical data storage. Matched with double-thread plastic shell electrode, withstand pressure 0.6 MPa, working temperature 0~80°C, applicable for rivers, sewage and pure water to stably monitor pH and ORP.

• Fluorescent Dissolved Oxygen Transmitter: Equipped with IP68 anti-corrosion digital DO sensor, range 0–20 mg/L, built-in NTC temperature compensation for biochemical tank aeration monitoring; no frequent membrane cap replacement required.

• Online Residual Chlorine Transmitter: Specially designed for disinfection processes, supports calibration, data storage and high/low alarm. Paired with constant potential electrode, measuring range 0–20 mg/L for tap water, sewage outlet and flow cell monitoring in swimming pools.

• UV Nitrate Nitrogen Monitor: Dual-wavelength UV reagent-free detection, sensor with automatic wiper self-cleaning, IP68 stainless steel housing, measuring range 0.1–100 mg/L for long-term nitrate monitoring in various water bodies.

• Sludge Concentration Transmitter: 135° infrared scattering principle; large-screen controller with multi-unit switching and 3 relay alarms. IP68 sensor with automatic wiper, range 0.01–50000 mg/L for suspended solids in sewage, pulp and mortar.

• Ultrasonic Sludge Interface Meter: Measuring range 0.2–12 m, dual output 4–20mA / RS485; IP68 stainless steel probe with blind zone ＜20 cm. Accurately identifies mud-water interface in sedimentation tanks to guide sludge return and discharge.

• Standardized construction specification: Sensors installed ≥5 cm above tank bottom; ultrasonic probes kept away from tank walls to avoid echo interference; layered pipeline layout inside station with independent waste liquid recovery.

• Unified communication commissioning: All devices equipped with Modbus RTU, completing one-time data interconnection for plant central control and environmental supervision dual platforms.

• Working-condition optimization design: Automatic wiper on sensors reduces manual cleaning frequency; low-reagent-consumption formula for analyzers to cut long-term operation & maintenance costs.

Project Acceptance

1. Hardware Installation Inspection

   Full verification of installation quality for T9000/T9001 analyzers, W-series controllers, CS-series sensors, ultrasonic sludge / level meters. Cable waterproofing, bracket fixing and pipeline anti-leakage all conform to specifications.
2. Precision & Stability Test

   72-hour continuous full-index testing with national standard solutions. Indication error and 24-hour drift of COD, ammonia nitrogen, DO, sludge concentration, nitrate nitrogen, residual chlorine and other instruments meet national standards. Self-cleaning wiper operates steadily without data drift.
3. Data Transmission Verification

   Simulated measurement, calibration and fault scenarios. Real-time readings, equipment alarms and historical records can be stably uploaded to central control and environmental platforms; Modbus and HJ212 communication maintain continuous connection without disconnection or data loss.
4. Overall Handover & Training

   Acceptance team verified complete equipment list, original manuals and spare parts, and the acceptance document was formally signed. After acceptance, Chunye technicians delivered on-site professional training for operation, calibration and troubleshooting for the operation & maintenance team. Long-term after-sales support including on-site calibration and spare parts replacement is available.