1、 Industry analysis background

The Importance of Ammonia Nitrogen Monitoring

Ammonia nitrogen (NH3-N) is an important indicator reflecting the degree of nitrogen-containing organic pollution and self purification status of water bodies. It is widely present in domestic sewage, industrial wastewater (fertilizers, coking, pharmaceuticals, etc.), and agricultural non-point source pollution. Excessive ammonia nitrogen can lead to eutrophication of water bodies, fish poisoning, and even death. Therefore, environmental regulations have strict limits on its discharge concentration (such as the Class A standard of ≤ 5 mg/L in the "Pollutant Discharge Standards for Urban Sewage Treatment Plants").

　　1.2 Ammonia nitrogen water quality automatic analyzerThe current application status

With the advancement of smart water management and online monitoring systems for pollution sources, ammonia nitrogen water quality automatic analyzers have become one of the online monitoring equipment for environmental protection departments, water operation enterprises, and industrial enterprises. Common measurement methods include:

　　Nessler's reagent spectrophotometric method(National standard HJ 535-2009)

　　Salicylic acid spectrophotometric method(HJ 536-2009)

　　electrode method(Ammonia sensitive electrode)

These devices can achieve continuous and real-time monitoring, but strict implementation is necessary to ensure accurate and compliant dataperiodic calibrationandScientific maintenance.

1.3 Industry Pain Points

　　data driftReagent aging, light source attenuation, and pipeline contamination can cause measurement results to deviate from the true values.

　　Lack of timely maintenanceEasy to cause false positives and omissions, affecting supervision and corporate reputation.

　　Calibration is not standardizedSome units use unqualified standard solutions or omit multi-point calibration, which reduces data reliability.

2、 Calibration points

Calibration is the core link to ensure the accuracy and stability of ammonia nitrogen analyzer measurement, and should be carried out in accordance with national/industry standards (such as HJ 355-2019 "Technical Specification for Operation of Online Monitoring System for Water Pollution Sources").

2.1 Calibration Classification and Cycle

calibration type	purpose	Suggested cycle	Applicable scenarios
zero point calibration（Zero Calibration）	Determine the instrument output signal when there is no ammonia nitrogen	Daily or every startup	Eliminate baseline drift
Range calibration（Span Calibration）	Establish a correspondence between known concentrations and signals	Weekly or monthly (depending on usage)	Ensure accurate linear range
Multi point calibration（Multi-point Calibration）	Improve full range accuracy	Quarterly or after equipment maintenance	High demand occasions (regulatory comparison)

2.2 Calibration operation steps (taking spectrophotometry as an example)

　　Prepare standard solution​

Prepare at least 3 concentration points (zero point, midpoint, and full-scale point) using certified reference materials (CRM).

The solution should be stored away from light within its expiration date to prevent volatilization or contamination.

　　Equipment preheating and stability​

Preheat the machine for at least 30 minutes and confirm that the temperature of the reaction tank and the light source are stable.

　　zero point calibration​

Inject a blank solution without ammonia nitrogen, run the measurement program, record the absorbance or signal value, and set it to 0 mg/L.

　　Range calibration​

Inject standard solutions of different concentrations in sequence, record the corresponding signal values, and fit the standard curve (linear correlation coefficient R ² ≥ 0.999).

　　Calibration verification​

Use another standard solution (not within the calibration curve) for verification, with an error of ≤± 5% (as per standard requirements).

　　Record and Archive​

Complete record of calibration date, operator, batch number of standard solution, environmental conditions, calibration curve equation, and verification results.

2.3 Precautions

Before calibration, check the expiration date of the reagent and the cleanliness of the pipeline, and replace the reagent if necessary.

The electrode method equipment needs to undergo electrode activation and slope inspection first.

When the ambient temperature fluctuates greatly, temperature compensation calibration should be performed.

3、 Key points of daily maintenance

Good maintenance can extend equipment lifespan, reduce failure rates, and ensure continuous and reliable monitoring data.

3.1 Daily Maintenance

　　Check the operating statusConfirm that the sampling pump, injection valve, and reaction tank are stirring normally without any abnormal noise.

　　Observe the reagent liquid levelTimely supplement insufficient reagents to avoid air traffic control operation.

　　View data trendsPay attention to whether there are sudden changes or continuous drift, and analyze the reasons in a timely manner.

3.2 Weekly maintenance

　　Pipeline flushingRinse the sampling and reagent pipelines with deionized water or dilute acid/alkaline solution to prevent crystallization or biofilm adhesion.

　　Colorimetric dish cleaningWipe the optical window with a soft dust-free cloth to avoid damaging the coating with organic solvents.

　　Zero point inspectionPerform a zero calibration to confirm baseline stability.

3.3 Monthly maintenance

　　Replace consumablesSuch as pump tubing, sealing rings, filter membranes, electrode membranes, etc.

　　Deep cleaning reaction tankAfter disassembly, use neutral detergent to ultrasonically clean and remove sediment.

　　Check the circuit and temperature controlEnsure that the heater and temperature control module are working properly.

3.4 Quarterly/Annual Maintenance

　　Comprehensive calibrationPerform multi-point calibration and record.

　　Performance verificationCompare with laboratory manual analysis method (relative error ≤ ± 10%).

　　Software and firmware updatesKeep the data collection and analysis functions up-to-date.

3.5 Maintenance under special circumstances

　　Long term shutdownDrain the reagent pipeline and reaction tank to prevent corrosion or microbial growth.

　　High pollution water sample impactIncrease the frequency of rinsing and replace all reagent batches if necessary.

4、 Common Problems and Countermeasures

problem	Possible reasons	Solution measures
Data consistently high	Reagent contamination, dirty colorimetric dishes, and standard curve drift	Replace reagents, clean colorimetric dishes, recalibrate
Low or zero data	Sampling pump failure, pipeline blockage, electrode failure	Check pump pressure, unclog pipelines, activate or replace electrodes
Signal instability	Environmental temperature fluctuations and aging of light sources	Install a constant temperature device and replace the light source
Calibration failed	Standard solution failure, instrument instability	Use new standard solution and extend preheating time

V. Conclusion

As the core equipment for online monitoring of water environment, the ammonia nitrogen water quality automatic analyzer directly affects the scientific nature of environmental supervision and the compliance level of enterprises in terms of data quality.calibrationIt is a 'fixed disk star' that ensures measurement accuracy,routine maintenanceIt is the 'moat' that ensures the long-term stable operation of the equipment.

The industry should:

Establish standardized operating procedures (SOP) and traceable record system;

Strengthen the training of operation and maintenance personnel to enhance their ability to judge and handle abnormal situations;

Introducing remote monitoring and intelligent diagnostic systems to achieve predictive maintenance and reduce manual inspection costs.

Only willStandardized calibrationandFine maintenanceOnly by covering the entire lifecycle of the equipment can the technical value of ammonia nitrogen analyzers be fully utilized in water quality protection.