Against the backdrop of deep integration between Industrial Internet of Things (IIoT) technology and digital ecosystem environmental supervision, the automatic monitoring of stationary pollution sources has become a hard compliance baseline for industrial project landing and operation. For system integrators, IoT solution providers, and environmental engineering contractors, precisely identifying compliance boundaries and meeting the field-end construction requirements of specific industries and technical specifications are core to ensuring that projects smoothly pass environmental protection self-acceptance and grid connection with government platforms.

Environmental regulatory policies clearly define the "Ten Criteria" under which units must be included in the list of key pollutant discharging units and forcefully installed with automatic monitoring equipment. At the same time, strict restrictions are placed on monitoring parameters for water and atmospheric environments, data transmission standards (HJ 212 protocol), and grid connection timelines. This article will adopt the technical perspective of B2B engineering contractors and integrators to deeply analyze these mandatory criteria, system architectures, and key selection points.

Regulatory Mandatory Criteria: "Ten Criteria" and Deadline Requirements for Forceful Installation of Automatic Monitoring Equipment

According to the regulations on the administration of the list of pollutant discharging units and the monitoring specifications of regional ecological and environmental authorities, any pollutant discharging unit that meets the screening conditions for key pollutant discharging units of water and atmospheric environments in the "Administrative Regulations on the List of Key Pollutant Discharging Units (Trial)" (Huan Ban Jian Ce [2017] No. 86), or meets one of the following ten criteria, shall be included in the list of key pollutant discharging units of water environment or atmospheric environment within its administrative region, and must forcefully install automatic monitoring equipment:

Water Environment and Sensitive Area Mandatory Installation Criteria (Criteria 1 to 5)

• (1) The average daily volume of wastewater discharged externally is greater than or equal to 100 cubic meters;

• (2) Wastewater is discharged directly into rivers and lakes within water functional zones such as water source protection areas and drinking water source areas;

• (3) Located within sensitive areas such as quasi-protection zones of surface-type drinking water sources and nature reserves, where wastewater is discharged directly into the environment;

• (4) Industrial enterprises directly discharging into the sea and urban sewage treatment plants in various coastal cities;

• (5) Nitrogen-related key industry enterprises that discharge pollutants directly into the sea or into rivers flowing into the sea.

Atmospheric Environment and Stationary Source Mandatory Installation Criteria (Criteria 6 to 9)

• (6) The height of the exhaust stack is greater than or equal to 45 meters, or the equivalent internal diameter is greater than or equal to 1 meter;

• (7) Coal-fired boilers of 20 tons and above, or industrial kilns or various types of incinerators with an exhaust volume equivalent to coal-fired boilers of 20 tons and above;

• (8) Specific heavily polluting and high-energy-consuming kilns: including cupolas, glass melting furnaces, brick and tile sintering kilns using coal and coal gangue as fuel, refractory material roasting kilns (except electric kilns), carbon baking (calcining) furnaces (kilns), lime kilns, chromium salt roasting kilns, phosphorus chemical roasting kilns, ferroalloy submerged arc furnaces and refining furnaces, etc.;

• (9) Stationary emission sources with a volatile organic compounds (VOCs) emission rate from the exhaust stack (including the equivalent emission rate of equivalent exhaust stacks) greater than 0.5 kg/hour or an exhaust volume greater than 10,000 cubic meters/hour.

Catch-all Clause, Allocation Proportions, and Construction Deadlines (Criterion 10)

• (10) Other situations that the ecological and environmental competent authority believes should be included in the list of key pollutant discharging units.

The ecological and environmental competent authorities of each city shall determine the list of key pollutant discharging units within their administrative regions before the end of March each year. The total amount of pollutant discharge from key pollutant discharging units shall not be lower than 80% of the total industrial pollutant discharge in the administrative region. According to regulations, key pollutant discharging units shall complete the installation, debugging, self-acceptance of automatic monitoring equipment **within 6 months after the disclosure of the list**, and connect to the monitoring platform of the ecological and environmental competent authority.

Previously, pollutant discharging units listed as key pollution sources by environmental protection administrative competent authorities at or above the municipal (district) level, or key pollutant discharging units located in environmentally sensitive areas, were required to install online monitoring instruments for major pollutants such as TOC, COD, and pH, as well as sewage flowmeters and operation recorders for pollution treatment facilities. For universal pollutant discharging units with a daily wastewater discharge volume above 100 tons or a daily Chemical Oxygen Demand discharge above 30 kilograms, they were also required to at least install sewage flowmeters and operation recorders for pollution treatment facilities.

Monitoring Items Mandatory Matching Table: Compliance Parameter Specifications for Water Quality and Flue Gas

When planning field-end technical solutions, system integrators must strictly match statutory monitoring factors and parameter metrics based on the category of the pollutant discharging unit (water environment, atmospheric environment, or VOCs key source):

1. Monitoring Requirements for Water Environment Key Pollutant Discharging Units

Chemical Oxygen Demand (COD) and Ammonia Nitrogen must be monitored as pollutants, alongside wastewater flow and pH as two parameters. Among them, centralized sewage treatment facilities and enterprises in nitrogen and phosphorus key emission industries stipulated by the Ministry of Ecology and Environment **must additionally monitor Total Nitrogen and Total Phosphorus as two pollutants**.

2. Monitoring Requirements for Atmospheric Environment Key Pollutant Discharging Units

Particulate matter, Sulfur Dioxide, and Nitrogen Oxides must be monitored as three pollutants, alongside five flue gas parameters: flue gas oxygen content, flow velocity, flow rate, temperature, and humidity. Among them, municipal solid waste and hazardous waste (including medical waste) incinerators must also monitor Carbon Monoxide and Hydrogen Chloride; the dust removal system of the ironmaking blast furnace cast house and the stock house dust removal system in the iron and steel industry, and the grate cooler (kiln hood) in the cement industry can be exempted from monitoring Sulfur Dioxide and Nitrogen Oxides; those using natural gas as fuel can temporarily bypass the monitoring of Sulfur Dioxide and particulate matter.

3. Monitoring Requirements for Volatile Organic Compounds Key Emission Sources among Atmospheric Environment Key Pollutant Discharging Units

VOCs (Non-Methane Hydrocarbons) must be monitored alongside five flue gas parameters: flue gas oxygen content, flow velocity, flow rate, temperature, and humidity. Among them, where other characteristic pollutants are stipulated in emission standards, the corresponding characteristic pollutants must also be monitored.

System Integrator Perspective: Systemic Architecture of Outlet Automated Monitoring Engineering

Online water quality monitoring systems and flue gas continuous emission monitoring systems target online analytical instruments and environmental compliance networking requirements as their service goals, taking the provision of representative, timely, and reliable sample information as their core mission. They utilize automatic control technology, computer technology, and corresponding software to compose a complete system. These sub-systems are both independent in architecture and highly collaborative, ensuring continuous and reliable operation of the entire online automatic monitoring system.

1. Six Sub-systems Architecture of Online Water Quality Automatic Monitoring System

• Sampling System: Configured with automated water pumps, pipelines, and control valves, responsible for stably extracting representative water samples from discharge outlets.

• Pre-treatment System: Performs physical filtration, silt backwashing, defoaming, and other physical preparations to prevent high turbidity and high suspended solids in industrial wastewater from damaging precision backend analytical instruments.

• Online Monitoring Analytical Instruments: The calculation and measurement core of the system, including digital and wet chemical analytical instruments for COD, Ammonia Nitrogen, Total Nitrogen, Total Phosphorus, pH value, TOC, etc.

• Data Acquisition and Control System: Usually composed of a PLC or field-end intelligent gateway, controlling sampling and cleaning logic, and converging sensor signals.

• Data Processing and Transmission System: Responsible for converting and formatting original signals into national standard transmission protocol packets.

• Remote Data Management Center: The Environmental Protection Bureau monitoring platform or enterprise digital center, achieving cross-regional data convergence.

2. Screening of Major Exhaust Stacks and Fugitive Emission Collection Engineering

The discharge outlets where key pollutant discharging units must install automatic monitoring equipment include: major wastewater discharge outlets and organized exhaust gas stacks screened according to relevant industry application and issuance technical specifications for pollutant discharge permits, self-monitoring technical guidelines, emission standards; discharge outlets specified in pollutant discharge permits that must implement automatic monitoring for units already issued with pollutant discharge permits; where it remains difficult to determine the discharge outlets for implementing automatic monitoring after screening according to the first two items, a technical scheme for installing automatic monitoring at discharge outlets can be formulated through a "One Factory, One Strategy" approach based on expert demonstration. The technical scheme must ensure that the annual emission volume of pollutants from the discharge outlets selected for automatic monitoring is not less than 80% of the total organized annual emission volume of that pollutant.

For complex plant sites, **fugitive emission exhaust gas should be collected and converted into organized emissions**. For areas or processes with dense small exhaust stacks, uniform collection and treatment measures should be constructed to discharge through a single exhaust stack, and automatic monitoring equipment must be installed. This serves as the standard modification path for integrators during system pipeline design.

Environmental Compliance Project Selection: YEXSENSOR Industrial-Grade Digital Monitoring Components

To address project bidding and system compatibility requirements, YEXSENSOR (Yexin) provides a complete range of digital sensors and data convergence data logger hardware for system integrators and environmental engineering contractors, adapting to various highly corrosive and highly polluted industrial fields:

Selection Guide and System Integration Considerations

When building industrial stationary pollution source online automatic monitoring projects, engineering integrators must plan the following technical details carefully during the solution design stage to ensure the long-term authenticity and accuracy of operational data and smooth grid connection:

1. Compliance of Data Transmission Protocol and Dynamic Control

Automatic monitoring equipment must comply with relevant national regulations concerning environmental monitoring and measuring instrument manufacturing. Acquisition and transmission must comply with the data transmission standard for automatic pollution source monitoring (HJ 212). During selection and integration, the field-end data logger (such as YEX-DAC-G2) must not only stably upload mean value data of monitored items, but must also support uploading operational states and working parameters of the equipment that affect data quality to the automatic pollution source monitoring platform to achieve remote dynamic control.

2. Specifications for Video Integration inside Station Houses and Front-end Outlets

According to construction technical specification standards, video monitoring facilities must be forcefully installed inside the automatic monitoring station house and at the monitoring sampling outlet. System integrators need to align and synchronize video streams or captured images with the data acquisition time stamp of the data logger, so that environmental enforcement departments can retrieve video footage to reconstruct actual field working conditions when data anomalies (such as exceedances, sharp mutations, or disconnections) are detected.

3. Modification of Physical Points and Applications for Exemption from Installation

Various municipalities have clarified situations where units can be exempted from installing automatic monitoring equipment, namely: where the emission concentration of pollutants is lower than the detection limit of existing automatic monitoring equipment, or where the discharge outlet does not meet the installation requirements of measurement points specified in technical specifications and cannot be modified. If the industrial site objectively cannot create a sampling section that conforms to technical specifications, integrators should assist the key pollutant discharging unit in providing third-party monitoring reports, expert demonstration opinions, and other evidentiary materials to the municipal ecological and environmental competent authority for review and confirmation, after which the unit can switch to regular manual self-monitoring, and local environmental departments will carry out supervisory monitoring.

Engineering Contractors and System Integrators Common FAQ

Q1: If an enterprise's average daily wastewater discharge is exactly around 95 cubic meters, can it avoid being included in the list of key pollutant discharging units and skip installing online monitoring?

A: A double check is mandatory. Although 95 cubic meters does not reach the general metric of "average daily volume of wastewater discharged externally greater than or equal to 100 cubic meters", it is still necessary to check whether the enterprise fits the other nine criteria. For instance: Is the discharge outlet directly releasing wastewater into water functional zones like water source protection areas and drinking water source areas? Is it located within sensitive areas like nature reserves? Or does it belong to an industrial enterprise directly discharging into the sea in a coastal city? As long as it meets one of the ten criteria, or meets the screening conditions of Huan Ban Jian Ce [2017] No. 86, it must be forcefully included in the list and installed with online monitoring.

Q2: After a key pollutant discharging unit's automatic monitoring equipment passes self-acceptance and applies for grid connection, when does the data start acting as the basis for environmental enforcement?

A: After installation is complete, the pollutant discharging unit shall carry out debugging and trial operation according to relevant technical specifications, and organize and complete the self-acceptance of automatic monitoring equipment construction installation and technical performance indicators before grid connection. After self-acceptance is qualified, the pollutant discharging unit applies for grid connection to the municipal ecological and environmental competent authority. The data after grid connection is valid data and can officially serve as the basis for environmental enforcement and management. The pollutant discharging unit can carry out routine operation and maintenance itself or commission a third-party operations company.

Q3: Among atmospheric environment key pollutant discharging units, what special requirements apply to the monitoring parameters of municipal waste incinerators and hazardous waste incinerators?

A: Universal atmospheric environment key sources only need to monitor particulate matter, sulfur dioxide, nitrogen oxides, and five flue gas parameters (oxygen content, flow velocity, flow rate, temperature, humidity). However, because the composition of municipal solid waste and hazardous waste (including medical waste) is highly complex and extremely prone to generating incomplete combustion products and acidic gases during incineration, the regulations emphasize that such incinerators must also forcefully monitor Carbon Monoxide (CO) and Hydrogen Chloride (HCl) as two special pollutants.

Q4: There are many small exhaust stacks scattering fugitive emissions inside the plant area. How should fugitive emissions be treated in integration engineering to conform to automatic monitoring specifications?

A: Regulations require that "fugitive emission exhaust gas should be collected and converted into organized emissions". For areas or processes with dense small exhaust stacks, the standard engineering approach for integrators is to construct unified negative-pressure collection and purification treatment measures to gather and direct the scattered exhaust gas toward the same standard exhaust stack for discharge, and install automatic monitoring equipment on that major exhaust stack. By formulating an installation technical scheme via a "One Factory, One Strategy" approach, ensure that the annual emission volume of pollutants from the discharge outlets selected for automatic monitoring is not less than 80% of the total organized annual emission volume of that pollutant.

Q5: Which industries belong to the "nitrogen and phosphorus key emission industries" that require mandatory additional monitoring of Total Nitrogen (TN) and Total Phosphorus (TP)?

A: In addition to centralized sewage treatment facilities, any enterprise falling under the scope of the Ministry of Ecology and Environment's "Notice on Strengthening the Prevention and Control of Nitrogen and Phosphorus Pollution from Stationary Pollution Sources" (Huan Shui Ti [2018] No. 16) belongs to this category. It mainly covers chemical raw materials and chemical product manufacturing (such as chemical fertilizers, inorganic phosphorus chemicals), pharmaceutical manufacturing, agricultural and sideline food processing, slaughtering and meat processing, leather tanning, electroplating, etc. When integrators undertake sewage outlet integration projects in these industries, the solution must include online analyzers for Total Nitrogen and Total Phosphorus.

Q6: In volatile organic compounds (VOCs) stationary source monitoring, what is the difference between monitoring "Non-Methane Hydrocarbons" and "characteristic pollutants"?

A: Key volatile organic compounds emission sources must monitor VOCs (expressed as Non-Methane Hydrocarbons, NMHC) and five flue gas parameters, which constitutes the baseline compliance item. However, if the industry emission standard to which the enterprise belongs (such as industry standards for pharmaceuticals, coatings, petroleum chemicals, etc.) explicitly stipulates other characteristic pollutants (such as benzene, toluene, xylene, formaldehyde, etc.), integrators must expand and add corresponding characteristic factor chromatography detection modules or exclusive sensors on top of the NMHC analyzer during selection.

Q7: If the environment at the industrial wastewater discharge outlet is extremely harsh, how can digital sensors avoid frequent damage and data breakpoints?

A: The key lies in the protection rating and automated cleaning design during selection. For direct immersion installation at major wastewater discharge outlets, digital sensors with an IP68 high protection rating and acid/alkali resistant materials (such as POM or titanium alloy) must be selected. Furthermore, integrators should program timed backwashing control sequences in the PLC or gateway, coordinating with hardware like YEX-S1-COD that comes standard with an optical self-cleaning brush. Through dual physical and pneumatic cleaning, probe surface scaling and bio-attachment are prevented, ensuring continuous and stable operation.

Q8: What specific equipment parameters are included in the "dynamic control" required by ecological and environmental competent authorities? How does data logger integration respond?

A: Dynamic control requires uploading not just final concentration values, but also working parameters that reflect the operational status of the analytical instruments. For instance: digestion temperature of the instrument, measurement range, current calibration coefficients, equipment fault codes, whether the device is currently measuring or in a cleaning/maintenance state, etc. The YEX-DAC-G2 data logger directly reads these status parameter registers inside YEXSENSOR digital intelligent sensors via the downlink RS485 bus, encapsulates them into standard HJ 212 protocol packets, and uploads them, ensuring that the field end fully conforms to dynamic supervision self-acceptance standards.

Conclusion

The standardized construction of automatic monitoring systems for stationary pollution sources is not only a compliance baseline for industrial owners to avoid environmental legal risks, but also a commercial core for system integrators and environmental contractors to demonstrate technical delivery capabilities. Whether it is the hard threshold of average daily wastewater exceeding 100 cubic meters, or stationary gas sources with a VOCs emission rate greater than 0.5 kg/hour, every single installation metric under the ten criteria carries strict legal traceability. Realizing complete systemic high-reliability operation covering "sampling, pre-treatment, analysis to data processing and storage" and passing national standard grid-connection self-acceptance is the final benchmark for successful project delivery.

By selecting the YEXSENSOR full series of digital intelligent water quality monitoring components (pH/COD/Ammonia Nitrogen/Flowmeters) and the supporting YEX-DAC-G2 environmental data acquisition and transmission instrument, system integrators can maximize simplification of backend hardware access complexity. Standard digital bus architecture, hardware-level optoelectronic isolation, a breakpoint resume flash memory mechanism, and protocol encapsulation fully compatible with HJ 212 standard dynamic control ensure the entire automatic monitoring field end possesses strong field anti-interference and lightning protection capabilities, while simultaneously achieving high synergy with the environmental department's monitoring platform. Under the new normal of digitalized and continuous environmental supervision, YEXSENSOR is committed to providing deterministic compliance product protection and technical support for global IoT solution providers and environmental engineering contractors.