ACITEK's Online Dissolved Oxygen Meter

In recent years, with the continuous improvement of water quality management technology and level in water plants, online water quality monitoring system has been integrated as an emerging management method, triggering industry changes. With the help of advanced sensor technology and automation equipment, the system can monitor the quality of raw water, water production process and outgoing water in water plants 24 hours a day. From key indicators such as pH, turbidity to residual chlorine content, they can all be accurately measured, and data can be fed back in real time, which completely changes the lag and limitations of traditional manual sampling and monitoring. ​
After the online monitoring system is put into use, the water plant can capture subtle changes in water quality in a timely manner, quickly adjust the water production process, and ensure that the water quality is stable and meets the standards. This not only effectively improves the safety of water supply and ensures the health of residents' water use, but also greatly improves the operating efficiency of water plants and reduces labor costs and management difficulties. At present, the online water quality monitoring system has become an important measure for many water plants to optimize management. With the continuous iteration of technology, it is expected to be popularized in more water plants in the future, promoting the entire water supply industry to move towards intelligent and refined management, and building a solid line of defe

ACITEK G300 Online DO Transmitter + DO6800 High-temperature Dissolved Oxygen Electrode

1. Project Background
A fine chemical enterprise produces 50,000 tons of acrylate annually. Its reaction kettles operate at 80–120℃ and 0.6–1.0 MPa. Dissolved Oxygen (DO) must be strictly controlled within 0.5–1.5 mg/L. Excess DO causes side reactions and reduces product purity, while insufficient DO leads to incomplete chemical reaction and lower output.

The traditional polarographic electrodes suffered severe signal drift above 60℃, with membranes aging every 2–3 weeks. Frequent shutdown for calibration and replacement brought high maintenance costs and disrupted continuous production. The site adopted ACITEK G300 DO Transmitter + DO6800 High-temperature DO Electrode to solve the problems.



2. Product Specifications
ACITEK G300 Online DO Transmitter

Measuring range: 0.00–40.00 ppm, Accuracy: ±0.01 ppm
Working temperature: -10.0–130.0℃, automatic temperature compensation
Output: 4-20mA & Modbus RTU, compatible with DCS system
Protection class: IP65, explosion-proof design







ACITEK DO6800 High-temperature DO Electrode

Temperature resistance: 0–130℃, supports 130℃ SIP sterilization
Housing: 316L stainless steel, acid & alkali resistant
High-temperature resistant membrane, anti-aging and anti-fouling
Response time: t90 ≤ 60 s




3. Installation & Commissioning

Mounted on DN50 side port of reaction kettle, immersed 20–30 cm below liquid level, away from agitator and inlet to avoid bubble interference.
Shielded cabling to prevent electromagnetic interference.
Two-point calibration with oxygen-free water and air-saturated water. Stable performance lasts over 6 months after one calibration.
Linked with DCS: Automatic nitrogen purge when DO below set value; cut off nitrogen supply when DO exceeds limit.

4. Application Results (6-month operation)

Stable measurement: No signal drift at 120℃, DO fluctuation controlled within ±0.1 mg/L.
Low maintenance: Membrane service life extended from 2–3 weeks to 8–10 months. Calibration cycle reaches 6 months, maintenance workload reduced by over 70%.
Quality improvement: Acrylate purity rose from 99.2% to 99.7%, high-grade product rate increased by 12%.
Higher efficiency: Gas consumption cut by 18%. Shutdowns caused by DO faults were eliminated, with annual output increased by 2000 tons.
Durable performance: Continuous trouble-free operation for 180 days, no corrosion orscaling on electrode.

5. Customer Feedback
"This high-temperature DO monitoring solution perfectly solves our pain points of unstable reading and frequent maintenance. The G300 transmitter delivers reliable data and smooth communication. The DO6800 electrode works well under high temperature. It greatly guarantees our continuous production and product quality." — Manager Wang, Equipment Department

6. Applicable Scenarios

Chemical industry: High-temperature reaction kettles, polymerization & oxidation processes, high-temperature wastewater
Pharmaceutical industry: Fermenters with 121℃ SIP sterilization
Power industry: Boiler feed water and condensed water trace oxygen monitoring
Environmental protection: High-temperature industrial wastewater & leachate treatment

1. Product Application Overview
ACITEK G100-DO is a miniature DIN rail-mounted dissolved oxygen (DO) transmitter specially designed for industrial process water quality monitoring. With an ultra-narrow 12.5 mm modular housing, 4–20 mA active analog output, RS485 communication, 24 VDC power supply and integrated temperature measurement function, it perfectly solves the installation limitation of narrow control cabinets, compact fermenters and small-scale process monitoring stations. Matched with 12 mm diameter 316L stainless steel DO sensor (IP65 protection), it delivers fast response within 1 minute and stable long-term measurement, widely deployed in chemical, pharmaceutical, biotechnology, food & beverage, energy industries, industrial wastewater treatment and laboratory process analysis. The complete package includes DIN rail transmitter, stainless steel DO sensor, mounting fittings, signal cable, flow cell and operation manual, supporting OEM & ODM customized service for diversified on-site working conditionsacitekinst....

2. Industry-Specific Application Scenarios
2.1 Biotechnology & Pharmaceutical Fermentation
Biopharmaceutical and microbial fermentation processes require precise real-time dissolved oxygen control to guarantee strain reproduction, metabolite yield and drug purity.


Core application: Small & medium-sized bioreactors, seed culture tanks, cell culture lines.
Application advantages:

Ultra-thin 12.5 mm body allows centralized installation in dense PLC control cabinets with multi-channel parameter transmitters (pH, conductivity, DO) without cabinet space shortage.
Built-in manual calibration keys (K3/K4) support on-site one-point/two-point calibration without extra handheld calibrators; calibration cycle is recommended once every 3 months to sustain measurement accuracy.
Stainless steel 1.4435 sensor probe adapts to repeated SIP/CIP high-temperature sterilization sanitary working conditions, avoiding corrosion from culture medium and organic solvents.
4–20 mA signal connects to DCS/PLC to realize automatic linkage of stirring speed and aeration flow, stabilizing DO concentration in fermentation broth and improving production batch consistency.


Typical case: Antibiotic, amino acid, vaccine cell culture production lines.

2.2 Food & Beverage Production
Dissolved oxygen directly determines product flavor, shelf life and oxidation stability in food processing.


Core application: Beer/wine fermentation, pure water production, beverage filling pretreatment, dairy processing.
Working value:

Monitor low-level residual oxygen in finished water and beverage pipelines to suppress fat oxidation, color fading and flavor deterioration.
Fermentation tank online monitoring: control oxygen supply in yeast growth stage to avoid excessive DO causing off-flavor in finished wine.
Compact DIN rail design fits small beverage factory central control cabinets, realizing multi-point DO monitoring for multiple production lines with low overall investment cost.


Matching hardware: 12 mm stainless steel sanitary DO sensor with silicone sealing, compatible with food-grade fluid pipelines.

2.3 Chemical Industry Process Monitoring
Chemical synthesis, polymerization and fine chemical reactions are sensitive to dissolved oxygen to prevent invalid oxidation side reactions.


Application points: Chemical reaction kettles, solvent recovery systems, intermediate water circulation pipelines, fine chemical pilot test lines.
Product highlights for chemical sites:

4-wire system with 14–24 VDC wide voltage power supply, stable signal transmission under factory electromagnetic interference.
RS485 Modbus communication supports distributed networking, enabling centralized remote data collection of dozens of monitoring points.
Low-cost modular measurement station solution, ideal for small-batch pilot chemical workshops with limited cabinet space.



2.4 Energy & Power Industry Water Treatment
High dissolved oxygen in boiler feed water, cooling circulating water and thermal power sampling water will cause pipeline and equipment corrosion, shortening service life.


Core scenario: Thermal power plant condensate sampling rack, boiler deaerator outlet monitoring, cooling water circulation system.
On-site advantages:

Slim DIN rail transmitter can be densely arranged on sampling rack small-sized control boxes.
Synchronous measurement of dissolved oxygen and medium temperature, providing dual-parameter data for water chemical supervision.
4–20 mA analog signal uploads DO data to power plant monitoring system to trigger deaeration equipment linkage control.



2.5 Industrial Wastewater & Environmental Water Treatment
Aerobic and anaerobic biochemical tanks rely on precise DO adjustment to optimize activated sludge treatment efficiency and reduce aeration energy consumption.


Applications: Factory sewage treatment stations, small municipal wastewater aerobic tanks, discharge water quality monitoring wells.
Field performance:

IP65 stainless steel sensor probe resists sludge adhesion and weak corrosive wastewater medium.
Fast 1-minute response time timely reflects DO fluctuation in biochemical tanks to adjust fan operation frequency and cut power consumption.
Low maintenance cost, suitable for scattered small sewage treatment stations with limited operation manpower.



2.6 Laboratory & Pilot Test Equipment
Universities, R&D laboratories and pilot workshops have compact test equipment with limited installation space.


Usage scene: Laboratory bench bioreactors, small water quality test circulation devices, material oxidation test systems.
Laboratory advantages: Miniature transmitter saves laboratory control box space; simple manual calibration operation meets frequent experimental parameter calibration demands; one-year warranty and customizable OEM labels support laboratory self-developed test equipment matching.

3. Installation & System Application Modes
3.1 DIN Rail Central Cabinet Installation
The G100-DO transmitter adopts standard 35 mm DIN rail mounting, dozens of units can be side-by-side installed together with pH, conductivity transmitters inside narrow control cabinets, realizing multi-parameter centralized monitoring of the whole production line, which is the most mainstream application mode for medium and small factories.

3.2 Independent Small-Scale Monitoring Station
Matched with flow chamber, mounting bracket and cable, it forms a complete compact DO measuring station for single reactor, single pipeline or single wastewater tank independent monitoring, without large integrated analysis cabinet, greatly reducing equipment procurement and cabinet transformation cost.

3.3 PLC/DCS Automatic Control System Integration

Analog output: 4–20 mA active current signal accesses PLC analog module to realize closed-loop automatic control of aeration, stirring, deaeration equipment.
Digital communication: RS485 Modbus-RTU connects to industrial gateway, uploading DO & temperature data to upper computer, SCADA or cloud platform for remote real-time viewing and historical data recording.

4. Application Advantages Over Traditional Large DO Transmitters

Space-saving layout: Only 12.5 mm width, solving the installation bottleneck of narrow cabinets and compact equipment that large display transmitters cannot fit.
Cost-effective construction: Low unit price plus modular assembly reduces the total investment of multi-point monitoring stations, especially suitable for small factories and pilot projects.
Wide universal compatibility: One set of equipment covers biotech, food, chemical, energy and environmental protection industries; stainless steel sensor adapts to sanitary, corrosive and aqueous working conditions.
Easy on-site maintenance: Independent K3/K4 calibration buttons support field calibration without removing the transmitter from the cabinet; recommended quarterly calibration ensures long-term stable measurement.
Dual signal output: Simultaneous 4–20 mA analog and RS485 digital communication, compatible with both traditional PLC control and modern industrial internet remote monitoring systems.

5. Application Matching Notes

For sanitary fermentation and food production, select 1.4435 stainless steel sanitary DO sensor; for chemical wastewater, 316L stainless steel probe is recommended.
The transmitter body protection grade is IP20, so it must be installed inside closed control cabinets; the matched DO sensor reaches IP65 and can be directly inserted into pipelines or tanks.
Power supply range: 14–24 VDC 4-wire connection, avoid long-distance thin wire power supply to prevent voltage drop affecting measurement stability.
OEM/ODM customization is available for special industrial application requirements, including logo printing, cable length adjustment and flow chamber modification.

Updated Environmental Regulations Bring New Compliance Requirements for Wastewater Online Monitoring Equipment


With the official implementation of China’s HJ 212-2025 Technical Requirements for Data Transmission of Pollutant Automatic Monitoring System and the upcoming enforcement of the Ecological Environment Code, stricter supervision is being carried out on wastewater discharge monitoring. Regulators have raised higher standards for online water quality instruments used at wastewater outlets, including pH, dissolved oxygen and conductivity sensors. Factories in chemical, pharmaceutical, food & beverage industries, together with industrial wastewater treatment plants, are now entering a critical period to evaluate and upgrade their monitoring systems.

Core Updates in New Environmental Standards

Full data traceability to prevent distorted monitoring results Unique device identification codes are required for all field monitoring instruments during network access. Raw measurement data, calibration logs and equipment operation records must be stored for long-term review. Any modification to instrument parameters will be recorded automatically. Unauthorized devices cannot connect to official environmental monitoring platforms.
Higher standards for long-term measurement stability Wastewater usually contains sludge, weak acid, alkali and dissolved salts. Regulators demand sensors with reliable temperature compensation and low measurement drift. Sensors prone to corrosion, scaling and frequent deviation will be regarded as invalid monitoring equipment during official inspections.
Unified communication protocol for seamless data networking New standards standardize data interaction between sensors, transmitters and data collectors. Instruments shall support standard Modbus-RTU and stable 4–20mA analog signals. Outdated equipment with unstable signal output or incompatible communication cannot meet current compliance demands.

ACITEK Solutions for Regulatory Compliance
ACITEK offers a complete portfolio of water quality sensors and transmitters fully adapted to the latest environmental monitoring requirements: • AC580 series conductivity sensors, industrial pH electrodes and DO sensors feature built-in PT1000 temperature compensation. Wetted SS316L material provides anti-corrosion performance in complicated wastewater media. • G100 compact DIN rail transmitters support 4–20mA active output + RS485 Modbus dual signals. All parameter changes are logged automatically to meet traceability requirements. • Complete accessories including flow cells, immersion holders and mounting fittings comply with HJ installation & operation specifications.

Recommendations for End Users & System Integrators

For existing monitoring stations: Test sensor accuracy and signal stability in advance. Replace aging instruments in phases to avoid compliance risks.
For new wastewater treatment projects: Adopt integrated monitoring systems with both analog and digital communication to satisfy long-term regulatory demands.
Form standardized maintenance schedules, regularly clean and calibrate sensors and archive all calibration documents.

ACITEK provides professional technical support and customized online monitoring packages for wastewater discharge applications. If you need a complete solution for pH, DO and conductivity monitoring in wastewater projects, please contact our engineering team.

This paper presents three representative field application cases to verify the actual performance, economic benefits and technical advantages of ACITEK LDO Model 1 in seawater aquaculture, municipal wastewater treatment plant and coastal river nutrient monitoring projects.


Case 1: Seawater Industrial Mariculture Base Real-Time DO Control


1.1 Project Background


A large-scale coastal marine ranch in Fujian operates recirculating seawater breeding tanks for grouper and abalone, covering 12,000 m² breeding area.



Original monitoring scheme: Traditional polarographic dissolved oxygen electrodes
Pain points encountered:


Seawater contains high Cl⁻, algae and barnacle attachment; electrode membrane fouled within 7–10 days, data drifted severely;
Weekly membrane replacement, monthly electrolyte refilling, daily manual cleaning; 2 full-time maintenance staff required for 32 breeding tanks;
H₂S produced by residual bait decomposition poisoned polarographic electrodes, leading to invalid readings and delayed oxygen supply adjustment;
Without stable real-time DO data, aerators ran at full load all day, resulting in huge electricity waste; low DO at night caused occasional fish hypoxia mortality (annual loss over 180,000 RMB).






1.2 Solution Deployment


The project replaced all old electrodes with ACITEK LDO Model 1 seawater version dissolved oxygen sensors:



Installation: 1 probe per recirculation tank, installed on pipeline thread interface (standard thread compatible with existing tank fixtures); 10m matched sensor cable connected to ACITEK G800 controller;
Configuration: Factory pre-calibration, plug-and-play without on-site calibration; built-in automatic temperature compensation, immune to seawater temperature fluctuation 12–32°C;
Linkage control: Set DO threshold 5.0–7.5 mg/L; when DO <5.0 mg/L, system auto-starts aerators; when DO >7.5 mg/L, aerators reduce frequency or shut down.



1.3 On-Site Operation Results



Ultra-low maintenance workload

No consumables (membrane/electrolyte) needed. Only quarterly simple surface wiping of sensor cap required. The maintenance team cut staffing from 2 to 1 part-time worker, saving labor cost around 65,000 RMB annually. The sensor cap maintains 12-month service life covered by official warranty.
Strong seawater anti-interference performance

Not affected by high-concentration chloride, sulfide, residual feed organic matter and marine biofouling. Continuous 12-month immersion test showed no measurement drift, data accuracy kept ±0.05 ppm below 5 ppm as original specification.
Energy saving & mortality reduction

Precise aeration frequency regulation cut aeration power consumption by 22%. Night hypoxia incidents were completely eliminated; fish survival rate increased from 82% to 97%, reducing aquaculture economic loss by over 160,000 RMB each year.
Customer Feedback

"The ACITEK LDO sensor solves our long-standing seawater measurement trouble. Stable readings without frequent replacement parts greatly lower our operating cost, and scientific oxygen control significantly improved breeding output." — Farm Technical Director



Case 2: Municipal Wastewater Plant Secondary Biochemical Treatment Tank Monitoring


2.1 Project Background


A medium-sized municipal sewage treatment plant in Jiangsu adopts AAO secondary treatment process, daily treatment capacity 40,000 tons. Dissolved oxygen in aerobic tank is the core parameter to balance nitrification efficiency and aeration energy consumption.



Previous problem: Polarographic DO probes easily blocked by activated sludge foam; data fluctuated widely, unable to support automatic variable-frequency blower control; operators relied on manual sampling calibration twice per week, aerators operated with excessive air supply, high power consumption.



2.2 Project Scheme



Deploy 8 sets of ACITEK LDO Model 1 probes evenly distributed in aerobic biochemical tank;
Probe specification: 155mm length, 28.25mm diameter, Noryl corrosion-resistant body, maximum 3.5 bar pressure resistance adapting to tank immersion depth;
Data transmission: Max 100m transmission distance to G800 control unit, realizing real-time DO curve display and blower linkage regulation.









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Sensor Installed in Aeration Tank









2.3 Application Benefits



Stable measurement without flow demand

ACITEK LDO technology does not consume oxygen during detection, requiring no minimum water flow. Even in static sludge deposition zones, T90 response time <40s, quickly capturing DO concentration changes.
Cut down maintenance frequency drastically

Factory pre-calibration eliminates monthly air calibration work; no anode/cathode cleaning, membrane and electrolyte replacement. Calibration cycle extended to 6 months, annual maintenance time reduced by 70%.
Aeration energy consumption reduction

Stable continuous DO signal supports intelligent blower variable frequency control, maintaining aerobic tank DO steady at 2–3 mg/L. Annual power saving for aeration system reaches about 130,000 kWh, equivalent to 100,000 RMB electricity cost reduction.
Effluent standard compliance improvement

Stable dissolved oxygen environment promotes microbial nitrification, effluent ammonia nitrogen concentration stably below national discharge standard, compliance rate raised from 92% to 99.8%.



Case 3: Coastal Estuary Water Nutrient & Discharge Compliance Monitoring


3.1 Project Profile


Local ecological environmental bureau launched coastal river real-time water quality monitoring stations to track nutrient salt and DO variation, supervise industrial wastewater outlet discharge up to standard. Water body is brackish mixing fresh water and seawater, with complex interference substances including heavy metal ions, residual chlorine (<4 ppm), sulfate and surfactant.


3.2 Equipment Selection Reason


Traditional electrochemical DO sensors suffer severe cross-interference from H₂S, metal ions and chloride in brackish water, causing measurement distortion. ACITEK LDO Model 1 has exclusive anti-interference performance, unaffected by H₂S, K⁺, Na⁺, heavy metal ions, Cl⁻ and low-concentration residual chlorine, fully matching estuary water monitoring demands.


3.3 Field Operation Effect



Long-term continuous immersion for 10 months without data distortion, accurately recording daily DO fluctuation for nutrient eutrophication analysis;
Support remote unattended monitoring, sensor cable up to 10m, immersion depth up to 34m to cover multi-layer water body sampling;
One-point air calibration simple operation for routine inspection, convenient for environmental law enforcement personnel on-site verification;
Data provides reliable basis for early warning of algal bloom and pollution source tracing, assisting environmental management department to complete regular water quality assessment reports.



Core Advantages Verified by All Three Field Cases


Combining seawater breeding, municipal sewage and coastal environmental monitoring practical application data, ACITEK LDO Model 1 shows irreplaceable strengths compared with conventional DO electrodes:



Zero pre-use calibration & no drift

3D factory calibration before delivery, out-of-box usable; no signal drift under long-term continuous operation, ensuring long-period data authenticity.
Ultra-low operation & maintenance cost

No consumables (membrane, electrolyte), only annual replacement of sensor cap; labor and material maintenance expenditure reduced by over 60% versus polarographic sensors.
Powerful anti-interference for complex water bodies

Optical luminescent principle avoids electrode poisoning; suitable for seawater, sludge wastewater, brackish estuary water with various ion contaminants.
Wide environmental adaptability

0–50°C operating temperature, 3.5 bar pressure resistance, compact small footprint for flexible pipeline/tank installation; compatible with ACITEK G800 controller for automatic linkage control.
Cost-effective seawater dedicated version

Stainless steel sensing head with corrosion resistance against saline water, one-year full machine warranty, support OEM/ODM customized cable length and thread interfaces for engineering integrators.



Conclusion


ACITEK LDO Model 1 (AC9020000-SW) luminescent dissolved oxygen sensor has achieved remarkable energy-saving, labor-saving and efficiency-improving results in marine aquaculture, municipal wastewater secondary treatment and coastal water environmental monitoring projects. Its low-maintenance, high-stability and strong anti-interference characteristics perfectly solve the long-standing pain points of traditional dissolved oxygen electrodes in complex water quality scenarios, especially seawater working conditions. For water treatment system integrators, aquaculture enterprises and environmental monitoring institutions pursuing long-term reliable online DO detection, ACITEK LDO Model 1 is a preferred cost-performance optical dissolved oxygen monitoring solution.