The client is a food industry manufacturer—you have likely tasted their delicious nut products. They recently wanted to measure the COD (Chemical Oxygen Demand) of their wastewater and compare the results with their online monitoring data to gain a better understanding of their water quality. We were honored that they purchased one of our rapid COD testing instruments, and we visited their facility to provide free on-site training.
I. Explanation of Theoretical Foundations and Principles
1. **Principles of Rapid Digestion Spectrophotometry:** Explained how organic matter in water samples is oxidized at high temperatures in the presence of strong acids and catalysts, with COD concentration calculated by measuring changes in absorbance.
2. **Equipment Overview:** Introduced the performance characteristics and measurement ranges of core equipment—such as the rapid COD analyzer and multi-function digester—as well as storage requirements for the accompanying pre-prepared reagents.
3. **Safety Precautions:** Emphasized that the reagents used are highly acidic and corrosive; operators are required to wear lab coats, acid/alkali-resistant gloves, and safety goggles.
II. Standardized Hands-on Practice
1. **Startup and Preheating:** Turned on the digester (set to 165°C) and the main analyzer unit to begin preheating.
2. **Sample Addition and Mixing:** Accurately pipetted distilled water (for the blank sample), standard solution, and the wastewater sample (for testing) into separate pre-prepared reagent tubes. Tightened the caps and mixed thoroughly to ensure complete reaction between the reagents and the samples.
3. **High-Temperature Digestion:** Placed the digestion tubes into the preheated digester and closed the protective cover. Heated for 20 minutes. Emphasized that the process must not be interrupted and the heating block must not be opened during this time to avoid affecting the reaction.
4. **Cooling and Colorimetric Measurement:** Removed the tubes after digestion, allowing them to cool in air for 2 minutes followed by a water bath for 2 minutes (cautioned against placing hot tubes directly into the instrument to avoid damaging the optical system). Wiped fingerprints and water stains from the tube exteriors using a soft, lint-free cloth. Inserted the blank sample first to “zero” the instrument, then inserted the test sample to read the COD concentration.
III. Data Recording and Routine Maintenance
1. Data Processing: Guide customers to record test data systematically (including dates, sample IDs, etc.) and use the instrument’s printing function to generate test reports.
2. Cleaning and Maintenance: Demonstrate how to clean digestion tubes and advise on the periodic replacement of reagents, as well as checks for printer paper and the cleanliness of the optical system.
3. Calibration and Troubleshooting: Explain the schedule for periodic instrument calibration using standard solutions (e.g., every 3–6 months for standard use, or monthly for high-frequency use) and teach methods for troubleshooting common data anomalies.
Post time: Sep-17-2026
