What is Total Organic Carbon?
Total Organic Carbon (TOC) testing is important in drinking water treatment as an indicator of potential disinfection by-product formation. In wastewater, TOC is valuable as a surrogate for COD testing and has applications in domestic wastewater pre-treatment standards, effluent discharge limitations, and industrial process waters.
The colorimetric TOC test measures the total amount of non-volatile organic carbon in a sample. The method is based on controlled digestion/diffusion in a sealed glass assembly*. Sample carbon is oxidized to carbon dioxide by persulfate oxidation. The carbon dioxide diffuses into a colored pH indicator solution where it is converted into carbonic acid. The resulting color change is proportional to the concentration of carbon present in the sample.
Chemical Reactions:
Inorganic carbon is removed from the sample by adjusting the sample to pH 2 with a buffer, and stirring vigorously for 10 minutes:
TOC = Total Carbon – Inorganic Carbon
A suitable volume of treated sample and potassium persulfate is added to a 16-mm screw top digestion vial containing Acid Digestion Solution Reagent. A 9-mm sealed glass ampule containing the TOC Indicator Solution is opened and placed inside the digestion vial. The whole assembly is then sealed with a screw cap and digested at 103–105° C (217–221 °F) for 2 hours.
In the presence of acidic persulfate and with increased pressure and elevated temperature, the sample’s organic carbon is oxidized to carbon dioxide. For example, in the persulfate digestion of a sample that contains formate, the chemical reaction is:
S2O82- + HCOO- → HSO4- + SO42- + CO2
The evolved CO2 then diffuses and is trapped in an aqueous solution containing a pH indicator. The absorbed CO2 forms carbonic acid according to:
CO2 + H2O → 2H+ + CO32-
The pH indicator (prior to CO2 absorption) is in its deprotonated, or basic, form (D–). As the absorbed CO2 level increases, the hydrogen ion level will also increase, resulting in an increase of the protonated form of the indicator:
D-(Color A) + H+ → DH (Color B)
The concentration of the carbon in the sample is proportional to the color change, either the change in Color A (D–), or the change Color B (DH) or the sum (D– + DH). What container does Hach recommend for collecting total organic carbon (TOC) samples for laboratory analysis?
A good bottle for collecting TOC samples is Product # 2794005. This is a glass 40-mL vial that is precleaned to USEPA standards for volatile organics analyzes.
How can a Total Organic Carbon (TOC) method be used to test for Dissolved Organic Carbon (DOC)?
The analysis of DOC is almost identical to that of TOC, but the sample must first be filtered through a 0.45 micron pore-size filter. Depending on the volume of sample and level of suspended solids, different types of filters may be used (syringe filters up to electronic-pump filters). None of Hach's TOC analyzers have a built-in filter explicitly for DOC, so the filtration needs to be conducted by the user first.
If the sample for a total organic carbon (TOC) test cannot be run right after sampling can the sample be preserved and measured later?
If immediate analysis is not possible, cool the sample to 4 °C with no headspace. Cooled samples can be stored for several days. Acid preservation is not recommended because it results in poor digestion efficiency and low recovery.
For the best accuracy, however, samples should be analyzed as soon as possible to prevent consumption of organic carbon by bacteria. Bacteria consume some organic molecules, such as glucose, much faster than others. Methods 10128, 10129, and 10173 instruct to analyze the sample as soon as possible for best results.
How can we reduce Influent Toxicity in Wastewater?
Influent toxicity is a non-specific parameter that allows you to monitor and protect your wastewater treatment plant’s valuable microorganisms from toxic influent. During this session, you will learn how a toxicity index and continuous monitoring can help protect plant assets and improve operations.
20_c-vid_22_Hach - Monitoring Influent Toxicity in Wastewater Treatment Plants - June 18, 2020 from Hach Pictures on Vimeo.
What Is TOC or Total Organic Carbon and why is it measured?
TOC analysis measures organic contamination levels (organic load) - a crucial indicator of general water quality and as control for water treatment processes.
TOC responds to all organic types, either dissolved or suspended in water, even if containing oil, fats, greases, salts, particulates or high sulphur levels.
TOC (Total Organic Carbon) is a crucial parameter for water quality analysis. It helps in determining the amount of organic carbon present in each sample of water.
The measurement of TOC is vital for assessing water quality and ensuring its safety. By analyzing TOC levels, it becomes possible to evaluate the presence of organic matter and potential contaminants in water sources. This information is particularly significant for applications where the purity of water is essential.
TOC analyzers, instruments specifically designed for TOC analysis, are used to measure, and calculate TOC levels accurately. These analyzers employ various methods to determine total organic carbon in water samples. The TOC principle involves the oxidation of organic carbon compounds, followed by the detection and quantification of the resulting carbon dioxide.
By utilizing TOC analysis, professionals can assess water quality, calculate TOC concentrations, and understand the organic carbon content in both soil and water. This information aids in monitoring environmental conditions, identifying potential contaminants, and optimizing water treatment processes.
TOC analysis has gained significance due to factors such as the Disinfection Byproduct Rules (DBPR) Stage I and II, which require increased monitoring for TOC. The awareness of disinfection byproducts and their potential health risks has emphasized the importance of measuring TOC levels in water.
Understanding the basics of organic chemistry reveals that when organic carbon combines with chlorine, it results in the formation of disinfection byproducts (DBPs). This relationship emphasizes the need for TOC analysis as a means to monitor and control the formation of DBPs, ensuring water safety.
In the event of spills or accidental releases, TOC analysis proves to be a valuable method for detecting a wide range of contaminants in water. The measurement of TOC levels provides an effective means to identify and assess the presence of various organic compounds that may have entered the water supply.
Optimization of water treatment processes is another area where TOC analysis plays a vital role.
In summary, TOC (Total Organic Carbon) is a key aspect of water quality analysis. It provides valuable insights into the organic carbon content in water samples, aiding in monitoring, assessing, and optimizing water quality for various applications.
What are the Organics Measurement Methods?
Biological oxygen demand (BOD) and chemical oxygen demand (COD) are commonly used to indirectly measure organics, but it takes five days to test BOD and several hours for COD. Lab TOC analysis directly measures organics but without continuous readings, it is difficult for facilities to optimize treatments or detect product loss. Only online TOC analysis provides quantifiable product loss detection and helps protect capital equipment. Many TOC analysers won’t hold up in the harsh conditions of food and dairy processing. However, the B7000 uses patented two stage advanced oxidation (TSAO) technology and larger internal diameter tubing (with self-cleaning), giving the B7000 the ability to measure organics reliably in food processing conditions with 99.86% uptime and required preventative maintenance only twice per year.
With the ability to monitor two streams, the B3500c is ideal for clean water, such as condensate applications. Facilities can continuously monitor condensate return lines for organics to facilitate water reuse. When TOC is high, systems can divert the condensate to protect equipment, alarm staff to look for leaks, and track TOC data for process improvement.
Can the BioTector TOC analyzers handle high sulfate levels?
Many TOC analyzers will have a hard time with high levels of sulfates. BioTector actually uses 1.8 N H2SO4 and 6 N H2SO4 reagents which means that the BioTector will not have a problem with measuring sulfates.
What phases are involved in The TSAO Technology?
Patented two-stage oxidation with hydroxyl radicals, ensures complete oxidation of the sample.
First phase
- ToC stripped by adding acid.
- The resulting CO2 is measured in the IR detector.
- Important: The ToC stripping is controlled by the CO2 curve, which ensures that all the ToC is stripped.
Second Phase
- TOC converted into carbonates and oxalates by adding ozone and lye.
- Carbonates and oxalates converted into CO2 by re-adding acid.
- The resulting CO2 is measured in the IR detector.
The online total organic carbon (TOC) analyzer BioTector series is a TOC analyzer uses the “two-step oxidation method" with strong oxidizing power. In addition, the energy cost is 1/5 or less compared to a general combustion-type TOC meter, contributing to the realization of SDGs.
What is the Importance of Monitoring Organics?
All food sources have an organic component. Monitoring organics in water and drain lines helps production facilities quickly and accurately measure the carbon content in their water streams so they can:
- Maximise production yield by quickly detecting product loss events to take corrective actions and improve production management processes to prevent future product loss.
- Mitigate compliance risks by addressing biological treatment overload, irregularities in operations, and inefficient chemical feed in the wastewater treatment process. Food production facilities can save energy, reduce chemical consumption, and generate less solid waste while consistently meeting regulation requirements.
- Protect capital equipment by reducing corrosion, leaks,fouling, maintenance, and downtime. Organics in condensate will cause organic acid formation, leading to corrosion of the boiler and damage to valuable assets.
The BioTector TOC Analysers help facilities run more efficiently by measuring organics in minutes to diagnose product loss, optimise treatments, improve process control, protect capital equipment, and most of all ensure compliance.
Can the Biotector measure COD?
Can I use the Biotector to calculate product loss?
Since the Biotector measures TOC, a total sum parameter of carbon compounds present, this can be used to calculate product loss.
Does the Biotector have a self cleaning function?
The entire system is automatically self-cleaned by the reaction process during every cycle.
Can I measure anything other than TOC?
The Biotector B7000 can directly measure TOC, TC, IC, VOC, TN, TP as well as BOD and COD via correlation.
Can I use the Biotector to monitor NOM in drinking water applications?
The Hach BioTector ® B3500dw Online TOC Analyzer , which is developed specifically for the drinking water industry, optimizes the monitoring and the removal of organics based on real time TOC measurements. BioTector utilizes an advanced oxidation technology, which is a US EPA approved method, and supplies accurate and reliable detection of organics, assisting and ensuring optimal water treatment process.
How often do I need to maintain the instrument?
HACH recommends a six monthly service and maintenance schedule which is typically conducted by factory trained HACH service technicians.
Can the Biotector handle high salt levels?
The Hach B700i is designed and tested to handle up to 30% w/v salt levels.