Total Organic Carbon (TOC)

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What is Total Organic Carbon (TOC)? 

Total organic carbon is a measure of the amount of organic compounds contained in a water sample. Organic carbon-containing compounds can either be dissolved in water or exist in water as undissolved, suspended material, or liquid. This organic matter can enter water naturally and through man-made sources/processes.

Examples of organic matter are plant or animal based, or synthetic substances containing carbon and other elements defining organic compounds. Inorganic matter is mineral carbon-containing compounds.

Why Measure TOC?

While organic matter isn't necessarily toxic, high concentrations in water can significantly impact ecosystems and damage equipment when left unchecked and untreated.

Avoid Environmental Consequences

Organics can be toxic to the environment in rivers or streams, even if the compounds themselves are not directly toxic. By depleting oxygen levels in water, organic waste can lead to fish suffocation and can affect water ecosystems in many other ways.

Ensure Compliance with Regulations

Organic compounds are precursors for disinfection by-products (DBP), which are strictly regulated in the drinking water industry. Measuring TOC makes it possible to implement the right treatment to reduce the formation of DBP to comply with the regulatory requirements.

Industries and municipalities that do not properly monitor TOC may fail to comply with laws and regulations, incurring fees or fines. There are additional financial consequences for exceeding permit limits for discharge.

Business Efficiency & Integrity

The organic compounds in products can have a detrimental effect on taste, odour, aesthetics and customers’ perceptions of quality. Excessive organic content in source water can influence the cost of production, cause contamination, result in charges for wastewater treatment, present challenges to meeting regulations and bring about negative environmental consequences that could harm the reputation of a business.

Wastewater Treatment

Events outside of the normal or expected process can affect the organic load. These events can disrupt or even be catastrophic to the treatment process. Monitoring TOC in wastewater influent and effluent can allow the plant to manage the treatment process efficiently, redirect the water as needed for retention and additional treatment, and avoid violations of the discharge regulations.

At Hach ®, find the testing equipment, resources, training and software you need to successfully monitor and manage TOC levels in your specific process application.


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Featured Products to Measure Total Organic Carbon (TOC)

TOC

The Hach TOC Analyzer completes a full breakdown of process samples to deliver trusted results.

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EZ Series TOC Analysers

The EZ Series Online Analyzers offer multiple options to monitor TOC and Total Carbon (TC) in water.

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LCK385 TOC cuvette test (purging method) 3-30 mg/L C, 25 tests

TOC TNTplus chemistry and your Hach spectrophotometer are engineered to simplify water analysis for accurate results, every time.

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LCK386 TOC cuvette test (purging method) 30-300 mg/L C, 25 tests

TOC TNTplus chemistry and your Hach spectrophotometer are engineered to simplify water analysis for accurate results, every time.

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Spectrophotometers

The DR6000 is a benchtop UV-VIS (190 - 1100 nm), split beam spectrophotometer that delivers top performance for both routine laboratory tasks and demanding applications.

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Which Processes Require Total Organic Carbon Monitoring?

Wastewater Treatment

Determining the full TOC load before it enters the treatment facility allows the plant to prepare for treatment and optimise operation. Measuring the TOC discharge at the end of treatment helps ensure that the plant complies with regulations.

A wastewater equalisation tank is a good source to monitor full TOC load before it enters the treatment plant.

Drinking Water Treatment

Raw water sources such as lakes, streams and reservoirs contain natural organic matter (NOM) from decaying plant or animal content. During disinfection, organics can combine with chlorine and other disinfectants to form harmful DBP ( DBP reduction). To comply with regulations, drinking water plants that are held to DBP requirements must measure TOC in raw and treated water to calculate the TOC percent removal. Dissolved organic carbon content in drinking water can also affect odour, taste and appearance.

A water treatment facility monitors for natural organic matter present in raw water sources.

Dairy Industry

At each stage of dairy processing (as milk is converted into products like cheese or butter), a TOC analyser can indicate potential product lost to the effluent, aiding in process control. Measuring TOC at the end of the processes, allows the facility to confirm that it complies with its regulatory discharge limit. Monitoring the milk fats that leave the plant in effluent, can reduce product loss and wastewater treatment costs, resulting in increased revenue.

A worker stacks blocks of cheese at a dairy plant. In the dairy industry, TOC analysers can aid in monitoring effluent organic waste and reducing product loss.

Industrial Boilers

In boilers, condensate from the heat exchangers can be returned to the boiler. TOC can be used to ensure the quality. If the TOC levels in the condensate are too high, the condensate must be diverted away from the boiler to prevent damage. Continuous TOC monitoring allows operators to make adjustments quickly, preventing equipment damage, production downtime and revenue losses.

Industrial boilers at a factory. TOC levels need to be monitored here to ensure organics that can cause damage are not present in the return condensate

Cooling Towers

Measuring the TOC of the source and make-up water before it enters the heat exchangers ensures that it does not contain organics that may damage the equipment. Checking the TOC of the water after the cooling process ensures that the heat exchanger has not leaked contaminants into the water coming to the receiving water body.

Water cooling towers at a treatment plant work best with water free of organics that can cause build up and equipment damage.

Storm Water Treatment

TOC levels guide the treatment of storm water. If the TOC levels are normal, the water is discharged directly into a waterway. If the TOC levels are too high, the storm water is diverted into a retention pond and then treated by a wastewater treatment plant. Monitoring TOC helps the industrial facilities remain in compliance with storm water regulations.

This storm drain diverts water into holding ponds where TOC levels can be monitored.

How is TOC Measured?

TOC is measured in a 3-step process:

  1. The sample is added to the reaction vial that contains acid then the vial is placed into the TOC X5 Shaker device to release the inorganic carbon (TIC) portion of the sample.
  2. After driving off the TIC, the reaction vial is attached to the pH indicator vial via a gas permeable membrane two-sided cap.
  3. The vial combination is then placed into the DRB200 digestion block for 2 hours at 100°C.

LCK385 TOC cuvette test (purging method) 3-30 mg/L C, 25 tests

Laboratory Testing

Individual samples are tested in the lab and the results may be charted to identify trends.

LCK385 TOC Cuvette Test

XPERT TOC/TN Analysers


Hach BioTector TOC Analyzer

Online Process Testing

Online analysers can be placed throughout a facility to continuously monitor TOC levels and automatically chart results to identify trends.

BioTector TOC Analyser Family

Frequently Asked Questions

Are Hach’s LCK TOC Reagents approved for enviromental compliance reporting?

Yes, - Hach LCK cuvette tests are officially approved for legally required consent limits. With the help of standard solutions and round-robin test solutions, they provide the assurance you need.

How can you measure NOM in drinking water applications?

Managing natural organic matter (NOM) is important to produce safe drinking water. NOM, measured as TOC can react with chlorine to form DBP. The NOM, which is the precursor of DBP formation, can be measured by TOC analysis. The Hach BioTector B3500dw Online TOC Analyser , which is developed specifically for the drinking water industry, optimises the monitoring and the removal of organics based on real time TOC measurements. BioTector utilises 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.

What is the relationship between BOD, COD and TOC?

Biochemical oxygen demand (BOD) can be estimated from chemical oxygen demand (COD) measurements, if a correlation is established. This requires historical data of BOD and COD measurements taken over a period of time. Typically, the average BOD result is divided by the average COD result to find a "conversion factor" between the two parameters. One would then multiply their COD results by this factor to estimate BOD.

COD values are almost always higher than BOD values for the same sample. As a result, the multiplication factor will usually be less than one.

Once established, the correlation will only apply to the sample used to create it (one couldn't use the correlation with samples taken from other water sources). If the sample composition changes significantly (due to temperature or seasonal variations), a new correlation may need to be established. TOC measurements can also be used to estimate BOD using a correlation. The same methods and considerations would apply.