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Dichromate method - Alternatives are urgently needed

The European Parliament and the Council called 'REACH' have adopt a ban which prohibits the use of Potassium dichromate.

COD analyzer QuickCODultra

Potassium dichromate is also known as double potassium. It is used in the tannery, in certain printing processes and in the chemical analysis. For instance the chemical oxygen demand (COD) of water is determined by the definition of potassium dichromate method (dichromate method DIN 38409-41: 1980-12).

A few years ago it was only classified as irritant but today it is considered to be mutagenic, toxic for reproduction and dangerous for the environment as well as carcinogenic. The European Parliament and the Council called 'REACH' (Registration, Evaluation, Authorisation and Restriction of Chemicals) have adopt a ban in April 2013, which prohibits the use of this chemical. Manufacturer of COD tests, which employ Potassium dichromate, can apply for a special individual permission for re-use. The European Commission adopts a final decision about the exceptional authorizations.

Because of the dangerous dichromate method, the varying recovery rates, the known chloride interferences as well as the high demand of time of 2h alternative approaches are urgently required. A first step to use a constant sample matrix, is to adjust a correlation factor, according to the mixture of substances in water. Thus, the fast and reliable Online-TOC-Measurement technology can also be used for COD determination. An additional alternative is the direct measurement of the oxygen demand. With LAR's QuickCODultra, the online analyser to determine the total oxygen demand, both alternatives are possible. The measuring system operates with the ultra-high temperature method at 1200 ° C and goes with no dangerous chemicals.

Due to the patented sampling system FlowSampler a blockage-free sampling is ensured. The QuickCOD determines reliably fluctuating loads and peak loads up to 200,000 mg / l and provides measurement results in a few minutes. The water sample is taken event dependently and without any pretreatment such as dilution, or other modifications by chemicals or additives. Only this way, the sample is reliably detected in its entirety, including all contained particles, and the true load is determined.

The sample is injected into the reactor by the proven XY- technology. The robotic horizontally and vertically moving needle takes an exact sample dose in the micro-liter range and injects it into the oven through the patented lock valve. It ensures that the oven stays 100% sealed from the ambient air at any time. This guarantees that all ingredients are oxidized, completely at 1200 ° C whether volatile or not. This process control reduces carryover effects, blockages and down times. With this smart sample feeding components such as flakes or solids do not disturb the measurement. They are rather recognized as an important part of the sample and also considered completely.

The COD measurement has become indispensable for a cost-effective process control and monitoring. A measuring instrument that provides reliable and fast results is not only inevitable in fact of that, but also to observe all guidelines and regulations. LAR's QuickCODultra fulfills these requirements and, additionally, is an environmentally friendly and safe alternative to the dichromate method.

 

 

The total organic carbon (TOC) is one of the most important sum parameters in the assessment of the organic pollution of water. Since it includes all carbon compounds as one mass, it is exactly defined and an absolute quantity. Therefore, it may be determined directly.

Read more about TOC measurement methods.

Total organic carbon analyzers of LAR Process Analysers AG

The chemical oxygen demand (COD) indicates the amount of oxygen which is needed for the oxidation of all organic substances in water and is thus an important indicator for water analysis. It is considered in the planning and controlling of treatment, as well as assessing its efficiency, thus forming the basis for the calculation of waste water charges.

The COD can be determined in laboratory or online, whereby these methods significantly differ in duration and consumables used.

Read more about COD measurement methods.

COD analyzers of LAR Process Analysers AG

The biochemical oxygen demand (BOD) indicates the amount of oxygen which is needed for the biological degradation of organic substances in water.

Since the generally used BOD5 excludes the nitrification part of the process, this parameter is poorly suited for the control of waste water treatment plants. Alternatively, the total BOD is well-suited, due to the determination of the nitrogen as well as the carbonaceous part of biological degradation.

Read more about the online measurement of BOD.

Toxicity is described as the direct harmful effect of a substance on organisms. These effects can already occur at low concentraions of toxic substances and are dependent on the incubation period and the dosage.

Some test methods that are available on the market can detect toxicity by using fish, daphnia, molluscs, algae or luminous bacteria and testing whether a water sample has a toxic effect on the organisms. They do not, however, identify exactly which toxins are present.

Read more about online toxicity measurements.

BOD / toxicity analyzers of LAR Process Analysers AG

The total nitrogen bound (TNb) shows the pollution of water caused by nitrogen compounds. Nitrogen may be present as ammonia, ammonium salts, nitrites, nitrates and organic nitrogen compounds.

In contrast to single measurements of the above-mentioned components, the TNb determination contains all these substances in a single analysis process.

Read more about online TNb measurements.

The total phosphorus (TP) is a sum parameter that shows the organic and inorganic phosphorus compounds in water. Phosphorus is an essential nutrient for humans as well as flora and fauna. However, the substance – depending on its concentration– may cause serious damage.

Read more about online TP measurements.

TN TP analyzer of LAR Process Analysers AG