Fast, green, accurate Chemical Oxygen Demand analysis
MANTECH’s revolutionary PeCOD® COD Analyzer technology provides accurate chemical oxygen demand (COD) results in 15 minutes — without the use of harmful chemicals including dichromate and mercury. Highly adaptable for wastewater and drinking water applications, the PeCOD® COD Analyzer’s patented nanotechnology-based approach to COD analysis will save you time and money while protecting the environment and the health and safety of your workers.
peCOD is the fastest available method for quantifying chemical oxygen demand (COD), providing operators with real time data needed to make timely, impactful decisions that enhance environmental protection while generating substantial savings on chemical and energy use.
peCOD nanotechnology provides a higher oxidizing power and none of the risks associated with harmful chemicals such as dichromate and mercury used in traditional COD analysis. It’s safe and simple to use for any laboratory or operations staff member at any point in the process.
The core of the technology is the peCOD sensor, which consists of a UV-activated nanoparticle TiO2 (titanium dioxide) photocatalyst coupled to an external circuit. When a sample is introduced into the microcell containing the peCOD sensor, the TiO2 is irradiated by UV light, and a potential bias is applied. The UV light creates a photohole in the TiO2 sensor with a very high oxidizing power and organics in the cell are oxidized. peCOD is extremely accurate across a broad range of organics. The powerful oxidizing potential of UV-illuminated TiO2 ensures that virtually all species will be fully oxidized giving a true measure of COD.
The PeCOD® COD Analyzer technology is a proven performer in a variety of municipal and industrial wastewater applications. Recent studies have shown a strong correlation between the 15 minute peCOD method for testing chemical oxygen demand (COD) and standard dichromate COD (CODCR) and five-day BOD (BOD5) methods. In most cases, peCOD can be used as a BOD screening tool, providing accurate BOD estimates in just minutes versus several days.
The PeCOD® COD Analyzer will be the technology of choice as new regulations take effect in Europe in September 2017 that will eliminate the use of dichromate in COD testing. peCOD conforms to Method E3515, released in 2014 by the Ontario Ministry of Environment and Climate Change (MOECC) to replace the dichromate method for COD testing. peCOD is also included as an approved alternate COD method in the Protocol for the Sampling and Analysis of Industrial/Municipal Wastewater which was updated in 2016 by the MISA (Municipal Industrial Strategy for Abatement) program.
The PeCOD® COD Analyzer is available in a variety of configurations that use the same innovative technology and method. peCOD combines robust performance and flexibility to suit the needs of your laboratory or process operations.
Models and Specifications
MANTECH is excited to announce that the release of the PeCOD L50 Model! See here for more details.
The L50 is a direct replacement for the L100 shown in previous videos and pictures. The L50 offers a simpler, industrial and robust design, with improved pricing over the L100. Contact us for more information.
The PeCOD® COD Analyzer is available in laboratory, portable and online configurations that are highly customizable. The peCOD system can be configured to accommodate laboratory operations, automated sampling, or continuous process monitoring.
The Benchtop L50 PeCOD® COD Analyzer is MANTECH’s base model for use in industrial, municipal or government and academic lab settings.
- Small footprint (280 x 210 mm, 11.00 x 8.25 in)
- Lightweight (7 kg, 15.5 lb)
- MANTECH’s PeCOD Pro™ software adds automation and a sleek user interface
- Can be upgraded to Automated or Online systems
The world’s fastest method for chemical oxygen demand (COD) analysis is also available in a portable field unit. Just add the battery and carrying case and COD can be measured in the field without the need to transport toxic or hazardous reagents.
- Small footprint (508 x 355.6 x 609.6 mm, 20 x 14 x 24 in)
- Convenient case with wheels (weighs approximately 16 kg, 35 lb with analyzer & supplies)
- No sample digestion is required, making it a truly portable technique
- MANTECH’s PeCOD Pro™ software adds automation and a sleek user interface
The Automated L100 PeCOD® COD Analyzer provides unattended analysis for a large number of samples.
- Unattended, continuous analysis of 73 samples
- System is pre-calibrated before the start of each work day
- Additional parameters can be added on, including pH, EC, alkalinity, BOD and turbidity
The Online L100 PeCOD® COD Analyzer will automatically grab samples from a low flow line or wastewater tank, at scheduled time intervals.
- Save time and money through process optimization with real time COD results
- Option to add automated pH adjustment and dilutions
- Additional parameters can be added on, including pH, conductivity, alkalinity, and ammonia
Frequently Asked Questions
Chemical Oxygen Demand (COD) analysis is a measurement of the oxygen-depletion capacity of a water sample contaminated with organic waste matter. Specifically, it measures the equivalent amount of oxygen required to chemically oxidize organic compounds in water. COD is used as a general indicator of water quality and is an integral part of all water quality management programs. Additionally, COD is often used to estimate BOD (Biochemical Oxygen Demand) as a strong correlation exists between COD and BOD, however COD is a much faster, more accurate test. Learn more here.
Chemical Oxygen Demand (COD) analysis is a measurement of the oxygen-depletion capacity of a water sample contaminated with organic waste matter. Specifically, it measures the equivalent amount of oxygen required to chemically oxidize organic compounds in water. The traditional COD method is the wet chemistry method, dichromate COD (CODCr). This involves a two hour digestion at high heat under acidic conditions and involves hazardous chemicals such as mercury and dichromate.
Biochemical Oxygen Demand (BOD), also often referred to as biological oxygen demand, is a test performed to measure the potential of wastewater and other waters to deplete the oxygen level of receiving waters. The BOD test involves taking an initial dissolved oxygen (DO) reading and a second reading after five days of incubation at 20°C. For this reason, this test is often written as BOD5 for short.
MANTECH has developed an automated COD method utilizing a new, rapid and green technology called the PeCOD® COD Analyzer. This method directly measures the amount of oxidizable material in a sample via photoelectrochemical oxidation in a microcell, eliminating the need for time-consuming digestion and hazardous chemicals as only an electrolyte solution is required for analysis.
The primary driver of the peCOD method chemistry is advanced oxidation induced by photocatalysis with Titanium Dioxide (TiO2). Pure TiO2 is only photo-active at wavelengths below 380 nm. This is because a certain amount of light energy is required to bump the electrons around and cause the behaviors that we associate with photocatalysis. The UV LED in the PeCOD® COD Analyzer operates at a peak wavelength of 365 nm, with a minimum 360 nm and maximum 370 nm, ensuring that efficient photocatalysis is achieved.
The PeCOD Analyzer performs advanced oxidation on a small volume of sample. As the reaction proceeds, electrical charge is generated proportional to the oxygen being consumed. The PeCOD analyzer captures this generated charge, plotting the output current from the reaction over time as shown below. The area under the curve generated by plotting current over time is proportional to the COD of the sample. A blank charge is also determined for each sample, and subtracted from the total charge to ensure accuracy.
View the detailed overview of PeCOD technology and calculations here.
KHP (Potassium Hydrogen Phthalate) has historically been a common reference standard used in a variety of chemistry applications including the traditional dichromate COD test, where it does provide a result close to the theoretical COD result, and for TOC analysis. KHP is not recommended for use in the PeCOD COD analysis as it over reports compared to the theoretical COD amount. This is predominantly due to some pre-concentration of the molecule on the surface of the PeCOD sensor prior to analysis which is a peculiarity of KHP with the PeCOD COD method.
It is important to note that for all COD methods there are specific molecules whereby the individual analytical result is not well aligned to the theoretical value. For instance, organic compounds such as propionic acid, diethylamine or nicotinic acid could not be used as a COD standard for the dichromate COD method due to poor correlation to theoretical results but could be suitable for the PeCOD COD method. It is therefore important to chose a standard that provides a strong correlation to the theoretical result for the method employed, is a good reflection of the samples to be analysed, is suitable for general laboratory use and is readily available. For details on preparing sorbitol and glucose-based COD standards for the PeCOD COD method, read our technical bulletin 2017-029: PeCOD Standard Recipe.
pH Range: 4.0 – 10.0 (after mixing with electrolyte)
The peCOD method requires that the pH of a sample AFTER being mixed with electrolyte must be between 4 – 10. To determine if a sample must be pH-adjusted, mix the sample with peCOD electrolyte at the proper mixing ratio for your COD range, then test the pH of the mixture.
For example, the sample may have a pH of 3.0, but then after preparing with electrolyte, the pH is in the required range, therefore, it is acceptable for immediate peCOD measurement.
Samples must be filtered prior to peCOD analysis to ensure that no particulates greater than 50 micron (um) are primed into the peCOD. Particulates larger than 50um can cause clogging, which can lead to damage of the internal fluidics of the machine. To prevent clogging and ensure proper sample preparation, MANTECH has a Sample Filtering Guide for PeCOD Analysis.
For pulp and paper and wastewater applications, MANTECH recommends using a 35um polyethylene (PE) syringe filter. These filters can contribute trace amounts of organics, which are negligible for wastewater applications. For drinking and source water applications it’s important to use a filter that does not contribute organics to the filtered sample. One of MANTECH’s research partners has recommended a 0.45um polyethersulfone (PES) filter; however, other filter types may also be acceptable, if no organics are contributed by the filter. Since these applications traditionally see less particulates, having a smaller pore size filter hasn’t shown an impact on the peCOD results.
There is a strong correlation between the PeCOD COD results and the dichromate COD results. To determine this, the two methods were compared vs. the theoretical oxygen demand (ThOD) for 34 organic species. See MANTECH’s technical bulletin for more information on the study.
Chemical Oxygen Demand (COD) results may differ when measured via the PeCOD COD method versus the traditional dichromate COD method for certain sample matrices. There are various reasons for this difference. One is that chloride, ammonia, and some heavy metals have been known to interfere with PeCOD readings and provide inaccurate results. Another reason could be the time delays between analyses. It is best to analyze samples via PeCOD and dichromate on the same day to limit uncertainties due to sample degradation. For additional reasons and more information, read MANTECH’s technical bulletin here.
The PeCOD electrolyte solution is mainly composed of a low-concentration lithium nitrate solution. The PeCOD calibrant and check standard solutions supplied by MANTECH are composed of sorbitol. These solutions contain a trade recipe preservative that allow for the longer shelf life, compared to solutions prepared manually. Calibrant and check standard solutions prepared manually, following the PeCOD Standard Recipe, can be used for up to two weeks.
Both MANTECH supplied calibrant and standard solutions are good for one year after they are made. MANTECH supplied electrolyte has a shelf life of two years after it is produced. All labels have the expiry date in the box just above the MANTECH logo.
Sensors are expected to last 150 runs when used consistently for an average of 50 samples per week (samples, calibrations and QC checks). However, should a sensor be intermittently used, it is recommended that it be changed after 3-4 weeks of use regardless of the number of completed runs, or based on consistently failing calibration values. When analyzing higher sample concentrations (especially red range) the sensor life expectancy is likely to be shorter, ranging from 60 – 150 total measurements. For more information, read MANTECH’s technical bulletin here.
Open the top plastic door by pushing down firmly on the front centre of the door until a “click” is heard, then release the door. Open the PeCOD analyzer module by pressing firmly down on the fixed bar, and lifting the front latching bar (should unlatch), then lift up the PeCOD sensor lid. Remove the old sensor by lifting it off of the pins and place the new sensor on the same pins with the “THIS SIDE UP” surface (blue side) facing you.
If only storing the electrode block for a short period of time (less than 4 weeks), rinse DI water through the PeCOD and leave the electrode block inside. Make sure all of the sample has been washed through by priming Port A several times. If storing for more than 4 weeks, put DI water through the PeCOD and then remove the electrode block to store outside the PeCOD. Flush the channels with 20-30 mL of DI water before pushing through about 10 mL of NaCl, leaving the channels filled. Tape the ends of the channels to ensure no leaks or crystallization occur. For more information, read the storage instructions here.
There are limitations to ensure that, after dilution with electrolyte, the chloride concentration will be <200mg/L. This means that the allowable chloride concentration of the original sample varies depending on the COD range (as illustrated below) since each range has a different ratio of sample to electrolyte. For more information, read MANTECH’s technical bulletin here.
There are 4 COD ranges for the PeCOD. The advanced blue range is the lowest range and analyzes samples up to 25mg/L with a mixing ratio of 3:1 (sample to electrolyte). Green is the second lowest range and measures up to 150mg/L with a mixing ratio of 1:1. The yellow range determines COD up to 1,500mg/L with a mixing ratio of 1:9 and the red range can analyze samples up to 15,000mg/L and has a mixing ratio of 1:49. For more information, read MANTECH’s technical bulletin here.
A C value is reported after a calibration. It is measured in μC, and indicates the raw charge generated during the blank oxidation. In PeCOD Pro, the C Value can also be referred to as the Zero Charge (Z1). The expected C value ranges depend on the color range you are working in (advanced blue and green ranges have lower C values than yellow and red ranges). The acceptable values are 50-300 µC for advanced blue range, 150-700 µC for green, 200-750 µC for yellow range, and 250-800 µC for the red range.
An M Value is also reported at the end of a calibration. It is a ratio of the expected COD to the charge generated during the reference oxidation (of the calibrant solution). It is expressed as COD/μC. The acceptable M value range for the green, yellow, and red ranges is 0.02-0.06 COD/μC. The advanced blue range has an acceptable M value range of 0.01-0.08 COD/μC.
The Y-axis of the oxidation graph is defined as the Iwork (reported as μA) which is a measure of current. The Iterm is essentially the Iwork at the end of each oxidation curve as it levels off. The acceptable Iterm value for advanced blue and green ranges is >16 μA. For the yellow and red ranges, the Iterm value needs to be >14 μA.
The PeCOD conforms to regulatory standards such as the ASTM International Method D8084, the Ministry of Environment, Conservation and Parks, Ontario (MECP) method E3515, and the Health Canada Guidance on drinking water.
The ASTM International method for photoelectrochemical oxygen demand is approved for measuring organics in freshwater sources and treated drinking water. More details about this method can be viewed here.
The Ontario MECP method E3515 replaced the standard dichromate methods due to the fact that no harmful chemicals are used in the PeCOD method. This method now includes PeCOD as an approved alternate COD method in the Municipal and Industrial Strategy for Abatement (MISA). The MECP method can be viewed here.
The peCOD method is also referenced in the Health Canada Guidance on Natural Organic Matter in Drinking Water. COD has been added as a parameter with a <5ppm limit, only the peCOD method is referenced for the parameter, and peCOD is also referenced as a “parameter” to monitor in source waters for drinking water plants. For more information, read the article in Environmental Technology here.
The PeCOD COD Analyzer has a warning label on the analyzer head “DO NOT OPEN ANALYZER LID WHILE IN OPERATION” and “CAUTION: CLASS 3B INVISIBLE LASER RADIATION. AVOID EXPOSURE TO BEAM.” See Image 1.
Image 1: Warning label on analyzer lid
There are two normal LED lights (one red, one green), and one (invisible) Class 3B UV LED laser. See Image 2.
The red LED light is an error indicator and is a non-harmful light. The green LED light is the power indicator and is also a non-harmful light.
The Class 3B UV LED laser is a catalyst for TiO2 oxidation of organics. Class 3B UV LED lasers are harmful to your health, however, there are safety measures put into place to avoid exposure to this invisible UV LED laser on the PeCOD COD Analyzer. The PeCOD has an automatic laser shut off built in so the laser will turn off when the analyzer lid is opened. This lid should not be tampered with or modified as the Class 3B laser is hazardous to your health.
Image 2: Analyzer head with 2 (two) normal LED lights, and 1 (one) 3B UV LED Laser
The L50 is the newer, more cost efficient model of the PeCOD. It uses the same method, reagents, and software as the L100. Improvements were made with the fluidics and space requirement in the L50 model. For more information, see the news section.
Click ‘File’ in the top left corner, and select ‘Preferences’. The ‘General’ tab will pop up, select the ‘QC Regimes’ tab. Here you can see how many calibrations, QC checks, and recalibrations the PeCOD® will preform for the ‘Startup (Daily) Regime’. To see the other regimes, select the ‘Startup (New Sensor)’ tab, or the ‘QC Routine’ tab in the second row. To edit the number of calibrations or QC checks, click the arrows beside the numbers to choose how many of each the PeCOD® will perform.
MANTECH recommends storing samples in the laboratory fridge vs preserving samples. If you do choose to preserve your samples, use H2SO4 to adjust the pH of your samples to ~2.
For peCOD calibration, the peCOD goes through the following phases:
- Normalization Phase. This is where the peCOD is adjusting the LED lamp output, trying to achieve a baseline of 20µA.
- Burn-In Phase (port B). This is where the pre-mix blank solution is brought into the sensor cell. It is oxidized to remove contaminants from the cell.
- Pre-Burn Phase (port B). This is where a new aliquot of pre-mix blank solution is brought into the sensor cell. This phase removed more contaminants from the cell and conditions the cell for the pre-mix blank.
- Oxidation (port B). A new aliquot of pre-mix blank is brought into the sensor cell and is oxidized. This value is used in the peCOD calculation. The area under this curve is used to calculate the ‘blank charge’, which corresponds to the C value determined by each calibration. This is the small amount of COD contributed by the electrolyte reagent, which is then subtracted from all future COD analyses to give the final COD result.
- Pre-Burn (port A). A new aliquot of pre-mix calibrant solution is brought into the sensor cell where it is oxidized. This removes contaminants from the cell and conditions the cell for the pre-mix calibrant.
- Oxidation phase (port A). A new aliquot of pre-mix calibrant if brought into the sensor cell. This value is used in the peCOD calculation. The area under the curve is used to calculate the reference charge, which is used with the blank charge to determine the relationship between charge and COD. This corresponds to the M value determined by each calibration.
For peCOD sample analysis, the peCOD goes through the following phases:
- Burn-In phase (port B). The pre-mix blank solution is brought into the sensor cell and is oxidized. This removed contaminants from the cell.
- Pre-Burn phase (port A). An aliquot of sample is brought into the sensor cell and is oxidized. This removes contaminants from the cell and conditions the cell for the sample.
- Oxidation phase (port A). A new aliquot of sample is brought into the sensor cell and is oxidized. This value is used in the peCOD calculation. The area under the curve is used to calculate the charge generated by sample oxidation. The blank value will be subtracted from the sample value to determine the sample COD.
It is possible that a PeCOD will fail it’s calibration. If this occurs, the PeCOD will notify you of the reason it did not pass. Common reasons are that the M value or C value are out of range. Please refer to page 19 of the PeCOD Pro Operation manual for more information.
There are several common methods to test wastewater and drinking water for organic pollutants, natural and chemical. Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD) and, Total Organic Carbon (TOC) compromise the three main methods of testing water samples. BOD and COD methods differ from TOC because they measure the amount of oxygen that is depleted by organic species in water. Moreover, TOC is a measure of all carbon (both organic and inorganic), rather than the oxygen that is reduced by these species. As written by a TOC manufacturer, “TOC on its own sheds no light on the oxidizability of the measured carbon or the amount of oxygen needed for its biodegradation.” Specific to COD, it measures the reactive fraction of the TOC. This is also known as oxidizability in the European Union.
View the full article: Comparison of COD, BOD and TOC Methods for organics, which summarizes the advantages and disadvantages of the COD, BOD and TOC methods, and compares them to the PeCOD method.