Drinking Water, Fully Characterized
MANTECH’s revolutionary peCOD Analyzer technology measures the chemical reactivity and associated oxidative changes in Natural Organic Matter (NOM). As a result it is more sensitive than Total Organic Carbon (TOC) and UV254 to changing NOM concentrations in source and treated drinking waters.
Introduction to the PeCOD® L50 COD Analyzer.
Download the brochure for Online L50 PeCOD Analyzer.
Follows ASTM International approved method D8084
Download PeCOD Pro™ Software for Benchtop L100
peCOD is the fastest available method for quantifying oxygen demand (OD), 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. It offers a low detection limit (< 1 mg/L) with results generated in less than 10 minutes.
peCOD offers a safe, fast and green chemistry method that can be used by anyone. This eliminates the need for trained analytical chemists on staff or an external lab facility
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 OD.
The peCOD 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 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 Analyzer is MANTECH’s base model for use in municipal, 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 oxygen demand (OD) analysis is also available in a portable field unit. Just add the battery and carrying case and OD can be measured in the field!
- 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 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 Analyzer will automatically grab samples from a low flow line or water tank, at scheduled time intervals.
- Save time and money through process optimization with real time OD results
- Option to add automated pH adjustment and dilutions
- Additional parameters can be added on, including pH, conductivity, alkalinity, and ammonia
Case Studies and Resources
Frequently Asked Questions
OD (Oxygen Demand) measures the chemical reactivity of organics by the demand for oxygen, as shown in the diagram below. It can be used as an additional tool in the characterization of NOM (Natural Organic Matter) to predict DBP (Disinfection by-product) formation. This metric also allows for rapid feedback and optimization of coagulation and disinfection dose requirements.
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 oxygen demand 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.
Natural organic matter (NOM) is a critical target for drinking water treatment because it causes a negative effect on water quality by color, taste and odor, and can react with disinfectants to form disinfection by-products (DBP). There are several tools for measuring NOM in source and ground water that include total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), specific UV absorbance (SUVA), and chemical oxygen demand (COD).
UV254 is a water quality test which uses ultraviolet light of 254nm wavelength to measure natural organic matter in water and wastewater.
THMs (trihalomethanes) are disinfection by-products (DBP’s) formed when residual chlorine reacts with elevated levels of naturally occurring organic matter found in water. THMs are present in most drinking water supplies and are dependent on several factors such as type of organic material present and chlorine dosage.
TOC (Total Organic Carbon) is the amount of carbon based organic contaminants in a water system. TOC does not identify each specific organic contaminant present, but rather an absolute quantity of all carbon-bearing molecules. In other words, TOC is a way to measure organic contaminants that may pose a threat to drinking water or wastewater systems.
The primary driver of the peCOD method chemistry is advanced oxidation induced by photocatalysis with Titanium Dioxide (TiO2). Pure TiO2 is only photoactive at wavelengths below 380 nm. This is because a certain amount of light energy is required to bump the electrons around and cause the behaviours 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.
A common benefit of peCOD implementation for this application is optimization of coagulant dosing.
The traditional method up to this point has been consistent dosing based on laboratory testing results (jar testing is a very common method of developing coagulant dosing requirements). They then increase their dosing for events that they know to cause NOM spikes. The problem is they often don’t know the extent of the NOM spikes, so they increase their dosing to what has been deemed as ‘enough’. More often than not this is over-dosing, not really causing downstream issues but incurring more cost than is needed for these events. However, when the extra dose is not enough and they under-dose, NOM gets through and reacts with the disinfection chemicals creating DBPs.
The missing ingredient is knowing when these NOM spikes occur, and to what extent. The events could be anything from seasonal variation based on climate to rapid spikes from storm events, but the benefit of knowing is the same. Plants that have enough funding to do so monitor UV and TOC online, however research has shown that this is not enough. peCOD is another piece of the NOM puzzle and is truly the more important measure when looking at how NOM will react and be affected by treatment. If you know the COD of the NOM coming in and can match it to known dosing requirements, you minimize the possibility of DBPs forming.
The speed and ease of use of the peCOD is also key here, you are placing this knowledge directly in the operators’ hands, rather than having it be a result they wait to get back from an external lab. When they can truly understand the technology and it’s value, it has a secondary effect of getting them more involved with optimizing the treatment processes. We see with numerous cases (mostly in WWTPs at this point) this occurring, where they get the peCOD for measuring one or two points then realizing the benefit it can have through monitoring their whole plant.
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 solutions. 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 that summarizes the advantages and disadvantages of the COD, BOD and TOC methods, and compares them to the PeCOD method.