Nanotechnology Provides Alternative Method to Dichromate Based COD Analysis
Nanotechnologies hold a lot of promise for improving the world and offering revolutionary advancements over traditional technologies that have not changed for decades, including for water quality analysis.
Laboratory staff have known for a long time about the potential negative health impacts associated with Chemical Oxygen Demand (COD) testing using the traditional dichromate method, however the determination of COD for the analysis of wastewater is required under the EU Urban Waste Water Directive 91/271 and no viable safe, user friendly alternative method existed.
The traditional COD analysis approach has been used for decades and is based on the use of potassium dichromate, one of the reagents necessary for dichromate COD analysis. Dichromate is listed as a “Substance of Very High Concern” on the Annex XIV list of the European Union’s REACH regulation. The European Chemical Agency has found potassium dichromate to be carcinogenic, mutagenic and a reproductive toxin. These properties make the dichromate COD method potentially unsafe for the analyst, the public and the environment. As a result, starting September 2017, producers of COD tests will need authorisation from the European Union to sell these tests, which creates demand uncertainty for end users.
The challenge has been to identify an alternative COD analysis method that overcomes the limitations of the traditional dichromate method, and a new nanotechnology based approach called PeCOD® from MANTECH is the first alternative method to be adopted by leading global regulatory agencies.
The core of the technology is a nanotechnology based sensor, which consists of a UV-activated nanoparticale TiO2 (titanium dioxide) photocatalyst. The high electrochemical potential of the TiO2 gives it a substantial advantage over the modest chemical potential generated by the dichromate method. The PeCOD® approach measures photocurrent charge originating from the oxidation of organic species contained in a sample. The result is that the user obtains a very accurate measurement of organic pollution, in less than 15 minutes, with no use of dichromate or other hazardous chemicals.
Regulatory approvals are conservative in the water industry, as they should be since incorrect decisions can have serious impacts for the environment and public health. The nanotechnology based COD method has been methodically validated by the Ontario Ministry of the Environment and Climate Change (ON MOECC) in Canada. After 20 months of validation testing, the ON MOECC released official method E3515 in February 2014, which replaces the standard dichromate methods previously used within the regulatory agency. A comparison between the standard dichromate method and the PeCOD® method in terms of performance was provided in a validation report. Method E3515 eliminates environmentally hazardous waste and the use of harmful and toxic reagents. The MOECC now utilizes two PeCOD based units and relies on them for analysis of samples for enforcement, compliance and legal purposes. The technology validation is also now underway by the Dutch RWS Laboratory.
“The Laboratory Services Branch of the Ontario Ministry of the Environment and Climate Change supports the development of new green technology. The new approach for measuring chemical oxygen demand by photo-electrochemical measurement eliminates the use of corrosive (H2SO4), carcinogenic (K2Cr2O7), toxic (HgSO4) and irritant (Ag2SO4) chemicals for the analysis of chemical oxygen demand. Analysis time was significantly reduced and the method detection limit was 1 mg/L O2.” commented Vasile Furdui, Ph.D. Research Scientist, Ministry of the Environment and Climate Change.
The PeCOD(r) method also provides a significant breakthrough in terms of reducing COD sample analysis time to 15 minutes or less, vs ~3 hours for the traditional dichromate test. This rapid analysis can have a significant impact for wastewater facility operators in terms of understanding incoming COD levels, optimizing plant operations and monitoring discharge effluent for regulatory compliance.
“We moved from the COD vials to the PeCOD® primarily because it allowed us to run our process more efficiently and further adjustments to our process could be made up to ten times a day. With the COD vials, only 3 or 4 adjustments could be made. This increase in efficiency and turnaround time in sample analysis has easily paid for the system, not to mention the added benefit that we’re no longer using carcinogenic chemicals to test for COD. We have also seen a reduction in cost of consumables and waste disposal.” said Mark Westhorpe, Analytical Shift Leader, Vertellus Specialty Materials based in the United Kingdom.
The nanotechnology based approach is currently deployed at nearly 100 sites around the world and used in a variety of sectors including regulatory agencies, academic laboratories, industrial facilities, food and beverage producers and municipal water treatment facilities. Beyond the COD analysis capabilities, the application of the technology is being expanded to BOD5 correlation, and for COD testing of potable water sources where early technology applications have shown that with PeCOD monitoring, removal of Natural Organic Matter (NOM) is approximately 3.5x greater vs the use of traditional surrogates analysis methods such as TOC, DOC and UV254 (Application of Photoelectrochemical Demand to Drinking Water Analysis, Stoddart & Gagnon | http://dx.doi.org/10.5942/jawwa.2014.106.0106).
For more information on the PeCOD analyser click here