Chemical Oxygen Demand (COD) is used as a measure of organic pollutants in water. In wastewater treatment, it indicates the efficacy of a treatment process and is expressed in milligrams per litre (mg/L) or parts per million (ppm). Removing certain fractions of COD in waste streams can be particularly challenging, especially to levels safe for discharge to the environment.
The need for tertiary (Advanced) water treatment
Regulations such as the Water Framework Directive in the EU, the Environmental Protection Agency’s Clean Water Act in the US and the directives of the Ministry of Environmental Protection in China stipulate strict limits of COD for water to be discharged to sewers or the environment. Typically, the COD concentrations are from <120 ppm in the EU to < 50 ppm in China. Failure to comply with these regulations can result in a loss of permit, operational downtime and fines for the water-discharging entity. Treating wastewater to a standard fit for discharge to sewers or for reuse demonstrates Good Manufacturing Practice and Corporate Social Responsibility. Yet achieving proper standards for disposal has been impossible with just one water treatment method, due to the ubiquitous presence of recalcitrant COD and persistent micro-pollutants in wastewater. The resultant need for combinations of technologies generates spiking water-treatment costs and a complex treatment train to maintain.
Existing advanced treatment solutions
Primary and secondary wastewater treatment technologies typically remove 75-85% of COD, leaving the hard-to-treat (recalcitrant) COD behind. Popular technologies such as UV, Ozone, Reverse Osmosis and Activated Carbon can be deployed as an advanced or tertiary treatment to reduce the remaining recalcitrant COD for regulatory compliance. However, each of these technologies has its own drawbacks, including the generation of secondary waste streams that need further disposal, considerable maintenance demands and costs, and the management of pH and/or turbidity for effective operation. Add to that the application of chemical dosing as part of most advanced treatment methods, coupled with the typically high-energy requirements for achieving relatively small changes in the quality of the treated waste water, and most existing tertiary treatment solutions prove expensive, ecologically-unsound and complicated to maintain.
Arvia's revolutionary system
Arvia’s patented advanced Organics Destruction Cell (ODC) system combines adsorption and electrochemical oxidation within a single unit. The system uses no chemicals during operation and releases none at the end of the process. Arvia's ODC destroys organic contaminants without any by-product formation or sludge generation. The patented adsorbent it uses, Nyex, is regenerated in-situ, allowing for a continuous process. Furthermore, while UV, Ozone, Reverse Osmosis and other Advanced Oxidation Processes treat the whole volume of wastewater, resulting in high energy costs for low levels of organics removal, Arvia's ODC technology applies targeted oxidation. It uses energy in proportion to the waste stream's organic load, targeting the organic concentration regardless of water volume. Destroying only the organics in this way results in much lower operation costs. Moreover, Arvia ODC's simple and modular design enables its integration into existing treatment plants. It targets specific pain points without causing disruption to existing processes. Last but not least, the Arvia ODC system requires little or no maintenance and can operate unmanned 24/7. For the first time, water-intensive industries such as food, beverage, pharmaceutical and chemical manufacturers can avoid high trucking and disposal costs, overcome water reuse limitations, and be ready to face increasingly tougher regulations.