The quest to identify the ideal measure of water quality is an evolving saga and involves various analyses, such as dissolved oxygen, total organic carbon (TOC), chemical oxygen demand (COD) and biological oxygen demand (BOD). Developing reliable, easy-to-use instrumentation for such measurements is a challenge, but one that makers of COD analyzers are increasingly up to meeting. The market for COD analyzers is still quite small and fragmented but has considerable potential to develop into a broader market.

The COD of a sample provides a measure of nearly all organic compounds and therefore is an excellent measure of water quality. However, the practical measurement of COD has traditionally been difficult because of the need to find reagents, catalysts and methods that will reliably oxidize all organic compounds, as well as the fact that a standard manual lab method can take several hours—although this is still much more rapid and less variable than BOD. In contrast to BOD, TOC analysis has been more conducive to the development of both benchtop and online analyzers that can perform such measurements in a matter of minutes. Although TOC cannot be exactly correlated to COD, it provides an adequate measure of water quality that TOC analyzers have become a more common technique for periodic monitoring than COD or BOD tests.

The earliest COD methods were manual benchtop techniques that were based around potassium permanganate, but many compounds were not easily oxidizable using the reagent. Of more recently developed methods, the use of potassium dichromate as the primary reagent provides a better oxidizing agent that is also relatively inexpensive. But both of these methods involve the use of reagents that result in the need for disposal of hazardous materials, including mercury in some cases.

A number of vendors have developed online analyzers based on various reagent COD methods, but none have become widely popular. Some vendors now offer direct-UV analyzers that can be modeled to monitor COD in water that has consistent concentrations and types of oxidation compounds. Also, the development of electrochemical and photoelectrochemical oxidation methods has reduced or eliminated the use of hazardous reagents.

Most of the vendors involved in the COD analyzer market are small or midsize organizations. Endress+Hauser is one of the only large vendors in the area. None of the firms significantly involved in the COD analyzer market is based in North America. The total market for COD analyzers in 2010 was only about $10 million. The majority of COD analysis is still performed using manual lab methods. A number of the newer analyzers have the potential to drive growth in demand. Regulatory approval of such methods is the largest barrier to more widespread use of COD analyzers.

COD Analyzers at a Glance:

Leading Suppliers

• Endress+Hauser

• LAR Process Analyzers

• Aqua Diagnostic

Largest Markets

• Wastewater

• Industrial Effluent

• Surface Water

Instrument Cost

• $10,000–$30,000