How Are Optical Filters Used in Water Analysis?

Monitoring organics continuously provides instantaneous water quality data that is vital for several of the most common water and wastewater treatment applications. Originally, research focused on the modeling of spectral data and water parameters by a single wavelength method. Bandpass filters centered at 254nm have been used for their sensitivity to total organic carbon (TOC), a measure of the total amount of carbon in organic compounds in pure water and aqueous systems. Meanwhile, bandpass filters centered at 280nm are chosen for the biochemical oxygen demand (BOD). Biochemical oxygen demand represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present) conditions at a specified temperature.

Later on, pairs of wavelengths were introduced as sensitivity references to eliminate the influences of turbidity and particles in the water sample. The 254nm bandpass filter has been paired with the 350nm bandpass filter and also has been paired with the 580nm bandpass filter in order to measure organic pollution in water samples. Likewise, the 280nm bandpass filter has been paired with the 309nm bandpass filter to detect the presence of resorcinol and hydroquinone in laboratory wastewater using a double system double wavelength fluorescence microscopy.

In addition to the specific bandpass filters previously described, Andover Corporation can also supply high-quality off-the-shelf optical components with passbands, edge filters, and dichroic filters covering all of these center wavelengths and covering all of these wavelength ranges.