5 Things you must know about FGD Wastewater

FGD wastewater can be a challenging engineering undertaking.  Operators of coal utilities are under increased scrutiny of their flue-gas desulfurization (FGD) wastewater discharges. Chemical and biological treatment systems have been designed for removing target analytes below the regulatory limits with some success. However, many facilities are facing issues with selenium and other trace metals.

Frontier has been involved with the development of trace metal analytical solutions for coal utilities for over a decade.   The complex nature of FGD wastewater (high TDS, high chloride, and volatile met¬al species) poses difficulties for accurate analysis of trace metals. Several inter-laboratory studies have yielded very different results between laboratories.  With our extensive experience dealing with FGD wastewater we have come across five major things that every utility operator must know before using an analytical service provider for FGD wastewater measurements.

1. Find out what analytical techniques the laboratory intends to use. Typical techniques used are inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), or inductively coupled plasma mass spectrometry utilizing collision or dynamic reaction cells (ICP-DRC-MS).  ICP-AES is a less sensitive method that will have difficulties measuring the trace elements in FGD wastewater.  ICP-MS is a much more sensitive method but suffers from high bias associated with spectral interferences present in FGD wastewater.  ICP-DRC-MS is the best technique commercially available to measure FGD wastewater.
2. Ask what there detection limits are. Although ICP-DRC-MS techniques are the best available, high TDS present in FGD wastewater will necessitate significant dilutions of the sample prior to analysis.  It is critical that the analytical technique used can accurately measure trace elements present in the sample.
3. When asking for detection limits make sure they can provide you with a minimum detection limit (MDL) and a reporting limit. The MDL is a statistical concentration only and does not guarantee accuracy at that limit.  Ensure that the reporting limits are sufficient enough to measure the trace elements in each sample at the necessary dilution.  Do not rely on reported concentrations at the MDL or below the reporting limit.
4. Ask how they optimize their collision or reaction cell for FGD wastewater analysis. Typical instrumental optimization procedures used do not account for the possible interferences present in FGD wastewater.  Make sure that the optimization procedure used by the laboratory takes into account the specific nature of FGS wastewater.
5. The most important is to ask the laboratory how much experience they have optimizing and performing FGD wastewater analysis. Not all samples, instrumentation, and operators are the same and it is very important that the laboratory has the expertise to effectively analyze FGD wastewater and provide you with the highest quality and accurate data possible.