MERCURY, ARSENIC AND SELENIUM IN WASTEWATER GENERATED FROM THE COAL FIRED POWER INDUSTRY

In June 2013 US EPA proposed a new rule “40 CFR Part 423” entitled “Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category”.

The intention of the new rule is the limit the amount of toxic metals, nitrogen and total dissolved solids discharged from power plants to surface water

Main toxic metals of concern are Mercury, Arsenic and Selenium. These bio‐accumulate in the environment harming wildlife and human health

Power Plant Wastewater

Power plants generate various streams of wastewater from different processes and operations. This is dependent on the plant design and how it is operated. Typical wastewater streams include FGD wastewater, fly ash and bottom transport water, flue gas mercury control water, leachates from landfill/surface ponds/coal piles, metal discharge cleaning wastewater and wastewater from gasification.

The streams are typically combined and delivered to surface impoundments to allow settling of solids before direct discharging. Dissolved metals such as Hg, Se and As do not settle within the surface pond and therefore additional water treatment is required on site. Chemical precipitation treatments are reasonably effective for Hg and As. Selenium is more challenging and bioreactors are required to convert oxidised forms of Se to elemental Se

Some typical Results for FGD Wastewater

Online Determination of Mercury, Arsenic and Selenium.

For over 30 years P S Analytical (PSA) has been at the forefront of trace determinations from environmental samples. The determination of Hg, As and Se is performed using cold vapour atomic fluorescence spectroscopy (CV-AFS) or hydride generation atomic fluorescence spectroscopy (HG-AFS). The advantages of both of these analytical techniques have been well documented as they offer outstanding detection performance with easy to use and affordable systems.

More recently the trend towards the use online analysers has grown. This is not surprising given the requirement for continual monitoring, less operator error and generally reduced staff resources.

Application

Wastewater is a challenging sample matrix (especially from the power industry) because of the high dissolved solids content, low analyte concentrations and often complex metal speciation (if this is a requirement). HG-AFS or CV-AFS offers a low cost alternative with low detection limits and minimal interference. Our on board UV photolysis provides the online sample digestion that is required.

P S Analytical has been involved in a number of projects concerning this application. An example of the results obtained comparing the online and laboratory approach are shown below.

Comparison Data for Lab and Online Filtered Wastewater Outlet Sample

For more information regarding these specific applications, please click here.

As well as detailed application notes regarding power industry waste water, PS Analytical applications include environmental samples such as ground water, drinking water, tap water food stuffs (e.g. milk, rice, fish & tea), soils & sludges, clinical samples (e.g. urine, blood and hair), and industrial effluents. 

P S Analytical has a wealth of application information that we are happy to share, click on our application notes page for more information.

Instrumentation from P S Analytical

To perrform a successful analysis, you will need an instrument. P S Analytical offer both onine and laboratory based analytical solutions. Ease of use, reliability and robustness as well as affordable running costs are hallmarks of the P S Analytical brand.   Click on our Product Overview page for more information.

P S Analytical offer a range of online systems for real time analysis, monitoring and management of wastewater discharges. The systems are based upon our successful laboratory product offerings. Mercury and the hydride forming elements are considered highly toxic, environmentally sensitive and they are difficult to remove wastewater discharges. Effective management of treatment systems includes monitoring in real time using online measurements to ensure discharge limits are being achieved. We have supplied many industries including water supply, waste management, petrochemical, food and industrial markets where online monitoring is required, often to ensure discharge limits are being achieved.

Click on our Online Mercury Analyser page for more information.

Click here for our Online Arsenic, Selenium and Antimony Analysers

If you would like any further information on anything from this page, please fill in our Information Request page and will will be happy to send you any information you require.