{"id":2992,"date":"2021-11-17T19:15:57","date_gmt":"2021-11-17T19:15:57","guid":{"rendered":"https:\/\/sci-monitoring-cn.com\/?p=2992"},"modified":"2021-11-18T16:45:26","modified_gmt":"2021-11-18T16:45:26","slug":"selenium-measurement-at-flue-gas-desulfurization-wastewater-treatment-pilot-plant","status":"publish","type":"post","link":"https:\/\/sci-monitoring-cn.com\/selenium-measurement-at-flue-gas-desulfurization-wastewater-treatment-pilot-plant\/","title":{"rendered":"Selenium Measurement At Flue Gas Desulfurization Wastewater Treatment Pilot Plant"},"content":{"rendered":"
The U.S. EPA, under the Clean Water Act, establishes Effluent Limitation Guidelines (ELG). On August 31, 2020 the EPA issued a finalized version to the Stream Electric Power Generating category (40 CFR Part 423). This finalized version added numerical limitations on several pollutants and waste streams. One waste stream of interest is flue gas desulfurization (FGD) wastewater. FGD waste streams received numerical limits on total arsenic (daily = 18 ppb (parts per billion), monthly = 8 ppb), total mercury (daily = 103 ppt (parts per trillion), monthly = 34 ppt), total selenium (daily = 70 ppb, monthly 29 ppb), nitrate\/nitrite (daily = 4 ppm (parts per million), monthly = 3 ppm), total suspended solids (daily = 100 ppm, monthly = 30 ppm) and oil and grease (daily = 20 ppm, monthly = 15 ppm). These numerical limits are based on Best Available Technology Economically Achievable (BAT) using chemical precipitation followed by low hydraulic residence time biological reduction.<\/p>
Electric generating utilities have a broad compliance deadline from as soon as incorporated into permit to December 31, 2028, depending on the specific facility\u2019s sub-category.<\/p>
This application focuses on measuring total selenium in the FGD waste stream, using Cooper Environmental\u2019s Xact 920, a continuous multi-metal monitor based-on energy dispersive X-ray fluorescence (XRF), as an alternative to typical laboratory methods.<\/p>
Typical selenium sampling and analysis is conducted by collecting manual grab samples and sending to a laboratory for inductively coupled plasma mass spectrometry (ICP-MS) analysis, utilizing any number of interference reduction methods such as triple quadruple or collision cell techniques. This analysis is expensive, and the plant operator doesn\u2019t receive results for days to weeks, usually after an upset event has already occurred. The Xact 920 provides continuous online results within hours of an event happening, allowing quick adjustments to the treatment process, including adjustments to ferric chloride and bioreactor nutrient dosage. <\/p>
Data presented in this paper was collected over an eight-month demonstration in 2020, with the Xact 920 installed at a pilot scale FGD wastewater treatment plant, capable of treating up to 50 gpm. The general treatment process included typical Phys\/Chem followed by biological treatment and ultrafiltration. The Xact 920 collected samples in a continuous online configuration providing total selenium concentration measurements every hour. Periodic grab samples were collected thoughout the demonstration and sent to a laboratory for total selenium analysis using triple quadruple ICP-MS.<\/p>
The Xact 920 was configured to sample both the bioreactor effluent (Path A) and the Phys\/Chem effluent (bioreactor influent) (Path B), this configuration is show in Figure 1.<\/p>