2019-11-27_PERMIT FILE - M2019058 (10)

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Environmental Impacts of Water Treatment Chemicals at Industrial Sand Mines IN BARR treatment industry has established standards(NSF/ANSI Control Volume 60)that limit DADMAC monomer in drinking water to 50 - ug/L,or 100 times the de facto standard for acrylamide.1 Wet Sand(103 gpm) 45 gmp I , Because DADMAC has no known human health concerns I with I ; rines Sand associated with it,there is less published data and little slurry to warn n 1 8 � risk analysis concerning its fate in the environment. Mine Pit ; Process ; Acrylamide ^ r— Makeup ; mining process water Monomer I Water (155 gpm) ; Most industrial sand mines utilize a wash water loop, , similar to the one depicted in Figure 1(below). Water i Clarifier Reservoir from a reservoir(augmented with makeup water, usually ; , from a groundwater source) is used to slurry raw sand. `7 This slurry is processed by a series of screens,scalpers, and density separators to separate the sand by particle , Underflow � , size. Fines are generally returned to the mine pit or `------------ ----------'---------------= - f— Belt Press filter Cake stockpiled until used for site reclamation,while sized I �'(7gpm) sand is transported to the dry plant for further process- DADMAC ing. Monomer i Polyacrylamide anionic flocculants are used to enhance Figure 1. Control volume used in estimating the steady- settling of solids in the clarifier,or thickener, associated state DADMAC monomer concentration in the water with the process.The clarifier produces an underflow, leaving the sand wash loop. which is essentially a thick mud. Some facilities use a belt tion of the process water that overflows the clarifier and press to convert this mud into a solid or filter cake,which is recycled in the process. offers easier disposal. It is common for facilities that use a belt press to use a polydimethyldiallyammonium chlo- The water-phase concentrations of acrylamide monomer ride (polyDADMAC)cationic coagulant to enhance the within each water reservoir at a typical wash plant facility performance of the belt press. (see Figure 1) can be characterized by the following mass fate of polyacrylamide balance equation: The acrylamide monomer is highly soluble in water, is Accumulation=Incoming -Outgoing- Biodegradation biodegradable under aerobic and anaerobic conditions, Incoming and has poor adsorption to minerals and organic mat- The incoming rate of acrylamide monomer is directly ter.'The fate of this residual acrylamide monomer in the related to the feed rate of the polyacrylamide flocculant environment is discussed later in this document. added to the clarifier(see Figure 1).The Wisconsin DNR, as part of the Nonmetallic Mining Operations General Steady-State Kinetic Model of Acrylamide Monomer Permit, requires permitted facilities to record on a concentration in Process Water and Quarry Pit monthly basis all water treatment additives and to report The acrylamide monomer is highly soluble in water, and this amount annually.The concentration of the acryl- has poor adsorption to minerals and organic matter. amide monomer in polyacrylamide flocculants is limited Thus,the concentration of acrylamide that will exit the to 500 ppm. clarifier in the underflow slurry will equal the concentra- Biodegradation 3 www.nsf.org/newsroom Acrylamide monomer is biodegradable. Biodegradation pdf/NSFFactSheetPolyelectrolytes.pdf rates vary with the availability of oxygen,temperature, concentration of acrylamide monomer, concentration of 4 EPA. 1994.Chemical Summary for Acrylamide.http:// capable microorganisms,and whether the capable www.epa.gov/chemfact/s—acryla.txt Page 3 ® Barr Engineering Co.2013 Keenesburg No. 2 Mine_112 Reclamation Operation—November 22, 2019