Removing Salt From Coal Mine Wastewater in a Remote, Wet Area: Full - PowerPoint PPT Presentation

Removing Salt From Coal Mine Wastewater in a Remote, Wet Area: Full Scale Experience Srikanth Muddasani, P.E. Veolia Water Technologies, USA

Project Background • Centralized ZLW treatment facility to handle water from six mine locations • All six mines located within Monongahela River Basin • Regulatory driver = Chlorides to < 218 mg/L • Solid wastes generated are disposed in on-site landfill • Treated effluent is discharged to creek and/or used as frac water 2

Contributing Mine Locations 18” Force Main collects water from 4 mines to the North CENTRALIZED TREATMENT FACILITY 14” Force Main collects water from 2 mines to the South

The Project • Centralized ZLW treatment facility is designed to treat 5 MGD (795 m 3 /h) of mine water • Mine water, pretreated for metals removal where needed, conveyed from six source points to the facility through 32 miles of pipeline • Executed through a Design-Build-Operate contract with Veolia • June 2010 - Request for proposals issued • April 2011 - Project awarded • July 2011 - Construction began • May 2013 - Full operation 4

Design Basis - Influent Mine Water Current Design 1 Parameters Original Design Design Flow, gpm 3500 (795 m3/h) 2026 (460 m3/h) pH, S.U. 5 - 10 7.39 Temperature, deg F 38 – 85 (3 – 30 deg C) 60 – 72 (15-22 deg C) Calcium, mg/L 300 217 Magnesium, mg/L 200 104 Iron, mg/L 150 0.27 Manganese, mg/L 2 0.27 Alkalinity, mg/L CaCO 3 700 - 1200 891 2700 2 Sulfate, mg/L 5,500 1530 2 Chloride, mg/L 1,500 TDS, mg/L 10,000 8600 Silica, mg/L as SiO 2 10 10 Note 1: Average Value based on the data collected between Jun 1st 2014 to Dec 31st 2014 Note 2: Average Value based on the data collected between Aug 20th,2014 to Sep 5th, 2014 5

Effluent Water Quality Requirements Maximum Effluent Parameters Concentration Chlorides, mg/L < 218 < 150 1 TDS, mg/L pH, S.U. 6 to 9 ≥ 50 Minimum Hardness, mg/l as CaCO 3 Note 1: Applied to product water prior to remineralization 6

The Process: Three Primary Components • Raw Water Pretreatment System • Reverse Osmosis System • Thermal Brine Management System 7

Process Overview Primary Objectives 1. Remove TDS and Chlorides 2. Zero Liquid Waste 8

Facility Overview Multimedia Filters Lime & Soda Ash Silos RO Trains Evaporator Crystallizer Raw Water Tank Softening System 1st Stage Clarifier Dewatering Building 9

Chemical Softening System • Multi-stage process • Two aeration tanks for precipitation of metals such as manganese and iron • Crystallization tank for removal of alkalinity and hardness • Draft-tube reactor design • Solids recycle • Reduce chemical consumption • Enhance particle growth and settling characteristics • Conventional circular clarifier design 10

Multimedia Filter System • Removes residual suspended solids in the effluent from upstream clarification and aluminum precipitation processes • Backwash water is returned to the Raw Water Feed Tank • Filtrate is conveyed to the RO System 11

The Process Flow - RO System Reverse Osmosis System RO Feed Tank, followed by Cartridge Filtration • • RO Skids designed to achieve chloride and TDS specifications while operating at a high recovery rate • Five parallel skids, each sized to handle 25% of the design flow, 1 standby Thirty-one pressure vessels per skid, each with seven • seawater RO membrane elements • Permeate flows to Product Water Tank, which also collects distillate from Brine Management System • Prior to discharge, the Product Water Tank effluent is re- mineralized using carbon dioxide and lime water, to protect aquatic life • Discharged to creek, or to a truck loading station for reuse in energy-related operations. • Reject is sent to the thermal Brine Management System 12

Evaporation Evaporator • Concentric falling film unit is divided into two sections with a low concentration side and a high concentration side • Split design to reduce overall power consumption by allowing a portion of the evaporation to occur at a lower boiling point rise than the final concentration • Evaporator operates as a Mechanical Vapor Recompression System • Recycle of hot vapor in the system; minimize auxiliary steam • Distillates from the Evaporator and Crystallizer are pumped through a Feed Preheater for heat transfer to the incoming brine • Heat exchanger for efficient energy utilization 13

Crystallization • Crystallizer includes a vapor body, recirculation pump, and forces circulation heat exchanger • Vapors created by concentrating the slurry in the Crystallizer are recompressed and recirculated through the heater • As the brine concentration increases, the solution becomes supersaturated and salts precipitate, resulting in a brine slurry • A slip stream of the crystallizer slurry is sent to centrifuges for dewatering • The result: Zero Liquid Waste • Dewatered salt cake is disposed in the on-site landfill along with the dewatered sludge from the softening processes 14

Thermal Brine Management System Evaporator Heat Exchanger Crystallizer Crystallizer Distillate Tank 15

Land fill • Dewatered Salt and Softening Sludge is brought separately to onsite landfill • Dewatered Salt contains approximately 90 – 95% in solids concentration and Sludge contains 50 – 65% in solids concentration. • Both passes paint filter press test • Both Salt and Sludge are mixed before applied to landfill • Lechate generated in landfill is collected in storage tank and metered back to thermal system 16

Ancillary Support Systems • Chemical Storage and Feed Systems • Lime Water Preparation System • RO Membrane Clean-in-Place System • Compressed Air System • Electrical and Control Rooms • Laboratory • Communications Equipment • Maintenance and Storage Areas • Personnel Amenities 17

Feed Water Conductivity 18,000 16,000 14,000 12,000 Conductivity (µs/cm) 10,000 8,000 6,000 4,000 Original Design Conductivity = 13,000 µs/cm 2,000 Current Avg Conductivity = 11,180 µs/cm 0 06/01/14 07/06/14 09/16/14 10/21/14 11/25/14 12/31/14 Days Current Feed Conductivity Design Feed Conductivity 18

Product Water Conductivity 200 Product water Cond before Remineralization = 63 µs/cm 180 Final Effluent Discharge Cond = 142 µs/cm 160 140 Conductivity (µs/cm) 120 100 80 60 40 20 0 06/01/14 07/06/14 09/16/14 10/21/14 11/25/14 12/31/14 Days Product Water Cond before Remin Final Eff Discharge Cond 19

Feed Water Chlorides 1650 1600 Chlorides (mg/L) 1550 1500 1450 Current Avg Feed Chlorides = 1,530 mg/l 1400 8/20/14 8/22/14 8/26/14 8/28/14 9/1/14 9/2/14 9/3/14 9/4/14 9/5/14 Days Current Feed Chlorides 20

Final Effluent Chlorides 25.00 20.00 Effluent Chlorides, mg/l 15.00 10.00 5.00 Final Effluent Chlorides = 16 mg/l 0.00 1/1/2014 1/21/2014 2/10/2014 3/2/2014 3/22/2014 4/11/2014 5/1/2014 5/21/2014 6/10/2014 Days 21

Estimated Waste Generation Current Average Waste Design Condition Condition Softening Sludge 6,666 lb/hr (3,030 kg/hr) 2,200 lb/hr (1,000 kg/hr) (on a 100% dry basis) Salt (on a 100% dry basis) 17,500 lb/hr (7,954 kg/hr) 8,710 lb/hr (3,960 kg/hr) Total Waste Generated 24,166 lb/hr (10,984 kg/hr) 10,910 lb/hr (4,960 kg/hr) (on 100% dry basis) Please Note: Waste Estimation for design condition was estimated based on 3500 gpm flow Waste Estimation for Current Average Condition was estimated based on 2026 gpm flow 22

Summary • Treatment process achieves > 99% removal of chlorides using state-of-the-art membrane technology • Energy efficient evaporation and crystallization technology for brine management • Solid waste generated onsite is disposed into onsite landfill and leachate generated at the landfill is sent back to the facility’s thermal treatment process • Since no liquid waste leaves the property, this facility is termed as a “zero liquid waste” (ZLW) facility 23

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