Treatment of saline streams: removal of precipitable salts Case study Denieul M.-P., Mauchauffee S., Le Calvez G., De Laval A., Coste M.

Transcription

1 Treatment of saline streams: removal of precipitable salts Case study Denieul M.-P., Mauchauffee S., Le Calvez G., De Laval A., Coste M. Veolia Environnement Recherche & Innovation 16/07/2012) Veolia Environnement Recherche & Innovation

2 Content 1. Context and stake 2. Advanced precipitation processes: High rate softening 1. Precipitation: Mechanism and bibliography 2. High rate softening: Multiflo TM -softening 3. Application of Multiflo-softening to Pulp&Paper waste water 1. Downstream aerobic treatment 2. Downstream anaerobic treatment 4. Conclusions 16/07/2012 Veolia Environnement Recherche & Innovation 2

3 1 Context and Stakes Pulp& Paper industry 16/07/2012) Veolia Environnement Recherche & Innovation

4 Water reuse in the Pulp&Paper sector Lot of effort used to water saving and closing water circuits However: Number of problems around the removal of substances not solved yet; Further closing the water cycle causes other problems Challenges for water re-use in P&P industry: Elimination of residual (soluble) COD and BOD 3 ry biological treatment Membrane processes NF Ozonation Removal of residual stickies, suspended solids Filtration processes 3FM, membrane processes (NF) Treatment of concentrate streams, containing calcium, sulphate, chloride, organics Salt accumulation Corrosion Scaling in pipes, showers (CaCO 3 ) Precipitable salts Removal of CaCO 3 Softening Membrane processes Evapo-concentration Non precipitable salts 16/07/2012 Veolia Environnement Recherche & Innovation 4

5 2 Advanced precipitation processes: High rate softening 16/07/2012) Veolia Environnement Recherche & Innovation

6 Context & Stakes of Advanced Precipitation Processes in the treatment of industrial waste waters The physicochemical treatment of aqueous by-product streams from industrial operations Typically involves chemical precipitation of the contaminants viaacid-base neutralization (or other means) followed by separation of the solids from the solution; Acid waste neutralization, metal removal, Softening(Softened water production, WW Re-Use, pre-treatment ) Industrial water treatment operators daily face problems in de-alkalization / precipitation processes Why? Precipitation reaction = Core of the chemical engineering in such processes Generally, a very unstable mechanism when poor homogenization and dispersion of the reagents are applied in the reactor. Lower removal efficiency (hydraulic short-cut, long induction time) Over-consumption of reagents (poor dispersion around the reagent input) Scaling on walls and pipes / residual TSS in treated water (post precipitation) Low density Sludge presenting a high moisture rate (nucleation >>> growth) Size, shape and density of the precipitated particles can have a significant impact on sludge rheology, settling rate and dewatering performance. 16/07/2012 Veolia Environnement Recherche & Innovation 6

7 High rate softening: Multiflo -softening Chemical precipitation of hardness, alkalinity, and other constituents (e.g., heavy metals) by the addition of lime, carbonate ions, metallic salts and polymer Combination within a single treatment line of: anenhancedprecipitationreactorturbomix TM (drafttube+custommixer): improvesreactionkineticsof chemicalsinputs and homogenisationof solidparticles, minimizationof energyinput necessaryto avoidbreakageof particlesand limitation of energy consumption a Sludge recirculation system Total crystal surface area increased by increasing solid concentration a conventional solid/liquid separation stage(lamellar settler) Actiflo Softener 60 80m.h -1 Multiflo Softener 20 30m.h -1 Turbomix reactor Conventional precipitation softening 2 6m.h -1 Multiflo softening Compactness = one of the main advantages 16/07/2012 Veolia Environnement Recherche & Innovation 7

8 3 Application of high rate softening to Pulp & Paper effluents Removal of CaCO 3 before membrane processes to prevent scaling 16/07/2012) Veolia Environnement Recherche & Innovation

9 Application of Mutiflo TM -softening to the removal of CaCO 3 before membrane processes Two case studies: 1 st treatment line Physico-chemical technologies for 3 ary treatment: AOP (O 3 ) Water to be re-used? AOP (O 3 ) Can be recycled into Anaerobic??? Anaerobic Aerobic 3FM Industrial WWTP Evapo Water to be re-used? Multiflo softening NF Final waste Water to be re-used? 2 nd treatment line Biological & tertiary treatment with internal recycling of concentrates AOP (O 3 ) Impact of re-injection??? Water to be re-used? AOP (O 3 ) Anaerobic Multiflo softening MBR Evapo Water to be re-used? NF Final waste Water to be 16/07/2012 Veolia Environnement Recherche & Innovation re-used? 9

10 Multiflo TM -softening on site unit Reaction tanks Lime input to ph target Coagulant Flocculant Feed Turbomix reactor Treated water Lamellar settler Sludge recirculation X : 1 Sludge extraction SOFTENING Removal of carbonate before membrane process Addition of calcium chloride and lime: - Calcium chloride Calcium contribution - Lime (Ca(OH) 2 ) To reach a basic ph to allow CaCO 3 precipitation 16/07/2012 Veolia Environnement Recherche & Innovation 10

11 3.1 Case 1: Softening before NF process 16/07/2012) Veolia Environnement Recherche & Innovation

12 Case 1: Multiflo TM -softening upstream NFprocess Treatment of 3FM filtrate: Final waste Evapo Water to be reused? paper mill Anaerobic Aerobic 3FM Multiflo TM softening NF Water to be reused? Industrial WWTP CaCO 3 scaling - Antiscalant -HCl Process conditions: Flow rate: 125 L/h Lime injection ph = 10.5 Chemical input: Mineral coagulant (40 ppm) Flocculant: 0.4 ppm of polymer Sludge recirculation ratio: X 1 : 1(kg of dry solid recirculated / kg of dry solid produced by the reaction) 16/07/2012 Veolia Environnement Recherche & Innovation 12

13 Multiflo TM -softening -Results upstream NFprocess Ca removal Alkalinity removal 16/07/2012 Veolia Environnement Recherche & Innovation 13

14 Multiflo TM -softening -Results upstream NF process Impact on turbidity Impact on COD Residual turbidity after softening = Residual of Abatement of the initial turbidity + Abatement of SS formed in the reactor (2 g/l) during the softening process Multiflo-softening Very good performances regarding CaCO 3 removal upstream NF process 16/07/2012 Veolia Environnement Recherche & Innovation 14

15 Impact of softening on downstream NF process Benefits of low calcium concentration on the NF process: Decrease of the antiscalant consumption Reduction of hydrochloric dosis during NF Increaseof NF conversion rate up to 80% Permeate fulfills the highest quality requirements for re-use (white paper grade production process): Conductivity = 113 ±16 µs/cm Hardness < 1 dh COD < 9 mgo 2 /L Cl - < 33 mg/l Ca < 7 mg/l SAC 436, 425, 620 < 0.4 m -1 (colorless) Moreover: Tiny amount of used HCl NF concentrates can be treated by evapoconcentration Absence of scaling is as well beneficial for the maintenance of intermediate material (pumps, pipes ) Recommendations for implementation: TSS after softening < 14 mg/l Slight release of particulate matter Continuous UF pre-filtration system before NF recommended in this configuration 16/07/2012 Veolia Environnement Recherche & Innovation 15

16 3.2 Case 2: Softening before MBR process 16/07/2012) Veolia Environnement Recherche & Innovation

17 Case 2: Multiflo TM -softening upstream MBR process Treatment of Anaerobic effluent: Evapo Final waste Water to be reused? paper mill Anaerobic Multiflo TM softening MBR NF Water to be reused? COD 4 x COD aerobic CaCO 3 scaling -Need of frequent cleanings - Operation not reliable Impact of organic matter on softening process? Process conditions: Flow rate: 250 L/h Lime injection ph = 10.5 Chemical input: Organic coagulant (10-13 ppm) Flocculant: 0.4 ppm of polymer Sludge recirculation ratio: X 2 : 1 16/07/2012 Veolia Environnement Recherche & Innovation 17

18 Multiflo TM -softening -Results upstream MBR process Ca removal Alkalinity removal NO impact of soluble organic matter 16/07/2012 Veolia Environnement Recherche & Innovation 18

19 Impact of softening on downstream MBR process Multiflo-softening Very good performances regarding CaCO 3 removal upstream MBR process Benefits of low calcium concentration at the inlet of MBR: Better stabilization of the membrane process Prevention of scaling by CaCO 3 Significant extension of cleaning intervals MBR operation reliable Moreover: TSS level ~ 150 mg/l in the softening outlet MBR can be directly implemented without intermediate pre-filtration 16/07/2012 Veolia Environnement Recherche & Innovation 19

20 4 Conclusions 16/07/2012) Veolia Environnement Recherche & Innovation

21 Conclusions AquaFit4Use project aims at developing innovative treatment trains to close the water loop in hig water consumer industrial sectors In the Pulp&Paper sector, removal of calcium content: One of the major concerns when closing water loop in order to prevent scaling of pipes and showers; Can be as well a major problem to implement a membrane process after biological treatment process when speaking of recycling water Multiflo TM -softening, an advanced precipitation technology developed by Veolia Water STI, proved to be well adapted to remove calcium before membrane processes 95-98% removal of Ca both on 3FM filtrate (aerobic ) and Anaerobic effluent No impact of soluble organic matter on the precipitation process (anaerobic effluent) Reliability of process performances regarding impact of waste waters variations 16/07/2012 Veolia Environnement Recherche & Innovation 21

22 Conclusions and perspectives Impact of softening on downstream membrane processes: Prevention of scaling on membranes Reliability of membrane processes and of their operation NF process: conversion rate and use of chemicals Absence of scaling as well beneficiary for pipes and other utilities MBR process: cleaning frequencies and thus use of chemicals MBR becomes economically viable!!!importance of tertiary treatments when closing the water loop for water re-use!!! AquaFit4Use = 1 st application of Multiflo-softening on anaerobic effluent in the Pulp & Paper sector!!! 16/07/2012 Veolia Environnement Recherche & Innovation 22

23 THANK YOU FOR YOUR ATTENTION Special thanks to: 16/07/2012 Veolia Environnement Recherche & Innovation 23