Treatment of saline streams: removal of non-precipitable salts Case studies

Transcription

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

2 1 Context and Stakes 16/07/2012) Veolia Environnement Recherche & Innovation

3 Context and Stakes Aquafit4use European project objective: to close the water circuit in the main water consuming industries by treating their wastewater to produce water they can reuse. One of the main issues: concentrated streams Often considered as wastes Two different origins Directly produced by the company process Or produced from the waste water treatment (removal of substances not solved) 1 common point a strong saline load with precipitable or non-precipitable salts 2 objectives: Reduction of saline load in closed loops Reduction of final wastes 16/07/2012 Veolia Environnement Recherche & Innovation 3

4 Context and stakes Concentrated streams characterization: High COD content High conductivity high salts content: Precipitable: which can be eliminated in solid form by chemical precipitation (neutralization, metal precipitation, softening ) Non-precipitable: which can t be treated by precipitation membrane treatment? Thermal treatment? Concentrated streams with non-precipitablesalts Reduction of final waste Reduction of saline load elimination of the non-precipitable salts Treatment by thermal way with evapoconcentration technologies 16/07/2012 Veolia Environnement Recherche & Innovation 4

5 2 Evapoconcentration Evapoconcentration principle & technologies Pilot used for the case studies 16/07/2012) Veolia Environnement Recherche & Innovation

6 Evapo-concentration Evapoconcentration principle Distillate Steam Feed Concentrate Boiling of effluents under vacuum Lower boiling temperature Heat transfer with a heat pump, a compressor or steam boiler Evapoconcentration technologies Rising Film Ebullition = 85 C MVR ( T 25 C) Vertical Falling Film Ebullition = 98 C MVR or thermo-compressor ( T 5-7 C) Forced Circulation Ebullition = 37 C Heat pump ( T 15 C) Scraped Surface Ebullition = 37 C Heat pump ( T 15 C) 16/07/2012 Veolia Environnement Recherche & Innovation

7 Evaporators Rising Film Less energy consuming VCF limited by the concentration in chlorides (8-9 g/l) and the dry matter content (15-30%) in the final concentrate Ebullition at 85 C 580 mbar (Roots) MVR ( T ~ 25 C) Distillate flow = 20 L/h Scraped surface Overconcentration Used for «small» fluxes/volumes More corrosion resistant (UB6) (up to 45 g/l in chloride) Higher dry matter content (30 to 60%) More energy consuming Ebullition at 37 C 50 mbar (hydro-ejector) Heat Pump ( T ~ 15 C) Distillate flow = 7 L/h Treatment in 2 steps: First concentration with the rising film evaporator Second step or over-concentration with the scraped surface 16/07/2012 Veolia Environnement Recherche & Innovation 7

8 3 Case Study 1: textile sector Presentation Treatment of the concentrated streams produced on site Global treatment 16/07/2012) Veolia Environnement Recherche & Innovation

9 Textile sector On-site separation of concentrated and low-concentrated streams 3 concentrated streams produced on site by textile production and 1 coming from low-concentrated streams treatment by nanofiltration Stenters Impregnation Bleaching Foulard Discharge (m 3 /year) 332* 290* 253* ph * 12.3 C (ms/cm) * 55.1 Dry matter at 105 C (%) tcod (mg O 2 /L) * Cl - (mg/l) SO 4 2- (mg/l) < Ca 2+ (mg/l) * Company analyses NF concentrates /07/2012 Veolia Environnement Recherche & Innovation Impregnation bleaching: high hydrogen peroxide content can t be treated by evapoconcentration without pre-treatment Two combinations of streams for evapoconcentration: -Mix of concentrated streams produced on site: Stenters and Foulard - Mix of all the concentrated streams: Stenters, Foulard and NF concentrate 46

10 Treatment of mix Stenters/Foulard Treatment of two concentrated streams mixed in a ratio equal to their flows on site Evapoconcentration only carried out with scraped surface evaporator No addition of chemical products during evapoconcentration Final volumic concentration factor (VCF) = 5 Based on ph, chloride concentration and dry matter content 16/07/2012 Veolia Environnement Recherche & Innovation 10

11 Treatment of mix Stenters/Foulard 16/07/2012 Veolia Environnement Recherche & Innovation 11

12 Treatment of mix Stenters/Foulard Concentrate: High viscosity final VCF can t be increased Some clogging need for using chemical product for evaporator washing Distillate: High turbidity Slightly coloured (purple) Feed Distillate Concentrate COD: higher than quality requirements Distillate: necessity of a complementary treatment before its re-use AOP treatment (with low-concentrated streams) 16/07/2012 Veolia Environnement Recherche & Innovation 12

13 Treatment of all the concentrated streams Stenters, Foulard and concentrates coming from nanofiltration of low-concentrated streams Mixed in proportions corresponding to on-site flux (1/1/100) Evapoconcentration only carried out with scraped surface evaporator No addition of chemical products during evapoconcentration Final volumic concentration factor (VCF) = 45 Based on ph, chloride concentration and dry matter content 16/07/2012 Veolia Environnement Recherche & Innovation 13

14 Treatment of all the concentrated streams 16/07/2012 Veolia Environnement Recherche & Innovation 14

15 Treatment of all the concentrated streams Concentrate: final VCF can be increased to 50 Amount of waste to be disposed off = 0.4% of the global treated WW Distillate: Feed Distillate in time Concentrate Uncoloured Respects all the quality requirements: Absorbance stays in acceptable range No need for further tertiary treatment 16/07/2012 Veolia Environnement Recherche & Innovation 15

16 Conclusion Evapoconcentration: technology validated For concentrated streams produced on site For those coming from low-concentrated treatment by nanofiltration Concentrated streams produced on site Further tertiary treatment of distillate necessary Waste to be disposed off: divided by 5 Global treatment of concentrated streams Distillate fulfilled water quality criteria Final VCF = 50 Waste to be disposed off = 0.4% of the global treated wastewater 16/07/2012 Veolia Environnement Recherche & Innovation 16

17 4 Case Study 2: paper sector Presentation Results Conclusion 16/07/2012) Veolia Environnement Recherche & Innovation

18 Evapoconcentration in paper sector Treatment of NF concentrates: Removal of salts Production of water to be re-used Reduction of final volume of wastes to be disposed off 2 steps: MVR evaporator Heat pump evaporator (overconcentration) Tested on NF concentrates coming from two different treatment train: Train 1: WWTP 3FM Multiflo Nanofiltration Train 2: Anaerobic process Multiflo MBR Nanofiltration 16/07/2012 Veolia Environnement Recherche & Innovation 18

19 Results obtained on Train 1 Global VCF = 40.4 VCF = 8.6 VCF = 4.7 Lab-scale simulation ph 7,5 C (ms/cm) 4,5 Dry matter (105 C - %) 0,3 scod (mgo 2 /L) 285 Cl (mg/l) 1120 Ca (mg/l) 18,1 TAC (mgcaco 3 /L) 213 SO 4 (mg/l) 241 Abs (436nm - m -1 ) 1,3 ph 7,2 C (ms/cm) 0,022 Dry matter (105 C - %) - scod (mgo 2 /L) < 15 Cl (mg/l) < 5 Ca (mg/l) 0,23 TAC (mgcaco 3 /L) 0,2 SO 4 (mg/l) < 5 Abs (436nm - m -1 ) - ph 6,9 C (ms/cm) 0,006 Dry matter (105 C - %) - scod (mgo 2 /L) 18,6 Cl (mg/l) < 5 Ca (mg/l) < 0,05 TAC (mgcaco 3 /L) - SO 4 (mg/l) < 5 Abs (436nm - m -1 ) 0,009 ph 8,8 C (ms/cm) 130 Dry matter (105 C - %) 17 scod (mgo 2 /L) 285 Cl (mg/l) Ca (mg/l) 247 TAC (mgcaco 3 /L) 119 SO 4 (mg/l) 9800 Abs (436nm - m -1 ) - 16/07/2012 Veolia Environnement Recherche & Innovation 19

20 Results obtained on Train 2 Global VCF = 35.2 VCF = 6.4 VCF = 5.5 ph 8,26 C (ms/cm) 7,1 Dry matter (105 C - %) 0,45 scod (mgo 2 /L) 391 Cl (mg/l) 1414 Ca (mg/l) 168 TAC (mgcaco 3 /L) 275 SO 4 (mg/l) 179 Abs (436nm - m -1 ) 4,32 ph 6,2 C (ms/cm) 0,029 Dry matter (105 C - %) - scod (mgo 2 /L) < 15 Cl (mg/l) < 5 Ca (mg/l) 1,61 TAC (mgcaco 3 /L) 0,2 SO 4 (mg/l) < 5 Abs (436nm - m -1 ) - ph 6,5 C (ms/cm) 0,02 Dry matter (105 C - %) - scod (mgo 2 /L) < 15 Cl (mg/l) < 5 Ca (mg/l) 0,68 TAC (mgcaco 3 /L) 0,3 SO 4 (mg/l) 6 Abs (436nm - m -1 ) - ph 8,5 C (ms/cm) 92,7 Dry matter (105 C - %) 12,6 scod (mgo 2 /L) 7590 Cl (mg/l) Ca (mg/l) 764 TAC (mgcaco 3 /L) 31,6 SO 4 (mg/l) 2900 Abs (436nm - m -1 ) - 16/07/2012 Veolia Environnement Recherche & Innovation 20

21 Conclusion In both trains, produced distillate had the same quality and fulfilled water quality criteria for the highest quality Train 1: Global VCF 40 Considering that VCF of NF step = 5 (80% conversion rate) VCF evapo+ NF = 200 final waste < 0.5% in volume of the global treated flux Train 2: Global VCF 35 Considering that VCF of NF step = 4 (75% conversion rate) VCF evapo+ NF = 140 final waste < 0.7% in volume of the global treated flux 16/07/2012 Veolia Environnement Recherche & Innovation 21

22 5 General conclusion 16/07/2012) Veolia Environnement Recherche & Innovation

23 General conclusion Evapoconcentration technology Reliable technology Can be used for various concentrated streams Allows to produce re-used water with high quality and to strongly reduce final waste to be disposed off But this technology is very energy consuming And limited to small flux to be economically viable For high flux: separation organic matter/salts Electrodialysis Activated Carbon Ion exchange resins 16/07/2012 Veolia Environnement Recherche & Innovation 23