CONTACTOR TYPE ADVANTAGES DISADVANTAGES

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Marilynn Barnett
7 years ago
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1 CONTACTOR TYPE ADVANTAGES DISADVANTAGES - Backwash cycle cleans calcite media and prevents iron oxide particles and other sediments from fouling or coating the media. - Large particle calcites are prevented from leaving the filter tank due to the bottom underdrain. - Requires frequent automatic or manual backwash cycles to clean calcite media during replenishment and to avoid media compaction. - Requires spare units to operate during replenishment and backwashing. - Potentially higher headloss due to calcite media compaction. - Longer downtime during media replenishment. - Variation in tank head loss due to changes in bed height. - Lost in CO2 application efficiency due to continuous backwash. - Variation in water quality due to changing bed height CO2 concentration in the media. Downflow - Waste water treatment plant (WWTP) required for treating large amounts of backwash water. This includes settler and sludge removal units as well as water recovery system. - Return of cleaned water from the WWTP to the entrance of the plant causes flow increases and potentially turbidity events. Therefore reuse from backwash water requires sufficient storage for constant feeding. - Sludge from WWTP settler needs to be disposed. - Need for a separate storage area outside the filter area. - Operators with high technical skill required. - Delicate design due to motors and automation. Risk of failure, even under harsh environmental conditions. - Higher energy consumption - Higher capital and O&M costs.

2 CONTACTOR TYPE ADVANTAGES DISADVANTAGES - Constant water quality due to continuos bed height. - Refilling is done in the in-built silo and not directly on the bed s surface. No turbid water is generated during refill. No need to backwash and divert turbid water every refill. - No backwash required because media is not compacted. - Good quality calcite recommended (< 0,3% Fe2O3 ) to prevent iron or other sediments from fouling or coating the media and prevent the need for backwashing. - Percentage of calcite particles less than 0,1 mm to be minimized (< 1%) for prevent calcite been dragged by up-flowing water. - No need for spare units. - A very even distribution among tanks as they have same hydraulic head loss that remains constant during operation and refilling. - Lower head loss experienced. - Effluent turbidity is typically lower as fines do not accumulate at the top of the contactor. DrinTec Upflow of constant height - No backwash water treatment plant needed. Pumps and blower used in other sections of the desalination plant can be used for initial clean-up of the media. - Continuous operation. No need to stop the plant during replenishment. - No sludge to be disposed off. - Low energy consumption as no pumps or blower for backwashing is needed. - Robust design. No moving parts and low risk of failure, even under harsh environmental conditions. - Higher CO2 efficiency due to constant operation. - No need for separate storage area. In-built silos allow for more than 30 days autonomy. - Lower operation health and safety factors due to no moving parts. - Simple to operate. No high technical skills required. - Less expensive on capital costs and O&M.

3 YEARS OF OPERATION WITHOUT BACKWASHING FOR DRINTEC UPFLOW CALCITE CONTACTORS Nominal flow m 3/ d Main Parameters Location of plant Client Relevant Operation Parameters Year of commissioning Years of operation without backwashing 200, Rectangular concrete cells 3 m x 7 m Barcelona EBCT: 12.2 min Vsup: 12.3 m/h Bed height: 2.5 m. O.Pres: 0.7 bar Autonomy > 30 days 10 to , Rectangular concrete cells 2 m x 5 m Alicante Spanish Ministry of Public Works EBCT: 14.4 min Vsup: 10.3 m/h Bed height: 1.6 m O. Pres: 0.5 bar Autonomy > 30 days 10 to ,000 2 Rectangular concrete cells 2 m x 5 m Gran Canaria Vsup: m/h Bed height: 3.18 m Op. Pressure: 0.7 bar Autonomy > 30 days ,500 4 Rectangular concrete cells of 2.6 m x 5 m Gran Canaria Vsup: m/h Bed height: 2.42 m Op. Pressure: 0.7 bar Ø CaCO3: 1-3 mm Autonomy > 30 days

4 6,000 5 x FRP Tanks Ø2040 mm; 2.83 m bed height 5.5 m total height. Canary Islands Vsup: 15.5 m/h Bed height: 2.83 m O. Pres: 0.7 bar ,000 2,000 m 3 /d 2 x FRP tanks Ø2040 mm; 2,0 m bed height 4,2 m total height. Oman Vsup: 13.3 m/h Bed height: 3.42 m Op. Pressure: 0.7 bar ,000 2 x FRP tanks Ø2040 mm; 4 m total height Cape Verde Islands Local Water Supply Company Vsup: 13.3 m/h Bed height: 3.42 m Op. Pressure: 0.7 bar ,000 4 x FRP tanks Ø1860 mm; 4 m total height Formetera Island, Mediterranean Spanish Ministry of Public Works EBCT: 8 min Vsup: 16.4 m/h Bed height: 2.5 m Ø CaCO3: 1-3 mm O. Pres: 0.6 bar , x FRP Tanks Ø2040 mm; 3.35 m bed height 5.6 m total height Chile Mining Company EBCT: 13.9 min Vsup: 13.6 m/h Bed height: 3.35 m O. Pres: 0.7 bar 10 to

5 THE DRINTEC PROCESS: CONSTANT FEEDING OF GRANULAR CALCITE UNDER WATER

6 Turbidity during normal plant operation in a DrinTec plant "&.'''# &B'>%>;2%-.'/0'-/..%12%.3'/3'-/..%% Cells in operation (green) "'.'''# &B'>% $&.'''# $'.'''# &.'''# "&.'''# "# $%,# "'.'''# $%(# $%)# $&.'''# $%"# $# &B'>% "#$% '# "$/'&/$$# *$/'&/$$# $'/'(/$$# "'/'(/$$# *'/'(/$$# $'/'+/$$# &B'>%>;2%-.'/0'-/..%12%.3'/3'-/..%% "#$%>;2%-.'/0'-/..%12%.3'/3'-/..%% $'.'''# '%,# '%(# &.'''# '%)# '%"# '# '# "$/'&/$$# *$/'&/$$# $'/'(/$$# "'/'(/$$# *'/'(/$$# $'/'+/$$# "# "#$%>;2%-.'/0'-/..%12%.3'/3'-/..%%

7 Effect of plant restart to nominal flow rate in a DrinTec plant FLOW RATE (m 3 /h) TURBIDITY (NTU) Fig. 30.1: Evolución del caudal y de la turbidez en el arranque de la planta el día 23/01/2014 a 3,26 m/h.

8 PROCESS FLOW DIAGRAM OF A TYPICAL DOWNFLOW CONTACTORS WITH FREQUENT BACKWASHING NaOH TANK NaOCL TANK A 50% 1.BAR NaOH DOSING! NAOCL DOSING! B 1 BAR 3 LIMESTONE! RECHARGING! LIMESTONE RECHARGING & HANDLING 4 C 50% PRESSURIZED CONTACTORS % TOWER & 2.5 BAR TANK 1 BAR EXISTING PRODUCT WATER TANK PRODUCT WATER! BOOTER CO2 DOSING SYTEM 2 8 BACWASHING! WATER! (every 12 days approx.) 6 B AIR BLOWER! (every 12 days approx) SEDIMENTATION BASIN 7 SLUDGE! 9 EXTRACTION 11 FAN SLUDGE TO WASTEWATER TREATMENT

9 PROCESS FLOW DIAGRAM OF A TYPICAL DRINTEC CONTACTOR PLANT WITH NO BACKWASHING NEED NaOH TANK NaOCL TANK 9 10 A 50% Flow 1 BAR NaOH DOSING! NAOCL DOSING! B C 50% Flow 1 BAR 1 DRY LIMESTONE RECHARGING (once a month) ATMOSHPERIC DRINTEC CONTACTORS % Flow 1 BAR m TOWER & TANK 8 1 BAR EXISTING PRODUCT WATER TANK EXTRACTION CO2 DOSING SYTEM 2 FAN 6 5 WHITE-WATER TO WASTEWATER TREATMENT! (only at start-up)

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