Reverse Osmosis and Deionization Systems for Aquaria

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Reverse Osmosis and Deionization Systems for
Aquaria

• Thoram Charanda
• Sr. Chemist
• Walt Disney World Co.
• Life Support
• Lake Buena Vista, FL

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Reverse Osmosis and Desalination

• Theory of Osmosis
• Typical Industry Applications of Reverse Osmosis
  (RO), Desalination
• Practical Considerations for RO in Aquaria
• Designing an RO System for a Salt Water Exhibit

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Theory of Osmosis
Semipermeable Membrane
Pressure
p
Sea Water (diluted)
Sea Water
Fresh Water
Fresh Water
Fresh Water
Sea Water
H2O
H2O
H2O
H2O
Initial Condition
Equilibrium
Reverse Osmosis
The Osmotic Pressure, p, is defined as p
MRTFor sea water at 35 ppt, p is about 350 psi.
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Key Terms in RO Systems

• Permeate The purified product water exiting
  the system.
• Concentrate The concentrated salt solution
  exiting the system. In some system designs this
  outflow is returned to the aquarium for salt
  recovery.
• Feed Flow The total flow rate of the source
  water pumped in the system.
• Recovery - The percentage of permeate achieved
  in a system, Recovery permeate flow/feed flow
  x 100.
• Rejection The percentage of dissolved solids
  removed from the source water by the membrane.

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RO Membrane Filter Detail
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Industrial Applications of RO Systems

• Purification of potable or fresh water sources
  Purified, very low Total Dissolved Solids (TDS)
  water is produced for various uses. In the
  aquarium industry it can be used for
• - Make up water in fresh and salt water
  aquariums
• - As a pure water base for artificial salt
  water systems
• - As a non-scaling/spotting wash or rinse water
  for aquarium exhibit windows.
• Desalination of Sea Water
• - Production of potable drinking
• - Source water for combustible turbine power
  plants
• - Irrigation and non-potable utility water uses
• - It can also be used as a salt recovery system
  for closed-filtration sea water aquaria

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RO System for Fresh Water

• 300 to 1,000 gallon per day RO System
• Requires a reservoir tank, high level shut-off
  switch and delivery pump
• Pre-Filtration Requires a 5-micron sediment
  filter and a GAC filter to remove any chlorine
  residual and organics

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Desalination RO Systems
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Design Considerations for a Salt Recovery RO
System

• Consider your feed water source Natural or
  Artificial Sea Water.
• Identify the typical range of the water chemistry
  parameters.
• pH
• Temperature
• Salinity
• Silt Density Index (SDI)
• Silica
• Level of Particulates
• Presence of Organics or Residual Oxidizers
• What is the desired rate of permeate (fresh
  water) removal from your system? This will
  dictate the required feed flow rate for the RO
  system.

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Design Considerations for a Salt Recovery RO
System

• Consider any future requirements for system
  upgrade in fresh water removal capacity, e.g.
  system can accept an additional membrane, high
  pressure pump is slightly oversized.
• Identify the best location in the aquarium
  filtration pathway to connect the feed source.
• Consider connecting the return filtration line
  post ozonation.
• Identify pre-filtration requirements
• GAC filter to removal residual oxidants, e.g.
  bromine, ozone
• Additional particulate filters for highly loaded
  systems

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ROSA 5.4 Reverse Osmosis Design Software
Specialized software can be used to assist in the
initial design and membrane performance
parameters required for a successful salt
recovery system. A freeware program is offered by
DOW Chemical called ROSA 5.4, that offers the
ability to calculate the required feed, permeate
and concentrate rates based on the feed water
chemistry and a given sea water RO membrane
type. The URL for this program is www.filmtec.com.
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5,000 gpd RO System at Shark Reef, Typhoon Lagoon
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Deionization Water Filtration Systems

• Principles of Deionization (DI)
• Applications for DI Water
• Water Chemistry Parameters and Considerations for
  a DI System

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Ion Exchange Beads
Ion exchange beads are typically constructed of a
polymeric resin or gel with an average diameter
of 0.3 to 1.2 millimeters. The beads can have
either cationic or anionic functional groups
attached to the surface.
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Types of Ionic Exchange Resins

• Strong Acid Resins
• - contain functional groups of R-SO3H on the
  polymeric resin
• Weak Acid Resins
• - contain functional groups of R-COOH
• Strong Base Resins
• - contain functional groups of R-OH
• Weak Base Resins
• - contain functional groups of R-NH3

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Strong Acid Cationic Resin
Typical Cations
H
Na
R-SO3-H
Polymeric Resin
Ca2
R-SO3-Na
Mg2
R-SO3-H
K
Metals
R-SO3-
H
Cu2
R-SO3-
Ca2
Fe2
Zn2
H
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Applications for DI Water

• Analytical grade water for laboratory use
• Essentially salt and micro nutrient free water
  that can be used to make artificial sea water
• Replenish system water loss due to evaporation
• Makeup of specialized water quality environments,
  ie. natural waters with very low TDS and specific
  concentrations of cations

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Design Engineering of DI Systems

• Identify the source water for the DI system
• Analyze for the key water chemistry parameters
• pH
• Free and Total Chlorine
• Total Dissolved Solids (TDS)
• Identify the intended volume of DI required per
  day
• A GAC prefilter is required to remove residual
  chlorine and dissolved organics
• typically sized from 0.0283 to 0.057 m3 (or 1 to
  2 ft3)
• Plan for a reputable company to provide an
  exchange service for the mixed resin beds and
  GAC filter

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Design Engineering of DI Systems
Mixed bed ion exchange capacity 353,357 grains
per m3 10,000 grains per ft3
Example Your source water is potable city water
and you require up to 400 liters per day of
DI water. Source water TDS 200 ppm Equivalent
grains per gallon 11.7 gpg (divide TDS by
17.1) Planned DI resin exchange frequency 30
days Minimum required amount of mixed bed resin
0.105 m3 3.71 ft3
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Summary

• Reverse osmosis systems are a good design choice
  where
• - Moderate (2,000 liters) to large (18 m3)
  volumes of water are required per event and
  there is sufficient space for the purified water
  reservoir
• - Desalinated water source for utilities and as
  a purified water source for DI analytical
  laboratory grade water
• - Desalination system for salt recovery
• Deionization systems are a good design choice
  where
• - A relatively fast flow rate (gt 35 Lpm) of
  pure water is required
• - Only cost effective for relatively small
  exhibits, lt 2,000 liters
• - Analytical laboratory grade water

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Acknowledgements
Dow Chemical Company GE Water Technologies Reverse
Osmosis of South Florida US Filter
Corporation David Cohrs, National Aquarium in
Baltimore Kent Semmen, Brooksville Zoo Eric
Kingsley, Monterey Bay Aquarium