Aquaculture Water Sources

Supplies of Quality Water are Decreasing

What is Good for One Species May be Bad for Another

Water Quality Degradation is Dependent on Waste Generated

Waste Generated is a Function of Culture Intensity and Amount and Kind of Feed Added to System

Key: Know Highest Stocking Density Possible Without Degrading Water Quality

Much Depends on the Water Source

Aquaculture Water Sources Rivers, Lakes & Streams: Large Volumes – Inexpensive But often Excessive Nutrients & Potential for Contaminants (Toxins & Pathogens)

Surface Water: Inexpensive – But Strong Contaminant Potential (Toxins & Pathogens)

Springs: Harbor Few Predators – No Toxins or Pathogens

Wells: No Predators or Pathogens – Low O2 Levels

Groundwater: Hard to Drain or Remove Fish

Municipal Supplies: No Predators But Disinfectants Chloramines

Seawater: Plentiful But Chemistry & Pathogens Variable

Groundwater Supply Dependable – Uniform Over Time – Stock Free from Competitors  &  from  Competitor’s  Eggs  – No Predatory Insects

Water Temperature Nearly Constant Through-Out Year.

Contaminant Susceptibility Generally Low Depending on Local Pollution Sources – Septic Systems, Dumps etc

Potential for Toxic Gases Such as NH3, H2S CH4 & CO2

Major Disadvantage: Low O2 – Must Recharged – Also Excessive Fe2+ or Other Metal Ions

Types of Groundwater

Alternative Water Sources

Rainwater: Free, Unpredictable, Only a Supplement, Often Acidic, Poorly Buffered

City Water: Limited Potential Due to Cost, also Contains Disinfectants (eg Chlorine)

Saltwater Wells: Via Saltwater Intrusion, Ancient Seabeds Mineral Composition Variable – High Cost

Recycled Water: Stay within Permitting Guidelines – Prior Use Determines Availability – Conserves Pumping Requires Biofiltration – Sedimentation a Problem

Seawater

Although many of the issues we have studied in the context of freshwater aquaculture apply equally to salt water – much of Alaska’s  aquaculture revolves around seawater Therefore I am including a description of some of the differences caused by husbandry in seawater – or Mariculture compared with Fresh-Water Aquaculture

Seawater

Saltwater: Potential for Contamination & This Increases if Intake is Higher in Water Column & Closer to Shore

Problems: Intake Location, Biofouling & Salinity Fluctuations – Potential for Contamination by Hydrocarbons if Intake is Near Navigation Lanes

Estuaries Have High Tidal Amplitude and With it Potential for Increased Sediment Entrainment

Seawater Aquaculture Water Quality

Objectives: What Important Criteria are Associated with Obtaining Ocean Water

How is Seawater Prepared for Use in Aquaculture Systems?

How is Seawater Distributed in a Facility?

Seawater Composition Dissolved Gases* Nitrogen N2 12 ppm Oxygen O2 7 ppm Carbon Dioxide CO2 80 ppm

*Huge Variability – Values are Near Offshore Averages

n Water is a versatile solvent owing to the polarity of the water molecule

n Ionic compounds dissolve in water

Seawater Ionic Composition Chloride Cl- 18.98 ppt Sodium Na+ 10.56 Sulfate SO4

-2 2.65 Magnesium Mg+2 1.27 Calcium Ca+2 .40 Potassium K+ .38 Bicarbonate HCO3

- .14 Bromide Br- .07 Borate BO3

-3 .03 Strontium Sr+2 .01

On Average – Seawater  Salinity  is  3.5%  or  35‰ North Pacific is Lower – Around  33‰

Determining Salinity

Optical  Salinity  Refractometer      →

Or by Calculation from [Chloride]

Salinity ppt = 1.81 x [Chloride] ppt

Ion Sensitive Probe – [Chloride] = 19.2 ppt

Then Salinity = 19.2 x 1.81 = 34.7 ppt

Osmomolarity Osmolarity is a Measure of Solute Particles in Solution – Used in Reference to Seawater Because it Determines Many Physiological Parameters of Fish

NaCl which Dissociates into Na+ & Cl- – Counts as 2 Particles – Glucose does Not Dissociate and Counts as 1

Osmolarity is Distinct from Molarity – and is Indicated as Osm/l – in Physiology the Unit Frequently used is milliOsmolarity or mOsm/l

Measuring Osmolarity Osmometers Measure the Osmotic Strength of a Solution – Several Techniques are Employed Based on the Colligative Properties of a Solution

Colligative Properties of Solutions Depend on the Ratio of Solute Particles to Solvent Molecules in a Solution – and are Independent of the Solute  Particle’s  Nature

A 0.5 M NaCl Solution has the Same Osmolarity as a 1M Sucrose Solution

Osmometers Colligative Properties of Solutions Include: 1) Relative Lowering of Vapor Pressure 2) Elevation of the Boiling Point 3) Depression of the Freezing Point 4) Osmotic Pressure

Vapor Pressure and Freezing Point Osmometers are the Most Popular

For SW Fish – Osmoregulation is a Physiological Demand & Osmolarity Needs to be Monitored When FW Can Overwhelm the System

2 Kinds of Osmoregulation Osmoconformers Match Their Osmolarity to that of Their Environment Osmoregulators Control their Osmolarity, by Actively Adjusting Their Internal Salt Concentration

FW Fish: Internal Osmolarity Higher than FW – Gills Actively Take Up Salt – Water Diffuse in – Fish Control Their Water by Expelling Dilute Urine

Marine Fish: Internal Osmolarity Lower Than Seawater – Fish Tend to Lose Water & Gain Salt – Actively Excretes Salt from Gills

Sharks Use Different Mechanism – Retaining Urea in Tissue Increasing Osmolarity

Marine Aquaculture Salmon Farmed in Cages Inshore Salinity 32-35 ppt Depth >5 m Beneath Net – Moderate Current Flushes DO >80% Saturation – Temp < 18°C (65°F) Cage Size: Variable from 1-2 mts to 100-150 mts Net Bags 5-20 m deep – Shaped by Scaffolding Anti-Predator Material – Rings – Weights Fouling Increases Drag, Weight and BOD Means Nets Need to be Cleaned on Schedule Predators Can be a Major Problem

Hydrozoan Fouling

Seal on Salmon Cage

Sealion Eating Salmon

Seawater Treatment – Flow Thru Systems

Water Quality is Everything

Pre-Filtration Performed Via Well Screens

External Reservoir for Storage / Salinity Control

Pressurized Sand Filtration (20–50 μm)

Then Cartridge Filtration (5–0.5 μm )

Ozone Contact Disinfection / Degassing

In-Line UV Sterilization if Ozone Degassed

In-Line Heating on Flow-Thru Tanks

Water Supply-Reservoir

Most Facilities have Ample Water Storage Capacity in the Form of Reservoirs

Minimum Capacity is 24 Hours Worth of Water

Reservoir a Buffer Between Ocean and Seawater System in Case of Pollution or Salinity Changes

Advanced Facilities have Two Reservoirs, Used on Alternating Days

Reservoirs can be Ponds, Vertical Tanks, Underground Cisterns

Seawater Storage in 10,000 Gallon Reservoirs Texas AgriLife Research – Port Aransas Texas

Removing Solids All Contaminants in Water, Except Dissolved Gases Contribute to Solids Loading

Solids Includes Organic & Inorganic Constituents

Solids Block Pipes, Reduce O2 Levels & Compromise Filtration Equipment

As They Decompose, Organic Solids Consume O2 and Release NH3 / NH4

+

70% of NH3 / NH4+ in Water Associated with Organic

Solids & Not Excreted Nitrogen Compounds

Solids For Each Species & System, Solids Must be Characterized to Choose Proper Treatment Methodology

Seawater has Abundant Solids that Needs to be Removed

Solids Characterization Solids are Further Classified as being: Settleable Suspended, Dissolved or Colloidal

Difference Between Settleable & Suspended is a Matter of Practicality

Most Settleable: > 10 µm (in Imhoff cone <1 hr)

Particles Passing Thru a 1.2 µm Filter are Dissolved, Suspended Solids are Trapped

Dissolved Particles are Organic & Inorganic Ions and Molecules in Solution

Colloids: are Particles – 1 nm to 1 µm in Size Dispersed Within a Continuous Medium

Solids Treatment - Screens Simplest Method – Pre-Treatment Prior to Primary Treatment – Placed Across Flow of Recirc Water

Coarse Screens Handle Raw Effluent, Biofloc; Fine Screens for Tertiary Treatment

Varied Screen Materials: Cost Increases with Decreased Mesh Size

Static vs Rotary Screens: 0.25 to 1.5 mm ~ 4-16 gpm flow per in2 of Screen – Removal Efficiency ~ 5-25%

Rotary Screens for Fine Solids (15–60 µm) Removal are ~ 50-70% Efficient

Gravitational Separation of Solids

Primarily Used in FW Aquaculture as Settlement Ponds

Without Screens Water is First Treated by Simple Sedimentation (Primary Treatment)

Separation is by Gravitational Settling

Principle Design Criteria are Basin’s  Cross-Sectional Area, Detention Time, Depth & Overflow Rate

Ideal Sedimentation Basins do Not Exist Due to Particle Size Variation – Composition etc

Once Settling Velocity Known, Basic Dimensions Can be Estimated

Plate & Tube Separators

Also Work on Principle of Gravity

Enhance Basin Settling Capacity

Shallow Devices Consisting of Modules of Flat Parallel Plates or Inclined Tubes of Various Geometrical Design

Used in Primary Thru Tertiary Treatment with Limited Success

Centrifuge & Cyclonic Separators Increase Gravitational Force by Spinning (ie The Settling Rate Increases)

Many Devices All Rated at Different g Forces

Work Best on FW Systems Particles have Similar Densities to Seawater

Cyclonic Separators & Hydrocyclones are Most Practical

Heavy Particles Moved Downward by Gravity and to the Outside by Higher Velocity

Underflow Exiting Unit is Small and High Density Cleaner Water Exits at The Top

Sand Filtration

Mechanical Filtration Allows Gradual Reduction in Size of Particle Filters: 20µm \ 5 µm \ 0.5-1.0 µm

Reduction in Particle Size to < 20 µm by Rapid Pressurized Sand Filtration

Sand Filtration Filters at 40 psi, 100 gpm Flow & Installed in Parallel with 0.95-1.50 mm Sand

Sand Filtration Routinely Used with Seawater Systems – They are Not Acceptable for Raising Embryos or Larval Studies

Seawater Filtration Systems Water from Sand Filters Flows to a Battery of Cartridge Filters

Often There are Several Cartridges Housed in Common Canister

Canisters Need Shut-Off Valves – Pressure Gauges – Come in Both 5 µm & 0.5-1.0 µm Sizes for Particle Capture

Filtration Systems are Usually Designed for Each Facility to Handle Unique Seawater Characteristics & Flow Demand

Integrated Filter System

Typical Flow-meters Measures Both in gpm & lpm

Plastic Shatter-Proof Housing

Downstream from Main Pump Back-Pressure Valve

Impeller-Driven

Connected to Discharge Pipe by Saddle Arrangement

Low Q

High Flow / High Q

Biofilters Biofilters Rely on Bacterial Communities Growing on Wet Surfaces to Collectively Metabolize Specific Molecules Such as NH3 – Different Bacteria will Metabolize Different Pollutants

Takes Significant Time for a New Bacterial Community to Become Capable of Metabolizing Significant Amounts of the Specific Pollutant

Common Kinds of Biofilters are: Trickling Biofilter Pressurized Bead Filters Rotating Biological Contactors Fluidized Bed Sand Filters

Trickling Biofilter Simplest and Least Expensive Form of Biofiltration

Consists of Fixed Bed with Water Flowing Over Promoting a Layer of Microbial Slime (biofilm) to Grow - Covering the Bed of Media

System is for Aerobic Bacteria – Anaerobes Live Under Aerobic Colonies

Low Tech and Low Capacity Capacity Increased with Multiple Units

Pressurized Bead Filter System

A Pressurized System Providing an Efficient Mechanical & Biological Filter in One – Traps Debris in 25-30 μm Range Low Head Pressure & Backwash System with Easy Access to Bead Media

Separate Operational Cycles allows Bypassing Beads but Keeps Beads Oxygenated

Lower Pressure Operation Allows for Beads of Different Shapes and Composition Providing Settlement Sites for Alternative Microbes

Pressurized Bead Filter System

Different Kinds of Beads

Rotating Biological Contactors (RBC) RBCs Allow Water to Come in Contact with a Biofilm to Remove Pollutants in the Water

Rotating Biological Contactors Consist of a Series of Closely Spaced, Parallel Discs Mounted on a Rotating Shaft Supported Just Above the Surface of the Water.

Microbe Communities Grow on the Disc Surface and Metabolize Specific Pollutants in the Water

The Microbial Communities on RBCs Consist of Many Different Bacteria and Protozoa – Aerobes on Top – Half the Time in Air and Anaerobes Underneath – Shielded from the Air by the Aerobe Slime

Rotating Biological Contactor

Fluidized Bed Sand Filters (FBSF)

Sand Bed Fluidized When Up Flowing Water Raises Sand and Separates Grains – Velocity Required to Fluidize Bed is a Function of Shape, Size & Density of Particles

FBSFs Pack More Surface Area than Other Filters Optimal Shape is a Column – Small Foot Print for Given Capacity – FBSF Self Cleaning & Tolerant of Different Nutrient Loadings

Fluidization Fundamentals Buoyant Force of Rising Water Lifts Sand Bed When

Velocity Exceeds Minimum Fluidization Velocity

Static Bed(vo < vmf)

Expanded Bed(vo > vmf)

Water Distribution &Media Support Mechanism

Interface BetweenClear Fluid & Static Bed

LLe

UV Irradiation UV light is Emitted by Low-Pressure Mercury Discharge to Disinfect Water – Invented by Dr. Askok Gagdil (UC Berkeley) Disinfection at Affordable Cost is an Important Feature of UV Waterworks.

Use of UV treatment for Disinfection of Water is ~ 20,000 Times More Efficient than Boiling the Water

UV Photo-repair System Can undo DNA Damage caused by UV Irradiation – Photo-repair Requires White Light – Irradiated Organisms kept in the Dark Cannot Undergo Photo-repair

Term Sterilization Requires 100% Removal of Micro-Organisms Disinfection Only Requires 99.9999%

UV Disinfection System

In-Line UV Irradiator

Subsequent Seawater Treatment After Ozonation, Seawater is Stripped of Residual Ozone Via Aerated Column

Some Facilities use In-Line UV Irradiation to Strip Residual Ozone from the Seawater

In-Line UV Disinfection Recommended to Eliminate Pathogenic Organisms from Seawater

Seawater Distributed from Gravity Header Tank by 4 inch PVC Lines

Use Dual Distribution Systems to Allow Back-Flushing – Also Clean-Outs

Ozone – O3

Ozone is Used in Industrial Settings to Sterilize Water and Disinfect Surfaces – Ozone Oxidizes Most Organic Matter but it is a Toxic & Unstable Gas that Must be Produced On-Site

Ozone Used in Recirculating Systems Linked to Reduction of Bioavailable Iodine in Salt Water Systems – Resulting in Iodine Deficiency Symptoms

Ozonated Seawater is Used for Surface Disinfection – and Can Oxidize Not Only Bacteria but also Viruses