Chapter 5 – water treatment
Chapter 5 - Water Treatment
5.1 Overview of Water Treatment
Water treatment is necessary in both semi-closed and closed systems.
Factors determining treatment type and degree:
Requirements for culture organisms.
Initial quality of water.
Cost considerations (capital and operating).
5.2 Methods of Water Treatment
Filtration: Removal of particulates or dissolved materials.
Disinfection: Techniques include using ozone (O3), ultraviolet (UV) light, or chlorination to eliminate unwanted organisms.
Aeration: Enhances dissolved oxygen (DO) levels in the water.
Degassing: Removal of excess nitrogen (N2).
Temperature Control: Essential for optimal organism growth.
5.3 Filtration Methods
5.3.1 Mechanical Filters
Screens: Simple filter screens placed at pump inlets.
5.3.2 Rotary Filters
Water flows through rotating screens with both filtering and backwash capabilities.
5.3.3 Bag Filters
Primarily used at raceway inlets and tanks; easy to clean and are available in various weaves to filter specific particle sizes.
5.3.4 Cartridge Filters
Less common; useful in laboratory and hatchery systems.
5.3.5 Particle Filters
Contain a housing with a filtering bed (sand/gravel). Smaller bed material removes finer particles but slows flow.
Backwashing process:
Reverses water flow to dislodge accumulated particles and clear the filter.
5.4 Chemical Filters
5.4.1 Foam Fractionation
Removes organic waste through a process of bubble formation.
5.4.2 Carbon Filtration
Activated carbon filters remove polar and non-polar solutes.
High surface area due to microporosity, and must be arranged downstream of biological filters to avoid clogging.
5.4.3 Ion Exchange
Utilizes resins to exchange ions from the water, commonly for softening hard water.
5.5 Disinfection Techniques
5.5.1 Ultraviolet (UV) Radiation
Disrupts microbial DNA and RNA through exposure to specific wavelengths.
Efficiency considerations: Suspended particles can hinder effectiveness.
5.5.2 Ozone (O3) Treatment
A strong oxidizing agent that reacts with microbes.
Produced via high voltage or UV exposure.
Requires decomposition to O2 before entering aquaculture systems to prevent toxicity.
5.5.3 Chlorination
Common in wastewater treatment; involves electrolysis of salt and subsequent reactions forming hypochlorous acid for disinfection.
De-chlorination methods:
Activated carbon, UV radiation, and sodium thiosulfate.
5.6 Aeration Techniques
Necessary to raise dissolved oxygen (DO) levels, particularly in high-density culture environments.
Factors affecting oxygen transfer:
Differential pressure gradients.
Water movement in the system.
5.7 Temperature Control in Water Treatment
Critical for fish health and plant growth in aquaponics.
Methods to regulate temperature include insulation, placement in shaded areas, and the use of heaters or chillers to maintain stability in varying climates.
Chapter 5 – water treatment
Chapter 5 - Water Treatment
5.1 Overview of Water Treatment
Water treatment is necessary in both semi-closed and closed systems.
Factors determining treatment type and degree:
Requirements for culture organisms.
Initial quality of water.
Cost considerations (capital and operating).
5.2 Methods of Water Treatment
Filtration: Removal of particulates or dissolved materials.
Disinfection: Techniques include using ozone (O3), ultraviolet (UV) light, or chlorination to eliminate unwanted organisms.
Aeration: Enhances dissolved oxygen (DO) levels in the water.
Degassing: Removal of excess nitrogen (N2).
Temperature Control: Essential for optimal organism growth.
5.3 Filtration Methods
5.3.1 Mechanical Filters
Screens: Simple filter screens placed at pump inlets.
5.3.2 Rotary Filters
Water flows through rotating screens with both filtering and backwash capabilities.
5.3.3 Bag Filters
Primarily used at raceway inlets and tanks; easy to clean and are available in various weaves to filter specific particle sizes.
5.3.4 Cartridge Filters
Less common; useful in laboratory and hatchery systems.
5.3.5 Particle Filters
Contain a housing with a filtering bed (sand/gravel). Smaller bed material removes finer particles but slows flow.
Backwashing process:
Reverses water flow to dislodge accumulated particles and clear the filter.
5.4 Chemical Filters
5.4.1 Foam Fractionation
Removes organic waste through a process of bubble formation.
5.4.2 Carbon Filtration
Activated carbon filters remove polar and non-polar solutes.
High surface area due to microporosity, and must be arranged downstream of biological filters to avoid clogging.
5.4.3 Ion Exchange
Utilizes resins to exchange ions from the water, commonly for softening hard water.
5.5 Disinfection Techniques
5.5.1 Ultraviolet (UV) Radiation
Disrupts microbial DNA and RNA through exposure to specific wavelengths.
Efficiency considerations: Suspended particles can hinder effectiveness.
5.5.2 Ozone (O3) Treatment
A strong oxidizing agent that reacts with microbes.
Produced via high voltage or UV exposure.
Requires decomposition to O2 before entering aquaculture systems to prevent toxicity.
5.5.3 Chlorination
Common in wastewater treatment; involves electrolysis of salt and subsequent reactions forming hypochlorous acid for disinfection.
De-chlorination methods:
Activated carbon, UV radiation, and sodium thiosulfate.
5.6 Aeration Techniques
Necessary to raise dissolved oxygen (DO) levels, particularly in high-density culture environments.
Factors affecting oxygen transfer:
Differential pressure gradients.
Water movement in the system.
5.7 Temperature Control in Water Treatment
Critical for fish health and plant growth in aquaponics.
Methods to regulate temperature include insulation, placement in shaded areas, and the use of heaters or chillers to maintain stability in varying climates.
