Greenhouse Water Treatment and Filtration
(book excerpts)Water quality is very important for irrigating greenhouse crops, especially when considering micro-irrigation. Of particular concern are suspended solids, such as silt and sand, minerals that precipitate out of solution, such as iron or calcium, and algae that may grow in the water. Virtually every micro-irrigation system must include a filtration and treatment system for water. A system with poor quality water will not function reliably enough to warrant the maintenance requirements needed to keep it in operation. Suspended solids will normally be less of a problem when groundwater is used than when surface water is used for irrigation. The precipitation of minerals in irrigation water is usually a problem only with groundwater sources. Dissolved minerals may come out of solution with a change of pH or temperature or when aeration occurs. Growth of algae within the irrigation system is seldom a problem since most algae require sunlight to grow, and virtually all system components are made of opaque materials. However, if surface water is used to irrigate, algae often exist in the water supply. Water filtration and treatment can be thought of as a three-dimensional challenge: physical, chemical, and biological. A combination of physical, chemical, and biological treatment methods is often needed to treat irrigation water. No single water filtration or treatment system is best for all greenhouses. Suspended solids, organic matter, algae, bacteria, and other particles that can clog the irrigation system, especially drip emitters and sprinklers, can be removed from the water supply using filtration. A variety of filters is available for the removal of physical clogging agents from irrigation water. The choice of filter depends on the origin and quantity of contamination anticipated in the system, as well as the size of the irrigation system. Often, chemical treatment is required to prevent organic growths and/or chemical precipitation in the irrigation system. Biological treatment systems generally combine a number of treatment processes: physical separation, competition by other organisms, or creating an environment that does not favor pathogen survival. Often, these systems can provide nutrient removal as well and serve as methods for dealing with water that cannot be recirculated.
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Topics Within This Chapter:
- Water Treatment for Total Dissolved Solids
- Management Practices for Controlling Soluble Salts
- Leaching Fraction
- Selection of Growing Media
- Use of Substrate Amendments
- Irrigation Method
- Fertility Regime
- Plant Tolerance
- Reverse Osmosis
- Pretreatment Stage
- Filtering Efficiency
- Deionization
- Neutralizing Alkalinity/pH Adjustment
- Fertilizer Selection
- Reduce Limestone Added to Potting Media
- Low Alkalinity
- Acid Treatment
- Types of Acids
- Pre-Dilution of Acid/Base Concentrates
- pH Reaction Time
- Nutrients from Acids
- Water Filtration for Suspended Solids
- Pre-Treatment or Pre-Filtration
- Centrifugal Sand Separator
- System Flushing
- Rotating Drum Filter
- Fiber Media Filter
- Media Filters
- Sizing of Sand Media Filters
- System Flushing
- Screen Filters
- Sizing Screen Filters
- System Flushing
- Disc Filters
- System Flushing
- Membrane Filters
- Disinfestation of Greenhouse Irrigation Water
- Pre-Filtration
- Chlorination
- Chlorine Gas
- Sodium Hypochlorite
- Calcium Hypochlorite
- Factors to Consider with Water Chlorination
- Chlorine Dioxide
- Hydrogen Peroxide-Based Materials
- Copper Ionization
- Ultraviolet Light Treatment
- Ozonation
- Heat Pasteurization
- Water Treatment for Specific Ions
- Boron
- Calcium and Magnesium
- Ion Exchange
- Lime Softening
- pH Adjustment with Acid
- Chloride
- Fluoride
- Iron and Manganese
- Depth of Irrigation Intake from Holding Pond
- Basin Aeration Pump
- Tank Oxidation
- Oxidatizing Agents
