Sanosil disinfectants Use in hydroponic systems
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SANOSIL AG, CH-8634 Hombrechtikon, Switzerland Tel.: +41 (0) 55 254 00 54, Fax: +41 (0) 55 254 00 59 Email: info@sanosil.com, Website: www.sanosil.com
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Hydroponics Hydroponics or hydroculture refers to a type of plant cultivation in which plants root in a substrate (such as expanded clay, coconut fibres or rock wool) instead of soil. In this process, the plants are nourished and watered using a nutrient solution. By providing the optimal level of nutrients and water to plants, combined with relatively good protection against environmental influences in greenhouses, plants and crops can be produced in a relatively resourceefficient way and with the use of less pesticide and herbicide.
The most important hydroponic techniques: A distinction is made between active and passive systems. In passive systems, the plant “hangs” over a pool/pipe with nutrient solution that is sucked up to the roots of the plant via a wick (made for example from glass fibres) or an absorbent substrate (capillary effect). Well-known systems include houseplant hydroculture with expanded clay or clay granules (“Seramis”). These are not as effective as active systems, but their utmost simplicity and the fact that they work without need of management, electricity, pumps, etc. means they are less susceptible to errors and faults than active systems.
Active systems, however, transport the nutrient solution to the roots of the plants using a pump. Active systems include: • • • • •
Flooding desks (ebb and flood systems) Dripping systems/top feeders (drip irrigation via a hose) NFT nutrient film DWC (deep-water culture) Aeroponic systems (spraying freely hanging plant roots)
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Ebb and flood (flood desks) This is a simple and safe type of hydroponics. In the ebb and flood method, plants stand in pots with a substrate made from coconut fibres or rock wool in a flat tub, referred to as the flood desk. The substrate stabilises the roots and functions as a short-term deposit location for the nutrient solution. At regular intervals (3-6 times per day), the tables are flooded from a supply container using a pump and (after the substrate blocks have fully soaked) the excess water flows off and back into the supply tank. The speed at which water is pumped into the table is irrelevant, so a simple, low-capacity pump is sufficient. However, flood systems tend to become contaminated very quickly. The large surface and liquid/air borders create optimum conditions for the formation of biofilm. Root rot as a result of fungi (pythium) also often occurs in untreated systems.
Dripping systems: This is a frequently used design type in hydroponics, with a wide range of variants. In the simplest variant, the plants stand in pots with small balls of expanded clay, or in rock wool cubes covered with plastic film. A small water hose connects each plant to the branched irrigation system, in which the nutrient/water quantity can be controlled individually. Depending on the system, there is also a backflow which returns excess nutrient solution into a collection tank. This prevents substrate salinization. Problems in these systems occur primarily because significant heat formation in the thin tubes lowers the oxygen content of the water, resulting in favourable conditions for root rot. In addition, the lines tend to calcify and build up biofilm, which can result in blockages and therefore crop failures.
NFT nutrient film systems are recirculation systems. In this process, plants stand in pots/substrate cubes in a sloping trough or a kind of table, while the nutrient solution is conveyed by a pump to one side of the table with a slight incline, before running to the other side as a thin film and, from there, returning to the tank. This means that the nutrient solution is used multiple times and – in the supply tank – can be constantly controlled, supplemented with the required substances, and also have oxygen added (via a kind of aquarium pump).
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Adding a cover made up of a film that is impermeable to light is very important in this process, in order to prevent the growth of algae. If the nutrient solution does not include Sanosil, it will need to be completely replaced relatively often (1-2 times per week) as it tends to become contaminated. Semiactive DWC deep water culture has a special status. In DWC (deep water culture), pots filled with substrate (mostly expanded clay) hang in buckets or tanks containing nutrient solution, and shall be filled only to the point where the nutrient solution is just touching the expanded clay. In this process, the nutrient solution is ventilated and enriched with oxygen. The small balls of expanded clay pull the nutrient solution upward and the root system is able to thrive. Soon, the roots grow out of the pots and hang into the water. The level of the nutrient solution reduces as the plant grows more strongly. This means that the plant roots are more exposed to air and are able to take in additional oxygen. Therefore, although this system does not require irrigation pumps, oxygen enrichment of the nutrient solution with air pumps is very important.
Aeroponic systems are the futuristic option in hydroponic systems. Developed for space travel by future-focused researchers, they do not need any substrate whatsoever. The plants hang (held by a type of rubber cuff) in a box, and the freely hanging roots are sprayed with nutrient solution by pumps/atomisers. Systems with living fish are often integrated into these processes, and the fish excretions are used as fertiliser for the plants. This enables, for example, the simultaneous cultivation of fish and vegetables such as carrots. However, this system is relatively susceptible to obstructions and has the highest energy requirements of any system, due to the high pump outputs.
Sprinkler technology They must be mentioned for the sake of completeness. Although this is not a separate hydroponic technique, it is very widely used in greenhouses. In this process, each plant is irrigated by a nozzle attached above the plant. Excess water either trickles away into the ground or is transported away by a drainage line, in order to prevent waterlogging.
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Problems when operating a hydroponic system: As hydroponic systems can be completely closed off from the environment through installation in greenhouses, problems with garden pests are significantly more minor than on conventional fields. However, other difficulties occur: The often-warm temperatures in greenhouses and the many thin lines used (particularly in the dripping method) mean that water heats up quickly. This reduces the capacity for oxygen and CO2 to be absorbed.
Limescale Limescale occurs more quickly as a result of water being heated, particularly in hard water. Lime crystals form on the surfaces of tanks and hoses, and encourage the formation of biofilms.
Biofilms Biofilms are mucus structures consisting of algae, protozoa and fungi, and form very quickly. These plaques can obstruct parts of the irrigation system and therefore cause crop failures. In addition, biofilms create ideal reservoirs for bacteria and fungi, which may damage the root system of the plants. In addition, depending on their composition, they may absorb nutrients and oxygen from the water, preventing those nutrients and oxygen from being transported to the plant roots. This encourages development of the notorious stem or root failure as a result of fungi and various bacteria.
Toppling diseases: Toppling diseases refers to plant diseases that attack the stems and roots of plants, causing the plants to bend or die. Many of these diseases are due to fungi such as pythium or fusarium. As damp conditions encourage the spread of these diseases, they are mainly caused by seedlings/plants being planted too close together, or too much irrigation on soil that is too compressed, with poor ventilation/a lack of oxygen. These conditions are a matter of course in a hydroponic system, and must be corrected accordingly.
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The solution: Limescale is either prevented/removed through the use of softened water or by regularly descaling the systems with e.g. phosphoric acid after the harvest. The other problems mentioned can be resolved by: A) scrupulous cleanliness when installing the system (cleaned and disinfected tools, new/disinfected substrate, absolutely clean and disinfected water system) B) a disinfectant that can be mixed into the water/nutrient solution during operation, and features the following properties: • • • • • • • • • • • • •
No restriction to plant growth/plant health Approved for disinfection of drinking water Does not leave problematic residues in plants and environment Comprehensively effective against typical bacteria that occur in humidity, as well as biofilms, algae and fungi Does not increase the pH value of the water Does not leave deposits in the water system Long-term effect; prevents re-contamination Compatible with standard fertilisers/nutrients Efficient dosing/benefit ratio Biodegradable without problematic byproducts such as trihalomethanes Does not change the taste or smell of the plants Can be easily dosed and measured in water Enriches the water with oxygen
The Super 25 and S015 disinfectants fulfil all of these requirements.
✓
Both products are approved for the disinfection of drinking water and are distinguished only by their commercial size and packaging/concentration of active agent. They are identical in their working concentration.
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Product variants (Sanosil Super 25, Sanosil S015) Sanosil drinking water disinfectants are available in two different concentrations, and are identical in their efficacy at comparable working concentrations. Product
User requirements (handling)
Sanosil Super 25 High-concentration
Use only by professional personnel.
Sanosil S015 Concentrate
Can be used by normal personnel after instruction.
- H2O2 content - Transport - Warning symbols Contains 50% H2O2 Hazardous substance UN 2014 C, O Contains 7.5% H2O2 Not classed as dangerous goods
Sanosil disinfectants: product description Sanosil S015/Super 25 have been proving their worth for water disinfection for more than 30 years. Their consistent efficacy against bacteria, viruses, yeasts, moulds and a broad spectrum of protozoa has been repeatedly tested and confirmed by internationally recognised institutions. In contrast to many other biocides, Sanosil disinfection products offer outstanding protection against biofilms, as well as being effective long-term. The main active ingredient is environmentally friendly hydrogen peroxide, which is stabilised and made more effective against microorganisms through the addition of silver. The result is an antimicrobial effect many times greater than that of native hydrogen peroxide. The tiny amounts of silver help to prevent recolonisation. On direct contact with the microbial cell wall, the elemental oxygen (O2) produced by the hydrogen peroxide attacks it.
1. The oxygen reacts with molecules in the cell wall, leading to its denaturation and destruction. The effect is enhanced by silver ions, which bind to sulphur bridges in specific microbial proteins 2. resulting in their inactivation or precipitation.
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Effect of stabilised hydrogen peroxide on biofilms Standard hydrogen peroxide products without stabilisation tend to break down very rapidly on contact with biofilms. This can severely limit their efficacy. To achieve maximum effect, the hydrogen peroxide needs, as in Sanosil disinfectants, to be highly stabilised. This inhibits decomposition of the hydrogen peroxide for a period following initial contact with the surface of the biofilm and enables the peroxide to penetrate the biofilm structure. The action of the catalase produced by the biofilm then leads to the release of oxygen from the peroxide. In addition to their oxidising effect, the fine bubbles produced exert a physical, mechanical effect. The expansion of the bubbles within the biofilm matrix literally blows/tears the matrix apart. The resulting biofilm fragments detach from the structure, leaving holes, which in turn allow further peroxide to penetrate into the structure. Under optimal conditions, the entire biofilm coating is rapidly detached from the substrate and broken up.
1. Stabilised hydrogen peroxide (blue) comes into contact with the biofilm structure (brown)
2. Thanks to their stability, the peroxide molecules are able to penetrate the film structure
3. The peroxide which has penetrated the film begins to release oxygen
4.
The bubbles of oxygen come together, expand and blow the biofilm apart.
Additional effect of silver on microorganisms
Once the biofilm structure has been broken up, the individual microorganisms are virtually defenceless against the dual-phase effect of the disinfectant. Whilst the cell walls are broken open by oxidation, silver blocks the microorganisms’ ability to reproduce and obtain energy. This results in excellent elimination rates and longterm efficacy. Margin note: Certain competitors of Sanosil AG try to market product copies of the original products as “silverstabilised hydrogen peroxide”. They claim that silver is not effective in any way as a biocide and that it only serves as a stabiliser in the product. This is of course nonsense and is stated with the sole purpose of bypassing the registration requirements of the EU Biocides Regulation.
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Use of Sanosil disinfectants: Surface disinfectants: Both Sanosil S015 and Super 25 can be used both for water disinfection and surface disinfection. In this process, S015 is mixed with water at 20%-66%, while Super 25 is mixed with water at 3%-10%. This solution is sprayed onto materials and surfaces that have been pre-cleaned as thoroughly as possible (e.g. empty plant troughs, pots, substrate, tools, etc.). An appropriate cold fogger such as the Sanosil Easy Fog is particularly well-suited to this task. Robust plants can even be treated directly to protect against fungal diseases such as mildew. (20% S015, 3% Super 25)
Important: where possible, disinfectant solution should be used within 24 hours of mixing in order to prevent quality defects.
Water system shock disinfection: It is worth performing shock disinfection on the entire water system before the first commissioning/introduction of the plants. To this end, shock disinfectant is mixed in a supply container, brought into the system, and left there for 8-12 hours. In this way, (unused) substrate can also be treated. Dosing in this process is as follows: For S015: 6-7ml/l water; for Super 25 approx. 1ml/l water.
• Maintenance disinfection with operation 1 (recirculation systems) The disinfectant can be manually added directly into the nutrient solution tank in recirculation systems. Dosing for S015: 0.33-1.6ml/l water, for Sanosil Super 25: 0.05-0.25ml/l water (mix well). Any pH correction required must be performed right at the end of the process. Please note: Organic fertilisers such as guano, liquid manure, poultry manure, etc. greatly reduce the effect of the disinfectant. In systems with automatic level control, the disinfectant can be dosed and added to the fresh or supplementary water using a proportional dosing system or a dosing pump. • Maintenance disinfection with operation 2 (sprinkler systems) In order to keep the line system (no nutrient solution/recirculation tank) free of biofilms and bacteria, it is sufficient to mix a dose of 0.13 ml/l of water for S015 and 0.02 ml/l of water for Super 25 into the water.
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Measuring the concentration in the water: The concentration of the Sanosil disinfectant in the water and nutrient solution can easily be determined at any time using corresponding test strips. These show the content of the Sanosil disinfectant in the water when they are immersed and change colour.
Our instructions for use are based on comprehensive experiments. The advice we give is based on the best current knowledge. Since usage and storage conditions are outside of our control, it does not, however, claim to be definitive. Product descriptions and information on the properties of the preparations do not contain any statement on liability for damages.
SANOSIL AG, CH-8634 Hombrechtikon, Switzerland Tel.: +41 (0) 55 254 00 54, Fax: +41 (0) 55 254 00 59 Email: info@sanosil.com, Website: www.sanosil.com
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SANOSIL AG, CH-8634 Hombrechtikon, Switzerland Tel.: +41 (0) 55 254 00 54, Fax: +41 (0) 55 254 00 59 Email: info@sanosil.com, Website: www.sanosil.com
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