businessmen
Active Member
I think you forgot carbon filtration in your examples of filtration
Water: The Most Essential Compound
- Thread starter doc111
- Start date
doc111
Well-Known Member
What is Activated Carbon?
Activated carbon (AC) is a natural material derived from bituminous coal, lignite, wood, coconut shell etc., activated by steam and other means, and each one have different adsorption properties (e.g. bituminous carbon for high chlorine reduction capacity). Some manufacturers use various blends of carbon to achieve specific water quality and contaminants reduction (e.g. coconut shell carbon for "sweet taste").
Activated carbon surface properties are both hydrophobic and oleophilic; that is, they “hate” water but “love” oil. When flow conditions are suitable, dissolved chemicals in water flowing over the carbon surface “stick” to the carbon in a thin film while the water passes on.
This process is called adsorption. As a result of the adsorption process,activated carbon is an effective method in removing chlorine and it's by-products (TTHM's) and volatile organic compounds (carbon based VOC's). Both, man-made and naturally occurring including among others:
None carbon based anions (-) and cations (+) such as arsenic, fluorides, some heavy metals, nitrate, etc.
What forms does it come in?
Most popular forms of activated carbon used in the treatment of POU drinking water filters are granular activated carbon (GAC), extruded solid carbon block (CB) and powdered activated carbon (PAC).
What is granulated activated carbon (GAC)?
All activated carbon forms including granulated activated carbon (GAC) have a tremendous surface area resulting from its porous structure. GAC filters degree of effectiveness depends on the flow rate of the water and contact time with the water. If flow rate is excessive their efficiency could be as low as 0% and if the flow rate is slow their efficiency can match and or exceed those of different carbon forms.
For comparative purpose, a teaspoon of activated carbon have surface area the size of a football field.
What are the advantages of GAC vs. other form of carbon?
On a large scale such as municipal water treatment pools (gravity filters) for taste, odor and chemical reduction GAC is cheaper, very effective and can be re-used.
Powdered activated carbon used in CB and PAC cartridgesFine granule carbon used in GAC cartridgesCoarse mesh carbon used for industrial and municipal gravity water filters
Can I make my own GAC water filter?
Sure. If you are a bit handy you can make a GAC water filter using standard 3" PVC pipe, fittings and few accessories for less than five dollars. If you intend to market your "invention" you must apply a fancy label around the pipe and come up with some catchy name such as "spring", "natural water", "pure", something on that order. Kidding, take a little break from this boring technical stuff however don't leave, it's getting more interesting or, for quick and easy to understand the filtration principle go to Doulton's filtration principle.
Can silver impregnated GAC remove bacteria?
No form of carbon filter removes bacteria. In fact under quite normal operating condition all carbon forms can and do become perfect breeding grounds for bacteria, including pathogenic bacteria. Silver based GAC's are effective in controlling bacterial growth and multiplications (bacteriostatic) only for a short time because the silver is in form of a "spray" over a small percent of granules (usually 1.05% of the total GAC content). As the water passes the granules "rub off" each other leaching the silver prematurely. As we mentioned earlier, a POU filter containing silver based GAC must register that device with EPA, that does not mean is approved by EPA.
My inexpensive GAC water filter is rated for 10.000 gallons while more expensive "block" water filters are only rated for 500 gallons, why are they so much more expensive?
First of all your 10K filter is rated for chlorine reduction which if properly designed and used will do the job for that quantity, a more expensive "block" filter rates their "life-span" on specific contaminants reductions such as lead, THM's etc. It's like comparing apples to oranges. Granted that you use your 10K chlorine reduction filter within short time you are fine, otherwise you are taking chances of bacterial and chemical "dumping" contaminations.
What micron pore rating is my GAC filter?
These filters cannot be measured in micron pore size due to their granular state. They are measured in mesh size similar to that of your window screen. Coarse carbon is used in different applications while in domestic POU finer mesh is used followed by a cloth like "filter" to prevent granule escaping.
What is "channeling" or "dumping" means?
"Channeling" is water passing through least resistant path of the granule bed avoiding contact time with carbon resulting lower effectiveness. "Dumping" is sudden change in your water pressure releasing the trapped contaminants into your glass. "Dumping" can occur also if your carbon filter media is exhausted (over used). Some times this is visible as a "gray" water but most often is not. This happen with pressure filter cartridges.
Sounds like the GAC water filters are terrible buy?
Not quite. If your water is municipally supplied a well designed GAC filter with changeable cartridge is all you'll need, don't forget to change the cartridge at least every 6 months. Avoid those "high capacity" throw away filters unless you use that capacity within 6-9 months.
Why should I buy expensive carbon block water filter instead of less expensive pitcher-style or faucet-mounted water filters?
Let me ask you a question. Do you want your drinking water to be cleanest, semi-clean or just somewhat clean? Those gadgets are made with small amount of GAC and ion exchange media. The most popular pitcher-style "filter" was developed many years ago in Germany to strip the water from calcium and magnesium (hardness). Why? In those days car batteries required periodic refill with water. The distilled water being so acidic was eating the lead cells while hard water was shorting the cells. Of all GAC filters these are the least effective and cheapest to buy however, the most expensive to use on ongoing basis (low capacity "filters"). NSF standard 42 have 3 classes for chlorine reduction; class I is >75% reduction, class II is 50-75% reduction and class III is 25-50% reduction. Most of those filters falls under class III. It's like "you get what you pay for" rule.
Conclusion: In most cases, pre and post-filtration, including a ceramic filter element will improve the effectiveness of the GAC filter.
Of all carbon forms solid carbon block (CB) filters are the most efficient and cost effective method
of removing volatile organic carbon compounds (VOC's, insecticides, pesticides and industrial solvents) from drinking water.By adding various ion exchange media (e.g. zeolite, activated alumina or other media) heavy metal, MTBE, nitrate and other water treatment effects can be achieved.
CB's are made of single or various blends of carbons combined with plastic polymers which are pulverized to a fine dust then shaped in varieties of forms under high pressure (600 to 800 tons). Unlike the other carbon forms, the CB's are industrial grade filters. They are made in various sizes and micron ratings (nominal), are physically strong therefore they do not "channel" nor "collapse"under pressure change, however once carbon block is exhausted for chemical removal have to be changed according to the manufacturers specifications.
Most 1/2 micron nominally rated CB filters are effective in cysts and asbestos reduction (not removal). CB's are the best choice for POU filters.
CB filters by itself have to be used on microbiological safe water.
The best CB filter is inside Doulton ceramic shell and Aquasana filtration system.
Can my 1/2 micron CB protect me against bio-terrorism on our water supplies?
Not at all. For that you'll need a laboratory grade RO system, a filter with 1/2 micron or less absolute ANSI standard pore size, distillers and UV's to some extent.
Powdered Activated Carbon (PAC)
As with CB's, molded or powdered activated carbon (PAC) are very effective method of removing volatile organic compounds (insecticides, pesticides and industrial solvents) from drinking water.
As with all carbon forms change these filters often and do not wait until quality of the water taste has deteriorated.
The best and only PAC filter made in USA is Multi-Pure solid carbon block.
NOTE: All POU activated carbon water filters should be used on microbiologically safe water only.
At last, here we are, more tech stuff which you have been patiently waiting for.
What is it all this stuff about microns, pore size ratings, nominal, absolute etc. means?
Pore size - Absolute vs. Nominal Microns (µm) Pore Ratings>>
Source: DoultonUSA
Activated carbon (AC) is a natural material derived from bituminous coal, lignite, wood, coconut shell etc., activated by steam and other means, and each one have different adsorption properties (e.g. bituminous carbon for high chlorine reduction capacity). Some manufacturers use various blends of carbon to achieve specific water quality and contaminants reduction (e.g. coconut shell carbon for "sweet taste").
This process is called adsorption. As a result of the adsorption process,activated carbon is an effective method in removing chlorine and it's by-products (TTHM's) and volatile organic compounds (carbon based VOC's). Both, man-made and naturally occurring including among others:
- alachlor
- atrazine
- benzene
- carbofuran
- carbon tetrachloride
- chlorobenzene
- 2,4-D
- dibromochloropropane (DBCP)
- O, P-dechlorobenzines
- forms of dichloroethylens
- 1, 2-dechloropropane
- cis-1,3-dichloropropylene
- toxaphene
- chlordane
- radon
- lindane
- simazine
- PCB's
- toluene
- xylenes etc., etc.
None carbon based anions (-) and cations (+) such as arsenic, fluorides, some heavy metals, nitrate, etc.
What forms does it come in?
Most popular forms of activated carbon used in the treatment of POU drinking water filters are granular activated carbon (GAC), extruded solid carbon block (CB) and powdered activated carbon (PAC).
What is granulated activated carbon (GAC)?
For comparative purpose, a teaspoon of activated carbon have surface area the size of a football field.
What are the advantages of GAC vs. other form of carbon?
On a large scale such as municipal water treatment pools (gravity filters) for taste, odor and chemical reduction GAC is cheaper, very effective and can be re-used.
Can I make my own GAC water filter?
Sure. If you are a bit handy you can make a GAC water filter using standard 3" PVC pipe, fittings and few accessories for less than five dollars. If you intend to market your "invention" you must apply a fancy label around the pipe and come up with some catchy name such as "spring", "natural water", "pure", something on that order. Kidding, take a little break from this boring technical stuff however don't leave, it's getting more interesting or, for quick and easy to understand the filtration principle go to Doulton's filtration principle.
Can silver impregnated GAC remove bacteria?
No form of carbon filter removes bacteria. In fact under quite normal operating condition all carbon forms can and do become perfect breeding grounds for bacteria, including pathogenic bacteria. Silver based GAC's are effective in controlling bacterial growth and multiplications (bacteriostatic) only for a short time because the silver is in form of a "spray" over a small percent of granules (usually 1.05% of the total GAC content). As the water passes the granules "rub off" each other leaching the silver prematurely. As we mentioned earlier, a POU filter containing silver based GAC must register that device with EPA, that does not mean is approved by EPA.
My inexpensive GAC water filter is rated for 10.000 gallons while more expensive "block" water filters are only rated for 500 gallons, why are they so much more expensive?
First of all your 10K filter is rated for chlorine reduction which if properly designed and used will do the job for that quantity, a more expensive "block" filter rates their "life-span" on specific contaminants reductions such as lead, THM's etc. It's like comparing apples to oranges. Granted that you use your 10K chlorine reduction filter within short time you are fine, otherwise you are taking chances of bacterial and chemical "dumping" contaminations.
What micron pore rating is my GAC filter?
These filters cannot be measured in micron pore size due to their granular state. They are measured in mesh size similar to that of your window screen. Coarse carbon is used in different applications while in domestic POU finer mesh is used followed by a cloth like "filter" to prevent granule escaping.
"Channeling" is water passing through least resistant path of the granule bed avoiding contact time with carbon resulting lower effectiveness. "Dumping" is sudden change in your water pressure releasing the trapped contaminants into your glass. "Dumping" can occur also if your carbon filter media is exhausted (over used). Some times this is visible as a "gray" water but most often is not. This happen with pressure filter cartridges.
Sounds like the GAC water filters are terrible buy?
Not quite. If your water is municipally supplied a well designed GAC filter with changeable cartridge is all you'll need, don't forget to change the cartridge at least every 6 months. Avoid those "high capacity" throw away filters unless you use that capacity within 6-9 months.
Why should I buy expensive carbon block water filter instead of less expensive pitcher-style or faucet-mounted water filters?
Let me ask you a question. Do you want your drinking water to be cleanest, semi-clean or just somewhat clean? Those gadgets are made with small amount of GAC and ion exchange media. The most popular pitcher-style "filter" was developed many years ago in Germany to strip the water from calcium and magnesium (hardness). Why? In those days car batteries required periodic refill with water. The distilled water being so acidic was eating the lead cells while hard water was shorting the cells. Of all GAC filters these are the least effective and cheapest to buy however, the most expensive to use on ongoing basis (low capacity "filters"). NSF standard 42 have 3 classes for chlorine reduction; class I is >75% reduction, class II is 50-75% reduction and class III is 25-50% reduction. Most of those filters falls under class III. It's like "you get what you pay for" rule.
Conclusion: In most cases, pre and post-filtration, including a ceramic filter element will improve the effectiveness of the GAC filter.
- Top of Page -
Extruded Carbon Block (CB)
of removing volatile organic carbon compounds (VOC's, insecticides, pesticides and industrial solvents) from drinking water.CB's are made of single or various blends of carbons combined with plastic polymers which are pulverized to a fine dust then shaped in varieties of forms under high pressure (600 to 800 tons). Unlike the other carbon forms, the CB's are industrial grade filters. They are made in various sizes and micron ratings (nominal), are physically strong therefore they do not "channel" nor "collapse"under pressure change, however once carbon block is exhausted for chemical removal have to be changed according to the manufacturers specifications.
Most 1/2 micron nominally rated CB filters are effective in cysts and asbestos reduction (not removal). CB's are the best choice for POU filters.
CB filters by itself have to be used on microbiological safe water.
The best CB filter is inside Doulton ceramic shell and Aquasana filtration system.
Can my 1/2 micron CB protect me against bio-terrorism on our water supplies?
Not at all. For that you'll need a laboratory grade RO system, a filter with 1/2 micron or less absolute ANSI standard pore size, distillers and UV's to some extent.
Powdered Activated Carbon (PAC)
As with CB's, molded or powdered activated carbon (PAC) are very effective method of removing volatile organic compounds (insecticides, pesticides and industrial solvents) from drinking water. As with all carbon forms change these filters often and do not wait until quality of the water taste has deteriorated.
The best and only PAC filter made in USA is Multi-Pure solid carbon block.
NOTE: All POU activated carbon water filters should be used on microbiologically safe water only.
At last, here we are, more tech stuff which you have been patiently waiting for.
What is it all this stuff about microns, pore size ratings, nominal, absolute etc. means?
Pore size - Absolute vs. Nominal Microns (µm) Pore Ratings>>
Source: DoultonUSA
doc111
Well-Known Member
Hadn't forgotten...........I just hadn't gotten to it yet.
doc111
Well-Known Member
Water in Plants - Plant Biology
The movement of molecules, specifically water and any solutes, is vital to understand in light of plant processes. This will be more or less a quick review of several guiding principles of water motion in reference to plants.
Molecular Movement
Roughly 90% of the water that enters a plant is lost via transpiration. Transpiration is the loss of water vapor through the leaves, just to refresh you. In addition, less than 5% of the water entering the plant is lost through the cuticle. Water is vital to plant life, not just for turgor pressure reasons, but much of the cellular activities occur in the presence of water molecules and the internal temperature of the plant is regulated by water. Recall that the xylem pathways go from the smallest part of the youngest roots all the way up the plant and out to the tip of the smallest and newest leaf. This internal plumbing system, paired with phloem and its nutrient transportation system, maintains the water needs and resources in the plant. The issue of the processes by which water is raised through columnsof considerable height at timeshas been studied and debated for years in botany circles. The end result is the cohesion-tension theory.
The Cohesion-Tension Theory
Polar water molecules adhere to the walls of xylem tracheids and vessels and cohere to each other which allows an overall tension and form columns of water in the plant. The columns of water move from root to shoot and the water content of the soil supplies the columns with water that enters the roots via osmosis. The difference between the water potentials of the soil and the air around the stomata are capable of producing enough force to transport water through the plantfrom bottom to top and thus goes the cycle.
Transport of Food Substances (Organic Solutes) in Solution
Phloem is responsible for transporting food substance throughout the plant. As with water movement in plants, the movement of organic solutes in plants has been studied and debated for years. The currently accepted hypothesis is the pressure-flow hypothesis for the translocation of solutes.
The Pressure-Flow Hypothesis
This is essentially a source and sink hypothesis. Food substances that are in solution flow from a source, which is generally where water is taken up by osmosis (roots; food storage tissues, such as root cortex or rhizomes; and food producing tissues such as mesophyll in leaves), and the food substances are then given up at a destination or a sink where the food resources will be utilized in growth. The idea is that the organic solutes are moved along concentration gradients existing between sources and sinks.
At the source, phloem-loading occurs and sugars are moved by active transport into the sieve tubes of the smallest veins. The overall water potential in the sieve tube drops and then water enters the phloem cells via osmosis. The resulting turgor pressure from the movement of the water is enough to drive the solution through the sieve network to the sink . The sugar is unloaded at the sink via active transport and water then exits the ends of the sieve tubes. The pressure drops as the water exits, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. Much of the water that exits the sieve tubes will diffuse back into the xylem where it can be recirculated, transpired once it reaches the source. In a nutshell the mass flow is caused by drops in turgor pressure at the sink as the sugar molecules are removed. This generates the next push of materials toward the sink.
Regulation of Transpiration
It is the responsibility of the stomata to regulate transpiration and gas exchange via the actions of the guard cells. The pores of the stomata are closed when turgor pressure in the guard cells is low, and they are open when turgor pressure is high. Changes occur when light intensity, carbon dioxide concentration or water concentration change. The guard cells of the stomata use energy to take up potassium ions from adjacent epidermal cells.The uptake opens the stomata because water potential in the stomata drops and water moves into the guard cells and increases turgor pressure. When the potassium ions are released, the water then leaves the cells as the water potential shifts again. There is evidence that stomata will close with water stresses, but there also seems to be some indication that hormones are involved cause a loss of potassium ions from the guard cells and thus a pore closure.
Most plants keep their stomata open during the day and close them at night. However, there are plants that do the opposite and open their stomata during the night when overall water stress is lower. These plants have a specialized form of photosynthesis called CAM photosynthesis since the standard source of carbon dioxide is shut off as the stomata are closed during daylight hours. There are desert plants that are able to store carbon dioxide in their vacuoles in the form of organic acids that are converted back into carbon dioxide during the daytime for standard photosynthetic processes. As mentioned earlier, there are also adaptations such as sunken stomata which reduce the loss of water. Submerged or partially submerged plants generally do not have stomata on the underwater portions of their leaves.
High humidity will reduce transpiration rates while low humidity accelerates the process. There is a direct correlation between temperature and water movement out of the leaf. At high temperatures the rate of transpiration increases, while the opposite occurs at lower temperatures.
Mineral Requirements for Growth
Many external factors will affect growth rates and quality. The minerals available in the local soil is one such source of external input. Essential plant elements include: carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulphur, calcium, iron, magnesium sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum, and boron to name the most common. Other minerals are required but they vary greatly from plant to plant. For example some algae need large amounts of iodine and silicon, while some loco weed species need seleniumwhich is poisonous to cattle on its own.
Macronutrients and Micronutrients
When any of these elements are lacking in the soil and the deficiencies are not compensated for by adding fertilizer compounds of compost the plant will demonstrate characteristic symptoms of mineral deficiencies. Most commercial fertilizers are some ratio of nitrogen, phosphorus and potassium and thus are able to compensate for a wide variety of issues. As an example of uses for the essential element in plants we will look at a few elements and how they are utilized:
Nitrogenused in the building of proteins, nucleic acids and chlorophyll
Potassiumresponsible in the process of enzyme activation, usually found in the Meristems
Calciumvital part of the middle lamella and has a direct role in the movement of substances through cell membranes
Phosphorusvital role in respiration and cellular division also used in the synthesis of energy compoundsATP and ADP
Magnesiumcentral component of the chlorophyll molecule and involved in enzyme activation
Sulphurstructural component of many amino acids
Ironintegral in chlorophyll production and plays role in respiration
Manganeseenzyme activator
Boronrole in calcium ion use, not clearly understood
As you can see by scanning through the list, all of these elements are involved to one degree or another in vital life sustaining processes!
Source: Biology online
The movement of molecules, specifically water and any solutes, is vital to understand in light of plant processes. This will be more or less a quick review of several guiding principles of water motion in reference to plants.
Molecular Movement
- DiffusionDiffusion is the net movement of molecules or ions from an area of higher concentration to an area of lower concentration. Think of it as a rebalancing. The molecules or ions are said to be moving along a diffusion gradient. If molecules or ions moving in the opposite direction are said to be moving against a diffusion gradient. Diffusion will continue until a state of equilibrium is reached. Rates of diffusion are affected by temperature and the density of the involved molecules among other things. In the leaves, water diffuses out via the stomata into the atmosphere.
- OsmosisOsmosis in plant cells is basically the diffusion of molecules through a semipermeable, or differentially permeable, membrane from a region of higher solute concentration to a region of lower solute concentration. The application of pressure can prevent osmosis from occurring. Plant physiologists like to describe osmosis more precisely in terms of potentials. Osmotic potential is the minimum pressure required to prevent fluid from moving as a result of osmosis. Fluid will enter the cell via osmosis until the osmotic potential is balanced by the cell wall resistance to expansion. Any water gained by osmosis may help keep a plant cell rigid or turgid. The turgor pressure that develops against the cell walls as a result of water entering the cells vacuole. This pressure is also referred to as the pressure potential. The crunch when you bite into a celery stick is as a result of the violation of the cells turgor pressure. The osmotic potential and pressure potential combined make up the water potential of a plant cell. If there are two cells next to each other of different water potentials, water will move from the cell with the higher water potential to the cell with the lower water potential. Water enters plant cells from the environment via osmosis. Water moves because the overall water potential in the soil is higher than the water potential in the roots and plant parts. If the soil is desiccated then there will be no net movement into the plant cells and the plant will die.
- PlasmolysisPlasmolysis is the loss of water via osmosis and accompanying shrinkage of the protoplasm away from the cell wall. When this occurs, the cell is said to be plasmolyzed. This process can be reversed if the cell is placed in fresh water and the cell is allowed to regain its turgor pressure. However, as with anything living, there is a point of no return and permanent or fatal damage to the cell can occur.
- ImbibitionImbibition is the swelling of tissues, alive or dead, to several times their original volume. This is a result of the electrical charges on materials in suspension (colloidal) such as minerals, cellulose and starches attracting highly polar water molecules which then move into the cell. This swelling process is the initial step in the germination of seeds.
- Active TransportActive transport is the energy assisted movement of substances against a diffusion or electrical gradient. This process requires enzymes and a proton-pump embedded in the plasma membrane. The pumps are energized by ATP moleculesa cellular energy storage molecule.
Roughly 90% of the water that enters a plant is lost via transpiration. Transpiration is the loss of water vapor through the leaves, just to refresh you. In addition, less than 5% of the water entering the plant is lost through the cuticle. Water is vital to plant life, not just for turgor pressure reasons, but much of the cellular activities occur in the presence of water molecules and the internal temperature of the plant is regulated by water. Recall that the xylem pathways go from the smallest part of the youngest roots all the way up the plant and out to the tip of the smallest and newest leaf. This internal plumbing system, paired with phloem and its nutrient transportation system, maintains the water needs and resources in the plant. The issue of the processes by which water is raised through columnsof considerable height at timeshas been studied and debated for years in botany circles. The end result is the cohesion-tension theory.
The Cohesion-Tension Theory
Polar water molecules adhere to the walls of xylem tracheids and vessels and cohere to each other which allows an overall tension and form columns of water in the plant. The columns of water move from root to shoot and the water content of the soil supplies the columns with water that enters the roots via osmosis. The difference between the water potentials of the soil and the air around the stomata are capable of producing enough force to transport water through the plantfrom bottom to top and thus goes the cycle.
Transport of Food Substances (Organic Solutes) in Solution
Phloem is responsible for transporting food substance throughout the plant. As with water movement in plants, the movement of organic solutes in plants has been studied and debated for years. The currently accepted hypothesis is the pressure-flow hypothesis for the translocation of solutes.
The Pressure-Flow Hypothesis
This is essentially a source and sink hypothesis. Food substances that are in solution flow from a source, which is generally where water is taken up by osmosis (roots; food storage tissues, such as root cortex or rhizomes; and food producing tissues such as mesophyll in leaves), and the food substances are then given up at a destination or a sink where the food resources will be utilized in growth. The idea is that the organic solutes are moved along concentration gradients existing between sources and sinks.
At the source, phloem-loading occurs and sugars are moved by active transport into the sieve tubes of the smallest veins. The overall water potential in the sieve tube drops and then water enters the phloem cells via osmosis. The resulting turgor pressure from the movement of the water is enough to drive the solution through the sieve network to the sink . The sugar is unloaded at the sink via active transport and water then exits the ends of the sieve tubes. The pressure drops as the water exits, which causes a mass flow from the higher pressure at the source to the now lowered pressure at the sink. Much of the water that exits the sieve tubes will diffuse back into the xylem where it can be recirculated, transpired once it reaches the source. In a nutshell the mass flow is caused by drops in turgor pressure at the sink as the sugar molecules are removed. This generates the next push of materials toward the sink.
Regulation of Transpiration
It is the responsibility of the stomata to regulate transpiration and gas exchange via the actions of the guard cells. The pores of the stomata are closed when turgor pressure in the guard cells is low, and they are open when turgor pressure is high. Changes occur when light intensity, carbon dioxide concentration or water concentration change. The guard cells of the stomata use energy to take up potassium ions from adjacent epidermal cells.The uptake opens the stomata because water potential in the stomata drops and water moves into the guard cells and increases turgor pressure. When the potassium ions are released, the water then leaves the cells as the water potential shifts again. There is evidence that stomata will close with water stresses, but there also seems to be some indication that hormones are involved cause a loss of potassium ions from the guard cells and thus a pore closure.
Most plants keep their stomata open during the day and close them at night. However, there are plants that do the opposite and open their stomata during the night when overall water stress is lower. These plants have a specialized form of photosynthesis called CAM photosynthesis since the standard source of carbon dioxide is shut off as the stomata are closed during daylight hours. There are desert plants that are able to store carbon dioxide in their vacuoles in the form of organic acids that are converted back into carbon dioxide during the daytime for standard photosynthetic processes. As mentioned earlier, there are also adaptations such as sunken stomata which reduce the loss of water. Submerged or partially submerged plants generally do not have stomata on the underwater portions of their leaves.
High humidity will reduce transpiration rates while low humidity accelerates the process. There is a direct correlation between temperature and water movement out of the leaf. At high temperatures the rate of transpiration increases, while the opposite occurs at lower temperatures.
Mineral Requirements for Growth
Many external factors will affect growth rates and quality. The minerals available in the local soil is one such source of external input. Essential plant elements include: carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulphur, calcium, iron, magnesium sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum, and boron to name the most common. Other minerals are required but they vary greatly from plant to plant. For example some algae need large amounts of iodine and silicon, while some loco weed species need seleniumwhich is poisonous to cattle on its own.
Macronutrients and Micronutrients
When any of these elements are lacking in the soil and the deficiencies are not compensated for by adding fertilizer compounds of compost the plant will demonstrate characteristic symptoms of mineral deficiencies. Most commercial fertilizers are some ratio of nitrogen, phosphorus and potassium and thus are able to compensate for a wide variety of issues. As an example of uses for the essential element in plants we will look at a few elements and how they are utilized:
Nitrogenused in the building of proteins, nucleic acids and chlorophyll
Potassiumresponsible in the process of enzyme activation, usually found in the Meristems
Calciumvital part of the middle lamella and has a direct role in the movement of substances through cell membranes
Phosphorusvital role in respiration and cellular division also used in the synthesis of energy compoundsATP and ADP
Magnesiumcentral component of the chlorophyll molecule and involved in enzyme activation
Sulphurstructural component of many amino acids
Ironintegral in chlorophyll production and plays role in respiration
Manganeseenzyme activator
Boronrole in calcium ion use, not clearly understood
As you can see by scanning through the list, all of these elements are involved to one degree or another in vital life sustaining processes!
Source: Biology online
businessmen
Active Member
Actually sorry, I notice after I said that, you had a few sentences on the first page. Just meant to remind in case anyone wanted to know about it. 
doc111
Well-Known Member
No worries my friend.Actually sorry, I notice after I said that, you had a few sentences on the first page. Just meant to remind in case anyone wanted to know about it.
doc111
Well-Known Member
I don't have a brand preference. They are pretty much the same. The stealth r/o systems are popular. You can find a ton of reasonably priced r/o filters on e-bay. I've seen them for as low as $79!
smokie927
Active Member
very comprehensive post,this is the second one i've seen like this so far. I suggest keep it simple and get,"HANNA". Measures everything. The EC like most advanced nutrient measuring controllers is converted into TDS(total dissolved solids) Which is your ppm. Nice post Doc. Stay up Oregon.
doc111
Well-Known Member
I agree that people should keep it simple. Especially if you are new at this. The purpose of this thread is to educate people about the water they use, problems people run into with their water, to show them their purification options, etc.
Silky Shagsalot
Well-Known Member
smoke is a young jerk who thinks he knows it all, lol. the last s in kiss is smoke. LOL!!!
naww i think the post was great i feel sorry you wanted it simpler. Idiocracy here we come
doc111
Well-Known Member
Damn kids!!!
lol!
doc111
Well-Known Member
I appreciate that and I'm glad you found it helpful.
Tyrannabudz
Well-Known Member
Hydrogen Monoxide rocks!
doc111
Well-Known Member
...........Dihydrogen monoxide, aqua, l,eau, das wasser, it's all good!Hydrogen Monoxide rocks!
doc111
Well-Known Member
What's happening bro? I haven't seen you on here in a while. Thanks for the compliment. Bottled water is usually fine for growing. It typically has a little bit of calcium and magnesium to make it taste better which your plants need. And the pH is within range (although a bit on the low side). How's your grow going?