Abstract:
A method of preventing the formation of microbiological deposits in the water delivery systems of micro-irrigation systems which have in addition to water delivery systems, a water filtration system, a pump and a water distribution system. This method comprises cleaning the micro-irrigation system to remove existing microbiological deposits thereby providing a clean distribution and delivery system, and then continuously treating the water fed to the delivery system with a few ppm of glutaraldehyde to maintain cleanliness. The invention is particularly effective in controlling microbiological deposits which are either slimes or algae or mixtures thereof.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The prevention of microbiological deposits in micro-irrigation systems.  
           [0003]    2. Description of the Prior Art  
           [0004]    Micro-irrigation systems are utilized extensively for growing crops throughout the world. These systems provide a very uniform distribution of water directly to the irrigated crop in the most cost effective manner. Micro-irrigation is replacing the older methods of irrigation such as flood, furrow, ditch, and overhead sprinkler irrigation because of the ever increasing shortage of water supplies and increased cost of these water supplies. Since micro-irrigation dramatically lowers the cost of the irrigation process, almost every grower is driven to use this method of irrigation to survive the economic pressures of today&#39;s world.  
           [0005]    Micro-irrigation systems typically include the following:  
           [0006]    1. A source of water, which is usually a reservoir, canal, stream or well.  
           [0007]    2. A pump to deliver the water.  
           [0008]    3. A filtration system for removing particulate or other debris.  
           [0009]    4. A distribution system, which consists of an extensive network of pipes and valves.  
           [0010]    5. A delivery system, which is the heart of the micro-irrigation system. There are many types of delivery systems that are used to accomplish the accurate delivery of the water. Among these delivery systems are: in-line emitters (both pressure compensated and non-pressure compensated); drip tape (both pressure compensated and non-pressure compensated); external emitters (both pressure compensated and non-pressure compensated); and micro-sprinklers (both pressure compensated and non-pressure compensated).  
           [0011]    The major problem that results during the use of the micro-irrigation system occurs because of the unique design of these very effective water delivery systems. The problem arises because the water sources are usually laden with microorganisms. In the case of surface waters, such as reservoirs, canals or streams, the major biological problem is in the form of algae. In the case of wells, the major problems are slimes, which contain iron-bacteria and manganese-bacteria. These bacteria convert water soluble species of iron and manganese compounds into insoluble forms thereof.  
           [0012]    The suppliers of micro-irrigation systems have tried to eliminate these microbiological problems by installing filtration systems. While these filtration systems do remove some debris and particulates, but due to the very large flow rates of water (typically 1000 gallons per minute), these sand-media, screen, and synthetic-media filters are not completely efficient for removing all of these biological contaminants. Although significant amounts of algae, slime and particulate compounds of iron and manganese are removed via filtration, there is still a small amount of these materials that are passed through the filtration system. In the case of algae and slimes, both of these biological entities are simply extruded through the filters. With iron and manganese bacteria most of the insoluble compounds of iron and manganese are removed by the filter. However, there is always some soluble iron and manganese that cannot be filtered out and the bacteria are too small in size to be stopped by the filter. It is these unforeseen and unexpected low levels of biological contaminants that this invention addresses and eliminates.  
           [0013]    In ordinary water delivery systems these low levels of biological contaminants would not be a problem. However, these micro-irrigation systems quite unexpectedly lend themselves to an exacerbation of these biological problems. As mentioned previously, the manufacturers of these micro-irrigation systems provide filtration that should alleviate the potential microbiological problems. The unexpected problem arises in that even very low levels of microbiological contaminants pass through the filtration system. These contaminants are then subjected to an environment at the end of the micro-irrigation system that leads to an “incubator” for microbial growth that is unique to micro-irrigation and is not present in other water delivery systems. This “incubator” effect happens in the delivery system. The delivery system precisely controls the water delivery to each individual plant in the crop that is being irrigated by an emitter or micro-sprinkler. These devices, as well as the rest of the plastic that comprises the drip pipe, tape or tubing, is made of a black plastic, such as polyethylene or PVC or other plastic that is impregnated with a black colorant. The manufacturers of the system have incorporated the black colorant into the plastic for UV stabilization of the plastic. Although this colorant does an excellent job at prolonging the life of the plastic components, the black plastic absorbs sunlight and is warmed during the day, providing perfect temperatures for the “incubator” effect. The other unexpected problem results because of the design for precise water control to each plant that is being irrigated. The emitter or micro-sprinkler that is delivering water to an individual plant is designed with either a soft plastic diaphragm and/or a torturous pathway for restriction of water flow. In either case, the device has a section that restricts the water flow. It is because of this unique design that it delivers a precise rate of water to the irrigated plant. As a result of the design and configuration of all commercial irrigation delivery devices, small amounts of light can penetrate the orifice of the device.  
           [0014]    In the case of algae, this light level is sufficient to allow for the growth of the very low levels of algae that have passed through the filtration system. The worst-case scenario occurs with a light source and the warm temperature of the black components. With both light and heat the algae proliferate on the diaphragm of the emitter and/or in the torturous pathway in the device. When this happens, depending on the design of the device, the device plugs or “sticks” open. In either case, this situation causes severe problems with the operation of the micro-irrigation system. Plugging results in less water being delivered to the plant, and pressure builds up in the overall irrigation system as more and more devices plug. This causes poor crop development, increased cost resulting from over irrigating to get enough water distributed throughout the field, and increased energy costs to operate the system at higher pressures. When a device flows open an even worse scenario develops. In this case, when many devices “stick” open many portions of the field are over irrigated. At first this would not seem to be a major problem. However, if some parts of the field have excess water delivered, other portions will be under-irrigated. This commonly occurs because irrigation systems have been designed to deliver a maximum amount of water. If too much water flows out of one section, insufficient capacity is left for the remainder of the field. This is particularly a problem in elevated or rolling terrains, where the lower parts of the field are over irrigated, and the upper elevations receive no water.  
           [0015]    In the case of slimes or iron/manganese bacteria, light is not required, but a similar problem still results. Many crops are not irrigated every day. On the off days, this same “incubator” effect is in place to provide an ideal temperature for growth of the slimes and iron/manganese bacteria. When bacteria or slimes are present there is another unexpected problem that happens as a result of the emitter or micro-sprinkler design. When the system is off there is no water pressure on the irrigation system and the emitters or micro-sprinklers are “open to the environment”. When the irrigation system is depressurized the delivery device is open to the environment. In pressure-compensating delivery devices this occurs when the diaphragm relaxes and opens to the atmosphere. In the case of non pressure-compensating delivery devices, the tortuous path of the emitter simply is open to the atmosphere when no water is flowing. Again, in either case, air exchange can take place between the water delivery device and the environment. When this happens the damp, warm delivery device is now under aerobic conditions, where slimes and bacteria can proliferate, and plug the device or cause the device to “stick” open and deliver too much water on the next irrigation cycle.  
         SUMMARY OF THE INVENTION  
         [0016]    A method of preventing the formation of microbiological deposits in the water delivery systems of micro-irrigation systems which have in addition to water delivery systems have a water filtration system, a pump and a water distribution system. The method comprises cleaning the micro-irrigation system to remove existing microbiological deposits thereby providing a clean distribution and delivery system, and then treating, preferably continuously, the water fed to the delivery system with a few ppm of glutaraldehyde. The term, “cleaning” as used herein and in the claims includes new start-up systems that have not previously been used to delivery irrigation water.  
           [0017]    In a preferred embodiment the glutaraldehyde is continuously fed to the delivery system and is added after the filtration system. The microbiological deposits are most commonly bacterial slimes, algae or mixed bacterial slimes and algae. Most often these slimes have as a portion of their makeup iron and magnesium bacteria which convert soluble forms or iron and manganese into insoluble forms of these metals.  
           [0018]    One of the important aspects of the invention resides in the fact that the glutaraldehyde maintains these micro-irrigation systems in a clean condition using a relatively low dosages thereof. Specifically, the glutaraldehyde may be applied at a dosage ranging between 0.1-10 ppm. In a preferred embodiment the dosage may range between 0.5-5 ppm. Typical of the low dosages that produce excellent results are those ranging between 1-5 ppm.  
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    The laboratory test study was conducted by developing an accelerated method by which various dosages of glutaraldehyde could be evaluated. Since it may take an entire growing season to accumulate enough biological deposit in a delivery device to cause plugging or a “stuck open” condition, a laboratory screening study was developed to test the efficacy of various glutaraldehyde dosages under a worse case scenario. To accomplish this screening test, a common emitter used by many growers was chosen as the test case. This emitter is a diaphragm-type pressure-compensating emitter (Rain Bird). To obtain emitters that already had a build-up of a biological contamination, a site was chosen where the emitters had been known to be malfunctioning. In the case of the Rain Bird emitters, a prelude to plugging is when these emitters begin to “spit”, in all directions, instead of just dripping down toward the ground. The “spitting” characteristic made the detection of potentially problematic emitters easy to identify. To obtain a good distribution, 100 of these problem emitters were taken from the field and put through the screening study.  
         [0020]    To determine if there was a biological deposit built up in these emitters, five emitters were selected randomly and cut open to observe the biological deposit. Since the water source was a reservoir, the deposit was mostly algae as determined by visual inspection. The deposit was determined to be of significant quantity in these emitters so as to utilize them in the screening study.  
         [0021]    To obtain a water sample from the source of the water, two five-gallon samples of the reservoir water were taken after the filtration system. This water was used for all subsequent laboratory testing. In between testing periods this water was stored under refrigerated temperatures to minimize any additional microbiological growth.  
         [0022]    Since cost is extremely important for the grower, only two dosage levels were chosen to study. These levels were 1 ppm and 5 ppm active glutaraldehyde. The test procedure for evaluation was as follows:  
         [0023]    1. 100 ml of test solution was passed through each tested emitter to ensure the treatment had thoroughly passed through the emitter. This was accomplished by means of a positive displacement pump that pumped at a rate of about 200 ml per 5 minutes.  
         [0024]    2. For the control, twenty-five such emitters were treated with just the filtered reservoir water, as indicated in step 1. All twenty-five emitters where then placed in a 1 quart Mason jar containing 500 ml of the filtered reservoir water. This Mason jar was then placed in the sun for the prescribed period of time.  
         [0025]    3. For the 1 ppm treatment, twenty-five such emitters were treated with the filtered reservoir water, as indicated in step 1, to which was added 1 ppm active glutaraldehyde. All twenty-five emitters were then placed in a 1-quart Mason jar containing 500 ml of the filtered reservoir water containing 1 ppm glutaraldehyde. This Mason jar was then placed in the sun for the prescribed period of time.  
         [0026]    4. For the 5 ppm treatment twenty-five such emitters were treated with filtered reservoir water, as indicated in step 1, to which 5 ppm active glutaraldehyde was added. All twenty-five emitters were then placed in a 1-quart Mason jar containing 500 ml of the filtered reservoir water containing 5 ppm glutaraldehyde. This Mason jar was then placed in the sun for the prescribed period of time.  
         [0027]    5. To test the efficacy, five emitters from steps 2, 3, and 4 were removed from the Mason jars at various intervals and treated as described below. To remove any residual treatment and to simulate flow conditions through the emitter, distilled water was passed through each emitter at a rate of approximately 35 ml per minute for 24 hours. At the end of the 24 hour flush treatment, the emitters were cut open and inspected for any visual biological debris. To ensure the emitters remaining in the Mason jar experienced a fresh treatment, steps 1, 2, 3 and 4 were redone on all the remaining emitters.  
         [0028]    6. The time intervals for evaluation of the control and the two glutaraldehyde dosage levels were as follows: 0 days, 10 days, 20 days, 30 days and 45 days.  
         [0029]    The results of this study can be seen in Table I, Table II, Table III, Table IV and Table V.  
                           TABLE I                       Time   Emitter   Dosage Level           Period   Number   (glutaraldehyde)   Visual Observation                   0 days   1   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   2   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       0 days   3   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   4   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 95% covered.                   Rating 100% alive.       0 days   5   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 95% covered.                   Rating 100% alive.       0 days   1   1 ppm   Diaphragm completely                   covered with green deposit.                   Rating 95% covered.                   Rating 100% alive.       0 days   2   1 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       0 days   3   1 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       0 days   4   1 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   5   1 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   1   5 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   2   5 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       0 days   3   5 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       0 days   4   5 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       0 days   5   5 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.                  
 
         [0030]    [0030]                           TABLE II                       Time   Emitter   Dosage Level           Period   Number   (gluraldehyde)   Visual Observation                   10 days   1   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       10 days   2   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       10 days   3   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       10 days   4   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 95% covered.                   Rating 100% alive.       10 days   5   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       10 days   1   1 ppm   Diaphragm mostly covered                   with brown/green deposit.                   Rating 85% covered.                   Rating 80% alive.       10 days   2   1 ppm   Diaphragm mostly covered                   with brown/green deposit.                   Rating 90% covered.                   Rating 80% alive.       10 days   3   1 ppm   Diaphragm mostly covered                   with brown/green deposit.                   Rating 90% covered.                   Rating 85% alive.       10 days   4   1 ppm   Diaphragm mostly covered                   with brown/green deposit.                   Rating 85% covered.                   Rating 85% alive.       10 days   5   1 ppm   Diaphragm mostly covered                   with brown/green deposit.                   Rating 90% covered.                   Rating 80% alive.       10 days   1   5 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 20% covered.                   Rating 0% alive.       10 days   2   5 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 30% covered.                   Rating 0% alive.       10 days   3   5 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 30% covered.                   Rating 0% alive.       10 days   4   5 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 25% covered.                   Rating 0% alive.       10 days   5   5 ppm   Diaphragm partly covered                   Rating 10% covered.                   Rating 0% alive.                    
         [0031]    [0031]                           TABLE III                       Time   Emitter   Dosage Level           Period   Number   (glutaraldehyde)   Visual Observation                   20 days   1   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       20 days   2   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       20 days   3   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       20 days   4   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 110% covered.                   Rating 100% alive.       20 days   5   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       20 days   1   1 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 40% covered.                   Rating 5% alive.       20 days   2   1 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 25% covered.                   Rating 0% alive.       20 days   3   1 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 25% covered.                   Rating 0% alive.       20 days   4   1 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 30% covered.                   Rating 5% alive.       20 days   5   1 ppm   Diaphragm partly covered                   with brown deposit.                   Rating 35% covered.                   Rating 5% alive.       20 days   1   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       20 days   2   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       20 days   3   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       20 days   4   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       20 days   5   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.                    
         [0032]    [0032]                           TABLE IV                       Time   Emitter   Dosage Level           Period   Number   (glutaraldehyde)   Visual Observation                   30 days   1   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       30 days   2   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       30 days   3   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 95% covered.                   Rating 100% alive.       30 days   4   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       30 days   5   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       30 days   1   1 ppm   Trace of brown deposit                   on diaphragm.                   Rating 5% covered.                   Rating 0% alive.       30 days   2   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   3   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   4   1 ppm   Trace of brown deposit                   on diaphragm.                   Rating 10% covered.                   Rating 0% alive.       30 days   5   1 ppm   Trace of brown deposit                   on diaphragm.                   Rating 5% covered.                   Rating 0% alive.       30 days   1   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   2   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   3   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   4   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       30 days   5   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.                    
         [0033]    [0033]                           TABLE V                       Time   Emitter   Dosage Level           Period   Number   (glutaraldehyde)   Visual Observation                   45 days   1   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       45 days   2   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       45 days   3   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       45 days   4   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 105% covered.                   Rating 100% alive.       45 days   5   0 ppm   Diaphragm completely                   covered with green deposit.                   Rating 100% covered.                   Rating 100% alive.       45 days   1   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   2   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   3   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   4   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   5   1 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   1   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   2   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   3   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   4   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.       45 days   5   5 ppm   Diaphragm free of deposits.                   Rating 0% covered.                   Rating 0% alive.                    
         [0034]    This invention overcomes these unexpected biological problems that occur in micro-irrigation systems by treating the irrigation water with very low levels of glutaraldehyde. What makes this treatment process unique is that very low levels of glutaraldehyde can be dosed because the bulk of the biological load in normal ground and/or surface waters are removed, via the filtration process. A small maintenance level, typically lppm glutaraldehyde is added to all irrigation water. As a result, this threshold level of glutaraldehyde maintains a clean delivery device so that none of the aforementioned problems arise. The result is a micro-irrigation system that remains free of microbial growth in the delivery devices and that is capable of delivering water to each plant precisely, and according to the manufacturer&#39;s specifications.  
         [0035]    The micro-irrigation systems may be cleaned prior to the initiation of the low levels of glutaraldehyde using known methods for removing scale and microbiological deposits. For instance, such techniques as mild acid cleaning may be used. Preferred is the use of biocides such as chlorine or mixtures of chlorine and bromine and glutaraldehyde at high dosages, e.g. 20 ppm or more for several days to provide a clean deposit-free system.  
         [0036]    The invention is applicable for treating micro-irrigation systems utilizing such mechanical delivery systems as drip hoses with in-line emitters, drip hose with external emitters, drip tapes and micro-sprinklers. Any of the above type systems may be either pressure or non-pressure compensated type systems.  
         [0037]    Finally, it should be noted that in addition to being effective at extremely low dosages, glutaraldehyde is a safe biocide which is important since many well known yet effective biocides such as formaldehyde are not capable of being used in micro-irrigation applications due to local and federal laws.