HYDROCYCLONE TECHNOLOGY TO REDUCE PLANT PATHOGENS IN IRRIGATION WATER

HYDROCYCLONE TECHNOLOGY TO REDUCE PLANT PATHOGENS IN IRRIGATION WATER Roy D. Lister Hydro-Separation Systems, Inc. (A Modular Protection for the Environment Company) Houston, TX 77077 ABSTRACT Plant pathogens in irrigation water is a serious problem and source of damage to crops and turf (especially seedlings) in the agriculture, nursery, and commercial lawn maintenance (e.g., golf course) industries. The problem of plant pathogens has historically been controlled by the application of chemical fungicides. This project proposes to evaluate the effectiveness of hydrocyclone technology to eliminate the problem at the source by reducing the presence of plant pathogens in irrigation water, and thereby eliminate or substantially reduce reliance on chemical fungicides. INTRODUCTION PROJECT DESCRIPTION Hydrocyclone technology has been employed by Hydro-Separation Systems to improve the quality of irrigation water by reducing the source of damping-off disease, namely plant pathogens such as pythium, in irrigation water. Damping-off disease is prevalent world wide, affecting many types of plants. The greatest damage is done to seeds and seedling roots. The fungus also may attack the fruits of older plants, causing the fruits to spoil in the field or in storage. Fungicides are typically used to control this plant disease. However, misapplication of fungicides or certain conditions, such as heavy rains, can spread the chemicals to streams and groundwater supplies. Thus, the project's goal is to reduce the use and environmentally negative effects of fungicides by reducing or eliminating the pfesence of plant pathogens. The improved quality of the water feed diminishes the need for the use of fungicides, thus reducing the amount of fungicide in the eventual run-off from the crop field. 79

Hydrocyclone technology is fairly simple. Pressure energy supplied to a water slurry by a pump is converted into centrifugal force due to the inside geometry of the hydrocyclone. A hydrocyclone is shown in Figure 1. Figure 1. Hydrocyclone FEED SLURRY c c P As the water spins, the heavier materials, such as dirt, are forced to the walls of the cone where they move down and out through the bottom opening. Clean water is displaced to the cone s center and exits through the top of the hydrocyclone. Up to 3000 g s of force are exerted on the particles at the bottom of the cone. This high sheer, it is believed, is responsible for the destruction of the plant pathogen population in the water. 80

Several benefits to the irrigation water were realized during the project: 1. The majority of plant pathogens were removed or destroyed; 2. Most bacteria were removed or destroyed; 3. Silt was removed, so that soil drainage was improved; and 4. Water was oxygenated for healthier plant growth. Figure 2 illustrates the irrigation system retrofit for cyclonic silt removal. Figure 2. Irrigation System Retrofit for Cyclonic Silt Removal IRRIGATION SYSTEM RETROFIT FOR CYCLONIC SILT REMOVAL 0"- -- Solids can be discharged to the water source, as depicted, or may be collected separately. 81

APPLICATION The hydrocyclone process is intended to reduce the need for fungicides in irrigation water, thus reducing environmental and health hazards associated with their use. Industries which could benefit from this technology include agriculture, turf farms, golf courses, and nurseries. All these industries intensely use water and management chemicals. Introducing a hydrocyclone into the irrigation system can greatly reduce the need for fungicides. PROCEDURE DEMONSTRATION Eleven test sites were part of this study: 8 golf courses (water sources: Trinity River, ponds, and city water); a peanut farm (water source: well water); a sod farm (water source: well water); and a nursery (water source: pond water fed by a well). Plant pathogens were found in water samples from all sites, while the pythium fungus was found at 7 of the 9 sites selected for that fungus. Hydro-Separation Systems constructed a mobile test unit for sampling procedures. It consisted of a trailer with both a gas powered and an electric driven pump, flexible hoses, and an aluminum test stand which supported a 3 inch hydrocyclone. At the test site, water was pumped for several minutes through the hoses from the source into the hydrocyclone at 45 pounds per square inch (psi). 2 gallons each of FEED water (water pumped into the hydrocyclone), OVERFLOW (clean processed water from the top of the hydrocyclone), and UNDERFLOW (approximately 5 percent of the feed volume plus dirt, silt, and debris) were taken to Texas A & M University s (TAMU) Dallas laboratory for analysis. The principal investigators at TAMU were Phillip F. Colbaugh, Ph.D., and Kirk Bond. Funai Tests At TAMU, 15 centimeter petri dishes were used for all fungal tests. For each 10 plates, 500 milliliters of corn meal agar was prepared. To the prepared agar was added 10 milligrams Primaricin, 200 milligrams Ampicillin, and 25 milligrams Rifamycin sv. 02

For each water sample, either 15 or 30 plates were prepared. mis number was dependent on the number of samples taken in a given week and the number of plates available.) 5 milliliters of the water sample was pipetted into each plate. The agar was poured over the water sample and quickly swirled to mix. The plates were allowed to set for 2 to 4 days until data was taken. Figure 3 depicts cumulative fungus data. Figure 3. Cumulative Fungus Data Cumulative Fungus Data Colony Mean Per Plate 10 0 6... 4 2 0 la lb 2a 2b 3 4 5 6 7 8 9 10 11 12 Site Identification Number -Feed =Over 03

Data were varied from each site. Values from the FEED ranged from 0.2 fungus colonies per plate to 8.3 colonies per plate. OVERFLOW values ranged from 0 to 24 colonies per plate. UNDERFLOW ranged from 0 to 120 colonies per plate. The total data mean demonstrated a decrease in fungal colonies per site mean from FEED to OVERFLOW of 16.0 to 6.0, or a decrease of 62.5 percent. However, using a mean percent decrease, the reduction was 45 percent due to an unusually high data set from one of the sites. This decrease, although significant, does not follow the 20:l concentration factor expected by Hydro-Separator. The high data variation suggests that multiple factors, including fungus size, determine what portion of fungi are removed. Pvthium Tests In examining Pythium removal, the percent decrease from FEED to OVERFLOW was 54.5 percent. The data suggests that on a larger scale, Pythium removal is no different than that of other fungi. The Hydro-Separator does not select for a specific fungus type. Bacteria Tests The Hydro-Separator was also tested for bacteria removal. For each sample, FEED, OVERFLOW, and UNDERFLOW, a separate dilution chain was set up. 10 milliliters of sample were placed in an autoclaved graduated cylinder with 90 milliliters autoclaved deionized water. The top was covered with parafilm and the mixture shaken. 2 milliliters of this 1:lO mixture were added to 18 milliliters of water in a test tube to yield a 1:lOOO mixture. The 1500 dilution was obtained by adding 1 milliliter of the mixture to 4 milliliters of water in a test tube. From each dilution, 1 milliliter of sample was pipetted into the bottom of a disposable petri dish. Plate count agar was poured directly into the plates which were then inverted to inhibit fungus growth. Readings were taken after 2 to 3 days, and dilutions which quantitatively fell between 30 and 300 bacteria per plate were used for analysis. The following different plating dilutions and counting techniques were used. The correction factors account for the use of two different sizes of petri dishes..- Method 1 - No dilution. Since plate counts were so high, a 4 square centimeter on each plate was measured and the number of colonies found in that square was multiplied by 38.47 to get the correct plate area of 153.86 square centimeters. Method 2 - Three replications each of 1 :lo0 and 1500 dilutions were made. All but one set were full plate counts. One set, with a high number of colonies, 84

Discussion used a partial plate count Of 4 square centimeters. The count was multiplied by 19.6 to get a total area of 78.5 square centimeters. Method 3 -- Five replications each of 1 :lo0 and 1500 dilutions were made. Certain sets were partial plate counts of 4 square centimeters. These numbers were multiplied by 19.6 to get a total area of 78.5 square centimeters. Method 4 -- Five replications each of 1:lOO and 1:5OO dilutions were made. All were total plate counts. In accordance with standard microbiological principles, the data chosen was the set with values which fell closest to the range of 30 to 300. The means found suggest that the OVERFLOW had 74 percent of the bacteria removed. However, computed on a mean percent, it was 50 percent; the 74 percent, as in the fungus report, is inflated due tounusually high data sets. The decrease of 50 percent is very close to the 45 percent decrease found in the fungus experiments. Likewise, the UNDERFLOW was concentrated 680 percent, however not all sites had concentrations and removals to these degrees. Further study is necessary for conclusive results on the Hydro-Separator's potential to remove bacteria from the water supply. Dissolved Oxvaen Content The violent action of the Hydro-Separator suggests the machine could be used to enhance the dissolved oxygen content of water samples. From each site, three standard samples were taken: FEED, OVERFLOW, and UNDERFLOW. Measurements were done at either the laboratory or on site using a Cole-Parmer 5946-50 Oxygen Meter. For each sample, three replications were done, and a mean taken. The original measurement was in parts per million dissolved oxygen which was taken after the meter was calibrated using air temperature. From this, the percent saturation of dissolved oxygen could be taken using the water temperature. RESULTS AND DISCUSSION PERFORMANCE RESULTS _- It is technically feasible to use hydrocyclones to remove pythium from irrigation water. The average removal (all test sites) was 70 percent. 85

From material balances, approximately 60 percent of the original pythium was actually destroyed, about 10 percent of the original number of pythium colonies being discarded with the silt, while the remaining 30 percent left the hydrocyclone with the "clean" water. Other plant pathogens are affected by the hydrocyclone. A material balance of the total fungi counts indicates that 54 percent of the original total fungi are destroyed, 70 percent of the total fungi are "d from the "Clean" water, with 16 percent discarded with the solids in the underflow. The hydrocyclone has a pronounced effect on bacteria, probably due to the combined effects of high shear and the saturation of the water inside the hydrocyclone with oxygen. From a mas balance perspective, 74 percent of the bacteria are destroyed, with only about 1 percent of the original bacteria exiting the cone with the solids and the remainder staying with the "clean" water.. The hydrocyclone causes the water to become saturated with oxygen - an average level of 98.6 percent for the 12 sites tested. This finding is significant in the application of the hydrocyclone technology to areas such as agriculture and waste water treatment. The resulting data suggests that the Hydro-Separator is beneficial to water samples whose dissolved oxygen is below 95 percent. For sites categorized as LOW oxygen (80 percent or less), sites experienced a mean 27 percent increase in oxygen content. INTERMEDIATE samples (80 percent to 95 percent dissolved oxygen) showed a mean increase of 14 percent. Samples in the HIGH category (above 95 percent) showed no increase in oxygen saturation. One sample was significantly higher in initial saturation (137.2 percent), and the action of the Hydro-Separator seemed to cause an equilibrium effect, bringing the reading close to the 100 percent level. Product Qualitv Variance In fungi removal from different test sites, there was a wide variation in the efficiency of the hydrocyclone, from complete removal of fungi in the "clean" stream, to only 10 percent removal at one of the sites. Hydro-Separation believes this variation is due to the difficulty in obtaining consistent biological samples. For example, the two extremes are related to very low fungi populations in the feed water samples, so that any effects have extraordinary weight on the results. 86

Conditions That Impact Performance A number of process variables, such as pump pressure, underfiow orifice size, percent solids in the feed water, water temperature, and water viscosity (concentration of clays) could affect the efficiency of the hydrocyclone in destroying or removing fungi. Tabulation of Data Taking TAMU s data and adjusting it to account not only for the concentration, but also for the relative amounts of fungi present in the FEED, OVERFLOW (OF), and UNDERFLOW (UF), based on a flow split, where 90 percent is OF and 10 percent is UF, Table 1 presents a clearer picture of the fate of the fungi. Table 1. Fungi Removed or Destroyed 07

Percent fungi destroyed = 11.657-7481~ 100 = 54% of original 1,657 Percent fungi removed from OF (clean water) = J1.657-489l x 100 = 70% 1,657 Percent fungi in UF = 259 x 100 = 16% 1,657 Percent fungi in OF (clean water) = 489 x 100 = 30% 1,657 Teed and OF data have been reversed from TAMU report because of sample misidentification. Table 2 treats the data related to pythium in the same manner as previously shown. Table 2. Pythium Removed or Destroyed Percent Pythium destroyed = 1263-105) x 100 = 60% of original 263 Percent qnhium removed from OF (clean water) = 1263-479) x 100 = 70% 263 Percent qnhium in UF = 26 x 100 = 10% 263 88

Percent Pythium in OF (clean water) = 79 x 100 = 30% 263 Usable bacteria data were calculated as shown in Table 3. Table 3. Useable Bacteria 9 3 6 5 2a * lb 614 39 5 44 536 271 2 273 45 35 7 42 49 36 2 38 327 15 10 25 427 90 6 96 ~- Total 1,998 406 32 518 L Percent bacteria destroyed = f1.998-5181 x 100 = 74% of original 1,998 Percent bacteria removed from OF (clean water) = 11,998-486) x 100 = 75% 1,998 Percent bacteria in UF = 36 x 100 = 1% 1,998 Percent bacteria in OF (clean water) = 486 x 100 = 25% 1,998 Cost-Benefit Analvsis As this project did not involve a product or process improvement, quantifying a cost benefit is elusive. A 70 percent reduction in plant pathogens does not necessarily mean a corresponding 70 percent reduction in fungicide use. However, it is possible that less fungicide would be needed. As plant pathogens develop resistance to the various fungicides, alternate methods of plant disease control will become necessary; 89

hydrocyclone technology to improve water quality could be a beneficial tool in plant disease control. Consequently, a reduction in the use of fungicides decreases fungicide run-off from fields. While a cost-benefit analysis to estimate the use of hydrocyclone technology to supplement fungicide use is beyond the scope of this project, it appears that thousands of dollars from reduced fungicide use could be saved each year. The cost range for equipment ranges from $lo,ooo to $5O,OOO with a payback in 3-5 years. For example, according to the Golf Course Superintendent s Association of America, there were 13,004 courses in the United States in 1992 that each spent an average of over $8,000.00 on fungicide or $104,000,000.00. If fungicide use could be halved using a hydrocyclone system, the savings in fungicide could average $4,000.00 per year per course or over $so,ooo,ooo.00 for 1992. Projections of fungicide usage in 1993 are $1 40,000,000.00, thus the potential savings are $70,000,000.00. This savings in fungicide costs is in addition to extending the life of the greens by reducing the amount of silt deposited. Considering approximately half of the 13,000 courses have silt problems, which require them to replace their greens on an average of five to ten years, a savings of $25,000.00 to $5O,OOO.00 per year for 6,500 courses would translate to $162,500,000.00 to $325,000,000.00 per year for the industry. In addition to the monetary payback is the reduced risk of pollution and health problems by reducing the use and dependency on fungicides. CONCLUSIONS POLLUTION PREVENTION ASSESSMENT The hydracyclone can be used to reduce plant pathogens in imgation water. A measure of the actual effects on the health of seeds and seedlings is needed. Does an immediate reduction of the quantity of fungi in irrigation water allow a significant reduction in the amount of fungicide applied without adverse effects to the seeds and saedlings? Controlled, documented studies may allow the application of this technology to improve yields, reduce crop losses, lessen heajth hazards, and reduce fungicide pollution in the environment. Industries, such as agriculture, turf, and golf course maintenance, which depend on irrigation water, would benefit from this technology. The publicity resulting from Hydro-Separation System s grant spawned a new Texas corporation, AGKONE. This company uses hydrocyclone technology to manage wash water from dairy bams that is typically sent to holding lagoons.

AGKONE pumps this water through a hydrocyclone before sending it to the lagoons. The lagoons with hydrocyclone treated water are odor-free, with water quality similar to stock ponds. The solids removed from the water are also odor-free. The solids can be used as fertilizer, burned as fuel, or even re-fed after further enhancement. Hydro-Separation Systems has employed hydrocyclones in such industrial applications as cleaning foundry and sawmill scrubber water, extending coqlant life in metalworking shops, and removing solids from oil drilling muds. The Company s focus has recently shifted to environmental concems, including agriculture wastewater from dairy, swine, and poultry operations, the aquaculture industry, and irrigation water. 91