Biological Treatment Of Clogged Emitters

Journal of Environmental Management 76 (2005) 338–341 www.elsevier.com/locate/jenvman

Biological treatment of clogged emitters in a drip irrigation system ¨ mer Anapalıa, Mesude Figen Do¨nmezb, Fikrettin S¸ahinb,c,* ¨ stu¨n S¸ahina, O U a

Department of Agricultural Structures and Irrigation, Faculty of Agriculture, Ataturk University, 25240 Erzurum, Turkey b Department of Plant Protection, Faculty of Agriculture, Ataturk University, 25240 Erzurum, Turkey c Biotechnology Application and Research Center, Ataturk University, 25240 Erzurum, Turkey Received 18 March 2004; accepted 10 February 2005

Abstract This study was conducted to investigate microbial organisms that can be used for preventing clogging in drip irrigation systems caused by biological factors. A total of 25 fungi isolate and 121 bacterial strains were isolated from water samples collected from drip irrigation systems in tomato greenhouses in the eastern Anatolia region of Turkey in the spring season of 2001. Biological clogging of emitters in a model drip irrigation system was experimentally caused by application of the microorganisms (fungi and bacteria) isolated in the study. Three antagonistic bacterial strains in the genus Bacillus spp (ERZ, OSU-142) and Burkholdria spp (OSU-7) were used for treatment of biological clogging of the emitters. The results showed that the antagonistic bacterial strains tested have the potential to be used as anti-clogging agents for treatment of emitters in drip irrigation system. This is the first study that demonstrated that antagonistic microorganisms can be utilized for treatment of clogging in drip irrigation systems. q 2005 Elsevier Ltd. All rights reserved. Keywords: Biological treatment; Drip irrigation; Emitters; Antagonistic bacteria; Anti-clogging agent

1. Introduction Drip irrigation, also called trickle irrigation or microirrigation, is a localized irrigation method that slowly and frequently provides water directly to the plant root zone (Evans, 2000). It is known as a low cost water delivery system. Due to limited water resources and environmental consequences of common irrigation systems, drip irrigation technology is getting more attention and playing an important role in agricultural production, particularly with high value cash crops such as greenhouse plants, ornamentals and fruit. Therefore, use of drip irrigation systems is rapidly increasing around the world. Emitter clogging has often been recognized as inconvenient and one of the most important concerns for drip irrigation systems, resulting in lowered system performance and water stress * Corresponding author. Address: Department of Plant Protection, Faculty of Agriculture, Ataturk University, 25240 Erzurum, Turkey. Tel.: C90 442 231 2610; fax: C90 442 231 1469. ¨ . S¸ahin), fsahin@atauni. E-mail addresses: [email protected] (U ¨ . S¸ahin). edu.tr (U

0301-4797/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2005.02.003

to the non-irrigated plants (Povoa and Hills, 1994; Capra and Scicolone, 1998). Partial and total plugging of emitters is closely related to the quality of the irrigation water, and occurs as a result of multiple factors, including physical, biological and chemical agents (Gilbert et al., 1981; Pitts et al., 1990; Coelho and Resende, 2001). Favorable environmental conditions in drip irrigation systems can cause rapid growth of several species of algae and bacteria resulting in slime and filament buildup, which often become large enough to cause biological clogging (Gilbert and Ford, 1986). On the other hand, some of the bacterial species may cause emitter clogging due to the precipitation of iron, manganese and sulfur minerals dissolved in irrigation water (James, 1988; Pitts et al., 1990). Filtration, chemical treatment of water and flushing of laterals are means generally applied to control emitter clogging (Nakayama and Bucks, 1991). Physical clogging can be eliminated with the use of fine filters and screens. Chemical precipitation can be controlled with acid injection. However, biological clogging is quite difficult to control. Chlorination is the most common practice used in the prevention and treatment of emitter clogging caused by algae and bacteria (Pitts et al., 1990; Yuan et al., 1998; Coelho and Resende, 2001; Hills and

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Brenes, 2001). Calcium hypochlorite, sodium hypochlorite, and particularly chlorine are the most common and inexpensive treatments for bacterial slimes and for inhibition of bacterial growth in drip irrigation systems (Howell et al., 1983; Evans, 2000; ASAE Standards, 2001). However, continuous chlorination would increase total dissolved solids in the irrigation water and would contribute to increased soil salinity (Hills et al., 2000). These problems have forced scientists to find an environmentally friendly method for treatment of biological clogging. Some of the microorganisms have been previously reported to be antagonistic and have been used for biological control of pathogenic microorganisms in agricultural crop production (Es¸itken et al., 2002; Kotan and S¸ahin, 2002). They may be useful for development of an alternative method of controlling biological clogging of emitters in drip irrigation systems. However, there has been no attempt to study the development and application of biological methods for treatment of emitter clogging. Therefore, the objectives of this study were: (1) to identify potential microorganisms with antimicrobial activity on the microbial flora isolated from drip irrigation systems and (2) to develop a biological method for treatment of biologically clogged emitters in drip irrigation systems.

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2.2. Evaluation of antagonistic bacterial strains against microflora of drip irrigation system Three bacterial strains (Bacillus OSU-142, Bacillus ERZ and Burkholdria OSU-7) determined to exhibit strong antagonistic activity in previous studies (Kotan et al., 1999; Es¸itken et al., 2002; Kotan and S¸ahin, 2002) were tested against each of the fungi isolates and bacterial strains isolated in the present study according to the in-vitro tests described previously (Kotan and S¸ahin, 2002). All of the three bacterial strains were found to have the potential to be used in the treatment of biologically clogged emitters in drip irrigation systems. 2.3. Preparation of bacterial suspension for biological treatment All three antagonistic bacterial strains (Bacillus OSU-142, Bacillus ERZ and Burkholdria OSU-7) were grown on nutrient agar. A single colony from each culture was transferred to a 500-mL flask containing nutrient broth (NB), and grown aerobically in the flask on a rotating shaker (150 rpm) overnight at 30 8C. The nutrient broth with bacterial growth was then diluted in sterile distilled water containing 0.025% Tween 20 to a final concentration of 109 CFU/mL, and used for biological treatment of biologically clogged emitters in a drip irrigation system.

2. Materials and methods 2.4. Design and operation of a model drip irrigation system 2.1. Sample collection, microorganism isolation and culture conditions In the spring of 2001, a total of 17 water samples with microbial growth were collected from drip irrigation systems of tomato greenhouses, where biological clogging of emitters was observed, in the eastern Anatolia region of Turkey. Each sample (10 mL) was mixed with 90 mL of sterile peptone water by shaking in a Stomacher (Gerhardt, Germany) for 5 min. Then decimal dilutions of the resulting suspension in 9% (w/v) NaCl solution were prepared and plated on Potato Dextrose (PDA) agar (Oxoid, Hampshire, UK), and Sabouraund Dextrose (SD) agar (Difco, Detroid, USA) for fungal isolation and Man Rogosa Sharpe (MRS) agar (Oxoid), Violet Red Bile (VRB) agar (Oxoid), Baird–Paker agar (Difco) and Nutrient (NA) agar (Acumedia, Baltimore, MD, USA) for bacterial isolation. All plates were incubated at 30 8C for 3–5 days. After the incubation period, sub-culturing on the same media used for isolation purified the grown bacterial and fungal colonies. In this study, a total of 121 bacterial strains and 25 fungi isolates were isolated and stored for further studies. Bacterial strains were maintained for long-term storage in nutrient broth with 15% glycerol at K80 8C. Fungi isolates were kept in PDA slants at 4 8C in a refrigerator.

An experimental model of a drip irrigation system was designed on a workbench at the Laboratory of Irrigation in the Department of Agricultural Structure and Irrigation at Atatu¨rk University. A hydraulic structure was formed with two 12-m-long polyethylene drip irrigation pipes (: 16 mm) (Go¨ktepew, Izmir, Turkey), one of which was for treatment and the other was a control lateral. Each lateral emitter spacing, operation pressure and discharge rate was 0.33 m, 0.4 atm and 2.3 L/h per emitter, respectively. The emitters (tortuous path) used in this study were the in-line type with double exits. Hydraulic properties of the emitters are summarized in Table 1. Table 1 Hydraulic properties of emitters Operation pressure (atm)

0.5 1.0 1.5 2.0 a b

Average emitter discharge rate, q (L/h) 2.57 3.94 4.81 5.62

Coefficient of (qZkhx) equation ka

xb

3.8441

0.5625

Correlation coefficient, r2

Manufacturer’s coefficient of variation

0.99

0.022

Coefficient characterizing dripper dimension. Dripper flow regime coefficient (flow exponent).

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Table 2 The physical and chemical properties of drinking water used

100

Physical properties

Concentrations

Chemical properties

Concentrations

Suspended solids (mg/L)

–

263.07

Color Smell and taste Temperature (8C) Organic matter (mg/L)

Clear Normal 14G1 0.60

Electrical conductivity (m[/cm) PH Ions (mg/L) Calcium Magnesium Ammonium Sodium Potassium Boron Carbonate Bicarbonate Chlorine Sulfate Nitrite Nitrate Manganese Iron Sulfur

Treatment Control

Change in average discharge rate (%)

80

7.86 32.06 7.29 0.002 6.90 5.38 0.005 – 80.00 20.00 36.63 0.02 25.92 0.13 0.30 –

60

40

20

0 0

2

4

2.5. Biological clogging and treatment of emitters in a model drip irrigation system

6

8

10

12

14

16

Time (day) Fig. 2. The change in average discharge rate in the stage of anti-clogging.

All of the fungi isolates and bacterial strains isolated from drip irrigation systems were grown on the same media used for isolation. A mixture of suspension prepared from bacterial strains (109 CFU/mL) and fungi isolates (104 spores/mL) with sterile water in a plastic container (2 L) was injected into the tank of the drip irrigation system three times at 7-day intervals. The irrigation system was operated 8 h daily for 30 days. The physical and chemical properties of the drinking water used are given in Table 2. All emitters were partially or totally

clogged due to microbial growth during the time of the experiment (Fig. 1). Then, 500 mL of a mixture of antagonistic bacterial suspension and sterile distilled water was applied to the treatment and control lateral, respectively. This application was repeated two times at 48 h intervals. The irrigation system was operated and the flow rate of each emitter was measured daily (Fig. 2).

3. Results and discussion 2.5

Average discharge rate (L/h)

2

1.5

1

0.5

0 0

10

20

30

Time (day) Fig. 1. Average discharge rate of the emitters in the stage of clogging.

A total of 25 fungi and 121 bacterial strains were isolated from water samples collected from drip irrigation systems in tomato greenhouses in the eastern Anatolia region of Turkey in the spring season of 2001. Biological clogging of emitters in a model drip irrigation system was experimentally caused by application of the microorganisms isolated in the study within two weeks (Fig. 2). The mechanism of biological clogging may be explained by growth of mycelium after injection of fungi spores into the tank without requiring a high level of organic matter in the water. Colonization of fungal mycelium around the emitters of the drip irrigation system may provide substrate for bacterial strains to grow and produce extracellular polymeric substances (EPS). Development of biomass (a mixture of microbial growth including fungi and bacteria with EPS) on the emitters resulted in biological clogging of the emitters. The in-vitro test results of the three antagonistic bacterial strains (Bacillus spp ERZ, OSU-142 and Burkholdria spp OSU-7) selected and tested against all of the microbial

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organisms isolated confirmed the data reported in previous studies (Kotan et al., 1999; Es¸itken et al., 2002; Kotan and S¸ahin, 2002) The results showed that Bacillus strains (OSU-142, ERZ) inhibited all of the fungi isolates, but only 18 and 42% of the bacterial strains, respectively. However, Burkholdria OSU-7 inhibited the development of all of the fungi and bacterial strains tested. Two applications of 500 mL of a mixed antagonistic bacterial suspension at a concentration of 109 CFU/mL into one lateral of the pilot drip irrigation system showed that all emitters clogged due to microbial growth were cleaned and the discharge rate reached a maximum within 2 weeks after treatment. However, there was no reduction in the emitters of the control lateral treated with sterile water. This finding confirmed the in-vitro test results suggesting that the antagonistic bacterial strains tested in this study have the potential to be used not only for management of plant diseases (Kotan et al., 1999; Es¸itken et al., 2002; Kotan and S¸ahin, 2002), but also as anti-clogging agents for treatment of emitters in drip irrigation systems. This is the first study that demonstrated that antagonistic microorganisms can be utilized for treatment of clogging in drip irrigation systems.

4. Conclusion The results of the present study suggested that: (1) Bacillus spp ERZ, OSU-142 and Burkholdria spp OSU-7 are the antagonistic bacterial strains which can be used as anti-clogging agents for treatment of emitters in drip irrigation systems used in agriculture and/or domestic landscapes; (2) the use of these antagonistic bacterial strains in drip irrigation systems may reduce or completely eliminate the need for repetitive chemical applications to treat emitter clogging; (3) these strains may have the potential to be used not only for cleaning of biologically clogged emitters, but also for biological control of pathogenic microorganisms that cause diseases in plants watered with drip irrigation systems.

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