Agrochimica, Vol. LVI - N. 4-5
July-October 2012
Efficiency of different remediation technologies for fenitrothion and dimethoate removal in the aquatic system A.S. Derbalah*, A.A. Ismail Department of Pesticides Chemistry, Faculty of Agriculture, Kafr El-Sheikh University, Egypt
Received July 26, 2012 – Received in revised form October 24, 2012 – Accepted October 7, 2012
Keywords: pesticides, pollution, remediation, toxicity, water.
Introduction. – Agricultural pesticides significantly improve crop yields, and pesticides protect against pests. On the other hand, pesticides have become universal contaminants found in all segments of the environment and create many hazards to the environment and human health. Pesticides contamination of fresh water has emerged as an important environmental problem in the last few decades and is causing concern with respect to long-term and low-dose effects on public health as well as non-target species (Sudo et al., 2002).Wide spread use and disposal of organophosphorus compounds that have been used as alternative to organochlorine compounds for pest control (Mueller and Schwack, 2001) resulted in the release of their residue into natural water, thus inducing an environmental problem (Lasram et al., 2009). Dimethoate (O,O-dimethyl-S-methylcarbamoyl methylphosphorothioate) is a systemic and contact broad-spectrum insecticide and acaricide used against numerous crop pests as well as to control houseflies. It belongs to the organophosphate family and, as most of these pesticides, is moderately toxic and readily absorbed through the skin and lungs acting as a cholinesterase inhibitor, an enzyme essential for normal nerve impulse transmission. It is enzymatically converted in the intestine wall and liver enabling desulfuration to its oxon-derivative omethoate (O,Odimethyl-S-methylcarbamoyl methylthiophosphate) causing enhanced neurotoxicity (Buratti and Testai, 2007). Fenitrothion (O,O-dimethyl O-3-methyl-4-nitrophenyl phosphorothioate) is an organophosphorus insecticide that has been widely used throughout the world because of its broad spectrum activity. After being applied to the environment, fenitrothion is transformed into various *
Corresponding author:
[email protected]
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compounds by biological and chemical activities as well as photolysis, and there is much literature available on the transformed products (TPs) of fenitrothion. However, the existence of unidentified TPs has been suggested (Matsushita et al., 2003). Due to the great environmental and human risk of pesticide residues in water resources, advanced methods are in demand for effective treatment of pesticides-polluted water to achieve complete mineralization of target pesticides and to avoid the formation of toxic end products (Derbalah, 2009). Advanced oxidation processes (AOPs), which are constituted by the combination of several oxidants such as Fenton reagent and zinc oxide combined with hydrogen peroxide, are characterized by the generation of very reactive and oxidizing free radicals in aqueous solution. Among them there are hydroxyl radicals which possess a great destruction power (Derbalah et al., 2004; Derbalah, 2009). An important feature of nanomaterials is that their surface properties can be very different from those shown by their macroscopic or bulk counterparts (Theng and Yuan, 2008). The application of nanoparticles as catalysts of the Fenton-like and photo-Fenton reactions has been described by several investigators (Valdés-Solís et al., 2007). In comparison with their micro size counterparts nanoparticles show a higher catalytic activity because of their large specific surface where catalytically active sites are exposed (Nurmi et al., 2005). The advantage of using nanoparticles as catalysts for Fenton-like reactions would more than offset the disadvantage (associated with the use of iron (III) catalysts) of requiring ultraviolet radiation to accelerate the reaction. Bioremediation of hazardous wastes is a relatively new technology that has undergone intense investigation in recent decades. This process is focused on destroying or immobilizing toxic waste materials (Shannon and Unterman, 1993). Bioremediation is an option that offers the possibility to destroy or render harmless various contaminants using natural biological activity. As such it uses relatively low-cost and low-technology techniques, which generally have a high public acceptance and can often be carried out on site (Vidali, 2001). However, after remediation of pesticide residues in water, toxicity assessment is needed to directly assess the potential hazard of both original pollutants and its metabolites (Derbalah, 2009). The use of acetylcholinesterase (AChE) biosensor seems to be the most appropriate technique for unambiguous determination of toxicity of water samples and wastewater at different stages of organophosphorus and carbamates
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degradation processes. The main advantages of AChE bioassays result from their selective sensitivity to organophosphates toxic photoproducts and prompt response, which enables on line monitoring and control of photodegradation processes (Kralj et al., 2007). In this study the efficiency of AOPs with different nanomaterials and bioremediation with effective microorganisms (EMs) were evaluated to achieve total degradation of fenitrothion and dimethoate. The cholinesterase activity was measured to confirm the complete detoxification of fenitrothion and dimethoate contaminated water after remediation. Materials and methods. – Chemicals. – Fenitrothion and dimethoate with purity of 99.5% was obtained from Central laboratory for Pesticides, Agriculture Research Centre, Cairo, Egypt. Zinc oxide (99.99%) and zero valent iron (99.9%) nanoparticles and titanium dioxide (99.9%) were obtained from Egypt Nanotech Company Limited, Cairo, Egypt. Titanium dioxide was obtained from Egypt Nanotech Company Limited, Cairo, Egypt. Photochemical remediation. – The scope of the experiments included the following treatments: nano photo-Fenton reagent [Fe0(nano)/H2O2/UV], nano photo zinc oxide combined with hydrogen peroxide [ZnO(nano)/H2O2/UV], photo-Fenton reagent (Fe2+/ H2O2/UV), photo zinc oxide combined with hydrogen peroxide (ZnO/H2O2/UV), titanium dioxide combined with hydrogen peroxide (TiO2/H2O2/UV), and ultraviolet alone (UV). For photo-Fenton reagent, a UV mercury lamp model VL-4.LC (80 W) with wavelength range of 254-365 nm was employed for the irradiation of fenitrothion or dimethoate in water solution, separately. Ferrous sulphate and zero valent iron nanoparticles were used as a source of iron catalyst. The solution was prepared by addition of the desired amount of fenitrothion or dimethoate (1 mg L-1) to distilled water and careful agitation. Then, freshly prepared ferrous sulphate, zero valent iron nanoparticles at concentration of 50 mg L-1 as Fe2+ or zero valent iron was added, followed by the addition of H2O2 at concentration of 0.05%. The solution was completed with water up to 1000 mL. The initial pH of the solution was adjusted to 2.8 with 1 M HCl in all experiments (Derbalah et al., 2004; Kallel et al., 2009). The solution was transferred from the standard flask to a quartz cell and exposed to the irradiation of the UV lamp under constant temperature of 25°C with stirring (the distance between the lamp and the pesticides solution was 15 cm). The solutions from the irradiated samples were removed at regular intervals (10, 20, 30, 60, 120, 240 and 300 min) for HPLC analysis. For ZnO and TiO2 catalysts, fenitrothion and dimethoate at concentration level of 1 mg L-1 with appropriate amount of ZnO and TiO2 or ZnO nanoparticles (300 mg L-1) were carefully shaken before illumination, followed by the addition of H2O2 at concentration level of 0.05%. Then the pH was adjusted to 7, the optimum pH for ZnO and TiO2 catalysts (Derbalah, 2009). The suspension was left for 30 min in the dark prior to illumination to achieve the maximum adsorption of the pesticide onto semiconductor surface (Derbalah, 2009). The solutions from the irradiated samples were removed at regular intervals (10, 20, 30, 60, 120, 240 and 300 min) for HPLC analysis. An experiment using UV alone without catalysts was carried out to evaluate the photolysis of the insecticides. All photochemical experiments were repeated three times for accurate data.
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Bioremediation technique. – Effective microorganisms (EMs) formulation used for bioremediation of fenitrothion and dimethoate was obtained from the Egyptian Ministry of Agriculture, Cairo, Egypt. This formulation contains 60 species of beneficial microorganisms grown in special media and produced in Egypt under the supervision of the Japanese EMRO Scientific Organization. The enrichment and propagation were carried out in sterilized 250 mL Erlenmeyer flask using a mineral salt medium (MSM) (AbdelMegeed, 2004) and 5 mL L-1 of EMs liquid concentrate. Then the culture was prepared in sterilized 250 mL flasks containing 190 mL MSM, 10 mL EMs supplemented with fenitrothion and dimethoate at concentration level of 1 mg L-1, separately. The cultures were incubated at 30°C, pH 7 and 150 rpm as optimum conditions for the growth of the EMs (Derbalah et al., 2008). Samples were collected at 0, 1, 2, 3, 4 and 5 weeks for monitoring the degradation of the insecticides. Control flasks of equal volume of MSM medium and the tested insecticides without the EMs were run in parallel at all intervals to assess abiotic loss of the insecticides. The collected water samples of the insecticides were filtered using syringe filter (0.2 µm) (Derbalah et al., 2008) before HPLC analysis. This experiment was repeated three times for accurate data. HPLC analysis. – The irradiated samples were analysed directly by HPLC (1100 series, Agilent Technologies, Palo Alto, CA, USA). The HPLC column (i.d. 4.6 mm; length 250 mm) was filled with Wakosil-II 5 C18-100 (Wako). A mixture of acetonitrile and distilled water was used as mobile phase for fenitrothion (60:40) and for dimethoate (40:60) under the isocratic elution mode. The flow rate was maintained at 1 mL min-1 and the UV detector was employed at wavelength of 220 nm for fenitrothion (Kiso et al., 1996) and 210 nm for dimethoate (Evgenidou et al., 2006). Data Calculation. – First order rate constants were derived from plots by linear regression analysis for each experiment. The half-life (t1/2) was estimated from equation (1) (Monkiedje and Spiteller, 2005).
t1/2 =
0.693 K
(1)
Toxicity test. – To confirm the complete detoxification of fenitrothion and dimethoate in treated water, a toxicity test was conducted on rats. Fenitrothion and dimethoatecontaminated waters after treatment with Fe2+/H2O2/UV, Fe0(nano)/H2O2/UV, ZnO/ H2O2/UV, ZnO(nano)/H2O2/UV, TiO2/H2O2/UV, UV alone and EMs were orally administrated to the rats. The test was carried out to measure the effect of the possible remaining fenitrothion or dimethoate (parent or metabolites) in water samples after remediation on rats with respect to AChE activity in treated rats relative to control. Adult rats (Sprague Dawley) of 100-120 g of weight obtained from the faculty of Veterinary Medicine of Kafr-El-Shiekh University were used. Rats were housed in polypropylene cages under standard conditions with free access to drinking water and food. The animals were randomly divided into eight groups each comprising three animals, and the treated samples containing fenitrothion and dimethoate separately were given to rats as oral administration. Control group rats was fed with normal diet and given oral dose containing no fenitrothion and dimethoate. After 21 days, the rats were sacrificed under anaesthesia and blood sample was taken by cardiac puncture in vials containing heparin. Plasma was separated and centrifuged at 4500 rpm for 15 min. The supernatant was used to determine AChE activity according to the method described by Ellman et al. (1961). To determine the specific activity of cholinesterase, total protein content was
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determined by the method described by Gornall et al. (1949). The specific activity (µmol AChE min-1 mg-1 protein) was calculated according to Ellman et al. (1961) by using equation (2):
activity = ∆ O.D. sample – ∆ O.D. blank /0.0124 × PC x Sv
(2)
where: O.D. = optical density PC = protein concentration (mg mL-1) Sv = sample volume (100 µL) Statistical analysis. – Enzyme activity data were statistically analysed using oneway analysis of variance. Least significant difference (LSD) was used to separate means using SAS program (Version 6.12, SAS Institute Inc., Cary, USA).
Results. – Degradation of fenitrothion and dimethoate by advanced oxidation processes. – The first parameter considered in this study was the losses of fenitrothion and dimethoate concentration with respect to the irradiation time compared to the rate and the complete degradation of the tested compounds. As shown in Figs. 1 and 2 as well as in Tables 1 and 2 the irradiation under Fe0(nano)/H2O2/UV system gave the highest degradation rate of fenitrothion and dimethoate followed by ZnO(nano)/H2O2/UV, TiO2/H2O2/UV, Fe2+/H2O2/UV, ZnO/H2O2/UV and UV light alone, respectively. A complete degradation of fenitrothion and dimethoate (100%) was achieved under Fe0(nano)/H2O2/UV followed by ZnO(nano)/H2O2/UV, TiO2/H2O2/UV, Fe2+/H2O2/UV and ZnO/H2O2/UV systems within 10, 20, 30, 60, 120, 240 and 300 min of irradiation time, respectively (Figs. 1 and 2). The complete degradation of the insecticides was not achieved under UV treatment. Biodegradation of fenitrothion and dimethoate using EMs. – The degradation ability of the EMs against fenitrothion and dimethoate is illustrated in both Fig. 3 and Table 3. The EMs showed high potential in the degradation of the insecticides with half-life values of 6.74 and 10.34 days for fenitrothion and dimethoate, respectively. A value of 98.7% of fenitrothion initial concentration (1 mg L-1) was degraded within five weeks, while 91.7% of dimethoate was degraded within the same time. On the contrary, the degradation percentage of fenitrothion and dimethoate was negligible at the end of incubation time in control samples (data not shown). This is an indication that the abiotic losses of fenitrothion and dimethoate are negligible. Toxicity assessment. – The complete detoxification of fenitrothion and dimethoate in water samples treated with Fe0(nano)/H2O2/UV,
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Fig. 1. – Degradation of fenitrothion at initial concentration of 1 mg L-1 in water under Fe0(nano)/H2O2/UV, ZnO(nano)/H2O2/UV, Fe2+/H2O2/UV, ZnO/H2O2/UV, TiO2/H2O2/UV and UV alone systems.
Fig. 2. – Degradation of dimethoate at initial concentration of 1 mg L-1 in water under Fe0(nano)/H2O2/UV, ZnO(nano)/H2O2/UV, Fe2+/H2O2/UV, ZnO/H2O2/UV, TiO2/H2O2/UV and UV alone systems.
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Table 1. – Half-life values (t½) and related correlation coefficient (R2) for fenitrothion in aqueous system under different advanced oxidation processes. Treatments UV only TiO2/H2O2/UV ZnO/H2O2/UV Fe2+/H2O2/UV ZnO(nano)/H2O2/UV Fe0(nano)/H2O2/UV *
R2
t½ (h)*
0.93 0.97 0.86 0.94 0.96 0.93
16.50 ± 1.7 0.49 ± 0.03 0.64 ± 0.05 0.52 ± 0.04 0.43 ± 0.04 0.39 ± 0.02
Values are means ± standard deviation (n = 3).
ZnO(nano)/H2O2/UV, Fe2+/H2O2/UV, TiO2/H2O2/UV, ZnO/H2O2/UV, UV alone and EMs was confirmed by measuring the effect of these treated samples on the activity of AChE relative to control in rats. The results showed that, there were no significant differences in cholinesterase activity in the rats treated with water samples after remediation compared to control treatment except for UV treatment only (Table 4). Discussion. – The degradation rate of fenitrothion and dimethoate was enhanced by irradiation by Fe0(nano)/H2O2/UV and ZnO(nano)/ H2O2/UV compared to the degradation under other photochemical remediation systems. This is due to the fact that the stabilized nanoparticles offered much greater surface area and reactivity which lead to higher generation rate of hydroxyl radicals in comparison with to the normal particles (He et al., 2007), and this subsequently induced faster degradation of the insecticides.
Table 2. – Half-life values (t½) and related correlation coefficient (R2) for dimethoate in aqueous system under different advanced oxidation processes. Treatments UV only TiO2/H2O2/UV ZnO/H2O2/UV Fe2+/H2O2/UV ZnO(nano)/H2O2/UV Fe0(nano)/H2O2/UV *
R2
t½ (h)*
0.92 0.95 0.83 0.94 0.92 0.96
14.44 ± 1.1 0.42 ± 0.03 0.74 ± 0.06 0.55 ± 0.04 0.40 ± 0.02 0.36 ± 0.03
Values are means ± standard deviation (n = 3).
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Fig. 3. – Biodegradation of fenitrothion and dimethoate at initial concentration of 1 mg L-1 in water by effective microorganisms (EMs).
The degradation rate of fenitrothion and dimethoate under Fe0(nano)/ H2O2/UV and Fe2+/H2O2/UV was higher than under ZnO(nano)/H2O2/ UV and ZnO/H2O2/UV systems. This may be due to the high generation rate of hydroxyl radicals under Fe2+/H2O2/UV (nano or normal) through many sources (eqs. 3-6) relative to ZnO/H2O2/UV (nano or normal) (eqs. 7-10) (Derbalah, 2009).
H2O2 + hν → 2 OH Fe3+ + H2O2 → Fe2+ + HO2˙+ H Fe2+ + H2O2 → Fe3+ + ˙OH + OH- Fe(OH)2+ + hν → Fe2+ + ˙OH ZnO + hυ→ ZnO (e–cb/h+vb) → e–cb + h+vb e–cb + h+vb → heat h+vb + OH–(or H2O)ads. → ˙OH (+ H+) e–cb + O2 → ˙O2–
(3) (4) (5) (6) (7) (8) (9) (10)
The degradation rates of fenitrothion and dimethoate under ZnO(nano)/H2O2/UV were higher than that under ZnO/H2O2/UV and this was due to the effect of particle size of nano zinc oxide. The effect
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Table 3. – Half-life values (t½) and related correlation coefficient (R2) for fenitrothion and dimethoate in aqueous system using effective microorganisms (EMs). Treatments
R2
t½ (day)*
Fenitrothion Dimethoate
0.96 0.95
6.74 ± 0.32 10.34 ± 0.52
*
Values are means ± standard deviation (n = 3).
of particle size on the photodegradation efficiency can be ascribed to two reasons. First, when the size of ZnO crystals decreases then the amount of the dispersion particles per volume in the solution will increase resulting in the enhancement of the photon absorbance. Second, the surface area of ZnO photocatalyst will increase as the size of ZnO crystals decreases, which promote the adsorption of more insecticide molecules on the surface (Wang et al., 2007). The degradation rates of fenitrothion and dimethoate under Fe0(nano)/ H2O2/UV were higher than that Fe2+/H2O2/UV, and this was mainly due to the effect of nano zero valent iron particle size in agreement with Valdés-Solís et al. (2007), who developed a new catalyst using nanosize particles with a high surface area that can accelerate the photo Fenton reagent. Therefore, zero valent iron and zinc oxide nanoparticles are potentially useful for remediation of fenitrothion and dimethoate contaminated water because they can reach or penetrate into zones that are inaccessible to micro size solid catalysts (Liu, 2006). Table 4. – Effect of different fenitrothion- and dimethoate-contaminated water treatments on the activity of cholinesterase in rat. Treatments Control (EMs) UV only TiO2/H2O2/UV ZnO/H2O2/UV Fe2+/H2O2/UV ZnO(nano)/H2O2/UV Fe0(nano)/H2O2/UV
Specific activity of cholinesterase Fenitrothion
Dimethoate
5.53 x 10-1± 0.05 a 4.83 x 10-1 ± 0.04 a 2.89 x 10-1 ± 0.02 b 4.98 x 10-1 ± 0.04 a 4.73 x 10-1 ± 0.03 a 4.95 x 10-1 ± 0.05 a 5.33 x 10-1 ± 0.05 a 5.40 x 10-1 ± 0.05 a
5.67 x 10-1 ± 0.033 a 5.05 x 10-1 ± 0.04 a 3.03 x 10-1 ± 0.02 b 5.33 x 10-1 ± 0.05 a 5.24 x 10-1 ± 0.05 a 5.13 x 10-1 ± 0.05 a 4.83 x 10-1 ± 0.05 a 5.43 x 10-1 ± 0.06 a
Values are means ± standard deviation (n = 3). Letters show the significance and non-significance between the means using Duncan’s multiple range test.
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The degradation of the insecticides under Fe0(nano)/H2O2/UV is due to the generation of hydroxyl radicals through a three-stage system (Ortiz de La Plata et al., 2012). The main reason for the three-stage reaction is the evolution of iron(II) in aqueous solution (eq. 11). Then, the initial Fe2+ would cause ˙OH radicals to be available for oxidation (eq. 5). When the optimum concentration of iron(II) is available the Fenton reaction reaches the highest level, pH of aqueous solution is generally less than 3, and the rate of the insecticides removal is at his maximum. The main reason for this fast reaction is that ferrous iron reacts very quickly with hydrogen peroxide to produce large amount of hydroxyl radicals. In the third stage of the reaction, generation of iron(II) continues even after H2O2 depletion (Ortiz de La Plata et al., 2012):
Fe0 + H2O2 → Fe2+ + 2 HO–
(11)
TiO2/H2O2/UV showed high ability for the degradation of the insecticides (Kouloumbos et al., 2003). This high degradation is due to the fact that from the semiconductor TiO2 in the presence of light the valence band holes (h+vb) and conduction band electrons (e-cb) are photogenerated (eq. 12). ˙OH radicals generated through water oxidation by photo-generated valence band holes according to eqs. 13, 14 and 15 are known to be the most oxidizing species. ˙OH radicals react rapidly and non-selectively with organic molecules leading to the production of numerous oxidation intermediates and final mineralization products. In the presence of air, other species might contribute to the oxidation of the organic molecules such as H2O2 or even superoxide radicals, which are produced by oxygen reduction through photo-generated conduction band electrons: TiO2 + hυ → e–cb + h+vb TiO2 (h+) + H2O ads. → TiO2 + ˙OH + H TiO2 (h+) + HO ads. → TiO2 + ˙OH TiO2 (h+) + RX ads. → TiO2 + RX+
(12) (13) (14) (15)
After 120 min of irradiation time, the degradation rates of the remaining fenitrothion and dimethoate were quite slower than the first 120 min under all photochemical remediation systems. This might be due to the low concentration of the remaining fenitrothion and dimethoate (lower than 5% of initial concentration) after 20 min of irradiation time which lead to high delivery rate of Fe2+/H2O2 and ZnO/H2O2 and corresponding
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higher concentrations of these reagents, and this subsequently increased their ability to compete with fenitrothion and dimethoate in reacting with hydroxyl radicals as hydroxyl radicals scavenger (eqs. 16 and 17) (Derbalah et al., 2004; Derbalah, 2009). Furthermore, chloride and carbonate ions naturally present in water react with hydroxyl radicals (Pare et al., 2008) as shown in equations 18 and 19: Fe2+ + ˙OH → Fe3+ + OH OH + H2O2 → HO2˙ + H2O Cl- + ˙OH → Cl˙ + OH- CO32- + ˙OH → CO3-˙ + OH-
(16) (17) (18) (19)
The degradation rates of fenitrothion and dimethoate were the lowest under UV alone compared to other systems due to the degradation induced by direct photolysis only, in agreement with the findings of Derbalah (2009). Concerning the bioremediation of fenitrothion and dimethoate, EMs showed high degradation ability against fenitrothion and dimethoate in drinking water. This might be due to the fact that the EMs is not one microorganism but a mixture of microorganisms (Higa, 1995) and has also been described as a multi-culture of coexisting anaerobic and aerobic beneficial microorganisms. Therefore, its degradation ability must be faster and effective than using one microorganism. The results revealed that fenitrothion and dimethoate might have been efficiently metabolized by detoxifying enzymes since the biodegradation of organophosphates involves activities of enzymes such as phosphatase, esterase, hydrolase and oxygenase. Enzymatic hydrolysis of twelve commonly used organophosphorus insecticides was found to be much faster than chemical hydrolysis (Mulbry and Karns, 1989). As a conclusion, EMs could be used in various kinds of aerobic and anaerobic systems for treating agricultural wastes which represent the first point for discharge of many chemicals into the environment. The effective and stable degradation capacity of this EMs technology in utilizing and degrading these compounds reflect their efficacy in biotechnological application for the bioremediation of such contaminated water. These results indicated that EMs are more stable in retaining their ability to completely degrade fenitrothion and dimethoate because these EMs live in symbiotic relationships and their influence on the environment are the sum of all activities of these microorganisms. Where the
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metabolites formed by one type of microorganism may be utilized by other group of organisms. Therefore, this study so far suggested that microorganisms endowed with this property of degradation of toxic pollutants are a boon to mankind. Future studies on the genes responsible for enhanced biodegradation will enable us to elucidate the exact degradation pathway involved in the microbial biodegradation. To evaluate the efficacy of different remediation techniques in removing fenitrothion and dimethoate from drinking water, toxicity assessment was carried out with respect to biochemical and histological tests. The results showed that the treated water samples either after chemical or bioremediation had no significant effect on the activity of AChE compared to control (Table 4). This implies that fenitrothion and dimethoate which spiked water samples before remediation were completely removed in all remediation techniques. Moreover, this means that the aqueous solution spiked with fenitrothion and dimethoate was completely detoxified to AChE non-inhibiting products when a bioassay was conducted with AChE as a sensitive target of fenitrothion and dimethoate (Kralj et al., 2007). Conclusions. – The photo-Fenton reagent and photo zinc oxide combined with hydrogen peroxide with nanoparticles as well as photo titanium dioxide combined with hydrogen peroxide showed much promise in the complete degradation and detoxification of fenitrothion and dimethoate in contaminated water, especially with nanoparticles. EMs formulation is promising as effective and safe bioremediation technique for fenitrothion and dimethoate removal in water. REFERENCES Abdel-Megeed, A.: Psychrophilic degradation of long chain alkanes. Dissertation Technische Universität Hamburg-Harburg, Germany (2004). Buratti, F.M. and Testai, E.: Evidences for CYP3A4 auto activation in the desulfuration of dimethoate by the human liver. Toxicology 241, 33-46 (2007). Derbalah, A.S.: Chemical remediation of carbofuran insecticide in aquatic system by advanced oxidation processes. J. Agric. Res. Kafr El-Sheikh Univ. 35, 308-327 (2009). Derbalah, A.S., Nakatani, N. and Sakugawa, H.: Photocatalytic removal of fenitrothion in pure and natural waters by photo-Fenton reaction. Chemosphere 57, 635-644 (2004). Derbalah, A.S., Massoud, A.H. and Belal, E.B.: Biodegrability of famoxadone by various microbial isolates in aquatic system. Land Contam. Reclam. 16, 13-23 (2008). Ellman, G.L., Courtney, K.D., Andres, V. and Featherstone, R.M.: A new and rapid colorimetric determination of acetyl cholinesterase activity. Biochem. Pharmacol. 7, 88-95 (1961). Evgenidou, E., Konstantinou, I., Fytianos, K. and Poulios, I.: Oxidation of two organophosphorus insecticides by the photo-assisted Fenton reaction. Water Res. 41, 2015-2027 (2006). Gornall, A.G., Bardawill, C.J. and David, M.M.: Determination of serum protein by means of the biuret reaction. J. Biol. Chem. 177, 751-766 (1949).
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Summary. – This study was carried out to evaluate the efficiencies of different remediation technologies (advanced oxidation processes and bioremediation) for removing fenitrorthion and dimethoate in water. Nano photo-Fenton reagent (Fe0(nano)/ H2O2/UV) was the most effective treatment for fenitrorthion and dimethoate removal in water, whereas UV alone was the least effective one. Bioremediation of fenitrorthion and dimethoate by effective microorganisms (EMs) removed approximately 100% of their initial concentration after 5 weeks of treatment. There was no remaining toxicity in fenitrorthion and dimethoate contaminated water after remediation on treated rats with respect to cholinesterase activity except for UV alone. Advanced oxidation processes, especially with nanomaterials, and bioremediation with EMs can be regarded as safe and effective remediation technologies for fenitrorthion and dimethoate in water.
