Fate of Soil-Applied Olive Mill Wastewater and Potential Phytotoxicity Assessed by Two Bioassay Methods (original) (raw)
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Plant and Soil, 2014
Background and aims Olive mill wastewater (OMW) generated in Mediterranean countries is partly disposed of on soil. Its underlying fate mechanisms and influences on plant growth are still largely unknown. Our goal was to understand OMW organic matter (OMW-OM) degradation in soil and its phytotoxic effects. We hypothesized that OMW phytotoxicity decreased with degradation of its phenolic components. Methods In a 60 day incubation study, we monitored soil respiration, extractable total phenolic content (TPC) and carbon isotope ratio (δ 13 C) of OMW treated Israeli soil. The soil was extracted using accelerated solvent extraction (ASE) and its extracts were exemplarily analyzed for four phenolic substances by LC/MS. Phytotoxicity of soil and soil extracts were tested using a Lepidium sativum seed germination bioassay. Results Soil respiration was 2.5 times higher for OMW treated soil with two respiration maxima and indicated a degradation of up to 27 % of the added OMW-OM. Four phases of OMW-OM degradation were identified: (i) degradation of easily degradable OMW-OM and transformation of phenolic compounds, (ii) intermediate suppression of phytotoxicity, (iii) degradation of phytotoxic phenolic compounds and (iv) significant physical immobilization of phytotoxic compounds. Conclusion Environmental conditions during and after OMW disposal on soil ought to favor fast degradation of OMW-OM, minimizing their physical immobilization and phytotoxic effects.
Chemosphere, 2007
Extremely high organic load and the toxic nature of olive mill wastewater (OMW) prevent their direct discharge into domestic wastewater treatment systems. In addition to the various treatment schemes designed for such wastewater, controlled land spreading of untreated OMW has been suggested as an alternative mean of disposal. A field study was conducted between October 2004 and September 2005 to assess possible effects of OMW on soil microbial activity and potential phytotoxicity. The experiment was carried out in an organic orchard located on a Vertisol-type soil (Jezre’el Valley, Israel) and included two application levels of OMW (36 and 72 m3 ha−1). Total microbial counts, and to less extent the hydrolytic activity and soil respiration were increased following the high OMW application level. A bench-scale lab experiment showed that the rate of OMW mineralization was mainly dependent on the general status of soil activity and was not related to previous acclimatization of the soil microflora to OMW. Soil phytotoxicity (% germination and root elongation) was assessed in soil extracts of samples collected before and after each OMW application, using germinating cress (Lepidium sativum L.) seeds. We found direct short-term effect of OMW application on soil phytotoxicity. However, the soil was partly or completely recovered between successive applications. No further phytotoxicity was observed in treated soils as compared with control soil, 3 months after OMW application. Such short-term phytotoxicity was not in correlation with measured EC and total polyphenols in the soil extracts. Overall, the results of this study further support a safe controlled OMW spreading on lands that are not associated with sensitive aquifers.
Olive mill wastewater (OMW) is the main residual product of olive processing and its disposal can represent a relevant environmental issue in Mediterranean countries, where olive oil production is large and concentrated in a short-lasting period. OMW is characterised by high pollutant load, salinity and phytotoxic levels of polyphenols, but also by a high amount of organic compounds and plant mineral nutrients. Therefore, OMW field spreading may represent a low cost contribution to crop fertilisation and soil amendment. Here, we assessed the short-and long-term effects of long-lasting repeated OMW applications on soil chemical and biochemical properties and arbuscular mycorrhizal fungi (AMF). In addition the influence of two OMW management strategies, characterised by different seasonality of spreading (autumn and spring times) was evaluated. Soil was amended by 0 and 80 m 3 ha À1 of OMW. Principal coordinate analyses (PCO) together with PERMANOVAs showed that long-lasting repeated OMW spreading: (i) affected the main soil chemical and biochemical parameters in the short-term, whereas did not determine long-term residual effects irrespective of the application times; (ii) decreased AM fungal root colonisation both after autumn and spring OMW applications; (iii) improved arbuscule occurrence in the short-and long-term for both disposal times. Therefore, at least regarding the monitored parameters, we can argue that OMW may be utilised as organic amendment in agriculture under controlled conditions given the short-term negative effects on soil quality, which can be considered negligible after a suitable waiting period.
Application of Ecotoxicological Tests in a Preliminary Evaluation of Soils Treated on Bioreactor
J. Braz. Soc. Ecotoxicol., 2007
Bioremediation processes are being applied nowadays for treatment of contaminated soils by petroleum products. However, only chemical analyses are used for efficiency verification, without taking into account a biological indicator. The aim of this work was the application of two ecotoxicological tests for the evaluation of a soil contaminated by crude oil, after treatment on a bioreactor, in different conditions. Sample A was treated with biostimulation (pH, nutrients and moisture control), while samples B and C, besides biostimulation was applied bulking material (sawdust; 10% w/w) also. The ecotoxicological tests chosen were luminescent bacteria Vibrio fischeri (ISO 11348-3:1998) and an avoidance behavior test with Eisenia fetida earthworms (still in a draft form). This test consists in the exposition of the organisms to contaminated soil and control soil samples, simultaneously, to evaluate the percentage of organisms that goes from the center of the recipient to the control sample sector. The results of avoidance behavior tests of samples A, B and C were, respectively, 52%, 29% and 50%. Those results indicate no toxicity, once the criteria for a sample be considered toxic is that more than 80% of the total exposed organisms are in the control soil at the end of the test. However, the test with Vibrio fischeri indicated toxicity for sample B (CE 50 13.8%), probably because of the recent contamination. Those results indicate that, although the importance of ecotoxicological tests inclusion for the complementation of bioremediation processes evaluation, at least two tests, using different organisms must be performed for a better consideration.
Application of bioassays and soil column test for toxicity evaluation of selected pesticides
WIT Transactions on Ecology and the Environment, 2008
The toxic effects of an organophosphate nematicide (Fosthiazate) and a benzenoid fungicide (Metalaxyl-M) have been evaluated by the use of the fresh water algae P. subcapitata. The effects of copper (Cu +2), an ingredient of many fungicidal mixtures, have also been assessed on the same organism, as well as the interactive effects of binary mixtures of the three aforementioned agrochemicals. Finally, leachates containing fosthiazate in two different concentrations have been tested on the bioluminescent bacterium Vibrio fischeri. The interactive effects of the binary mixtures were additive in most cases, while fosthiazate leachates exhibited low, dose-related toxicities.
Ecotoxicology, 2012
The olive oil mill wastewater (OMW) is a problematic and polluting effluent which may degrade the soil and water quality, with critical negative impacts on ecosystems functions and services provided. The main purpose of this review paper is presenting the state of the art of OMW treatments focusing on their efficiency to reduce OMW toxicity, and emphasizing the role of ecotoxicological tests on the evaluation of such efficiency before the up-scale of treatment methodologies being considered. In the majority of research works, the reduction of OMW toxicity is related to the degradation of phenolic compounds (considered as the main responsible for the toxic effects of OMW on seed germination, on bacteria, and on different species of soil and aquatic invertebrates) or the decrease of chemical oxygen demand content, which is not scientifically sound. Batteries of ecotoxicological tests are not applied before and after OMW treatments as they should be, thus leading to knowledge gaps in terms of accurate and real assessment of OMW toxicity. Although the toxicity of OMW is usually high, the evaluation of effects on sub-lethal endpoints, on individual and multispecies test systems, are currently lacking, and the real impacts yielded by its dilution, in freshwater trophic chains of receiving systems can not be assessed. As far as the terrestrial compartment is considered, ecotoxicological data available include tests only with plants and the evaluation of soil microbial parameters, reflecting concerns with the impacts on crops when using OMW for irrigation purposes. The evaluation of its ecotoxicity to other edaphic species were not performed giving rise to a completely lack of knowledge about the consequences of such practice on other soil functions. OMW production is a great environmental problem in Mediterranean countries; hence, engineers, chemists and ecotoxicologists should face this problem together to find an ecologically friend solution.
Concentrations of dissolved organic carbon (DOC) and total phenols (TP), and the phytotoxicity to cress (Lepidium sativum L.) were determined for three molecular-sized fractions of olive mill wastewater (OMW), <1000, 1000-5000, and >5000 Da, before and after incubation with Pleurotus ostreatus. The <1000-Da fraction contained 82% of the total DOC and 48% of the TP, and was the most phytotoxic. Ethyl acetate separation of aqueous and solvent fractions showed that the aqueous fraction contained 93% of the total DOC, 83% of the TP, and was most phytotoxic, indicating low importance of monomeric phenols. Incubation of whole OMW and of the separate size fractions with P. ostreatus mycelia reduced TP by factors of 4.3-5.3, but exerted diverse impact on phytotoxicity; overall, P. ostreatus efficacy in organic load removal and OMW detoxification was limited. Additional size fractionation of the incubated fractions revealed that most residual phytotoxicity was associated with low-molecular weight (MW) compounds originated from the <1000 Da fraction and not with low-MW byproducts from the degradation of higher-MW fractions and that polymerized metabolites were nonphytotoxic. Total phenols should not be used as sole indicators of the successful remediation of OMW.
Ecotoxicology and Environmental Safety, 2008
Hazard assessments based on two measures of toxicity were conducted for the untreated olive mill wastewaters (U), untreated olive mill wastewaters organic extract (UOE), treated olive mill wastewaters (T), treated olive mill wastewaters organic extract (TOE) and extracts of soils ferti-irrigated with untreated (SU) and with treated olive mill wastewaters (ST). The measures of toxicity were achieved by the determination of the bioluminescence inhibition percent (I B %) of Vibrio fischeri and by the growth inhibition (GI) of Bacillus megaterium, Pseudomonas fluorescens and Escherichia coli. A bioluminescence inhibition of V. fischeri of 100%, 100%, 65%, 47%, 46% and 30% were obtained with U, UOE, T, TOE, SU and ST respectively. Indeed, even diluted 24 times, a significant bioluminescence inhibition of 96% was obtained by U. However, only 30% bioluminescence inhibition was obtained by 24 times diluted T. Whereas, 24 times diluted, SU and ST did not show a bioluminescence inhibition (3% and 1%, respectively). The GI of B. megaterium, P. fluorescens and E. coli were, respectively, 93%, 72% and 100% by U; 100%, 80% and 100% by UOE; 70%, 60% and 89% by T; 63%, 54% and 68% by TOE; 39%, 27% and 43% by SU and 23%, 0% and 34% by ST. The incubation of U or T in the soil during four months reduced their toxicity by 54% and 35%, respectively. As it was expected, the most resistant bacterium to OMW toxicity is P. fluorescens then B. megaterium and E. coli. V. fischeri remained the most sensitive strain to the toxicity of this sewage what proves again its utilisation as standard of measure of the toxicity. r