Qualitative analysis of activated sludge using FT-IR technique.

The ability to measure and control the composition of activated sludge is an important issue, aiming at evaluating the effectiveness of changes occurring in the sludge, what determines its usefulness to treat wastewater. In this research, diffuse reflectance infrared Fourier transform (FTIR-DRIFT) technique was used, which relies on measuring the reflectance of the powdered substance's surface layer and capturing spectra in range of infrared wave. First, spectra correlation table of the substances mostly occurring in wastewater was developed to assess the main components of the tested samples of activated sludge. The simplest compounds containing functional groups characteristic for particular chemical classes were chosen: peptides (peptone and albumin), fats (glycerin and fatty acids), carbohydrates (glucose and sucrose), nitrogen compounds (NaNO3 and NH4SO4), sulfur compounds (Na2SO4 and Na2S2O3), silicate, etc. The spectra of those substances were captured and characteristic absorption bands for respective bonds in the function groups were assigned. Second, samples of activated sludge from lab-scale membrane bioreactors (MBRs), which purifies petroleum wastewater, were taken. Samples were properly prepared (lyophilization and homogenization) and their spectra were captured. During spectra analysis, previously developed correlation table was used. In obtained spectra of activated sludge, absorption bonds characteristic for amides, peptides, carbohydrates, fats, and aliphatic was identified. The spectra profile of the sludge sample from MBR feed with petroleum wastewater was slightly different from the control MBR sample's spectra. Intensity of bands in the area characteristic for aliphatic compounds and phenols was clearly higher. This study proves the usefulness of FT-IR technique to observe changes in the chemical composition of activated sludge.

Dose-dependent effects of the herbicide mesotrione on soil cyanobacterial communities.

This study aimed to investigate the dose-response effects of an herbicide on soil photosynthetic microbial communities, particularly cyanobacteria, using a microcosm approach. Pure mesotrione (active ingredient), and Callisto (a commercial formulation of this triketone herbicide), were spread at different rates on soil microcosm surfaces. Soil Chlorophyll concentrations were quantified to assess the photosynthetic biomass, and the genetic structure and diversity of the cyanobacterial community were investigated by a group-specific polymerase chain reaction followed by denaturing gradient gel electrophoresis. Dose-dependent responses were evidenced for both functional and structural parameters. No effect was detected in soils treated with 1 × AR (1-fold recommended application rate) irrespective of the herbicide formulation. At 10 × AR (10-fold recommended application rate), only Callisto treatment induced significant decreases of photosynthetic biomass, whereas structural parameters were less affected. At the 100 × AR (100-fold recommended application rate), both pure mesotrione and Callisto had strong negative impacts on soil chlorophyll concentrations and cyanobacterial genetic structure and diversity. At both the 10 × AR and 100 × AR treatments, Callisto induced significant stronger effects than pure mesotrione. In addition, indicators of photosynthetic biomass, compared with structural parameters of cyanobacterial communities (within 14 days), responded (within 7 days) more quickly to herbicide stress. The results of this study underscore the relevance of soil photosynthetic microbial communities to develop indicators for herbicide risk assessment.

Photolysis of the herbicide sulcotrione: formation of a major photoproduct and its toxicity evaluation.

BACKGROUND: Sulcotrione is a selective herbicide marketed for use in maize since 1993, but its environmental fate is not yet fully elucidated. A major metabolite resulting from cleavage between the two ring moieties, leading to 2-chloro-4-mesylbenzoic acid (CMBA), has been identified; it presents a rather low toxicity. In photochemical studies this compound has also been claimed to be formed in high proportions. The present authors recently found that, under irradiation, sulcotrione mainly yields a cyclization product (CP). Thus, Sulcotrione photochemistry is still a matter of debate. The aim of the present work was to give an unequivocal answer to this issue. The potential toxicity of CP, CMBA and sulcotrione towards three organisms considered as representative of aquatic ecosystems was also evaluated. RESULTS: The main transformation product of sulcotrione is the cyclization product (CP), and CMBA is formed in smaller amounts. For the toxicological approach, the tested organisms were a bacterium, Vibrio fischeri (Bejerinck) Lehmann & Neumann, an alga, Pseudokirchneriella subcapitata (Korshikov) Hindak, and a protozoan, Tetrahymena pyriformis (Ehrenberg) Lwoff. Sulcotrione is more harmful towards the alga, but CP is more toxic to the bacterium and the protozoan. It must be noted that the measured toxicities are nonetheless rather low. CONCLUSION: On irradiation, sulcotrione mainly gives the photocyclization product, which presents a higher toxicity than sulcotrione and CMBA. This cyclization product should thus be considered in sulcotrione environmental risk assessment.

Phototransformation of pesticides on plant leaves: the case of sulcotrione.

Photochemistry is one of the main ways of pollutants degradation in the environment. There is an obvious lack of data concerning the photostability of agrochemicals on plant foliage. We report here the first photodegradation study of a triketonic herbicide (sulcotrione) used as a substitute of atrazine. To mimic surface Leaves, we used films made of carnauba grey wax or of cuticular wax extracted from maize Leaves. Under simulated solar light, sulcotrione was rapidly phototyzed. The phototysis was much faster on cuticular wax films than in aqueous phase. Moreover, the formulated sulcotrione (Mikado) disappeared even more quickly than the pure active ingredient. Sulcotrione mainly underwent an intramolecular cyclization. To validate these observations, sulcotrione and its main photoproduct were monitored after maize field treatment. The day after the treatment the main photoproduct was detected on the maize leaves and suLcotrione had already significantly disappeared. This experiment demonstrates that phototysis can be a relevant process in real conditions after field treatment.

R&D priorities in the field of sustainable remediation and purification of agro-industrial and municipal wastewater.

This article was presented as a position paper during the Environmental Biotechnology and Microbiology Conference in Bologna, Italy in April 2012. It indicates major and emerging environmental biotechnology research and development (R&D) priorities for EU members in the field of sustainable remediation and purification of agro-industrial and municipal wastewater. The identified priorities are: anaerobic/aerobic microbial treatment, combination of photochemical and biological treatment, phytoremediation and algae-based remediation, as well as innovative technologies currently investigated, such as enzyme-based treatment, bioelectrochemical treatment and recovery of nutrients and reuse of cleaned water. State of the art, research needs and prospective development in these domains are crucially discussed. As a result, goals of the future development of bioremediation and purification processes are defined and the way to achieve them is proposed.

Removal of petroleum pollutants and monitoring of bacterial community structure in a membrane bioreactor.

The long-term operational stability (159 d) in removal of organics and ammonia from synthetic wastewater was investigated. The experiment was carried out in two identical plug flow membrane bioreactors (MBR) (each with a submerged A4 Kubota membrane) operated under aerobic conditions. The vacuum distillate of a crude oil fraction in the emulsified state, which was used to model the petroleum pollutants, was added into the feed medium. The performance of biological treatment was evaluated by physicochemical analyses such as nitrogen forms, COD, and BOD. Additionally, monitoring of PAHs in the wastewaters was performed using HPLC-diode array detector. Moreover, the community structure of bacteria was analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis. The MBR treatment was very effective with reduction by more than 90% of COD and Total Organic Carbon. Nearly complete removal of petroleum originated non-polar micropollutants was observed. The influence of the highest dosage of petroleum pollutants (1000 µLL(-1)) on the bacterial community was noted.

Photodegradation product of sulcotrione and the physiological response of maize (Zea mays) and white mustard (Sinapis alba).

One of the strategies for decreasing the consumption of herbicides consists in improving their uptake and efficiency. It was suggested that the photodegradation of herbicides due to sunlight results in a greater demand of herbicides to be introduced into the environment in order to ensure the plant protection activity. Moreover, an ecotoxicological effect of the photoproducts needs to be clarified. The physiological response of Zea mays and Sinapis alba (weed) to sulcotrione and its main photoproduct, called chromone (xanthene-1,9-dione-3,4-dihydro-6-methylsulfonyl), was evaluated under controlled conditions in a growth chamber. The dose-response effects were determined on Z. mays and S. alba. Using the sulcotrione (doses ranging from 1 to 9mg per plant), the physiological parameters indicated a decrease of photosynthesis for the S. alba species while the Z. mays species were only slightly affected. On the contrary, the chromone had no herbicide activity on both species. The sulcotrione is known to block 4-hydroxyphenyl pyruvate dioxygenase (HPPD) enzyme. The differences between the parent herbicide and the photoproduct could be ascribed to drastic structural modifications. We have shown that the chromone probably do not block the HPPD active site.