Unwanted metals and hydrophobic contaminants in bioreactor effluents are associated with the presence of humic substances

Biological treatment of landfill leachate is challenging due to the presence of complex compounds. Here, we treated an old landfill leachate using a membrane bioreactor under the following conditions: 24 h for hydraulic retention, 65 days of sludge retention and an average organic load rate of 1.71 ± 0.16 g/L/day. We observed a high removal of ammonia, phosphorous and some metals. However, removal of organic carbon was incomplete. Despite a major removal of suspended solids, hydrophobic and volatile hydrophilic compounds, high concentration of fulvic acid and hydrophilic contaminants was found in the effluent. Overally, we demonstrate that the presence of humic substances in the effluent is associated with the detection of arsenic, copper and chromium and di(2-ethylhexyl) phthalate.     

No evidence for effect of soil compaction on the degradation and impact of isoproturon

Soil is damaged by several threats and, among them, chemical contamination by pesticides and compaction. However, the effect of compaction on the fate of pesticides in soil, and the impact of pesticides on soil biological functioning are unknown. Therefore, we studied the effect of soil compaction on the degradation of the herbicide isoproturon, and the impact of this herbicide on an enzyme activity (β-glucosidase) involved in the C soil cycle. Undisturbed soil samples were prepared at different bulk densities, treated with isoproturon then incubated at 18°C in darkness for 63 days. The results showed that soil compaction did not modify significantly the degradation of isoproturon, neither the formation rates nor the nature of its metabolites. Moreover, compaction did not modify the impact of isoproturon on β-glucosidase activity. To our knowledge, these are the first results concerning the interactions between soil compaction and the degradation and impact of a pesticide.     

Can green trade save the environment? Introducing the Green (Trade) Openness Index

Environmental Science and Pollution Research - Environmental degradation is one of the main drivers of climate change. One of the most broadly accepted tools to minimize environmental degradation...     

Roadmap for recycling of germanium from various resources: reviews on recent developments and feasibility views

Environmental Science and Pollution Research - Germanium as a strategic metalloid is widely used in high-tech devices. The most crucial germanium resources are rare and limited to zinc minerals,...     

Inspecting the influence of renewable energy and R&D in defending environmental quality: evidence for California

Environmental Science and Pollution Research - The United Nations’s Sustainable Development Goals (SDGs) is international cooperation that aims to climate change mitigation, and encourage the...     

Tetracycline removal enhancement with Fe-saturated nanoporous montmorillonite in a tripartite adsorption/desorption/photo-Fenton degradation process

The adsorption and photo-Fenton degradation of tetracycline (TC) over Fe-saturated nanoporous montmorillonite was analyzed. The synthesized samples were characterized using XRD, FTIR, SEM, and XRF analysis, and the adsorption and desorption of TC onto these samples, as well as the antimicrobial activity of TC during these processes, were analyzed at different pH. Initially, a set of adsorption/desorption experiments was conducted, and surprisingly, up to 50% of TC adsorbed was released from Mt structure. Moreover, the desorbed TC had strong antibacterial activity. Then, an acid treatment (for the creation of nanoporous layers) and Fe saturation of the montmorillonite were applied to improve its adsorption and photocatalytic degradation properties over TC. Surprisingly, the desorption of TC from modified montmorillonite was still high up to 40% of adsorbed TC. However, simultaneous adsorption and photodegradation of TC were detected and almost no antimicrobial activity was detected after 180 min of visible light irradiation, which could be due to the photo-Fenton degradation of TC on the modified montmorillonite surface. In the porous structures of modified montmorillonite high, ˙OH radicals were created in the photo-Fenton reaction and were measured using the Coumarin technique. The ˙OH radicals help the degradation of TC as proposed in an oxidation process. Surprisingly, more than 90% of antimicrobial activity of the TC decreased under visible light (after 180 min) when desorbed from nanoporous Fe-saturated montmorillonite compared to natural montmorillonite. To the best of our knowledge, this is the first time that such a high TC desorption rate from an adsorbent with the least residual antimicrobial activity is reported which makes nanoporous Fe-saturated montmorillonite a perfect separation substance of TC from the environment.

     

Adaptation of maize to climate change impacts in Iran

Adaptation is a key factor for reducing the future vulnerability of climate change impacts on crop production. The objectives of this study were to simulate the climate change effects on growth and grain yield of maize (Zea mays L.) and to evaluate the possibilities of employing various cultivar of maize in three classes (long, medium and short maturity) as an adaptation option for mitigating the climate change impacts on maize production in Khorasan Razavi province of Iran. For this purpose, we employed two types of General Circulation Models (GCMs) and three scenarios (A1B, A2 and B1). Daily climatic parameters as one stochastic growing season for each projection period were generated by Long Ashton Research Station-Weather Generator (LARS?WG). Also, crop growth under projected climate conditions was simulated based on the Cropping System Model (CSM)-CERES-Maize. LARS-WG had appropriate prediction for climatic parameters. The predicted results showed that the day to anthesis (DTA) and anthesis period (AP) of various cultivars of maize were shortened in response to climate change impacts in all scenarios and GCMs models; ranging between 0.5 % to 17.5 % for DTA and 5 % to 33 % for AP. The simulated grain yields of different cultivars was gradually decreased across all the scenarios by 6.4 % to 42.15 % during the future 100 years compared to the present climate conditions. The short and medium season cultivars were faced with the lowest and highest reduction of the traits, respectively. It means that for the short maturing cultivars, the impacts of high temperature stress could be much less compared with medium and long maturity cultivars. Based on our findings, it can be concluded that cultivation of early maturing cultivars of maize can be considered as the effective approach to mitigate the adverse effects of climate.     

Modified dehydrogenase enzyme assay for evaluation of the influence of Hg,Cd, and Zn on the bacterial community structure of a wastewater treatment plant

In this study, a traditional assay was modified to evaluate the effect of Hg, Cd, and Zn on the bacterial community of a sequencing batch reactor and activated sludge plants and heavy metal-resistant bacterial species were determined. After the isolation of metal-resistant bacteria, their 16S rRNA gene fragments were sequenced. The BLAST program was used to compare the resulting 16S rRNA sequences with those in GenBank database to identify the isolated bacterial species. Hg was found to be the most toxic metal for both bacterial communities investigated. Sequence batch reactor bacteria were comparatively more resistant to Hg, Cd, and Zn than those from activated sludge. The resistant strains were close to the members of genus Pseudomonas, Kocuria, Stenotrophomonas, Enterococcus, and Staphylococcus. The modified dehydrogenase enzyme assay seems to be simple, robust, and competent for evaluation of the impact of metals on bacterial activity. Sequencing batch reactor systems should be preferred over activated sludge when wastewaters containing hazardous metals are to be treated.     

Dose-response modeling for developmental neurotoxicity data

The fact that maternal exposures to some chemicals during pregnancy can adversely affect the structure and function of the nervous system in the offspring is well established. Government agencies have for a long time been concerned with regulation of developmental neurotoxicants and safe perinatal exposures. However, despite this concern, current guidelines provide only broad and nonspecific recommendations and lack clear directions for a model based approach to risk estimation. In this paper we propose a dose-response model for the nonquantal data obtained from developmental neurotoxicological experiments. To account for the critical issue of the correlation among responses from pups in the same litter, the so called intralitter correlation, a hierarchical distributional structure is used to derive the underlying unconditional distribution of responses. The maximum likelihood method is used to estimate model parameters and the covariance matrix of the estimates is derived. An example is used to illustrate the results.     

Mass transfer and bioremediation of aromatics from NAPL in a baffled roller bioreactor

A non-aqueous phase liquid (NAPL) containing dissolved naphthalene or phenol was used to simulate water insoluble contaminants which are produced during the processing of oil sands. Mass transfer and biodegradation of organic contaminants in the aqueous phase were studied in a baffled roller bioreactor. Mass transfer of both naphthalene and phenol from NAPL into the aqueous phase was completed in less than 60 min, by which time naphthalene reached its saturation concentration in the aqueous phase and phenol was completely transferred into the aqueous phase. Pseudomonas putida (ATCC 17484) was subsequently used in biodegradation experiments in the baffled bioreactor containing the model NAPL contaminant. The optimum loading of NAPL for biodegradation of naphthalene at 500 mg/L was found to be 40%. High biodegradation rates (136.4 mg/L h for naphthalene and 13.2 mg/L h for phenol based on the working volume of the bioreactor) were achieved. In the case of simultaneous biodegradation of naphthalene and phenol, the highest total biodegradation rate of 102.6 mg/L h was achieved.