Subsequent Biological Degradation Research Articles

Functional interplay between plastic polymers and microbes: a comprehensive review.

Escalated production of plastic, their worldwide distribution and persistent nature finally results into their environmental accumulation causing severe threats to the ecological environment and biotic health. Thus, development of suitable measurements for environmental remediation of plastic may be an urgent issue in this plastic age. Some recent reviews have categorized the microbial species able to degrade different plastic polymers and the different factors effecting bio-degradation of plastic are poorly understood. This review comprehensively discusses bio-degradation of traditional and biodegradable plastic polymers both in natural and biological environment (gut microbes and fungi) to understand different factors regulating their degradation, and also shows how degradation of plastic polymers under abiotic factors influence subsequent biological degradation. Different physicochemical modifications like - breaking large polymers into small fragments by pre-treatment, functional groups enrichment, identifying potent microbial species (consortia) and engineering microbial enzymes might be crucial for bio-degradations of plastic. Effects of micro/nanoplastic and other chemical intermediates, formed during the bio-degradation of plastic, on species composition, abundance, growth, metabolism and enzymatic systems of microbes involved in the bio-degradation of plastic should be determined in future research.

Treatment of real pharmaceutical wastewater using combined approach of Fenton applications and aerobic biological treatment

The pharmaceutical wastewater of different organic loads i.e. high (HSW) and low strength wastewater (LSW) were collected from the bulk pharmaceutical industry and subjected to different applications of Fenton’s treatment followed by subsequent biological treatment. For both the HSW and LSW, applications of Fenton such as, dark-Fenton (DF), solar driven photo-Fenton (PF) and electro-Fenton (EF) were utilized as pre-treatment technologies to improve the biodegradability and reduce the organic load of wastewater by combine oxidation and coagulation. The operational parameters like pH, hydrogen peroxide dosage and iron concentration were optimized in case of DF and PF processes, whereas in case of EF process, applied voltage and hydrogen peroxide dosage were optimized to make water biocompatible for subsequent biological degradation. The use of Fenton applications as a pre-treatment resulted in a significant enhancement in the BOD5/COD ratio validating the production of easily degradable metabolites or secondary products. Overall results indicated that among the utilized Fenton technologies, pre-treatment of pharmaceutical wastewater with PF lead to better COD and TOC removal efficiency with subsequent biological degradation when compared to DF and EF pre-treatment. Overall COD removal efficiency of the combined PF and biological treatment was around 84% for LSW and 82% for HSW. Conclusively, it can be established that combined Fenton applications as pretreatment technology and biological treatment is more effective approach in comparison to single stage oxidation either by Fenton or biological treatment. Cytotoxicity assessment revealed that complete detoxification of wastewaters were achieved indicating that hybrid treatment technology of Fenton’s and biological treatment did not exhibited any toxicity against the selected microbes.

Inferring changes in soil organic matter in post-wildfire soil burn severity levels in a temperate climate

Simple, rapid and reliable methods of assessing soil burn severity (SBS) are required in order to prioritize post-fire emergency stabilization actions. SBS proxies based on visual identification and changes in soil organic matter (SOM) content and quality can be related to other soil properties in order to determine the extent to which soil is perturbed following fire. This task is addressed in the present study by an approach involving the use of differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) to determine changes in SOM generated in soils subjected to different levels of SBS.Intact topsoil monoliths comprising the organic horizons and the surface mineral soil (alumic-humic umbrisols) were collected from a representative P. pinaster stand in NW Spain. The monoliths were experimentally burned in a combustion wind tunnel to simulate different fire conditions (fuel bed comprising forest pine litter and wood; air flow, 0.6 m s−1). Changes in OM properties in the soil organic layer and mineral soils samples (0–2 cm) at the different temperatures and SBS levels were identified.For both duff and mineral soil, the data revealed a temperature-induced increase in aromatic compounds and a concomitant decrease of carbohydrates and alkyl products. However, for a given temperature, the degree of carbonization/aromatization was lower in the mineral soil than in the duff, possibly due to the different composition of the OM and to the different combustion conditions. The low degree of aromatization of the organic matter suggests that this soil component could undergo subsequent biological degradation. SOM content and thermal recalcitrance (measured as T50) discriminated the SBS levels. Use of visual identification of SBS levels in combination with DSC-TGA enables rapid evaluation of the spatial variability of the effects of fire on SOM properties. This information is useful to predict soil degradation process and implement emergency soil stabilization techniques.

Morphology of regenerated bone tissue under effect of Easygraft and amorphous calcium phosphate implants.

Background. The theoretical basis of osteoplasty, fully supported by clinical observations, is that violations occur in periodontitis of correlation between tooth and the surrounding tissues, including the microcirculation. However, multifaceted morphological and clinical analysis of effectiveness of the material held EasyGraft was not. Objective. The aim was experimental evaluation of tissue alterations in bone implant materials Easy-Graft® and tricalcium phosphate®. Methods. The comparative analysis of quantitative morphological estimation of regenerative processes in osteal tissue in model of osteal defect is carried out at implantation of material EasyGraft and amor­p­hous calcium phosphate. Results . Implantation of amorphous calcium phosphate on the 7th day of observation defined system defect initial signs of degradation and sprouting of blood vessels. Intervals around the particles of the material have been filled by fibrose tissue. Among the spongy bone substance occurred active formation of new bone tissue. After 15 days of observation of the implanted material adjustment processes were more pronounced: define complex regenerate formed by osteogenic tissue with inclusions of large volume graft particles. On the 30th day of the experiment, all of the defect area was riddled with large bony trabeculae, actively carry out the process of compaction of bone and subsequent biological degradation of the implant. After 60 days, the fragments were subjected defragmentation implant and bone substitution. In the inter-trabecular spaces formed sections filled with yellow bone marrow. Between trabecular bone, and substituted defect area boundary is not observed. Conclusion. EasyGraft and amorphous calcium phosphate undergo resorbtion and thus optimize bone regeneration. Regeneration is accompanied by decreased specific area of the particles implanted and increased integration index and specific density of trabeculae within the reaction zone. Highest intensity of these processes observed in the period from 15th fill the 30th day after implantation.

Hydrophobisation of wood surfaces by combining liquid flame spray (LFS) and plasma treatment: dynamic wetting properties

Abstract The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which the nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate (mWP) method, resulting in advancing and receding contact angles as well as sorption behavior of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behavior. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

Coupling of acrylic dyeing wastewater treatment by heterogeneous Fenton oxidation in a continuous stirred tank reactor with biological degradation in a sequential batch reactor

This work deals with the treatment of a recalcitrant effluent, from the dyeing stage of acrylic fibres, by combination of the heterogeneous Fenton's process in a continuous stirred tank reactor (CSTR) with biological degradation in a sequential batch reactor (SBR). Three different catalysts (a commercial Fe/ZSM-5 zeolite and two distinct Fe-containing activated carbons – ACs – prepared by wet impregnation of iron acetate and iron nitrate) were employed on the Fenton's process, and afterwards a parametric study was carried out to determine the effect of the main operating conditions, namely the hydrogen peroxide feed concentration, temperature and contact time. Under the best operating conditions found, using the activated carbon impregnated with iron nitrate, 62.7% of discolouration and 39.9% of total organic carbon (TOC) reduction were achieved, at steady-state. Furthermore, a considerable increase in the effluent's biodegradability was attained (BOD5:COD ratio increased from <0.001 to 0.27 and SOUR – specific oxygen uptake rate – from <0.2 to 11.1 mg O2/(gVSS·h)), alongside a major decrease in its toxicity (from 92.1 to 94.0% of Vibrio fischeri inhibition down to 6.9–9.9%). This allowed the application of the subsequent biological degradation stage. The combination of the two processes provided a treated effluent that clearly complies with the legislated discharge limits. It was also found that the iron leaching from the three catalysts tested was very small in all runs, a crucial factor for the stability and long-term use of such materials.

Removing PAHs from urban runoff water by combining ozonation and carbon nano-onions

Ozone (O3) is a chemical oxidant capable of transforming polycyclic aromatic hydrocarbons (PAHs) in urban runoff within minutes but complete oxidation to CO2 can take days to weeks. We developed and tested a flow-through system that used ozone to quickly transform PAHs in a runoff stream and then removed the ozone-transformed PAHs via adsorption to carbon nano-onions (CNOs). To quantify the efficacy of this approach, 14C-labeled phenanthrene and benzo(a)pyrene, as well as a mixture of 16 unlabeled PAHs were used as test compounds. These PAHs were pumped from a reservoir into a flow-through reactor that continuously ozonated the solution. Outflow from the reactor then went to a chamber that contained CNOs to adsorb the ozone-transformed PAHs and allowed clean water to pass. By adding a microbial consortium to the CNOs following adsorption, we observed that bacteria were able to degrade the adsorbed products and release more soluble, biodegradable products back into solution. Control treatments confirmed that parent PAH structures (i.e., non-ozonated) were not biologically degraded following CNO adsorption and that O3-transformed PAHs were not released from the CNOs in the absence of bacteria. These results support the combined use of ozone, carbon nano-onions with subsequent biological degradation as a means of removing PAHs from urban runoff or a commercial waste stream.

Reaction of polychlorinated biphenyls and benzenes with neopentyl glycol

The reactions of a mixture of 1,2,3- and 1,2,4-trichlorobenzene and polychlorinated biphenyls congeners of the industrial mixture Sovol with neopentyl glycol in the presence of alkali in DMSO medium was studied. In the conditions of nucleophilic substitution the aromatic compounds are converted completely. Using the method of gas chromatography with flame ionization and mass spectrometric detectors the structure of all synthesized compounds was studied and the following series of increasing reactivity of the polychlorinated biphenyls congeners was revealed: tetra- < penta- < hexachlorobiphenyls. The process can serve as a preliminary step of the preparation of industrial waste for the subsequent biological degradation.

Removal of COD and color from hydrolyzed textile azo dye by combined ozonation and biological treatment

The application of ozonation has been increasing in recent years, the main disadvantage of this type of treatment being related to the by-products, which can have toxic and carcinogenic properties, and therefore should be studied further. In this study, the combined treatment of ozonation and subsequent biological degradation with a biofilm, to reduce the color and chemical oxygen demand (COD), was investigated. The experimental part of the study consisted of two phases. The first phase was the ozonation process, the results obtained demonstrated that the ozonation of Remazol Black B dye at pH values of 3–11, was effective, partially oxidizing and completely decolorizing the effluent, even at relatively high concentrations of the dye (500 mg/L). Color removal efficiencies greater than 96% were obtained in all cases. The degradation kinetics of ozone is a pseudo-first-order reaction with respect to the dye concentration. It was possible to verify that the ozonation process as a pre-treatment increases the dye degradation efficiency. For the biological treatment, an increase in ozonization time increased the dye concentration reduction in hydrolyzed dye synthetic effluent. The toxicological results of the tests with Daphnia Magna showed that there is an increase in toxicity after ozonization and a decrease after submitting the ozonized synthetic wastewater to biological treatment with a biofilm.

Effect of Ozonation on Biodegradability Characteristics of Surplus Activated Sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O3/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.

Combined ozone and microbiological degradation of the six‐membered ring PAH indeno (1,2,3cd)pyrene in water solution

The aim of this work is to investigate between ozone and the model substance lndeno(1,2,3‐cd)pyrene in water as the first step of chemical and microbiological degradation. Ozonation is kept for one hour in an ozone stirring reactor with ozone concentrations of 5–10 mg/1 at low pH value. The mixture of reaction products contains ozonides at low concentration of ozone and hydroxy/keto‐compounds at high ozone concentration. Subsequent biological degradation of ozone products was carried out with a mixed bacterial culture. First experiments show a partial transformation of these products.

Chemical (photo-activated) coupled biological homogeneous degradation of p-nitro- o-toluene-sulfonic acid in a flow reactor

This study presents the combined photochemical (Fenton) and biological flow reactor degradation of p-nitrotoluene- ortho-sulfonic acid ( p-NTS). p-NTS is a compound whose degradation is not possible by waste water bacteria. From this point of view it is considered as a non-biodegradable intermediate found in the manufacture of dyes, surfuctants and brighteners. By way of HPLC technique it is shown that the photochemical pretreatment of p-NTS induces dearomatization due to -OH radical attack. A concomitant 20–25% decrease in the initial carbon content during the photochemical pretreatment was observed along the abatement of the aromaticity. This study shows that the intermediates produced in the pretreatment stage are biodegradable. After pretreatment a minimum residual H 2O 2 (< 0.2 mg l −1) was attained. This level of oxidant did not interfere with the subsequent biological degradation. The influence of the reaction parameters such as: input concentration of p-NTS, rate of H 2O 2 addition, reactor flow rate, TOC reduction rate and BOD 5/COD as a function of the time of photochemical pretreatment are reported. At a flow rate of 0.18 l h −1 (5.5. h residence time) a photochemical degradation efficiency of 75%, a biological degradation efficiency of 52% and an overall degradation efficiency for the coupled process of 88% was observed. The disappearance of p-NTS in the photochemical reactor, the growth and degradation of the benzoquinone like aromatic intermediate followed by the appearance short chain aliphatic compounds are reported as a function of pretreatment time. The increase in BOD/TOC as function of pretreatment time has been correlated to the p-NTS and aliphatic recalcitrants existing in the solution. The biological degradation was observed to be strongly dependent on the flow used and on the pollutant loading of the solution. These were the two main parameters affecting the degradation in the bioreactor.

Overview on Photocatalytic and Electrocatalytic Pretreatment of Industrial Non-Biodegradable Pollutants and Pesticides

Electrochemical and photochemical catalytic pretreatments were studied on diverse non-biodegradable industrial or toxic pollutants using different catalysts. This approach turned out also to be useful to degrade recalcitrant industrial waste waters markedly enhancing the biodegradability and biocompatibility of the treated effluents. In the case of p-toluenesulfonate, a completely non-biodegradable material from the dye industry, the TiO2 photocatalytic material applied for two hours affected total dearomatization allowing efficient subsequent biological degradation. A photochemical-biological flow reactor has been built to attain full mineralization of large volumes of diluted solutions of this xenobiotics as found in polluted water reservoirs. Fenton and photo-Fenton systems have been extensively studied in the abatement of the highly soluble Orange azo-dyes. They induce rapid destructive and low cost degradation of these textile dyes comparable to flocculation/coagulation techniques.