Biodegradation Of Organic Compounds Research Articles

Biological pre-treatments enhance gravity-driven membrane filtration for the decentralized water supply: Linking extracellular polymeric substances formation to flux stabilization

Abstract Gravity-driven membrane (GDM) filtration is a promising technology for decentralized drinking water treatment due to its low energy requirements and simple operation. The reduced flux observed in GDM systems relative to other membrane treatment techniques remains a vital obstacle to their wider application. With the goal of further improving membrane flux and permeate quality, three simple and practical technologies have been examined as pre-treatments for GDM systems, (i) slow filtration with granular activated carbon (GAC), expected to remove both biodegradable and non-biodegradable contaminants, (ii) slow filtration with modified fiber ball (MFB), expected to promote biodegradation of organic compounds and (iii) microfiltration (MF), expected to reject suspended substances and particles. Results indicated that stable permeability increased by approximately 230%, 150% and 100% in GDM systems employing GAC, MFB and MF pre-treatments compared to the control. The dissolved organic compounds (DOC) were removed by approximately 60% and 30% in GAC/GDM and MFB/GDM, while MF/GDM and GDM control were not effective at DOC removal. Correlations between the stable flux and extracellular polymeric substances (EPS) concentration (R2 > 0.9) indicated that reduction of EPS should be responsible for the flux improvements. Tracing the fate of florescent foulants illustrated that the EPS was mainly secreted/converted by the microbes colonizing within the bio-fouling layer of the GDM system. During long-term filtration, assimilable organic compounds (AOC) which can serve as nutrients for the growth of microbes within the bio-fouling layer were efficiently consumed (>50%) by the biological pre-treatments. This reduction in AOC was linked with a reduction in the growth/activity of bacteria within the bio-fouling layer of GDM system and a reduction in EPS accumulation. Overall, biological pre-treatments can significantly enhance the flux and water quality produced by a GDM system without significantly increasing the operation and maintenance. These improvements in flux and water quality can hopefully spark wider adoption of GDM as an economical and environmentally-friendly technology for decentralized drinking water treatment.

Kinetics and efficiency of ozone for treatment of landfill leachate including the effect of previous microbiological treatment.

The application of conventional physicochemical and microbiological techniques for the removal of organic pollutants has limitations for its utilization on wastewaters as landfill leachates because of their high concentration of not easily biodegradable organic compounds. The use of ozone-based technologies is an alternative and complementary treatment for this type of wastewaters. This paper reports the study of the degradation of landfill leachates from different stages of a treatment plant using ozone and ozone + UV. The experimental work included the determination of the temporal evolution of COD, TOC, UV254, and color. Along the experimental runs, the instantaneous off-gas ozone concentration was measured. The reaction kinetics follows a global second order expression with respect to COD and ozone concentrations. A kinetic model which takes into account the gas liquid mass transfer coupled with the chemical reaction was developed, and the corresponding parameters of the reacting system were determined. The mathematical model is able to appropriately simulate COD and ozone concentrations but exhibiting limitations when varying the leachate type. The potential application of ozone was verified, although the estimated efficiencies for COD removal and ozone consumption as well as the effect of UV radiation show variations on their trends. In this sense, it is interesting to note that the relative ozone yield has significant oscillations as the reaction proceeds. Finally, the set of experimental results demonstrates the crucial importance of the selection of process conditions to improve ozone efficiencies. This approach should consider variations in the ozone supply in order to minimize losses as well as the design of exhaustion methods as multiple stage reactors using chemical engineering design tools.

Use of aged sludge bioaugmentation in two-stage activated sludge system to enhance the biodegradation of toxic organic compounds in high strength wastewater

This research investigates the toxic organic compounds biodegradation efficiency of two-stage activated sludge systems with (bioaugmented) and without aged sludge bioaugmentation (non-bioaugmented). The influent was a mixture of leachate and agriculture wastewater (1:1, v/v), used as the representative high strength wastewater. The bioaugmented and non-bioaugmented systems were operated in parallel, with three levels (low, moderate, and high) of concentrations of organics, nitrogen, and toxic organic compounds in the influent (conditions 1, 2, and 3). The results showed that both systems could efficiently degrade the organic compounds. Nevertheless, the toxic organic compounds biodegradation efficiency of the bioaugmented system was higher than that of the non-bioaugmented one. The bioaugmentation enhanced the overall removal efficiency under conditions 1 and 2. However, the bioaugmented system became less effective under condition 3. Further analysis indicated that the bacterial groups essential to the toxic organic compounds biodegradation were abundant in the aged sludge, including heterotrophic bacteria, heterotrophic nitrifying bacteria, and nitrifying bacteria. The abundance of the effective bacteria improved the biodegradation and wastewater treatment performance of the bioaugmented system. In essence, the aged sludge bioaugmentation is a viable and eco-friendly solution to improving the treatment efficiency of the biological activated sludge system, despite limited biodegradation efficiency in an elevated compounds-concentration environment.

Effects of Sphingomonas sp. GY2B on the structure and physicochemical properties of stearic acid-modified montmorillonite in the biodegradation of phenanthrene

Abstract The objective of this study was to investigate the interaction between stearic acid-modified montmorillonite (SA-Mt) and Sphingomonas sp. GY2B and its effect on the physical and chemical properties of montmorillonite in the 2 days' biodegradation of phenanthrene. Due to bacterial activities, surface and colloidal properties of the bacteria-treated sample evidently changed in comparison with the untreated SA-Mt. Changes in surface morphology and the agglomerate state of SA-Mt were clearly observed by scanning electron microscopy (SEM) after interaction with GY2B for 2 days. Although the interlayer space of SA-Mt structure remained basically unchanged, the decrease of the structural order and the appearance and shift of several absorbance bands in the Fourier transform infrared (FTIR) spectra verified the structural changes of SA-Mt after bacterial treatment. Besides, the second derivative infrared spectra indicated that bacterial growth and metabolism largely affected the microstructure in SA-Mt. Dissolution rates of major elements were obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES) in the solution, which revealed that bacterial activities enhanced the release of major elements and brought about a significant higher dissolution of Si preferentially from the tetrahedral sheet edges of SA-Mt than Al. The improvement of elemental dissolution in the biotic experiment was attributed to the combined action of pH effect and ligand-promoted process. These results substantiated that microorganisms have a considerable influence on the physicochemical properties and structure in the clay-modulated biodegradation of organic compounds. This study has profound impacts on the clay-modulated biodegradation of hydrophobic organic contaminants in the environment.

Effect of vegetation type on treatment performance and bioelectric production of constructed wetland modules combined with microbial fuel cell (CW-MFC) treating synthetic wastewater.

An operation of microcosm-constructed wetland modules combined with microbial fuel cell device (CW-MFC) was assessed for wastewater treatment and bioelectric generation. One of the crucial aims of the present experiment is also to determine effect of vegetation on wastewater treatment process and bioelectric production in wetland matrix with microbial fuel cell. Accordingly, CW-MFC modules with vegetation had higher treatment efficiency compared to unplanted wetland module, and average COD, NH4+, and TP removal efficiency in vegetated wetland modules were ranged from 85 to 88%, 95 to 97%, and 95 to 97%, respectively. However, the highest NO3- removal (63%) was achieved by unplanted control module during the experiment period. The maximum average output voltage, power density, and Coulombic efficiency were obtained in wetland module vegetated with Typha angustifolia for 1.01 ± 0.14V, 7.47 ± 13.7mWatt/m2, and 8.28 ± 10.4%, respectively. The results suggest that the presence of Typha angustifolia vegetation in the CW-MFC matrix provides the benefits for treatment efficiency and bioelectric production; thus, it increases microbial activities which are responsible for biodegradation of organic compounds and catalyzed to electron flow from anode to cathode. Consequently, we suggest that engineers can use vegetated wetland matrix with Typha angustifolia in CW-MFC module in order to maximize treatment efficiency and bioelectric production.

Effects of interaction between montmorillonite and Sphingomonas sp. GY2B on the physical and chemical properties of montmorillonite in the clay-modulated biodegradation of phenanthrene

Environmental contextInteractions between microbes and minerals can influence geochemical reactions, and hence are of fundamental importance in natural environmental processes. We investigate the effects of Sphingomonas sp. on the structure and physicochemical properties of montmorillonite, a common clay mineral, and determine how this interaction influences the biodegradation of phenanthrene. The findings have profound impact on the clay-modulated biodegradation of organic compounds in the environment. AbstractWe investigate the effect of Sphingomonas sp. GY2B on the structure and physicochemical properties of montmorillonite (Mt). The simultaneous biodegradation of a polycyclic aromatic hydrocarbon compound, phenanthrene, was also monitored. After interaction with bacteria for 2 days, the increases of the specific surface area (SSA) and micropore volume, differences of the thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) patterns and the morphological changes revealed modification of the physicochemical properties and mineral surface. Although the interlayer spacing of Mt remained unchanged, the appearance and shift of several vibration peaks in the Fourier transform infrared (FTIR) spectra confirmed the structural changes of Mt arising from bacterial activities. Concentrations of the major elements of montmorillonite changed greatly in the aqueous solution, especially Si, Al, Fe and Ca. Based on the analyses of X-ray diffraction (XRD) and FTIR, these changes were mainly ascribed to the formation of precipitates and minerals in the biotic experiment. Changes in the release rate of different elements also substantiated that the GY2B strain has a considerable impact on the dissolution of montmorillonite. Additionally, a preferential release of Si and the 27Al and 29Si cross-polarisation magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) spectra of bacteria-untreated samples demonstrated that tetrahedral sheets were preferentially destroyed and octahedral sheets in montmorillonite were dissolved. These results showed that microorganisms can greatly affect the physical and chemical properties of clay minerals in the clay-modulated biodegradation of hydrophobic organic contaminants. This study provides valuable insight into the clay-modulated microbial remediation of organic pollutants in the environment.

Anaerobic biodegradation of dissolved ethanol in a pilot-scale sand aquifer: Variability in plume (redox) biogeochemistry

The use of ethanol in alternative fuels has led to contamination of groundwater with high concentrations of this easily biodegradable organic compound. Previous laboratory and field studies have shown vigorous biodegradation of ethanol plumes, with prevalence of reducing conditions and methanogenesis. The objective of this study was to further our understanding of the dynamic biogeochemistry processes, especially dissolved gas production, that may occur in developing and aging plume cores at sites with ethanol or other organic contamination of groundwater. The experiment performed involved highly-detailed spatial and temporal monitoring of ethanol biodegradation in a 2-dimensional (175cm high×525cm long) sand aquifer tank for 330days, with a vertical shift in plume position and increased nutrient inputs occurring at ~Day 100. Rapid onset of fermentation, denitrification, sulphate-reduction and iron(III)-reduction occurred following dissolved ethanol addition, with the eventual widespread development of methanogenesis. The detailed observations also demonstrate a redox zonation that supports the plume fringe concept, secondary reactions resulting from a changing/moving plume, and time lags for the various biodegradation processes. Additional highlights include: i) the highest dissolved H2 concentrations yet reported for groundwater, possibly linked to vigorous fermentation in the absence of common terminal electron-acceptors (i.e., dissolved oxygen, nitrate, and sulphate, and iron(III)-minerals) and methanogenesis; ii) evidence of phosphorus nutrient limitation, which stalled ethanol biodegradation and perhaps delayed the onset of methanogenesis; and iii) the occurrence of dissimilatory nitrate reduction to ammonium, which has not been reported for ethanol biodegradation to date.

Slowly biodegradable organic compounds impact the biostability of non-chlorinated drinking water produced from surface water

It is possible to distribute drinking water without a disinfectant residual when the treated water is biologically stable. The objective of this study was to determine the impact of easily and slowly biodegradable compounds on the biostability of the drinking water at three full-scale production plants which use the same surface water, and on the regrowth conditions in the related distribution systems. Easily biodegradable compounds in the drinking water were determined with AOC-P17/Nox during 2012–2015. Slowly biodegradable organic compounds measured as particulate and/or high-molecular organic carbon (PHMOC), were monitored at the inlet and after the different treatment stages of the three treatments during the same period. The results show that PHMOC (300–470 μg C L−1) was approximately 10% of the TOC in the surface water and was removed to 50–100 μg C L−1. The PHMOC in the water consisted of 40–60% of carbohydrates and 10% of proteins. A significant and strong positive correlation was observed for PHMOC concentrations and two recently introduced bioassay methods for slowly biodegradable compounds (AOC-A3 and biomass production potential, BPC14). Moreover, these three parameters in the biological active carbon effluent (BACF) of the three plants showed a positive correlation with regrowth in the drinking water distribution system, which was assessed with Aeromonas, heterotrophic plate counts, coliforms and large invertebrates. In contrast, the AOC-P17/Nox concentrations did not correlate with these regrowth parameters. We therefore conclude that slowly biodegradable compounds in the treated water from these treatment plants seem to have a greater impact on regrowth in the distribution system than easily biodegradable compounds.

Monitoring Microbial Mineralization Using Reverse Stable Isotope Labeling Analysis by Mid-Infrared Laser Spectroscopy

Assessing the biodegradation of organic compounds is a frequent question in environmental science. Here, we present a sensitive, inexpensive, and simple approach to monitor microbial mineralization using reverse stable isotope labeling analysis (RIL) of dissolved inorganic carbon (DIC). The medium for the biodegradation assay contains regular organic compounds and 13C-labeled DIC with 13C atom fractions (x(13C)DIC) higher than natural abundance (typically 2–50%). The produced CO2 (x(13C) ≈ 1.11%) gradually dilutes the initial x(13C)DIC allowing to quantify microbial mineralization using mass-balance calculations. For 13C-enriched CO2 samples, a newly developed isotope ratio mid-infrared spectrometer was introduced with a precision of x(13C) < 0.006%. As an example for extremely difficult and slowly degradable compounds, CO2 production was close to the theoretical stoichiometry for anaerobic naphthalene degradation by a sulfate-reducing enrichment culture. Furthermore, we could measure the aerobic degradation of dissolved organic carbon (DOC) adsorbed to granular activated carbon in a drinking water production plant, which cannot be labeled with 13C. Thus, the RIL approach can be applied to sensitively monitor biodegradation of various organic compounds under anoxic or oxic conditions.

Physicochemical properties of some hydrophobic room‐temperature ionic liquids applied to volatile organic compounds biodegradation processes

AbstractBACKGROUNDIonic liquids (IL) are an interesting solvent choice for specific industrial applications since physicochemical properties can be fine‐tuned by modifying the substituent groups or the cation/anion pair. Hydrophobic ILs are considered green solvents and known to be good absorbents for hydrophobic organic compounds. Given their physicochemical properties an industrial application of such compounds is conceivable. Classical physicochemical properties such as density, viscosity and surface tension have a strong influence on the fluid dynamics; they were therefore measured and determined.RESULTSThe density, viscosity and surface tension of 23 hydrophobic ILs were measured at room temperature. These compounds are potential candidates for the absorption and biodegradation of volatile organic compounds (VOCs) in a two‐phase partitioning bioreactor. The thermal expansion coefficient, molecular volume, standard molar entropy and lattice energy were determined for each IL using empirical and semi‐empirical equations based on the density values. Viscosity values were correlated by the Arrhenius equation. Then, the surface excess enthalpy and surface excess entropy were determined from the surface tension values.CONCLUSIONThe influence of the presence of different functional moieties (unsaturated bonding, oxygenated and cyanide) and the side chain length in the physicochemical properties of these hydrophobic ILs was discussed, since their presence affected directly the density, viscosity and surface tension. © 2017 Society of Chemical Industry

EVALUATION OF TREATABILITY OF HIGH STRENGTH WASTEWATER IN A THREE STAGE-ROTATING BIOLOGICAL CONTACTOR

Cheese whey effluent contains biodegradable organic compounds in the range of 40 to 80 g·L–1. In this study, a three–stage rotating biological contactor was fabricated as a bench scale experimental unit to remove organic matters from cheese whey. First, the treatability of cheese whey effluent in the three–stage rotating biological contactor (RBC) was evaluated. Then the effect of extended specific surface area (SSA) and recirculation rate on COD removal was investigated. The obtained results showed that the organic removal rate increased with an increase in loading rate, till other limiting parameters affect the process. Prior to application of the designated modifications to the system, maximum COD removal efficiency at hrts of 24 and 36 h with OLR of 50 gcod·L–1·d–1 was 90 and 92.4%, respectively. The removal efficiency was improved as a result of increasing the SSA and recirculation rate. Also, recirculation rate may assist to increase the DO level of the wastewater, especially at high olrs. To sum up, obtained results showed that whey effluent has been efficiently treated in a continuous operation of bench scale RBC.

Optimization of moving bed biofilm reactors for oil sands process-affected water treatment: The effect of HRT and ammonia concentrations

Two moving bed biofilm reactors (MBBRs) were optimized to improve the biodegradation of organic compounds in raw and ozonated OSPW by changing the hydraulic retention time (HRT) and the influent ammonia concentrations. During the five stages, the average COD removal reached 50.8±3.4%, 52.8±6.5%, 54.7±4.3%, 56.3±2.2%, and 58.0±2.3% respectively in raw OSPW MBBR, and 54.6±3.8%, 57.2±7.1%, 55.5±5.8%, 58.3±2.2%, and 60.7±2.3% respectively in ozonated OSPW MBBR. Welch's weighted ANOVA tests show that the increase in ammonia levels significantly improved the COD removal in the two systems, while the HRT was an important parameter for COD decrease in the raw OSPW MBBR. Compared to the HRT, the increase in ammonia concentrations were more beneficial for acid extractable fraction (AEF) degradation and the average AEF removal reached 29.80% (raw OSPW MBBR) and 16.50% (ozonated OSPW MBBR) by the end of the optimization (Stage V; HRT=96h, 60mg/L NH4+-N). >98% of the NH4+-N was removed in the two MBBR systems, showing good nitrification. Microtoxicity tests showed that no significant correlations were found between HRT/ammonia levels and the OSPW toxicity changes toward V. fischeri. Spearman's rank correlation analysis was applied for q-PCR data, showing that positive correlations between the removal efficiencies of AEF and NSR and NirK gene copies were observed in the raw OSPW MBBR system, while positive correlations between AEF removal efficiency and total bacteria gene, NSR, Nitro, and NirK gene copies were observed in the ozonated OSPW MBBR system.

Ultimate composition analysis of municipal solid waste in Muscat

Properly uncontrolled municipal solid wastes (MSWs) may affect public health and the environment. This study investigates the ultimate composition of the MSWs in Muscat, Oman. To achieve this, a set of 22 solid and leachate samples was collected in February 2015. The solid samples were screened according to their size fractions from less than 8 mm up to 100 mm. In addition, the fresh and old leachate samples were examined as well. The ultimate analyses were conducted for various physical and chemical characteristics of the MSW samples, e.g., composition of waste, moisture content (MC), volatile content (VC), loss on ignition, total oxides, elemental analysis, chemical content, heating value and energy content. Moreover, the leachates were analyzed for pH, electrical conductivity (EC), turbidity, total solid (TS), bacteriological analysis, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), ammonia nitrogen, sodium and potassium, and major anions. From the study, it was found that more than 43% by weight of the disposed materials at the landfill consisted of biodegradable organic compounds. The results also showed that the main components of the total generated wastes were plastic wraps (24%), cardboard (14%) and food wastes (8%). This study also recommends a “waste-to-energy” program, because of the high-energy content of the MSWs (>15,000 kJ/kg). The chemical formulas of the MSW were obtained as C215H395O120N2S with sulfur and C125H230O70N without sulfur element.

SYNTHESIS, CHARACTERIZATION AND FUNCTIONALIZATION OF MCM-41 FOR THE REMOVAL OF ORGANIC COMPOUNDS FROM WASTEWATERS

In this study was synthesized MCM-41 mesoporous silica by hydrothermal treatment and funtionalized with titanium in order to obtain mesoporous materials with high surfacea area and photocatalytic activity in photodegradation of organic compounds as antibiotics. The functionalization of the synthesized support material was achieved by impregnation from alcoholic solution. The obtained materials (MCM-41) and (Ti-MCM-41) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), FTIR and UV-Vis spectroscopy. A high photocatalytic activity of TiMCM-41 was obtained in photocatalytic degradation of hardly biodegradable organic compounds as erythromycin.

The effect of thermohydrolysis on biological properties of selected chemical compounds

One of the negative effects of the continuous development of civilization which is observed in recent decades is an increase in the number and variety of pollutants released into the environment. These substances have ecotoxic properties and pose a serious threat to humans and proper functioning of the ecosystem. Their presence in the environment forces the development of new pollution control techniques. One of the latest and very promising methods to destroy organic contaminants using the properties of water which exceeded the critical point is thermohydrolysis in supercritical water. The aim of this study was to investigate thermohydrolysis in supercritical water conditions and to check its suitability for removal of hardly biodegradable organic compounds present in wastewater. Tests for toxicity of these compounds to aquatic organisms such as sewage bacteria, crustaceans and guppy fish were also performed and the degree of their biological decomposition was determined. Biological studies were carried out on starting compounds and after the processes of thermohydrolysis. The research material included p-nitrotoluene sulfonic acid (PNTS), 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNSDS) and 4,4′-diaminostilbene-2,2′-disulfonic acid (DASDS). The research leads to the conclusion that the reactions occurring during high-temperature thermohydrolysis of the three tested compounds are extremely complex. Results of biological studies indicate a significant decrease in toxicity and increase in the biodegradability of products obtained after the process of thermohydrolysis.

Mini review: Update on bioaugmentation in anaerobic processes for biogas production

Anaerobic digestion (AD) is increasingly being used and exploited as a strategy to generate biomethane, which can be used as a renewable and clean energy. AD rests on the biodegradation of organic compounds in anaerobic condition, and these organic compounds are generally agricultural-, industrial- and domestic-wastes. However, problems of AD decrease efficiency, as the result of bioreactor stress, are generally encountered. The primarily cause of this stress is the presence of high concentrations of inhibitory substances such as nitrate, sulfate, heavy metals and oxygen among others. Another cause of AD decrease efficiency is the use of organic compounds that are less amenable to biodegradation such as lignocellulosic compounds. One of the strategies to overcome these limitations is the addition in bioreactors of “stress resistant”- or “efficient biomethane generating”- microorganisms to improve AD process. This strategy, known as bioaugmentation, has been used for the last 15 years to increase biomethane production. In this review, work carried out on this bioaugmentation process has been summarised, and new strategies that could be used or exploited to improve the success of this approach have also been discussed.

Hydrochemical Characterization of a Tropical, Coastal Aquifer Affected by Landfill Leachate and Seawater Intrusion

The hydrochemistry of landfill leachate and groundwater is affected by not only waste degradation processes, but also by external factors such as the geography of the landfilling site. Knowledge on the fate of landfill leachate in tropical countries will be beneficial for monitoring and regulatory purposes. We studied the Keputih landfill close to the sea at Surabaya, Indonesia: (1) to assess leachate and groundwater hydrochemistry with respect to contamination and seawater intrusion, (2) to investigate the seasonal effects on hydrochemical composition; and (3) to determine redox conditions in order to evaluate the potential for natural attenuation through microbe-mediated electron-accepting processes. We document an influence from sea water intrusion on groundwater hydrochemistry on top of the influences from the landfill itself. Leachate had a high electrical conductivity and high COD, and contained high concentrations of NH4+, HCO3-, SO42-, Fe2+ and Cl-. Concentrations were significantly influenced by season, except for COD and SO42-. The groundwater at locations surrounding the landfill was also contaminated by leachate and concentrations of groundwater contaminants were higher than national regulatory standards in Indonesia for drinking water. The abundance of SO42- in groundwater indicates a large potential for anaerobic biodegradation of organic compounds. Based on the relative concentrations of Cl- and SO42- an influence of the sea water on groundwater hydrochemistry was obvious. Landfilling in developing countries often occurs in coastal areas, therefore we emphasize the need to study microbial community structure and functioning in relation to degradation of landfill leachate in tropical coastal areas impacted by seawater infiltration.

Old landfill leachate treatment through multistage process: membrane adsorption bioreactor and nanofitration.

A bench-scale integrated process based on submerged aerobic powdered activated carbon-membrane bioreactor (PAC-MBR) has been utilized and established for the treatment of landfill leachate. The results showed that the submerged PAC-MBR system effectively removed biodegradable trace organic compounds by the average removal rate about 71% at optimum food to microorganism (F/M) ratio of 0.4gCOD/gday under a HRT of 24h. Adding nanofiltration (NF) process increased the treatment efficiency up to 99%. Further, adding powdered activated carbon to activated sludge (AS) resulted in a higher adsorption capacity in comparison with AS. Adsorption isotherms were investigated and fitted by the Langmuir and Freundlich isotherm models in which the Langmuir model performed better. The specific oxygen uptake rate (SOUR) showed that adding PAC reduces the effects of COD on microorganism activities. NH3-N, TKN and Heavy metals removal efficiency amounted to 97±2, 96±2, and 99±2%, respectively.

The Current Research Status of PLGA as Drug and Gene Carrier

PLGA, poly (lactic-co-glycolic-acid), is a kind of biodegradable functional macromolecular organic compounds. PLGA, certified by the Food and Drug Administration (FDA), possesses desirable features of biocompatibility, nontoxicity and no immune response, and is being widely applied to human clinical medical research. Because of its biodegradability, simple synthetic methods, controllability of degrading rate and desirable plasticity, PLGA was applied in large quantity into the carrier materials which is to control the release in recent years, gradually propelling PLGA microsphere controlled release system to be the most ideal drug-carrier system at present. As the carrier of drug and genes, PLGA is mainly researched on its features as the carrier, synthetic methods, different surface modification methods, and the applications on different drugs, genetic treatments and genetic vaccines.

Dynamics of changes in coplanar and indicator PCB in sewage sludge during mesophilic methane digestion

Research was conducted, which aim was to evaluate the influence of mesophilic methane digestion on degradation of coplanar and indicator PCB in sewage sludge, and on dynamics of changes of these congeners during the process. For the research, sewage sludge from a municipal wastewater treatment plant were used. Mesophilic digestion was conducted at the temperature of 36°C±1°C. The anaerobic stabilization processes of sewage sludge occurred correctly what was confirmed by appropriate values of pH, content of volatile fatty acids (VFA) and ratio of VFA to alkalinity. Biodegradation of organic compounds in sewage sludge was confirmed by the decrease in total solids (by 26%) and volatile solids (by 36%). Up to the 3rd day of the digestion process no statistically significant differences in concentration of both coplanar and indicator PCB was observed. During the following days of the process, an increase in lower chlorinated PCB concentration was demonstrated and a decrease in concentration of higher chlorinated congeners (penta-, hexa-, and heptachlorobiphenyls). After the digestion, a decrease in higher chlorinated congener concentration was found. Significant degradation was demonstrated for coplanar PCB 169 (from 77.8 to 80.5%), and indicator PCB 180 (from 57.1 to 90.3%) and PCB 153 (from 60.4 to 79.2%).