Aerobic Purification Research Articles

The Effects of Low-frequency Pulsed Electromagnetic Fields on the Cleaning of Household Wastewater

The effect of pulsed EMF with a pulse repetition frequency of 16 Hz on the decomposition of organic compounds in wastewater in the presence of activated sludge microorganisms has been studied. It is shown that aerobic purification of a mixture of wastewater and activated sludge in the presence of a continuous pulsed electromagnetic field with a frequency of 16 Hz and a magnetic induction of no more than 0.5 μT accelerates the process of ammonification by 25 %, nitrification and denitrification by 15 %, reduction of COD by approximately 20 %.The intensity of the increase in the biomass of activated sludge and the rate of its deposition were noted.

Wastewater treatment using microbial enzymatic mixture

The effectiveness of the use of microbial enzymes as a wastewater treatment method depends on factors such as temperature, pressure, and oxygenation level, among others. However, very few scientific studies have provided real data regarding the evaluation of the applicability of this type of treatment. This research was therefore carried out to evaluate the effect of temperature and aerobic treatment time on the level of treatment of wastewater pollutants, with a mixture composed of enzymes and aerobic microorganisms under environmental conditions in the city of Huancayo, Peru. For this purpose, synthetic wastewater samples were prepared, considering a value of CODinitial= 800 mg L-1. One group of experiments was conducted at a 20°C controlled temperature and another group without control. The following average kinetic constants were obtained as results (Ko= 1.662 d-1, Kc=2.53 mg COD mg-1 VSS) when the T°= 20°C. For the experiments where the T° was not controlled, the average constants were: Ko= 1.217 d-1, Kc=1.24 mg COD mg-1 SSV. We observed from the measurements that the pollutant removal was adjusted to the kinetic model proposed by Orozco, and the biomass production was adjusted to the stoichiometric equation of biomass production with endogenous respiration. Therefore, we concluded that the effect of temperature control and treatment time on the level of purification caused by the microbial enzymatic product is significant at a 95% confidence level.
 Keywords: aerobic purification, biomass, digesting bacteria, kinetics, microorganisms.

Dual-site activation enhanced photocatalytic removal of no with Au/CeO2

Photocatalytic technology provides an effective strategy for aerobic purification of dilute gaseous NO pollutant, but suffers from its low efficiency. In this study, we demonstrate that the bicomponent Au/CeO2 photocatalyst possesses an enhanced photocatalytic NO removal performance under visible light irradiation, with a higher NO conversion efficiency (65%) and triple rate constant (0.1451 min−1) versus CeO2 (50%, 0.0448 min−1). Density function theory calculations and experimental results revealed that oxygen vacancies on the CeO2 component could favorably initiate the adsorption and activation of O2 to generate O2−, simultaneously, Au nanoparticles loaded on the CeO2 surface were active centers for adsorption and activation of NO to produce NO+ by plasmonic holes of the Au under visible light irradiation. Subsequently, these O2− and NO+ species generated via dual-site activation pathway on Au/CeO2 photocatalyst reacted spontaneously to generate the final NO3−, leading to enhanced photocatalytic removal of NO. This study sheds light on a dual-site induced photocatalytic NO oxidation and advances the design of effective air purification photocatalyst.

Anaerobic Protein Purification and Kinetic Analysis via Oxygen Electrode for Studying DesB Dioxygenase Activity and Inhibition.

Oxygen-sensitive proteins, including those enzymes which utilize oxygen as a substrate, can have reduced stability when purified using traditional aerobic purification methods. This manuscript illustrates the technical details involved in the anaerobic purification process, including the preparation of buffers and reagents, the methods for column chromatography in a glove box, and the desalting of the protein prior to kinetics. Also described are the methods for preparing and using an oxygen electrode to perform kinetic characterization of an oxygen-utilizing enzyme. These methods are illustrated using the dioxygenase enzyme DesB, a gallate dioxygenase from the bacterium Sphingobium sp. strain SYK-6.

Optimization of the process of anaerobic-aerobic purification of waste waters of food production using the spatial separation of stages

The advanced energyand resource saving technologies for purification of industrial waste waters from the food production include both anaerobic biotechnologies, and the combined ones, which include anaerobic and aerobic purification steps. They possess such advantages as economic efficiency, high purification efficiency, minimal formation of excess sludge and ability to obtain alternative energy carrier - biogas. The aim of this investigation was to perform optimization of the process of anaerobic-aerobic biological purification of wastewaters from the milk treatment enterprise. During our investigation we have studied relations between the efficiency of the process of anaerobic-aerobic biological purification of wastewaters of the milk treatment enterprise and specific organic load. We investigated influence of the spatial separation of the anaerobic step of purification with directed succession of the microbial community, which performs the sequence of destruction of the organic compound on the process efficiency. It was shown, that the preliminary anaerobic purification of wastewaters from the milk treatment enterprise allows one to significantly reduce organic load at the aerobic stage of the purification facilities and remove up to 85% of the organic compound. With increase of the specific organic load from 1.4 up to 2.8 kg COD·m -3·days-1 we see a drastic improvement of the efficiency characteristics both for anaerobic and aerobic stages. The redox-potential of the fermentation medium depends on the metabolitic activity of the microbial community and might be used as an efficiency characteristics for destruction of the organic compound at the anaerobic stage, and as an indicator for the oxygen saturation of the medium at the aerobic stage of purification.

Комп’ютерне моделювання процесу аеробного очищення стічних вод

Комп’ютерне моделювання процесу аеробного очищення стічних вод

Kinetic and hydrodynamic assessment of an aerobic purification system for petroleum refinery wastewater treatment in a continuous regime

Different petroleum refinery wastewater (PRWW) loading rates and solid retention times were employed to determine the coefficients of chemical oxygen demand (COD) removal kinetics using a continuous stirred tank reactor (CSTR). To evaluate kinetic coefficients, a new approach that could be useful for all recalcitrant wastewater samples was developed. The observed range of COD removal was from 89.9% to 96.5%, with an organic loading rate range of 0.177 kg COD kg−1 mixed liquor volatile suspended solids per day (MLVSS.d) to 0.744 kg COD kg−1 MLVSS.d. Different kinetic parameters were computed and compared with the theoretical parameters. The specific growth rate obtained in this study exhibited the efficiency and faster biodegradation rate of the proposed method compared with the previous respirometric method for treating PRWW. High sensitivity was observed for effluent COD toward Ks and μmax. Bacterial identification determined that the predominant bacteria were Pseudomonas putida, Acidovorax delafieldii, and Aeromonas hydrophila. Residence time distribution (RTD) curve analysis provided a better estimate for complete mixing at a hydraulic retention time (HRT) than at 19.2 h HRT and 25.6 h HRT.

Influence of the Silicon- and Element-Organic Compounds on the Process of Biochemical Oxidation in the Organic Contaminations

One of the methods used in practice for the purification of wastewater from vegetable-processing enterprises is biological method of aerobic purification. With the aim to increase air-tank capacity used in traditional systems of biochemical purification of wastewater, different ways effecting to the process of vital activity of microorganisms of active sludge are applied. On the one hand, using the compositions of different salts and complex organic biogenous supplements prevents from the accumulation of some anions in the amounts exceeding the limited concentration, on the other hand- allows different groups of microorganisms to choose biogenous elements, which they assimilate easily and fully. It is known, that compounds of silicon and germanium can cause stimulating effects [1] to the organisms of active sludge. The goal of present studies is the intensification of biological processes of oxidation of organic contamination in wastewater by new bio-degradable chemical compounds or compositions on their basis, and by bio-sorbents.

Production of biohydrogen by heterologous expression of oxygen-tolerant Hydrogenovibrio marinus [NiFe]-hydrogenase in Escherichia coli

Oxygen sensitivity of hydrogenase is a critical issue in efficient biological hydrogen production. In the present study, oxygen-tolerant [NiFe]-hydrogenase from the marine bacterium, Hydrogenovibrio marinus, was heterologously expressed in Escherichia coli, for the first time. Recombinant E. coli BL21 expressing H. marinus [NiFe]-hydrogenase actively produced hydrogen, but the parent strain did not. Recombinant H. marinus hydrogenase required both nickel and iron for biological activity. Compared to the recombinant E. coli [NiFe]-hydrogenase 1 described in our previous report, recombinant H. marinus [NiFe]-hydrogenase displayed 1.6- to 1.7-fold higher hydrogen production activity in vitro. Importantly, H. marinus [NiFe]-hydrogenase exhibited relatively good oxygen tolerance in analyses involving changes of surface aeration and oxygen proportion within a gas mixture. Specifically, recombinant H. marinus [NiFe]-hydrogenase produced ∼7- to 9-fold more hydrogen than did E. coli [NiFe]-hydrogenase 1 in a gaseous environment containing 5-10% (v/v) oxygen. In addition, purified H. marinus [NiFe]-hydrogenase displayed a hydrogen evolution activity of ∼28.8 nmol H₂/(minmg protein) under normal aerobic purification conditions. Based on these results, we suggest that oxygen-tolerant H. marinus [NiFe]-hydrogenase can be employed for in vivo and in vitro biohydrogen production without requirement for strictly anaerobic facilities.

Identification of Eukaryotic and Prokaryotic Methylthiotransferase for Biosynthesis of 2-Methylthio-N6-threonylcarbamoyladenosine in tRNA

Bacterial and eukaryotic transfer RNAs have been shown to contain hypermodified adenosine, 2-methylthio-N(6)-threonylcarbamoyladenosine, at position 37 (A(37)) adjacent to the 3'-end of the anticodon, which is essential for efficient and highly accurate protein translation by the ribosome. Using a combination of bioinformatic sequence analysis and in vivo assay coupled to HPLC/MS technique, we have identified, from distinct sequence signatures, two methylthiotransferase (MTTase) subfamilies, designated as MtaB in bacterial cells and e-MtaB in eukaryotic and archaeal cells. Both subfamilies are responsible for the transformation of N(6)-threonylcarbamoyladenosine into 2-methylthio-N(6)-threonylcarbamoyladenosine. Recently, a variant within the human CDKAL1 gene belonging to the e-MtaB subfamily was shown to predispose for type 2 diabetes. CDKAL1 is thus the first eukaryotic MTTase identified so far. Using purified preparations of Bacillus subtilis MtaB (YqeV), a CDKAL1 bacterial homolog, we demonstrate that YqeV/CDKAL1 enzymes, as the previously studied MTTases MiaB and RimO, contain two [4Fe-4S] clusters. This work lays the foundation for elucidating the function of CDKAL1.

SufU Is an Essential Iron-Sulfur Cluster Scaffold Protein in Bacillus subtilis

Bacteria use three distinct systems for iron-sulfur (Fe/S) cluster biogenesis: the ISC, SUF, and NIF machineries. The ISC and SUF systems are widely distributed, and many bacteria possess both of them. In Escherichia coli, ISC is the major and constitutive system, whereas SUF is induced under iron starvation and/or oxidative stress. Genomic analysis of the Fe/S cluster biosynthesis genes in Bacillus subtilis suggests that this bacterium's genome encodes only a SUF system consisting of a sufCDSUB gene cluster and a distant sufA gene. Mutant analysis of the putative Fe/S scaffold genes sufU and sufA revealed that sufU is essential for growth under minimal standard conditions, but not sufA. The drastic growth retardation of a conditional mutant depleted of SufU was coupled with a severe reduction of aconitase and succinate dehydrogenase activities in total-cell lysates, suggesting a crucial function of SufU in Fe/S protein biogenesis. Recombinant SufU was devoid of Fe/S clusters after aerobic purification. Upon in vitro reconstitution, SufU bound an Fe/S cluster with up to approximately 1.5 Fe and S per monomer. The assembled Fe/S cluster could be transferred from SufU to the apo form of isopropylmalate isomerase Leu1, rapidly forming catalytically active [4Fe-4S]-containing holo-enzyme. In contrast to native SufU, its D43A variant carried a Fe/S cluster after aerobic purification, indicating that the cluster is stabilized by this mutation. Further, we show that apo-SufU is an activator of the cysteine desulfurase SufS by enhancing its activity about 40-fold in vitro. SufS-dependent formation of holo-SufU suggests that SufU functions as an Fe/S cluster scaffold protein tightly cooperating with the SufS cysteine desulfurase.

Aerobic purification of dairy wastewater in continuous regime: Part II: Kinetic study of the organic matter removal in two reactor configurations

Biokinetic equations are needed to determine net microbial growth rate or its reciprocal mean cell residence time, effluent substrate concentrations, observed yield coefficients, decay rate constants… In this paper an attempt is made to establish the kinetic parameters that describe the organic matter biodegradation process in dairy wastewaters. Two different experimental devices in continuous regime were used: a first system with a working volume of 80 L, and a second system that was a series three-reactor system. Mass balances to describe the substrate utilisation rate and the microbial growth together with the kinetic models of Michaelis–Menten and Chen–Hashimoto were used to describe the process. While the first system was overloaded under the loading conditions tested, the performance of the second system could be described by the below cited kinetic models at hydraulic residence times higher than 2.3–2.4 days.

Aerobic purification of dairy wastewater in continuous regimePart I: Analysis of the biodegradation process in two reactor configurations

Abstract The removal of organics and nitrogen species is postulated in many water quality regulations. In the dairy industry, milk, water and detergents are discharged to wastewater treatment plants as a result of routine operations. In general, the treatment applied has been aerobic. This work is focused on the study of the biodegradation of a synthetic dairy wastewater (4000 mg/L COD, COD/TKN ratio of 4 and pH around 11.5) in continuous regime. Two different reactor systems thermostated at 30 °C were used. The first system was a single reactor with a working volume of 80 L. The second one was a three-stage reactor cascade with a total working volume of 30 L. In general, high organic matter removals (exceeding 96.8%) were achieved with the two systems. However, the performance of the systems showed much variability in relation to the biomass settling properties, resistance to filtration and tendency to produce viscous bulking and foaming phenomena associated with the specific characteristics of the wastewater and operational conditions.

Aerobic purification of dairy wastewater in continuous regime: Part I: Analysis of the biodegradation process in two reactor configurations

The removal of organics and nitrogen species is postulated in many water quality regulations. In the dairy industry, milk, water and detergents are discharged to wastewater treatment plants as a result of routine operations. In general, the treatment applied has been aerobic. This work is focused on the study of the biodegradation of a synthetic dairy wastewater (4000 mg/L COD, COD/TKN ratio of 4 and pH around 11.5) in continuous regime. Two different reactor systems thermostated at 30 °C were used. The first system was a single reactor with a working volume of 80 L. The second one was a three-stage reactor cascade with a total working volume of 30 L. In general, high organic matter removals (exceeding 96.8%) were achieved with the two systems. However, the performance of the systems showed much variability in relation to the biomass settling properties, resistance to filtration and tendency to produce viscous bulking and foaming phenomena associated with the specific characteristics of the wastewater and operational conditions.

Aerobic purification of dairy wastewater in batch reactors: kinetic study of the influence of a pre-storage stage without aeration in the degradation of organic matter and ammonium consumption by nitrification

Six tests were carried out delaying the air intake in order to determine the influence of a pre-storage stage (between 0 and 48 h) in organic matter removal and ammonification processes. The kinetic model proposed by Quiroga & Sales predicted successfully the total and soluble COD profiles. The maximum consumption rates were reached in tests with 0 and 30 h without initial aeration. There was no advantage in pre-storage times higher than 30 h, as the non-biodegradable organic matter increased. Concerning ammonium consumption in nitrification, the adjustment to Quiroga & Sales model demonstrated kinetics with an order varying between zero and one. This change in the reaction order was associated to an inhibition due to free ammonia. The experimental data adapted themselves fairly well to the proposed kinetic model.

A novel lysine 2,3-aminomutase encoded by the yodO gene of Bacillus subtilis: characterization and the observation of organic radical intermediates

The yodO gene product of Bacillus subtilis has been cloned and overexpressed in Escherichia coli and purified. The nucleotide sequence encodes a protein of 471 amino acids with a calculated molecular mass of 54071 Da. The translated amino acid sequence is more than 60% identical to that of the lysine 2,3-aminomutase from Clostridium subterminale SB4. Analytical HPLC gel-permeation chromatography leads to an estimate of an over all molecular mass of 224000+/-21000 Da, which corresponds to a tetrameric protein. The purified protein contains iron, sulphide and pyridoxal 5'-phosphate (PLP) and displays an optical absorption band extending to 700 nm, suggesting the presence of an iron-sulphide cluster. After reductive incubation with L-cysteine anaerobically, the protein catalyses the transformation of L-lysine into beta-lysine in the presence of S-adenosylmethionine (AdoMet) and sodium dithionite. The K(m) value for L-lysine is estimated to be 8.0+/-2.2 mM. The iron-sulphur centre is stable in air,allowing aerobic purification. EPR spectroscopy at 10 K of the purified enzyme revealed an EPR signal similar to that of the [4Fe-4S](3+) cluster observed in the clostridial lysine 2, 3-aminomutase. Incubation with cysteine under anaerobic conditions converts the iron-sulphur centre into the EPR-silent [4Fe-4S](2+). Unlike the clostridial enzyme, the fully reduced [4Fe-4S](+) could not be characterized by further reduction with dithionite in the presence of AdoMet, although both dithionite and AdoMet were required to activate the enzyme. Upon addition of L-lysine, dithionite and AdoMet to the reduced enzyme and freezing the solution to 77 K, the EPR spectrum revealed the presence of an organic free-radical signal (g=2.0023), which displayed multiple hyperfine transitions very similar to the spectrum of the beta-lysine-related radical in the mechanism of the clostridial lysine 2,3-aminomutase. Experiments with isotopically substituted L-lysine and lysine analogues verified the association of spin density with the carbon skeleton of lysine. The data indicate that the protein encoded by the yodO gene of B. subtilis is a novel lysine 2,3-aminomutase. The E. coli homologue of clostridial lysine 2,3-aminomutase was also expressed in E. coli and purified. This protein contained ironand sulphide but not PLP, it did not display lysine 2,3-aminomutase activity, and addition of PLP did not induce 2,3-aminomutase activity.

Purification, characterization, and preliminary crystallographic study of copper-containing nitrous oxide reductase from Pseudomonas nautica 617.

The aerobic purification of Pseudomonas nautica 617 nitrous oxide reductase yielded two forms of the enzyme exhibiting different chromatographic behaviors. The protein contains six copper atoms per monomer, arranged in two centers named Cu(A) and Cu(Z). Cu(Z) could be neither oxidized nor further reduced under our experimental conditions, and exhibits a 4-line EPR spectrum (g(x)=2.015, A(x)=1.5 mT, g(y)=2.071, A(y)=2 mT, g(z)=2.138, A(z)=7 mT) and a strong absorption at approximately 640 nm. Cu(A) can be stabilized in a reduced EPR-silent state and in an oxidized state with a typical 7-line EPR spectrum (g(x)=g(y)= 2.021, A(x) = A(y)=0 mT, g(z) = 2.178, A(z)= 4 mT) and absorption bands at 480, 540, and approximately 800 nm. The difference between the two purified forms of nitrous oxide reductase is interpreted as a difference in the oxidation state of the Cu(A) center. In form A, Cu(A) is predominantly oxidized (S = (1)/(2), Cu(1.5+)-Cu(1.5+)), while in form B it is mostly in the one-electron reduced state (S = 0, Cu(1+)-Cu(1+)). In both forms, Cu(Z) remains reduced (S = 1/2). Complete crystallographic data at 2.4 A indicate that Cu(A) is a binuclear site (similar to the site found in cytochrome c oxidase) and Cu(Z) is a novel tetracopper cluster [Brown, K., et al. (2000) Nat. Struct. Biol. (in press)]. The complete amino acid sequence of the enzyme was determined and comparisons made with sequences of other nitrous oxide reductases, emphasizing the coordination of the centers. A 10.3 kDa peptide copurified with both forms of nitrous oxide reductase shows strong homology with proteins of the heat-shock GroES chaperonin family.

Physiological responses of Tetrahymena pyriformis to copper, zinc, cycloheximide and Triton X-100.

Protozoa, and particularly ciliates, are essential in aerobic purification processes of wastewaters and have proved to be very sensitive to environmental changes. The physiological response of the ciliate Tetrahymena pyriformis was assessed in terms of mortality, growth and grazing capacity after exposure to four toxicants: copper, zinc, cycloheximide and Triton X-100. In the ranges of concentrations used, mortality, inhibition of growth and inhibition of grazing were observed with all toxicants employed, but in different ways. Copper and zinc showed lower toxicity than observed in other studies with protozoa, though some of the present results are in accordance with those reported by other authors. This supports the importance of the organism tested and the experimental conditions of the bioassays.

Physiological responses of Tetrahymena pyriformis to copper, zinc, cycloheximide and Triton X-100

Protozoa, and particularly ciliates, are essential in aerobic purification processes of wastewaters and have proved to be very sensitive to environmental changes. The physiological response of the ciliate Tetrahymena pyriformis was assessed in terms of mortality, growth and grazing capacity after exposure to four toxicants: copper, zinc, cycloheximide and Triton X-100. In the ranges of concentrations used, mortality, inhibition of growth and inhibition of grazing were observed with all toxicants employed, but in different ways. Copper and zinc showed lower toxicity than observed in other studies with protozoa, though some of the present results are in accordance with those reported by other authors. This supports the importance of the organism tested and the experimental conditions of the bioassays.

Aerobic purification of dairy wastewater in continuous regime; reactor with support

Continuous-flow experiments have been carried out to achieve effluents with low COD and a minimum ammonium–nitrogen concentration. The system was aerated by air injection. The air passing through bottom-resting perforated tubes by a plastic mesh. Mixtures of milk and water, pH 11 units and containing 3500 mg COD/l (similar to dairy sewage) were fed into the reactor. The liquor temperature was near 30°C. A mixed culture of isolates from dairy effluents, adapted at 30°C for 19 days and mixed with sludge from a domestic wastewater plant, was used as an inoculum. The inlet flows were 8, 10, and 12.6 l/d. Experiments were continued to the pseudostationary state. The pH generally became stabilized around 8.5. With increasing flow, the average COD values and the final ammonium–nitrogen concentrations decreased until a certain flow value, at which they were almost stable. The same behaviour was seen with the concentrations of nitrate and nitrite–nitrogen, nitrification and denitrification phenomena taking place simultaneously. At the end of the experiments, the effluent was characterized by low COD and nutrients. The biomass content was 5.9 g N, 5.5 g P 2O 5, and 0.9 g K 2O for each 100 g biomass. This could be used as a source of nutrients after mineralization.