Biological Chemical Methods Research Articles

Effect of Optimized Chitosan Coating Obtained by Lactic Fermentation Chemical Treatment of Shrimp Waste on the Post-Harvest Behavior of Fresh-Cut Papaya (Carica papaya L.)

Chitosan is a biopolymer obtained from shrimp waste mainly by a polluting chemical method. In this work, a less polluting biological-chemical method to obtain chitosan from this waste has been optimized; this method used a successive lactic fermentation and chemical process. Additionally, in this work, the effect of chitosan coating on the post-harvest behavior of fresh-cut papaya was studied as a practical application. A rotatable central composite design (CCRD) with two variables (fermentation time and total soluble solids of the fermentation medium) was used to optimize the chitosan extraction. The optimized conditions for chitosan extraction were 108 h and 8.74 °Brix. The optimized chitosan showed a high deacetylation degree of 83%, acceptable process yield of 2.03%, a low ash content of 0.23% and a molecular weight of 107.5 kDa. In addition, optimized chitosan decreased the loss of color and acidity, as well as the growth of microorganisms; it also increased the pH of minimally processed papaya slices without a statistically significant difference with that of commercial chitosan. Based on these results, optimized chitosan could be applied to other fruits as a coating to maintain their quality characteristics and inhibit microbial growth during the storage of fresh-cut fruits.

Responses of Different Submerged Macrophytes to the Application of Lanthanum-Modified Bentonite (LMB): A Mesocosm Study

Lanthanum-modified bentonite (LMB) has remarkable efficacy on eutrophication control, but the reduced bioavailable phosphorus and formed anaerobic horizon from LMB may be harmful to submerged macrophytes. We conducted this study to explore the influence of LMB on Hydrilla verticillata and Vallisneria natans in mixed-species plantings. The concentrations of TP, TDP, SRP, and TDN in the LMB treatments were lower than the Control, but the Chl a concentration in the HLMB treatment (850 g m−2) was higher than the Control by 63%. There were no differences of V. natans growth among the treatments. For H. verticillata, its biomass, RGR, height, branch number, root number, and length in the LLMB treatment (425 g m−2) were lower than the Control by 48%, 22%, 13%, 34%, 33%, and 8%, respectively. In addition, the biomass of H. verticillata was 62%, the RGR was 32%, the height was 19%, the branch number was 52%, the root length was 40%, and the root number was 54% lower in the HLMB treatment than those in the Control. In summary, LMB had negative effects on submerged macrophytes with underdeveloped roots. Submerged macrophytes with more developed roots are preferred when using combined biological–chemical methods for water restoration.

Metals recovery from acid mine drainage

The objectives of the present work give the results view of some physicochemical, chemical and biological-chemical methods for the heavy metals removal from Acid Mine Drainage (AMD). The background of the studied physicochemical methods was the adsorption by turf, chemical methods the heavy metals precipitation by the neutralization with NaOH. The principles of the biological-chemical methods were the bioprecipitation by the applications of sulphate-reducing bacteria (SRB), the sorption by the bacterially produced iron sulphides and sorption by brown coal bio-modified by micromycetes.

Combination of Chemical and Biological-Chemical Methods for Elimination of Metals from Acid Mine Drainage

Each acid mine drainage has a specific composition, but always contains sulphuric acid, dissolved heavy metals, sulphates, iron precipitates and their pH can be very low. The elimination of metals form the acid mine drainage is a severe environmental problem andhas been a long-standing major concern to scientists, engineers, industry and governments. Various methods are used for the metalsremoval from waters, but any of them have been applied under commercial-scale conditions. Mostly studied are chemical and biological-chemical methods. Main aim of the paper was to interpret the combination of chemical and biological-chemical methods for theheavy metals elimination from the synthetic solution of acid mine drainage, coming from the zinc mine located in Tùnel Kingsmilloutlet of the Rio Yaulì (district of Yauli – Perù). The metals selective precipitation as hydroxides (chemical method) and sulphides(biological-chemical method) at the various values of pH acid mine drainage is the fundamental of the examined process. For thehydrogen sulphide production the sulphate-reducing bacteria of genus Desulfovibrio was used. The selective sequential precipitationprocess reaches the selective precipitation of chosen metals with 97–99% efficiency – Fe, As, Al and Mn in the form of metal hydroxides,Cu and Zn as metal sulphides

Removal of Contaminants from Water by Bacterial Activity

High concentration of sulphates and metals in waters is often as a consequence of anthropogenic activity and industry. The principlesof the biological-chemical methods for pollution removal include various processes. The most widely metabolic pathway of sulphate-reducing bacteria - overall dissimilatory reduction - is the complete reduction of sulphate to hydrogen sulphide. Two major metabolicgroups are known, depending on whether or not they can oxidize acetate. One group utilizes lactate, fumarate, propionate, butyrate,pyruvate, and aromatic compounds, which they typically oxidize to acetate, while the other group oxidizes acetate to CO₂ and H₂O.Sulphate is reduced to H₂S through a series of intermediate reactions. The end product of this reaction, hydrogen sulphide, can reactwith metal ions to form insoluble metal sulphides or reduce soluble toxic metals, often to less toxic or less soluble forms. This way,sulphate-reducing bacteria are utilizable in bio-elimination of sulphate and metal from water.

Efficient phosphate removal by biological corrosion method

Water quality deterioration in water bodies is directly related to the development of anthropogenic eutrophication processes. To resolve this complex issue, one needs to minimize biogenic discharge of nitrogen and phosphorus compounds into the water bodies. The article presents relevant information in the field of phosphate-removing wastewater treatment, describes the most effective biological and biological-chemical methods of phosphate-removing wastewater treatment. The article presents the results of research on phosphate-removing wastewater treatment methods using iron-bearing reinforced feed material (biological corrosion method, biogalvanic method). The placement of reinforced feed material in a standard air tank allowed to significantly increase the efficiency of organic contamination-removing biological wastewater treatment. The biological process activation ratio due to the use of reinforced feed material amounted to 1.78. The placement of reinforced feed material in the bioreactor, which operates without activated sludge return, allowed to achieve complete phosphate removal from the waste water. The maximum effect of phosphate removal (99 %) with the concentration of phosphate in treated water below the detection limit was achieved after 4 to 6 hours of wastewater treatment in the bioreactor, with the concentration of organic contamination in the incoming wastewater from 150 to 300 mgBOD/L and the concentration of phosphate upstream of the bioreactor from 4 to 6 mg PO4/L. Based on the research carried out, it was concluded that the use of biological corrosion method allows to achieve high efficiency of phosphate removal, as well as to intensify the biological process of organic contamination removal from waste water.

COD removal from biologically stabilized landfill leachate using Advanced Oxidation Processes (AOPs)

The removal of soluble organic matter from mature landfill leachate by means of biological, chemical, and combined biological-chemical methods was investigated in this study. Aerobic sequencing batch reactor (SBR) with activated sludge was used as the biological treatment to remove ammonium. The chemical treatments included ozone (O3), ozone + hydrogen peroxide (O3 + H2O2), Fenton’s reagents (H2O2 + Fe2+), and ozone + Fenton’s reagents (O3 + H2O2 + Fe2+). Results indicated that the SBR achieved approximately 25% Chemical Oxygen Demand (COD) removal with an initial COD of 1276 mg/L. Ozonation of raw leachate achieved 16% COD removal after 240 min of treatment while O3 + H2O2 achieved 33% COD removal of raw leachate with 900 mg/L H2O2 in 120 min. Moreover, Fenton’s process also achieved 33% COD removal from raw leachate. Results suggest that the biological treatment followed by chemical treatments had the most efficient COD removal. After biological stabilization, ozonation removed 52% of the COD within 240 min. The Fenton’s process achieved 67% COD removal using equal doses of H2O2 and Fe2+. However, Fenton’s reagents in conjunction with O3 removed 69% and 72% COD in 120 min and 240 min, respectively. The dosage test also revealed that the 2:1 ratio of H2O2 and Fe2+ had the best COD removal. Therefore, these results indicate that the combination of biological and post-chemical treatment methods effectively remove organic pollutants from mature landfill leachate.

Post-harvest Preservation of Cactus Fruits Produced in Semidesertic Areas of Oaxaca by Biopolymer Coatings

AbstractThe pitaya (Stenocereus pruinosus) and sweet xoconostle (Stenocereus stellatus) are Cactaceae fruits with local distribution, due to their perishability and microbial decay with postharvest life from 3 to 5 days. Thus, the objective of this research was to apply chitosan based coatings: commercial chitosan (CQ), chitosan produced by biological-chemical method (Q) and Q grafted to hydroxypropylmethylcellulose in an emulsion with entrapment neem oil (N) (NMQ-g-H). Application in field was carried out in Santa Gertrudis Cosoltepec, in the Mixteca area of Oaxaca, which is a deforested region with eroded soil. QC, Q and NMQ-g-H at 10±5°C and 75±5% relative humidity extended the postharvest life of fruits by 15 days. Q was obtained by thermochemical heterogeneous deacetylation from chitin extracted from a lactic fermentation of shrimp wastes, therefore there is an additional benefit, due to the decrease of wastes produced in coastal area by obtaining value-added products that served as coatings for prolong postharvest life of fruits produced in Mixteca Region of Oaxaca.

Study of Precipitating Methods for Elimination of Heavy Metals from Acid Mine Drainage

Abstract The submitted paper deals with the study of combination of chemical and biological-chemical methods for the heavy metals elimination from the acid mine drainage. The experiments were carried out at the laboratory scale using a synthetic solution with similar properties to the real sample of acid mine drainage, originating from the zinc mine located in Tùnel Kingsmill outflow of the Rio Yaulì (district of Yauli - Perù). The successive repetition of the metal precipitations as hydroxides (chemical method) and sulphides (biological-chemical method) at the various acid mine drainage pH was the basis of the examined processes. For the hydrogen sulphide production the sulphate-reducing bacteria of genus Desulfovibrio were used. Results confirmed the precipitation of Fe, As, Al and Mn in the hydroxide form; Cu and Zn in the form of sulphides. For the selective removal of Cu, Zn, Al and Mn the excellent results were received. Selective precipitation of Fe and As was not so successful since the co-precipitation of Fe and As was later determined as a main mechanism of the precipitate forming.

Application of physical–chemical and biological–chemical methods for heavy metals removal from acid mine drainage

Acid mine drainage (AMD) represents a serious environmental problem related to sulfide minerals and coal mining. High content of toxic metals and high acidity in AMD adversely affects surface water, groundwater and soil. The abandoned mine of the Smolník deposit in Slovakia is a typical example in this respect. The quality of AMD needs to be monitored and suitable treatment methods need to be developed.The aim of this paper was to demonstrate the technical feasibility of heavy metals removal from AMD using physical–chemical and biological–chemical methods. The base of the physical–chemical method was electrowinning. The principle of the biological–chemical method was the selective sequential precipitation (SSP) of metals with the application of hydrogen sulfide produced by sulfate-reducing bacteria and sodium hydroxide solution. Both the electrowinning and SSP processes decrease the content of heavy metals in AMD. The pre-treatment of AMD by chemical iron–aluminum precipitation (in the case of electrowinning tests) and chemical iron precipitation (in the case of SSP tests) improved the selectivity of the processes. A further aim of the work was the improvement of the SSP.During the electrochemical experiments, 99% Zn removal – under metallic form – and 94% Mn removal – under MnO2 form – both with a high degree of purity, were achieved. The SSP process reached the selective precipitation of chosen metals with 99% efficiency – Fe, Al and Mn in the form of metal hydroxides, Cu and Zn as metal sulfides. The results achieved may be used for designing a process appropriate for the selective recovery of metals from the AMD discharged from the Smolník deposit.

Application of physical-chemical and biological-chemical methods for heavy metals removal from acid mine drainage

Abstract Acid mine drainage (AMD) represents a serious environmental problem related to sulfide minerals and coal mining. High content of toxic metals and high acidity in AMD adversely affects surface water, groundwater and soil. The abandoned mine of the Smolnik deposit in Slovakia is a typical example in this respect. The quality of AMD needs to be monitored and suitable treatment methods need to be developed. The aim of this paper was to demonstrate the technical feasibility of heavy metals removal from AMD using physical–chemical and biological–chemical methods. The base of the physical–chemical method was electrowinning. The principle of the biological–chemical method was the selective sequential precipitation (SSP) of metals with the application of hydrogen sulfide produced by sulfate-reducing bacteria and sodium hydroxide solution. Both the electrowinning and SSP processes decrease the content of heavy metals in AMD. The pre-treatment of AMD by chemical iron–aluminum precipitation (in the case of electrowinning tests) and chemical iron precipitation (in the case of SSP tests) improved the selectivity of the processes. A further aim of the work was the improvement of the SSP. During the electrochemical experiments, 99% Zn removal – under metallic form – and 94% Mn removal – under MnO 2 form – both with a high degree of purity, were achieved. The SSP process reached the selective precipitation of chosen metals with 99% efficiency – Fe, Al and Mn in the form of metal hydroxides, Cu and Zn as metal sulfides. The results achieved may be used for designing a process appropriate for the selective recovery of metals from the AMD discharged from the Smolnik deposit.

Sorption of Copper Ions by Biogenic Iron Sulphides

Biogenic iron sulphides are excellent adsorbents for various heavy metals ions. Consequently, they have practical application for the elimination of heavy metals from waste waters. One of the principles for the iron sulphides preparation is the application of sulphatereducing bacteria. This biological-chemical method is based on the ability of these bacteria to reduce sulphates to hydrogen sulphide, which binds with the ferrous cations to form insoluble precipitates – iron sulphides. Under certain bacterial growth conditions biogenic iron sulphides can be magnetic. The aim of this work is to study the possibility of using SRB for the preparation of iron sulphides, which were used subsequently in the framework of sorption tests to eliminate copper ions from model solutions.

Remediation of Acid Mine Drainage by Means of Biological and Chemical Methods

The formation and treatment of acid mine drainage is the biggest environmental problems relating to mining and processing activities in the worldwide. Various methods are used for the sulphates and heavy metals removal from acid mine drainage in the world, but any of them is universal. Main aim of the paper is the interpretation of chemical and biological-chemical methods for the metals and sulphates removal from acid mine drainage sample. The chemical method is based on the sulphates precipitation by the sodium aluminate in combination with the calcium hydrate. The biological-chemical method is based on the application of sulphate-reducing bacteria (SRB). A sample of acid mine drainage from the abandoned and flooded deposit of Smolník located in Slovak republic was used in this study.