Influence of immobilization supports on the kinetic constants of anaerobic digestion of cheese whey

Three materials of different structure, sepiolite, saponite and bentonite, assayed as supports for the microorganisms effecting anaerobic digestion, were found to behave differently towards cheese whey wastewater from a kinetic point of view. Assuming the overall anaerobic digestion process to conform to first-order kinetics, the apparent kinetic constant for the digester including sepiolite as support was 2.44 days⁻¹, while that of the digester using the saponite and bentonite support was 2.20 days⁻¹ and 0.70 days⁻¹, respectively. Thus, the support used to immobilize the microorganisms that mediate the process had a marked influence on the constant. This was found significant at 95% confidence level. The yield coefficients, Y_p/s, were 0.336, 0.329 and 0.311 litres CH₄ STP/g COD for the sepiolite, saponite and bentonite supports, respectively.     

Cement for stabilisation of industrial residues containing heavy metals

A method aimed at decreasing the toxicity of heavy metals [namely, Zn(II) and Cr(III)] in real polluted residues by immobilisation has been developed. The residues were processed either with two cement-type stabilisers or lime. The cement-type stabilisers were Portland cement and Depocrete SM/2 at the self-generated pH (ca. 11) which afforded physical as well as chemical potential for the immobilisation of heavy metals. The other stabiliser, lime, reduced organic compounds, thus favouring the decrease of the chemical oxygen demand (COD) and endowing the residue with better mechanical properties for transport. After leaching the stabilised residues using the standard leaching test [Order 13/10/89, Boletín Oficial del Estado (BOE) 270 10/11/89], three ways for establishing the toxicity of the treated residues were used, namely: (1) the ecotoxicity test using Photobacterium phosphoreum (DIN 38 412); (2) determination of the concentration of heavy metals by atomic absorption spectrometry (AAS); (3) determination of the COD or oxygen required for complete chemical oxidation of a water sample. Portland cement (20%) blended with Depocrete SM/2 (3%) acted as an effective stabiliser for residues containing heavy metals as it increased the ecotoxicity index (EC50) by more than five times. Thus the heavy metal concentration in the leaching liquid was lowered to less than 0.1 mg l-1. The addition of 5% of lime afforded a residue easily transportable from the place of treatment to the landfill. The precision of the method was studied in terms of both repeatability and reproducibility. The values found with respect to EC50 and expressed as the relative standard deviation (RSD) were 1.6% and 5.1%, respectively.     

Production,Characterization and Bioemulsifying Activity of an Exopolysaccharide Produced by <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. Isolated from Freshwater

This study aimed to evaluate the emulsion stability of solutions containing exopolysaccharide and culture medium of a Sphingomonas sp. strain with various hydrophobic compounds. The exopolysaccharide characterized belongs to a sphingan group, however, not being a gellan gum as produced by certain Sphingomonas strains. In general, the emulsifying indexes found in this study were above 70% for gasoline, hexane, kerosene and used frying oil. Nonetheless, the best results were achieved in kerosene solutions, which showed an index of 80% after 24 h, remaining stable for more than 168 h in combinations with various EPS concentrations. Interestingly, diesel oil best results were singly achieved in solution pH of 11, showing an index of around 65%. Furthermore, hexane obtained an index of 100% after 24 h when culture medium was used. Thus, these findings highlight the use of EPS as a potential bioemulsifier agent to enhance hydrocarbon degradation and emulsification effects in environmental biotechnology.     

Effects of copper sulfate on growth and physiological responses of Limoniastrum monopetalum

A glasshouse study of the coastal shrub Limoniastrum monopetalum was carried out to evaluate its tolerance and capacity to accumulate copper. We investigate the effects of Cu from 0 to 60 mmol l^?1 on the growth, photosynthetic apparatus, and nutrient uptake of L. monopetalum, by measuring gas exchange, chlorophyll fluorescence parameters, photosynthetic pigments, and total copper, nitrogen, phosphorus, sulfur, calcium, and magnesium content in the plant tissues. Although L. monopetalum did not survive at 60 mmol l^?1 Cu, the species demonstrated a high tolerance to Cu-induced stress, since all plants survived external Cu concentrations of up to 35 mmol l^?1 and displayed similar growth in the Cu-enriched medium as in the control treatment of up to the external level of 15 mmol Cu l^?1 (1,000 mg Cu l^?1). The reduced growth registered in plants exposed to 35 mmol Cu l^?1 can be attributed to reduced photosynthetic carbon assimilation associated with the adverse effect of the metal on the photochemical apparatus and a reduction in the absorption of essential nutrients. Copper tolerance was associated with the capacity of the plant to accumulate the metal in its roots and effectively prevent its translocation to photosynthetic tissues. L. monopetalum has the characteristics of a Cu-excluder plant and could be used in the revegetation of Cu-contaminated soils.     

Causes and consequences of salt-marsh erosion in an Atlantic estuary in SW Spain

This study reports on the quantification of horizontal erosion by undermining of slopes in the atlantic mesotidal salt marshes of Odiel, SW Spain, and analyses its causes and consequences. Horizontal erosion has produced considerable losses of salt marsh area, including zones of mature salt marsh. Human pressure, such as from water-borne traffic or the exploitation of the slopes for the capture of bait, increases the natural erosion processes. The role of vegetation in protecting the slopes against erosion is studied. Channel banks covered with plants, many of which belong to species with long-living, above-ground creeping stems, were less eroded than those without vegetation cover. The enormous volume of sediments moved (ca. 7000m³ in one year) could contribute to the silting-up of the navigable channels of the estuary, so that continual dredging is necessary to allow access to shipping. These sediments are highly contaminated, and dredging exposes them more directly to the trophic network of the estuary. There is a considerable loss of natural resources. Finally, the integrated management of this coastal ecosystem is discussed.     

Investigation on the role of graphene-based composites for in photocatalytic degradation of phenol-based compounds in wastewater: a review

Environmental Science and Pollution Research - The ineptitude of conventional water management systems to eradicate noxious compounds leads to the development of advanced treatment systems. The...     

Application of polysaccharide-based biopolymers as supports in photocatalytic treatment of water and wastewater: a review

Environmental Chemistry Letters - Rising health issues of Worldwide pollution by fossil fuel products are Fostering the development of safer materials such as biopolymers in many sectors such as...