Capdevielle A.,IRSTEA |
Sykorova E.,ICT Prague |
Beline F.,IRSTEA |
Environmental Technology (United Kingdom) | Year: 2014
An experimental design was set up to understand the influence of five process parameters on the kinetics of struvite precipitation in synthetic swine wastewaters. The responses studied were the kinetics of phosphorus (P) removal, the struvite precipitation rate and the dissolution rate of amorphous calcium phosphates (ACP). The kinetic study showed that the P-removal was complete in less than 1 h and was influenced positively by the added MgO. The precipitation of struvite with MgO was confirmed to follow a first-order kinetic. This study showed that ACP co-precipitated with struvite during the first 30 min. Afterwards, ACP dissolved to maintain the phosphates balance limiting the struvite growth. An initial Mg:Ca>1.5 induced a complete dissolution of ACP in 1 h. Another experiment was conducted and it validated the results of the statistical model. This experiment also determined that 7-10 h was the best time to recover large crystals. After 10 h, the crystals were broken by stirring. © 2013 Taylor & Francis.
Capdevielle A.,IRSTEA |
Capdevielle A.,European University of Brittany |
Sykorova E.,ICT Prague |
Biscans B.,CNRS Chemical Engineering Laboratory |
And 2 more authors.
Journal of Hazardous Materials | Year: 2013
A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P dissolution followed by the separation of particulate organic matter. The next two steps are firstly the precipitation of struvite crystals done by adding a crystallization reagent (magnesia) and secondly the filtration of the crystals. A design of experiments with five process parameters was set up to optimize the size of the struvite crystals in a synthetic swine wastewater. More than 90% of P was recovered as large crystals of struvite in optimal conditions which were: low Mg:Ca ratio (2.25:1), the leading parameter, high N:P ratio (3:1), moderate stirring rate (between 45 and 90. rpm) and low temperature (below 20 °C).These results were obtained despite the presence of a large amount of calcium and using a cheap reactant (MgO). The composition of the precipitates was identified by Raman analysis and solid dissolution. Results showed that amorphous calcium phosphate (ACP) co-precipitated with struvite and that carbonates were incorporated with solid fractions. © 2012 Elsevier B.V.
Geun Goo B.,Catholic University of Korea |
Baek G.,Catholic University of Korea |
Jin Choi D.,ICT Prague |
Il Park Y.,ICT Prague |
And 5 more authors.
Bioresource Technology | Year: 2013
Extracellular polysaccharide (EPS) was isolated from defatted micro-algae Dunaliela tertiolecta and defined as linear (1 → 4)-α-d-glucan based on monosaccharide composition, enzymatic and spectroscopic analyses. Optimization and characterization of acidic and enzymatic hydrolyses of EPS have been performed for its potential use as a renewable biorefinery material. The hydrolytic methods were improved to assess the effect of substrate specificity, reaction time, pH, ionic strength and temperature on efficiency of glucose production. EPS was effectively converted into glucose within one-step enzymatic or acidic hydrolysis under optimized conditions. Over 90% recovery of glucose was achieved for both hydrolytic approaches. High potential production of EPS and high yield conversion of this substrate to glucose may allow further exploration of microalga D. tertiolecta as a potential biomass producer for biotechnological and industrial exploitation of bioethanol. © 2012 Elsevier Ltd.
Koci V.,ICT Prague |
Mocova K.,ICT Prague |
Kulovana M.,T. G. Masaryk Water Research Institute |
Vosahlova S.,ENVISAN GEM
Environmental Science and Pollution Research | Year: 2010
Background, aim, and scope: The purpose of this study was to compare the suitability of different phytotoxicity testing procedures for the evaluation of toxicity associated with both soil contamination and solid wastes, both of which can be of environmental risk to plants. Ten different representative types of contaminated soils and solid waste samples were chosen from the Czech Republic. Materials and methods: Both solid-phase and aquatic toxicity testing procedures on mono- and dicotyledonous plants were performed using Lactuca sativa L., Sinapis alba L., Hordeum vulgare L., Triticum aestivum L., Lemna minor L., and the chlorococcal algae Desmodesmus subspicatus (syn. Scenedesmus subspicatus), strain Brinkmann 1953/SAG 86.81. An innovative classification scheme, using the intensity of toxic effects upon the plants, is presented in the study. Detailed chemical characterizations of both solid samples and their aquatic elutriates were carried out, using the appropriate ISO guidelines. In the solid samples, all the congeners of polychlorinated biphenyls were analyzed, together with 16 U. S. EPA polyaromatic hydrocarbons, the aggregate of C10-C40 hydrocarbons, total organic carbon, extractable organic halogens, as well as the majority of the environmentally toxic metals. In the aquatic elutriates, parameters analyzed were pH, conductivity, dissolved organic content, phenol index, main anions, and the majority of the environmentally relevant metals. Results: Eight out of ten samples tested expressed phytotoxic properties on tested organisms. Only three of the samples were toxic to both aquatic and terrestrial organisms in the tests. This demonstrates how different substances present in different samples can express different types of toxic effects, resulting in the illogical substituting terrestrial bioassays with aquatic ones. Discussion: Based upon our experience, we propose the following battery of bioassays for use in the characterization of toxic properties of solid wastes and contaminated soils: Aquatic ecosystems were tested by the algae D. subspicatus and plant L. minor; and the terrestrial ecosystems were tested by the dicotyledonous L. sativa and monocotyledonous H. vulgare. This proposed new battery of bioassays for the detection of phytotoxicity of both solid wastes and contaminated soils has higher sensitivity (as well as greater ecological relevance) compared to the battery of bioassays currently used in the Czech Republic. Conclusions: The tests currently used for regulatory purposes in the Czech Republic are phytotoxicity tests of elutriates, using S. alba and D. subspicatus, which have been found insufficiently sensitive to the range of different pollutants present in contaminated soils and/or solid wastes. If only aquatic bioassays are used for the toxicity testing, it is possible that the toxic effects of substances (poorly or totally) insoluble in water might be underestimated. The new proposed system of toxicity classification has proven to be both practical and sensitive. Recommendations and perspectives: This recommended alternative battery of phytotoxicity tests includes both aquatic tests of waste elutriates (with the algae D. subspicatus along with the aquatic plant L. minor), in addition to tests of the terrestrial solid samples (with the dicotyledonous L. sativa and the monocotyledonous H. vulgare). This battery of bioassays is sufficiently sensitive, representing a majority of types of aquatic and terrestrial plants. © Springer-Verlag 2009.
Taubner T.,ICT Prague |
Copikova J.,ICT Prague |
Havelka P.,VUOS a.s. |
Synytsya A.,ICT Prague
Cellulose | Year: 2013
Amidated derivatives of monocarboxy cellulose (MCC), the product of cellulose oxidation, containing carboxyl groups only at C-6 position, were prepared and characterised. Two-step way of amidation was based on the esterification of C-6 carboxyls in MCC by reaction with methanol at 60 °C for 72 h and further amino-de-alkoxylation (aminolysis) of the obtained methyl ester with n-alkylamines, hydrazine and hydroxylamine in the N,N-dimethylformamide medium. Purity and substitution degree of the products were monitored by vibration spectroscopic methods (FTIR and FT Raman) and organic elemental analysis. Analytical methods confirmed the preparation of highly or moderately substituted N-alkylamides, hydrazide and hydroxamic acid of MCC. © 2013 Springer Science+Business Media Dordrecht.