The effectiveness of the stabilization/solidification process on the leachability and toxicity of the tannery sludge chromium

[EN] A stabilization/solidification (S/S) process by using cement was applied to tannery sludge in order to find a safer way of landfilling this waste. The effects of three parameters on the process effectiveness were analysed in terms of leachate toxicity and chromium retention (%). The parameters studied were the relative amount of added water (30e50 wt.%), cement (10e60 wt.% in the solid components), and the use of three different types of cement (clinker with additions of limestone, with additions of limestone and fly ashes, and with additions of pozzolans). Statistical analysis performed by variance analysis and categorical multifactorial tests reveals that all the studied parameters significantly influence the effectiveness of the process. Results showed that chromium retention decreases as the relative amount of cement and water increases, probably due to additional chromium provided by cement and increased in the porosity of the mixtures. Leachate toxicity showed the same minimum value for mixtures with 30% or 40% cement, depending on the type of cement, showing that clinker is the main material responsible for the process effectiveness, and additives (pozzolans or fly ashes) do not improve it. The volume increase is lower as less sludge is replaced by cement and the relative amount of water decreases, and for the cement without additions of fly ashes or pozzolans. Therefore, the latter seems to be the most appropriate cement in spite of being more expensive. This is due to the fact that the minimum toxicity value is achieved with a lower amount of cement; and moreover, the volume increase in the mixtures is lower, minimizing the disposal cost to a landfill.The authors wish to express their gratitude to the tannery facility INCUSA, S.A., to the cement facility CEMEX ESPAÑA, S.A. and to Carles Martínez for his translation assistance.Montañés Sanjuan, MT.; Sánchez Tovar, R.; Roux, MSB. (2014). The effectiveness of the stabilization/solidification process on the leachability and toxicity of the tannery sludge chromium. Journal of Environmental Management. 143:71-79. doi:10.1016/j.jenvman.2014.04.026S717914

Mehka optimizacija za izbiro portfelja na osnovi vstavljenega (vgrajenega) izreka v mehko normiran linearni prostor

Background: This paper generalizes the results of Embedding problem of Fuzzy Number Space and its extension into a Fuzzy Banach Space C(Ω) × C(Ω), where C(Ω) is the set of all real-valued continuous functions on an open set Ω. Objectives: The main idea behind our approach consists of taking advantage of interplays between fuzzy normed spaces and normed spaces in a way to get an equivalent stochastic program. This helps avoiding pitfalls due to severe oversimplification of the reality. Method: The embedding theorem shows that the set of all fuzzy numbers can be embedded into a Fuzzy Banach space. Inspired by this embedding theorem, we propose a solution concept of fuzzy optimization problem which is obtained by applying the embedding function to the original fuzzy optimization problem. Results: The proposed method is used to extend the classical Mean-Variance portfolio selection model into Mean Variance-Skewness model in fuzzy environment under the criteria on short and long term returns, liquidity and dividends. Conclusion: A fuzzy optimization problem can be transformed into a multiobjective optimization problem which can be solved by using interactive fuzzy decision making procedure. Investor preferences determine the optimal multiobjective solution according to alternative scenarios.Ozadje: Članek posploši rezultate problema vgrajenega mehkega številskega prostora in njegovih razširitev v mehki Banachov prostor, kjer je C(Ω) množica vseh realnih kontinuirnih funkcij na odprti množici Ω. Cilji: Poglavitna ideja v ozadju našega pristopa je izrabiti prednost medsebojnega vpliva mehkih normiranih prostorov in normiranih prostorov na način, da dobimo ekvivalenten stohastičen program. Tako se laže izognemo tveganju zaradi prevelikega poenostavljanja realnosti. Metoda: Vgrajeni izrek pokaže, da množico vseh mehkih števil lahko vgradimo v mehki Banach-ov prostor. Izhajajoč iz tega izreka predlagamo rešitev koncepta mehkega optimizacijske problema, ki se pojavi, kadar uporabimo vgrajeno funkcijo na prvotnem mehkem optimizacijskem problemu. Rezultati: Predlagano metodo smo uporabili, da smo razširili klasičen model (srednja varianca) za izbiro portfeja na model v mehkem okolju (srednja varianca z nesimetrično porazdelitvijo) ob kriteriju dolgoročnih in kratkoročnih dobičkov na vlaganja, likvidnosti in dividend. Zaključek: Problem zabrisane optimizacije je mogoče pretvoriti v problem večkriterijske optimizacije, ki ga je mogoče rešiti z uporabo interaktivnega mehkega postopka odločanja. Investitorjeve preference določajo optimalno večkriterijsko rešitev glede na alternativne scenarije