Recovery of Mixtures of Construction Waste, PET and Sugarcane Bagasse for the Manufacture of Partition Blocks.

The building industry generates millions of tons of construction and demolition waste annually (12 million tons/year are generated in Mexico, of which only 4% is reused or recycled). Concomitantly, the demand for goods and services by the building industry causes significant environmental impacts. On the other hand, plastic waste is also difficult to assimilate into the environment in the short term, and its recovery is of special interest. Therefore, this research focuses on the feasibility of the manufacture of Partition Blocks (essential building element) through the combination of construction and demolition waste (CDW), polyethylene terephthalate (PET) plastic flakes, dust from tire shredding, and residue from the sugar industry (bagasse). The results of this study show that the Partition Blocks made with CDW and PET reach an average compressive strength of 115.003 kgf/cm2 (11.278 MPa) (suitable for structural use according to Mexican regulations); the use of lime enhances the consistency of the mixture of CDW and PET (increases its cohesion and homogeneity); and finally, these Partition Blocks have a cost comparable to the current conventional Partition Blocks made with virgin material, thus, conferring them validity as a feasible recycling option for these residues.

Leachate treatment: comparison of a bio-coagulant (Opuntia ficus mucilage) and conventional coagulants using multi-criteria decision analysis.

The main aim of this research was to compare a bio-coagulant, organic coagulant, and a conventional coagulant applied to the treatment of leachates. Coagulant options were Stage 1 FeCl3, Stage 2 Polyamine, and Stage 3 Opuntia ficus mucilage (OFM). Optimal conditions for maximum chemical oxygen demand (COD) removal were determined by experimental data and Response Surface Methodology. The application of Multiple Criteria Decision Analysis using Multi-Criteria Matrix (MCM) was explored by evaluating the Coagulation-Flocculation processes. Maximum COD removal (%) and the best MCM scores (on a scale from 0 to 100) were: Stage 1: 69.2±0.9 and 48.50, Stage 2: 37.8±1.1 and 79.0, and Stage 3: 71.1±1.7, and 81.5. Maximum COD removal using FeCl3 and OFM was not statistically different (p 0.15 < 0.05). OFM extraction process was evaluated (yield 0.70 ± 1.17%, carbohydrate content 32.6 ± 1.18%). MCM allows the evaluation of additional technical aspects, besides oxygen COD removal, as well as economic aspects, permitting a more comprehensive analysis. Significant COD removals indicate that the use of OFM as a coagulant in the treatment of stabilized leachate was effective. Opuntia ficus cladodes, a residue, were used to treat another residue (leachates).

GIS-based approach to zoning the risk associated with municipal solid waste management: application to regional scale.

The objective of this paper is to offer an approach to assess the risk associated with Municipal Solid Wastes, in a geospatial context. Initially, a risk index including hazard, vulnerability and other important variables was built. The built model is based on multi-criteria evaluation techniques and geographic information systems. Subsequently, the constructed index was used to model possible damage in various municipalities of the state of Chiapas, Mexico. The results indicate that the highest levels of risk are found in places with unfavorable conditions, such as high rates of waste generation, low waste collection coverage, steep slopes, etc. that cover 6.22% of the study area. The areas with high risk level are mainly found in the southeast of the municipalities of Villa Corzo and Villaflores, and cover 27.06% of the study area. The places of low and very low risk levels are concentrated in the center and northeast of the study area, in the municipalities of Suchiapa, Chiapa de Corzo and Acala, and cover 38.6% of the area. At the municipal level, Berriozábal, Villaflores and Villa Corzo have the highest levels of risk in most of their territory; the high levels of risk presented in Berriozábal are due to the limited territorial area that it occupies in the study area. In Villaflores and Villa Corzo, the high levels of risk are due to the high population dispersion. A large part of Tuxtla Gutiérrez territory presents low and medium risk levels, especially within the population settlement. The peripheral areas show the highest levels of risk, because the waste collection service is not provided very often. Finally, the Cohen's kappa statistic used to validate the precision of the model gave a value of 0.34, which means that the spatial model can be considered acceptable despite its low value. Although this work is only a general approach to spatial risk modeling at a regional scale, it provides interesting information. Moreover, it adds to the few efforts that exist in the literature to model the risk associated with wastes.

Analysis of the Physicochemical and Mineralogical Properties of the Materials Used in the Preparation of Recoblocks.

The construction sector generates 14,000 t/d of construction waste in Mexico City, these materials do not have real applications and end up accumulating in landfills. This work, the objective of which was to analyze the physicochemical and mineralogical properties of soil and construction waste used in the manufacture of Recoblocks, is divided in five stages. First, the excavation material was submitted to field tests. Physical and chemical tests were then carried out on construction waste. Subsequently, the optimal mixture for making Recoblocks was determined. Next, Recoblocks were evaluated and compared with blocks made with water only, without mucilage of Opuntia ficus, and finally a feasibility study was performed. The X-ray diffraction study showed the presence of plagioclase, minerals that improve bending resistance, hardness, durability, as well as resistance to stress in a material. Compared to blocks manufactured without mucilage, the use of Opuntia ficus mucilage increased the compressive strength of the material by 59%, as well as the erodibility. Recoblocks are an environmentally friendly option because they are based on recycled materials, dried under the sun, which eliminates the use of brick oven. The production cost per unit is just USD 0.19, so it is a viable option as a building material.

Degradation of gestodene (GES)-17α-ethinylestradiol (EE2) mixture by electrochemical oxidation.

Evidence of the negative effects of several pharmaceutical molecules, such as hormones and steroids, on the environment can be observed throughout the world. This paper presents the results of the anodic oxidation of the mixture of gestodene steroid hormones and 17 α-ethinylestradiol present in aqueous medium. The tests were conducted in an undivided cell containing a working volume of 50 mL, using a Na2SO4 solution as support electrolyte and boron-doped diamond electrodes. The experiments were adjusted to the structure of a 33 factorial design. The evaluated factors were: support electrolyte concentration (0.02, 0.05, and 0.10 M), pH of the reaction media (2, 3, and 4), and current density (16, 32, and 48 mA cm-2). Under the optimum conditions (0.02 M Na2SO4, pH 4, and current density of 32 mA cm-2), the degradation of at least 93% of the initial concentration of gestodene and 17α-ethinylestradiol was reached in a reaction time of 5 and 10 min, respectively. The complete degradation of both molecules required 15 min of reaction. Under these conditions, the degradation profile of the pharmaceutical mixture as each one of the active ingredients, followed a pseudo-first order kinetic behavior (kmix = 0.0321, kGES = 0.4206, and kEE2 = 0.3209 min-1).

Application of the Fenton process in the elimination of helminth eggs.

This study relates to a method for evaluating the degradation efficiency of Ascaris lumbricoides eggs through a Fenton reaction, using hydrogen peroxide (H2O2) at 100, 250, and 500 mg/L, ferrous sulfate (FeSO4) at 458 mg/L Fe(2+) and pH values of 3, 4.5, and 6. The experiments were conducted according to a 3(2) experimental design, with 1:1, 3:1, and 5:1 (H2O2/Fe(2+)) molar ratios. The oxidation and flocculation stages were performed at 130 rpm during 2 hours and at 25-30 rpm during 20 min, respectively. As a result of the Fenton reaction, an average of 91.2% Ascaris lumbricoides egg degradation was achieved at pH 6 using a 500 mg/L dose of H2O2 and a 3:1 (H2O2/Fe(2+)) molar ratio. Thus, this process is an alternative for eliminating parasites that are resistant to conventional disinfection processes and significantly reduces the human health hazard they represent.

Estimación de la tasa máxima de crecimiento de un cultivo mixto de microalgas de una zona tropical, sujeto a variaciones de luz

Dentro de los parámetros que gobiernan la dinámica de los procesos que determinan la calidad del agua, destaca la tasa de crecimiento del fitoplancton, que depende de factores ambientales como la intensidad de la luz, la temperatura y los nutrientes. En este trabajo se presentan los resultados de la experimentacion realizada con un cultivo mixto de microalgas que fue sometido a variaciones de luz en el ambito de 53.75 a 26.875 uE m2 s1 (equivalentes a 8.000 y 4.000 lux, respectivamente), y de temperatura en el ambito de 20 a 30 grados. Los resultados indican que a una intensidad de luz de 53.75 uE m2 s1(intensidad de saturación), se obtuvo la tasa máxima de crecimiento