The capacity of the photo electro-Fenton (PEF) process to degrade a mixture of seven polychlorinated biphenyl (PCB) congeners was studied. Boron-doped diamond (BDD) sheets were used as anode and cathode in the experimental electrolytic cell that contained Na₂SO₄ 0.05 M at pH 3 as supporting electrolyte for the electro generation of H₂O₂ at the cathode. The effects of UV light intensity (254 and 365 nm), current density (8, 16 and 24 mA cm⁻²) and ferrous ion dosage (0.1, 0.2 and 0.3 mM) on PCB (C₀ = 50 μg L⁻¹) degradation were evaluated. The highest level of PCB degradation (97%) was achieved with 16 mA cm⁻² of current density, 0.1 mM of ferrous ion and UV light at 365 nm as irradiation source after 6 h of reaction. PCB28, PCB52 and PCB101 were not detected after 0.5, 1.5 and 3 h of reaction, respectively. The degradation of PCB138, PCB153, PCB180 and PCB209 was also high (>95%). The PEF system outperformed other oxidation processes (electro-Fenton, anodic oxidation, Fenton, photo-Fenton and UV photolysis) in terms of reaction rate and degradation efficiency. These results demonstrate for the first time the degradation of PCB209, the most highly chlorinated PCB congener, by an advanced electrochemical oxidation process.

This paper proposes a solution to the current problems of Mexico City (Ciudad de México) with respect to construction and demolition waste, through a spatial analysis to locate a waste treatment and disposal infrastructure. Two analysis methodologies, specifically the multi-criteria evaluation technique and network analysis, are used with the support of geographic information systems. The results of the multi-criteria evaluation technique indicate that the most suitable places for this infrastructure location are in the south and southeast of the study area, in the Tlalpan, Milpa Alta, Xochimilco and Cuajimalpa boroughs. The results of the network analysis technique indicate that four facilities strategically located in Miguel Hidalgo, Gustavo A. Madero, Tlahuac and Tlalpan boroughs would permit the provision of service to almost all waste generation points in the study area. Decision makers in Mexico City can use either of the two approaches. If the objective is to find the best location of a single place for the treatment or disposal of huge amounts of waste, the results obtained with the multi-criteria evaluation technique should be used. On the other hand, if waste treatment is favored over final disposal, decision makers should use the results of the network analysis technique.

In this paper, a proposal was presented to improve the MSW collection service in the municipality of Reforma, in Chiapas, Mexico. Specific field work was developed and various spatial analysis techniques were applied in the GIS environment. The application of a multivariate analysis technique (Grouping Analysis) allowed the study area to be clustered into three waste collection sectors with common characteristics, which were the basis for generating three collection route scenarios. Scenario 1 corresponds to the current situation, where 478 waste collection points are served, with an average travel distance of 60.30 km and a collection time of 8.00 h. Scenario 2 was generated through the “maximize coverage” algorithm and vehicle route modeling in ArcGis 10.8. In this scenario, 1220 waste collection points are served, with an average travel distance of 143.21 km and an average collection time of 12.38 h. Scenario 3 was created using the “minimize facilities” algorithm, as well as collection modeling in ArcGis 10.8. Using this algorithm, impedances (distances) were automatically minimized so that 697 waste collection points could be served, with an average travel distance of 100.00 km and an average collection time of 9.66 h. In terms of improvement, scenario 3 gives the best results, because it minimizes distances and average travel times.

This paper presents a technology based on the use of aged refuse that has proven to be highly effective in the treatment of low biodegradability leachates. The tests were developed using two filled bioreactors arranged in series and operated at steady state. The aged refuse used as filling material was extracted from a city located in the southeast of Mexico and characterized by particle size, humidity, volatile solids, and volumetric weight. On the other hand, bacterial characterization made it possible to identify the presence of species related to the degradation and mineralization of organic compounds, as well as to processes of nitrification or reduction of phosphates and Cr (VI). The bioreactor system was operated under four hydraulic loads (10, 20, 35, and 50 L/m³·d). Maximum removal efficiencies of 85, 86.1, 87.9, 98.6, 97.8, and 97.4% were achieved in COD, BOD₅, Color, TP, TN, and N-NH₃, respectively, complying with Mexican regulations (NOM-001-SEMARNAT-1996). The system also proved to be stable against shock loads, such as organic load fluctuations in the influent or pH variations. The results of this study show that, in countries such as Mexico, aged refuse extracted from landfills represents a promising option as a sustainable alternative for leachate treatment.

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).