This paper presents a global historical review of rainfall-runoff modeling, beginning with its inception in the mid-nineteenth century with the rational method and continuing with unit hydrograph theory, the use of computers, and finally the application of Kalman filters and artificial neural networks to achieve greater numerical precision in the design of hydraulic structures and flood forecasting. In developing countries, such as Mexico, the most commonly used models are: 1) those that are available for free and have open forums for users to ask and answer questions, 2) those with theoretical-practical strength, and 3) those with easily available input and output data to feed and calibrate the model. Trends in hydrologic modeling in Mexico include the implementation of distributed models, the upgrading of radars for rainfall prediction and the use of this prediction to feed models for improved early flood forecasting.

The corn processing industry has increased its product output, resulting in a considerable increase in wastewater due to the treatment called nixtamalization. The extract is discharged directly into the sewer system, and there is significant evidence of its contribution to environmental pollution. The aim of this paper is to propose a membrane process for the treatment of these wastewaters, in order to reduce their pollutant load in terms of polyphenols, carbohydrates, turbidity, total soluble solids (TSS), total solids content (TSC), pH, calcium, electrical conductivity and total organic carbon (TOC). The wastewaters had a high content of polyphenols (1,190.74 mggallic acid∙liter-1), turbidity (538.09 NTU), TSC (1.34 %), pH (13.48), electrical conductivity (2,424.00 μS∙cm-1), calcium (1,078.3 mg·liter-1), TOC (2,984.10 mg·liter-1) and low content of carbohydrates (3.47 mg·mL-1) and TSS (1.53 ºBrix). The wastewaters were subjected to a microfiltration separation process using a hollow fiber membrane (pore size: 0.2 μm). The viability of the process was analyzed in terms of productivity (709 kg·m-2·h-1 permeate flux), fouling index (22.68 %) and washing efficiency (99.82 %) by enzymatic methods. The membrane showed high retention in turbidity (72.76 %), followed by TSC (23.74 %), electrical conductivity (21.75 %), TSS (15.14 %), carbohydrates (14.69 %) and calcium (11.36 %). Finally, a significant decrease in organic concentration, in terms of TOC, was achieved in the effluent.

Asadero cheese is one of the most important spun paste cheese of Mexico; this is traditional cheese, made with raw cow milk generally produced using traditional methods, existing for decades. In the case of typical asadero cheese, so that paste plasticizes and stretches during kneading, the milk must be fermented with acidulated or lactic acid with an organic acid such as lactic acid, acetic acid or citric acid. Another way to achieve the right stretched is using calcium-sequestering salt such as sodium citrate (trisodium citrate); or combine the effect of the organic acid with calcium-sequestering salt. In this study we made asadero cheese like that made in Aguascalientes using sodium citrate and three levels of acidity of milk. Proximate analysis, some physicochemical properties and yield of the cheeses were also assessed. It was found that, functionally, sodium citrate together with milk acidity allow to make asadero cheese; whose composition varies according to the concentration of citrate added to the paste at the time of kneading. To higher concentration of salt, higher product yield; but also lower acidity (pH greater than 6.7 on the product). The texture of the cheeses analyzed was different; less firm and chewiness with increasing concentration of sodium citrate.