Khalidou M. Bâ

COD fractionation and biological treatability of mixed industrial wastewaters.

This study was conducted at a centralized wastewater treatment plant that receives discharges from nearly 160 industries. The chemical oxygen demand (COD) was fractionated for two objectives: delineation of the limits of the activated sludge process being used at the plant, and evaluation of the potential environmental impact of the treated effluent. Physico-chemical analyses, respirometric and biodegradation tests, as well as COD fractionation were carried out. Molasses-wastewaters were determined to be the major contribution to the plant. The influent was dark brown in color, with a relatively high content of both organics (2503 mg/L COD) and salts (5459 μS/cm conductivity), but a low biochemical oxygen demand (568 mg/L BOD(5)) and BOD(5)/COD ratio (0.24). The degradability of the organics was limited by the high content of inert soluble COD (S(I)). The COD fractionation pattern was 40-20-40% for S(I), X(I) (inerts) and S(H) (soluble hydrolyzable), respectively. More than 90% BOD(5) removal was obtained, which was sufficient for the plant to meet the national Standards. However, the effluent discharged into the river was intensely colored and polluted (>1000 mg/L COD, >5000 μS/cm), emphasizing the need for legislation regulating COD, color and salinity, and for upgraded treatment methods worldwide for molasses wastewaters.

Identification of Variations in the Climatic Conditions of the Lerma-Chapala-Santiago Watershed by Comparative Analysis of Time Series

The current study presents a method for automating the Koppen–Garcia climate classification using a GIS module. This method was then applied in a case study of the Lerma-Chapala-Santiago watershed to compare time series data on climate from 1960 to 1989, 1981 to 2010, and 1960 to 2010. The kappa statistic indicated that the climate classifications of the generated model had a perfect degree of agreement with those of a prior nonautomated study. The climate data from the period 1960 to 2010 were used to create a climate map for the watershed. Overall, the dominant climates were dry, semiarid, temperate, and semiwarm temperate with a summer rainfall pattern. A comparative analysis of climate behavior between 1960 and 1989 and between 1981 and 2010 showed changes in temperature and extreme temperatures over 13.6% and 9.9%, respectively, of the watershed; the presence or absence of mid-summer drought also changed over 0.8% of the watershed. The module developed herein can be used to classify climates across all of Mexico, and data of varying spatial resolution and coverage can be inputted to the module. Finally, this module can be used to automate the creation of climate maps or to update climate maps at diverse spatial-temporal scales.

Les enjeux de l’approvisionnement en eau au Mexique

En 2004, la population du Mexique a depasse les 103 millions d’habitants. Le niveau actuel du taux de croissance demographique du pays tire son origine de la croissance rapide qu’a connue la population jusqu’aux annees soixante-dix du dernier siecle. Bien que le taux de croissance soit en baisse depuis lors, la population a continue d’augmenter significativement en valeur absolue. La commission nationale de la population (CONAPO) prevoit un taux de croissance moyen annuel de 1,2% entre 1995 et 2015, qui, s’il est atteint, sera inferieur au taux actuel de 1.8%. Du point de vu urbain, en 2000, le Mexique comptait 364 villes de plus de 15 000 habitants, ou residaient plus de 65% de la population du pays. A titre d’exemple, on verra le cas de la region appelee Valle de Mexico (Vallee de Mexico), laquelle est situee dans un bassin de 9 600 km2 a une altitude moyenne de 2 200 m. La plus grande partie de l’eau consommee par la population de cette ville provient d’un aquifere situe dans la region urbaine et le reste provient de bassins versants exterieurs. Le transport de l’eau jusqu’a la ville, en plus d’etre une operation peu pratique et onereuse a cause de la difference enorme d’altitude (> 1 km), a mis ces bassins exterieurs dans une situation alarmante (epuisement des ressources naturelles, assechement des cours d’eau, etc.). D’autre part, la ville de Mexico est en train de s’enfoncer par subsidence a cause des quantites d’eau extraites de son sous-sol. Cette region, une des plus peuplees du monde, qui fut jadis une terre fertile et parsemee de lacs a souffert des actions nefastes de l’homme qui a draine ses eaux et accelere sa deforestation. Alors que la ville continue de s’agrandir, le probleme d’approvisionnement en eau s’aggrave. Elle se trouve face a un serieux risque de manquer d’eau ou d’accelerer un processus d’assechement de toutes les regions qui l’entourent.