Stream water quality is controlled by the interaction of natural and anthropogenic factors over a range of temporal and spatial scales. Among these anthropogenic factors, land cover changes at catchment scale can affect stream water quality. This work aims to evaluate the influence of land use and seasonality on stream water quality in a representative tropical headwater catchment named as Córrego Água Limpa (Sao Paulo, Brasil), which is highly influenced by intensive agricultural activities and urban areas. Two systematic sampling approach campaigns were implemented with six sampling points along the stream of the headwater catchment to evaluate water quality during the rainy and dry seasons. Three replicates were collected at each sampling point in 2011. Electrical conductivity, nitrates, nitrites, sodium superoxide, Chemical Oxygen Demand (DQO), colour, turbidity, suspended solids, soluble solids and total solids were measured. Water quality parameters differed among sampling points, being lower at the headwater sampling point (0m above sea level), and then progressively higher until the last downstream sampling point (2500m above sea level). For the dry season, the mean discharge was 39.5ls⁻¹ (from April to September) whereas 113.0ls⁻¹ were averaged during the rainy season (from October to March). In addition, significant temporal and spatial differences were observed (P<0.05) for the fourteen parameters during the rainy and dry period. The study enhance significant relationships among land use and water quality and its temporal effect, showing seasonal differences between the land use and water quality connection, highlighting the importance of multiple spatial and temporal scales for understanding the impacts of human activities on catchment ecosystem services.

En este estudio se ha planteado la necesidad de evaluar el funcionamiento de proceso biológico utilizando tecnología MBR con el objeto de establecer las condiciones operacionales que permiten obtener un proceso de filtración en las diferentes circunstancias que puedan presentarse. | This study has raised the need to evaluate the performance of the biological process in order to establish operational conditions to obtain filtration process in different circumstances that may arise.

La demanda química de Oxígeno (DQO) determina la cantidad de oxígeno requerido para oxidar la materia orgánica contenida en una muestra de agua, bajo condiciones específicas de agente oxidante, temperatura y tiempo de reacción. Para determinar este parámetro en una muestra de agua residual pueden usarse básicamente dos métodos, uno de digestión a reflujo en sistema abierto y otro de digestión en sistema cerrado. Sin embargo, en ambos casos, la digestión tarda dos horas y la medición, en su conjunto, por lo menos tres horas. En este proyecto de investigación se busca establecer una relación entre la DQO de una muestra de agua residual doméstica y su absorbancia en la región UV/VIS comprendida entre 250 y 600 nm. Para ello se toman muestras compuestas de agua residual en tres puntos distintos del Río Tunjuelo, denominados en este estudio como ‘Makro sobre Autopista Sur’, ‘Carrera 80 con intersección Río Tunjuelo’ y ‘Río Tunjuelo con intersección Avenida Ciudad de Cali.’ En cada uno de esos puntos se midió la DQO por el método estándar de digestión en sistema cerrado (SM 5220 CHEMICAL OXYGEN DEMAND) y posteriormente se determinó el área bajo la curva espectral, ABC’ en el rango 250-600 nm, encontrándose, para todos los casos, una relación absolutamente lineal entre estas dos variables. Las mediciones espectrales se realizaron en un espectrofotómetro marca Shimadzu, Modelo UV 1280, utilizando celdas de cuarzo, de un centímetro de espesor. Las curvas de calibración se construyeron sobre diluciones de la muestra original, en factores de 10 y, midiendo, para cada una de esas muestras diluidas, el área bajo la curva espectral en el rango 250 a 600 nm. Con estos datos se realizaron gráficas de ABC ‘vs’ DQO, obteniéndose, en la mayoría de los ensayos, coeficientes de correlación lineal cercanos a uno. Finalmente, con dichas curvas se realizaron ejercicios de predicción, cuyas desviaciones fueron inferiores al 15 %. No obstante, se encontró también, que las predicciones se ajustan mejor cuando las curvas se construyen por rangos de concentración. Análogamente a como sucede con la masa de una sustancia -no existe una balanza capaz de medir con precisión, desde 1,0 miligramo hasta una tonelada- tampoco se encontró una curva de calibración capaz de predecir con precisión la DQO de una muestra de agua residual doméstica, para cualquier rango de concentración. | The Chemical Oxygen Demand (COD) determines the amount of oxygen required to oxidize the organic matter contained in a water sample, under specific conditions of oxidizing agent, temperature and reaction time. In order to determine this parameter in a sample of residual water, two methods can be used, one of reflux digestion in the open system and another of digestion in the closed system. However, in both cases, the digestion takes two hours and the measurement, as a whole, at least three hours. This research project seeks to establish a relationship between the COD of a sample of domestic wastewater and its absorbance in the UV / VIS region between 250 and 600 nm. For this, composite samples of wastewater are taken at three different points of the Tunjuelo River, referred to in this study as ‘Makro on Autopista Sur’, ‘Carrera 80 with intersection Río Tunjuelito’ and ‘Río Tunjuelito with intersection Avenida Ciudad de Cali.’ In each of these points the COD was measured by the standard closed system digestion method (SM 5220 CHEMICAL OXYGEN DEMAND) and subsequently the area under the spectral curve, ABC 'in the range 250-600 nm was determined, being, for In all cases, an absolutely linear relationship between these two variables. The spectral measurements were made on a Shimadzu brand spectrophotometer, Model UV 1280, using quartz cells, one centimeter thick. The calibration curves were constructed on dilutions of the original sample, by factors of 10 and, measuring, for each of those diluted samples, the area under the spectral curve in the range 250 to 600 nm. With these data, graphs of ABC ‘vs’ COD were made, obtaining, in most of the trials, linear correlation coefficients close to one.inally, with these curves, prediction exercises were performed, whose deviations were less than 15%. However, it was also found that the predictions fit better when the curves are constructed by concentration ranges. Similarly to what happens with the mass of a substance - there is no balance capable of measuring accurately, from 1.0 milligram to one ton - nor in this case was a calibration curve able to accurately predict the COD of a sample of domestic wastewater, for any concentration range.