Rubén Asesor López Cervantes

Number of residual thermotolerant coliforms on plants and in soil when using reclaimed domestic wastewater for irrigation.

The reclamation of domestic wastewater for irrigation is one alternative approach to solve the water scarcity crisis, but it is essential to control the microbiological quality of wastewater used for irrigation. The removal of thermotolerant coliforms, also known as faecal coliforms (FC), from treated domestic wastewater by intermittent media infiltration (IMI) in column was studied. The columns were filled with natural filter media (soil, soil/charcoal and zinc-modified zeolite, Zeo-Zn), and wastewater, IMI-treated wastewater and disinfected wastewater were compared. The numbers of residual FC on Swiss chard (Beta vulgaris) and in agricultural soil were determined over a 4-month period. The column using Zeo-Zn had a higher FC removal efficiency (2.98 log) than columns with other filter media and disinfection (1.87-2.57 log) due to the bactericidal properties of Zn(2+). The treatment of wastewater using Zeo-Zn and disinfection both decreased the accumulation of FC on plants and in soil to approximately 1-20 MPN/g dry matter. IMI-treated wastewater using the column with Zeo-Zn was suitable for unrestricted agricultural use, complied with Mexican regulations (as did disinfected wastewater) and had a low risk of FC contamination of plants and soil.

Metales pesados y calidad agronómica del agua residual tratada

espanolEn este estudio se recolectaron muestras de agua en el efluente de una planta de tratamiento de agua residual durante los meses de enero a julio de 2012. El objetivo fue determinar la concentracion de metales pesados, asi como evaluar la calidad agricola del agua residual tratada. Los resultados del analisis de los elementos: cadmio (Cd), cobre (Cu), cromo (Cr), niquel (Ni), plomo (Pb) y zinc (Zn), muestran que la concentracion de estos metales fue baja, por lo que, de acuerdo con la NOM-001-SEMARNAT-1996 el agua residual tratada cumple con la concentracion permitida para su descarga en cuerpos receptores. Mediante las variables Ca2+, Mg2+, Na+, K+, CO3(2-), HCO3-, Cl-, SO4(2-), pH, conductividad electrica (CE) y relacion de adsorcion de sodio (RAS) se determino su calidad agricola. Los indicadores de salinidad muestran que el agua no es adecuada para la irrigacion. Los valores de RAS fueron menores de 5,5 meq L-1, y los valores conjuntos CE-RAS sugieren la clasificacion del agua como C4-S1, lo que indica que el agua tiene restricciones de uso por el riesgo de salinidad al aplicarla al riego agricola. EnglishIn this study, water samples were collectedfrom the effluent of a treatment plant wastewater during the months of January to July 2012. The objective was to determine the concentration ofheavy metals, as well as evaluating the agricultural quality of the treated wastewater. The results of analysis of elements: cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb) and zinc (Zn), show that the concentration of these metals was low, so which, according to NOM-001-SEMARNAT-1996 the treated wastewater complies with the permitted concentrationfor download on receiving bodies. Using variables: Ca²+, Mg2+, Na+, K+, CO3(2-), HCO3-, Cl-, SO4(2-), pH, electrical conductivity (EC) and sodium adsorption ratio (SAR) was determined agricultural quality. The salinity indicators show that water is not suitable for irrigation. The SAR values were lower than 5.5 meq L-1, the joint EC-SAR values show that water use is restricted by salinity risk when applied to irrigation.