Elements in Wastewater for Agricultural Use

With the increase in the application of wastewaters for agricultural purposes, the determination of the concentrations of some elements that can be found in such waters and their temporal behavior are of great interest. In this work, treated and untreated sewage samples were analyzed to determine the concentrations of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Na, Ni, Pb, and Zn. Ca, Mg, and Na concentrations were determined to estimate the sodium adsorbed ratio index. Total residue and setteable solids volume in every samples were also determined. With a view to understanding the effects of rainwater on such parameters and on treatment plant process efficiency, rain data for the period of observations were also collected. Analyses were conducted by atomic absorption spectrophotometry. A Perkin-Elmer Model 460 with a nebulizer-flame system and a Perkin-Elmer Model 5000 with an HGA graphite furnace were used to perform analyses. Principal components analysis was performed to simplify the description of the above 13 parameters and gain a better understanding of their interrelationships. Preliminary results showed that rainwater's impact on the concentrations of the investigated elements cannot be considered as simple dilution. Each parameter follows its own evolution; there is no correlation between treated and untreated sewage.