Assessment of water surface quality of Wierna and Mojotoro Rivers from Salta, Argentina

REYES, SARITA ISABEL; JURADO, MARCELO A.; PEÑALOZA, LIDIA; RAJAL, VERONICA BEATRIZ; CÉLIZ, GUSTAVO; CRISTÓBAL, HÉCTOR A

Salta

Congreso; LV Annual SAIB Meeting and XIV PABMB Congress, Sociedad Argentina de Bioquímica y Biología Molecular; 2019

The Wierna and Mojotoro rivers runs from north to south the locality of La Caldera, Salta city. The Mojotoro river receives the discharge of two wastewater treatment plants located in two specific sites. Both rivers are used for recreational purposes, thought, it is important to establish the water quality. The objective of this work was evaluate the influence of the wastewater treatment plants (WWTP) on the physicochemical and microbiological quality. Water samples was obtained from Wierna river (P1) and Mojotoro river (P2, P3). This last river acts as an effluent receptor of two WWTP. The physicalchemical variables were determined in situ: temperature (°C), pH, turbidity (NTU), conductivity (mS/cm), salinity (%) and dissolved oxygen (mg/l); using a portable multiparameter analyzer. In laboratory, density of total (TC) and fecal (FC) coliform bacteria were measured using the multiple tube method (NMP/100 ml). The concentration of Cu, Mn, Pb, Fe, Cr, Zn and Cd were measure by atomic absorption spectrophotometry (AAS) and As by the method of Hydride Generation (HG) coupled to AAS, a total of 90 samples were studied. A Spearman correlation analysis was performed for found relation between variables analyzed and the influence of the WWTP were evaluate using the Wilcoxon test. The maximum and minimum values of the physicalchemical variables were: 8.5-21°C, pH 7.8-9.5, 2->999 NTU, 0.19-0.32 mS/cm, 0-0.02%, 2.3-7.7 mg/l. In addition, the values TC and FC were 0-1.09 106 and 0-1.19 105 NMP/100 ml respectively. The Fe and Mn at P1 and P2 exceed the maximum permissible limits, established by international legislations 0.2 and 0.1 mg/l respectively. The correlations between Zn and conductivity, TC and FC were statistically significant (p-value> 0.05) in all sampling points. The Wilcoxon test showed significant differences (p-value> 0.05) for TC and FC between P1 and P2; and P2 and P3. The Mojotoro river show deterioration in water quality after discharge of wastewater. High concentrations of water quality indicators in these sites represents a risk to the health of the population.