Abstract
Contamination of natural water sources is one of the main health problems worldwide, which could be caused by chemicals, metals, or microbial agents. This study aimed to analyze the quality of 18 rivers located in Quito, the capital province of Pichincha, Ecuador, through physico-chemical and microbial parameters. The E. coli and total coliforms assessments were performed by a counting procedure in growth media. Polymerase chain reaction (PCR) was realized to detect several microbial genera, as well as Candida albicans, two parasites (Cryptosporidium and Giardia spp.) and E. coli pathotypes: enterohemorrhagic E. coli (EHEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC) and enteropathogenic E. coli (EPEC). Additionally, physico-chemical parameters and major and trace metals were analyzed in each surface water sample. Our results demonstrated that most of the rivers analyzed do not comply with the microbial, physico-chemical, and metal requirements established by the Ecuadorian legislation. In terms of microbial pollution, the most polluted rivers were Monjas, Machángara, Pisque, and Pita Rivers. Furthermore, three out of four analyzed E. coli pathotypes (EIEC, EHEC, and EAEC) were detected in certain rivers, specifically: Monjas River showed the presence of EIEC and EHEC; in the Machángara River, EAEC and EIEC were detected; and finally, EIEC was present in the Guayllabamba River. Several physico-chemical parameters, such as pH, CODtotal, and TSS values, were higher than the Ecuadorian guidelines in 11, 28, and 28% of the rivers, respectively. Regarding heavy metals, Zn, Cu, Ni, Pb, Cd, and Mn surpassed the established values in 94, 89, 61, 22, 22, and 17% of the rivers, respectively. Machangara River was the only one that registered higher Cr concentrations than the national guidelines. The values of Al and Fe were above the recommended values in 83 and 72% of the rivers. Overall, based on the physical-chemical and microbiological parameters the most contaminated rivers were Machángara and Monjas. This study revealed severe contaminations in Ecuadorean Rivers; further studies should evaluate the sources of contamination and their impact on public health.
Highlights
The discharge of wastes and chemical compounds into rivers is one of the biggest sources of environmental contamination, mainly in developing countries, due to a lack of domestic and industrial wastewater treatment [1,2,3]
The level of contamination was characterized by different types of parameters, microbial load and several microbial genera, physico-chemical parameters, and metal levels
Sequencing analysis confirmed the positive results for Giardia spp., identifying with 100% homology to Giardia intestinalis
Summary
The discharge of wastes and chemical compounds into rivers is one of the biggest sources of environmental contamination, mainly in developing countries, due to a lack of domestic and industrial wastewater treatment [1,2,3]. The absence of water treatment generates an accumulation of environmental pollutants which could lead to severe public health issues [4]. The increase in microorganisms and anthropogenic contaminants enhances the risk of pathogen outbreaks, bacterial antibiotic resistance, and public health costs [8,9]. In 2000, Ecuador evidenced more than two thousand cases of diseases associated with water microbial pollution, where most of those cases consisted of diarrhea or dysentery associated with pathogens, such as Escherichia coli and others [12,13]. The rates of morbidity and mortality by water contamination are increasing in Ecuador [12]
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