Abstract
Macro- and microorganism activities are important for the effectiveness of the slow sand filtration (SSF), where native microorganisms remove contaminants mainly by substrate competition, predation, and antagonism. The aim of the present study was to evaluate the addition of the oligodynamic metals iron, copper, and brass, inserted separately into SSF to enhance pollutant removal in water samples. Four laboratory-scale SSFs were built and tested: control, iron, copper, and brass. Water analysis included physicochemical evaluation, total and fecal coliform quantification. An analysis on microbial communities in the SSFs schmutzdecke was achieved by using 16S rRNA amplification, the Illumina MiSeq platform, and the QIIME bioinformatics software. The results demonstrated that inorganic and organic contaminants such as coliforms were removed up to 90%. The addition of metals had no significant effect (p > 0.05) on the other parameters. The microbial community analysis demonstrated different compositions of the SSF with brass-influent, where the eukaryote Streptophyta was predominant (31.4%), followed by the acetic acid bacteria Gluconobacter (24.6%), and Acetobacteraceae (7.7%), these genera were absent in the other SSF treatments. In conclusion, the use of a SSF system can be a low cost alternative to reduce microbial contamination in water and thus reduce gastrointestinal diseases in rural areas.
Highlights
SSF system operation is based on a mechanical filtration process that traps organic and inorganic contaminants in very small size grains, where native microorganisms use them as edible substrates
When bacterial cells are exposed to heavy metals, metallic ions are delivered to the cell and bound to DNA, enzymes, and proteins, disrupting membrane permeability and causing cell death[10], which facilitates microorganism removal
The soil physicochemical characterization results are shown in Supplementary good drainage aeration and do not offer resistance to tillage, which benefits microorganisms’ activity[7]
Summary
SSF system operation is based on a mechanical filtration process that traps organic and inorganic contaminants in very small size grains, where native microorganisms use them as edible substrates. This process allows the biolayer, known as schmutzdecke, to provide a rich nutrient environment that promotes microbial growth and biofilm formation[4]. In the SSF system, algae and bacterial predation, detritus compaction, microorganism death, and organic carbon reduction are the main biological mechanisms responsible for contaminant removal[6]. In the SSF system, predation is an important factor that allows enteric microorganism removal during water filtration. The aim of the present study was to evaluate the removal of inorganic and organic pollutants present in water collected from a dam and a river located near to Chihuahua city in Mexico after the addition of an oligodynamic metal—iron, copper, or brass—into a SSF system
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