Microbial contamination of beach sand

Beach sand may act as a reservoir for potential human pathogens, posing a public health risk. Microbiological monitoring of beach sand could be an indicative tool to determine its quality. Thus, this study aimed to assess the microbial contamination of beach sand and evaluate the potential of quicklime (CaO) for decontamination purposes. Sand samples were analyzed by microbiological (CFU counts) and molecular methods (microarray and Whole Genome Sequencing, WGS), showing the significant presence of contaminants of human and animal origin, including virulent and drug-resistant strains. The potential usage of CaO as a restoring method was first tested in vitro and then assessed in on-field tests, mixing sand with 1-3% CaO (w/w). Results demonstrated CaO ability to provide prompt and effective decontamination from bacteria, fungi, and viruses persisting for around one month post-treatment. In conclusion, this study provides a first description of the sand microbiome by deep sequencing, highlighting the importance of monitoring sand, besides water, to assess beach quality and safety. Besides, first evidence of CaO potential for sand decontamination is also provided, suggesting its usage as a possible way to restore the microbiological quality of sand in highly contaminated areas.