Assessment of the 20L SODIS bucket household water treatment technology under field conditions in rural Malawi

Evaluation of microplastics release from solar water disinfection poly(ethylene terephthalate) and polypropylene containers

Public health concern associated with the ingestion of microplastics (MPs) released from water packaging materials is increasing. The use of plastic materials for solar disinfection (SODIS) containers has also raised concerns in the SODIS community due to the lack of studies evaluating the presence of MPs in the treated water. In this work, the migration of MPs from poly(ethylene terephthalate, PET) bottles and polypropylene (PP) translucent and transparent jerrycan containers (TJC) into water under natural weathering was investigated using micro-reflectance Fourier Transform Infrared Spectroscopy (µ-FTIR). Containers exposed to sunlight for three months became photodegraded, releasing micro-sized fragments identified as PET, PP and high-density polyethylene (HDPE, from the screw-caps), although with varying degrees of weathering. It is noteworthy that the presence of a clarifying additive in PP formulation did not seem to impact the release of MPs from the containers. The study showed that PP TJC containers released more MPs than PET bottles. Finally, the size of MPs was measured to determine their fate upon ingestion and highlights the need for further studies to understand the safety of these plastic containers for SODIS.

A Low Cost and Eco-Sustainable Device to Determine the End of the Disinfection Process in SODIS

The lack of safe drinking water is one of the main health problems in many regions of the world. In order to face it, Solar water disinfection (SODIS) proposes the use of transparent plastic containers, which are filled with contaminated water, and exposed to direct sunlight until enough UV radiation is received to inactivate the pathogens. However, a reliable method for determining the end of the disinfection process is needed. Although several approaches have been proposed in the literature for this purpose, they do not strictly accomplish two critical constraints that are essential in this type of project, namely, low cost and sustainability. In this paper, we propose an electronic device to determine when the lethal UV dose has been reached in SODIS containers, which accomplishes both constraints mentioned above: on the one hand, its manufacturing cost is around EUR 12, which is much lower than the price of other electronic solutions; on the other hand, the device is sufficiently autonomous to work for months with small low-cost disposable batteries, thereby avoiding the use of rechargeable batteries, which are considered hazardous waste at the end of their useful life. In our approach, we first analyze different low cost UV sensors in order to select the most accurate one by comparing their response with a reference pattern provided by a radiometer. Then, an electronic device is designed using this sensor, which measures the accumulated UV radiation and compares this value with the lethal UV dose to determine the end of the disinfection process. Finally, the device has been manufactured and tested in real conditions to analyze its accuracy, obtaining satisfactory results.

Epidemiological and Immunological Gains from Solar Water Disinfection (SODIS): Fact or Wishful Thinking?

OBJECTIVE

There is still no consensus on the impact of using solar disinfection (SODIS) to reduce the prevalence of waterborne gastrointestinal diseases. The reported reduction in diarrhea prevalence among SODIS users has been attributed to the consumption of water free of viable pathogens. However, it has also been suggested that ingestion of SODIS-inactivated pathogens may induce protective immunological changes that may also contribute to a reduction in the frequency of diarrhea. The present study aimed to critically review the epidemiological and immunological gains of using SODIS.

METHODS

We critically reviewed 22 articles published in English, selected from 2,118 records systematically retrieved from the databases.

RESULTS

All trials (except one) reported a significant reduction in diarrhea prevalence among children using SODIS, but some of the data from trials report contrary findings. All in vitro and in vivo assays indicate that SODIS-inactivated pathogenic bacteria have the potential to induce immunological alterations that may result in protective immunological effects. Studies with a low risk of bias are still awaited to confirm the ability of using SODIS to reduce the prevalence of diarrhea.

CONCLUSION

Reducing the prevalence of diarrhea depends on the success of SODIS delivery strategies in inducing behavioral changes in communities that result in the production of SODIS-compliant outcomes. The results of trials reporting a reduction in the prevalence of diarrhea due to the use of SODIS seem to support the hypothesis of the contribution of the protective immunological effect against diarrhea in SODIS users.