SODIS: Is it Safe?

Solar Disinfection of water, also known as SODIS, is a method that uses sunlight to purify water in glass or plastic PET bottles. The method purifies water in anywhere from six hours to two days, depending on the degree of cloudiness in the sky and the turbidity of the water. It is highly regarded for its ease and low-cost, and for these reasons has been implemented in developing countries as a safe, effective method of water purification.

But how safe and effective is it?

The main argument against this method of water disinfection is the use of PET bottles to carry it out. Some claim that it is dangerous to drink water from a plastic bottle that has been left in a hot car for a few hours, because the toxins from the plastic could leach into the water. According to this claim, over time this method of water disinfection could become carcinogenic. Of course, proponents of the method refute this claim, regarding it as perfectly safe. After all, even if SODIS is toxic over time, it is saving lives in the short run, preventing diarrhea in residents of developing countries where gastrointestinal illness from poor water quality can be fatal.

The effectiveness of the method seems questionable too. On cloudy and rainy days, it takes longer to purify the water. If the water is too turbid, it must be filtered first. However, many filters that are available to developing nations do the work of purification as well, rendering SODIS unnecessary. A fairly recent youtube video demonstrates how to purify water using the SODIS method:

(Since when do people in developing countries have access to youtube?)

“Eco-Friendly” Bottled Water? Part Three: Eco-Shape and Biodegradable PET Plastic

In case you haven’t been keeping up, here’s a quick recap.  In part one of this series on eco-friendly bottled water, we introduced several bottles made with bioplastic.  In part two, the paper bottle was born.  Here, we discuss the environmentally friendly-er PET plastic bottle. Yes, it does exist, though these last three may be a bit harder to swallow.


PureLife Brand Purified Water, Arrowhead Brand Mountain Spring Water and Poland Spring Brand Natural Spring Water are made with 30 percent less plastic than other comparably-sized plastic beverage bottles.  The label is one third-smaller and its eco-shape design makes it flexible, lighter and easier to crush for recycling.  Clearly, Nestle is embracing the concept “less is more,” but I’m not sure it’s really working.  They might need to eliminate plastic altogether if they want to catch up with their competitors.


Nestle isn’t the only company desperate to save its brand from environmental fury.  Coca-Cola followed suit with its Dasani PlantBottle – made with up to 30 percent plant materials, it is 100 percent recyclable and renewable.  Nice job, Coke.  Perhaps your efforts to go green will take some of the attention off of the fact that your water is municipally-sourced and a waste of most peoples’ hard-earned cash.


Aquamantra’s ENSO bottle is the first biodegradable PET plastic bottle on the market. Both landfill and compost biodegradation completes in one to five years, depending on the environment’s microbial levels. Better than traditional plastic, but still – up to five years? Why not just eliminate waste altogether?