Back to the tap is a project selling reusable bottles with an inbuilt filter. This bottle filters the water as you drink it. All you have to do is to change the filter every now and then (approximately 3 months). An alternative to the disposable plastic bottles. On their web page they are presenting interesting figures how many disposable bottles people actually are purchasing a year, and how much it contributes to the global plastic waste. You can also read more about the subject on Treehugger.