27th February 2015 at 8:36 pm #877
I also found the adaptations section on the CMS website very helpful. It nicely demystifies BioSand filter design and the home made biological sand filterthere has some sensible simplifications to the original design. I have had to think about how to teach people to make filters with plastic drums. One thing I would add is that when using plastic it is definitely worth scratching up the inside surface with horizontal scratches. A broken piece of brick is good for this. This is a simple enough addition to the design for it not to lose its potential to be spread virally by word of mouth, and a sensible precaution in case people start using plastic containers that are incredibly smooth inside.
Using charcoal would help quality but as you know the carbon very gradually becomes obsolete. Users don’t notice the quality changing and most won’t change the charcoal. Smell and colour probably won’t be a problem as no doubt you will be teaching people that germs are invisible and that bio filters take out diseases. Lets face it even in the UK household carbon filters are notoriously forgotten about and most are not changed as often as they ort to be.