For me, the most innovative, simple and cost-effective way to purify large quantities of water (including ‘waste’ water) is the Biosand Filter (Slow Sand Filtration Process)
Source: Helvetas Arsenic Bio Filter
Design: Here is how it works:
Source: India Water Portal
As shown in the image, water can be poured from the top of the diffuser plate manually or by using a small pump. The blue box as seen in the image is made out of concrete or plastic and filled with sand and a few pebbles. The design might look very simple but the processes happening inside are far too complex. Also, don’t confuse this system with a typical sand-pebble filter you might have learned about in school.
Working: There are four simultaneously happening processes through which this water filters out. They are – Biological Filtration, Mechanical Trapping, Adsorption and Natural Death. This video via Youtube here, explains the entire process very beautifully:
How to make it better: The water thus obtained by this form of filtration process is very safe to drink. For a more efficient filtration process, UV light and Organic home-grown Activated Carbon can be used in line with this filter to make it much more efficient.
Efficiency: Identical inefficiency to an RO based system but at lower costs. Simply stated, the science is the same. There you have membranes, here you have sand! Technical comparisons are available. Moreover, this can also handle Arsenic-related problems well.
Money Matters!: The overall cost of building one entire system with UV light and Activated Carbon in line will not exceed INR 3000 (compared to ROs running into INR 10,000 +). The per liter filtration cost (after using UV light and Activated Carbon) will be only 8 paisa/liter of water (6 US Cents per liter)! Moreover, the raw materials are indigenously available so setting up a manufacturing hub for such filters is very easy – anywhere. Great!
Maintenance: These filters don’t require maintenance and are excellent for Rural and Community Water filtration processes.
I have even tried to downscale the size. You can find a raw footage via Youtube here:
I’m also working on replacing the sand with something better. The Activated Carbon was prepared in labs using organic matter and the UV light runs on lab-based Solar Cells (termed as DSSC), which are made out of waste mobile screens (reverse engineering) to keep the overall cost very low.
(Love building such stuff, still working on the funding though)
And as images convey a better story, please find some below:
Amazing things science can do for us. The sites mentioned above as sources provide for a lot of great details. More innovations to be covered in future posts.
Abhimanyu Dinesh Rathi 