Recycled water. Drinkable?

9/12/2013

Would you drink recycled water? That’s what I had to ask myself when I was preparing for a live talk back interview on SBS Cantonese Radio last month.

Australia experiences recurrent spells of long droughts.  The radio interview asks whether recycling household wastewater is a solution for securing drinkable water our dry continent.  And even if it is a safe solution, would we drink it?

Drinking recycled water is a controversial topic and during the interview some callers utterly rejected the idea of drinking something reclaimed from our household discard.  I held some reservation myself before I studied this topic.  But after reading the recent report, “Drinking Water Through Recycling” by the Australian Academy of Technological Sciences and Engineering, I am convinced that drinking recycled water is a perfectly safe and sustainable solution.  It is also much cheaper and greener to recycle compared to other drink water production options like sea water desalination.

Upon comparing different solutions, the report favours adding recycled water directly into our drinking supply (“Direct Potable Reuse” or DPR).  Safety levels could be ensured regardless of the solution considered, but DPR is the cheapest option: it requires the least energy to run, and the least material to build, it concludes.

And the technology is already here.  Reverse osmosis membrane and active carbon can be used to remove dissolved substances in selectively sourced waste water.  After disinfection (by ozone, chlorine, UV etc.) the water is ready to be blended into our water system.  Desalination plants also do reverse osmosis, but they use a lot more electricity because sea water is a lot saltier, and needs to be pumped in from off the coast.

Of course, social attitude has a lot of influence on whether we will drink directly recycled water one day. Australians are already drinking recycled water indirectly - many towns source their water supply downstream from treatment plants. The technology explored here is a much more thorough cleaning process. Namibia, USA and Singapore have all used it for many years to different extends and have demonstrated its safety.  Many of the SBS talk-back callers were comforted by the explanation that water is a carrier that that nature recycles all the time, and this technology recycles the water, not the waste it once carried.

Louie

FUN FACT:

The pores on Reverse Osmosis membranes are just big enough to drive water molecules through.  If a water molecule were the size of a tennis ball, a virus would be like a semi-trailer truck, and bacteria would each be a pyramid.