Wednesday, April 26, 2017

Armed for bear: My favourite portable water filters configuration

For today's post, let's move away from serious talk such as national water supply and dive back into water filters.

When I am outside of good old SG where the water (tap or otherwise) cannot be relied upon to be safe (biologically at least), I trust my health on the water treatment that has never failed me (yet) - good old boiling. Boiling is great against microbes and parasites! For good measure, I prefer to get a rolling boil for 3min though some literature quote that 1min is enough.

But let's face it - boiling requires a good source of fuel (e.g. finding dry wood can be a pain after a heavy downpour in the middle of the jungle) and a big enough pot (typically metallic which can another pain to carry along in the bush). This is not to mention that you have wait... for the boiled water to cool down before drinking.

Therefore in cases for which the above conditions do not apply (e.g. no fuel, no pot, need to drink now), I rely on a handy package to treat my water.
  1. I have already introduced the Sawyer Mini filter before. What's not to like about it? It is small and versatile, removes most bacteria and parasites (99.99999% and 99.9999%, respectively) and super high capacity (100 000 gallons!).
  2. To squeeze even more performance out of my Mini, I hook it up to a Platypus Gravityworks Carbon element. Containing granular activated carbon (GAC), it is good to remove odours and taste due to organic compounds and chlorine.

    However, compared to the Mini, this little guy is only rated for 300L capacity, depending on the water quality so expect to replace it long before the Mini. There is also a slight increase in resistance when the 2 are connected together so be prepared to suck or squeeze harder to get drinkable water but it's nothing that cannot be overcome.

    Finally, the most important caveat... it is not designed to remove dangerous substances such as pesticides, solvents, heavy metals, radioisotopes... so if you have a reason to suspect such nasty stuff in your water, forget filtration and look for another water source.
  3. Not forgetting another nasty group of microbes - the viruses. I have posted before about the Steripen and how convenient it is. (Update by author on 13/5/18: This particular model of Steripen, Journey (no longer in production) is designed for only 50L of disinfection before requiring a change of batteries - 2x CR123. Wow! This is pathetic considering 100 000 gallons for the Sawyer Mini and even the measly 300L of the Platypus Gravityworks can beat this guy.) This guy can now play rear defence to polish whatever nasty bugs not removed by the Mini. Having the Mini in front also serves to remove particulates which may otherwise reduce the effectiveness of the Steripen.
  4. In actual practice, I do not place the Mini as the first man unless the water is exceedingly clear such as in an uphill jungle stream. Either I allow the water to settle first, then draw the supernatant into the Mini or I place a coffee filter before the Mini. This small and cheap accessory will prolong the life of my Mini so that it does not clog up prematurely.
  5. What I love about this setup is I can pack everything into a typical pencil case and I am ready to go. Just to restate a precaution, this setup is NOT omnipotent and does not remove chemical and radiological hazards.
Figure: The Carbon Element MUST BE fixed after the Mini to minimise unwanted bacterial growth on the GAC.

Figure: clearing up the leftover bugs with the Steripen

Friday, April 21, 2017

Relooking at the numbers of Singapore's water supply: 3 very interesting deductions (part 3 - final)

Though this is the final deduction of my 3-part series (part 1, part 2), I am planning to write a few more posts based on the discussion we had in the Future of Singapore forum on water security. For example, solutions to more effective rainwater harvesting (RWH) and another method to augment our water supply in "water scarce" SG. (But if you have read my part 1, SG definitely has no lack of rainwater.)

From  part 1
  1. Currently, our local catchment can presumably contribute 150MGD (imperial mega gallons per day) to an overall demand of 430MGD.
  2. Total demand in 2030 was interpolated to be 570MGD.

From PUB figures
  1. year 2030
    1. Contribution from Newater = 50%
    2. Contribution from desalination = 30%
  2. Year 2060
    1. Total demand is projected to be 860MGD.
    2. Contribution from Newater = 55%
    3. Contribution from desalination = 30%
Working with the numbers above
  1. 2030
    1. As in part 1, we reasonably assume that we can do without imported water (aka Johor water) and that the Newater and desalination plants are working hard at full capacity, local catchment can supply the remaining 20% of total demand.
    2. Multiplying by 570MGD, this works out to 114MGD.
  2. 2060
    1. Since we are only a year away from expiry of our water agreement with Malaysia in 2061, let's assume we are completely self-sufficient in 2060. (What are the odds of renewing the agreement? Hard to tell since it is still so far in the future.)
    2. Taking imported water out of the equation, our local catchment is left with contributing the remaining 15% of total demand.
    3. Multiplying by 860MGD, this works out to 129MGD.
  3. The trend then goes like this for our local catchment:
    150MGD (2017) --- 114MGD (2030) --- 129MGD (2060)
    Why are we seeing a decreasing contribution from our local catchment between now and the future?
    (Let's ignore the increase from 2030 to 2060 for now.)
    No doubt, I did make a couple of assumptions but I believe they are reasonable.
  4. Climate change?
    Possible. This region is modelled to have more intense rainfall but also more evaporation from a higher temperature.
  5. What is strange is according to PUB, "In the long run, our water catchment area will increase from two-thirds to 90% of Singapore’s land area. Most of this will be made up of unprotected catchments which are land where development is allowed, for example, for residential, commercial and non-pollutive industrial purposes."
    Shouldn't this translate to a greater contribution from local catchment?
    One possible explanation is the increase in catchment area is not via your typical reservoirs but through exploiting the small rivers and drains around the outskirts of SG island. This involves the use of VSP (variable salinity plant) which can desalt either brackish water (during rainy weather) or seawater (during dry weather). (References: 1, 2)

    Perhaps these VSPs are classified as desalination too? But if this is so, perhaps we should not be describing that our catchment is increasing to 90%? Still, VSPs do not explain the decrease in the contribution of our local catchment between now and the future.
  6. Something that we do not know??? If you do know, please share with the rest of us.