How big and little?

June 4, 2010

~not to scale

I was listening to a talk on sustainability today, and the speaker showed a graphic depicting the Earth and a much smaller sphere that represented the amount of water on the Earth.  I don’t know if he meant it to be just freshwater or not, but that’s what is usually talked about.  Nobody cares how much saltwater there is to drink!

The point of his image was to impress upon us the relative scarcity of water as a resource for human life.  He did the same thing for the Earth’s atmosphere, presumably to show how small its total volume is so we take care about polluting it.  But, I wondered, how significant is this?  The fact that potable water is small in volume in comparison to the volume of the Earth should come as no surprise at all.  Is this just some enviro-sustainability scare story?  I did a few calculations:

Radius of the Earth ~ 6,400 km

Radius of the a sphere containing the Earth’s freshwater ~ 202 km

Radius of the liquid ‘biomass’ of the Earth’s human population ~ 0.4 km

That last one may have you puzzled, but I was just wondering how this hypothetical drinkable sphere compared to the mass of those that drink it.  I took the population of the globe, assumed an average weight of 60 kg (probably conservative, considering how many children and malnourished people there are in the world today) and assumed that 60% of their weight is water – estimates vary depending on age:  it seems to decline as we get older.  That’s how I determined our liquid biomass.

What does it mean?  Well, it’s very small compared to the water-sphere.  Of course, the water is not uniformly distributed, nor is it necessarily found where we need it.  For instance, a good proportion of it is locked into glaciers and the polar ice sheets.  But what does telling us that the water makes a sphere much smaller than the Earth tell us?  Not much there either.

Scale and perspective are key, and they are always in short supply.

Where it all goes

January 13, 2010

Sometimes, when people find out about my professional work with sewage systems, they ask, “Oh, yeah, where does everything go when it goes down the drain? If you live in New York City, there’s a good chance it all goes here:

to the Newtown Creek water pollution control plant run by the NYC Department of Environmental Protection.  This is one of the largest wastewater treatment plants in the world, and I was there for a meeting this morning.  Afterwards, I took a stroll around the perimeter to get a view of the beautiful digesters, shown at the head of this post, that turn the residue of the treatment process into methane gas and inert sludge.  The shape of the tanks is quite innovative, and the DEP is very proud of them.  [In the aerial view, the digesters are on the right, under construction.]  At night, they are illuminated in their waterfront setting with blue searchlights.  These treatment plants are like ‘negative’ farms:  they use natural processes, aided by technology, to break down, rather than grow up, organic matter.

The public investment in facilities like these is enormous, and largely unremarked.  This plant is being enlarged and upgraded to the tune of about one billion dollars.  Lot’s of money is spent on sewage and drinking water, although not always wisely.

In the USA, the Clean Water Act of the 1960s was the impetus for a vast program of construction all across the nation to clean up urban waterways.  When I first came to NYC in college, it was not quite finished:  the entire west side of Manhattan dumped its raw sewage into the Hudson River, and on a  warm summer night, it stank!  A new treatment plant went on line there in the 1980s, and now all of NYC wastewater is treated, except when it’s raining (but that’s a story for another post.)

Consider this:  The waters around the city, in the Hudson and the East River, are easily cleaner than they have been in 100 years, despite the greatly increased population in the surrounding region.  In those bygone days of yore, when handsome lads would cool off in the summer with a dive off the East River docks, more likely than not they were dunking themselves in a pretty filthy brew.  Now it’s clean, although some people have a hard time believing it.

I came across this rather forlorn remnant of local national pride during my walk around the plant.

Ice thoughts…

April 23, 2009

Water into ice…

…When water moves from the solid state to vapor, without becoming liquid, we say it has sublimated or sublimed.

Who would have expected to find a heart of bronze or a brain packed in ice beneath as seductive an exterior as ever…

from The Girl with the Golden Eyes, by Balzac


Seems that arctic ice is doing pretty well this year, despite the predictions of an ice-free pole.