On Tue, 12 Jul 2011 23:03:38 -0400, Joseph Gwinn
wrote:



This is a false dichotomy, and in addition fails back-of-the-envelope
reasonableness calculations.

The false dichotomy is the claim that we can have either clean rivers or
clean glasses. Actually, there is no reason not to have both, as
discussed next.

The main use of phosphate chemicals is fertilizer: "About 95% of the
phosphate rock mined is used to produce fertilizers, animal feeds and
pesticides." [1]

This leaves 5% for everything else, including dishwasher detergents.
Modern dishwashers use a few ounces of detergent per wash, while farms
use phosphate fertilizer by the ton. The difference is thus orders of
magnitude.

So even if we stopped washing dishes altogether, nothing much would
change.

As I said above, The basic problem [with the EPA] is that they don't
know when to just stop, to just declare victory and move on.

Joe Gwinn


http://en.wikipedia.org/wiki/False_dilemma


[1] "World Phosphate Production: Overview and Prospects", L. CISSE and
T. MRABET, World Phosphate Institute, 3, Rue Abdelkader Al Mazini, 20001
Casablanca, Morocco, in Phosphorus Research Bulletin Vol. 15 (2004) p.
21-25, www.imphos.org/download/jena/cisse_prb-15.pdf.

To be reasonable, the back-of-the-envelope calculations need to
account for the fact that most sewage treatment systems do not remove
phosphate, and often deliver it directly to water bodies vulnerable to
algal blooms. On the other hand, fertilizers are applied to soil,
which effectively binds the phosphorous. Which explains why, as
someone else mentioned, septic systems with leach fields generally do
not release much phosphorous.

Septic systems do release considerable nitrogen, which is the limiting
nutrient in salt water, at least here in the northeast. Excess algae
on the clam flats here is often a sign of nitrogen runoff in coves
with limited tidal flushing, whereas phosphorous isn't really a
problem.

--
Ned Simmons