Reality-Based Engineering: EPA Rescinds Plans To Allow For Blending of Partially-Treated Sewage for Discharge

Saturday, May 28, 2005

EPA Rescinds Plans To Allow For Blending of Partially-Treated Sewage for Discharge

I get this regular collection of water treatment related articles across the country, and this one really cought my eye - the EPA was looking into allowing municipalities to blend partially treated wastewater with fully treated wastewater. This article is from the Seattle Times and describes that municipalites across the country do this during certain times for whatever reason. Shellfish farmers in the Puget Sound area banded together to "send it back to the drawing board". That's all well and good, and should be applauded since it could cause increases in things like Red Tide.

Certainly, I could forsee instances when you'd want to have the emergency need to push out overflow. You don't want to spend 000's of billions of dollars all across the nation (and, remember, this is a local spending thing and any demands from the USG to build capacity would be an unfunded mandate). But, it really depends on WHAT the 'partially treated' waste is! Basically, municipal wastewater treatment involves for following:

Primary Clarification - settling out all the solids and essentially decanting off the remaining water. For those Bostonians reading this, Deer Island for years ONLY did this, which is why Boston Harbor was disgusting for so long - there's a reason the Standells wrote "Dirty Water" (here, too). Only with the (then) controvercial expansion of Deer Island to double its capacity did they also go beyond this.
Secondary Treatment - this is usually a bioogical treatment to remove what's called BOD (biological oxygen demand) from the primary effluent by using biology to do it's thing - eat. There are several types of secdonary treatment scenarios.
Tertiary Treatment - this is now being done by more and more cities and towns, especially in California, to use some sort of membrane treatment to filter out impurities to the micron and sub-micron level. This movement really took off when it was found that that things like giardia and cryptosporidium cold get through secondary treatment and then infect people. When you have floods and your city tells you to boil your water, these two buggers are the typical reason (but don't overboil!). Membrane treatment can affect a 9-log reduction in the count of these bugs. Especially in southern CA, they are injecting tertiary treated water into the ground near the coastline in order to push out seawater which increasingly infiltrates the local aquifers, rendering them unusable.

So, if you're telling me that you're going to mix secondary treated water with tert-treated water, I could see it being possible in an emergency situation. But if you're going to allow cities to regularly mix primary and secondary effluent, give me a break - that's rediculous. And just another thing that W is trying to do to pork us all (see all his other EPA regulation 'redefinitions' over the past 5 years).