Help! Salmonella in sewage sludge

George R. Neal mountaineer at eznet.com
Fri Aug 4 09:36:13 EST 1995


In article <3vboii$o2k$1 at mhade.production.compuserve.com>, 
75121.677 at CompuServe.COM says...
>
I can't answer your question for sure because I do not have enough 
information but I may be able to give you some insight. I am a chemist at 
a wastewater plant. We land apply sludge to farms in the Inland Pacific 
Northwest. Application of sludge in the United States is regulated by EPA. 
The regulations are reffered to as "503 Regulations". These regulations 
seem to me to be very well thought out. Some of the regulations which may 
be of interest to you are as follows: 1. Sludge must be applied on slopes 
<17 degrees. 2. Sludge must not be applied within 200 feet of a drinking 
water well or surface water source. 3. The pathogen level must be 
significantly reduced by anaerobic digestion or other means. These 
regulations are designed to prevent transmission of waterborne diseases 
(not just salmonella). Pathogen numbere are greatly lowered by sludge 
digestion and they can be furthur reduced by composting sludge with garden 
material. In fact, sludge composted with garden material can be given away 
or sold to the general public in bags which can be spread by hand. When 
sludge is applied to soil a couple of processes reduce the risk of 
pathogen transmission even furthur. Soil acts like a filter to prevent 
pathogens from migrating off of the place where they were applied. They 
adsorb to cation exchange sites in the soil and the soil acts as a simple 
physical filter. This is why there is a requirement for distance from a 
well. The soil needs some area to absorb pathogens. Pathogens also die due 
to UV radiation as they are exposed to sunlight. Many (not all) pathogens 
also cannot survive for very long outside a host. These are some of the 
rules and factors which the rules are based on which may affect your 
situation. The risk that you face is unknown to me because I do not know 
the particulars of your situation. If you have any furthur questions, feel 
free to contact me.
George R. Neal
mountaineer at eznet.com




More information about the Bioforum mailing list