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The U.S. Environmental Protection Agency recently ordered the city of Tolleson, Ariz. to develop a plan to prevent sludge exceeding various pathogen and metal limits from being transferred off-site.
The city is required to submit its plan and lab analysis to the EPA and the Arizona Department of Environmental Quality before transferring biosolids to a composting facility or to another party. The samples must show non-detectable levels of pathogens and low concentrations of certain metals. The city must have a plan in place should batches fail EPA and ADEQ limits.
"The city of Tolleson has a responsibility to show that the biosolids leaving its plant are low in metals and are pathogen-free," said Alexis Strauss, the EPA's Water Division director for the Pacific Southwest region. "The EPA will continue to oversee compliance with our national requirements for environmental protection."
According to its 2002 annual report, the city's wastewater treatment plant failed to use correct methods to test for pathogens, and on two occasions detectable levels of salmonella were found. On the same sampling there were high levels of fecal coliform -- an indicator of organisms capable of causing disease.
The city also failed to run the required number of tests for arsenic and mercury in 2002. Lab results found levels of arsenic and another metal exceeding EPA and ADEQ limits.
Composting companies use sewage sludge and compost it with green waste, which is then distributed for horticultural use.