Editing Sewage sludge (section)

==== Classes of sewage sludge in the United States ====
In the United States, two classes of sewage sludge are defined by  the amount of [[Pathogen|pathogens]] (i.e. [[bacteria]], [[Virus|viruses]]) remaining in the sludge, and therefore the types of uses allowed by law.<ref name=":0">{{Cite journal |last1=Popoola |first1=Lekan Taofeek |last2=Olawale |first2=Theophilus Ogunwumi |last3=Salami |first3=Lukumon |date=2023 |title=A review on the fate and effects of contaminants in biosolids applied on land: Hazards and government regulatory policies |journal=Heliyon |volume=9 |issue=10 |pages=e19788 |doi=10.1016/j.heliyon.2023.e19788 |issn=2405-8440 |pmc=10556614 |pmid=37810801 |doi-access=free|bibcode=2023Heliy...919788P }}</ref><ref name=":1">{{Cite journal |last1=Lu |first1=Qin |last2=He |first2=Zhenli L. |last3=Stoffella |first3=Peter J. |date=2012 |title=Land Application of Biosolids in the USA: A Review |journal=Applied and Environmental Soil Science |language=en |volume=2012 |pages=1–11 |doi=10.1155/2012/201462 |issn=1687-7667 |doi-access=free}}</ref> Both classes of sludge may still contain [[radioactive]] or [[pharmaceutical]] wastes.<ref>{{cite web |title=Pharmaceutical waste management |url=http://premierinc.com/safety/topics/pharma-waste/ |archive-url=https://web.archive.org/web/20070525065015/https://www.premierinc.com/safety/topics/pharma-waste/ |archive-date=25 May 2007 |access-date=30 May 2017 |website=Premier}}</ref><ref name="ieee">{{cite web |last=Boyd |first=John |date=26 August 2011 |title=Radioactive Sludge Collects in Japan's Sewage Treatment Plants |url=https://spectrum.ieee.org/radioactive-sludge-collects-in-japans-sewage-treatment-plants |access-date=30 May 2017 |website=[[Institute of Electrical and Electronics Engineers|IEEE]]}}</ref>

Class A sludge must be treated so that specific pathogens (like [[Salmonella]]) are no longer detected. This class of sludge can be used for all land applications, including where the public may come into contact with it (i.e. agricultural land, home use, for public sale).<ref name=":0" /><ref name=":1" /> Biosolids that meet Class A pathogen reduction requirements or equivalent treatment by a "Process to Further Reduce Pathogens" (PFRP) have the least restrictions on use. PFRPs include [[pasteurization]], heat drying, [[thermophilic]] [[composting]] (aerobic digestion, most common method), and [[beta ray|beta]] or [[gamma ray]] [[irradiation]].<ref>{{cite web |title=Processes to Further Reduce Pathogens (PFRPs) |url=http://www.epa.gov/nrmrl/pubs/625r92013/625R92013chap7.pdf |archive-url=https://web.archive.org/web/20090306082938/https://www.epa.gov/nrmrl/pubs/625r92013/625R92013chap7.pdf |archive-date=6 March 2009 |access-date=5 June 2017 |website=[[United States Environmental Protection Agency|EPA]]}}</ref>

Class B sludge also requires treatment to reduce pathogens, but pathogens are still detectable in the sludge (such as some [[parasitic worm]] eggs).<ref name=":1" /> This class of sludge has much stricter restrictions on its use.<ref name=":0" /><ref name=":1" /> Biosolids that meet the Class B pathogen treatment and pollutant criteria, in accordance with the EPA "Standards for the use or disposal of sewage sludge" (40 CFR Part 503), can be land applied with formal site restrictions and strict record keeping.<ref>{{cite web |title=Title 40 - Protection of Environment |url=http://edocket.access.gpo.gov/cfr_2003/julqtr/40cfr503.16.htm |access-date=5 June 2017 |website=[[United States Government Publishing Office|GPO]]}}</ref>