prov:value
| - Then too, specific research at the Pennsylvania State Universityhas demonstrated that sludge from treatment plants throughout theCommonwealth contain varying quantities of nitrogen, phosphorous, potassium,calcium, magnesium, iron, manganese, boron, molybdenum, zinc, and copper.Furthermore, Commonwealth sludge may also contain nonessential traceelements and heavy metals such as chromium, lead, nick
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