Beneficial use of wastewater and its by-products is receiving increasing attention. The objective is to maximize the resource value and minimize the need to consider disposal only. While not always possible, more opportunities for such uses are being pursued. One aspect of this effort is the beneficial use of biosolids or, as it long has been known, sludge. Even the change in terminology reflects the effort to consider these materials as potential resources. While the new term may reflect more an effort to make such materials acceptable to the public from a psychological basis, efforts to assure the material is acceptable based on health risks by minimizing hazards from organisms and chemicals are prerequisite. Among the contaminants of concern are several elements. In the mid 1970s (designated 1975) and during the last several years (designated 1993), samples of wastewater solids were collected from 22 publicly owned wastewater treatment facilities (POTWs), all with pretreatment programs, in Massachusetts. These samples were analyzed for seven metals (Cd, Cr, Cu, Hg, Ni, Pb, Zn). While there are several potentially confounding factors such as differences in sampling and analytical methods, the fact that the mean concentrations of all seven of the metals monitored decreased during the interval 1975–1993 when the two sets of data (126 and 54 samples respectively) were collected suggests that pretreatment and pollution prevention efforts have contributed to improving the quality of biosolids.

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