Methods 



During October and November, 1973, sludge samples were collected from 

 22 N.H. sewage treatment plants. Samples were not collected from several 

 communities which have treatment systems, since disposal is via small lagoons, 

 or an anaerobic digester is emptied only once a year. 



Nitrogen was determined by Kjeldahl method (Bremner 1965), and carbon 

 by the Walkley-Black wet oxidation method (Allison, 1965). Phosphorus, 

 potassium, calcium, magnesium, sodium, manganese, iron, boron, copper, zinc, 

 aluminum, strontium, barium, and molybdenum were determined at the Ohio 

 Research and Development Center's Spetrographic Laboratory. Silver, beryUium, 

 cadmium, cobalt, chromium, lithium, nickel, lead, antimony, and tin were 

 determined by emission spectroscopy at the University of New Hampshire's 

 Center for Industrial and Institutional Development, 



Errors in Measurement 



Due to high cost of analysis and limited research funds, only one sample was 

 collected from each of the treatment plants. Thus, the chemical analyses are 

 merely indicative of the sludge composition on a given calendar date. They may 

 or may not be representative of sludge composition if measured over a longer 

 period of time, since sludges from the same source can vary considerably in their 

 composition, even on a daily basis. For example, Sommers and Nelson (1974) 

 found that, in analyzing sludges from nine Indiana cities over a two-year period, 

 constituent variations of 60 percent or greater from the average values were not 

 uncommon. Relative magnitudes are, however, indicative of what one might find 

 in the sludges of New Hampshire. 



In addition, the precision of analysis must be considered. Errors in analysis 

 of nitrogen and carbon may be assumed to be no greater than two percent. 

 However, error in spectrophotometric analyses tend to be somewhat greater. The 

 reported values for the elements other than nitrogen and carbon are considered 

 to be within thirty percent of the actual value. 



Results and Discussion 



For comparative purposes, the towns from which sludge samples were 

 obtained were divided into three groups: (1) those containing little or no 

 industry, (2) those having a moderate amount of industry, and (3) those which 

 are heavily industrial. (Table 1). The latter group is of greatest interest since the 

 sludge from industrial towns is the most likely to contain potentially toxic 

 elements in substantial quantities. The sludges of all towns having probable 

 industrial input to the treatment plant were analyzed for ten potentially toxic 

 elements. This included all the towns of groups 2 and 3 (Salem was inadvertently 

 omitted). In addition, three sludges were included from Group 1: Durham, 

 because of the unknown input from the University; Goffstown, because of a 



