An exploration into the possibility of using proteins and amino acids from waste sludge of activated sludge treatment plants

The objectives of the study were to determine the quantity of protein and the amino acid composition of the biomass that accumulates in an activated sludge treatment plant. As a means of comparison, three industrial waste sludge samples were selected. The industries that supplied waste sludge include a petro-chemical plant, pulp and paper mill, and a food processing plant. Samples were also obtained from the reaeration tank of an activated sludge treatment plant treating a combination domestic and industrial waste. The accumulation of solids in the final clarifier of a conventional (trickling filter) domestic treatment plant was the source of one sample. Laboratory scale reactors with heterogeneous cultures established on sugar and starch substrates, provided several samples for the study. The preparation of the biomass samples varied somewhat from sample to sample, but in general, they were centrifuged, sterilized, and forced air dried (or in a desiccator) . The dry biomass samples were analyzed for total Kjeldahl nitrogen, ash, volatile material, and lipid content. The samples were also analyzed for amino acids using the Beckman 120C Amino Acid Analyzer. From these data, the chemical scores of the samples were determined. The preliminary analysis of the petro-chemical waste sludge indicated that the material contained refractory material and substances that produced offensive odors. The nitrogen content of the solids indicated that the maximum protein possible in the sample was less than 20 per cent. This solid sample was not analyzed for its amino acid composition because of the condition of the material and the possibility of contaminating the ion exchange columns on the amino acid analyzer. The solids sample obtained from the pulp and paper mill's activated sludge treatment plant was not analyzed for its amino acid composition since the fiber content was estimated at 90 - 95 per cent and the nitrogen content was very low (1.40 per cent). This sample did not appear to possess characteristics that would make it desirable as a feed supplement for animals