The Resistance to Decomposition of Certain Organic Matters in Sewage.

This investigation, in regard to the resistance to decomposition of certain organic matters, was begun in order thoroughly to comprehend the conditions prevailing in certain sand filters which had received sewage for periods varying from 10 to 17 years. Studies of the work accomplished by these filters during these many years of operation show that only about 55 per cent, of the nitrogen in the sewage applied to them has appeared in their effluents. Studies of municipal areas, moreover, receiving a fresher sewage, have shown that only about 30 per cent of the applied nitrogen appears in the effluents from these areas. Much of the remaining nitrogen is set free by nitrogen-liberating bacteria; but a small percentage of the nitrogenous matters is resistant to bacterial actions and accumulates within the filter?from 4 to 8 per cent in the experimental filters at Lawrence.1