M.S.

Of all industrial wastes that are discharged into streams, the one that probably causes the most trouble is the waste discharge of pulp mills. The waste quite frequently pollutes streams, principally because it has a high oxygen demand. In satisfying this demand, the dissolved oxygen content of the stream may be lowered to such an extent that it will not support fish life or prevent the occurrence of nuisances. The object of this investigation was to try to satisfy at least a part of this oxygen demand of semi-chemical kraft pulping waste before the waste is discharged into streams. The waste used in this investigation was prepared from a pulping mixture obtained from the Big Island, Virginia, mill of the National Container Corporation, and as prepared, had a total solids content of 2574 to 3591 p.p.m. The investigation was carried out by aerating the waste with and without the addition of chemical oxidizing agents and biological seeds. The results of this investigation show that the 5-day B.O.D. of semi-chemical kraft pulping waste was lowered from 24 to 31 percent by forty-eight hours of aeration at 20°C. without the addition of chemical oxidizing agents or biological seeds. A 40.5 percent reduction in the B.O.D. was obtained by the addition of sodium nitrate in the concentration of 20.0 p.p.m. of nitrogen. When the sodium nitrate concentration was increased to 100.0 p.p.m. of nitrogen, a 43.3 per cent reduction in the B.O.D. was obtained. The additions of sodium bichromate, in concentrations of 0.4 and 20.0 p.p.m. of Cr, and ferric chloride, in concentrations of 0.4 and 20.0 p.p.m. of Fe, did not aid in reducing the 5-day B.O.D. of the waste. Reductions up to 41.4 per cent were obtained with the addition of biological seeds to the waste. An average of 10 percent reduction in the total solids of the waste was obtained with forty-eight hours of aeration with and without the addition of chemical oxidizing agents and biological seeds. / M.S.