Technical Bulletin No. 0071: The Effect of Nutrient Additions upon the Rate of Stabilization of Spent Sulfite Liquor
On converting from calcium to the soluble ammonia base sulfite pulping it may be well to take into consideration the effects of the change upon the receiving stream. Several laboratory experiments were undertaken. To determine the effect of nitrogen 6nd phosphorus supplement6 upon the rate of oxidation of spent sulfite liquor added to river water. Various concentrations of calcium base sulfite liquor with and without nitrogen and phosphorus supplement were added to river water, and daily ROD determinations were conducted for 8 days to determine the rate of biochemical oxidation of the various pulp mill pollution loadings and to ascertain the effect of nutrient supplement upon the rate of biochemical oxidation of spent sulfite liquor, From the results presented the following general conclusions may be drawn: 1. In certain stretches of the Willamette River definite nutritional deficiencies existed and the addition of nitrogen would tend to increase the rate of deoxygenation of Willamette River water. 2. In streams, or particular stretches of a stream receiving calcium base liquor, where nutrient deficiencies exist, the rate of biochemical oxidation will be a function of the spent sulfite liquor loading; that is, an increase in the nitrogen deficient organic load will result in a consequent decrease in the rate of biochemical oxidation. 3. In nitrogen deficient streams receiving SSL, conversion from calcium to ammonia base would result in an increase in the rate of biochemical oxidation of the organic load and greater deoxygenation of the receiving stream at equivalent pollution loadings. 4. In calculating the self purification capacity of nitrogen deficient streams, considerable error will arise by assuming the rate of biochemical oxidation to be equal at all pollution loadings. If a definite nitrogen deficiency exists, reduction of the pollution load will not necessarily result in an equivalent improvement of the dissolved oxygen content of the stream since the reduction has resulted in a more favorable ROD to nitrogen ratio with a resultant increase in the oxidation rate of the organic load and consequent increase in deoxygenation of the stream.