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<br />- 14 - <br /> <br />collected downstream from the mill. Better than 98% of all the vanadium <br />in the mill effluent during the survey was added in the waste redcake <br />tailings liquor. This is an acid effluent stream, and it carries the <br />vanadium to the river in the form of a soluble ion. Probably because of <br />dilution and neutralizing action of discharged barium salts, the river pH <br />was found to be very nearly the same, just above neutral, both above the <br />mill and 1.6 miles downstream from the mill. As the vanadium ions, in <br />a soluble form in the acid effluent, come in contact with water in which <br />fhe pH is changing from acid toward neutrality, they change from a soluble <br />form to an insoluble one. Most of the vanadium precipitates out or goes <br />into suspension in this short stretch of river; this action may be <br />speeded by interaction with iron floc particles. Of about 72 pounds/ <br />day of vanadium added to the river during cycle I, better than 68 pounds/ <br />day were not found dissolved at the end of this l.6 mile length of river <br />channel. During cycle II, this was true of some 77 pounds/day out of some <br />87 pounds/day added. <br /> <br />Based on effluent flows, the mill contributed an average of 16,600 <br />pounds per day of sulfate to the river. The flow information which re- <br />sulted in this average was given in the form of an annual average. No <br />measurements of effluent flow rate were made during the survey. Based <br />on stream flows, the San Miguel River picked up some 170,000 pounds of <br />sulfate per day between the sampling points just above and below Uravan. <br />No means has been found to reconcile this difference at the present time. <br /> <br />The variation in sodium values at Stations US-8 and US-lO appears <br />large when it is expressed in mg/l. For instance, at station U8-8 during <br />cycle I, the sodium concentration in the composite sample was 30,000 mg/l, <br />whereas it was l5,000 mg/l during cycle II. However, when one considers <br />these values as percentages of a component in a waste stream, the varia- <br />tion is not undue (3.0 vs. 1.5%). Sodium concentrations are raised in <br />the San Miguel River, on the average, by a factor of about four due to <br />the entry of effluent streams from the mill. <br /> <br />Chloride concentration in the San Miguel River rose by about a <br />factor of ten as the river passed Uravan, but the level of chlorides <br />above Uravan was very low (about lO mg/l). A much greater change in <br />chloride concentration is presumably caused by natural causes related <br />to the Dolores River. Chloride concentration in the Dolores River has <br />been mentioned as changing from 93 to 5100 mg/l during cycle II from <br />below Slick Rock to the mouth of the San Miguel River and the change <br />seems to have been attributable to natural causes. When the smaller flow and <br />higher chloride concentration of the Dolores River were mixed with the larger flow <br />