of the department of civil engineering, announced recently that they have developed a pilot plant which looks like it can take the phosphorus out of sewage effluent.
Large-scale use of the discovery would mean: (1) Sewage effluent would no longer contaminate lakes and streams with surplus phosphorus, one of the elements held responsible for nuisance growths of algae; (2) Sewage phosphorus, which up to now has been lost, could be refined and sold as commercial fertilizer; and (3) Atomic-research men would no longer have to worry about the danger from radio-active phosphorus in wastes.
The engineers made their progress report at a special meeting of the University's Lake Investigations committee. Lea and Rohlich have been working on the project for two years under grants from the committee and from the National Ir~stitute of Health.
Working experimentally in the U. W. hydraulics laboratory and at the Nine Springs Treatment plant of the Madison Metropolitan Sewerage district, they have been able to remove 99 per cent of the phosphorus from the effluent. The ordinary sewage effluent being discharged by the Nine Springs plant contains about 5 parts-per-million of phosphorus. Lea and Rohlich have brought this level down to 7-tenths parts-per-million. This level is actually below the amount of phosphorus contained in most natural creek water.
Lea and Rohlich estimate they could get about a ton of salable phosphorus fertilizer a day out of the 15 million gallons of sewage being processed daily at the Nine Springs plant. They can also retrieve most of the chemicals used in removing the phosphorus. So the net cost of materials for removing the phosphorus at the Nine Springs plant would be less than $90 a day, according to their figures. Lea and Rohlich estimate that the cost of constructing a de-phosphorizing plant at Nine Springs would be about $1,500,000.
The Lea-R6hlich process not only removes virtually all the phosphorus from sewage effluent, but it also cuts down the organic nitrogen by 60 per cent and the "biochemical oxygen demand" by 84 per cent. These are two other factors which help cause excessive algal growths in lakes into which sewage effluent is being dumped. The Lea-Rohlich process has no apparent effect on the amount of ammgnia, nitrates, and nitrites in sewage effluent--three other factors favorable to algal growth.
Nevertheless, U. W. scientists see the Lea-Rohlich de-phosphorizing process as the first significant advance in what they call "tertiary sewage treatment," and one of the first successful attempts to recapture and re-use valuable materials which have been "going down the river."