DISINFECTION OF EFFLUENT FROM TRICKLING FILTER WITH CHLORIDE OF LIME.

In conclusion, it is believed that the solution of the problem is the filtration of the Lake water and the purification of sewage before it is discharged into the Lake.

No single municipality can hope adequately to handle the situation. The problem of supplying a permanently safe water can only be solved by the concerted action of the cities along the shore, and possibly aided by the state.

REPORT OF INVESTIGATION OF WATER SYSTEM, FOND DU LAC, WISCONSIN.

By E. J. TULLY, Chemist, State Laboratory of Hygiene, Laboratory of the State Board of Health.

After making a preliminary examination of the immediate surroundings of the water works and conferring with Dean Turneaure in regard to the general conditions, I decided to take three series of samples-two before and one after rain-in order to make the determinations as quantitative as practicable under the circumstances, with the idea of discovering the source of the trouble at once; and, also, to ascertain the effect, if any, of the heavy rainfall on deep well water.

Subsequently I made an investigation of the conditions about the wells and plant in general, and also the sections adjacent to the plant. At the plant I discovered what I believe to be one source of the trouble-the reservoir. The sides of the wooden covering of the reservoir do not come flush with the top of the stone walls of the reservoir, and through this space, during rains, surface material may be washed and dust blown into the stored water; and, also, organic material from the sides and roof of the covering may find its way into the reservoir through this space. I noticed some organic material getting into the water while making an inspection during the rain.

A few blocks from and to the east of the plant are two outcroppings of limestone strata, and in the vicinity of the edge of these surface exposures the sanitary conditions are rather unsatisfactory; in one case there is a considerable accumulation of manure and refuse. During rain, washings from such material might find its way in a more or less direct manner into the well water, if fissures of some considerable extent exist in the

limestone formation; but the well water appears to be free from pollution at this time as indicated in the analyses.

The chemical and bacteriological results of the three series of examinations indicate that the individual wells are free from pollution. The conditions under which the sample from well No. 2 was taken practically vitiate the results of the test; and as well No. 5 is a new one, the water has not yet reached its normal quality, but will undoubtedly do so as the water from the new well No. 4 has already done, in a short time. The findings in these two cases are of no special significance in this particular instance.

It appears, however, that the reservoir water collected either at the reservoir, the tap at the pumping station, or the tap at 88 South Main street has been consistently more or less contaminated, indicating that some foreign matter-probably surface. material and dust, rather than sewage-is gaining entrance to the system at the reservoir.

It would appear from a comparison and analysis of the results that the reservoir needs to be better protected from surface material.

REPORT OF THE SANITARY CONDITION OF THE YAHARA RIVER AND LAKE MONONA ALONG ITS WESTERN SHORE.

By E. J. TULLY, Chemist, State Laboratory of Hygiene, Laboratory of the State Board of Health.

It appears from an analysis of the data derived in this survey that the sanitary condition of the Yahara River and Lake Monona. is satisfactory at the present time. The putrescibility tests and dissolved oxygen determinations, indicating, respectively, the condition of a liquid relative to subsequent putrefaction and prospective nuisance, and the potentiality of a liquid effecting self purification, show that the river and the lake along the western shore from the mouth of the Yahara River to a point near Blount street are in stable condition and well oxygenated.

The mixing of the effluent and river water takes place rapidly and is quite complete a short distance below the outfall pipe; and provided present conditions continue, relative to inflow from Lake Mendota, velocity in the river and quality of the effluent, there is but slight probability of the lower part of the river becoming putrescible and thereby creating a nuisance. If the flow from Lake Mendota were to be considerably diminished the conditions under which a nuisance might develop in the river would depend mainly on the number of days the minimum flow continued, the volume of sewage pumped and the efficiency of the settling tanks. In such a case, however, the river water would be sufficiently purified by dilution with the well oxygenated water of Lake Monona,

The water and sludge of the swamp located southwest of Stondall's residence is highly putrescible, at least during the warm weather, and requires about six to ten times as much Lake Men

dota water to effect stability as is necessary to completely oxidize raw sewage. Most of the mephitic and noxious odors noticed in the vicinity of Patterson street during warm weather very probably emanate from this swampy tract of land.

The western shore of Lake Monona from the mouth of the Yahara river to Blount street was quite free from any sign of sewage contamination. The brownish green scum frequently noticed on the surface of the lake-and often mistaken for sewageis composed mainly of plant life-algae. The septic liquid discharged from the Blount street sewer rapidly becomes oxidized as it passes into the lake, and is rendered entirely stabile and free from odor within a few yards of the sewer.

The bacteriological data indicate that the lake along the western shore is only moderately contaminated-about to the same extent as most surface waters; the quality compares very favorably with the quality of the water of Lake Mendota in the vicinity of the bathing beach near the university gymnasium.

The experiments made on the effluent for putrescibility showed that the dilution necessary to effect stability varied somewhat. The maxium dilution found to be necessary (4 days basis) was 1:40. The average volume of effluent discharged into the river is estimated to be 3,000,000 gallons per day. The amount of Lake Mendota water, therefore, necessary to render this volume of effluent innocuous and stable would be 120,000,000 gallons per day. It would be advisable, however, to have an inflow of 180,000,000 gallons per day in order to take care of fluctuations in the volume and concentration of the effluent.