DISTILLERY WASTES.

The importance of this type of waste water, especially along the Ohio River and its tributaries, early led to consideration of the desirability of some experimental work upon its disposal. It was discovered, however, that there are already in use several methods of treatment, among these being feeding of the wet slop to cattle and vacuum evaporation for the production of a dry feed. It was decided, therefore, as the preliminary step, to make a somewhat extensive study of the efficiency and the economy of the various methods of treatment. A comprehensive report upon this matter, with engineering data, has been prepared.

LABORATORY INVESTIGATIONS.

In addition to the special experimental studies outlined above, the field laboratory at Cincinnati has been engaged in a comprehensive survey of industrial wastes in general, with special reference to securing data on the amount and character of wastes from the more important industries contributing to the pollution of the Ohio River. The data secured are in such form that they may be utilized in determining the extent and character of pollution in other sections, the nature and extent of the industries being stated.

Special investigations have also been conducted with reference to the chemical and biochemical characteristics of these wastes, these matters having important bearing upon the general problem of the self-purification of streams.

Studies have also been conducted upon the diffusion of oxygen through water, an important physical phenomenon having direct bearing on the problem of self-purification.

SEWAGE-DISPOSAL STUDIES.

As in previous years, investigations of sewage disposal have been under the general supervision of Prof. E. B. Phelps, of the Hygienic Laboratory, and the immediate direction of Sanitary Engineer L. C. Frank.

RESIDENTIAL AND SMALL COMMUNITY SEWAGE.

Two experimental plants, one at Chevy Chase, Md., and one at the Hygienic Laboratory, have been operated during the year upon many devices for the treatment of residential sewage. This particular problem is distinctly characteristic and unlike the problem of general city sewage disposal. Among other things, it differs in the greater concentration of organic pollution, less regularity of flow throughout the day, greater freshness of the material arriving at the plant, less available head for disposal apparatus, and the impossibility of utilizing either labor or machinery at the plant.

Among the devices investigated are Imhoff tanks; biolytic tanks; an antiscum tank (of new design); sand, contact and trickling filters; and the lath filter. Of these devices the most satisfactory one which has been sufficiently tested is the Imhoff tank-sand filter combination. Under conditions where such an installation is feasible (and these

conditions are by no means general), this system may be relied upon to give satisfactory results during warm weather and with some care reasonably satisfactory results in the winter. The final outcome, however, is not at all a complete solution of the problem, first, by reason of the unavailability of the sand in many sections of the country, and, secondly, by reason of a considerable labor item and general poorer results in winter.

Recently the prospects for a more general and satisfactory solution have been improved through studies made with the lath filter, a device originating with the health department of the city of Ontario. This device has not yet been sufficiently studied to warrant its recommendation, but gives every indication of fulfilling the essential requirements of this difficult situation.

SANITARY PRIVY.

Experiments with a new type of sanitary privy as designed and operated at the Hygienic Laboratory have not been entirely satisfactory and a similar privy installed at the service hospital at Jackson, Ky., has completely failed. The laboratory privy has been operated continuously throughout the year, and so far as satisfactory disposal of the materials involved has fulfilled the requirements. It has not been possible to operate it, however, without nuisance in the immediate vicinity, especially during the period of flushing. This design has therefore been abandoned and a modified design embodying the same general principle of biolytic treatment in a deep tank is now being developed.

STERILIZATION OF STEAMBOAT WASTES.

Investigations have continued throughout the year upon a device which will automatically sterilize and discharge the toilet wastes from steam vessels and from railway coaches. Special attention has been given to the vessel matter, as this seems to be of most importance. A full scale apparatus has been constructed and was installed at the sewage pumping station of the District of Columbia through the courtesy of the District engineer of sewers. These experiments led to the development of satisfactory mechanical devices for the operation of this apparatus. It also permitted actual tests upon the bacterial efficiency. These tests demonstrated a high degree of both mechanical and bacterial efficiency.

Arrangements were subsequently made through the courtesy of the president of the Lake Carriers' Association, an organization of the freight steamboat companies of the Great Lakes, and the apparatus was transferred to the steamer D. G. Kerr, a cargo vessel of one of these companies. Tests of the mechanical efficiency under actual conditions existing on board were made during several runs of this steamer, and the apparatus was then left in charge of the chief engineer in order to develop any inherent difficulties or uncertainties in its operation. The reports have continued to be satisfactory. It is proposed during the early part of the coming fiscal year to continue observations of the work of this device and to undertake further bacteriological studies of its efficiency under practical conditions. The officials of the Lake Carriers' Association have signified

their willingness to install any reasonably economic device of proven efficiency. The actual operation of this plant under the charge of the steamboat officials will be the best possible demonstration for this purpose.

ACTIVATED SLUDGE EXPERIMENTS.

At the close of the calendar year a communication was received from the former chief engineer of the Baltimore Sewerage Commission, now city engineer of the city of Baltimore, stating that the sewerage commission had ceased to exist and that the cooperative arrangement which had been made with the United States Public Health Service would be discontinued. Since that time the experiments begun at Baltimore have been continued without other assistance from the city than the use of the plant itself and some incidental labor.

On the whole, but little progress has been made in the general problem, although valuable experience has been gained in the important phase of the work dealing with the distribution of the air. Toward the end of the fiscal year authorization was granted for the employment of an assistant sanitary engineer and for the continuation of these experiments.

COMPILATION OF LAWS RELATING TO STREAM POLLUTION.

The service has commenced an examination and analysis of laws and court decisions in this country relating to the pollution of navigable waters. This study was conducted during the past year by Research Attorney S. D. Montgomery. The purpose is not only to summarize the powers and duties, active and potential, of the State and Federal Governments as set forth in existing statutes and court decisions, but to trace the common-law principles that have guided and that may be taken as precedents in fixing authority in these matters.

SEWAGE DISPOSAL AT HIGH POINT, N. C.

Upon request of the State Board of Health of North Carolina, Sanitary Engineer H. R. Crohurst made an investigation of the methods of sewage disposal at High Point, N. C., from July 23 to 27, 1915, and reported possible methods of improvement, which were submitted to the State and local authorities. This city, with a population of about 12,000, disposes of its sewage at two points. One outlet is directly into a small creek, with no treatment at all, the other is into another creek, very narrow at the point of the outlet, where the sewage is treated in a septic tank. Because the sewage was highly colored with dye liquors from industrial plants and because of the small amount of diluting water into which the sewage effluent was discharged the city has been involved in several suits brought by farmers on the brooks below the sewer outlets, who claim damage to the water of the brooks and the land bordering them. The investigation by the service indicated that, with the conditions such as existed at the time of inspection, the sewage lost its color in about 3 miles' flow in the brook, the creek being normal below that point. The lower section of the creek, it was found, occasionally 63887°-H. Doc. 1493, 64-2- 6

overflows its bank, but no offensive conditions due to sewage deposits were discovered.

The report presents three alternatives for improving the conditions in the two creeks. The alternative favored was the following: To extend the present sewers to a point near Carter's Mill, about 2 miles below the present outlets, to carry these lines high enough so that at some future time purification works can be constructed at this point to treat all of the sewage of the city, and to straighten and widen the creek at certain points below the new outlet. Carter's Mill is below the point where most of the nuisance in the brooks is now said to be, and the ditching below this point should prevent flooding of the meadows, which now seems to be the cause of complaint below this point. Even though the city may have to build purification works at Carter's Mill, the report states, the sewage would not have to be so highly purified as if works were constructed at the present outlets.

SEWAGE DISPOSAL PROJECT AT LEXINGTON, KY.

Following a sanitary survey of Lexington, Ky., made in connection with the studies of pollution of streams (see p. 56), the service directed Passed Asst. Surg. W. H. Frost and Sanitary Engineer R. E. Tarbett to confer with and advise the city authorities relative to plans proposed for sewage disposal. In their report, submitted by the bureau to the local authorities, it was recommended, in view of the desirability of avoiding delay in providing adequate sewage disposal for Lexington and for other reasons, that the wisest course would be to proceed with the construction of a plant in accordance with the recommendations of an engineer employed by the city to submit plans for a sewage-disposal system. His recommendations were for a sewage-treatment plant comprising screens, Imhoff tanks, and sprinkling filters. Dr. Frost and Mr. Tarbett recommended, however, that this plant be constructed, in so far as possible, with a view to adapting it later to the use of the "activated sludge " principle, in case that process, after further trial, appears to justify present expectations.

LEPROSY INVESTIGATION STATION.

On November 3, 1915, the director of the leprosy investigation station at Hawaii, Surg. George W. McCoy, was relieved to become director of the hygienic laboratory. He was succeeded by Surg. D. H. Currie. During the year the personnel of the station was reduced by the discontinuance of the assistant director and one unclassified laborer. One bulletin of the "Studies on Leprosy ries has been issued.

LABORATORY STUDIES.

A number of laboratory investigations have been made during the year. The more important of these may be thus summarized:

1. Autogenous vaccines and biological products from acid-fast bacilli isolated from cases of leprosy have been prepared and used, to ascertain if any of these substances, when given to lepers, tend to

arrest the progress of the disease. As yet no favorable results have been obtained.

2. An investigation was carried on to ascertain what effect, if any, iodine and its salts, which cause a softening of the nodules of lepers, have on the production of leucocytosis when injected into rabbits. No appreciable increase in the number of leucocytes in the animals was observed.

3. Because of the similarity of tuberculosis and leprosy, guinea pigs suffering from tuberculosis were given iodine and its salts, but no beneficial effects were noted.

4. A number of complement deflection tests were made, using various antigens, but chiefly extracts from acid-fast bacilli. The object of these experiments was to discover, if possible, some ready and practical means of early diagnosis in obscure cases of leprosy. Results obtained were not constant enough to indicate that this method could be used in routine diagnosis.

5. A number of studies were made on the growth of B. lepræ in symbiosis with other bacteria, and such mixed cultures were used to inoculate some of the lower animals; but these studies were productive only of negative results. A number of animals previously inoculated with leprosy-some of them many months before-were killed and necropsied. No evidence was secured indicating that the acid-fast bacilli obtained directly from leper nodules are capable of infecting laboratory animals.

6. Further attempts to cultivate an acid-fast bacillus morphologically identical with the bacillus of leprosy by the method of Clegg have, in a number of instances, been productive of positive results. On the other hand, attempts at cultivation on ascitic-fluid media and by various methods, such as the addition of Koch's old tuberculin to the leprous material, have failed.

7. A study of Wasserman's reaction with a series of presumably healthy Hawaiians and Hawaiians suffering from insanity in its various forms, in comparison with Hawaiians suffering from leprosy, has been begun.

8. Studies of certain fluid cultures of B. lepra which have been allowed to grow undisturbed for a period of five years (thus offering a possible opportunity for the autolysis of the bacilli) have not, as yet, resulted in securing a substance capable of causing febrile attacks in lepers in the manner that Koch's old tuberculin does in the case both of tuberculous patients and of lepers themselves.

9. Investigations have been begun on laboratory animals to ascertain if a certain copper-cyanide combination, prepared by Prof. Koga, of Kitasato's laboratory in Japan, is curative for tuberculosis in laboratory animals, as claimed.

10. Certain experiments have been conducted to ascertain whether the mechanism of defense of the guinea pig against infections with cultures of B. lepra is cellular or humoral in character. It has been concluded that apparently the most important element in the protection of these animals is the phagocytic action of the leucocyte.

11. Laboratory animals have been inoculated with a tubercle culture of low virulence with the intention of attempting to inoculate them with B. leprae in the coming fiscal year, it being thought possible that their natural immunity might be so weakened by the first