The CHEMIST at WORK ROY I. GRADY AND JOHN W. CHITTUM The College of Wooster, Wooster, Ohio
XX. SANITARY CHEMISTRY AS A VOCATION EDWARD S. HOPKINS
Edward Scott Hopkins i s a native of Maryland. He graduated from Milton College and later attended Johns Hopkins University and the Universities of Maryland and Georgetown. I n 1923 Mr. Hopkins entered the service of the city of Baltimore as Principal Sanitary Chemist i n its Bureau of Water Supply. Just recently he has become Acting Filtration Engineer i n the same bureau. He has been a n ofFcer i n the Sanitary Reserve Corps, lieutenant for twelve years and captain since 1936. He is a member of the American Chemical Society, former chairman of the Maryland Section, treasurer and later chairman of the Water, Sewerage and Sanitation Division. He i s now president of the Maryland Water and Sewerage Association. He is the author of various articles and books dealing with different phases of water purification and control and sanitation.
Chemistry in sanitation resolves itself into the control of many processes, as this subject includes water purification, sewage disposal, and trade waste discharge. In most instances utilization of stream waters is involved. With the growth of urban civilization these subdivisions are interlocking, forming a composite science. Those individuals charged with the administration of the many types of treatment plants must possess a broad technical background, together with long experience in the field. Efficient management of such works necessitates a knowledge of chemistry, bacteriology, and engineering. Plant design is fundamentally based upon principles of chemical engineering, and their operation is determined by bacteriological testing. It is expected of the trained laboratory staff, who perform the routine chemical and bacteriological tests, that they continuously keep abreast of their science by technical reading, society memberships, and further study. The usual undergraduate college training is acceptable as prerequisite of a satisfactory background. If special training has been given, the chemical personnel should be qualified in colloidal and physical chemistry. Organic chemistry is of relative importance in this field and biological chemistry, as usually taught, has practically little value. A general course in bacteriological principles with detailed application to sanitary problems is sufficient background for the
average routine investigator. I t frequently happens that a particular individual who has developed as a specialist in a given phase of the field, will become recognized as an authority in that branch. This situation will cause a certain plant or laboratory to stand out as an example for others interested in that portion of the general science. I t cannot he questioned but that chemical engineering, using as its definition the application of engineering principles to chemical problems, is the fundamental
course needed for plant control. The necessary practical engineering can, however, be acquired by the chemically trained man through experience or he can supplement his previous training with formal selected courses. A present outstanding handicap of the science is the lack of chemical advice or training in the design of many existing plants. It must be said in justice to the civil engineering profession that they did the best possible with meager fundamental chemical infopation. It is of interest to note that these conditions are being eliminated in present-day design. The object of water purification is to produce a commodity having a palatable taste, without odor,
taste, turbidity, and free from disease organisms. The principles involved are natural sedimentation in large reservoirs, coagulation by chemical treatment, sand filtration, disinfection by physical or chemical agents, and taste removal by adsorption. A separate phase is
highly technical job requiring personnel. Enumeration and identification of algae and other species of microorganisms is a daily task. The simplest form of sewage disposal is to discharge it into a stream of sufficient capacity to provide dilution of great magnitude. Under these conditions aerobic bacterial action occurs with ultimate stabilization of the waste. The concentration of peoples in urban centers, together with the discharge from industrial activity, has made necessary the use of more complex methods. The initial step in each instance is to screen out the coarse liquids then passing to sedimentation, with or without chemical precipitation. In many instances final discharge of the liquid is through trickling filters
Frounti ~ . - I N T ~ R I O1R. 1 ~ OF ~ h - n i I ~ T E R SMONTE, PLANT,BALTIMORE. MARYLAND. THERE ARETWBNTYEIGHT DIFFERENTUNITS, EACHHAVINGA CAPACITY OF 4,000,000 GALLONSP E R DAY. EACH UNIT COXPRISES OPENINGS. COZLI~CSY of the EIGHT OF THE RECTANGULAR Deparlment of Public Works. Bureau of Waler Supply. Baltimore, Maryland BELLO
hardness reduction by chemical precipitation or base F ~ G U R~.-CHLORENE E WLIGHI' ROOM-MUNTLBG~~LO FILTRAexchange phenomena. TION PLANT.BALLMORE, MARYLAND As routine, coagulation control necessitates frequent determination of turbidity, pH, color, alkalinity, and hardness. The same is true for the softening process. Disinfection requires frequent testing of the agent made of coarse gravel, into a convenient stream. utilized, commonly chlorine. This is determined by Chlorination of this effluent to reduce pntrescibility either the starch-iodide or ortho-tolidine methods. To and to control odors and the presence of flies in these facilitate service to consumers analysis for iron, man- systems is of frequent occurrence. Treatment of the ganese and dissolved oxygen are made, the purpose settled material or sludge is carried on by various being to prevent economic loss through the staining of methods. It may he digested in separate tanks or clothes when laundering, killing of gold fish, and to activated with air or treated by one or more special assure a pleasant tasting water. Complete analysis patented processes. Utilization of the hydrocarbon of the mineral constituents is in constant demand for gases obtained from sludge digestion is a new developinformation relating to generation of steam. Testing ment. of the materials used in the purification process for Control methods require frequent determination of available purity is an important task. suspended solids with additional testing for total and The efficiencyof the filtration and disinfection proces- suspended solids. The suspended solids are, of course, ses is based upon bacteriological tests. They are fre- an approximation of the quantity of material retained quently made, samples being collected every few hours. in the settling tanks. Ammonia and total nitrogen The B Cole-Aerogenes group of organisms is used as the tests are used to obtain knowledge as to the decompoindex of sanitary purity. Inoculation of at least five sition and stabilization rate of the sewage. The biolactose broth tubes per sample with additional plating oxygen demand and methylene blue tests are used to upon differential media, such as eosin-methylene blue determine the stability of the sewage effluent being agar, is routine procedure. If a count of the general discharged into the water course. These tests require o&anisms is to be made additional plat in^ upin pep- considerable skill and experience. In addition, grease, tone agar is carried out. ~ a n u f a c t u r eof mediais-a nitrogen as nitrates, chlorides, and chlorine are
372 routine tests. Bacteriological control is usually limited to the presumptive tests for members of the colon group together with the counting of the acid-forming organisms and the total number present. In conjunction with sludge conditioning by chemical methods, the various tests needed to control coagulation and to determine the sludge characteristics are made. Lime is used extensively to maintain correct reaction balance. Trade waste disposal ranges from controlling the discharge of a small creamery or canning factory to that of the largest industries, such as oil refineries, steel plants, and so forth. The problems are many and varied and can only be solved by cooperative laboratory research on the part of the industry and sanitary authorities concerned. In this type of work a broad, technical, trained background is especially valuable. It is easily shown in the above discussion that the tasks of the plant operator are many and diverse. He must decide and initiate the necessary study upon which the routine tests are laid. Under his direction are instituted new methods of testing or of technical operation. It is frequently necessary to make a complete study of the water-course involved for the
checking of pollution and to inaugurate methods for their elimination. Many conditions of this type are removed a t the source by the plant manufacturing the product through a change in their processes. The waste product is frequently converted into a profitable material. Such recovery is a major phase of trade waste disposal chemistry. I t is seen that bacteriology, chemistry, and chemical engineering must combine to meet these requirements. Only as the laboratory staff is reasonably expert, and when its work can be absolutely relied upon, will i t be possible to successfully solve many of these problems. [Dr. Hopkins calls attention to the comprehensive report covering the details of training for water and sewage plant operators which was published in Industrial and Engineering Chemistry, N m s Edition, 12, 389 (1934). He would amplify these suggestions by emphasizing the importance of analytical chemistrone semester of volumetric and gravimetric is inadequate. His last sentence regarding personal traits is, "Get a complete understanding of the daily school task; do not be one who allows studies to accumulate prior to examinations."]
