Types Of Sand Filters - General Filters Inc Humidifiers.
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1891 – 1892. Earlier view of Filter Gallery. Galvanized iron tanks on right may have been used for sludge digestion studies. (Note tanks #10 and #19.)
TANKS FOR FILTRATION EXPERIMENTS (1891-1892) These tanks, inside the long narrow building of the Station, were used to conduct sewage treatment and water purification experiments. The tanks were filled with sands, gravels, and other soils from various locations in the state; the suitability of each material for water and sewage treatment was evaluated. ------------------------------------------------------------------------------------------ A Brilliant Research Plan is Conceived The readers who forget that the Lawrence Experiment Station began its epic-making researches when the biological and chemical sciences were still in their formative stages may conclude that much of the early work wandered off into profitless blind alleys. Not only were the young men of the Mills' staff set to exploring every possible angle of their researches, but they were encouraged to demonstrate the uselessness of many preconceived notions old and new. To demonstrate how small was the role of mechanical straining in the purification of sewage, they built and operated an elaborate series of filters of all degrees of porosity and proved that coarse sands could produce purification as well as the finest silts. To get the most complete information on the role of organic matter in the process of purification, they added to their filters all sorts and all amounts of organic matter (as witness, the body of the dog) and proved that sewage alone contained all the constituents required for a healthy growth of beneficent bacteria. It is not to be wondered at that the Station staff explored so diligently some paths that proved to be blind alleys. These apparently fruitless journeys often ended in what must have been a new concept — chat definitely proved negative results have a highly important place in any research. Related studies of the treatment of sewage before filtration included the addition of chemical coagulants and metal salts and various aeration processes. Some of these explorations are exactly like the partial treatment methods used to this day. They worked with "contact" filters which were simply fill-and-draw tanks containing assorted coarse filter materials; everyone then interested in sewage treatment research was similarly engaged. At the station it was concluded that nitrification could not possibly result from this type of pretreatment and that its value in general was limited. Early in the 90's septic tanks were constructed to take advantage of the effects of putrefaction, and in 1895 staff concluded that septic tanks could be regarded only as a preliminary means of removing solids and could not result in a reduction of bacteria. It is interesting to note that at that time they warned against tanks affording unduly long storage — a mistake still being made very widely today. They early recognized the principle of seeding sewage with septic sewage and that method is still being utilized. Long before the symbol "pH" had been heard of, they corrected the sewage by adding acids or alkalis. Thoroughly investigated was the use of specific cultures of the organisms effective in sewage purification. Though after only a year or two of work the staff had concluded that the organisms were naturally present in all sewage, they continued to investigate the possibilities of accelerating sewage digestion and the stabilization of sludge by artificially prepared cultures of bacteria. Aeration of sewage was studied almost from the beginning; it was allowed to fall through the air, it was pumped against bundles of twigs or wooden or metal buffers; great quantities of air were blown into the bases of trickling filters; filters were operated with alternate upward and downward flow; filters were built with open walls. All of these ideas, which still come to the surface every now and then, were explored and dismissed because they offered no improvement over the type of filter which had been constructed. Much later, in 1910, the use of aeration entered a new and different phase; air was applied to aquaria filled with sewage to see if fish could survive. "Green growth" formed in these tanks, and when the growths were permitted to remain it was found that fish survived without other aeration. So the fish were removed and the carbonaceous matter was oxidated, and nitrification completed. Sewage thus treated was applied to sand filters — later trickling filters, and it was found that now the filters performed at rates even greater than before. The re-use of the sludge from the aerating process was further studied on a larger scale. The recognition of the importance of this returned sludge led to another blind alley, and the aerating tanks were provided with slate "contactors" to bring the new sewage into intimate contact with the sludge. Gradual removal of the slates showed that they were not at all necessary. This aeration process, termed "oxidizing" for the time being, was still rega1903. Rear view of the Lawrence Experiment Station showing filter house and some of the early intermittent sand filters. The mound in the right foreground shows the 1st covered intermittent sand fil
LAWRENCE EXPERIMENT STATION - 1903 Rear view showing filter house and some of the early intermittent sand filters. The mound in the right foreground is the 1st covered intermittent sand filter constructed in 1890. In order to prevent floods, the new laboratory additions were constructed at higher elevation and a protective dike was built adjacent to the Merrimack River. ------------------------------------------------------------------------------------------ Harry W. Clark was the first of the long list of famous scientists t3 dedicate his entire professional career to the Lawrence Experiment Station and the Massachusetts State Board of Health. The young chemist came to the Station at the beginning of the magic year 1888 and ten years later he was put in charge of the work. He continued his direction of the researches until his retirement in 1933) giving forty-five years of pioneering service in the sanitary sciences. He played a leading role in the inception and development of the "activated sludge" sewage-disposal process and carried on an immense amount of work in the treatment of industrial wastes. A contemporary, commenting on Clark's reports, said "Europe is certainly greatly indebted to work done by the Massachusetts State Board of Health." lmhoff is said to have admitted gladly that his development of the lmhoff tank was based upon the findings of the Experiment Station under Clark's direction. During the long years of Mr. Clark's administration of the Station's affairs many other young chemical engineers, biologists, and bacteriologists joined the staff to contribute their skills for a while to the never-ceasing investigations, only to move on to more tempting opportunities coming to them both because of their enhanced understanding and the recognition their connection with the Station brought them. The names of only two will provide some measure of the wide variety of the talents of these many budding scientists — of necessity, going unrecorded here. The then recently graduated sanitarian, Charles-Edward Amory Winslow, began his career at the Station, Today he is acclaimed as the elder-statesman of the world-wide public health movement as well as a revered leader in the National field. Another of the young pioneers was the chemist, Stephen DeMeritt Gage, assistant bacteriologist at the Station, who contributed much to the basic design of sewage treatment plants. A pioneer in the sanitary study of shellfish, his years of patient effort laid the foundation for much of our present ideas for control of the quality of this type of food, so important to New England. He went on to become Sanitary Engineer of the Rhode Island Board of Health and later a renowned and successful sanitary engineering consultant — and a consecrated adviser of other men less well-known than he. As a sort of summing up of the contributions of these men and others, Professor Gordon Fair wrote: "Many of the early studies of water purification and sewage treatment at the Lawrence Experiment Station are counted among the classics of sanitary engineering literature. Some of them were so fundamental and so well conceived that they have continued to be reprinted in books on sanitary engineering for 'half a century. The Lawrence Experiment Station eventually became a mecca for engineers, chemists and biologists interested in the purification of water, the treatment of sewage, wastes, and the control of stream pollution, Most of the important American laboratories for sanitary research, whether supported by federal, state, municipal or university authorities, are linked in one way or another to Lawrence and to the men who moved from Lawrence into engineering practice."
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