In ancient times, human wastes were sometimes (in certain civilizations) placed into storm sewers to be conveyed to either large cesspits (for percolation) or into nearby rivers. For the most part, sewage was disposed of wherever and however: via privies, “behind the bush,” cesspits, cesspools, pipes or troughs away from the homes, etc. These approaches worked for a long time in the new United States -- until, in certain cases, the density of the involved cities and towns evolved to the point that the sewage disposal locations were getting too close to (and/or negatively impacting the taste, odor and quality of) the area’s drinking water supplies.

It is known that some farms were irrigated with sewage in Athens, Greece; in France, some of the most sought after vegetables were grown in gardens watered/enriched at times with human sewage (sometimes with just the solids; other times, with the liquid version). Sewage farming was reintroduced by its use in Bunzlau, Germany, in the early 1600s.

One of the earliest large (and documented) community sewage farming efforts was in England, serving the town of Edinburgh. It was about 400 acres in size and served the town for nearly 100 years during the 1750-1850 era. As England’s cities grew (example: the London area), the countryside’s relatively small streams -- but also including the bigger Thames River -- could no longer bear the burden of all the sanitary sewage. The cholera epidemics of the 1840s-60s began to highlight the need to find another point of disposal. In England, two methods of disposing of the collected sewage evolved:

• The irrigation of land with raw sewage -- where local conditions and availability of suitable land so allowed.
• The precipitation of solids (and some of the dissolved matter) by chemical treatment, and subsequent sedimentation (and, in certain instances for sea coast towns, discharge of the sewage into the sea [or estuary] at a point below the low water level -- they had learned a significant lesson regarding the discharge of large quantities of raw sewage into rivers via the “London/Thames River Incident” in the mid-1800s.)

The general lack of suitable acreage for sewage farming, and/or filtration/sedimentation basins, led, in succeeding years, to the use of septic tanks and trickling filters in England.

The need for advanced methods of treatment/disposal did not exist early on in the United States -- i.e., not until the late 1800s/early 1900s, primarily because of the higher/closer availability of larger rivers and streams to receive and acclimate the sewage, and (in later years, when the “sewage discharge” issue versus the “water source” connection was more fully recognized) the larger areas of land available for sewage farming and/or filtration beds.

Irrigation (in areas where there was a year-round need for water) and filtration were utilized in several areas of the United States, but not to any great extent, until the Blackstone River in Massachusetts was recognized as having been fouled from the introduction of sanitary sewage from the Worcester area. To mitigate the situation, the first extensive treatment plant utilizing chemical precipitation was built in Worcester in 1889-90. This plant served as a model for others in succeeding years.

Disposal of sanitary sewage by dilution (i.e., discharging it into rivers, streams, lakes, or the ocean) continued to be the method utilized by American cities; the ready availability of larger bodies of water facilitated the use of this method. The large rivers in our country made the dilution process of disposal a very common and effective one. It was used by Boston, New York, Philadelphia, and Washington; by the cities situated along the Ohio, Missouri, and Mississippi rivers; and by many others. On our Great Lakes, dilution in the quietly moving waters was also practiced by all of the large cities except Chicago (starting in the late 1890s-early 1900s). The first comprehensive study of the subject (advisability of “dilution” as the “solution to pollution”) was begun by Dr. Rudolph Hering for Chicago in 1887; the results of this study -- that this method still had its applicability -- led to the construction of a drainage canal (to dilute the sewage with water from Lake Michigan) that eventually delivered sewage to the DesPlaines River, which in turn flowed into the Illinois River and on into the Mississippi River.

Sea coast towns/cities seldom utilized sewage disposal methods (in the 1850s-early/mid 1900s) other than dilution, i.e., discharge of the raw sewage to the ocean. However, the location of outlets soon became more important in order to help minimize pollution of beaches. In the case of the Boston main drainage works, special attention was paid to the positioning of the outlets and the temporary storage of the sewage and its release -- only at ebb tide. Later on, the protection of shell fisheries became important too; then, the use of primary treatment (followed by disinfection) began.

“Dilution-as-the-Solution-to-Pollution” really didn’t come under considerable criticism until the 1910-20s. Even then, most engineers/sanitarians still agreed that it was less expensive to obtain good drinking water by filtering sewage-laden river water than it was to treat the sewage (prior to discharge) to the degree that there was no danger of it degrading the receiving water into which it was being discharged. Some sanitarians, however, began to claim that they did not consider it reliable to depend on the continuous/proper operation of a water filtration plant for a continuous supply of good healthful drinking water; it was also necessary (and prudent) to properly treat the sewage prior to its discharge to the receiving body of water. Some feared that if the sanitarians had their way, the towns/cities would be faced with insurmountable fiscal hurdles to pay for the sewage treatment plants that would be required in addition to the water filtration plants.

The following is an excerpt from Metcalf & Eddy’s 1914 text book entitled American Sewerage Practice:

“The sanitary engineer who neglects to work for the best interests of the public health falls short of the full discharge of his professional obligations, but it is wise to keep in mind a fact stated as follows by Engineering News: ‘We know of many instances in which business men distrust engineers and pin their faith to so-called “practical” men, largely because of unfortunate experience with engineers who appeared to think that the question of cost was no part of their concern.’ The legal dangers of attempting to discharge sewage into a small body of water must be considered in the design of sewerage systems. In Sammons vs. City of Gloversville, the New York Court of Appeals decided that although the city exercised a legitimate governmental power for public benefit when it built its sewers, it had no charter rights to discharge sewage into a brook in such a way as to injure the plaintiff’s lands below the point of discharge. Even where a city has statute rights to construct sewers emptying into a creek, whereby a nuisance was created, the Alabama Supreme Court held in Mayor, etc. of Birmingham vs. Land, 34 S. Rep. 613, that the owner of a riparian farm below the sewer outlet was entitled to damages. The Maryland Court of Appeals similarly decided the case of West Arlington Imp. Co. vs. Mount Hope Retreat, 54 Atl. Rep. 982. The fact that a water-course is already contaminated does not entitle other persons to aid in its contamination or prevent those thereby injured from recovering from them damages for the injury; Ind. Sup. Ct., West Muncie Strawboard Co. vs. Slack, 72 N. E. Rep. 879.”

“Broad Irrigation,” “sewage farming,” and “land treatment” are terms for certain operations through which sewage is applied intermittently to land at a (low) rate of flow, such that it does not interfere with the raising or harvesting of the involved crop(s). The method was first used in the United States at the State Insane Asylum near Augusta, Maine, in 1876.

For the most part, these processes were not used all that much in the eastern part of the United States (the significant rainfall in the summer/fall diminished the need for another source of water; the generally shorter growing season and the heightened possibility of the sewage leaving the farming site and making its way to stream/river caused these processes to not be used much in the East). In the West, smaller annual rainfalls, the availability of more remote farm sites, and the generally longer (almost year-round) growing season prompted the need for a steadier source of water and the higher use of these processes.

This method of “disposal”/“treatment” required a large area of suitable land; it was utilized by many municipalities in the interior United States (ones away from the oceans and large rivers) -- particularly, areas with moderate year-round climates. By the 1930s, this method (due to expanding metropolitan areas, growing citizens concerns, etc.) was losing favor.

As of 1912, crops raised on sewer farms included peas, beans, tomatoes, corn, cabbage, alfalfa, fruit trees, etc. As people’s desire for personal hygiene/sanitation increased, their prejudices toward certain vegetables grown on sewer farms increased!

In Los Angeles, California, sewage farming was practiced until about 1905, when a new sewage outfall to the Pacific Ocean went into use (NOTE: Complaints about odors helped speed up the installation of the outfall!). Pasadena, California, had a nearly 300-acre farm in service up to about 1914, when odor complaints caused the change to “fresh” water and the sending of the sewage to the Pacific. Salt Lake City, Utah, and Fresno, California, also had extensive sewage farming activities under way in the early 1900s. But as with most such ventures, population growth, urban sprawl, and an increased concern regarding odors led to the demise of sewer farming (mostly by the 1930s).

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The following denotes the progress made, in the era of 1880-1930, on certain processes that evolved (in the years following the advent/use of sewer farms) to dispose/treat sewage in areas away from oceans/large bodies of water, more specifically:

Intermittent Filtration: The idea was developed in New England as a modified form of broad irrigation, known as “intermittent filtration,” in which raw or settled sewage was applied evenly to the surface of prepared areas of sand or other fine material a few feet in depth (which was underdrained by lines of tile with open joints). The goal was that during its passage through the bed, the sewage was to be purified via the removal, and changing of the organic matter into more stable substances by physical and biological processes working in conjunction with the oxygen present in the matrix of the sand. The process derived its name (basically) from the necessity to intermittently apply the sewage in order that air required for the oxidation of the organic matter could enter the voids of the sand during the dry period. In New England, where soil conditions were favorable, this method was utilized by many towns. The surface area (acreage) required was much less than that needed for sewer farms, but still greater than that needed for the later types of filters. Owing to the still larger acreage required, and the cost of operation, this method was adopted only by small towns -- where conditions were favorable.

Chemical Precipitation: Another early method of sewage treatment was “chemical precipitation”; it involved the addition of lime, lime and sulfate of iron, or other coagulants to form an inorganic floc, which absorbed and, upon settling, carried down with it particles of suspended solids, leaving a relatively clear liquid. The sludge produced was large in volume and quite offensive in character.

The earliest plants utilizing this process were located at Coney Island, New York (put in operation about 1887); at East Orange, N.J., in 1888 or 1889; and at Worcester, MA, in 1890. In 1902, other plants of this same type were built. Due to the incomplete level of purification actually achieved, the high cost of operation, and the large volume of sludge produced, chemical precipitation as a means for treating sewage didn’t stay in favor long. The City of Worcester abandoned this method of treatment in 1925 and put into operation a large Imhoff tank/trickling filter plant.

Septic Tanks: The “settling” of sewage in tanks -- without the use of chemicals -- was practiced for many years (1875-1930s). The combination of the sedimentation of solids and their digestion by bacteria was utilized in the septic tank, the Travis tank, and the Imhoff tank.

The early septic tank was a “sedimentation” tank designed and operated so as to facilitate the decomposition of the settled solids in the absence of oxygen. It was originally believed that nearly complete liquefaction of the suspended solids could be obtained in this manner. Experience proved, however, that the proportion thus liquefied was much less than originally thought. Early tanks were not covered; the resulting odors soon convinced everyone that they must be covered. The treated sewage was black and foul; the difficulties in operation often resulted in the accumulation of a floating mass of scum on the surface of the sewage. This approach involved principles and practices which had long been known and publicly used. Tanks were first used in America at the State Insane Asylum at Worcester in 1876 and later were adopted at other places.
In later years, the use of septic tanks with leach fields became widespread in the rural areas of the United States.

Imhoff Tanks: The data learned from the use of “regular” septic tanks eventually led to the use of a two-story tank in which the processes taking place in the septic tank were “separated,” with settling of the solids occurring in an upper chamber and digestion of the solids going on in a chamber below -- separated from the one above by a sloping partition containing narrow slots through which the solids passed into the lower area.

This tank was initially developed for use in the Emscher District in Germany and was introduced into this country largely through the efforts of Mr. Rudolph Hering.

The earliest plant in America using the Imhoff tank was put into service at Madison-Chatham, N.J., in 1911, and the first large Imhoff tanks were constructed at Atlanta, GA, in 1912. Thereafter, there were many other installations, including ones at Rochester, N.Y.; Fitchburg, Mass.; Cleveland, Ohio; and Philadelphia. The Imhoff tank was an improvement over the earlier versions of the septic process in that the treated sewage was less offensive and the solids could be digested to such a degree that the resulting sludge was “practically” free from odor and readily dewaterable on porous beds. However, in some places, difficulties were experienced due to unfavorable sludge digestion, which resulted in foaming or in excessive scum formation.

Separate Sludge Digestion: It was thought by some engineers that the processes carried out in the two-story Imhoff tanks could be accomplished better in two separate tanks: the solids being settled out in one and drawn or pumped from that basin into a digestion tank. In some cases, the sedimentation tanks were equipped with mechanical devices for the continuous removal of the settled solids.

The earliest attempt at separate sludge digestion (on a large scale) in America was at Baltimore in 1912. The Baltimore experience demonstrated that sludge could be digested in separate tanks. Early on, separate sludge digestion generally resulted in acid fermentation -- accompanied by offensive odors and the production of a foul-smelling sludge. Research at the New Jersey Sewage Experiment Station and at Harvard University indicated the importance of controlling the reaction of the sludge and the advantage which could be secured by maintaining a favorable temperature.

At Plainfield, N.J., experiments relating to this subject were carried out on a large scale, and at Boonton, N.J., a plant was constructed in which provisions were made for collecting and burning the gases from sludge digestion and for utilizing the heat (therefrom) for heating the glass-housed/covered sludge beds and the contents of the plant’s separate sludge digestion tanks.

Contact Beds (the forerunner of the “trickling filter”): Because of the large acreage required and the unavailability of suitable soil for sewer farms (or for intermittent filtration), the development of coarse-grained sewage filters, in the form of “contact beds,” began in England in the early 1890s; they were adopted somewhat later in America. Contact beds consisted essentially of tanks filled with broken stone, coke, or other coarse medium, which were alternately filled with settled sewage and then emptied; periods of several hours were allowed for the beds standing full with sewage and then for the beds to remain empty.

Oxidation and nitrification are brought about by the film of microorganisms growing on the surface of the medium; the oxygen was obtained from the air entering the voids of the material in the tanks during the empty periods. Comparatively few contact beds were actually built in America; most of those were soon replaced by other forms of treatment. This short life was due to the almost concurrent development of trickling filters, which were superior to contact beds in certain respects, the main one being the much larger volume of sewage which could be treated on a unit area of trickling filter (due to continuous flow through the trickling filters).

Trickling Filters: Trickling filters, utilized in England on a large scale prior to their introduction to America, differed from contact beds in that the sewage was distributed more or less uniformly, and continuously, over the surface of the beds of coarse material. A trickling filter was (primarily) a bed of broken stone several feet deep, laid on a concrete floor covered with a system of under-drains. Settled sewage was applied intermittently, at relatively short intervals, to the surface of the trickling filter in the form of fine drops -- by using equally spaced spray nozzles or other devices. As the sewage was sprayed through the air and passed on down through the porous bed, atmospheric oxygen was absorbed and was made available to fuel the biological oxidation of the organic matter. The effluent was usually settled in order to remove humus-like solids which (periodically) escaped from the body of the trickling filter.

The first municipal trickling filter of this type was put into service at Reading, PA, in 1908. By the mid-1920s, trickling filters (and the earlier Imhoff tanks) constituted the type of treatment most generally used in America. The largest installation of such filters was then at Baltimore, where about 30 surface acres of the filters were in use.

The control of odors from/around Imhoff tanks and the trickling filters was a problem for most plants; in the 1920s, the treatment of sewage with liquid chlorine was being given its first consideration, and begat the promise of beneficial results under some conditions.

Activated Sludge: Between 1915 and 1925, the activated sludge process was adopted in a number of places in the United States, Canada, and abroad. The process was the fruit of experiments on the aeration of sewage by numerous American workers, particularly, the investigations conducted at the Lawrence Experiment Station (Massachusetts) in 1912; this led to the work, in England, of Fowler and Mumford in 1913 and of Arden and Lockett in 1914. This treatment consisted primarily of aerating sewage with a mixture of aerated or activated sludge and subsequently allowing the mixture to settle.

Beginning in 1914, the City of Milwaukee conducted what is now recognized as the most extensive large-scale experimental investigation ever carried out in the field of sewage treatment in the early years. Based on the results of those experiments, a plant -- the largest in the world in 1926 -- was constructed at Milwaukee and put into operation in 1925. At that time, there were few activated sludge plants in America; the one at San Marcos, Texas, (built in 1916) was the first. Large plants were later constructed in Houston, Texas; Indianapolis; and Chicago. In Chicago, construction began in 1926 on an activated sludge plant to treat the sewage from a then population of 800,000.

Racks, Grit Chambers, and Screens: In order to protect pumps and other mechanical equipment from clogging and damage, and to simplify and improve the efficiency of various processes of treatment, it soon became general practice to provide preliminary treatment for the removal of trash, mineral matter, and the coarser suspended organic substances. In a few cases, in the early years, equipment was installed for the removal of floating oil and grease.

Cage racks for the interception of trash were constructed at the main drainage pumping station in Boston and put into service in 1884. Grit chambers for the removal of the heavier mineral solids were first implemented at Worcester in 1904. Stationary bar screens (manually or mechanically raked) had been in use for a long time, but only between 1905 and 1910 was there a marked development in fine, moving screens -- cleaned by brushing or flushing. The first of these in America was the Weand screen built at Reading, in 1908. This was followed by the Riensch-Wurl screen at Rochester in 1916 and later by others, such as the Dorrco and Link Belt screens. During the 1910-1925 era, such screens were also used for removing the larger and more easily visible floating and suspended matter -- where more complete treatment was not necessary (such as for “sewer farms”).

Sludge Disposal: One of the troublesome features of sewage treatment has always been the disposal of the solids removed by screening or by sedimentations. Screenings were often/early on taken away and plowed under -- in an effort to utilize their fertilizer value. To a much more limited extent, screenings were also incinerated in the early years. Sludge from septic and single-story settling tanks was generally recognized as being offensive and difficult to dry satisfactorily on beds of sand or similar material. Properly functioning two-story tanks produced sludge which was more easily dried and less offensive. Since rains and freezing weather interfered with the drying of sludge in the open air, drying beds were built with covers, like greenhouse structures, notably at Marion and Alliance, Ohio. At Houston and Indianapolis, activated sludge was lagooned.

During the early years of the treatment of sewage, attempts were made to utilize its manurial value by growing crops on the areas used for broad irrigation (sewer farms). Later, considerable effort was made to utilize the fertilizing ingredients in the sludge resulting from the “chemical precipitation” in sewage. That sludge was dewatered by a common filter press in plants at Worcester and Providence.

In the 1920s, air-dried digested sludge was sold to farmers near Baltimore, Maryland, and Rochester and Schenectady, New York. The value of those solids was small, because of their relatively high water content and resulting low ratio of fertilizing ingredients. In some localities, however, it was profitable for farmers to haul and utilize such sludge, even though a nominal price had to be paid for it.

In the case of activated sludge, the proportion of fertilizing ingredients, particularly nitrogenous compounds, was recognized as being materially greater than was existent in sludges from other processes, a factor that favored the expanded use of this process.

By far the greatest progress in this direction was demonstrated in Milwaukee, where a large plant was built (prior to 1926) for dewatering and drying activated sludge; thereafter, it was converted into a marketable fertilizer -- which was sold under the name of “Milorganite.” At Chicago, also, for several years during this same time era, activated sludge was dewatered, dried, and converted into fertilizer.

Disinfection: Where treated sewage was tributary to public water supplies or where effluent was discharged into tidal waters used for oyster culture, it became customary (in the early 1900s) to disinfect the effluent with chlorine. The first plant for this purpose was at Brewster, New York, where an electrolytic plant for the production of chlorine from salt solution was built in 1892. In 1909, the efficiency of hypochlorite of lime for the disinfection of sewage was demonstrated. Thereafter, Providence soon began using that agent to disinfect the effluent from its chemical precipitation plant. Liquid chlorine was, however, used more widely.

1. Milwaukee: Had one activated sludge plant -- also served some outlying villages.
2. Cleveland: One activated sludge plant, one Imhoff facility and one trickling filter plant (three total).
3. Indianapolis: Operated with plain aeration plant in the winter and activated sludge in the summer.
4. Chicago: Two activated sludge plants in service (north side and southwest) -- each was (in 1940) treating more sewage than any other activated sludge plant in the world. The Southwest Treatment Works was then under construction.
5. Baltimore: Adding activated sludge process to 30-year-old trickling filter facility.
6. Washington D.C.: Had enough “dilution” available in Potomac River to allow them to keep using their then-present clarification process.
7. Buffalo, New York: New plant with chlorination facilities -- to protect source of water supplies at Tonawanda and Niagara Falls. A lot of “dilution” available in Niagara River.
8. New York City: Was operating Wards Island and Tallman’s Island plants (both activated sludge) -- also Coney Island chemical precipitation facility. These (together) served only ¼ of the then-current 8,100,000 population.
9. Pittsburgh, PA: No treatment.
10. San Francisco: Had one small activated sludge facility on-line at the Golden Gate and a new sedimentation plant (with flocculation) at Richmond-Sunset.
11. Seattle, WA: Just put new 8 mgd clarification facility into service.
12. Los Angeles, CA: Had a fine-screening facility at Hyperion, with disposal in the Pacific Ocean. The County Sanitation District (surrounding the city) had just installed clarification plants.
13. Detroit, MI: No treatment, but was nearing completion of then-largest sedimentation plant in America -- still was able to only service ¼ of its $1.6 mil potentially tributary population.
14. Boston, MA: No treatment -- but plans were in the works.
15. Kansas City: No treatment.
16. St. Louis: No treatment -- but the city was “grinding” its garbage before it went into the Mississippi River; that made the pollution even higher in the river (reason for negative score).