Photo 4.1.28. March 24, 1922. Looking north along the west side of the trickling filter tank, the dosing tank sits above the filter bed. A 10-inch cast iron distribution pipe feeds 6-inch lateral pipes that distribute Imhoff tank effluent across the filter bed. (MWRD photo 8830)

Photo 4.1.29. November 25, 1921. Two circular settling tanks for trickling filter effluent were built south of the trickling filter tank. Looking southeast, reinforcing bars are being set on the outside of the interior form for the wall for the east tank. Part of the conical bottom for the west settling tank can be observed in the right foreground. (MWRD photo 8661)

Photo 4.1.30. July 31, 1923, looking southwest. The east trickling filter settling tank is in operation. Effluent from the trickling filter enters through the pipe and flows to the square baffle in the tank center. From under the baffle, flow proceeds to the peripheral weir. Settling occurs as the flow velocity diminishes upon approaching the weir. (MWRD photo 9913)

Photo 4.1.31. July 31, 1923, looking west. The two trickling filter settling tanks are shown in center mid-depth. The south end of the trickling filter is at right. The farm plots in the foreground are part of a research program to determine the effect of dried sludge application in growing various crops. (MWRD photo 9914.1)

Photo 4.1.32. July 31, 1923, looking northwest. The trickling filter is in full operation. The dosing tank along the west side of the trickling filter tank is raised, allowing gravity flow to the sprinkler heads on the distribution pipes. Pumps in the lower level of the dosing tank raised Imhoff tank effluent to the top of the dosing tank. (MWRD photo 9915)

Photo 4.1.33. January 7, 1924. The temperature dipped to minus 21° F on this date, and the trickling filter kept operating. Until reaching the trickling filter, sewage flow has been underground or in large tanks, minimizing expose to the atmosphere. Hence, the liquid temperature remains well above freezing. The collars of ice will thaw upon return to normal ambient temperatures. (MWRD photo 10419.2)

Photo 4.1.34. June 2, 1922. Preparation of sludge drying beds is underway between Imhoff tank batteries B and C. Looking west, the roller is compacting the base material for the drying bed next to tank 17 in battery C. A row of beds is on each side of the Imhoff tank batteries. (MWRD photo 9125)

Photo 4.1.35. June 2, 1922. Looking north northeast, west of Imhoff tank battery A, side walls have been constructed to contain each drying bed. A track will be laid in each side wall opening to facilitate removal of dried sludge. Dried sludge will be rail hauled to a dump located north on the Imhoff tank batteries. (MWRD photo 9129)

Photo 4.1.36. July 27, 1922, looking west southwest. Sludge drying beds in the foreground lie east of Imhoff tank battery D. Pipes rising out of the Imhoff tank vents convey digested sludge from the lower chambers to the ports in the west wall of the sludge drying beds. The length of time to dry the sludge is weather dependent. Three drying cycles per year was found optimum. (MWRD photo 9338.1)

Photo 4.1.37. June 13, 1923, looking northeast. The foreground shows the first bed in battery B clean and the tracks exposed. The tracks in the second bed can’t be used until the sludge is removed, an inefficient process. Removal of dried sludge from the drying beds became a time-consuming labor-intensive activity at the Calumet Plant. (MWRD photo 9808)

Photo 4.1.38. June 13, 1923. One person had to clean dried sludge off the tracks in advance of backing an empty dump car into the bed. This string of dump cars is loaded and will soon head for the dump north of the plant on District property. The inefficiency of manual sludge removal led to attempts to mechanize the process. (MWRD photo 9809)

Photo 4.1.39. August 30, 1926. The District attempted to improve the efficiency of removing dried sludge from the drying beds by using mechanical equipment. The use of a ladder-type loader, as shown here, was effective moving on a track and lifting dried sludge, but loading into dump cars wasn’t worked out. (MWRD photo 12948)

Photo 4.1.40. December 1, 1927. This helical-type scraper was more effective because it moved the dried sludge to one side of the bed. This device was the forerunner of a homemade machine perfected by the District to move the dried sludge to the side of the drying bed, elevate the sludge, and deposit it into a dump car. The dump car can move with the scraper for efficient loading. (MWRD photo 13632)

Photo 4.1.41. August 30, 1926. The District attempted to improve the efficacy of sludge drying by capturing solar radiation during the long winters. Two drying beds were covered with glass shelters as depicted here. Solar radiation wasn’t much help on the normally cloudy winter days and after two years, the use of glass shelters ceased. (MWRD photo 12942)

Photo 4.1.42. August 30, 1926. Under glass, sludge dried quickly during the summer. It also prevented re-wetting by occasional rain. However, removing the dried sludge was more difficult than on open drying beds, odors were overpowering, and using mechanical equipment was more challenging. Using glass enclosures was not pursued. (MWRD photo 12943)

Photo 4.1.43. July 27, 1922. To experiment with the new activated sludge process, the last two tanks in battery D were modified to act as aeration tanks. Workers are installing an air diffuser pipe in a tank bottom. In addition, the tanks didn’t have upper and lower chambers, and openings in the separation walls allowed sewage to be aerated triple the tank length. (MWRD photo 9342)

Photo 4.1.44. July 27, 1922. In place of the sludge drying beds, two circular settling tanks were built. Each tank had a conical bottom and a rotating scraper to move settled sludge to a center collector. When complete, the tanks will have peripheral effluent weirs and a center baffle to diffuse the inflow from the aeration tanks. (MWRD photo 9343)

Photo 4.1.45. October 3, 1922. The Calumet Plant was in operation, but the activated sludge process was not completed. The operating gallery was built between the aeration tanks and the final settling tanks to house the needed piping and valves to control the activated sludge process. The process was modified later to broaden the experiments. (MWRD photo 9538)

Photo 4.1.46. April 13, 1923, looking southwest. The machinery building is at left and the operating gallery at right. The administration building sits farther back behind the operating gallery. While experiments on the activated sludge process took place in the operating gallery, experiments on different sludge drying methods were underway in the machinery building. (MWRD photo 9686.1)

Photo 4.1.47. June 6, 1923. The experimental unit is being installed in the machinery building. The results of experiments in sludge drying using an Oliver vacuum filter were promising and led to its use at both the Calumet and Stickney water reclamation plants. (MWRD photo 9787)

Photo 4.1.48. June 6, 1923. The machinery building also contained blowers, pumps, and other electrical and mechanical equipment needed for plant operation. This interior view shows the blowers used for aeration in the activated sludge process. (MWRD photo 9789)

Photo 4.1.49. August 24, 1923. A Calumet Plant employee inspects a leaf from the crop of beets on plot 4. The beets were planted on July 20. Samples were taken of the sludge, soil, and plants, and chemical analyses performed to determine the impact of using sludge to grow edible crops. (MWRD photo 9977)

Photo 4.1.50. September 10, 1923. A Calumet Plant employee inspects an ear of corn from the crop on plot 2. The corn was planted on June 26. The District has a long history of studying the beneficial uses of sewage sludge, the potential health risks of doing so, and its environmental impacts. The research continues to the present day. (MWRD photo 10023)

Photo 4.1.51. October 15, 1923. Langdon Pearce, the District’s sanitary engineer, addresses trustees, public officials, and community leaders, explaining the operation of the Calumet Plant, standing on the influent screen chamber. Pearce was a widely respected engineer in the field of sanitary engineering. (MWRD photo 10193)

Photo 4.1.52. March 7, 1929. Once the plant went into operation, maintenance became as important as operation. A locomotive and three empty dump cars arrive at the screen and grit chambers. Cleaning these two steps in the treatment process are an everyday chore and the process was eventually mechanized. (MWRD photo 14464)

Photo 4.1.53. March 7, 1929. It’s critical that all mechanical devices be kept in top-notch running order. District employees, transported by locomotive 1, are repairing the grit tank scraper chain. The grit chamber included a bottom scraping and grit collection system. Plans were underway and construction will start in two years on a larger modern treatment plant for the South Area. (MWRD photo 14466)