Public works . w tank treatment, itis estimated that two-thirds of the total operatingcost is expended on the ImhofT tanks. Here thetotal cost in 1919 for the Imhofif tank was $6,,or $ per million gallons of sewage. The esti-mated cost of operation for the smaller plants rangesfrom $ to $ per million gallons of sew- Table No. 1—Population Served by Imhoff Tanks and Num ber of Tanks in New Jersey, 1911 to 1921 Year 1911 Population 7,000 Number of Imhoff tanks. 1 No. of single-story tanks. 8 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 9,000 12,500 36,000 41,000 44,000 52
Public works . w tank treatment, itis estimated that two-thirds of the total operatingcost is expended on the ImhofT tanks. Here thetotal cost in 1919 for the Imhofif tank was $6,,or $ per million gallons of sewage. The esti-mated cost of operation for the smaller plants rangesfrom $ to $ per million gallons of sew- Table No. 1—Population Served by Imhoff Tanks and Num ber of Tanks in New Jersey, 1911 to 1921 Year 1911 Population 7,000 Number of Imhoff tanks. 1 No. of single-story tanks. 8 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 9,000 12,500 36,000 41,000 44,000 84,000 91,000 100,000 104,000 2 6 12 15 18 23 24 26 34 37 12 17 23 32 35 40 42 43 44 45 in New Jersey since1911. The ten armyone-story tanks con-structed in 1918 havenot been included. Thealarming factor in thiscomparison is the greatincrease in the two-story tank during thelast few years as com-pared with those figuresof the one-storv tank. ?Assistant Sanitary En-gineer. Dept. of Health ofXen- COMPARATIVE EXCAVATION DEPTHS OF SINGLE- STORT . laiHOFF TANKS WITH EQUAL SETTLING CAPACITY 39 age, averaging about$ per milliongallons. Recently an engineer,who had just returnedfrom Germany, statedthat the construction ofImhofT tanks in thatcountry had aboutceased due to the un-satisfactory results ob-tained in operation andthat several municipali-ties were being suedbecause of nuisances 40 PUBLIC WORKS Vol. 52, No. 3 due to odors. He further stated that separate sludgedigestion of sewage was still being followed inGermany, but that it was carried out by other meansthan Imhofif tanks. The first Imhoff tank in New Jersey and one ofthe first in the country was constructed at Chathamin 1911. This installation of 300,000 gallons capacityserves jointly the municipalities of Chatham andMadison. Dr. Imhoff was in this country at thistime and personally inspected and approved the plansand construction of the tanks. It is interesting tonote that they were designed with a
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectmunicip, bookyear1896
