Sewage disposal . g in dif-ferent tanks. The results of septic treatment in three English and threeAmerican cities are brought together in the table on page comparing them it will be noticed that the effect on ammonianitrogen varies, this constituent sometimes decreasing appre-ciably, as at Exeter, but generally remaining fairly , as at Worcester, it exhibits a marked increase. Thereactions in the septic tank naturally vary materially with theoriginal composition and age of the sewage. In a very freshsewage there is always a considerable formation of ammonianitrogen by
Sewage disposal . g in dif-ferent tanks. The results of septic treatment in three English and threeAmerican cities are brought together in the table on page comparing them it will be noticed that the effect on ammonianitrogen varies, this constituent sometimes decreasing appre-ciably, as at Exeter, but generally remaining fairly , as at Worcester, it exhibits a marked increase. Thereactions in the septic tank naturally vary materially with theoriginal composition and age of the sewage. In a very freshsewage there is always a considerable formation of ammonianitrogen by the decomposition of more complex organic this process has been completed when the sewage is subjected 146 PRELIMINARY TREATMENT BY SEPTIC PROCESS og d l-B o ,_p lO rt Ci H c CO co >> - .—c OJ H < 2 to co co t^ t^ t--. t^ (M t^ b- CO CC CO *< CO -HiOCOOONCOi-OCOCCiO ?*U5N C5 CO »-< t- CO <N 00 3! s hOhCNNh 00MOONCCN • -(NiC^0503C3COOJC003 ? • CO <N NiOOOSMMO • • 00 CO. h hi m * <S O h-1 pq O e32 ^ GAS PRODUCTION IN THE SEPTIC TANK 147 to septic treatment a decrease in ammonia nitrogen may beexpected in the tank. Albuminoid nitrogen and oxygen con-sumed in each, case fall to one-half or two-thirds of their initialvalue. The evidence accumulated by the Royal Sewage Com-mission indicated that an increase of ammonia nitrogen was thegeneral rule in English septic tanks, while the albuminoid nitro-gen was reduced 38 to 54 per cent at Exeter, 50 per cent atLeicester, and 36 per cent at Birmingham. The oxygen con-sumed was reduced 25 to 33 per cent at Exeter, 50 per cent atAccrington, 50 per cent at Leeds, 36 to 60 per cent at Leicester,and 29 per cent at Birmingham. (Martin, 1905.) Gas Production in the Septic Tank. The gas produced in theseptic tank is a close measure of the amount of organic decom-position. Calmette (1909) calculates that a liter of methanerepresents either grams of albumin or grams of volume of gas
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