ACTIVATED CARBON FOR AIR PURIFICATION IN NEW-YORK-CITY SEWAGE-TREATMENT PLANTS

Odors from New York City's sewage treatment plants are controlled by a ctivated carbon housed in 44 large towers, each holding about 11 tons of carbon. The carbons are impregnated with NaOH or with KOH, or are u nimpregnated but continuously injected with ammonia gas. A study is no w under way in our laboratory to monitor the progressive exhaustion of these carbon beds and to predict their useful lifetimes. The monitori ng tests include a measure of the residual breakthrough capacity of th e carbon for hydrogen sulfide, and an estimate of the remaining capaci ty for physical adsorption of other gases. For the caustic-impregnated carbons the tests include a measure of the actual life-extension that can be realized by the retrofit of ammonia injection without interrup ting the operation of the carbon vessels. A procedure to predict the r esults of in situ regeneration is described.