WATER SUPPLY AND SEWERAGE AS AFFECTED BY THE LOWER VEGETABLE ORGANISMS.
(Concluded from last week.)
IN considering sewage by itself and not in the way it may affect our water supply, we find it in leeching cesspools, in earth-closets,in tight cesspools, and in the city sewers. The leeching cesspool stands in exactly the same relation to surrounding wells that the sewage discharged into a river does to the purity of the river. If we have a small enough supply of sewage and a great enough distance, we are safe. The earth-closet, when supplied with the proper kind of earth, is a sanitary appliance. The proper kind of earth is a dry loam, or surface garden soil dried without heat, which contains the forms of life that combat the noxious bacteria.
These disease-producing bacteria contained in the exposed sewage are not carried through the air.unless that sewage is first dried, desiccated, and then exposed to the wind. It is harmless so long as it is moist, and tests of the air in some large city sewers show a greater purity than the average wellventilated schoolroom when full of students. These organisms can be carried to us only by contact—the stench-producing organisms are not disease-producing; they are probably intended to keep us away from the foul matter in which they live. Sewer-gas itself, however unpleasant, is no more hurtful than any other gas which reduces the amount of oxygen; and it would be difficult to get a leak of sewer gas into a room from a well-ventilated system of plumbing that would vitiate the atmosphere anything like to the same extent as an ordinary gas burner, which uses during a giver, period at least as much oxygen as eight persons.
Dr. A, C, Abbott, of the laboratory of hygiene of the University of Pennsylvania,during the winter of 1894-95 conducted some experiments upon animals, as to the nature of sewer gas and of the gases arising from decomposing organic material. He took some rats, rabbits, and other animals, especial, ly subject to disease in laboratory experiment, and placed them in glass jars. Over some he passed a continuous stream of sewer gas; over others, gases from decomposing material. This was continued without interruption for five or six weeks, and none of the animals suffered a loss of appetite,nor seemed otherwise any the worse for wear. Disease-forming organisms are not gas-producers. The bacteria of decomposition almost universally produce gases. The parasitic bacteria seldom pro. duce gas. They live on our bodies and in the passages and chambers of our bodies that communicate with the external air. We have a variety which lives in our intestines, that is a gas-producer and which, if introduced into other portions of the body where bacteria do not normally belong, may produce disease. Hut, of the parasitic bacteria, a few are normally disease-producers, and of these normal disease-producers not one is known that produces gas. Even if they did, the gas would not of necessity be poisonous.
What is required of a sewerage system is to take away the noxious material as quickly as possible. Cesspools, therefore, are harmful, unless, tight; in which case the sewage being moist is harmless, though it gives off plenty of gas into the apartments above it. In the same way city sewers, if wellventilated, tight, and properly graded are all right. The only difficulty is where they shaii empty. A city like Buffalo, which has a river at its doors with a current of eight miles an hour, into which it can empty its sewage, and lake Erie from which to draw its water supply, can easily solve the problem. A small town can use the irrigation and sewage farm method. Where land is cheap the farm products will nearly pay the expense of running. This system depends for its success on the bacteria of decomposition,and other vegetation. The experiments of the Massachusetts board of health, already referred to, explain the principles of this system. The works at Freehold, N. J., are a good illustration of this type, The city sewers discharge into a large tank or basin. When this basin is full, the contained sewage is allowed to flow with full head through one of the distributing systems—there being six different fields used in alternation. The discharged sewage, before flowing on to the fields, first flows through a barrier of broken stone, where the algoid vegetation does its destructive work. The alternation of the fields gives this vegetation time to develop—being swamped with food—and the several days’ exposure to the sunlight between the floodings destroys the noxious bacteria that may have escaped the barriers of broken stone.
With respect to house filters—The old charcoal, or a sand filter, might do, if used only one day in four or five, and ex-
posed to air and light during the intermediate days. The wire filtersthat screw on the faucet and reverse are an abomination; the retained bacteria have time to multiply,and are then slowly set free when the filter is reversed, and, after a time, the water passing through in either direction will contain more bacteria than is contained in the same amount of water in the pipe supplying the filter. A pressure filter containing a film of paper pulp to be removed daily might be very effective. As to the earthenware filters—These answer their purpose,if they are sterilized by heat about once in four days. It has been shown by experiment that after this period there are more bacteria contained in the filtrate than in the water that enters the filter. The explanation is that it takes about four days for the bacteria to grow through the pores of the eathenware, and, after this is accomplished, these earthenware walls become a breeding-place. If, however, one removes the earthenware portion and either lays it on the coals till raised to a red heat, or puts it in a steam chamber far half an hour, and repeats this operation every fourth day.the filter will then be perfectly safe. It stands to reason, however, that every city should furnish water that is perfectly safe for all to drink —water properly filtered.