Purifying system. In reference to the disposal of the effluent from an L. R. S. privy, the designers wrote in 1910 as follows:

Disposal of effluent.-(1) Heat: If a suitable (metallic) vessel is provided to receive the effluent, a fire may be built under the vessel and the effluent heated to boiling. Or if a wooden or concrete effluent tank is used, the effluent may be transferred to some other vessel for boiling.

After boiling, the fluid may be safely used for fertilizer under any conditions. Heat disinfection is the only measure which can to-day be recommended unreservedly. (2) Burial: Burial will unquestionably decrease the dangers of spreading infection, but in the present state of our knowledge this method of disposal can not be relied upon as safe. If burial of the effluent is practiced, the fluid should be disposed of not less than 300 feet from and down hill from any neighboring water supply and not less than 2 feet underground, and then only provided the soil itself is a good filter. Burial in a limestone region may contaminate water supplies miles away.

(3) Chemical disinfection: Chemical disinfectants, such as chlorinated lime and certain coal-tar derivatives, have the great advantage of cheapness and can be relied upon to destroy pathogenic bacteria. Our knowledge regarding the action of chemical disinfectants upon the eggs and spores of the various animal parasites is at present very

rudimentary, but so far as results are known, their practicable use does not seem to be so efficient in the destruction of the zooparasitic as of the bacterial infectious organisms. Therefore, pending further investigations, the use of chemically treated excrement as fertilizer should not be regarded as unqualifiedly safe.

(4) Chemical disinfection with subsequent burial: Inasmuch as chemical disinfection can be relied upon to destroy pathogenic bacteria, and inasmuch as burial greatly reduces the danger from animal parasites, a suitable combination of the two methods (chemical disinfection and burial) can be used with reasonable safety.

(5) Sewers: In partially sewered towns, the effluent from these privies may be emptied into the sewers. If conditions are such that the addition of this material to the sewage is dangerous, then the entire sewerage system needs correction.

In this lesson the boiling of the effluent from a septic tank is not recommended, because boiling is advisable mainly for the purpose of destroying the eggs of certain animal parasites and in the North these parasites are not dangerous as they are in the South.

In the quotation given above the recommendation that purifying tile, used, should be laid not less than 2 feet below the surface cannot be successfully followed in any but the very lightest and most open soils. The reason for this is that the useful purifying bacteria on which we depend to keep the soil about the tile sweet and open must be near the surface in order to get air. In this lesson it is recommended that the tile be laid near the surface in some spot from which there is little danger of disease being spread. Of the "Rules for locating purifying tile," on page 157, rule 4 is considered by many well-informed sanitary engineers as being too conservative. In the opinion of these men there is so little danger in locating tiles under gardens or orchards, and there is so much benefit to the crops likely to result from such a practice, that it should rather be recommended than condemned. The writer's feeling is, however, that purifying tiles should not be laid under gardens unless there is absolutely no other location possible, and then they should be laid only at the maximum depth allowable for good operation.

The Kentucky sanitary privy

History. The State Board of Health of Kentucky has been experimenting for several years with a design of three-compartment tank shown in figures 94 and 95. At least two pails of water are to be poured into the tank each day unless drains from the house are led into the tank, in which case other water need not be supplied. With house drains connected, however, some trouble is experienced from odors from the first chamber, so that a vent pipe becomes necessary.

The closet bowl and inlet pipe shown in Fig. 76 form an arrangement which the writer believes to be better than an open-tank arrangement (Fig. 94), because, as previously stated, with a submerged inlet pipe the gases are trapped and prevented from rising. There is of course danger that the inlet tube in Fig. 76 may become fouled; but the design of the

closet bowl there shown, overhanging, as it does, the sides of the tube, will largely prevent this. The closet bowl itself will be fouled occasionally;

FIG. 1

but, since this is to be well painted and is easily accessible, it can be cleaned without difficulty. In this connection, the location of the closet seat in reference to the center of the inlet tube, as specified on page 168, is an important item.

KENTUCKY SANITARY PRIVY

FIG. 95. Details of Kentucky sanitary privy

Septic tanks of several distinct compartments have been very generally advocated in the past; but the experience of the writer has been that tanks of one compartment, if provided with suitable baffles, are efficient. They have the added advantage of being simple to construct, and in designs for homemade tanks simplicity is a very important feature.