Chapter 5

Where an unobjectionable natural outflow cannot be provided, the irrigation of agricultural lands affords the best relief. The action of vegetation, the oxidation which takes in the upper and well-aerated layers of soil, and the well-known but not yet fully explained disinfecting qualities of common earth, are effective in removing the dangerous and offensive impurities, and in converting them into a more or less important source of fertility. Precisely how far this system may be available during winter, it is not easy to say. While the earth is locked with frost, there must be very little, if any, infiltration; but, as an offset, the action of a low temperature upon the sewage matters will clearly be antiseptic; and it is only necessary to provide against an undue washing away of the surface of the ground during thaws, and against the flowing of the sewage beyond the proper limits.

Generally in the neighborhood of villages it will be easy to find lands over which the delivery may be carried on throughout the year without objection. The sewer, or some form of covered channel, should lead far enough from any public road to avoid offence. From this point it may be led by open gutters to the land over which it is to be spread,--or rather through such a system of surface gutters as will enable us to deliver it at different parts of the field, according to the requirements of the crops, and so as to use fresh land at frequent intervals, leaving that which has been saturated to the purifying processes of vegetation and atmospheric action.

The gutters having been made, it is easy, by the use of portable dams,--of thin boiler-iron, like broad shovels,--which may be set in the course of the flow, to divert the current into any branch channel, or to stop it at any desired part of this channel. All the gutters having sufficient descent to lead the sewage rapidly forward, it is usual to set a dam near the far end of the gutter, and allow the sewage to overflow and run down over the surface until it has reached as far as the formation of the ground and the quantity of the liquid will allow it to spread. This portion having received its due amount of the liquid, the dam is moved to a higher point, and the overflow is allowed to spread over a second area. In this way, step by step, we irrigate all that may be reached by a single gutter. Then the moving of the dam in the main line turns the water into another gutter, and this is proceeded with in like manner. In practice it is found best to begin the overflow at the farthest end of the lowest-lying gutter, working back step by step until the higher parts of the field are reached. It would be better that there should be land enough to require the irrigation of any given area not oftener than once in one or two weeks. The amount required for a given population cannot be determined by any fixed rule,--so much depending on the amount of water used _per capita_, and on the absorptive character of the irrigated soil. In the case of villages, one acre to each five hundred of the population would generally be found ample.

There are several instances of the successful use of a much smaller area than is here indicated, by the use of intermittent downward filtration. The most noted success in this direction is that at Merthyr-Tydvil in Wales, a large mining town, where the allowance is only one acre to each two thousand of the population. There are two filter-beds of light loam over a gravelly subsoil thoroughly underdrained with tiles at a depth of six feet. One of these beds is cultivated with some crop like Italian rye-grass, which bears copious irrigation; and the other by some crop like wheat, which, in the absence of irrigation, will thrive on the fertility left over from the previous season. The volume of sewage is very great, but the action of the six feet of earth in removing its impurities seems to be complete; the water flowing out from the drains having been proved by analysis to be really far purer than the standard fixed by the Rivers Pollution Commission.

It is an important condition of this system that the sewage, where its quantity is small, shall be stored in tanks until a large volume has accumulated, and that it then be rapidly discharged over the soil. There is no objection to an actual saturation of the ground, provided the soil is not of such a retentive character as to be liable to become puddled, and so made impervious. The tanks being emptied, the flow ceases until they are again filled. During the interval, the liquid settles away in the soil, by which its impurities are removed. Its descent is followed by the entrance of fresh air, and the oxidizing action of this, accompanied during the growing season by the purifying effect of the growing crop, leads to an entire decomposition or destruction of all organic matters.

The third system--the distribution of sewage through irrigation-pipes laid at a depth of ten or twelve inches below the surface of the ground--has its efficiency attested by numerous instances in private grounds. I have adopted this system for disposing of the sewage of the village of Lenox, Mass., where there was no other means available short of cutting an outlet, at great expense, through a considerable elevation. This method is an extremely simple one, and is available in every instance where even a small area of land lying slightly below the level of the outlet is to be commanded. The arrangement of the sub-irrigation pipes is easily made: Suppose that in land having an inclination of about one in two hundred, occupied by grass or other growth, a trench be dug twelve inches deep, that there be laid upon the bottom of this trench a narrow strip of plank to insure a uniform grade, and that upon this plank is laid a line of common agricultural land-drain tiles, say two inches in diameter. However carefully these tiles may be placed, there will be at their joints a sufficient space for the leaking out of any liquid they may contain; the tiles being laid either with collars around the joints, or with bits of paper laid over them, to prevent the rattling in of loose earth during the filling. The excavated earth is to be returned to its place, well compacted, and covered with its sod. Suppose this drain to have a cross-section equal to three square inches, and a length of one hundred feet, its capacity will equal about sixteen gallons, or a half-barrel. If this amount of liquid be rapidly discharged into the drain, the inclination being slight, it will at once be filled or nearly filled for its whole length, and the liquid will leak away in tolerably uniform proportion at every joint along the line, and will saturate the surrounding earth. The plan adopted at Lenox, and recommended for all small villages which cannot secure a better outlet, is simply a multiplication of these drains to a sufficient extent.

A description of the manner in which the Lenox work is arranged will illustrate the adaptation of the system to its circumstances. As circumstances vary, the adaptation must be modified. (See Figure 8.)

The main outlet sewer delivers at a distance of about one-half mile from the last junction with a branch sewer. It is a six-inch pipe five feet below the surface of the ground, and it delivers into a flush-tank like that shown in Figure 6, but having a capacity of about five hundred cubic feet. This tank stands at the upper side of a field having an inclination of seven in one hundred. There is a branch from the main sewer, above the tank, supplied with a stop-cock, by which, in case of need, the sewage may be carried on down the hill without going into the tank. The outlet from the chamber below the siphon leads off in another direction down the hill, and has a stop-cock and a branch which will allow its flow to be diverted. The discharge of this diverted stream and the discharge through the branch of the main above the tank, both deliver into a horizontal surface gutter to be well grassed, and lying at the top of the land to be irrigated. By this arrangement, should repairs become necessary in the tank, the flow may be turned into the gutter; or, should it be desired for any reason to use the outflow of the tank for surface irrigation, the second branch outlet will deliver it into the same gutter, where, the outflow being uniform along the whole length of five hundred feet, the stream will pass in a thin sheet off on to the descending ground. The hill-side, immediately below the gutter, is brought to a true grade and covered with grass. As its inclination is much greater than would be admissible for sub-irrigation drains, these are laid _obliquely_ in parallel lines at intervals of six feet from one end to the other over the whole graded slope. These drains are connected at their upper ends with the direct outlet-pipe leading from the siphon chamber. They have an aggregate length of about ten thousand feet. The method of operation is as follows:--

The capacity of the tank is supposed to equal about two days' discharge, or about thirty-five hundred gallons; and the whole capacity of the drains is about half that of the tank, so that the rapid emptying of the whole volume into them will insure their being pretty thoroughly filled from end to end. This arrangement will provide for the saturation of the soil about once in two days, and will leave a sufficient interval between the periods of saturation for the thorough dispersal and aeration of the filth.

The extent to which this system will be interfered with by frost, it is impossible to say. This will probably be less than would be supposed, for the reason that the ground would often be covered with snow, and that the sewage will have sufficient warmth to exert considerable thawing influence. Whenever the discharge of the liquid through irrigation pipes is shown to have become obstructed by freezing, it will only be necessary to divert the flow, and turn it into the surface gutter to be distributed over the ground.

It is possible that in this case, as in the one which has been under my observation for six years past, there will be no interruption of the working because of cold; but, should the interruption become serious, I shall propose the planting of evergreen trees in parallel rows midway between the drains. The protection that would thus be afforded, both by the trees and by the drifting snow which they would gather, would probably keep the ground free throughout the winter. Incidentally to the chief advantage of this system, there will be, so long as the land is in grass, quite an addition to its product.

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There are hundreds of villages, with and without a water supply, where the houses are too scattering and the street lengths too great to make it advisable that the cost of any form of public sewerage should be assumed. In all such villages, the public authority or the active influence of the village improvement association should be exerted to secure a regular and systematic adoption of some more perfect system for the private disposal of household drainage than is usual. Fortunately, the best system is the cheapest.

No form of cesspool, no leaching vault, and no cemented tank, should be allowed under any circumstances. Neither should there be permitted any form of the old-fashioned out-of-door privy with a vault. Every household should be supplied with water-closets or well-arranged earth-closets, to which reference will be made below.

The foul water discharge of kitchen sinks, or of whatever form of slop-sink is used for the water of bedrooms, should discharge into a flush-tank, and should be led from this by a tightly cemented four-inch drain to a tight settling basin in the ground beyond. If water-closets are used, the soil-pipe should deliver into the drain between the flush-tank and the settling basin. The settling basin should be constructed as shown in Figure 9; and this, as well as the flush-tank, the soil-pipe, and the connecting drains, should be amply ventilated. The outlet from the settling basin should be carried by well-cemented vitrified pipes (four-inch) to the connection with the subsoil irrigation pipes. The flush-tank discharging at each operation of its siphon about thirty gallons of liquid, two hundred feet of drain, unless the soil is very compact, will dispose of the whole discharge with sufficient rapidity. The tank being emptied, the flow ceases; and within a very short time the drain becomes empty of its contents, which are absorbed by the sponge-like action of the earth, and are subjected to the combined influence of the roots of plants, and of the concentrated oxygen contained among the particles of the soil. They will soon have their character entirely changed, so that the earth will become purified, and will be ready to receive the next discharge from the tank. In the case of my own drains, after five years of unremitted use, the gradual accumulation of bits of grease and more solid matters obstructed the drains, and there appeared undue moisture about their upper ends. All that was then necessary was to re-open the trenches, and remove, wash, and replace the tiles. This operation cost, for a length of two hundred feet, less than three dollars.

For any ordinary household of six or eight persons, where the water-closet is not used, two hundred feet of drain of this sort will be sufficient. If there are water-closets, it may be well to duplicate the length; and, to provide for the necessary connections to lead the liquid to the drains, we may assume that in all five hundred feet of length will be required. The cost of two-inch tiles at the works, in small lots, and where collars are furnished, is about three cents per foot; and we will suppose that transportation will increase the cost to five cents per foot, making the cost of this item twenty-five dollars. The strips of board (three inches wide) will cost, at a very liberal estimate, five dollars more, and the cost of digging and laying not more than another five dollars; so that the establishment of this means of disposal, under the most liberal allowance of prices, will not exceed thirty-five dollars. Ordinarily, especially where neighbors combine to buy their material in larger quantities, it will hardly exceed one-half of this amount. This, be it understood, is for a complete and permanent substitute for the expensive and nasty cesspool now so generally depended upon in the country.

A piece of ground fifty feet square, having ten rows of tile five feet apart and fifty feet long, will suffice for even a large household with an abundant water supply. For the better illustration of the arrangement of this system, I give in Figure 10 a plan for the work in the case of a lot fifty feet wide, with a depth of open ground behind the house of somewhat more than fifty feet. The leaching drains may safely begin at a distance of even ten feet from the back of the house, requiring for the whole a clear area of only fifty feet by sixty feet. With small households, the length of drain may be very much shortened. In my own case, where water-closets are not used, the total length of irrigation drain is, as before stated, only two hundred feet.

The earth-closet was invented by the Rev. Henry Moule, vicar of Fordington, in England, more than ten years ago. Its progress in England has been considerable, and its introduction there has resulted in a profit to the company undertaking it. In this country it has met with less general favor. Two companies with large capital, after expending all their resources, have been obliged to abandon their attempts to build up a profitable business. Having been actively interested in the enterprise from its inception, and having given constant attention to the merits of the system, I am to-day more than ever convinced that the solution of one of the most difficult problems connected with country and village life is to be sought in its general adoption. The public reports of sanitary officers in England, who have investigated the subject to its foundation, fully confirm every thing that has been claimed by the advocates of the earth-closet, unless perhaps in connection with the incidental question of the value of the product as a manure.

The only thing which now deters the authorities of some of the larger manufacturing towns of the North of England from adopting the dry-earth-system as a means of relief, under the sharp exaction of the law that prohibits their further fouling of water-courses, is the belief that the labor of bringing into the town the enormous amount of earth required to supply such an immense number of closets, and the labor of removing the product at frequent intervals, would be so great as to constitute an insurmountable obstruction.

Prof. Voelcker, in a paper published in the Journal of the Royal Agricultural Society, shows pretty conclusively that even the use of the same earth four or five times over, although perfectly successful in accomplishing the chief purpose of deodorization, fails to add to it a sufficient amount of fertilizing matter to make it an available commercial manure. Extended experience in small villages and public institutions seems to confirm his view, that, if the earth-closet is to be adopted by towns, they cannot depend either on farmers buying the manure, or undertaking the labor of supplying and removing it. It is estimated, that, for a population of one hundred thousand persons, there would be required seventy-five tons of earth per day, to say nothing of heavy refuse matters which would be thrown into the closets, and would increase the amount to be removed. Even the quantity required for a village of a few hundred inhabitants, if it were to be brought in and carried out, would entail a considerable cost for handling.

I have recently concluded an experiment of six years' duration, the result of which seems to show that this objection to the adoption of the earth-closet system may be set aside, or at least reduced to such proportions as to make it unimportant. In the autumn of 1870 I had brought to my house, where only earth-closets are used, two small cart-loads of garden earth, dried and sifted. This was used repeatedly in the closets; and, when an increased quantity was required, additions were made of sifted anthracite ashes. I estimate that the amount of material now on hand is about two tons. We long since stopped adding to the quantity, finding that the amount was ample to furnish a supply of dry and decomposed material whenever it becomes necessary to refill the reservoirs of the closets.

The accumulation under the seats is discharged through simply arranged valves into bricked vaults in the cellar. When these vaults become filled,--about three times in a year,--their contents, which are all thoroughly decomposed, are piled up in a dry and ventilated place with a slight covering of fresh earth to keep down any odor that might arise. After a sufficient interval these heaps are ready for further use, there being no trace, in any portion, of foreign matter nor any appearance or odor differing from that of an unused fresh mixture of earth and ashes. In this way the material has been used over and over again, at least ten times; and there is no indication to the senses of any change in its condition.

A sample of this material has recently been analyzed by Prof. Atwater, at the Connecticut Agricultural Station at Middletown. The analysis shows that it contains no more organic matter than Prof. Voelcker found in fresh earth prepared for use in the closet,--say about two hundred pounds,--nearly all of which organic matter it undoubtedly contained when first made ready for use. In my case, there was an addition, at a moderate calculation of at least, 800 pounds of solid dry matter during the six years' use by an average of four adult persons. Prof. Voelcker's analysis showed that the unused earth contained about twelve pounds of nitrogen. Prof. Atwater's analysis shows that my two tons contained only about eleven pounds of nitrogen. By calculation, the 800 pounds of solid dry matters added in the use of my material contained 230 pounds of nitrogen.

Doubtless the constitution of Prof. Voelcker's sample was somewhat different from the original constitution of my own; but practically, except perhaps for the addition of a trifling amount of residual carbon remaining after the decomposition, they were about the same; and, after being used ten times over, the whole of the 800 pounds of organic matter added, including 230 pounds of nitrogen, seem to have entirely disappeared.

It becomes interesting and important to know what has become of this added matter. That it was absorbed into the particles of the earth, is a matter of course; and the result proves that after such absorption it was subjected to such a chemical action of the concentrated oxygen always existing in porous dry material as led to its entire destruction. Porous substances condense gases--air, oxygen, etc.--in proportion to the extent of their interior surface. The well-known disinfecting action of charcoal--the surface of the interior particles of which equal from fifty to one hundred square feet to each cubic inch of material, and all of which surface is active in condensing oxygen--is due not simply to an absorption of foul-smelling odors, but to an actual destruction of them by slow combustion, so that the same mass of charcoal, if kept dry and porous, will continue almost indefinitely its undiminished disinfecting action.

The earth used in the closet is a porous material, sufficiently dry for the free admission of air or of oxygen. The foulest materials when covered with dry earth at once lose their odor, and are in time as effectively destroyed by combustion (oxidized) as though they had been burned in a furnace. The process is more slow, but none the less sure; and it is clear that in the case of my dirt-heap the foul matters added have thus been destroyed. The practical bearings of this fact are of the utmost importance. Earth is not to be regarded as a vehicle for the inoffensive removal beyond the limits of the town of what has hitherto been its most troublesome product, but as a medium for bringing together the offensive ingredients of this product, and the world's great scavenger, oxygen. My experiment seems to demonstrate the fact that there is no occasion to carry away the product from the place where it has been produced, as after a reasonable time it has ceased to exist, and there remains only a mass of earth which is in all respects as effective as any fresh supply that could be substituted.

The quantity necessary to be provided can be determined only by extended trial. My experiment proves that the amount needed does not exceed one thousand pounds for each member of the household, and that this amount once provided will remain permanently effective to accomplish its purpose.