Francis Lieber.

Library of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) online

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are placed in the interior of the house, it is troublesome to get at the drains when
required, an I lln closets themselves cannot be sufficiently ventilated. If the closet ia
inside the hou^e, then Brnmah's patent with a I) trap underneath is the only form that
should b:- used; but if the closet is outside, then a leas expensive one with a syphon
earthenware trap may be adopted. It is desirable that the closet should be surrounded
with brick walls, and, in fact, isolated from all other parts of the house. The window
of the closet when inside the house should always reach the ceiling; and a ventilating



Sewage.



378



ehaft is desirable where the closet is much used, and the window must be shut occa-
sionally. The ordinary water that passes into the drains leading from any closet-
such as is discharged each time that the handle is raised is not sufficient to sweep
out thoroughly all the solid matter from the drain-pipes, and therefore a flushing
apparatus at the highest point of all sets of drains is essential, so that a body of
water may be allowed to pass down with a rush at least twice or three times a
week. It is also desirable that the foul air engendered in the drain-pipes them-
selves should have some free outlet into the air at some point where it will not
be injurious. The gas given off under such circumstances is of a very light char-
.acter, and has a great tendency to ascend and draw toward heat. During the
greater part of the year, especially since the system has been introduced of heating
houses by hot air, the temperature of living-rooms is much higher than the atmosphere
outside; a pumping action is exercised upon the drains, or indeed upou any outlet, for
fresh supply. If, therefore, some safety-valve is not provided, the gas will force an
entry either the traps or some imperfection in the joints of the drains. In constructing
the drains from houses jar large public buildings, it is now a well-decided point that
there should be an entirely separate system for the sewage or foul water, apart from
that for rain and surface-water. The reasons are many and obvious, but they
are given more appropriately under the head of the drainage of towns. Stone-
ware pipes are the best material to be used for drains, because they are perfectly
non-absorbent: but in many cases glazed earthenware will answer very well. The
smallest size of pipes of any description that should be used for removing sewage
from a house is fi in. in diameter. This size, then, may be gradually increased
as is necessary, and one of 9 in. will remove the sewage of 500 people. The best, fall to
be given to a sewage-drain is 1 in. in 10 ft.; but all will work well from 1 in. in 5 ft. up
to 1 in. in 60 provided the flushing arrangements are as they ought to be. In order to
keep the drains clean, not less than 10 gal. of water daily should pass down the drain
for every person in the house; while anything over 25 gal. is superfluous. At every 20
yards there should be a pipe laid from which the upper half can be removed, and the
interior inspected at any time, and any stoppage remedied without the necessity of
breaking the pipes. Greasy water, such as is poured down from the kitchen and scul-
lery of a house, is one of the constant causes of such stoppages. The fat, as it cools,
congeals on the sides of the pipes, and forms a hard cake. The best method of pre-
venting this is to form a small cesspool, into which the kitchen water is poured first,
and then to take an overflow through a syphon into the foul drain, so that the liquid
only enters, while the fat can be removed by hand from the cesspool. The sewage-mat-
ter having been thus all thoroughly removed from the house, a sewage-filter should be
built. The solid and liquid matters of the sewage are here mechanically separated, and
the former can be removed from time to time say once in six weeks or two months
while the latter must be passed on for irrigation. It is clearly illegal to pass it into any
stream; and it is apt to become a serious nuisance if anything else is done with it. We
shall treat of the best method of utilizing this liquid under the fourth head. It is always
advisable to get space for all these arrangements on the n. and c. side of a house, when
possible, so as to run no risk of contaminating the air on the s. or hot side of a dwelling;
and if a belt of trees can be placed between the sewage-filter and the irrigated land and
the house, it will also be advantageous.

3. The Drainage oj Towns. Until within the last 40 years, the only drainage which
existed in towns was for the rain-water and surface-water alone, anil the inhabitants
were strictly watched to prevent their passing any sewage matter into these drains. The
introduction of the water-closet, however, gradually increased the water which over-
flowed from the old cesspools to such an extent that it was impossible to prevent over-
flows of this description, and systems of drainage were designed to carry off the whole,
both sewage and rain-water. A very composite system of drainage then arose. Gen-
erally, the bed of some stream or natural rivulet passing through the town was covered
over, and the whole filth passed into that along with the rain-fall of the district. This
Boon was found unsatisfactory, because the flood-waters of the stream were not to be
relied on to keep the channel clean, and so the filth remained festering underneath the
ground, giving off deadly gases in the midst of the population. The next, arrangement
which succeeded to that, system was to plan large drains for the rain and surface-water
and sewage, and still keeping the idea of the size of the bed of a natural stream before
them, engineers thought it necessary to make all the main drains large enough for a man
to pass through them, and keep them clean. Seeing the vast quantify of sand and grit
that was occasionally washed off the streets, something might be said in defense of this
system. Vast numbers of these great main sewers still exist. Into these sewers all the
smaller house-drains were to enter, and the surface-water through street-gratings as
well. The, ordinary water used for domestic purposes, and the occasional rain-falls,
were relied upon to flush those large main sewers; but their great size made this an exceed-
ingly difficult and uncertain process, and they, in fact, became only cesspools elon-
gated. In dry weather, the filth was retained in them to such an extent, that after heavy
rains, chemical analysis showed that the water that was discharged contained frequently
twenty times the amount of human fecal matter per gallon more than it did in dry
weather. This state of matters, added to the fact that long-continued dry weather was



379



Sewage.



always attended by an increase of deaths from typhus and other fevers, clearly shoved
that something more must be done. A further step was then, taken by sanitary engi-
neers. The idea of men passing up the drains was set aside, and the smallest possible
drains "were constructed, until these have arrived at such dimensions as an 18 in. main
drain for a town of 10,000 inhabitants. The rain-fall was still to be relied on to a cer-
tain extent for flushing purposes, but a supplementary assistance was to be given at some
points by flushing with water from the ordinary regular supply of the town. As these
smaller drains were not sufficient to carry off all the surface and rain-water, as well i;s
the sewage, overflow weirs have been provided at certain points, where the excess must
go over, and pass away into some other channel. This is the system now most gen-
erally adopted, and is better than its predecessors; but it is now decided that it, in its
turn, must give way to something better, and the change has commenced. The neces-
sity of dealing with the sewage at the main outfall, and the utilization of it for agricul-
tural fertilization, while, in nine cases out of ten, pumping must be employed to lift the
sewage of a town at the discharging point for such a purpose, have gradually forced
upon us the conviction that the sewage and household water must be kept quite dis-
tinct from the surface-water, subsoil water, and rain-fall.

The outfall of the sewage drain, and subsequent disposal of the filth, are in reality
the first things to be considered. Hitherto, engineers in general have taken the nearest
stream, and polluted it to such an extent, that perpetual law-suits, nuisances, and dis-
eases have been the result. Fever of the worst class is certain to follow the drinking of
water tainted in this manner, and there is scarcely a stream in the interior of the coun-
try which has not been injured more or less from this cause.

Again, where the sewage has been emptied into the sea, tide-locked drains are
objectionable, and the sewage, when mixed with salt water, generally gives off more
stench than ever. "VVe may briefly say that all attempts at deodorization by chemical
processed have hitherto failed, and as far as our present knowledge goes, are not to be
relied upon. The utilization of the sewage on the fields by irrigation is, therefore, the
true solution of the problem, and we must arrive at the simplest, cheapest, most certain,
and most perfect system of accomplishing this. When sewage and rain-fall all go
together in the same drains, as they do in all the older systems, all is uncertainty;
while when the tv.'o are separated, rain and surface-water can be discharged at any
point into the natural water-courses of the country, and a fixed quantity of sewage,
with household and flushing water, would be passed to the main outlet, to be there
dealt with. The opponents of this system say that it is too expensive and troublesome
to plan; that it is unnecessary, as it is sufficient if engineers provide for the dry -weather
flow of the sewage, and use that for irrigation; and That when the overflows come into
action in floods, the whole is so much diluted, that no harm is done to any one. The
advocates of this double system of drainage have proved that the total separation of the
two is the most sanitary system, because the street-gratings and rain-water pipes, which
at present let down the rain-water into the sewage drains, act, in fact, as so many venti-
lating shafts, and discharge the stench in the midst of the inhabitants; while, under a
separate system, the sewage-pipe would be entirely sealed up, and only ventilated at
such places as could .safely be done; that the rain-water as a flushing power ought to be
entirely discarded, as it fails in dry weather, just when it is most wanted; that in wet
weather, and winter again, when the discharging of the sewage on to the surface of
land is carried out, the great quantity of water sent down through the drains by the
present system is agricult urally a serious injury ; that when pumping has to be employed
for lifting the liquid for irrigation, as it is in most cases, .ill is uncertainty, and that no
machinery can be economical and efficient under such circumstances, and that the plan-
ning of the irrigation also becomes difficult to manage, and irregular. "With regard to
the expense, it has been proved that, as the rain-water and surface-water can be dis-
charged at the nearest point, all the drains may be much lessened in- size; and further,
that ^fhe flushing power of the water in the sewace drains will be much more efficient,
while the corresponding lessening of the expense in carrying out the process of utili-
zation will completely compensate any additional outlay that may be incurred in laying
the drains in towns. If we take the case, which is a common one, of a pop. of 10,000
people living upon a sq.m., the first-mentioned system, where rain and sewage-water
go together, would require pumping machinery, in dry weather, of, say, five horse-
power, to lift the liquid; and it would further be necessary, for wet weather, to have
in reserve a lifting power of 150 horses; while, on the separate system, where the sewage
alone would have to be dealt with, the five horse-power engine would be regularly
and constantly employed, and its work would be almost entirely confined to the daytime,'
whereas the other must be ready at any time, and for every emergency. The system of
sending sewage and rain-water together has been hitherto adopted in all towns: but
except in one or two cases where gravitation has been available to utilize the discharge
from the drainage, all engineers have failed to prevent the pollution of rivers, and it. is
obvious that something else must be tried, as that cannot be permitted to go on much
longer. The system of separating the sewage and rain-water has been carried out in
several large asylums and public buildings, many barracks, the town of Eton, and
Windsor castle where every consideration, both of expense and sanitary influence,
was brought to bear on the subject. Reading, Oxford, and several other towns arc fust



Sewage.

following on the same principles, and the results are hitherto most satisfactory. Great
economy has resulted from the process.

4. 2*/ie Utilization of Sewage. The whole of the sewage of a house or town haying
been conveyed away in the manner we have described, the next important step is to
know what to do with it. Above all things, it is desirable to add to the productiveness
of the soil, so as to compensate in some degree for the constant supply we are drawing
from that source.

The liquid nature of sewage, adopting as we may the ordinary amount of dilution in
dry weather at the rate of 25 gals, per head, has been a great obstacle in the way; whil
also the vast quantities of road-grit, and the great gluts of rain that come down along
with the sewage when there is only one system of drains in a town, have upset all
arrangements and calculations. Many attempts have been made, especially at Leicester,
some years ago, to precipitate all the'valuable qualities of the sewage by impregnating
the whole with milk of lime; but the process was unremunerative to those who did it,
as so much sand was precipitated at the same time, that the product obtained was almost
worthless as a manure; while, as the greater part of the ammonia escaped in the water,
the discharging 6f it into any stream was still, strictly speaking, quite illegal. As far as
chemical knowledge can guide us, there seems at present to be no hope in this direc-
tion.

At Edinburgh, again, and at Croydou, the irrigation of land by gravitation has ren-
dered the process a simple one, because the whole has been poured over the land with
many excellent results. These, however, are clearly exceptional cases, and we must
look to pumping as being necessary in by far the greater proportion of towns; while for
the two places we have mentioned, the results would, in all probability, have been better
still if the strength of the sewage had been more concentrated. Agriculturally speaking,
any dilution above 25 srals. per head of the population is not desirable, but is injurious
and expensive to distribute; while, again, human faecal matter is too strong to be applied
to land unless diluted in something like 10 gals, of water. The Chinese teach us an
important lesson in this respect. They place all the solid matter, when they remove it
from the towns, in small wells in their fields, and then take a scoopful and mix it in.
about ten or twelve times its volume of water before they apply it to their crops. If any
one attempts utilizing sewage when mixed with rain-water, and has to pump the whole
all the year through, he will find himself in endless difficulties.

Presuming, then, that we can arrive at a fixed quantity of 20 gals, per head of the
population, or what may be taken as the dry-weather flow of the drainage from a town,
the first step is to pass the whole through a strainer, so that all materials may be inter-
cepted which will be likely to interfere with the pumping, or choke the smaller pipws
used for irrigation. This is necessary, also, because in its unstrained state we cannot
depend upon sewage going down and up again, and so passing over a valley, and the
sphere of operations then becomes more limited.

Great part of the solid matter can also be removed by this process, and common
house-ashes are the best mixing and deodorizing material to facilitate the stuff being
carried away.

A piece of land should then be sought ought, with a slope, if possible, of 1 ft. in 30
at least, and the filtered liquid, which will be full of strength, conveyed either by
pumping or -gravitation to the highest point of that land. Iron pipes should not be
used, if possible; and when the land is very flat, it must be ridged and leveled. From
the highest point of the land selected, the liquid must be conducted by open channels or
through common drain-pipes laid on to the surface to all the different points where it is
wished, and utilized for irrigation. The land adopted should be moderately porous, and
then for every 100 people an acre may be allowed, but this varies much according to the
nature of the soil. The land must be thoroughly drained and prepared. The best crops
to be grown are Italian rye-grass, with alternately crops of vegetables, such as potatoes,
cabbages, rhubarb, mangold. All these will luxuriate on the liquid, and we think we may
safely say that the command of such liquid would be worth to any person \rorn 5 to
10 an imperial acre, according to local circumstances.

Milch cows thrive remarkably well on, this grass, and it has been proved by chemical
analysis that the milk is of the best quality, while the vegetables are also quite whole-
some.

Could such a system be carried out in the neighborhood of all our large towns, th
results would be highly beneficial. The difficulties in the way, principally arising from
ignorance on the subject, have been graat; but to this system, or something like it, there
can be no doubt, before many years, we must come, to prevent pollution of the rivers,
and to make the most of the sources of fertility which are at our command, but which
we are at present recklessly wasting. Many committees have been appointed by thp
house of commons to inquire and take evidence on this subject. In 1857 a commission
was issued by the crown to certain gentlemen, at the head of whom was lord Essex, to
inquire into "the best mode of distributing the sewage of towns, and applying it to
beneficial and profitable uses." This commission went to work principally at Rugby,
and made a vast number of experiments, the general result of which may be stated to be,
that ordinarily diluted sewage may be said to produce such increased crops as to warrant
an agriculturist in giving one halfpenny a ton for it, a ton of water contaiug 224 gallons.



381



Sewage.



The third report was issued in April, 1865, and the following recommendations are
given as the results of their labors:

" 1. The right way to dispose of town-sewage is to apply it continuously to land, and
it is only by sueh application that the pollution of rivers can be avoided.

"2. The financial results of a continuous application of sewage to land differ under
different local circumstances; first, because in some places irrigation cun be effected by
gravity, while in other places more or less pumping must be employed; secondly,
because heavy soils (which in given localities may alone be available for the purposi j
are less fit than light soils for continuous irrigation by sewage.

"3. Where local circumstances are favorable, and undue expenditure is avoide' 1 ,
towns may derive profit, more are less considerable, froni applying their sewage in agn
culture. Under opposite circumstances, there may not b'e a balance of profit; but even
in such cases a rate in aid, required to cover any loss, needs not be of large amount.
Finally, on the basis of the above conclusions, we further beg leave to express to your
lordships that, in our judgment, the following two principles are established for legisla-
tive application: First, that wherever rivers are polluted by a discharge of town-sewage
into them, the towns may reasonably be required to desist from causing that public
nuisance. Second, that where town-populations are injured or endangered in health by
a retention of cesspool-matter among them, the towns may reasonably be required to
provide a system of sewers for- its removal; and should the law as it stands be found
insufficient to enable towns to take land for sewage-application, it would, in our opinion,
be expedient that the legislature should give them powers for that purpose."

It is obvious, however, to any one perusing the above paragraphs, that they are
exceedingly vague, and form but little guide to any one who must go into the question
of whether money invested in utilization of sewage-schemes will pay an adequate return
upon the outlay. The uncertainty attending the dilution of the sewage; the necessity
of making the earth take it at all seasons; the distance that the liquid has to be pumped
have all been such difficulties in the way, that the commission could not well arrive at
any other result than they have done.

Experience has now proved, what was formerly a matter of presumption, that, until
we arrive at fixed quantities, no reliable principles can be laid down that would in all
cases enable us to overcome the difficulties attending the sanitary management anJ
utilization of sewage.

SEWAGE, LIEKXCR SYSTEM OP. The pneumatic system of capt. Licrmir for deal-
ing with the sewage of a town has been in operation for some years on the continent;
and Amsterdam, Leyden, Prague, Dordrecht, St. Petersburg, and some other towns, an}
now either partly or wholly drained on this plan. A town so drained is divided into
districts of from 250 to 1000 acres, according to circumstances. Each of these districts
is again divided into small sewage areas varying from 10 to 50 acres, also according to
local circumstances. These small areas have each an air-tight cast-iron tank, from
which extend along the several streets air-tight pipes of the same material, 5 in. in
diameter, and independent of each other. The closets of the houses are connected by
branches with these pipes.

An air-pump engine, or more usually two or three of these steam engines, are placed
in some central station, and in the under portion of the building air-tight iron reservoirs
are situated, in which a vacuum of about atmospheric pressure is maintained. Pipes,
also air-tight, and called central pipes, connect these reservoirs Avith the street tanks.
Like the outer series, these are 5 in. in diameter, and each pipe has two connections
with its street tank, by one of which only air can be sucked out; but the other dips into
the well of the tank, thus enabling its contents to be removed by suction to one of the
central reservoirs. When a vacuum is made in one of the street tanks, the contents of
the closet pipes are drawn toward it; and on a second vacuum being created, the charge
is drawn into it. This tank is then in due time emptied into a central reservoir by
exhausting the air in the pipe connecting them.

We may state here that, although no water is used for flushing it is found that the
fecal matter is reduced almost from the first to the consistency of thin pulp by the
atmospheric pressure. Now as it is impossible to propel liquid any great distance < long
a horizontal tube simply by air-pressure the air column always breaking through and
destroying the vacuum the pipes require to be set at inclines varying from 1 in 5 to 1
in 250 according to circumstances. This admits of a series of vertical risers being
formed from which the liquid matter can never be altogether removed, and therefore
these form a complete lock-off of one gradient from another, so that the vacuum
cannot be destroyed. The residual liquid in these risers corresponds to the left quan-
tity of water which a pump can never completely remove from a receptacle. When
the apparatus is at rest, this minimum quantity of liquid matter arranges itself partly
in the riser and partly in^the lower end of the sloping pipe.

To show what takes place when there is a much larger amount of excreta to remove
in one direction than in another, we may take the case of two branches from one main
pipe each 100 ft. long, the gradient 1 in 100, and each having a riser of 1 foot. One
of these pipes may havt to deal with a single house producing only 1 ft. of fecal matter;
the other may be connected with a barrack producing 100 times as much. " We have,



Sewage.
Seward.

therefore, in the barrack pipe a mass filling both pipe and riser, and ready on the slight-
est force to discharge into the main or street pipe. On the other hand, in the branch



Online LibraryFrancis LieberLibrary of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) → online text (page 88 of 203)