An important consideration, so fur as a sanitary house is concerned, is the getting rid of the waste products known as "sewage", in a manner that shall be expeditious, inoffensive, and economical. The question of sanitary appliances, drains, and traps has been dealt with by other contributors, but the question of the ultimate disposal of the sewage must now be considered

In nearly every town or large community in the United Kingdom, the sewage from the houses now passes by underground conduits or drains drecti into the arterial system of sewers, to be ultimately dealt with in a variety of ways which will be presently described The disposal of the sewage from isolated or country houses is a more difficult problem, which in its turn will also be discussed. Before proceeding to deal with the question of the disposal of sewage from towns, it will be well to consider its composition and quantity.

Section IX. Sewage-Disposal By H. Percy Boulnois

Inst C.E, F. San Inst. Etc Late City Engneer Or Liverpool, Past President Of The Incorporated Of Assoctation Of Minicipal And Sanitary Tuonioi, Past President Of The Northern Branch Of The Sanitary Inspectors' Association Pat President Of The Liverpool Engineering Society Author Of "The Municipal And Sanitary Engineers Handbook" . "Practical Hints On Taking A House", Etc.

Sewage may be described as the various waste products from communities,. mixed with a quantity of water which varies with the supply, and the admittance or otherwise of the subsoil and rain water, and also the habits of the community. The measure of the dry-weather flow may be readily estimated, when the supply of water per head of the population is ascertained, but allowance must be made for subsoil water in those cases where it is admitted, either purposely or accidentally, into the drains and sewers. In addition to which must be added the "manufacturers' waste", which in some special cases is necessarily considerable. The storm-water flow, which is dependent upon the rainfall, is, on the other hand, somewhat difficult to estimate, without a series of observations extending over a considerable period of time, and made with a view to estimate the amount of the rainfall upon the area drained by the sewers; and provision must be made for dealing in some manner with the maximun quantity of water which is likely to reach these sewers.

With regard to the chemical composition and degree of dilution of any sewage this must also necessarily vary in every district, but the late well-known chemist, Dr. C. Meymott Tidy, made the following determination of the excrementitious matter In sewage:

"Every adult male person voids on an average 60 ozs. (= 3 pints) of urine daily. The

60 ozs. containa an average of 253 ozs. of dry solid matter, consisting of-

Urea ••• *•-

5124

grains.

Extractives (pigment, mucus, uric acid), ....

1695

"

Salts (chiefly chlorides of sodium and potassium), ...

4250

"

1106.9

= 2.53 ozs.

"Every adult nude person voids about 1750 grains (or 4 ozs.) of faces daily, of which 75 per cent is moisture. The- dry faecal matter passed daily is therefore about 1 oz. per adult head of the population. Of this dry faecal matter, about 88 per cent is organic matter (of which 6 parts are nitrogen), and 12 per cent inorganic (of which 4 parts are phosphoric acid); of this dry faecal matter, 11 per cent is soluble in water." other experimentalists give about 36 ozs. of urine and 1 ozs. of faecal matter for each person in 24 hours, and Messrs. Wolff & Lehmann, from investigations made with a mixed population of 100,000 persons for a year, give the following result: - 3 ozs. of faecal matter and 26 ozs. of urine per day. It will thus be seen that there is some divergence of opinion as to the average amount of these matters voided daily by an adult, and it is really more important for our purpose to ascertain what is the composition of water-carried sewage. This was determined by the Rivers Pollution Commissioners in their first report as follows:-

Table XXX. Dissolved And Suspended Matter In Sewage In Parts Per 100,000

Description.

Matter in Solution.

Suspended Matter.

Total in Solution and Sus-pention.

Bejel

Mineral

Organic

Total.

Water-closet Towns, •

.

2418

2051

44.69

116.89

Midden Towns,

82.4

17.81

2130

3911

121.51

This shows that there is as a rule only '116 per cent of solid matters, in solution and snspension. in water-earned sewage in this country. It must not, however. be forgotten that this solid matter is of an extremely putrescible character, and hence the danger of untreated sewage, especially in cases where there may be in addition large numbers of dangerous pathogenic bacteria, or disease-germs. The problem is to remove from the sewage and reader innocuous the whole of this decomposable organic matter (small though it is in proportion to the large volume of water in which it is carried), and also to destroy the dangerous germs which are carried in it, and which, if allowed to mix with the air we breathe or the water we drink, become so dangerous to our health end lives.

Up to the present date the following may be taken as the various methods of sewage-disposal which have been tried: -

(1) Outfalls into the sea, estuaries, or large riven: in other words, disposal by dilution.

(2) Treatment of the sewage with various chemicals in tanks or otherwise: in other words, disposal by antiseptic treatment or precipitation.

(3) Filtration through artificial filters of various kinds, or through land: in other words, disposaI by mechanical separation of the solids, and by nitrification.

(4) Broad irrigation: in other words, using the sewage for manurial purposes on land, and at the same time purifying it by filtration and nitrification.

(5) Septic or natural decompositiou : in other words, allowing natural decomposition to act on sewage and to break up and destroy the solids, and allowing nitrification to purify the effluent.