J8t8. 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



77 



SANITARY IMPROVEMENTS IN THE SEWAGE. 

 ( With Engravings, Plate V.J 



The importance of the sanitary question increases every day, 

 a-nd t}ie large extent of works which will evidently he carried out 

 to ohtain a perfect system of sewage make it of great consequence 

 to engineers to he well informed of the most approved modes of 

 construction. For this reason Me have given copious extracts 

 from the evidence of Mr. Austin and Mr. Phillips, before the Me- 

 tropolitan Sanitary Commission, and to which we beg leave to 

 direct the particular attention of the profession. , 



H. Austin, Esq., C.E., at the request of the commissioners 

 nrade a survey of the Surrey and Kent district of sewers, and gave 

 the following evidence relative to the flat district of Lambeth, the 

 Borough, and Rotherhithe, as shown in the plan, fig. 1, Plate V. 



" There is little doubt that much improvement might be efl'ected 

 in the present system of sevrage, but it could only be carried out 

 Ht vast expense ; and to extend this system over the whole district, 

 so as to render it general and complete, even under such improved 

 arrangements, would not only be ruinous in cost, but the great 

 evils after all would only be lessened, not removed. With a dis- 

 trict so situated, nearly flat, and for the most part several feet under 

 high-water mark, all attempts at providing an adequate natural 

 drainage, direct into the river, must end in failure. Do what you 

 will, it must be a cesspool system still. A small additional current 

 of two or three feet may certainly be obtained in some cases by 

 lowering the outfalls to low- water mark, but the advantage of this, 

 carried over a distance of two miles or more, would scarcely be 

 appreciable, and could be carried out only at immense expense. It 

 appears to be absolute that tliis artificial state of things should be 

 treated artificially, and mechanical appliances brought to bear to 

 lift and discharge the refuse constantly as it is produced. Inter- 

 mittent drainage is somewhat more barbarous than intermittent 

 water supply. It does seem extraordinary, that with the steam- 

 engine applied in almost everv' useful relation of life, its adaptation 

 to this great purpose for the relief of flat districts of towns of its 

 refuse and water should never have been attempted. It was very 

 satisfactory to me to find, on proposing tlie system to Mr. Chad- 

 ^vick, that the idea of its practicability had already been impressed 

 an his own mind, from observation as to the eflicieucy and small 

 expense of pumping, for the purpose of agricultural drainage. We 

 have ample experience as to the facility with which refuse may be 

 pumped, in its application, in several instances, to agricultural 

 purposes. It only remains a question as to the best arrangement 

 of the drainage to realise the object in the most efficient and eco- 

 nomical manner. 



The district to be drained should be apportioned into convenient 

 eections or divisions, the drainage of which would be totally inde- 

 pendent and distinct, converging to the centre of each division 

 with any desired current, and f'rom these centres the liquid would 

 be raised by steam-engines, placed at any convenient point in con- 

 nection with them by pipes. The skeleton plan (fig. 1, Plate V.) 

 of the populous part of the Surrey and Kent district will best ex- 

 plain my meaning, it being understood that the divisions of the 

 district there represented, the position of the centre points or 

 wells, and the situation of the engine power, are only assumed for 

 <|ie purpose of illustration, without at all presuming that they 

 would be the most desirable to adopt. These are matters, the cor- 

 rect determination of which would demand much consideration and 

 study of local circumstances and arrangement. Beyond the con- 

 sideration of these circumstances, the extent of each division 

 would be limited only by the amount of fall that it would be ne- 

 cessary to preserve to allow of a certain maximum size of drain, 

 and the depth of digging that might be thought desirable. 



The most important consideration appears to be the size and 

 material of the drains, and I have founded my calculations on the 

 basis that the maximum size of the main outfall drains should not 

 exceed a dimension that would be conveniently manufactured in 

 pottery clay, so as to allow of the establishment, throuyhout, of a 

 complete system of pipe drainage rather than of brick sewers. I there- 

 fore fix the limit of the largest drain at 2 feet diameter, that being 

 a practicable size to manufacture. Taking then a perfectly flat 

 frrea — which is the worst case for calculation — assuming a total fall 

 of 15 feet from the extreme points to the centre, upon an area of 

 half of a square mile or 320 acres, this will give a current of 1 in 

 £50 as a minimum, and a 2-feet drain, with that fall, will be more 

 than sufiicient to discharge the whole refuse of the densest popu- 

 lation upon that extent of surface, with an improved constant sup- 

 ply of water of 100 gallons per day per house. "With such arrange- 

 ments, there would have to be discharged from each division of 



half a square mile nearly one million gallons per day ; but as by 

 far the largest quantity is used in the busy time, from nine to one 

 o'clock, I calculate a capacity sufficient to discharge the whole 

 quantity in that time. 



It would be essential that these drains should be capable of re- 

 moving also the whole external refuse of the streets and houses. 

 I assume, therefore, that the system should be capable of accom- 

 modating a fall of rain equal to an inch and a-balf in 12 hours, a 

 good soaking quantity that would soon cleanse the whole surface 

 of the streets and houses, and convey away the refuse. This 

 amount being added to the house sujiply of water, the total quan- 

 tity produced at such times in each division would be 200,000 cubic 

 feet per hour. 



The only question for consideration as to fall, would be to fix a 

 safe limit for the total inclination of those continuous lines of the 

 drainage that %vould have to convey the water from the extreme 

 points to the centre. Having decided upon that, the rate of in- 

 clination should be graduated from one end to tlie other ; because 

 the accelerated velocity of the stream, as it would approach the 

 centre outfall, would admit of considerably less inclination of the 

 drainage than at the commencement ; or, on tlie other hand, would 

 admit of a great reduction in the size of the pipes. All the col- 

 lateral or intermediate branch-drains, it will be seen, would have 

 so considerable an amount of fall, as to afford the opportunity of 

 putting them all in of a very small size. 



The engines may be fixed in any spot most convenient and ad- 

 visable, and there need be only one pumping establishment for the 

 whole district (as shown in the skeleton plan, fig. 1), to which 

 main pipes would lead from the several centre wells, precisely as 

 would be practised in raising so much water from a well at a dis- 

 tance. From the engines, one or more discharge-pipes, to convey 

 the whole refuse, would lead to the most convenient outlet in the 

 river, as shown by tlie double dotted line. The arrangement here 

 submitted would offer this great advantage, that the pollution of 

 the whole southern bank of the river would at once be avoided, as 

 the liquid refuse could, with equal facility, he discharged at any 

 spot lower down the ri\er, where no inconvenience would arise 

 from it. Bv-and-bye, wlien the public mind is brought to appre- 

 ciate the value of this material, and to apply it to its legitimate 

 purpose, instead of throwing it away, there w ould be nothing more 

 required than to lay down the distributing-pipes from the engines 

 in the direction of the demand. The discbarge pipe would then 

 serve its proper purpose of a waste-pipe into the river, «lien tlie 

 supply of the liquid exceeded the demand for it, or it would lead 

 into depositing reservoirs. 



I calculate that it would be necessary to provide four times the 

 amount of steam power for the removal of the refuse during wet 

 weather that would be necessary on dry days, and this is the very 

 amount that would probably be necessary to raise the refuse the 

 additional height required for its application to agriculture. 

 Thus, in wet weather, when there would be no demand for the 

 sewage manure, the whole power of the engines would be em- 

 ployed in raising the greater quantity of liquid sufficiently high 

 only for its discharge from the district ; and in dry weather the 

 full power would be engaged in raising the smaller quantity the 

 additional height necessary for its intended application to agricul- 

 ture. The system would so work together very satisfactorily as a 

 perfect whole. 



The cost of this improved system of drainage will not amount 

 to more than one-fourth of the system now pursued in the Surrey 

 and Kent district. This commission has recently given notice of 

 the intended execution of works, involving an outlay of £100,000, 

 to be expended in a few main lines of drainage, which, for the real 

 and important purposes of sewerage — the removal of the liquid 

 refuse from the houses — will be of no earthly benefit to the inha- 

 bitants, but will serve only to obstruct future improvement ; 

 whereas the outlay of this amount on tlie plan proposed would 

 actually suffice for the construction of the entire street drainage, 

 including every court and alley, of more than one half of the most 

 populous part of the district comprised within an area of four 

 square miles immediately south of tlie river. The perfect drain- 

 age of the most crowded district on this system would cost on the 

 average £2 per house, with an annual charge of 2*. per house, for 

 annual expense of engine power. To repay in 30 years, with in- 

 terest, the whole cost of the public or street drainage, together 

 with complete private or house drainage, with stone-ware water- 

 closet basin, and including the above annual charge for entrine 

 power, would involve a rate of 7*. per annum, or about a third of 

 the annual cost of emptying a cesspool, where at all decently 

 kept." 



