Art. III.—On the Cleansing of Towns.
[Read before the Wellington Philosophical Society, 30th November, 1878.]
An efficient and economical system of town cleansing is a responsibility that soon forces itself on colonial communities; hence its discussion cannot but be fraught with interest. Even in mere camps the subject is of the first importance to the health of armies, to travellers, or to moving tribes and peoples; an early appreciation of which we have in the laws of Moses.*
That it is not otherwise in New Zealand is evidenced by the various enquiries that have been instituted from time to time, by the measures of the various town councils, and by the reports and papers of engineers. The earliest Sanitary Commission in New Zealand, that I am aware of, was that of Dunedin, in which city it is stated that the death-rate, in the year 1863-4, was 35.3 per thousand. More recent statistics show great variation in different towns and years, as follows:—
|Auckland||in 1875||35.77||in 1877||16.68||per 1,000|
|Wellington||" "||26.01||" "||19.50||" "|
|Nelson||" "||27.39||" "||16.96||" "|
|Christehurch||" "||30.44||" "||15.50||" "|
|Dunedin||" "||22.24||" "||13.87||" "|
Impressed with the weight of the above considerations, during my recent visit to England I took the opportunity of examining the actual state of the sanitary works in several towns either wholly or partially, besides which I obtained personal interviews with the officers of several of the Boards, thus directly obtaining the views that had been arrived at by a full knowledge of
[Footnote] * Deut. xxiii., 12, 13.
their local circumstances and wants. These I found, as will be seen in the sequel, to be very various and often discordant.
First of importance was the drainage of London, and to this I had free access given me by the officers of the Metropolitan Board of Works, whereby I was enabled to inspect the arterial, side, and house-drains, as well as the outfalls some miles below the city. I had also several papers given me describing the same, and to these I shall now refer, quoting first in order from a paper by their engineer.* Here we are informed that the “subject of sewerage received the attention of the Legislature at an early date;” and that “amongst others, a proposal by Sir Christopher Wren for improved drainage, nearly two hundred years ago, is preserved in MS. in the records of the ancient Westminster Commission.”
Again: “Up to about the year 1815 it was penal to discharge sewage or other offensive matters into the sewers. Cesspools were regarded as the proper receptacles for house drainage, and sewers as the legitimate channels for carrying off surface waters only; afterwards it became permissive, and in the year 1847 the first Act was obtained making it compulsory to drain houses into the streets.”
Again: “Prior to the year 1847 sewers were under the management of eight distinct Commissions,” who “carried out (each) its drainage works, frequently regardless of the effect thereby produced upon the neighbouring districts through which the sewage flowed.”
Again: “In the year 1847 these eight Commissions of Sewers were superseded by one Commission termed ‘the Metropolitan Commission of Sewers,” who made “the adoption of the new system of drainage compulsory, so that, within a period of six years, thirty thousand cesspools were abolished, and all the house and street refuse was turned into the river.”
Again: “Similar systems were, about this period, to a large extent adopted in the provincial towns, by which means their drainage has been vastly improved, but the rivers and streams of the country have become very generally and seriously polluted.”
Again: “In 1852 the fifth Commission was issued, (when) fresh plans for intercepting the sewage of the metropolis still continued to be heard before the Commission, and were from time to time examined and reported on without any practical result. In 1854 the author (Sir J. W. Bazalgette) was directed to prepare a scheme of intercepting sewers intended to effect the improved drainage of London.”
Again: “The sixth Commission, formed in 1855, continued to discuss the subject, but without coming to a practical result.” “But it was not alone the anomalies of the old Commissions, &c., which compelled the
[Footnote] *“Main Drainage of London,” by Sir J. W. Bazalgette, M. Inst. C.E.
adoption of a general system of main drainage. The metropolis had suffered severely in the cholera visitation of 1831–2, again in 1848–9, and lastly in 1853–4.” “The places formerly most favourable to the spread of the disease became quite free from it when afterwards properly drained.”
Again: “In designing a system of main drainage these points had to be kept in view—to provide ample means for the discharge of the large and increasing water supply consequent on the universal adoption of water-closets, and of the ordinary rainfall and surface drainage at all times, except during extraordinary storms, and to afford to the low-lying districts a sufficiently deep outfall to allow of every house being effectually relieved of its fluid refuse.”
Again: “For centuries there had existed Sewers Commissions appointed by the Government, and irresponsible to the ratepayers, upon whom they levied rates.” “The author (Sir J. W. Bazalgette) having been appointed engineer to the Metropolitan Board was again instructed to prepare a plan for the drainage of the metropolis;” “and it was through the influence of Lord John Manners that the Board was left free to carry out their system of main drainage.”
Again: “The objects sought to be attained in the execution of the main drainage works were—the interception of the sewage (as far as practicable by gravitation), together with so much of the rainfall mixed with it as could be reasonably dealt with, so as to divert it from the river at London; the substitution of a constant, instead of an intermittent flow in the sewers; the abolition of stagnant and tide-locked sewers, with their consequent accumulations of deposit; and the provision of deep and improved outfalls for the extension of the sewage into districts previously, for want of such outfalls, imperfectly drained.”
Again: “According to the system it was sought to improve; the London main sewers fell into the Thames, and, most of them passing under the low grounds in the margin of the river before they reached it, discharged their contents into that river at or about the level, and at the time of low water only. As the tide rose it closed the outlets and ponded back the sewage flowing from the high ground.”
“The volume of pure water in the river (Thames) being at that time at its minimum rendered it quite incapable of diluting and disinfecting such vast masses of sewage.”
Again: “In the system now adopted it has been sought to remove those evils by the construction of new lines of sewers laid at right angles to those existing, and a little below their levels, so as to intercept their contents and convey them to an outfall fourteen miles below London Bridge.”
“By this arrangement the sewage is not only at once diluted by the large volume of water in the Thames at high-water, but is also carried by the ebb tide to a point in the river twenty-six miles below London Bridge, and its return by the following flood tide within the metropolitan area is effectually prevented.”
Again: “At the threshold of my (Sir J. W. Bazalgette's) enquiry into this subject the following important points required to be solved:
“1st. At what point and state of the tide can the sewage be discharged into the river, so as not to return within the more densely inhabited portions of the metropolis?
“2nd. What is the minimum fall which should be given to the intercepting sewers?
“3rd. What is the quantity of sewage to be intercepted, and does it pass off in a uniform flow at all hours of the day and night, and in what manner?
“4th. Is the rainfall to be mixed with the sewage? In what manner and quantities does it flow into the sewers; and, also, is it to be carried off in the intercepting sewers, and how is it to be provided for?
“5th. Having referred to all these points, how are the sizes of the intercepting and main drainage sewers to be determined?
“6th. What description of pumping engines and of pumps are best adapted for lifting the sewage of London at the pumping stations? So comprehensive a subject, involving not only the above but many other important topics, cannot be fully considered within the limits of an ordinary paper, in which these questions can only be briefly touched upon.”
Experiments by floats were now made on the river Thames, by which it was found that “the excess of the ebbs over the floods was only five miles in four days,” and “that a substance in suspension, works up the river about one mile a day at each high water, as the springs strengthen, and down the river two miles a day as they fall off.” Again: that “the delivery of the sewage at high water into the river at any point, is equivalent to its discharge at low water at a point twelve miles lower down the river; therefore the construction of twelve miles of sewer is saved by discharging the sewage at high instead of at low water.”
The flow of sewage in the drains was then determined by reference to the data afforded by the works of well-known authorities, and it was concluded by the engineer to regard that “a mean velocity of one-and-a-half miles per hour in a properly protected main sewer, when running half full, is sufficient, more especially when the contents have passed through a pumping station,”
In estimating the quantity of sewage to be carried off “provision has been made for an increase of the population up to 30,000 people to the square mile, except over the outlying districts, where provision has been made for a population giving 20,000 to the square mile.” “An improved water supply, equal to five cubic feet, or 31 ¼ gallons per head for such contemplated increased population has moreover been anticipated.”
Again: “How to dispose of the rainfall is a question of considerable difficulty, and has given rise to much diversity of opinion. This arises from the fact that, whilst it is in itself harmless, and even advantageous to the river, it sometimes falls suddenly in large quantities. These considerations have induced theorists to advocate that the rainfall should not be allowed to flow off with the sewage, but should be dealt with by a separate system of sewers. This theory however is most impracticable.”
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Referring to experiments on this subject the result “distinctly establishes the fact, that the quantity of rain which flowed off by the sewers was, in all cases, much less than the quantity which fell on the ground,” also “that ¼ of an inch of rainfall will not contribute ⅛ of an inch to the sewers; nor a fall of 4/10 of an inch more than ¼ of an inch.”
Again: “As it would not have been wise or practicable to have increased the sizes of the intercepting sewers much beyond their present dimensions in order to carry off the rare and excessive thunderstorms, overflow sewers, to act as safety valves in times of storms, have been constructed at the junctions of the intercepting sewers with the main valley lines.”
Again: “Having determined the quantities of sewage and rainfall to be carried off, and the rate of declivity of the sewer required for the necessary velocity of flow, the sizes of the intercepting sewers were readily determined by the formulæ of Prony, Eytelwein, and Du Buat.”
Again: “A primary object sought to be attained in this scheme was the removing as much of the sewage as practicable by gravitation, so as to reduce the amount of pumping to a minimum.” Under this view, on the north side of the Thames, the high level sewer commences at the foot of Hampstead Hill, passing through certain districts of London, draining about ten square miles (shown in the plan), the form of which “is mostly circular, and it waries in size from 4 feet in diameter to 9 feet 6 inches by 12 feet; its fall is rapid, ranging at the upper end from 1 in 71 to 1 in 376, and from 4 feet to 5 feet per mile at the lower end.”
The middle level sewer is as near the Thames as the contour of the ground will allow, the area intercepted being 17 ½ square miles.
The low level sewer intercepts the sewage from the low level area, which contains 11 square miles. “It is also the main outlet for a district of about
14 ½ square miles, forming the western suburb of London, which is so low that its sewage has to be lifted at Chelsea a height of 17 ½ feet into the upper end of the low level sewer. It is tunnelled under the river Lea, on its route to Abbey Mills, where its contents are raised 36 feet by steam power.
Again: “The northern outfall sewer is a work of peculiar construction; as, unlike ordinary sewers, it is raised above the level of the surrounding neighbourhood in an embankment, which has the appearance of a railway embankment, and it is carried by aqueducts over rivers, railways, streets and roads.”
Again: “The Barking reservoir is 16 ¼ feet in average depth, and is divided by partition walls into four compartments, covering altogether an effective area of 412,384 superficial feet, or about 9 ½ acres. The external and partition walls are of brickwork, and the centre area is covered by brick arches supported upon brick piers, the floor being paved throughout with York stone. The reservoir, being almost entirely above the general surface of the ground, is covered by an embankment of earth, rising about 2 feet above the crown of the arches. The ground over which it is built being unfit to sustain the structure, the foundations of the piers, and of the walls, were carried down in concrete to a depth of nearly 20 feet.”
Again: “The Abbey Mills Pumping Station will be the largest establishment of the kind in the main drainage works, providing, as it does, engine-power to the extent of 1140 h.p. for the purpose of lifting a minimum quantity of sewage and rainfall of 15,000 cubic feet per minute a height of 36 feet.”
The Engineer adds that “It is fortunate that these works were not projected in the year 1806 when coal was first introduced into London, and was regarded as such a nuisance that the resident nobility obtained a royal proclamation to prohibit its use under severe penalties; for this pumping station alone will consume about 9700 tons of coal per annum. The cost of pumping is not, however, actually in excess of the former expenditure upon drainage, for the cost of removing deposit from the tidelocked and stagnated sewers in London, formerly amounted to a sum of about £30,000 per annum, and the substitution of a constant flow through sewers by means of pumping must necessarily reduce the deposit, and consequently the annual cost of cleaning.”
Again: “On the south side of the Thames the high-level sewer and its southern branch correspond with the high and middle-level sewers on the north side of the Thames.” “Both lines are constructed of sufficient capacity to carry off the flood waters, so that they may be entirely inter-
cepted from the low and thickly inhabited district, which is tide-locked and subject to floods. The storm-waters will be discharged into Deptford Creek, whilst the sewage and a limited quantity of rain will flow by four iron pipes laid under its bed, each 3 feet 6 inches in diameter, into the outfall sewer.”*
Again: “The main line varies in size from 4 feet 6 inches by 3 feet at the upper end to 10 feet 6 inches, of the same form as the branch by the side of which it is constructed.”
Again: “The falls of the main line are at the upper end 53 feet, 26 feet, and 9 feet per mile to the Effra sewer at the Brixton Road, and thence to the outlet, 2 ⅓ feet per mile. The sewer is erected in brickwork, varying in thickness from 9 inches to 22 ½ inches, that forming the invert being in Portland cement, and the remainder in blue lias mortar.”
Again: “The low-level sewer does not follow the course of the river as on the north side; but commencing at Putney it takes a more direct line through the low ground once forming the bed of the second channel of the Thames, and drains Putney, Battersea, Nine Elms, Lambeth, Newington, Southwark, Bermondsey, Rotherhithe, and Deptford.” The Engineer adds that this district being mostly level was formerly much subject to be overflown, and to stagnation of waters, causing malaria, so much so that “the late Mr. R. Stephenson and Sir W. Cubitt forcibly described the effect of artificial draining by pumping as equivalent to raising the surface to the height of 20 feet. The low-level sewer has in fact rendered this district as dry and as healthy as any portion of the metropolis.”
Again: “The Deptford pumping station is situated by the side of the Deptford Creek, and close to the Greenwich railway station. The sewage here is lifted from the low-level sewer to a height of 18 feet into the outfall sewer. Four expansive condensing rotative beam engines, each of 125 h.p., and capable together of lifting 10,000 cubic feet of sewage per minute to a height of 18 feet, are here constructed.”
Relating to the southern outfall sewer: “The large volume of water met with in the marshes rendered the construction of that portion of the work very costly. These marshes originally formed part of the Thames, and were first enclosed, in the reign of Edward I., by the monks of Lesnes Abbey. Two thousand acres were afterwards flooded by the bursting of the river banks in the reign of Henry VIII., and were not again reclaimed until the reign of James I.”
Again: “The outfall of the sewage at the south side of the Thames is at Crossness reservoir and pumping station. The sewage is discharged into the river at the time of high water only; but the sewer is at such a level
[Footnote] * Written in 1865.
that it can discharge its full volume by gravitation about the time of low water.”
Again: “The maximum quantity of sewage to be lifted by the engines (at Crossness), will ordinarily be 10,000 cubic feet per minute, but during the night that quantity will be considerably reduced—while, on the other hand, it will be nearly doubled on occasions of heavy rainfall. The lift will also vary from 10 to 30 feet, according to the level of the water in the sewer and in the reservoir into which it is lifted.” “The reservoir, which is 6 ½ acres in extent, is covered by brick arches, supported on brick piers, and is furnished with weirs for overflows with a flushing culvert.”
Again: “The specifications provide that the whole of the cement shall be Portland cement of the very best quality, ground extremely fine, weighing not less than 100lbs. to the bushel, capable of maintaining a breaking weight of 500lbs. to the bushel on 1 ½ square inch, seven days after being made in an iron mould, and immersed in water during the intervening seven days.”
Again: “The total cost of the main drainage works when completed will have been about £4,100,000.” “The sum for defraying the cost of these works is raised by loan, and paid off by a 3d. rate levied in the metropolis, which produces £180,262 per annum, the rateable value being £14,421,011, and the principal and interest of the loan will be paid off in forty years.”
“There are about 1,300 miles of sewers in London, and 82 miles of main intercepting sewers. 380,000,000 of bricks and 880,000 cubic yards of concrete have been consumed, and 3 ½ million cubic yards of earth have been excavated in the execution of the main drainage works. The total pumping power employed is 2,380 nominal h.p.; and if at full work night and day 44,000 tons of coals per annum would be consumed, but the average consumption is estimated at 20,000 tons.”
“The sewage of the north side of the Thames at present amounts to 10 million cubic feet per day, and on the south side to 4 million cubic feet per day; but provision is made for an anticipated increase up to 11 ½ millions on the north side, and 5 ¾ millions on the south side, in addition to 28 ½ million cubic feet of rainfall per diem on the north side, and 17 ½ million cubic feet per diem on the south side; or a total of 68 million cubic feet per diem, which is equal to a lake of 482 acres 3 feet deep, or fifteen times as large as the Serpentine in Hyde Park.”
Turning now to the labours of a deputation appointed by the Town Council and Board of Police of the city of Glasgow, to enquire into the methods of disposing of sewage adopted in various towns in England*
[Footnote] * Report dated October, 1877.
we find it stated in the appendix of their Report that—
Leeds has a population of 291,580, covering an area of 21,572 acres. But the town at present sewered covers only about 4,900 acres, with a population of 245,600, thus showing a population of 50 to the acre, while Glasgow has 88.6. The average mortality for the five years—1871 to 1875 inclusive—is 27.4 per 1,000. The number of water-closets in Leeds is 8,500, and of ash-pits and privies 13,000, and about 3,000 of the latter are provided with pails or boxes. Many of the privies have been recently altered into trough water-closets, which are highly approved by Dr. Goldie, the Medical Officer of Health. Originally experimental works were erected to test the efficacy of the A, B, C process, which was in the hands of a Native Guano Company. These works cost about £10,000, and were constructed to treat 2 million gallons of sewage daily. The success of the experiment, so far as producing an apparently good effluent, induced the Corporation to erect works for the chemical treatment of the entire sewage of the town, amounting to nearly 14 million gallons daily, which cost £50,000; but since the works have been in operation practically, it has been found impossible to dispose of the produce in any quantity. As regards undried sludge the farmers in the vicinity refuse to accept it as a gift.
Bradford has a population of 178,000 and covers an area of 7,221 acres, giving a density of population equal to 24 per acre. The average death-rate is 26.1 per 1,000. The number of water-closets is about 2,000, and of dry-closets 3,000. The works for the purification of the sewage are at Manningham, about 1 ¼ miles from the town. The sewage amounts on an average to 9 million gallons per day, and the precipitant used is lime. The quantity employed is about 18 cwt. per million gallons of sewage. The works cost £65,000, and cost of working £5,000 per annum.
Halifax, a town of 68,500 inhabitants, occupies an area of 3,768 acres, giving a density of population equal to 18 per acre. The average mortality is 26.6 per 1,000. The town contains 2,000 water-closets and about 3,300 dry-closets. The sewage amounts to 2 ½ millions of gallons (per diem), and is carried in a culvert to a small beck or burn, which runs through the valley in which the town is situated. Formerly lime was used to defecate the sewage, but this attempt at purification has ceased. The Goux system is here adopted for the dry-closets. Once worked by a company, but at a heavy loss, the Corporation now carry on the works.
Croydon has a population of 63,000, and occupies a space of 10,000 acres, giving a density of population equal to 6.3 per acre—the average annual mortality being 19 per 1,000. The sewage in dry weather amounts
to 2 ½ millions of gallons per diem, and the number of water-closets is about 15,000. The whole sewage is disposed of by irrigation, for which the place is eminently adapted by nature. Crops of rye grass are thus obtained in value £40 per acre. Financially the farm to which the sewage is applied is not a success, the loss per annum varying from £1,012 to £1,700. The Deputation say it is, however, probably the most successful sewage farm in England.
Of London the Deputation remark that the population is 3,500,000; the density per acre being 45.7, and mortality 22.9 (per 1,000). Here also the sewage farms have been unsuccessful, and I need not go over the ground already traversed in the preceding part of this paper.
Birmingham has a population of 375,000, occupying an area of 8,420 acres; density, 44.6 persons to the acre; death-rate, 25.2 per 1,000. The number of water-closets in 1872 was 7,065, but though the population has largely increased since that time, the number of water-closets is now only 7,514. In fact, the use of these is discouraged by the municipal authorities, although not absolutely forbidden. The number of houses in 1871 was 75,000, and since that time 8,420 have been erected, bringing up the present number to 83,420. The number of pan-closets in use in 1876 was 17,000, all the new houses of the smaller class being fitted with these—one closet serving for not more than two houses. Of ordinary privies, at the same date, there were 27,436, and of ash-pits 19,154. The quantity of sewage is from 12 million to 16 million gallons per day, and before being passed into the River Tame it is treated with lime to cause precipitation. The sludge is also treated by a patented process, the annual expense of which, after deducting income from revenue, is £12,000.
The Rochdale system of pails for night-soil, and tubs for ashes is carried out at Birmingham; about 17,000 pans being now in use.
Coventry has a population of 40,000; an average annual mortality of 23.4 per 1,000, and 10 persons to the acre. The water supply is from artesian wells. The present number of water-closets is about 5,000; and privies, 800. The sewage works are about a mile from the town, and the effluent goes into a small stream called the Sherbourne. The sewage is passed through gravel filters before it is let out in the stream. But the system becoming inefficient, works for purification and utilisation were erected at a cost of £14,000. But the company to whom the sewage was conceded had to succumb. The Corporation now carries on the works at a yearly expenditure of about £2700.
Manchester has a population of 356,000; the average death-rate being 30 per 1000. The number of persons to the acre is 83, The river Irwell
separates it from Salford, which has a population of 136,000, and whose death-rate is 29.3 per 1,000, and density per acre, 26.3. There are comparatively few water-closets in Manchester, and they are discouraged as much as possible, and practically forbidden in houses of a smaller kind. There are 42,000 privies, and these are gradually being altered into pan-closets. Already 24,000 have been thus converted; and Dr. Leigh, the medical officer of health, expects that in three years the whole will have been altered. Dr. Leigh calculates that, when all the privies are converted, 6 million gallons of urine annually will be kept out of the sewers, and consequently out of the Irwell, that were formerly allowed to flow into it. Next, the system of removing is entered into, but we pass over this, and only note that about 3,000 tons of material are dealt with weekly, and these consist of—paper, 1 ton; rags, 3 tons; dead animals, 2 tons; stable manure, 2 tons; old iron and tin plate, 33 tons; refuse from slaughter-houses and fish shops, 60 tons; broken pottery, earthenware and glass, 80 tons; vegetable refuse, door-mats, table-covers, floor-cloths, old straw mattrasses and 100 tons fine ashes, 1,230 tons; cinders, 1,400 tons. These are separated, and specially dealt with; and, I may note here that, amongst these, 400 tons of manure is made weekly, and sold at 12s. 6d. per ton.
Oldham was the last place visited by the Deputation. It is a purely manufacturing town, having a population of 88,000, and an annual mortality of 28.2 per 1,000; the density, per acre, being 18.7. The pail system is in general use, and the contents are taken by the Carbon Fertilizing Company, who have purchased the patent for absorbing excrementitious matter by charcoal. The Deputation add that, unfortunately, this patent does not appear to have had a fair trial, the works being in inextricable confusion.
Glasgow.—A few statistics of their own city is added, of which the following, as well as the preceding, are extracts. The estimated population in 1875 was 584,564, and the average mortality 29.9. The area of ground occupied is 6,034 acres; giving an average density of 88.6 persons per acre. The number of dwelling-houses in 1874 was 101,368; and of shops, ware-houses, and factories, 16,218. The water-closets numbered 31,927; sinks, 71,291; fixed basins, 3,865; and urinals, 211. There are, also, at the present date (1878), 6,751 dry ashpits; 1,395 middins or wet ashpits; 3,816 pan-closets; 94 trough-closets (chiefly in public works); and 13 public conveniences, 7 of which are fitted with pans, and 6 with Macfarlane's patent troughs. One hundred and nine manufactories discharge refuse of various kinds into the sewers. And there are 2,304 stables, with 7,024 horses;
and 311 cow-houses, with 1,350 cows. In addition to the factories, the refuse is conveyed into the drains. Twenty discharge direct into the river. The length of the sewers is about 100 miles. Within the city boundary there are at present 131 ½ miles of paved streets, 20 ½ miles of statute labour roads, and 10 miles of turnpike roads; in all 162 miles.
The estimated volume of discharge into the river daily is 40 millions of gallons, exclusive of rainfall, but including the water of the Molindinar and other burns. The total quantity of sewage in wet weather would be about 74 million gallons per day. The water sent into the city and suburban villages (from the waterworks) averages 33 millions of gallons per day. It is distributed to a population of 710,000, so that the volume of water per head was 46 ½ gallons a day.
From the conclusions arrived at, as set forth in the report of the Deputation, we make the following extracts: The question of conservancy of rivers was constantly pressed on their attention, many of the inland towns being compelled, under heavy penalties, to render their sewage clear, in-odorous, and perfectly colourless, and sometimes under manifest injustice. The necessity of a Conservancy Board to watch over the whole drainage area of the various river-basins was constantly dwelt upon by the various authorities, as the only means of solving the important questions which were so intimately connected—the disposal of sewage, and the restoration of rivers to a state of purity. The Deputation state as a fact that the sewage question, in London even, is only partially solved; and in reference to the immediate subject of their attention, viz., Glasgow, the Deputation are of opinion that no sewage works can safely be undertaken till a Conservancy Board has been constituted for the Clyde. They point out at the same time that this city, in respect to area for discharge, is fortunately placed, being into a tidal river, as contra-distinguished from many of the inland cities of England, whose outfalls are into sluggish rivers of small capacity.
They point out that it has never yet been shown that the foul condition of the Clyde is directly injurious to health; and of the mode of dealing with sewage in particular, there are two ways, viz., the dry system, and carriage by water; the first being the most rational as well as consistent with public health and with national prosperity, which, however, has weak points, that while it disposes of excreta, it leaves untouched all other sewage which would still require to be removed by water-carriage, and be purified of course before passing into a river in the same way as if it had contained the whole excreta. While, therefore, they hold that upon economical and sanitary grounds, water-closets in houses—especially in houses of the smaller sort—and in public works, gaols, railway stations, &c., should, as far as possible, be
replaced by an efficient dry system, they do not think that the adoption of this course will very much lessen the amount of sewage to be dealt with, or render its purification less imperative.
When water-carriage is used, the following methods may be employed:—
Running into the sea or into a tidal river, under conditions that will prevent its return.
Purification by precipitation–
The dry method includes—
Stanford's system (Carbon Fertilizing Company).
Lienur's pneumatic system.
In regard to Glasgow, the report notices Messrs. Bateman and Bazalgette's scheme to pump the sewage to a high level and then carry it down to the Ayrshire coast. The plan adopted in London of running the unpurified sewage into the river could not be supported owing to the small current of the Clyde tidal waters.
If the sewage of Glasgow were taken to Farland Point, or to the lands between Irvine or Saltcoats, the scheme would resemble that carried out by Sir J. Hawkshaw for Brighton, whose outfall sewer is about eight miles long; but efficient ventilation would require to be applied to carry off the noxious gases generated.
Of dealing with sewage by irrigation, great hopes were entertained a few years ago that the grand solution had been attained. All this is now changed, owing to general failure. Probably the Beddington Manor Estate at Croydon is the most successful of sewage farms, and the report states that it is no small matter to say that it disposes of the sewage of a population of 60,000 persons at an outlay which is now reduced to a little over £1,000 per annum. But the situation of Croydon adapts it in a peculiar degree to the utilization of its sewage by filtration through land. When the Deputation visited this and other sewage farms the weather was cold, so that no odours of a truly offensive nature were observed; but this is not always so; on the contrary, evidence is adduced to the effect that warm weather makes these exceedingly unhealthy, giving off a most odious stench.
It is right to add, the report continues, that at Edinburgh, Croydon and other places, no evil effects to health have been traced to the influence of the farms irrigated by their sewage; but as to the land itself, sometimes enormous quantities of sewage are applied in season and out of season, till the surfeited land is sick, and even then it has to take more. If the land were obtainable at an ordinary agricultural value, suitable for the reception and distribution of sewage without pumping, a sewage farm might be made to yield a profit.
Regarding chemical treatment, the report states that purification of sewage is possible, and is carried out successfully at Bradford, Leeds, Coventry, Birmingham and other towns, but, so far as the Deputation had been-able to ascertain, the sale of the so-called manure appears to have failed of accomplishment, and this is not to be wondered at, as the processes fail to consume the ammonia and potash salts, which are the most valuable part.
As a precipitant, lime appears to be most capable of universal application, especially if supplemented by some form of charcoal. The A, B, C process was examined, but with unfavourable results, and the manure obtained by this process has a very low market value; the manipulations are also attended with a most nauseous odour.
Intermittent filtration has been carried out quite successfully at Merthyr Tydvil, but the conditions there are so exceptional that there are very few places where the process could be pursued with equally satisfactory results. It appears to be in operation also at Kendal.
Referring to the defects of the water-carriage system, the report points out the decomposition and evolution of sewer-gases, calling for careful ventilation in all cases.
Water-closets should be discouraged in small houses owing to the greater likelihood of their getting out of order. Drainage from stables and byres should be absolutely prohibited, and chemical factories should be under close regulation, as, where the disinfectant is cheap, there can be no hard-ship to the proprietors.
Coming to the dry system as affecting Glasgow, it is stated that the number of houses is 100,000, water-closets numbering only 32,000, showing that half the population is provided with these, the other half being supplied with other conveniences in one form or another of the dry-closet. This branch has therefore occupied much of the attention of the Deputation. In Leeds the old-fashioned privies are being replaced by trough water-closets; in Manchester and Birmingham, on the other hand, water-closets are being systematically repressed, and elaborate attention is being paid to the develop-
ment of dry collection and daily removal. The Deputation strongly commend, on sanitary grounds, the tub and pail system, which opinion has already had wide effects in the City of Glasgow, where the gain in health and decency is great and unquestionable.
The Goux system was in operation at Halifax, but is not recommended on account of its want of simplicity.
The earth-closet is supported as being admirably suited for country houses of the better class, but otherwise it is too costly to work.
Lienur's pneumatic system in operation in Holland, was not inspected by the Deputation, as it had not been adopted in England. However, they advance an opinion that, theoretically, it is perfect, since the whole of the excreta are converted into a highly portable and valuable manure, while all risk of sewer-gases being formed is entirely obviated, and all operations being conducted in vacuo are entirely free from offence. They then quote from a report to the Local Government Board, to wit;— “As, however, the pneumatic only deals with a small fraction of the refuse to be removed from houses, leaving all other forms to be dealt with in the ordinary way, so Dutch town sewage must flow into the rivers and canals, as now, to pollute the water supply, or else some complicated mode of intercepting it must be provided at an additional cost to the local authorities. The pneumatic system is ingenious, but is complicated in its construction and working arrangements, and is liable to derangements which are sometimes difficult to mend. We do not know one English town in which the apparatus, if adopted, would be other than a costly toy.”
The report of the Glasgow Deputation concludes with the following recommendations, viz.:—
1. That the system of having water-closets for public works, factories, gaols, workhouses, infirmaries, and railway stations, should be forbidden, so as to reduce the quantity of water-closet sewage now turned into the river (Clyde); water-closets in small houses should also be discouraged.
2. That ordinary privies and ashpits be altered to the tub and pail system, to be cleansed daily, as it has been carried out in Manchester and other important English cities and towns, and that special accommodation be provided for children.
3. That all drains, soil and waste-pipes, and all apparatus connected with water-closets, sinks and baths, and their connections, be constructed under public supervision.
4. That a complete system of ventilation of the common sewers throughout their entire length be immediately adopted.
5. That a system of ventilation of the house-drains and soil-pipes, inde-
pendent of the common sewers, be immediately adopted and enforced throughout the city.
6. That the use for domestic purposes of water from cisterns supplying water-closets be absolutely forbidden.
In the event of it being found necessary to purify the river–
7. That the whole drainage of the city be taken into main intercepting sewers, and conducted to a suitable point; and, after having been rendered clear by precipitation and filtration, passed into the Clyde.
8. That the sludge obtained in the precipitation process be got rid of in the cheapest possible manner. A part of it might be utilized in making up waste land, and a certain quantity might be taken away by farmers, but the greater part would probably require to be disposed of in the same manner as the dredgings of the rivers.
The report entirely discards the idea of utilization of the sewage itself, or the precipitate obtained by the action of lime or other chemical agents. The sludge obtained by many of the patented processes is dried at such cost, and its value when dry so trifling, that all hopes of disposing of it for manurial purposes–at a price that would be remunerative—is entirely illusory.
The report concludes that, while they consider the purification of the Clyde important, yet for the health of the city, the sewage works are of greater consequence, which they hope will be carried out without unnecessary delay.
Attached to the Glasgow report are appendices containing the opinions of the Local Government Board, and the Health and Sewage of Towns Conference Committees, which closely coincide with the above in their recommendations, and they pointedly insist “that no one system for disposing of sewage could be adopted for universal use; that different localities require different methods to suit their special peculiarities; and also that, as a rule, no profit can be derived at present from sewage utilization, but for health's sake, without consideration of commercial profit, sewage and excreta must be got rid of at any cost.”
“That the pail system, under proper regulations for early and frequent removal, is greatly superior to all privies, cesspools, ashpits, and middens and possesses manifold advantages in regard to health and cleanliness; whilst its results in economy and facility of utilization often compare favorably with those of water-carried sewage.”
“That for use within the house no system has been found in practice to take the place of the water-closet.”
“And that all middens, privies, and cesspools in towns should be
abolished by law, due regard in point of time being had to the condition of each locality.”
By referring to appendix I.,* the cost of the several systems of towncleansing will be seen at a glance, which will be found to vary from 1d. to 11 ½d. per pound on the rateable value of house property, local peculiarities evidently having influence in this matter. For instance, at Rochdale, scavengering is put down at 8 ¾d., Birmingham at 5 ¾d., and Leamington at 1d.; while sewage for Rochdale is put down at 0d., Birmingham at 4 ¼d., and Leamington at 5 ½d.; the totals being 8 ¾d., 10d., and 6 ½d. respectively. The highest rated is Blackburn, viz., at 11 ½d. in the pound.
Coming to my own observations, I shall first notice Berwick-upon-Tweed, as I had an opportunity of watching the construction of the waterworks and drainage of that town 23 years ago, so I inspected their state lately with more than ordinary interest. This is a town of 20,000 inhabitants, situated on rising ground near the mouth of the Tweed, and where its waters are fully affected by the tide. I ascertained that the drainage on the whole had worked well, excepting when the water-supply ran short, which occurs periodically in the summer. The sewers, constructed about 23 years ago, were well executed; but the engineer had under-estimated the water-supply, which had rendered the working somewhat experimental. The first trouble that was experienced was in the high-pressure mains being connected directly with the water-closets; this, when the supply of water was intermittent, sent the excreta back into the closets, creating great nuisances; this difficulty has now been obviated by each closet being provided with a small cistern filled by the mains, from which the closets are supplied. Before this was done, people, finding the water not on in leaving, tied up the valve, so that it might run when it came on, thus much of the supply was wasted by the water running continuously.
The poor classes especially are difficult to manage or to deal with, owing to the practice they are given to of abusing the conveniences, hence this class always demand sharp looking after by the inspector.
Ashpits are allowed in this town to a limited extent, but for small houses boxes or pails are used for the removal of rubbish, ashes, &c.
The sewage falls into the river Tweed, but to this the Tweed Salmon Commissioners object as it is tending to pollute the stream and destroy fish.
When the high-pressure water-supply is good and sufficient, the water-closet and sewage system of the town has worked well, but the entire problem of the removal of house-refuse has not yet been fully solved.
It is quite clear that here, as elsewhere, the subject is one for continuous effort, not possible to be settled by spasmodic exertion, and then to be done with.
[Footnote] * End of Glasgow Report copied.
At the inland town of Dunse, containing about 4,000 inhabitants, and where the water-closet system has been introduced during these last 40 years, I found that, as this was perfected and in operation, new and unanticipated difficulties presented themselves. Thus, as the town became satisfactory in its sanitary condition, the rural districts near and under its level became deteriorated by the nuisances flowing on them. Which circumstance brought about long and expensive law-suits with the proprietors, and especially with the owner of Wedderburn House and Demesne.
In the town of Kelso, situated on the banks of the Tweed, and about 25 miles inland, it was observed here, also, that the increase of sewage, by the introduction of improved water supply and conveniences, was drawing opposition from the owners of the valuable salmon fishing stations. In view of this, the Corporation is now about to try and remedy the evil by carrying their outfall to an extensive shingle bank, where they hope to absorb the objectionable matters.
At Edinburgh it was observed that the sewage that used to flow solely over the fields near Holyrood House uninterruptedly, and at least, without active objections, are now not only increased in their area, but the same system of irrigation is being applied to the west suburbs of the city. Hence, no certain action by the population can be anticipated on this subject.
At Glasgow, from the report of whose Deputation I have so largely quoted, I found that still no general scheme had been decided on; in fact, that different principles had been found applicable to different parts, and broadly, the water-gravitation system to first and second-class houses, and the pail system to those inferior. The sewage yet falls into the Clyde, and Bazalgette's recommendations were considered, if not impracticable, and beyond the means of the ratepayers, at least inadvisable. As a better scheme for conveying the offal away, steam barges, proceeding from Glasgow to the sea, were contemplated; as any attempt to utilize sewage is now abandoned.
As my time and other engagements enabled me to ascertain, such is the state of town and city cleansing at home; and it will be noted that whilst much difference of opinion in detail exists amongst engineers, yet, to those who are able to bring an unprejudiced judgment to bear on the question, the principles to be adapted to the several and varied circumstances are not difficult to be laid hold of. Comprehensively speaking, the interest is a growing one, and in this respect it is not an exception from other great interests and expansions of modern civilization and requirements. If its necessities cause it to unduly infringe on other interests, then conflict
takes place, the conflict not anticipated in the early years of its application, but in the course of years becoming palpable. It is no other than the ordnance versus iron-plate warfare; if the one increases in force and magnitude, so the other must be fortified in ratio. Thus, if ships have to be protected from their assailants, so must the rivers, estates, parks, seats, and castles be protected from the other. Hence Corporations, in initiating sanitary improvements for themselves, are not justified, as hitherto, in neglecting the interests outside of their precincts; and, as justly observed by the Glasgow Deputation, those cities having a natural outlet apart from all other interests, are fortunate.
This latter condition is oftener the case with seabound towns than with inland ones. Certain it is that the idea so often prevailing amongst sanitary engineers that their works are for ever, and all time to come, must be abandoned, and their judgment must be exercised, not as now to create works of magnitude far beyond present wants, but to institute systems to which least objections can be taken ultimately, or for the time being. The wants of the present population must not only be estimated, and of the future, but their capacity to bear the burden of taxation, hence, though working to an end, and on just principles, the consideration should be as to what was actually necessary, and no more, leaving their successors to continue the same. Without being attentive to these facts, the city populations may pay too dearly for the luxury of improvements or quasi improvements, and property may be overburdened by works which could perfectly well be held over.
As an example of the conflict between interests, that takes place consequent on the modern introduction of town cleansing by water-gravitation, we turn to the greatest city in the world, where it has perforce had largest development. The outfall of the sewage, till recent years, was into the Thames, within the precincts of the city. This created nuisances which it was found desirable to remove; hence those measures were taken which have already been described in the preceding part of this paper. But, besides the Metropolitan Board of Works, there exists a Board of Conservators of the River Thames, having other interests than the population of London to take care of, and on which the operations of the former Board were felt to act detrimentally. In consequence of this, Captain Calver, R.N., F.R.S., was, by the secretary, directed to investigate and report on the subject* That gentleman acknowledged the receipt of the instructions, to wit; that he should direct his attention to some recent surveys which had been made by the officers of the Board, of that section of the River Thames extending from Woolwich to Erith, as well as to analytical examinations by
[Footnote] * Thames Commission, 6th June, 1877.
Drs. Letheby and Williamson of the soil of its bed, both in Woolwich Reach and near to the sewage outfalls; and to give his consideration to the changes thus shown to have taken place in the channel of the river, and in the character of its bottom, for the purpose of reporting thereon. Captain Calver adds, that from the time of receiving the foregoing instructions, he had been engaged upon the various details of investigation, including, amongst other things, repeated observations upon the movements of the streams in the central section of the Thames, with the collection of such other physical facts as were likely to aid him in arriving at a clear under-standing of this important and interesting case*
From his report we shall make extracts, noticing the salient points of interest. He states “that the general features of Mid-Thames, its sectional capacity, and the various details of increase and decrease, are all brought out very clearly in the surveys made by the order of the Board. This series—the work of the same observers, and all referable to a common standard—has been made between 1861 and 1876.”
Again: “It having been reported in 1867 that a vessel had unexpectedly touched the ground while passing the southern outfall, a new survey was ordered to be made for the locality.”
Again: “1832 to 1861, a considerable increase in the general capacity of the channel occurred in the foregoing period—the result of dredging, for the most part.”
Again: “1863 and 1864, sewage began to be discharged from the outfalls.”
Again: “Since the Metropolitan outfalls came into operation, the former deep and free frontage of the southernmost one has lost a quarter part of its low water contents.” Again: “that the upper part of the river has been troubled with accumulations, which, as will be shown, must necessarily have been conveyed upwards by the flood-stream.”
In the analyses made, “the mud in each case was black and fetid in a state of active putrefactive decomposition, and, when examined under the microscope, it was found to consist of broken-up sewage matter.” Of the water, when near Woolwich, Greenwich and London Bridge, “all the samples were black and offensive, and they were found, on examination under the microscope, to consist of amorphous matter of the disintegrated tissue of vegetables, especially of wheat, and swarms of diatomaceous remains.” Again: in the last test of 1875, “most of the samples demonstrated the presence of sewage matter in a state of decomposition.” Those from “the Gallion Reach, within the influence of the northern outfall, exhibited organic and other similar matter to those of street-mud, while others in the
[Footnote] * Report, 15th October, 1877.
central track of the river-streams, and acted upon by their scourage, had very little organic matter.”
Again: “The reporters of 1958 estimated that 92,000 tons of solid matter of every description were contained in the sewage passing into the Thames at that time;” but it is now estimated, from data supplied by Glasgow, that “465,000 tons would represent the annual solid matter contained in Metropolitan sewage.”
Again: “The excreta of each person per day having been found by experiment to weigh 2 ½lbs., this, with the population of 3,5000,000, in connection with the outfalls, gives 3,9000 tons per day, or 1,425,000 tons per annum as the amount of excreta sent into the river from the outfalls.”
Again: It was found by experiment “that matter committed to the water of Mid-Thames would move down seaward about five miles in a fortnight.”
Again: “The daily discharge from the outfalls has been stated as 120 million gallons or 19,246,000 cubic feet, so that 423,412,000 cubic feet or 22 days' discharge, represents the aggregate amount of sewage in the oscillating section, being about one-fifth part of the whole contents of the river within the same limits below the level of ordinary low-water. This vast mass of polluted water—eight miles long, 750 yards wide, and 4 ½ feet deep, charged with offensive matter, both fluid and solid, moves up and down the channel four times daily, between Gravesend and near to Blackwall, dropping its solid burden wherever a reduction of the rate of current or still water may favour deposit. The purifying change which the putrescent matter may be supposed to undergo, after discharging from the outfalls, is reserved for future consideration.”
Again: In regard to accretion of the sewage in Woolwich Reach, it is stated that there is “a complete identity between accreted matter and that in the sewage discharged from the outfalls. There can be little doubt that it has been brought from their neighbourhood by the flood-stream. Most observers of rivers are aware of the disturbing action of the first portion of the flood-set, for, owing to its greater specific gravity, it works its way upwards under the last of the ebb-set, and probably obtaining thereby a strong rotatory or grinding motion, the surface of the bottom is sufficiently disturbed to charge the water with its particles.”
Again: “Another point which has bearing upon this section of the case is, the superior carrying-power of the flood-stream over the ebb; a fact very distinctly brought out in the Analytical Returns.”
Again: “The amount of solid matter in the flowing-tide at Greenwich and London Bridge is nearly 21 grains per gallon, while that in the ebb-tide is only 8.2 grains.”
In reference to the deleterious effect of sewage discharged into a tidal river, from various experiments, Captain Calver concludes that “it will be seen that it matters not whether the sewage be sent into the river at low-water at London, or at high-water at Barking Creek and Crossness, for the result is one and the same. The matter from the sewers will work its way upwards, and form accumulations above the outfalls both in the bed and along the sides of the channel.”
Again: As to the theory which erroneously assigns deepening to the credit of sewage discharge. This is said to be due “to two very different causes—viz., to the dredging carried on in the district, and to the scour resulting from the removal of impediments out of the channel in higher portions of the river.” Dredging, also, is stated to have removed “enormous hills of gravel which now disfigure and encumber the banks of the Tyne and Wear.” Another cause stated as tending to increase the depth of Mid-Thames resides in the removal of the old bridge at London, and the dredging that has taken place as high up as Isleworth.
Again: “As matters now stand, the Metropolitan sewage discharge has reproduced in Mid-Thames, in an aggravated form, a nuisance which was felt to be unbearable in the upper portion of the river. Formerly, the sewers at London discharged their contents into the river at low water, and this, Sir Joseph Bazalgette has pointed out, “was most injurious, because it was carried by the rising tide up the river to be brought to London by the following ebb-tide, there to mix with each day's past supply, the progress of many days' accumulations towards the sea being almost imperceptible.” This exactly describes the existing state of things in Mid-Thames, both in respect to accumulation of sewage, its daily oscillation, and its slow progress seaward; the only difference now is, that the nuisance which was formerly brought down to London by the ebb is now carried up to London by the flood.”
Again: “The evidence of the senses may also be relied on as an important factor for determining the question of purity. While in the neighbourhood of the outfalls, I observed that bubbles of gaseous matter, arising from decomposition, were continually ascending to the surface of the water, reminding me of similar experience in the polluted Clyde. The foul condition of the river was also apparent from the smell caused by the disturbance raised by the steamers' paddles; and the floating abominations by which I was surrounded, when making the test observations, are to be remembered rather than described.”
Again: “Contemporary and reliable opinions are all opposed to the practice of discharging crude sewage into rivers.”
Again: “Results worked out, and still being worked out in the Thames, by sewage discharge, are evils of great magnitude, and seriously detract from the general value of the Metropolitan sewage arrangements. If certain foul accumulations, formed near to the old sewers at London, led the reporters of 1868 to declare that the evil had attained such proportions as to render it essential to the well-being of the Metropolis that means should be taken for its permanent abatement, what would they say of similar features on a more gigantic scale lower down the river? Observing that the present channel in Mid-Thames is through banks of fetid matter, that the water in the channel is loaded with material in a state of putrescence, and that it daily oscillates within the Metropolitan area, with its teeming population, and contaminates the atmosphere, they would probably admit this to be a state of things altogether detrimental to the public interest. Though it may be very true that the action of land-floods, and the frequent passing to and fro of the steam-traffic of the river, will always maintain a navigable passage through its foul reaches, yet the sides of the channel and the contiguous foreshores must, of necessity, become more foul, and to a greater distance from the outfalls, as the population increases and the water is more highly charged with the accreting matter which sewage contains.”
Again: “Nothing can be possibly more unsatisfactory than the present condition of things.”
I may add that no effectual remedy is suggested by Captain Calver, though he anticipates that “experimental research and discovery” may bring about “a successful solution of this pressing question.”
The report concludes a re-iteration of what has already been advanced, to the effect that the “foul and offensive accretions have recently formed in the channel of the Thames;” and that a “material portion of these accumulations are in the neighbourhood of the metropolitan sewage outfalls;” and he recommends that the Metropolitan Board of Works be called on to dredge away those portions of the accreted matter which interfere with the convenience of navigation, and that they be requested to adopt such arrangements as are calculated to prevent similar accumulations in future.” He further hopes that the “noble metropolitan river” may be “freed from a drawback which is impairing its commerce and usefulness.”
The report of Captain Calver is met by a lively rejoinder from Sir J. W. Bazalgette, C.B., Engineer to the Metropolitan Board of Works, supported by other scientific men, in which he premises that, “when it is considered that the report in question purports to be, not the exaggerated statements of an advocate, but the calm and deliberate conclusions of a scientific man, upon a matter involving the most serious and vital interests, adopted and
circulated with the authority of a responsible public body, it is impossible to overrate the grave importance which attaches to such statements” as are contained therein.
Again: The Engineer states that, “in order to simplify the subject as far as possible, we propose to direct our enquiry to the following points, viz.:—
“1st. Whether there is any evidence that foul and offensive accretions have formed within the channel of the Thames since the metropolitan sewage outfalls came into operation.
“2nd. Whether careful analyses do show a perfect identity between the constituents of the Thames mud and those of the metropolitan sewage.
“3rd. Whether it is true that the sewage discharged at Barking and Crossness does work its way upwards, and cause the same pollution of the Thames within and about the metropolitan area as formerly existed.
“4th. As to the quantity of solid matter contained in the sewage discharged into the Thames at Barking and Crossness, and whether it is sufficient to produce any sensible deposit in the bed of the river, and as to the real cause of such deposit.”
As to the recent formation of foul and offensive accretions, the Engineer argues that comparison of the state of the river thirty years previous to 1861, and that in fifteen subsequent years, has “no value or significance whatever.” Further, when it is considered that the traverse sectional areas of the river taken at half-tide off the Crossness outfall have been increased by the removal of shoals,', &c., “it would be no matter of surprise if the river in this part of its course should be even more liable to partial deposits forming upon the banks than it was formerly.”
He then enters into the subject of the Woolwich shoals, and concludes “that it is obviously impossible to draw the conclusion which Captain Calver suggests, that because mud is found in this part of the river, therefore it comes from the metropolitan sewers.” Then as to the mud deposits higher up, near Waterloo Bridge, he remarks “that it is obvious that the deposits of mud above referred to, and which, it appears, accumulated in a few months time, could not have resulted from the sewage discharged into the river upon the ebb-tide at a point no less than 14 ½ miles lower down the stream.”
Next, as to the identity of Thames mud with sewage mud, the Engineer endeavours to show the fallacy of much of Captain Calver's arguments. This is illustrated by a table, from which he (the Engineer) surmises that “it is perfectly obvious that no conclusion can be possibly true which is founded upon the supposed ‘perfect identity’ of quantities which vary from 0.85 to 40.91,”
Then, as to the sewage working upwards, the Engineer quotes a previous paper by Captain Calver, where he himself “proves very distinctly the decided preponderance of the power of the ebb over that of the flood,” and points out that the late theory propounded by Captain Calver, to wit, “the operation of accretion has been effected by the superior disturbing and transporting power of the flood stream,” is “diametrically opposite and contradictory.” He also calls attention to Captain Calver's grammar in regard to his introduction into the English language of the new word “stickability.”
The amount of solid matter actually contained in the sewage is then discussed, of which 32 examples were taken from different parts of the Thames, which, being analysed, the Engineer proceeds: “Then taking the average quantity of sewage discharged in the 24 hours, at 120 million gallons, we have, for the weight of solid matter discharged into the river every year, 64,250 tons.” A different result from Captain Calver's, which is 465,000 tons.
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Again: The rejoinder continues, the quantity of solid matter discharged into the river at the outfalls in each tide is 88 tons, or 1,380 million grains; and the quantity of tidal water passing the outfalls in a spring ebb, as stated by Captain Calver is 108,138,140 cubic yards, or 18,248,311,125 gallons; consequently the amount of solid matter thrown into the river from the outfalls only “amounts to .076, or 1/13 of a grain per gallon, a quantity far too small to exercise any appreciable influence upon the purity of the water.”
Again: “That the water in the lower reaches of the river is very much loaded with mud, especially upon flood-tide, is a matter of fact which cannot fail to strike any person observing it; and the reason will be very evident upon examining the state of the river banks.” Then alluding to the “saltings,” that is erosions by waves, having been computed; the cubic contents of the same are estimated, whereby it is found that “at least a million tons of soil are washed into this part of the river every year, in addition to that which is brought down from above.”
It is stated that thus the “saltings below London, therefore, supply at least 15 ½ times as much solid matter as that discharged by the sewage out-falls.” This, the Engineer adds, “is, in fact, the real source of the mud deposit on the banks of the river, which, as we have shown, Captain Calver has erroneously attributed to the metropolitan sewage.”
The report concludes “that there is no documentary evidence to prove that foul and offensive accretions have recently formed within the channel of the Thames;” that, “in fact, the water and mud of the Thames have improved greatly in purity;” that “there is no resemblance between Thames
mud and sewage mud;” that “sewage does not work its way up the river;” and, finally, that “the muddy condition of the river is caused principally by the unprotected state of its banks.”
Here, then, we may pause and exclaim, How doctors differ!
Captain Calver supports his statements by numerous tables and analyses, and Sir J. W. Bazalgette does the same in treble volume, hence his chemical referees quaintly conclude their support of their employer by a remark, viz., conclusions of a few samples only (by Captain Calver's analysts) must be looked upon with great distrust!
The report of Sir J. W. Bazalgette is accompanied by an appendix containing letters and reports of other authorities, besides plans, charts, and sections of the Thames and its estuary. The evidence of Faraday is brought out as to the former foul state of the Thames within the city precincts, and apart from the question before us the charts of the saltings or erosions of the banks of the Thames estuary are interesting to the physical geographer. And here we may take the liberty of pointing out that, as these all take place below the sewage outfalls, extending for a distance of 20 miles, from which Sir J. W. Bazalgette ascribes the muddy condition of the river above—from this, his own principle, we have a difficulty in clearing him from contradiction, when he ignores Captain Calver's statement in the same direction, viz., that the filthiness of the river above the outfalls, extending up to London, little more than 10 miles, is due to the sewage deposits of Barking Creek and Crossness, which is but a corollary to his own theory.
But, in truth, the controversy is of a kind in which one throws his filth into a neighbour's bed, so complete equanimity is not to be expected, on the contrary, perturbations from the true mean of sound judgment are to be looked for. It is open, therefore, to the equirer to suppose, that as the sewage issues from the outlets into the Thames with the ebb, weightier particles will be the first to descend to the bed not far from the outlets; hence, may it not be supposed that, when the advancing flood of the heavier salt water, forcing itself beneath the lighter fresh water, yet ebbing at the surface, arrives at the outlets, these weightier particles will be carried up the river to certain distances? In the notesof experiments, on either side of the question, we do not detect that sufficient investigations have been made on this point. It is, therefore, yet unsettled, and can here only be alluded to.
But to the general public this subject carries little interest with it, for to those acquainted with the Thames near London, 25 years ago and now, the enormous improvement in the cleanliness of its waters is palpable.
This was so patent to ourselves that we had scarcely anticipated a most distant demur from any quarter. Leaving this portion then, and proceeding to what we suggest as being the vital point of misunderstanding between the Thames Conservancy and Metropolitan Board, viz., the interruption of navigation, we will tarry a little to examine it.
The official surveys, admitted to be correct by both parties, show changes going on in the river-bed near Barking Creek and Crossness, but that it has shallowed cannot be stated.
The cross-sections at Crossness show a bank as increasing on the Kent side (that is the side at which the sewage falls); and at Barking Creek, a bank increasing on the Essex side (that is the side on which the sewage there falls). But in both cases a deepening to an equal extent has taken place at the opposite sides of shallowing. The section lines are given for the years 1861, 1867, and 1876. At Crossness the soundings of 1861, on the Kent or outfall side, show a decrease of 10 feet, more or less; but on the Essex side an increase in like quantity. At Barking Creek, similar changes have taken place, but to a less degree. Thus exact data do not indicate danger of closing to the channel of the Thames, but only alteration of its bed. That this alteration is due to the new influence brought to bear on it, viz., the issue of large quantities of drain detritus, we think will be admitted by all unprejudiced persons.
But that the navigation of the Thames will be affected from the issue of the drainage of a district at points higher or lower, or the converse, we are not prepared, beyond a certain point, to admit. If the present drainage were not issued at Barking Creek and Crossness, it would have issued above and below London Bridge, carrying with it the same quantity of matter and sediment into the river, and in an equal degree, and no more; depositing the heavier particles in the beds or along the banks continuously; but at the same time continuously acted on by floods and tides, spreading it out from landward to seaward in that equilibrium due to the natural forces at work.
Thus, in the interests of Thames navigation, the question of outfall at London, or at Crossness, 14 miles below it, is of very little consequence. If one deteriorate passage of shipping, so would the other; but if either can be proved to do so, then the City of London would be bound to seek another area for the deposit of its offal. This contingency appears not yet to have arisen.
In prosecuting my enquiries, on the 2nd August last, I proceeded to Abbey Wood, near to which is the outlet of the South London drainage, on a point of the river called Crossness. I arrived there at about noon, and was taken over the works by the manager. The works are situated on a raised
mound, close to the south bank of the Thames, and on which are also erected official and workmen's houses, with a school for the children. The mound is actually a covered tank of six acres in extent, but being covered with earth, and planted with grass, this cannot be detected by a stranger.
The engine-house, is a spacious erection of the Byzantine style, the chimney-stalk being of elegant proportions. The power of the engines is 500-horse, and is used in pumping the sewage from the main drain into the tank, by means of eight plunge pumps, of about three feet in diameter. The main drain is 30 feet below the surface, and the tank rises above this, having a depth, when full, of 14 feet.
The sewage is only let out at high-water, on its turn” to ebb, and it continues to flow till nearly low-water. There are three outlets for the sewage from the tank into the river, constructed of solid brick and cement, leading to the high-water mark, then by open timber ducts to the low-water mark.
It was near low-water mark when I visited the place, and I could not markedly detect offensive smell, but the water of the river was exceedingly turbid and discoloured.
I also examined the sewage in the tank, through a manhole, and ascertained that but slight offensive odours escaped by this aperture.
I did not consider it necessary to examine the works on the north side of the river, as the principle is merely repeated, but they are larger, the tank there being equal to 10 acres.
The effect of the outfall of city sewage and detritus in a river, then, is similar to what may be readily studied on any goldfield where hydraulic works in simple gold-washings are in force. The sludge does not pen up the rivers of magnitude, but it merely spreads itself out on the banks adjacent to the outfalls, and what it occupies of the original bed, the stream compensates itself by scouring out a deeper channel on the opposite, so that it maintains an equal volume. Limiting the enquiry to navigation, such, in our view, is the influence on the Thames in this much-vexed question.
In regard to its pollution, that is another question. We cannot help opining that Captain Calver is more eloquent on this subject than necessary. That fetid matter is carried up to the metropolitan area, teeming with population, contaminating its area, is surely their grievance, not his; and so long as they are contented with the smells in their precincts, the Thames Conservancy need not disturb themselves, but if they can show that ship and barge crews are struck with gastric fever, or otherwise intolerably discomposed by the odours, by passing the outfalls, this comes within their functions to remedy. But no statistics are brought forward on this head, nor are complaints from this quarter even alluded to.
Looking at the question with a brid's-eye view, in our humble opinion
there can be no question that London, having adopted the water-gravitation system for cleansing its precincts, within practical distance, no sites could have been better chosen for the outfalls than Barking Creek and Crossness, as here the country around is devoid of population, hence the works, if not altogether inoffensive, are placed where they are in a position to give least offence.
Having thus discussed the Home sewage question in its various phases, and noticed the opinions drawn from experimental enquiry, as well as from long experience, we will now turn to the subject as it presents itself in this Colony. Referring to the report published by the Sanitary Commission of Dunedin, dated 25th January, 1865, we find this town principally built of wood, at that time containing 15,037 inhabitants, and whose bad sanitary state was graphically described by the city engineer, the late John Millar, Esq., F.S.A.
The remedies submitted to the Commission by several engineers were as follows:—One assumed, as a matter of course, that the sewage would be “hurried into the harbour,” though ultimately the outfall might be on to the ocean beach. Another propounded a scheme of irrigation, conducting the sewage over or through two dividing ranges to the land between Dunedin and Saddle Hill, and in which the Taieri Plain might participate. This was to be effected by a series of pumping engines. Another suggested that the sewage should be discharged at the Lawyers' Head, by means of hydraulic pressure on the drains. Another scheme was to submit the Forbury Flat to a system of high-class farming by the application of liquid sewage.
From this it may be surmised that there was great diversity of opinion amongst engineers as to the proposed measures; but in saying this, it cannot be said to be more so than is or was existent amongst engineers in England at that date. The fact of the matter is, the subject is a growing one, in which time makes changes, and matured experience, we have seen, has suggested alterations.
In this case of Dunedin, we see one engineer proposing to direct a system of irrigation over a plain, which ten short years have converted into a town. Another proposes to fertilize, by a similar scheme, an agricultural district, separated from the town by two ranges of hills, at ten miles distance, a project worthy of the greatest cities in Europe, and only practicable to them. Another proposes to send it into the sea; another into the harbour. It is worthy of note that none proposed a dry system of treatment.
Now it would be wrong to infer, from the want of unanimity in the engineers, that they were incompetent professionally. On the contrary,
the question was not of a technical nature in the first place, and at that time, but of the power to bear taxation on the part of the citizens, in their anticipated progress and increase, in estimating which (a duty of the statistician rather than of the engineer) they may be said to have failed. Study of the various works applied to cities in Europe will illustrate this fact in every direction; but here, also, the lesson cannot escape us. The practical end of all the professional advice given to the Dunedin Commission has been, that the sewage is carried to the nearest available point; that is into the harbour fronting the city, and into which area it will flow till sufficient opposition has been conjured up to prevent it.
This is the history of older cities; so it is the same of younger.
And continuing our theme, with Dunedin as our example: This city, like London, having adopted the water-gravitation principle of cleansing, the sewage will flow to its assigned levels, till, as in its great prototype, it becomes an intolerable nuisance. Then the city authorities will have to look abroad for projects in its disposal otherwise; and to all of them, from local interests, there will be objections. The question in the end resolves itself, not into attaining a project which has no objections attached to it, but to one which has the least. Hence, as we see in the cities of the Home country, the wearied and puzzled municipalities will have to look to the harbour as an easy solution of their difficulties, but to be opposed by the Boards in charge of this interest. Next, they will look to the ocean beach, to be thwarted by the suburban population and pleasure-seekers of that locality. Perchance, then, imitating the Borough of Brighton, they may have power to tunnel to beyond Tomahawk on the one side, or Green Island on the other; or, taking example by the inland cities of England, such as Birmingham, Leeds, or Bradford, they will discourage the water-gravitation system, and, perforce, purify their sewage before delivering it into the subjacent water of their estuary.
In Christchurch we also have a recent example in the colony of want of unanimity as to measures, the projected scheme only to be thwarted by the ratepayers; the real difficulty being, not what should be done, but what the majority of the several interests will allow to be done.
From this, it might be inferred, that sanitary engineering is at best experimental. To this it may be answered, that it has hitherto been largely so, a necessary concomitant of the modern advance of science, the altered conditions of society, and the variety and complicated arrangements of its requirements. In this, it has been no otherwise with other practical and economical branches, such as railroads, steam navigation, manufacturing enterprises, etc. But large data, the result of experiment and observation, are also now known or accessible to the engineer; hence principles for
guidance under the different difficulties he has to meet, are at hand to support him.
Thus in this colony, when principles are sought for, they will be found to be simple in the main, however complicated the details may be.
Sanitary works resolve themselves into two distinct systems, namely—wet and dry; the former acting by the gravitation of water, the other by manual or machine carriage.
The wet system carries its burden to the sea, or to rivers, when it can do this unopposed; to areas for irrigation in the production of crops; or to waste areas for the purpose of absorption and filtration. The burden may also be brought to tanks for precipitation and the purification of the sewage.
The dry system has its burden carried to the sea, whether by boat or carriage; to the fields for direct application to cultivation, or to works of manure manufacture, for all of which the extracts made in the preceding part of this paper give examples.
The separate systems, suitable for the respective situations, are not difficult to decide on. Where towns have accessible water-supply and easy exits, the wet system is suitable; where these do not exist, the dry system becomes imperative. We use the word imperative, because it is in human nature for people to divest themselves of that which is disagreeable with the least trouble to themselves, and this, when the conditions are favourable, is most readily effected by water. But it has not in all cases proved economical or efficient in the end where water has been had recourse to, owing to the nuisance being cast on other interests, and for which the law when appealed to has demanded a remedy at great cost.
In favour of the dry system one great recommendation is to be said, namely—that it returns to the soil that which man took from it; thus, that it should have a general acceptance by cities in a practical and convenient manner, will always be considered a desideratum.
In New Zealand, more than in almost any other country, the wet system is easily available, districts in which a contrary condition exists being limited to Canterbury, Southland, and Auckland.
The proportion of human excreta to sewage is an important question to sanitary engineers; and taking the data afforded by London, it will be found that these do not exceed one-hundredth part of the whole sewage. This element makes but a small factor in the whole, and is of very secondary consideration, under the circumstances of the city possessing a full water-supply and a ready place of disposal, such as the sea or a tidal river. But in the case of inland towns, where they are forced to purify the sewage, the matter is different; for though the excreta there may only form a small portion of the whole volume to be dealt with, they perforce form a large
part of the nuisances to be got rid of. The proportion of excreta must necessarily vary with the industries and habits of the towns or cities, in manufacturing populations the refuse from factories being great, while with residential populations this must be limited. Hence, in inland towns, we observe the present measures of municipalities discouraging water-closets and promoting some form or other of the dry system.
In a colony such as ours, where new municipalities are being annually incorporated, it is desirable that in their varied responsibilities they should not neglect sanitary reform. Though in the early stages of a town cesspools are not to be avoided, yet in relation to the health of the people these should, as early as possible, be abolished by law, and in the first place the dry system instituted, until they have obtained a water-supply and fully considered their facilities of removal and the permanent sites to which they could conduct the sewage, with the least offence to interests in their neighbourhood.
Appendix, No. 1.
Comparison of the Cost of Disposing of Town Sewage by different Processes, in proportion to the Annual Rateable Value, etc., 1875. Compiled from a Table given in the Report of Committee appointed by the Local Government Board, 1875, page lviii.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Name of Town.||Population (about)||Number of Houses.||Number of Water-Closets.||Annual Rateable Value.||Per £ of Rateable Value.|
|3. Blackburn||90,000||16,700||780||235,127||Sd.||3 ½d.|
|5. Chorley||20,000||4,000||200||54,407||4 ½d.||2 ½d.|
|6. Doncaster||20,000||4,300||68,721||3 ½d.|
|7. Harrowgate||12,000||1,500||1,620||50,000||5 ¾d.|
|8. Leamington||24,700||4,500||8,370||113,400||5 ½d.||1d.|
|9. Merthyr-Tydvil||55,000||10,778||8,000||135,000||7 ½d.|
|10. Rugby||8,400||1,700||1,400||45,000||1 ½d.|
|11. Tunbridge Wells||23,000||5,750||3,635||142,914||10d.|
|12. Warwick||11,000||2,400||2,000||43,339||6 ½d.|
|13. Wolverhampton||71,000||14,000||750||210,000||2d.||1 ½d.|
|14. West Derby||31,000||3,220||163,000||4d.||1 ¼d.|
|By Land Filtration.|
|16. Birmingham||350,000||83,420||8,000||1,229,844||4 ¼d.||5 ¾d.|
|17. Bolton-le-Moors||93,100||18,249||758||311,563||2d.||1 ½d.|
|18. Leeds||285,000||57,000||8,000||945.141||4 ¾d.||4 ½d.|
|19. Bradford||173,723||34,000||4,050||745,671||3 ¼d.||2 ¾d.|
|By the Pail System.|
|21. Rochdale||67,000||14,388||835||222,000||8 ¾d.|