The Sewage Farms of Berlin.
At the ordinary meeting of the Institution of Civil Engineers, held on Tuesday, April 5, the president, Mr. George Berkley, being in the chair, a paper was read on “ The Sewage Farms of Berlin,” by Mr. Herman Alfred Roechling, Assoc. M. Inst. C. E.
Berlin is situated in the sandy plains of North Germany on both sides of the River Spree, which empties itself into the Havel, at the town of Spandau, about five and one-half miles below the city. The Havel is a tributary of the Elbe, and forms a succession of lakes immediately above and below the junction with the Spree, which are picturesque in places, and are a favorite holiday resort of the population. The flow of water in the Havel and in the Spree is very sluggish, and the latter rivei in periods of great drought discharges only about 460 cubic feet per second. The area of the city is about twentyfour and one-half square miles, and its population at the last census (December 1, 1890) was 1,578,794. The density varies from 220 to 25 persons per acre, each dwelling house (flat system) being inhabited by an average of 65 people. There are about 250 miles of streets, 80 miles of brick sewers, 285 miles of stoneware pipe sewers, and 55*^ miles of pumping mains to the sewage larms The water-works were purchased (from an English company) by the city authorities in 1874, and the authorities also established their own gas works, as they could not come to terms with the Imperial Continental Gas Association. The city provides for its extraordinary expenditure by the issue of loans, the last loan, that of 1886, £2,500,000 was issued above par (101,18); this is an excellent indication of the credit it enjoys in the money market.
After the Franco-German war, Berlin became the German metropolis. Since then it has grown rapidly, and the changes it has undergone have been very marked. Whole districts have been cleared of the old insanitary houses, new streets have been formed, and others have been widened. Many new and elegant buildings have sprung up, the old abominably smelling street gutters, which were practically open sewage carriers, have disappeared, and under the sway of an intelligent and enterprising city council, which is the sole municipal authority, Berlin has become one of the finest and best managed cities in the world.
It was originally intended to drain the city in the ordinary way by two main intercepting sewers one on each side of the river, with one common pumping station, and to discharge the sewage, after some slight treatment, into the Spree. A scheme was prepared on these lines in 1861, hut it was not accepted, and finally, after numerous experiments respecting the best mode of sewage disposal had been made, the city council decided to employ sewage irrigation, and Mr. Ilobrecht’s new plan for the main drainage of the town was adopted in March, 1873. The works were commenced in August of the same year, and they have been in hand ever since. Under Mr. Ilobrecht’s scheme the whole area of the town is divided into twelve separate drainage areas, called “ radial systems,” which are entirely independent one of the other. They have each a pumping station from which the sewage is raised direct on to the farms, two drainage districts being in some cases united to one rising main. The area of these radial systems varies from about 674 acres to 2117 acres, the total population in such of them as are entirely built over being about 200,000.
The authorities have purchased the whole of the land required for sewage fanning ; some of this land lies in the north and northeast, about six miles from the city, and some in the south about twelve miles distant from it. The total area of all the farms has now reached 18,790 acres, of which at present only 11,016 acres are under sewage treatment ; the remainder is, however, being prepared for sewage farming, and the acreage of the farms is extended as circumstances require. The subsoil on the farms is, generally speaking, sand, with a preponderance of sandy loam in places, especially on the northern farms, and is well suited for sewage irrigation. The land is practically level, with small eminences here and there. The sewage of about 112 persons is now treated on each acre of land.
The distribution of the sewage takes place by means of underground cast-iron pipes, which start from the standpipes on the rising mains and terminate on the small summits, where the open earth carriers commence. The whole of the land that receives sewage has been specially prepared for irrigation by levelling and draining. The effluent from the farms is conveyed in open ditches into small streams, which empty into the river Spree, partly above, partly in the city, and partly below it.
The authorities employ a large number of “ misdemeanants ” in the work on the farms ; these are men who have been sentenced for various minor offenses to undergo a period of confinement in the house of correction ; they are the loafers of the Berlin streets. From a philanthropic point of view, this course cannot be too highly commended, as it gives the men a chance to get back into regular habits and thus to redeem their characters.
The city has spent about .£2,906,792 in works of sewerage, and .£1,173,648 in the sewage farms, and about 350.000,000 tons of sewage have been utilized on the farms since the commencement of irrigation. Broadly speaking, the largest acreage in 1S89-QO was under cereals, viz., 2817 acres, then follow the grass plots with 17S5 acres, the roots and green vegetables take the third place with 1013 acres, and oil producing plants are cultivated only on 237 acres. There has been a very fair profit on the management of the farms since 1S86, but of course the amount has not been sufficient to meet the payments for capital expenditure. The deficiency, however, is not a large one, as it has necessitated only an average annual rate of o.Sqtl. in the pound during the last five years, or a payment of 7.1 id. per head of the population per annum. This is a remarkably small amount, and compares favorably with what has been paid in England for sewage utilization.
The degree of purification attained has been excellent, as on an average from 95 to 98 per cent of the organic ammonia contained in the sewage has been abstracted on the farms. This is considerably above the figures quoted by the Rivers Pollution Commissioners as the result of sewage farming in this country. The farms have had no ill effect upon the hea th of the population living on them. an;l the prejudice against them has almost died out, which is evidenced by the ever increasing demand for sewage by adjacent farmers and landowners.
On the whole, Berlin is to lie congratulated upon the cheap and efficient way in which it utilizes its sewage. Where other towns have failed it has succeeded, and that upon a scale at present without a parallel.