A Short Retrospect.
In dealing with the sewage question during the last century, it will be an advantage to distinguish between the theory and practice of sewage purification, as such a division of the subject will render it less complicated and will tend to avoid misconceptions.
Dealing first with the theoretical side of the question, it is very doubtful whether at the dawn of the century even a working hypothesis existed to explain the process of sewage irrigation which was then adopted in one or two instances, notably at Edinburgh, where the town sewage was very successfully purified on the Craigentinny meadows. It is more than likely, that at this time instinct took the place of theory, and that sewage irrigation was an instinctive imitation of irrigation with river water employed for many centuries in some eastern countries.
Later on it is on record, that Cagniard de la Tour in France, about the year 1825, and Schwann in Germany, about the year 1836, expressed the view, that organised substances—micro-organisms—played some role in fermentative and putrefactive changes. Almost diametrically opposed to this were the views authoritatively laid down by the then star in the chemical horizon, Justus von Liebig, who, about the year 1845, maintained that these changes were brought about by the dead inert matter itself—by molecular movements in the same—and not by organised substances, the presence of which in fermenting or putrefying substances was purely accidental. So great was Liebig’s authority then, that many almost blindly adopted his views, and the strife that commenced around these opposing views was fought with the greatest bitterness. But the stronghold of old ideas, which were gradually but surely being supplanted by new ones, could not hold out for ever against combined attacks, however stoutly it was defended by its designer, and its final downfall came about the year 1860, when a young Frenchman, Pasteur, established beyond doubt by his ever classical researches, that fermentation and putrefaction were, in the first instance, due to living organisms and not to dead matter. Pasteur further demonstrated that living organisms were also the cause of some and probably of all zymotic diseases.
So far, so good! But unfortunately the methods of biological research employed by M. Pasteur were very cumbersome and left otherwise much to be desired, so that his discoveries could not be fully utilised and extended, until in 1882 Robert Koch of Berlin published his new methods of investigation. This was the signal of raising the floodgates of biological (bacteriological) research throughout the world with this result, that the flood waters pent up until then inundated practically other branches of scientific investigation and drowned their individual life for some time to come.
During this interval, 1860 to 1882, investigators who wished to study the organised impurities in sewage had to proceed by indirect methods. They had no means of ascertaining by direct biological experiment the number and character of the micro-organisms contained in sewage: all they could do, was to determine chemically the dangerous nature of the sewage by the amount and origin of organic matter it contained, which would probably act as food to the germs; and the greater this amount was, so it was inferred, the greater would be the number of germs it harboured and the more dangerous its character.
This was the condition of things at the time the second Rivers Pollution Commission carried out its investigations, which in many respects, and rightly too, are still considered standard investigations. It cannot be surprising, therefore, that, being without proper means of biological examination, and having to rely chiefly on chemical methods only, the Commissioners came to the conclusion that the changes brought about in sewage purification were due to mechanical and chemical agencies!
It is frequently a matter of the utmost difficulty to ascribe, after the lapse of half-a-century, a new theory to one special author, as several investigators may have been trending the same way quite independently of each other, but may not have been equally successful in the matter of their publications becoming generally known. Theories, as a rule, do not drop out of the clouds like meteorites, they force themselves gradually upon men’s minds and are elaborated by them until ripe.
Bearing this in mind, and subject to further research, it would appear as if Alexander Müller had been the first to apply Pasteur’s general theories as to decomposition, fermentation and putrefaction to the problem of the self-purification of sewage. He made his experiments in 1869 and published them in 1873. Since that date a very large number of investigators have been at work on similar lines, and whilst it would lead too far to deal with them minutely, it ought to be stated that the results of their labour confirmed the view of living organisms playing a very important part in the decomposition of sewage. Among the many names prominent in this respect are those of Schloesing, Müntz, Hatton, Warrington, Sorby, Winogradsky, Percy Frankland, Dupré, Emich and Dibdin. That set of researches, however, which has done more than any other to consolidate the theory of bio-chemical changes taking place in the self-purification of sewage are the investigations of the Massachusetts State Board of Health, which were commenced in November 1887, and are still being continued.
Since 1895 a large number of additional experiments have been made, which will be dealt with more in detail later on, but speaking generally they have not materially increased our knowledge of the processes taking place in sewage purification.
Summarising the remarks on the theoretical aspect of this question, it may be said that, as to the agencies at work, we know now they are of a mechanical, chemical and biological nature; but as to the processes and products brought about by these agencies we know very little beyond the initial and terminal stages, as will be pointed out in some of the subsequent observations.
Directing now attention to the practical side of the question, it has already been stated that the only known sewage treatment at the commencement of last century was land irrigation. Then about the middle of the century chemistry seems to have taken the matter in hand and tried to make a lucrative business out of it. It is on record, however, that it did not succeed in this attempt, and the financial loss which this endeavour has caused is a dismal subject to investigate.
There is before my mind’s eye the case of a gallant officer of His Majesty’s land forces who, after having reached very near the summit of his career, retired and employed his time in trying to make a fortune out of sewage. So enamoured was he of the subject, that—so the story goes—he commuted his pension to have all the more ready money; but fortune did not smile on him, and his last days were spent under the lengthening shadows of the sorrow of financial difficulties, having practically lost all he possessed.
The emphatic verdict of the first Sewage Commission of 1857, the first and second Rivers Pollution Commission, and, indeed, of all other authoritative investigations, was in favour of land treatment; and it cannot, therefore, be surprising to find that the Local Government Board insisted, save in exceptional cases, that “any scheme of sewage disposal, for which money is to be borrowed with their sanction, should provide for the application of the sewage or effluent to an adequate area of suitable land before it is discharged into a stream.” Indeed, had this body taken any different view and neglected the findings of practically all authoritative inquiries, it would have been singularly deficient in the discharge of its duties to the ratepayers of this country.
But the best of land cannot go on for ever doing its duty if by systematic neglect and ignorance the essential conditions for successful purification are year after year violated; and the great pity is that the Local Government Board, after deciding in favour of land treatment, did not systematically superintend this operation. It may not have had the power, but it is quite evident that had it done so, things would not have drifted from bad to worse, until local authorities, driven to despair by the apparent failure of land and not discerning the right cause, refused altogether to be ruled by what seemed to them a very unfair and absurd restriction.
It was at this time that Mr. Dibdin, who, on behalf of the London County Council, had been carrying out a set of valuable experiments, came forward with his application of well known theories to sewage operations on a large scale. As I pointed out at the time, Mr. Dibdin’s experiments proved beyond a doubt that the application of sewage to suitable land was right in principle and that the failures were brought about by the non-observance of the rules laid down by this gentleman—that, in fact, sewage irrigation was the only natural method of sewage purification and that all the other methods were artificial. I described land treatment as the natural self-purification of sewage and the oxidation or contact bed system as the artificial self-purification of sewage.
But the swift current of public opinion had set very strongly against sewage farms, and nothing but the contact bed treatment would do. A large number of experimental plants on this system grew up like mushrooms all over the country, and the waves of enthusiasm seemed at one time to engulf even the Local Government Board itself with its “antiquated notions,” until Parliament came to the rescue and appointed on May 7, 1898, a new Royal Commission to study the question of sewage purification.
This Commission consists of nine members,[4] i.e. six professional men and three laymen. Of the professional men, one is a biologist, one a chemist, two are medical men in administrative positions, and two are engineers likewise in administrative positions. Of the laymen two are members of special boards for the prevention of the pollution of rivers.
So far the Commissioners have issued an Interim Report dated July 12, 1901, a volume of evidence and a volume of appendices. Quite lately, it is stated, they have issued a further Interim Report, to which are attached separate reports on some special subjects by their officers, but this report has not yet come to hand.[5]
At the time of their first Interim Report, July 12, 1901, the Commissioners had held altogether thirty-five sittings, the first of which was on June 22, 1898, and the last on May 22, 1901. The period thus covered is nearly two years, and out of the thirty-five sittings thirty took place in London, and five in the provinces, viz. at Leeds, Ripon, Manchester, Accrington and Reigate.
On these occasions, all in all, fifty-eight witnesses were examined, who may be grouped as follows:
| 1 | Zoologist |
| 1 | Botanist |
| 2 | Laymen |
| 3 | Bacteriologists |
| 5 | Lawyers |
| 7 | Medical men |
| 11 | Patentees |
| 14 | Chemists |
| 14 | Engineers |
58 witnesses in all. | |
Out of this number twenty-five were officials, viz. five lawyers, six medical men, six chemists and eight engineers. Four officials were further managers of artificial sewage purification works, but not one single manager of natural purification works, i.e. a sewage farm manager, was called, the term “sewage farm manager” being used here to indicate an official whose sole duty it is to manage a sewage farm.
The entire absence of this latter class of official is so striking that it cannot be due to accident, but must be the outcome of a settled policy not to reopen questions conclusively settled by previous inquiries.
Another point that strikes the observer is that the Commission only called one zoologist and one botanist, as it is to these scientists that belongs in the first instance the question of studying the fauna and flora of sewage before the subject is taken up by other branches of natural science.
Speaking on the whole, the evidence taken by the Commissioners forms very interesting reading, and ought to be carefully studied by those who have to deal with the subject. When now and again opinions are expressed, which seem directly opposed to each other, it must be borne in mind that here, as in other things human, unanimity of opinion, though much desired, is apparently unobtainable.
To understand the conclusions fully, at which the Commissioners in their Interim Report have arrived, it ought to be pointed out that they had either to accept the recommendations in favour of land passed by all previous Royal Commissions and authoritative inquiries, or they had to show by incontestable evidence that their predecessors had made grievous mistakes, and where!
Of these two courses, the present Commissioners have adopted, no doubt for very good reasons of their own, the first, and they have started therefore, in the conclusions to which they have come, at the point where previous inquiries had left off, viz. that land treatment is a very proper method of sewage purification.
But before referring more in particular to their observations on land treatment, it will be necessary to point out that the Commissioners evidently divide all methods of sewage purification into two main classes, viz. natural and artificial methods. Into the former they only place land treatment, whilst they call all other methods artificial.
This division seems to have given a great deal of offence to all those who have expressed decided and frequently very one-sided views in favour of the “bacterial” treatment of sewage; but on closer examination it cannot be denied that the Commissioners were quite right in forming this view, as the following remarks will show.
For main divisions of all methods of sewage treatment two factors seem to be of primary importance, viz. the agencies which bring about this purification, and the way in which these agencies are employed. Now, it will not be denied that all agencies are natural ones, whether the process employed is a purely chemical one, a purely “bacterial” one, land treatment pure and simple, or a combination of these, and, at the present time no such thing as an artificial agency is known; indeed, it is perhaps not too much to say that there cannot be such a thing as an artificial agency. Hence it is impossible to divide sewage purification methods in this respect by the agencies employed, and one is bound to fall back upon the way in which these agencies are employed. Here it is no longer open to argument whether a chemical process or the contact bed system—oxidation bed system—is artificial, or whether the land treatment is natural! For who would deny that masonry or concrete tanks and the materials contained in the same are artificial products—i.e. products formed by man—and that land is a natural product—i.e. formed by nature—and that further the soil is the natural home of bacteria. Hence it must be perfectly clear, even to a casual observer, that the line of demarcation drawn by the Commissioners between all known systems of sewage purification is a correct and legitimate one, and that all objections to such a division are based on misconceptions.
Concerning land treatment, the Commissioners observe, “We doubt if any land is entirely useless,” but further on they observe that peat and stiff clay lands are generally unsuitable for the purification of sewage. Concerning peat, nobody acquainted with the subject would probably differ from their conclusions owing to the great amount of moisture contained in this material; but as to clay soils, the Commissioners when making this statement must have known that there are several successful sewage farms on this kind of land in existence, such as the sewage farms at South Norwood, Wimbledon, Warwick and Leicester, not to mention others. In the case of Leicester, although the land is a very dense boulder clay, the Corporation of this town have just purchased the freehold of the farm for about 160,000l.
Dealing with the artificial processes from a chemical point of view, the Commissioners are of opinion that it is practicable to produce by these processes alone, either from sewage or from certain mixtures of sewage and trade refuse, effluents which might be discharged without fear of creating a nuisance, and that in consequence the Local Government Board would be justified in modifying, under proper safeguards, the present rule as regards the application of sewage to land.
The artificial processes referred to in the observations appear to be the following:—
Closed septic tanks and contact beds.
Open septic tanks and contact beds.
Chemical treatment, subsidence[6]
tanks and contact beds.
Subsidence tanks and contact beds.
Contact beds alone.
Closed septic tank followed by continuous filtration.
Open septic tank followed by continuous filtration.
Chemical treatment, subsidence tanks, and continuous filtration.
Subsidence tanks followed by continuous filtration.
Continuous filtration alone.
The Commissioners do not say what these safeguards are, in fact they state that no general rules concerning them can be laid down, and that in the case of these artificial processes it is necessary to consider every case on its own merits.
The next point dealt with is the bacteriological quality of effluents, and here the Commissioners observe: “We find that, while in the case of effluents from land of a kind suitable for the purification of sewage there are fewer micro-organisms than in the effluents from most artificial processes, yet both classes of effluents usually contain large numbers of organisms, many of which appear to be of intestinal derivation, and some of which are of a kind liable under certain circumstances at least to give rise to disease.”
No particulars of effluents from sewage farms are given, and later on it will be shown that this conclusion of the Commissioners is not in accord with the results published up to now and available concerning the bacterial purity of effluents from land treatment.
The report concludes with some remarks on rivers pollution. The Commissioners state that it is of the utmost importance to provide the simplest possible means for adequately protecting all rivers, and they think that this subject is of such grave importance “as to demand the creation of a separate Commission or a new department of the Local Government Board, which shall be a supreme Rivers Authority, dealing with matters relating to rivers and their purification, and which, when appeal is made to them, shall have power to take action in cases where the local authorities have failed to do so.”
Summing up the observations on the practice of sewage treatment, it may be said that as a result of their extended inquiries, the present Royal Commissioners have at the end of the century re-established land in its position as the first and only natural method of sewage purification, beside which they have recognised artificial (biological) treatments as being under proper safeguards admissible for the purification of sewage.
Before concluding this portion of the observations, it is necessary to mention the valuable work done by Mr. Scott-Moncrieff and Mr. Cameron, who, contemporaneous with Mr. Dibdin, but quite independently, had experimented with sewage and evolved their own artificial methods of sewage treatment.
These remarks must suffice for the more historic portion of the subject, viz. the progress of sewage purification during the last century, and it is time now to direct attention first to natural and afterwards to artificial sewage treatments.
[4] Two of these have since retired.
[5] This report has just been issued (August 18, 1902), and although the special reports it contains are of the greatest interest, it is not necessary to refer to it again in these observations.
[6] The expression “subsidence tanks” is intended to denote tanks which are used in such way that little or no septic action is produced.