View report page

7
Miildleton—The Borough Surveyor states—"If of sufficient area and properly managed,
" they (bacteria-beds) will act satisfactorily."
Nelson—The results obtained by experimental bacteria-beds were quite satisfactory.
Oldham— Extract from a report entitled, "The Treatment of Oldham Sewage in the year
1900," by the Medical Officer of Health, p. iii—"With the exception of a few days during the
''year, when the weather was very dry, the method (bacterial treatment) has been entirely
" successful."
Ormskirlc—The Surveyor states that—" The results obtained at the council's farm, after
" the sewage running through lagoons into settling tanks and then run on to the land aud after"
wards through the coke breeze filter beds, are very satisfactory and meet the requirements of
" the authorities."
Oswestry—The Town Clerk states that they " have no doubt as to the success of the
" bacterial treatment. Our results are continuously satisfactory, and the effluents keep free from
" putrescence."
lleigatc—" The result of three years' searching trial is so satisfactory as to encourage the
" Council to sanction the outlay and adopt a scheme for treating the whole of the sewage of the
" Borough on the lines adopted by the experimental plant."
Salford—The Borough Engineer states that " we can fully depend upon the bacteria-beds
" to give a satisfactory effluent, even when working night and day, almost without intermission."
Permanent beds to treat the whole of the sewage are being constructed.
Sheffield—" The degree of purification obtained has been uniformly satisfactory. The loss
" of capacity of the beds continues, and experiments are being conducted with the object of
" reducing this as much as possible. Permanent works on bacterial principles are contemplated,
" but working details cannot be decided upon until further experiments are completed."
Southport—The Medical Officer of Health says that the " bacteria-beds are only small
" experimental ones. . . . They have, however, worked entirely to our satisfaction so far as we
" have tested them, and they have always produced a clear and non-putrescible effluent."
Walsall—The Borough Surveyor states that in the Bloxwich district first-class results
are being obtained in the bacterial treatment of the sewage.
Wolverhampton—The Town Clerk states that the results of the coke-bed treatment
are good, but that a permanent installation is doubtful owing to the presence in the sewage
of iron salts in large quantities.
York—In a Report to the Sewerage Committee, dated October, 1901, the City Engineer
states (on p. 41), with respect to an experimental plant consisting of an open septic tank and
continuous treatment in coke-beds, that the results were excellent and the filtrate was nonputrescible.
That " the system is adaptable for larger quantities per square yard than any other
" experiment," and that there is no loss of liquid capacity in the coke-bed.
Short Summary of the Evidence given before the Royal Commission on Sewage Disposal.
It has been suggested that the results arrived at by the Royal Commission on sewage
disposal would be of great value to the Main Drainage Committee of the Council. The Commission
have now published their minutes of evidence, and a careful perusal of the evidence
given by the independent experts, including engineers, bacteriologists and chemists, shows that
they are in general agreement in maintaining that the only known method of producing a
satisfactory sewage effluent on a large scale is by the adoption of one or other of the various
systems of bacterial treatment.
The bacteriologists gave evidence to the effect that the purification of sewage was a
combined anaerobic and aerobic process, and that the best results were obtained by a more or
less perfect anaerobic treatment, followed by an aerobic treatment. The evidence in support
of this view tendered by Professor Marshall Ward and by Dr. Sims Woodhead, is mainly
based on theoretical grounds, and will be found to be of great value and interest.
On the other hand, Dr. Adeney, Colonel Ducat and others claim that their processes are
entirely aerobic in their character. In face of the above evidence this contention appears very
doubtful, and it is more likely that the one treatment succeeds in combining the two processes.
The great majority of the witnesses agree that crude sewage cannot be successfully
treated by contact beds alone, since, although the results are good and a non-putrescible effluent
is produced, the liquid capacity of the beds diminishes so rapidly that they soon become useless.
In order to prevent this choking of the beds and to maintain their liquid capacity, almost
all of the schemes described iuclude a preliminary process of sedimentation which is in most
cases also rendered an anaerobic or so called "septic" process. Its main objects are to free
the sewage from mineral suspended solids and to cause the complex suspended organic solids
to pass into solution and to become simplified in nature. In the subsequent aerobic process,
usually carried out in coke-beds, opinion is divided as to the respective merits of a continuous
and of an intermittent supply. It must be said that those who support the continuous treatment
make out a good case so far as the results obtained are concerned. The continuous system seems
to produce nitrates in larger amount than does the intermittent system, but at the same time the
effluent is by no means as free from suspended solids which appear to be washed through the bed.
Some special method of distribution of the liquid to the bed is required by the continuous treatment,
and this is not only a cause of additional expenditure but also of additional trouble in
maintenance as compared with the intermittent system of supply.
It is generally agreed that the liquid capacity of a new bed falls rapidly when it is first
started, but it is maintained that this decrease soon ceases, and that a permanent capacity can be