Volume 6

Report of the Commissioners appointed in 1898 to inquire and report what methods of treating and disposing of sewage (including any liquid from any factory or manufacturing process) may properly be adopted.

  • Great Britain. Royal Commission on Sewage Disposal.
Date:
1902-1915
Catalogue details

Licence: Public Domain Mark

Credit: Report of the Commissioners appointed in 1898 to inquire and report what methods of treating and disposing of sewage (including any liquid from any factory or manufacturing process) may properly be adopted. Source: Wellcome Collection.

    873/1008 (page 7)
    ~] Mr. SIDNEY BARWISE, M.D., D.P.H., Medical Officer of Health to the Derbyshire County Council. County Offices, St. Mary’s Gate, Derby. June 29th, 1903. Sir, I regret that owing to illness I have not had an opportunity before this of replying to your letter of May. I have now had time to consider the various questions you sent me and beg to reply as follows :— (A).— Effluents which will pass into a non-drinking water stream. 1. I am in favour of standards of purity being fixed by some Central Authority as a generul guide to the various Sanitary Authorities dealing with the question ot sewage purification. I doubt whether it would be wise to fix absolutely and irrevocably a standard in an Act of Parliament, because the circumstances through the country are so different, and a standard which might legitimately be adopted in the lower reaches of a watershed might not come up to what might be necessary in the upper reaches, particularly where tributary streams are derived from densely-populated districts. Another reason why the standard should be only one adopted as a general guide ‘is that in the future new methods of analysis may be devised and better processes of purification be brought out, and the standard from time to time should be capable of being revised. It should also be made clear that, in mentioning any standard, it is a minimum standard. 2. In fixing a standard of purity, I think that it is not public policy at present to fix the standard too high. I think, however, that for Derbyshire it should be higher than that suggested by the Mersey and Irwell Joint Board, and in the future as works become more perfect it may be raised. Such a standard ought to be so high that any authority complying with it will not cause nuisance by polluting streams. At the same time it should not be so high as to put an unnecessary burden upon the sanitary authorities who have to comply with it. I believe that the standard of purity that we have adopted is a reasonable one at the present moment for Derbyshire, and that it complies with the two conditions I have laid down. I admit that authorities who have carried out modern works are getting much better effluents than our standard suggests, and there are circumstances which may require that higher purification being maintained, as where the stream into which the effluent is turned is a small one flowing through such populous districts as there are in Staffordshire. For instance, the effluent from Langwith Colliery Houses rarely contains more albuminoid ammonia than °03 parts per 100,000, the last sample I analysed containing only -01 parts per 100,000 of albuminoid ammonia, and as will be seen from the Return sent herewith, the first three effluents on the list all contained -05 parts per 100,000 of albuminoid ammonia, and from -7 to 2°8 parts per 100,000 of nitrogen as nitrates. I do not think that a standard of albuminoid ammonia or oxygen absorbed alone is reliable, unless the nitrogen as nitrates is also taken into consideration. On the outside of the Return of Sewage Effluents issued by the Derbyshire County Council we indicate as a provisional standard for the guide of the authorities the following :— Albuminoid Ammonia.—A good effluent is one which contains less than 0°1 parts per 100,000 of albuminoid ammonia. Nitrogen as Nitrates—An effluent should contain more than ‘5 parts per 100,000 of nitrogen as nitrates. The nitrates are produced by the action of the oxygen of the air in the pores of the land or intermittent filters. The amount of nitrogen oxidized to nitrates is the best index of the efficiency of the action of the land or filters. Incubator Test.—A good effluent should be so thoroughly oxidized that it does not absorb more oxygen after incubation for one week than it does at the time of collection Shake Test.—A simple test, which can be readily applied, is to shake vigorously for one minute a bottle half filled with effluent. All frothing should disappear in three seconds. Opacity Test.—A good effluent is one which is so transparent that Pearl type can be read by a person with normal sight, through a column 10 inches in depth. As will be seen we inform the authorities of the albuminoid ammonia, the nitrogen as nitrates, and the result of the incubator test. The opacity and shake tests are made in the presence of the man in charge of the works, and, frequently the surveyors of the district councils in a rough way carry out the incubator test themselves. We do not pin our faith just to one factor alone. 3. I do not consider the suggestion as to the rate at which the effluent dissolves oxygen from surrounding water practicable, nor do I think it necessary as long as the effiuent shows only a small amount of residual unoxidized organic matter, and a store of oxygen in the form of nitrates. ‘ 4, My reasons for objecting to a standard being established as a statutory limit have been explained in my answers to Question 1. This does not, however, take away the desirability of he minimum standard being published as a general guide for the information of local authorities.