beds, and the epidemic did not cease until the filter-beds were closed. Polarite not only enters into the purification of sewage effluents, but is now being used in the laying down of filter-beds in various parts of England, and report speaks highly of it as a filtering medium. THE TREATMENT OF SEWAGE BY ELECTRICITY is the most recent of all methods, and may be said to be very promising. Mr. Santo Crimp, referring to the Webster electrical process for sewage purification, says: "When it is considered that the application of electricity is almost daily extended to new objects, and that the science is as yet in its infancy, it must be admitted that the results achieved by the Webster process are of the most encouraging nature. The time may come when our towns will be lighted with electricity by night, whilst by day the dynamos will be employed in purifying the sewage; then the loading of the sewage with chemicals, with the consequent production of large masses of sludge, will no longer be necessary." Sir Henry Roscoe, M.P., F.R.S., has carefully investigated this process, and he mentions that "the quantity of sewage operated on in each experiment was about 20,000 gallons. The reduction of organic matter in solution is the crucial test of the value of a precipitating agent, for unless the organic matter is reduced the effluent will putrefy and rapidly become offensive. I have not observed in any of the unfiltered effluents from this process, which I have examined, any signs of putrefaction, but on the contrary a tendency to oxidise. The absence of sulphuretted hydrogen in samples of unfiltered effluents, which have been kept in stoppered bottles for three weeks, is also a fact of importance. By this process the soluble organic matter is reduced to a condition favourable to the further precipitation by natural agencies." Mr. Alfred Fletcher, F.C.S., F.I.C., Inspector under the Rivers Pollution Prevention Act, states:-"The result of my examination of this process has been to convince me of its efficiency in clarifying sewage, of removing smell, and in pre venting putrefaction of the effluent. I am of opinion that such effluent as I saw at Crossness can be discharged into a river, o after passing through a thin layer of sand, even into a streami, without causing any nuisance." Description of Sample Analyses of Samples of Sewage treated by Webster's Electrical Process. The effluent produced by the electrical process, Mr. Webster states, contains about three grains per gallon of suspended matters, which consist almost entirely of oxide of iron, which is quite innocuous. Where this may be objectionable, from a entimental point of view, it can be entirely removed by filtration through a few inches of sand. The bacteria question is one which has probably still to be settled, but, in order to obtain some information as to the action of the iron compound produced by electro-chemical decomposition, some experiments were carried out, with the result that, after a given treatment, the whole of the bacteria were killed. In the case of experiments carried out in Paris, with ordinary treatment by means of iron electrodes, the results were as follows: Organisms per cubic centimetre, Raw Sewage Effluent 600 In another experiment, in which the effluent was treated still further, all organisms were destroyed. Unquestionably, this process of sewage treatment has many advantages, and may yet solve the vexed sewage problem. Mr. Webster remarks further, "That it was while working with perchloride of iron, as a purifier of sewage that the importance of iron salts, in relation to organic matter, became apparent; and it was in connection with this chemical and free chlorine gas that the idea of electrolysis suggested itself." THE "OXYGEN PROCESS." A new process, which has had its birth in Ireland, and which promises to fully realise the expectation of its promoter, is the "Oxygen Process of Sewage Purification," devised by Mr. W. E. Adeney, F.L.C., and Mr. W. Kaye Parry, M.A., C.E. It has been submitted to an exhaustive investigation both in the laboratory and at some works at Monkstown, and the results have been successful. The process, moreover, has been examined in detail by the Chief Surveyor to the Board of Public Works, and has been selected by that body for the purification of the sewage of the Lunatic Asylum at Dundrum. To be brief, the results effected by this process are the complete separation of all matters in suspension in sewage, in a state suitable for air drying and utilisation as a manure, and an effluent of any degree of purity according to the circumstances of the locality to which it is applied may demand. In this process the solid matters in the sewage are first separated from the soluble constituents by subsidence in a tank of special construction, no precipitating chemicals being employed. The destruction of the fermentable organic matters in solution. in ordinary sewage is effected by taking advantage of the power which harmless micro-organisms, the germs of which are known to be widely distributed in the earth, air. and water, have, when growing under the most favourable conditions, of rapidly decomposing such matters into carbonic acid, water, ammonia, and also nitric acid. Under proper conditions these products result directly from the decomposition of the soluble fermentable matters in sewage, without any intermediate putrefactive fermentation being set up. The formation of offensive bodies is in fact entirely avoided in this process. The essential condition for the healthy and rapid action of the organisms here referred to, is a plentiful supply of oxygen, free or combined. The necessary supply of oxygen is secured by a careful use of nitrate and manganate of sodium. One of the products of decomposition of the latter chemical is oxyhydrate of manganese; it is completely recovered by subsidence in a second tank, similar in construction to the one employed for the separation of the solid matters of the sewage. The recovered oxyhydrate of manganese may be dried and re-converted into manganate of sodium, and so may be used over and over again. It may also be employed for mixing with the solid matters of the sewage separated in the first tank to prevent putrefactive fermentation being set up in them during the process of air-drying them. Another system, THE SHONE HYDRO-PNEUMATIC SYSTEM is also of comparatively recent date, and is in operation at Eastbourne, Shirley, and Freemantle, near Southampton, Lowestoft, Stoke-on-Trent, and some other thirty or forty towns in England, as well as at the Houses of Parliament. The system appears to work admirably, and is particularly adapted to districts and towns of a low-lying nature, and where the volume of sewage is insufficient to cause what is termed a self-cleansing velocity in the sewers. Correctly speaking, the Shone System might be better described as a successful method of getting rid of sewage by means of automatic sewage ejectors, and a writer described it some time since in the columns of The Health Record as a system so elastic in its application that it can not only be successfully applied to a solitary building, but is equally adaptable to towns, cities, and rural districts. In the subjoined illustration, the working of the Automatic Sewage Ejectors is shown, and is carried out as follows: The sewage gravitates from the sewers through the Inlet Pipe A into the Ejector, and gradually rises therein, until it reaches the underside of the bell D. The air at atmospheric pressure inside the bell is then enclosed, and the sewage continuing to rise outside and above the rim of the bell compresses the enclosed air sufficiently to lift the bell, spindle, &c., which opens the Compressed Air Admission Valve E. The compressed air thus automatically admitted into the Ejector presses on the surface of the sewage, driving the whole of the contents before it through the bell-mouthed opening at the bottom, and through the Outlet Pipe B into the iron sewage rising main or high be. The sewage can level gravitating sewer, as the case may only escape from the Ejector by the outlet pipe, as the instant the air pressure is admitted on to the surface of the fluid the valve on the Inlet Pipe A falls on its seat and prevents the fluid escaping in that direction. The fluid passes out of the Ejector until its level therein reaches the cup C, and still continuing to lower, leaves the cup full until the weight of the liquid in the portion of the cup thus exposed and unsupported by the sur rounding water is sufficient to pull down the bell and spindle thereby reversing the Compressed Air Admission Valve, which first cuts off the supply of compressed air to the Ejector, and then allows the air within the Ejector to exhaust down to atmospheric pressure. The outlet valve then falls on its seat |