REPORT 421 REPORT. Royal Commission on Sewage Disposal. Ninth Report. Vol. 1, Report. Vol. 2, Evidence and Appendices. February 11, 1915. [Cd. 7,819 and 7,820.1 Part I. of the Report treats of the disposal of liquid wastes from manufacturing processes when unmixed with domestic sewage, and deals with the wastes mainly from the point of view of finding some standard to which they might conform after treatment.I t is divided into three sections, the first of which deals with wastes which pollute the stream into which they are turned owing to the suspended matter which they contain. These wastes arise from mining and quarrying operations. Coal, when brought up from the pit, is mixed with shale, clay, etc., and these matters are removed from the small coal by washing.The waste water may contain over 5 per cent. of solids in suspension, which by efficient settlement in tanks may be reduced to as little as 4 parts per 100,000, which figure is recommended as a standard, the settled water being fit to use over again. The (( tailing ” water from the crushing of tin, lead, and zinc ores contains over 2. per cent. of suspended solids, Experiments showed that the solids could be reduced by settlement to 6 parts per 100,000, with an effluent practically free from lead or arsenic, although there might.be, on occasion, zinc and copper in solution. Effluents from clay-settling pits and stone-quarry washers also might be reduced to the standard of 6 parts per 100,0001 for suspended solids. The second section deals with wastes which are polluting by reason of the dissolved impurities they contain 8s well as the suspended impurities. They com- prise effluents from the cotton, woollen, and paper industries. Soluble salts of a, poisonous nature may be present, also acids and alkalis, and colloid suspended niatter such as wool and vegetable fibres, grease, gum, and starch.Some of these wastes are particularly objectionable in a stream. At the same time, much of the suspended matter is very difficult to remove, and the Commission admits that efficient means of purification are not practicable nor available.For wastes from the dyeing and printing of cotton goods, precipitation with lime or alumina, followed by settlement or filtration, will usually reduce the suspended solids to 4 to 6 parts per 100,000; although there would still be much matter in solution which would absorb oxygen.In cotton bleaching, the kier liquors obtained in boil- ing the cloth to extract size and gum before bleaching are especially polluting, and the Commission made experiments on their biological purification. It was found if the caustic alkali was neutralised with carbon dioxide and the liquid either filtered through a matured sewage filter or digested with sewage sludge and then filtered, that much organic matter was removed and a more fully oxidised effluent produced.422 REPORT I t is recommended that the kier liquor should be kept separate from the rest of the waste and turned into the sewers.The wastes from the dyeing and scouring of wool are less polluting than those from cotton.They contain up to 500 parts per 100,000 of suspended solids, which can be removed very completely by means of precipitation with lime and alumina, followed by streaming filtration, and in some cases by settlement alone. The effluent should not contain more than 4 parts per 100,000 of solids in suspension. The wastes from paper mills are usually very dilute, but contain a good deal of organic matter in solution.Treatment in settling tanks, followed by percolating filters, has been tried, but the purification effected was much less than with sewage; therefore the Commission do not recommend any standard except for solids in suspension-namely, 4 parts per 100,000 for wood pulp mills and 6 parts for other mills. The third section includes wastes which are polluting mainly from the dissolved solids which they contain, and for which in some cases practicable methods of purification are not yet available.These wastes are very varied in origin, but may be dividied into two classes-those containing putrescible organic matter, and those containing injurious chemicals. The first class being polluting liquids in the same way that sewage is polluting, additional treatment to simple clarification should be required.Of these, wool scouring liquor, where it occurs alone, is one of the most polluting. I t consists of a soapy solution containing about 1 per cent. of fat in suspension and 0-3 per cent. of potash in solution. Some recovery of fat and potash has been made, birt tha processes have been considered too expensive.The usual method of treatment in use is to acidify the waste, run off the acid liquid into a sewer or stream, and press the fat in a hot press. Many laboratory experiments were made by the Commission upon the direct precipitation of the waste, and it was found that ferric chloride was the best precipitant, removing about 99 per cent. of the fat. A series of large scale experiments was then made at a mill accompanied by recovery of the fat, and the cost was worked out i n detail.'The Commission were satisfied that the process could be worked at a profit, but the 6rm at whose mill the experiment was made did not accept this conclusion. The Commission found that the liquid after precipitation was amenable to filtration through matured clinker, becoming non-putrescent.They recommend, therefore, &hat the standard for this waste should be a dissolved oxygen absorption not exceed- ing 4 parts per 100,000 in five days, in addition to a limit of 4 parts of solids in .suspension. It is pointed out that these effluents and the sludges may contain anthrax spores, and are therefore a possible danger to animals grazing on land to which they may be applied.Brewery waste contains spent yeast and hops in suspension, and much dissolved carbonaceous matter, which undergoes acid fermentation with subsequent putrefaction. It can be treated readily along with sewage unless it is in excessive amount, and it can be treated by biological methods when it is to be turned into a stream alone.Observations were made on treatment in a septic tank and percolating filters, and in triple contact beds, and in each case it was possible to produce a good effluent. The acid liquid is very polluting, and still contains much fat.REPORT 423 When applied to land, the development of acidity requires to be prevented by the addition of lime. The standard recommended is 4 parts suspended solids and 4 parts dissolved oxygen absorption in five days.The same standard is fixed for steep water from maltings, which can be treated in the same way. The treatment of distillery waste was described in the Sixth Report, and the standard now fixed is 3 parts suspended solids and 2 parts dissolved oxygen absorption. Fellmongers’ wadte and tanners’ waste are exceedingly polluting liquids, containing large amounts of nitrogenous organic matter, and having an offensive smell.Labora- tory experiments proved that the wastes were amenable to biological filtration, and it is recommended that this should always be done before turning the waste into a stream. The sludge produced is liable to contain arsenic and anthrax spores. I n sewered areas the waste may be turned into the sewer.The same standard as for brewery waste is fixed also for dairy waste, including creameries, cheese and condensed milk stations, and butter factories. These wastes contain 0.1 to 0.2 per cent. organic nitrogen, and have an acidity of 0.2 to 0.5 per cent. The waste, mixed with sewage, is readily purified by biological filtration, and i t has been treated on land, I n towns it may be received into the sewers without treatmont other than the removal of most of the grease.Margarine waste is similar, and the grease should always be removed before turning into a sewer. The second class of these wastes do not undergo putrefaction ; indeed they fre- quently delay its occurrence in the stream, and they are poisonous to fish and plants.The waste from the distillation of shale oil consists of acid and alkali wash waters and spent gas liquor. I t is treated by settlement and filtration through heaps of spent shale. The effluent is a good one, although it may contain nearly 1 part per 100,000 of zinc. The standard suggested is 4 parts suspended solids and 4 parts dissolved oxygen absorption in five days. Metal waste from galvanising and tin-plate works is an acid solution of sulphate or chloride of iron.I t should not be turned into a stream, but should be evaporated. The dilute washings, however, may be neutralised with lime or sodium carbonate, and, after settling the suspended solids to 6 parts per 100,000, may be turned into a stream. Many experiments were made on the purification of spent gas liquor, but the Commission are unable to recommend any method of treatment, except possibly percolation through spoil heaps at collieries ; and the only alternative is evaporation.A partial purification process has been successful, in which the liquor is diluted with previously treated liquor, and passed through biological percolating filters ; about 80 per cent. purification is produced, but the method is considered expensive.When the waste is produced in a town it may be admitted to the sewers, provided it does not exceed 2 per cent. of the volume of the sewage, as it has been proved that in this amount it does not interfere with tank and filter treatment. Another waste for which the Commission are unable to suggest any treatment is the sulphite cellulose liquor of the paper industry, and it is stated that this liquid should not be discharged into a stream.The standard fixed for both wastes is the same as for brewery waste.424 REPORT Finally, the Commissioners state that, although their labours are concluded, there is still need for investigation and research, and they again press for the formation of a Central Authority, which would not only control methods of treat- ment, but originate new and improved ones.Part 11. of the Report deals shortly with the disposal of liquid and solid domeshic refuse in rural areas. Where the water-supply is adequate, water carriage is the most satisfactory system, but where the supply is. inadequate, dry closets are open to little objection. The use of dry earth in these closets is of gre& importance, and the contents should be frequently removed by means of pails.Domestic waste water may be conveyed to a cesspool or distributed over a garden, and ample garden space should be provided. The Appendices to the Report contain full details of the Commissioners’ experiments on the. purification of brewery waste, wool-scouring waste, and cloth scouring and dyeing waste.There are also two reports comparing the manurial value of natural and de-greased sewage sludge. I t was found that the removal of grease did not increase the manurial value, and in some cases decreased it. Final Report, February 11, 1915 [Cd. 7,82I].-This is a general summary of previous reports, and no new conclusions nor recommerJdations are contained in it. The Commissioners recall that their inquiry has extended over sixteen years, and that nine reports have been issued, four dealing mainly with the purification of domestic sewage discharging into streams, two with the discharge of sewage into tidal waters, and three with the discharge of trade wastes. The Commissioners record that two of their recommendations have been adopted. Shell-fish ownera agreed to close sewage polluted layings, and, consequently, oysters are far safer articles of diet now than formerly. A plant was erected €or the purificstiori of distillery waste according to the Commissioners’ directions, and has proved itself capable of producing an effluent at a reasonable cost which is not injurious to fish. Other similar plants are being erected. J. H. J.