SEWER GAS.

Taranaki Daily News, Volume LVII, Issue 34, 30 June 1914, Page 6

SEWER GAS.

NEW MOTIVE POWER. NEW ZEALANDER'S INVENTION.

. _ Sydney, Juno 10. invention of Mr IS. Walshaw, a Now Zealander, now residing in Parramatta, for the utilisation of sewer gas for power purposes, is attracting a good deal of attention here. Liko all other inventors, he has liad to fight against an army of prejudice, but people are realising now that his invention has given to the world a motive power that will remain with it for all time.

The. invention has paßSei the experimental stages. The Parramatta Council has, on tlie advice and under the direction of i'lr Wilshaw, had an engine installed at the sewage pumping station. This engine of sixteen horso : power is (says the Sydney Sun) driven by gas drawn directly from the septic tanks through 30(H) feet of pipes. No structural alterations have been made to t'he engine; it is just tlie same as an engine used for coal gas. It was installed on May 0. ( It has been running continuously for a month, operating a 6in. centrifugal pump, pumping up 45,000 gallons of sewerage from tlie low level to the higher level of the septic tanks against a head of about 35 feet. There could be no great;r test of its''efficiency. The sewage which the'pump lifts generates) tko powur wliick operates the pump. So perfect is the running of the machinery that the engine runa all niglst without attention. The installation of this engine is saving the Parramatta Council £lO a week in wages for a third shift, and in fuel and other incidentals. Hitherto, the work was done by two 12 liors«-power engines driven by steam'. The cost of the new installation was £1(98 10s 4d. In twenty weeks, the engine driven bv the sewer gas will haw saved the whole cost.

"A power that can do that in bo small an installation is worth more than passing consideration," observes the Sun. "Indeed, it is likely to revolutionise the power production of the world." GENjEIIATING THE GAS.

The g<is from the septic tanks, after passing through 3000 feet of pipe, goes ■ into an expansion box. .This being of Urge diameter causes a more regular flow than if drawn direct from the 3in pipe. The gas enters the combustion ckambcr of the engine through a l%in. pipe, and is there magnetically ignited. To all intents and purposes the engine works exactly the same as it would under coal gas; but it is not subject t® the back firing which occasionally takes place with the gas engina. "So fan as my experiments have gone," -Mr VValshaw told an interviewer, "the gas from septic tanks is not a good illuminant. It burns with a red flame. [ As a gas for the production of powor j it is equal, if nnt superior, to ordinary coal gas--and can bo used for the | production of electricity for lighting ! and heating purposes. T'he gas in it- ! self is obnoximia, and I hardly think it ; will bo used for illuminating purposes, i The gas gees through a slight prepar- | ation. The generation of the gases in i tlse septic tank is assisted-greatly by a , section of partial -carbonation 'by the'insertion of sniffle valves, or non-return valves, which allow a current of air to he drawn over the top of the sewage by the suction of the engine. This causes the pas to generate more freely. Some authorities contended that the admission of air into septic tanks would generate a highly explosive gas, probably a little too dangerous to handle. Experiments have proved the contrary. ; The ga?, after undergoing this process, 1 ia easier to handle than ordinary coal i gas, acetylene or any. other commercial ! gas. There is no highly-explosive gas to jbe found in any of the septio tanks. | After the gas has been practically car- | bonated it is necessary to put it through j another process of aeration, so that it really is a non-explosive until it enters I thf combustion chamber of the engine, j As a matter of fact, a greater quantity of air in needed with the gas than with j any other gas used for motive power, | HYGIENIC ADVANTAGES

"It is not so much on account of its commercial value that I am proud of the discovery a* for its hygienic advantages," continued t'he inventor. "These gases, let them say what they like about the perfection of septic tanks, are highly obnoxious. They are of great density, and much difficulty will be foani in making vents to carry them away under the different changes of atmosphere. Till; gas can now be entirety destroyed whilst at the 1-k.iik? time being used for commercial purposed" In the earlier stages of experimenting with the gas from septio tanks, Mr Walshaw had a !-;na!l' plant initialled, and ran a dynamo for 175 lights. Several people were under the-impression then that gas was leaking from the mains into the sewers. That idea has now been dispelled, though there are still many sceptics. .SEWAGE AX.O ELECTRICITY*

"Every town with a sewerage, system Can now have a power and lighting scheme," continued Mr Walshaw. "I was in Goulbnrn a little while ago, and I learned that the council had rejected a sewerage system for an electric lighting scheme. That was foolish. They could have had both at the cost of one —the sewerage system would have provided the motive powor for the dynamos. A town of 111.000 or 1-2,000 people, with a sewerage system installed could generate suflicient gas from the septic tanks to light the whole of the town with electricity. The town would require up to 150 horse-power. For an electric lighting scheme such 'as this, gasometers would be necessary to draw off and store the gases as they were gencrated. Large houses containing up to 30 persons could, through the installation of a septic Uutk, generate sufficient gas to give power for the driving of a small engine to light the household. "The simple secret of the septic tank is the breaking up of solids into liquids. The first action is putrefaction, and the next bacterial action and liquefaction. During the latter processes, the gases are given off, and it is at this point that sewer gases are utilised. It stands to reason that these gases must escape somewhere, otherwise they are forced back into suspension in the liquid, and this causes tile offence when the liquid is exposed to the atmosphere. By uti- ' Using the gas the moment it is generated, a, danger is removed, and the surroundings »f the sewrags outlets and septic tanks made perfectly healthy. The success of the scheme of utilising se.wor gas. however, depends upon tlic sewage being from a domestic source. Anything retarding the generation of the gas is detrimental to the working of the tank. The introduction of any trade affluents into the sewers running to the septic tanks-—a thing which should always be guarded against—would altogether upset the action of the tank.