ABSTRACTAir pollution is most important from the public health point of view, because everyindividual person breathes approximately 22000 times a day, inhaling about 15 to 22 Kg of air daily. Polluted air causes physical ill effect decides undesirable aesthetic and  p h y s i o l o g i c a l   e f f e c t s .   A i r   p o l l u t i o n   c a n   b e   d e f i n e d   a s  a d d i t i o n   t o   o u r   a t m o s p h e r e   o f   a n y material, which will have a deterious effect on life upon our planet. The main pollutantscontribute by automobiles are carbon monoxide (CO), unburned hydrocarbon (UBHC), oxidesof nitrogen (Nox) and Lead. Automobiles are not the only source of air pollution, other sourcessuch as electric power generating stations, industrial and domestic fuel consumption, refuse burning, industrial processing etc. also contribute heavily to contamination of our environmentso it is imperative that serious attempts should be made to conserve earth’s environment fromdegradation. An aqua silencer is an attempt in this direction, it is mainly dealing with controlof emission and noise. An aqua silencer is fitted to the exhaust pipe of engine. Sound producedunder water is less hearable than it produced in atmosphere. This mainly because of smallsprockets in water molecules, which lowers its amplitude thus, lowers the sound level. Becauseof this property water is used in this silencer and hence its name AQUA SILENCER. The noiseand smoke level is considerable less then the conventional silencer, it is cheaper, no need of catalytic converter and easy to installCONSTRUCTIONBasically an aqua silencer (fig. 1) consists of a perforated tube which is installed at theend of the exhaust pipe. The perforated tube may have holes of different diameters. The very purpose of providing different diameter hole is to break up gas mass to form smaller gas bubbles The perforated tube of different diameter is shown in fig. 2. Generally 4 sets of holesare drilled on the perforated tube. The other end of the perforated tube is closed by plug.Around the circumference of the perforated tube a layer of activated charcoal is provided and further a metallic mesh covers it. The whole unit is then placed in a water container. A small opening is provided at the lop of the container to remove the exhaust gasesa n d   a   d r a i n   p l u g   i s   p r o v i d e d   a t   t h e   b o t t o m   o f   t h e   c o n t a i n e r  f o r   p e r i o d i c a l l y   C l e a n i n g   o f   t h e container. Also a filler plug is mounted at the top of the container. At the inlet of the exhaust pipe a non-return valve is provided which prevents the back flow of gases and water as well.WORKING PRINCIPLEAs the exhaust gases enters in to the aqua silencer, the perforated tube converts highmass bubbles in lo low mass bubbles after that they passes through charcoal layer which again pur i fy   the gases .   I t   i s  h igh ly porous and  posses  ex t ra   f ree  va lences   so   i t  has  h igh absorp t ioncapacity.After passing over the charcoal layer some of the gases may dissolved in to the water and finally the. exhaust gases escape through the opening in to the atmosphere. Hence aquasilencer reduces noise and pollution.

1 . M o u n t i n g s 2 . F il l e r   P l u g 3 . C h a rc o a l   L a y e r 4 . P e r fo r a t e d   T u b e   5 . W i r e   Me s h 6 . D r a i n   P l u g

EFFECTS OF DISSOLVED GASES ON WATER The water is a good absorbing medium. In aqua silencer the gases are made to bedissolved in water. When these gases dissolved in water they form acids, carbonates, bicarbonates etc,Action of dissolved SO2:-When Sox is mixed in water, it  form SO2, SO3, SO4, H2SO4, H2SO, i.e. sulfur Acid (H2SO3,), it forms Hydrogen Sulphide which causes fol rotten egg smell, acidify and corrosionof metals.Action of dissolved CO2:-

The dissolved carbon dioxide forms bicarbonate at lower PH and Carbonates at higher PH. This levels 40-400 mg/liter. The form a scale in pipes and boilers. The carbon dioxidemixes with water to form Carbonic acid. It is corrosive to metals and causes green house effect.Effect of dissolved NOx :-The  Ni t rogen   in  wate r  under  goes  Oxida t ion   to   form ammonia ,  Ni t ra te ,  Ni t r i t e ,  Ni t r i cacid. This synthesis of protein and amino acids is effected by Nitrogen. Nitrate usually occursin trace quantities in surface water. A limit of 10 mg per liters Nitrate is affordable in drinkingwater.METHODS TO CONTROL THE WATER POLLUTIONIn aqua silencer the water gets polluted by the dissolved gases As in above topics saidthese gases are mixed with water to form carbonate, acids like carbonic acid, sulfuric acid, and Nitrous acid etc. the petroleum products contains phenols which gives suffocating smell. Thesulfur gas mixes with water to form hydrogen sulfide, which give rotten egg smell. Theseshould be controlled to minimum the water pollution.There are two methods:1 ) L i m e   w a t e r   w a s h   m e t h o d 2 ) A b s o r p ti o n   p r o c e s sLIME WATER WASH METHODThe water is treated with the calculated quantities of slaked lime. One should have thequantitative analysis of water to go for this process. After mixing the heavy precipitates settledown as sludge at the bottom of the tank are removed from time to time. Lime can neutralizeany acid present in the water. SO2, gases are removed from the flue gases forming calciumsulphate. The precipitates dissolved carbon dioxide as calcium carbonate and converts bicarbonate ions into carbonates. The equations are given below.The SO2gas is removed from the flue gases forming calcium sulphateCa(OH)2+ SO2........ CaSO3+ H2o Neutralizes any acid present in water 2HCL + Ca(OH)2..........Cacl2+ 2H2H2SO4+ Ca (OH)2........... CaSo4+ 2H20Precipitates bicarbonate as calcium carbonateCO2+ Ca(OH)2........CaCO3+2H2OPrecipitates bicarbonate as calcium carbonateCa(HCO3)2+ 2Ca (OH)2......... 2CaCO3+ 2H20Converts bicarbonate ions (Like NaHCO3, KHCO3etc.) into carbonates. NaHCO3+ Ca(OH)2............ CaCO3+ H20 + Na2CO3LIMITATIONS OF LIME WATER WASH METHODvAmount of neutralization capacity is limitedvIt is very difficult to handlevBridging and form are formedvIt is expansivevRegeneration is possiblevLime in any form it is difficult to handleABSORPTION PROCESS

Activated charcoal is available in granular or powdered form. As it is highly porous and possess free valencies. So it posses high absorption capacity.Ac t iva ted carbon   i s more  wide ly used   for the   removal o f t as te  and  odorous   f rom the  public water supplies because it has excellent properties of attracting gases, finely divided solid particles and phenol type impurities, The activated carbon, usually in the powdered form isadded to the water either before or after the coagulation with sedimentation. But it is alwaysadded before filtration. Feeding devices are similar to those used in feeding the coagulants.ADVANTAGES OF ABSORPTION PROCESS.vIt increases the coagulation power of the process.vIts use reduces the chlorine demand.vThe excessive dose of activated carbon is not harmful.vThe treatment process is very simple and it requires nearly no skill.vThe efficiency of removing color, odour and taste is quite high.vIt can be easily regeneratedvIt has excellent properties of attracting gasesCONCLUSIONThe aqua silencer is more effective in the reduction of emission gases from the engineexhaust using perforated tube and charcoal,vBy using perforated tube the backpressure will remain constant and the soundlevel is reduced.vBy using perforated tube the fuel consumption remains same as conventionalsystem.vB y   u s i n g   w a t e r   a s   a   m e d i u m   t h e   s o u n d   c a n   b e   l o we r e d   a n d   a l s o   b y   u s i n g activated charcoal in water we can control the exhaust emission to a greater level.vThe water contamination is found to be negligible in aqua silencer.vIt is smokeless and pollution free emission and also it is very cheap. This aquasilencer’s performance is almost equivalent to the conventional silencer. It can be  a l so  used  bo th for two  whee le rs and   four  whee le rs and a l so  can be  used   in industries.