,,comparison ,,of ,,methods ,,of ,,sewage ,,purification ,,by ,,theodore ,,clifford ,,phillips ,,and ,,edward ,,john ,,schneider ,,thesis ,,for ,,degree ,,of ,,bachelor ,,of ,,science ,,in ,,municipal ,,and ,,sanitary ,,engineering ,,college ,,of ,,engineering ,,university ,,of ,,illinois ,,presented ,,june #aijj ,,university ,,of ,,illinois ,may #ca1 #aijj4 ,,this ,,is ,,to ,,certify ,,that ,,the ,,thesis ,,prepared ,,under ,,my ,,supervision ,,by ,theodore ,clifford ,phillips and ,edward ,john ,schneider ,,entitled ,comparison of ,methods of ,sewage ,purification ,,is ,,approved ,,by ,,me ,,as ,,fulfilling ,,this ,,part ,,of ,,the ,,requirements ,,for ,,the ,,degree ,,of ,bachelor of ,science in ,municipal and ,sanitary ,engineering4 ,arthur ,m4 ,talbot ,,head ,,of ,,department ,,of ,municipal and ,sanitary ,engineering4 ,contents ,comparison of ,methods of ,sewage ,purification ,dilution ,irrigation ,intermittent ,downward ,filtration ,chemical ,precipitation ,septic ,tank ,contact ,bed ,discussion ,conclusion ,comparison of ,methods of ,sewage ,purification4 ,the disposal of sewage is one of the most important problems that confront the municipal and sanitary engineer to-day4 ,the study of this subject dates back to #ahdd when the ,healths of ,towns ,commission of ,london made the report which first showed the real course of the rapid increase in the death rate of the larger cities4 ,in this country practically nothing was done until #ahgb when the ,massachusetts ,legislature instructed the ,state ,board of ,health to investigate and report on the subjects of sewerage1 sewage disposal1 and the pollution of streams1 and to-day ,massachusetts leads in the investigation of the best methods of sewage disposal4 ,six different methods for the treatment of sewage are now in use4 ,these methods are used separately or in combination1 the choice depending upon local conditions and the amount of purification required3-- ,these methods are3 #a-- ,dilution4 #b-- ,irrigation4 #c-- ,intermittent ,downward ,filtration4 #d-- ,chemical ,precipitation4 #e-- ,septic ,tank4 #f-- ,contact ,bed4 ,the purpose of this thesis is to investigate each method and make a comparison along the following lines3 #a-- ,purification4 #b-- ,capacity4 #c-- ,applicability4 #d-- ,cost4 ,dilution ,disposal of sewage by dilution is the most common method at the present time1 and no doubt will continue to be for some time to come where the stream or body of water is not used for domestic purposes4 ,under certain conditions this affords a satisfactory solution of the problem4 ,however1 if the water into which the sewage is discharged is a source of water supply1 two very important questions arise4 ,they are3 #a--;,how large must the dilution be8 #b--;,how far must the polluted stream flow before the water way may be used with safety to public health8 ,in #ahfg ,dr4 ,letheby and others in ,england made the statement that if sewage is diluted at least twenty times its volume1 it will not only be made inoffensive but be thoroughly destroyed after flowing a dozen miles or more4 ,the ,rivers ,pollution ,commission of ,great ,britain in #ahgh maintained that no river in ,england was long enough to allow of a complete disappearance of sewage matter discharged into it4 ,mr4 ,f4 ,p4 ,stearns in an article on ,the ,pollution and ,self-,purification of ,streams in the ,massachusetts ,state ,board of ,health ,report #ahij gives a table showing1 8,the calculated composition of sewage for different degrees of dilution in a running stream04 ,a comparison was made of the ,blackstone and ,merrimack rivers1 and extended over three years4 ,it was from this investigation that the ,commissioner of the ,city of ,chicago reported that the flow of the ,chicago ,drainage ,canal should be four cubic feet per second per #ajjj inhabitants4 ,the purification by dilution may be due to three things3 #a-- ,oxidation of organic matter4 #b-- ,subsidence4 #c-- ,destruction of the organic matter by small animals and plants4 ,the oxidation is a very slow process and depends mainly upon bacterial life and conditions favorable to it4 ,subsidence depends upon the difference in the specific gravity of the suspended matter1 and the clarification is increased as the velocity is diminished4 ,in regard to the destruction of the organic matter by small animals and plants ,dr4 ,sorby says1 7,journal ,royal ,microscopic ,society1 #ahhd p4 #ihh47 8,it appears to me that the removal of impurities from rivers is more of a biolytic than a chemical question1 and it is most important to consider the action of minute animals and plants1 which may be looked upon as being indirectly most powerful agents40 ,irrigation ,although the method of broad irrigation has been carried on successfully in several of the largest cities of the old world1 it has not been used to any great extent in the ,united ,states1 except at a few state institutions in the east1 and in the arid districts of the west4 ,several years ago this method of disposal was given much attention as it was thought the sewage if used would yield large profits1 but more recent information shows conclusively that such is not the case4 ,perhaps the most noticeable examples of this system that are now in operation in the ,united ,states are the plants at the ,state ,hospital of the ,insane1 ,worcester1 ,mass41 at the ,rhode ,island ,state ,institute1 and at the ,reformatory at ,concord1 ,mass4 ,in all cases the labor was done by the inmates so that it is not possible to get a fair statement of the cost4 ,general information regarding the use of sewage for irrigation in the west may be obtained from ,baker and ,rafters' 8,sewage ,disposal in the ,united ,states04 ,undoubtedly the best example of sewage farming is at ,berlin4 ,the following summary is given by ,james ,h4 ,fuentes1 ,m4 ,am4 ,soc4 ,c4 ,e41 in ,no4 #b4 ,vol4 #dj of the ,engineering ,record4 ,the average quantity of sewage pumped to the farms and distributed amounts to from #f1jjj1jjj to #g1jjj1jjj gallons per acre per year1 or in other words each acre serves for #gej people4 ,the area farmed is divided into small beds about #aej by #bjj feet separated from each other by slight embankments and ditches for distributing the sewage over the surface4 ,the sewage is admitted into the carriers from the force mains through checking chambers made of woven willow and posts driven into the sand4 ,the farms are said to yield small profits over the expenses of working them1 consequently contribute scarcely anything toward the cost of pumping the sewage4 ,the great reason why this method of disposal has been possible and profitable in a degree at ,berlin is that this large and beautiful city lies in the midst of an extensive sandy area1 the greater part of which in the immediate neighborhood is quite sterile and therefore comparatively thinly populated4 ,better conditions for such sewage farms could not exist4 ,statistics compiled by ,chas4 ,s4 ,swan1 ,m4 ,am4 ,soc4 ,c4 ,e4 in his paper1 ,notes on ,european ,practice in ,sewage ,disposal1 in ,jour4 ,assn4 of ,eng4 ,soc4 ,vol4 #g ,no4 #g shows the volume of sewage per acre per day 7yearly average7 to vary from #baee to #bidej gallons1 and the average depth per annum varies from #b4d to #cb4h feet4 ,the nineteenth annual report of the ,massachusetts ,state ,board of ,health #ahhh states that on an ordinary farm in ,massachusetts #bejj gallons per acre per day are as much as could be applied to any valuable grass crop4 ,this would require such a large area for large cities that irrigation could not be depended upon for preventing the pollution of streams4 ,it is evident from the above report that the irrigation system can be used to advantage only where large tracts of low land can be obtained at a low cost1 and where help and plenty of cheap labor can be obtained4 ,intermittent ,downward ,filtration ,filtration means the concentration of sewage on an area of especially chosen porous ground1 or on an especially prepared bed as small as will absorb and purify it4 ,the intermittency of application is a necessary requirement even in suitably constituted soils wherever complete success is arrived at4 ,the reason for this is that free oxygen is indispensable to nitrification and the nitrifying organism4 ,this method has been in operation only during the last thirty years1 and the correct theory of its action has been found out within the last ten years4 ,dr4 ,frankland1 in the first report of ,rivers ,pollution ,commission of ,england1 shows that not only a chemical action but also a biolytic action takes place with the assistance of minerals and the oxygen of the air4 ,this biolytic action is known as nitrification1 and consists in the oxidation of the nitrogen of ammonia and its ultimate conversion into nitric acid4 ,this change takes place in two stages1 each characterized by a distinct organism4 ,the office of one of these organisms is to convert ammonia into nitrite1 while the other converts nitrites into nitrate4 ,the bacteria are present or quickly develop in the sewage which may be considered a nutrient medium for them by reason of containing a large amount of their natural nitrogenous food4 ,these organisms1 according to ,warrington1 may be separated by successive cultivations in favorable media2 from a potassium nitrate solution with no ammonia we may obtain nitric organism alone2 from an ammonium carbonate solution we may obtain nitrous organisms in a pure state4 ,it is a noticeable fact that frost checks nitrification1 but several satisfactory methods have been used so that no serious objection can be raised to intermittent filtration on this ground4 8,the purification of sewage by this method depends upon the oxygen and the time of action0 7,hazen74 ,to obtain the highest efficiency the sewage must be applied intermittently and there must be a large percentage of voids in the sand4 ,experiments made on especially prepared beds at ,lawrence1 ,mass4 show that by treating #hejjj gallons per acre per day1 #id percent of the organic matter and #ih percent of the bacteria are removed1 and by treating #fj1jjj gallons per acre per day1 #ig to #ii percent of the organic matter may be removed4 ,the above data shows that #ajj1jjj may be successfully treated with a five foot bed of sand4 ,the writers inspected the intermittent downward filtration plant at ,mendota ,illinois and the following data were obtained4 ,the city has a population of about #fjjj with #h miles of sewers and #baj house connections4 ,the average daily flow is about #cej1jjj gallons although during the rainy season there is a considerable amount of ground water present4 ,the disposal plant was constructed under the supervision of the ,iowa ,engineering ,company of ,clinton1 ,iowa1 on a #ae acre tract of land1 one and a half miles south of the city4 ,although original plans called for #ah beds with five feet of gravel1 only four beds each #bge feet by #ge feet were finished1 and instead of #e feet of ground only #bd inches was used4 ,the plant was complete in ,july #ahii and was operated until ,december1 when it was discontinued on account of cold weather1 it not being considered necessary to operate it during the winter4 ,from ,december until ,april the sewage was discharged directly into a creek which runs along one side of the land4 ,the beds have no automatic device for distributing the sewage at definite intervals of time1 but are connected with the main sewer by a number of gate valves which were regulated by the attendant4 ,the sewage is distributed by means of a wooden sluice way which extended the entire length of the bed and has six inch openings on the side every #af feet which gave a fairly even distribution4 ,although no analysis of the sand and gravel was made1 it was apparent that the uniformity coefficient was very large4 ,the material was shipped a distance of #ij miles and resembles ordinary ballast used for rail roads4 ,the largest pieces were thrown along the sluice way to prevent excessive washing4 ,the finest of the sand was of a size which would be considered too fine for good mortar sand4 ,no attempt was made to screen the material4 ,the gravel would not be considered first class for filtering beds4 ,samples of the sewage and effluent were taken at two different times4 ,the first was between #i3jj and #aj3cj ,a4 ,m41 ,april #bj1 #aijj4 ,until the day before no sewage had been applied to the beds since last fall4 ,the second collection was made two weeks later1 when samples of the sewage and effluent were collected at intervals of one hour during the day1 and mixed into composite samples4 ,the sewage was taken from a manhole just above the beds1 and the effluent from the outlet of the underdrain about #ijj feet below the beds4 ,the analysis is given in ,table ,i4 and the results show that the beds are not working as efficiently as might be expected from a first class plant4 ,this may be accounted for from the fact that the filtration is too rapid and that the material which is less than two feet in depth is not suitable for such a purpose4 ,,table ,i4 ,analyses of ,sewage and of ,effluent from ,intermittent ,downward ,filtration ,plant at ,mendota1 ,ills4 ,parts per #a1jjj1jjj ---------------------------------------- ------------------------------------ ,april #bj1 #aijj ,may #d1 #aijj ---------------------------------------- ---------------------------------- ,sewage,effluent,efficiency,sewage,efflu ent,efficiency ---------------------------------------- ------------------------------ ,oxygen consumed3 ,total #dh4e #f4ej #hf #bg4g #ab4j #ee ,in suspension #cc4d #ae4e #d4f #gj ,in solution #ae4a #ab4b #g4d #dj ,nitrogen as albuminoid ammonia ,total #aj4d 4#cb #ig #c4fh 4#gfh #gi ,in suspension #i4bh #b4haf 4#daf #he ,in solution #a4ab 4#hfd 4#ceb #ei ,total organic nitrogen#ag4ifj 4#ibj #ie #i4fj #a4hfj #ha ,in suspension#ae4jd #g4ejj #a4aeb #he ,in solution #b4ib #b4ajj 4#gjh #ff ,nitrogen as free ammonia #g4bj #b4dj #fg #c4hd #a4bh #fg ,nitrogen as nitrites 4#fge 4#cge #jjj #jjj ,nitrogen as nitrates #d4jj #ah4jj 4#abj 4#abj ,chlorine as chlorides #ec4j #di4j #dg4j #dd4j ---------------------------------------- ------------------------------------ ,chemical ,precipitation ,when certain chemicals are added to sewage a precipitate is formed which under favorable conditions may carry down with it all the suspended matter as well as a portion of the dissolved organic matter4 ,the addition of the chemicals together with the working of the various appliances for grinding and mixing the same1 the decanting of the effluent1 and the caring for the sludge all constitute what is known as the chemical treatment of sewage1 the complete process being in reality partly chemical and partly mechanical4 ,the following matter concerning the theory of precipitation is taken from ,baker and ,rafter's ,sewage ,disposal4 ,the reagents chiefly used at the present time are lime1 sulphate of alumina1 and ferrous sulphate4 ,in the case of lime1 there is a combination of some of the lime and with free and partially combined carbon dioxide to form an insoluble carbonate of lime4 ,there is probably a further combination of an additional part of the lime with a portion of the organic matter in solution4 ,the insoluble substances so formed sink to the bottom1 carrying with them the major portion of the suspended matter in the sewage in the form of sludge4 ,sulphate of alumina exercises a precipitating effort by a combination of the sulphuric acid with lime while alumina hydrate forms a flocculent precipitate which entangles and carries down the suspended organic matters4 ,on ,november #aa1 #ahii the writers visited the chemical precipitation plant at ,madison ,wisconsin and through the kindness of ,mr4 ,mc,clellen ,dodge1 ,city ,engineer1 were shown the plant at that time in operation4 ,the sewage was screened as it came from the city and emptied into a well4 ,here it was dosed with lime and then pumped to one of the four settling tanks4 ,these are #ae feet deep and #be feet in diameter4 ,the sewage enters near the bottom of the tanks4 ,the sludge settles to the bottom and the effluent rises to the top1 where it is carried away to three of the filter beds4 ,these three beds are in continuous use4 ,a fourth bed is out of use while it is washed and allowed to rest for one day4 ,the total area of the beds is #eeej square feet4 ,the flow through the beds is about #h1jjj1jjj gallons per acre per day4 ,the company that constructed and operated the plant agreed that the effluent on analysis should be found to be equal to the waters of ,lake ,mendota and the analyses of ,lake ,mendota water which was adapted as a standard of purity is reproduced in the ,engineering ,news ,vol4 #db ,no4 #bf p4 #dad4 ,samples of the crude sewage tank effluent and filter effluent were taken and analyzed as shown in ,table ,,ii4 ,a comparison of this table with the standard shows that in no particulars does the effluent from the plant come up to the standard4 ,the company has since abandoned the contract and the city is considering other methods of disposal and purification 8in order that there may be no more fiascos in civil engineering at the seat of this well known school40 7,university of ,wisconsin7 ,,table ,,ii4 ,analyses of ,sewage and ,effluent from ,chemical ,precipitation ,plant and ,filter ,beds at ,madison1 ,wis4 ,parts per #a1jjj1jjj4 ---------------------------------------- ------------------------------------ ,november #bc1 #aijj ---------------------------------------- ----------------------------------- ,chemical ,precipitation ,filter-beds ---------------------------------------- ---------------------------------- ,sewage,effluent,efficiency,sewage,efflu ent,efficiency ---------------------------------------- ------------------------------ ,oxygen consumed3 ,total #ch4c #bc4b #dj #bc4b #ad4c #ch ,in suspension #bg4b #ab4a #ee #ab4a #c4e #ga ,in solution #aa4a #aa4a #jj #aa4a #aj4h #c ,nitrogen as albuminoid ammonia ,total #h4cb #d4jj #eb #d4jj #b4df #ch ,in suspension #g4ab #b4ef #fd #b4ef #a4fj #cg ,in solution #a4bj #a4dd -#bj #a4dd 4#hfd #dj ,total organic nitrogen#ae4cj #e4cb #fg #e4cb #c4ef #cc ,in suspension#ab4dh #a4hf #he #a4hf #a4ed #ag ,in solution #b4hb #c4df -#bc #c4df #b4jb #db ,nitrogen as free ammonia #cb4j #cb4j #j #cb4j #cb4j #j ,nitrogen as nitrites ,nitrogen as nitrates 4#abj 4#bdj #j4bdj #j4fj ,chlorine as chlorides #acd #acf #acf #aai ---------------------------------------- ------------------------------------ ,another example of the use of chemical precipitation is at ,alliance1 ,ohio4 ,there are three tanks each with a capacity of #addjjj gallons4 ,the amount of sewage flowing into the tanks during the year #ahig averaged about #cjj1jjj gallons per day4 ,during the year #ahig each day #ahj pounds of chemicals were added to the sewage and #fej pounds of sludge was precipitated and pressed daily4 ,the total cost of the disposal plant was #bjgee4jj4 ,the cost of operation and maintenance for the years #ahig and #ahih was #abij4jj and #aefg4dc respectively4 ,the average amount of lime used during this time was #iejjj pounds yearly4 ,two men perform all the labor necessary for the operation of the plant4 ,from the chemical analyses given in the ,engineering ,record ,jan4 #ac1 #aijj of the sewage and effluent1 averages representing five months show the efficiency in albuminoid ammonia to be #dj percent and oxygen required #cj percent4 ,septic ,tank ,we will now discuss a very different process of treating sewage1 the septic method4 ,the septic tank consists of a tank from which generally the air and light are excluded and through which the sewage flows with a slow velocity1 thus allowing the matter in suspension to settle to the bottom or rise to the top by reason of its specific gravity1 there to be further acted upon or decomposed by bacteria4 ,the currents should be so guided that they are distributed over a considerable depth and not allowed to disturb the sediments at the bottom or the material at the top4 ,the darkened ill ventilated and modestly heated conditions in the tank are all conducive to the propagation of a micro-organism known as bacteria4 ,the activity of these organisms causes a chemical decomposition of the organic matter in the sewage a part passing off as gas and a part passing off in the effluent as inorganic matter1 while another portion is deposited in the bottom of the tank as sludge4 ,so far only matter in suspension has been considered but it is also true that chemical action takes place to some extent in the organic matter in solution4 ,this chemical action is a denitrifying action similar to that which takes place in intermittent downward filtration4 ,an important fact in the septic tank effluent is that its compounds have been broken down and it can now be more readily purified4 ,the septic tank process is self-regulating1 self-acting1 requires no attention except the occasional cleaning out of the sludge4 ,as an illustration of this process the septic tank at ,champaign ,illinois may be described4 ,this tank although designed in #ahie1 has only been in operation since #ahig4 ,the dimensions of this tank are #cg by #af by #e feet and it has a cubic capacity of #bb1jjj gallons4 ,it has taken care of a dry weather flow of #cjj1jjj gallons per day1 about #ac times its cubic contents4 ,the tank has operated with a range of from #aa to #bg times its cubic capacity with a high efficiency of purification though much of this was ground water4 ,the reduction of the organic matter in suspension1 as shown by the reduction of oxygen consumed1 nitrogen as albuminoid ammonia1 and total organic nitrogen in three analyses averaged #id percent4 ,however it is not considered that an average of more than #hj to #ij percent may generally be expected4 ,the reduction of organic matter in solution is considerable1 averaging #ag percent4 ,this sludge at the bottom is a black muddy looking silt-like deposit containing about #fj percent of water and #e percent of organic matter4 ,its value as a fertilizer is small4 ,although the amount of sludge is relatively small the accumulation requires removal occasionally1 three or four times a year4 ,it is estimated that for every #a1jjj1jjj gallons sewage there is about #c cubic feet of dry matter4 ,by chemical precipitation this would amount to from #bj to #be cubic feet per #a1jjj1jjj gallons4 ,another good example of the septic tank method is the one in use at ,exeter1 ,england4 ,this plant has been in operation since #ahif4 ,it was designed for #ihjjj gallons capacity4 ,the sewage is allowed to remain in the tank nearly #bd hours4 ,the tank is used in conjunction with five beds in which further purification is used4 ,the beds are filled with coke breeze and one is always resting for a week at a time4 ,the tank is made nearly air tight by an arched roof and any gasses collecting may be burned at a vent4 ,the rate of working this tank is much slower than the process at ,champaign ,illinois4 ,at ,southwold ,england1 there is another good illustration of this method4 ,this has been called an open septic tank and is used in conjunction with two beds1 an anaerobic1 and an aerobic bed1 the latter containing polarite4 ,this plant is interesting from the fact that the effluent from the anaerobic bed is distributed over the aerobic bed by means of a revolving sprinkler which prevents the liquid from passing unequally through the large grain1 porous material4 ,the action upon these beds is continuous4 ,from a report of this system the analysis of gas found in three samples are as follows3-- ---------------------------------------- ----------------------------- ,carbon ,sulphuretted ,oxygen ,nitrogen dioxide hydrogen ---------------------------------------- ------------------------- ,septic tank #j4be #bh4df #gj4jc #a4bf ,anaerobic bed #g4bf #ci4aj #eb4cg #j4ia ,aerobic bed #bj4fb #gh4fc #j4ge #j4jj ---------------------------------------- ----------------------------- ,contact ,bed ,the contact bed as distinguished from the bacteria bed may be said to be made up of fine material1 while the bacteria beds are built of coarse material4 ,the latter are used for taking out the rougher solids1 and the former for taking out the more finely divided material1 and the organic matter in solution4 ,while this distinction is not commonly made it seems to be growing into usage4 ,in the process of purification by means of contact beds the sewage is applied intermittently by distributing pipes or troughs so as to slowly fill the beds which are filled from a depth of from three to six feet with any kind of hard1 porous1 jagged material4 ,the change which takes place is due to the action of certain bacteria in the presence of air4 ,although this process is not a new one1 the method by which the results were obtained was not fully understood until the more recent discoveries in the science of bacteriology were made4 ,the beds are made water tight to a depth of about four feet1 the bottom being channeled or tiled to drain the effluent either to a secondary bed or into the effluent channel4 ,many eminent men have advocated special material as coal1 coke1 clinker slag1 sand1 and gravel1 and even glass for filling material4 ,the results do not differ materially and ,prof4 ,l4 ,p4 ,kennicutt in an article in the ,journal of the ,association of ,engineering ,societies1 ,february #aijj makes the following statement1 8,the material should be more or less porous so as to have a larger water absorbing area and have a jagged surface on which the gelatinized micro-organisms can be easily retained40 8,the quantity of sewage that can be successfully treated by intermittent filtration has been shown not to be over #ajj1jjj gallons per acre per day1 a quantity so small as to be quite useless for towns and cities which would be obliged to construct beds with sand not 8in situ04 ,this point was quickly perceived in ,england where sand 8in situ0 is not of common occurrence4 ,these bacteria beds were not used long before the problem arose3 ,can the amount of land required by the intermittent filtration method be so reduced that the construction of artificial bacteria beds will be a practical possibility8 8,the results of the investigation started by this problem have given us what is known as the contact system of treatment and the septic tank treatment and have apparently shown not only that by combining these two methods the amount of area required for #ajj1jjj gallons can be reduced from one acre to about one seventh of an acre but also that the bacterial treatment is possible with sewage containing manufacturing refuse1 and have outlined how sewage containing storm water may be treated40 ,it has been found by experiment that after two or three weeks there is a marked reduction in the initial capacity of the tank due to breaking down of the filling material and also to the filling material becoming charged and coated over with a gelatinous slime consisting of living organisms and organic matter in the process of transformation4 ,if the bed is not overworked the capacity of the tank will remain constant after the first two or three weeks1 showing that the durability is unlimited4 ,the beds are usually filled in half an hour1 and the sewage allowed to remain on them about two hours when the effluent is run off and the beds allowed to rest several hours before again being filled4 ,by contact beds in series1 the number depending upon the kind of sewage1 almost any degree of purification can be obtained4 ,the ,engineering ,record of ,jan4 #bg1 #aijj gives a very interesting account of the sewage disposal works at ,sutton1 ,england4 ,the works were constructed in #ahia-ic1 and comprise an area of #bh acres1 #ah acres only being capable of irrigation4 ,they were originally designed for chemical precipitation and broad irrigation1 but after giving these methods a two years' trial the local board found itself unable to satisfy the requirements of the conservators of the ,river ,thames1 into which the effluent flowed4 ,mr4 ,w4 ,j4 ,dibdin advised the construction of filters or fine grained bacteria beds4 ,two beds having a combined area of a quarter of an acre and a capacity of #bjj1jjj gallons1 were built in #ahie-if for the purification of the chemically treated sewage4 ,in #ahif the first bacteria bed was constructed for the treatment of crude sewage4 ,as previously stated1 many tests were made to determine the best kind of material for filling the beds4 ,the crude sewage1 after being screened to intercept floating matter1 is run directly onto the filters without the addition of any chemicals4 ,after remaining in the beds for a period of two hours the effluent is in a fit condition to be discharged into the brook leading to the ,thames and is uniformly superior to the effluent obtainable by local land treatment4 ,all experiments with bacteria beds show that the objects for which they were intended1 to abolish sludge1 has been realized and that sewage can be purified without chemicals at a small cost1 being but little more than that incurred by the labor in attending to1 or supervising the filling and discharging1 the filters1 and that sewage purification can be carried on with little or no nuisance4 ,discussion ,the amount of purification to be obtained by dilution depends upon the size of the stream into which the sewage is discharged and also upon the amount of oxygen contained in the stream4 ,the latter condition is controlled very largely by the rate of flow of the stream and its previous condition of pollution4 ,mr4 ,e4 ,p4 ,stearns in his report to the ,massachusetts ,state ,board of ,health1 #ahij1 on ,pollution and ,self-,purification of ,streams1 gave a table showing the calculated amount of free ammonia1 dissolved solids and chlorine which sewage adds to running streams4 ,much interest is being taken in the effect of the discharge of the sewage of ,chicago1 and the waters of ,lake ,michigan1 into the ,illinois ,river1 and the outcomes of the analyses of samples taken along the river is awaited with interest4 ,published reports have not been given out1 but information from the most reliable sources seem to show that a considerable purification takes place in the passage down the river4 ,no reliable data could be obtained giving the percent of purification by irrigation4 ,at ,berlin the sewage is purified by this method1 and the effluent comes well within the requirements of the ,german law4 ,with chemical treatment about #ij percent of the matter in suspension and a small percent of that in solution is removed1 and the purification is about #ec percent of the total organic matter4 ,the best examples of intermittent downward filtration show an efficiency of #ie percent on the total organic matter4 ,however1 if this process is used in connection with other methods the organic matter may be reduced #ii percent and the chemical analyses of the effluent may fill the drinking water requirements4 ,results of analyses of sewage and effluent from septic tanks show an efficiency of from #he to #ij percent in the organic matter in suspension4 ,very little change takes place in the matter in solution4 ,the result of experiments with a single contact bed at ,sutton1 ,england1 from ,november #ahif to ,march #ahih shows a purification of #fd percent2 if1 however1 two beds are used in series1 a further purification of #ej percent is obtained or a total purification of #hb percent of the crude sewage4 ,the capacities of irrigation1 and intermittent downward filtration plants1 and contact beds are usually stated in terms of the number of gallons per acre per day4 ,,table ,,iii4 ,,rate ,,of ,,sewage ,,treatment4 ,system4 ,location4 ,sewage treated in gallons per acre per day4 ---------------------------------------- ------------------------------- ,,irrigation4 ,berlin1 ,germany4 #ah1jjj4 ,manchester1 ,eng4--,estimated but not constructed4 #ah1ejj4 ,,intermittent ,,downward ,,filtration4 ,framingham1 ,mass4 #ai1jjj4 ,leicester1 ,mass4 #ch1gej4 ,brockton1 ,mass4 #dd1jjj4 ,marlborough1 ,mass4 #ed1jjj4 ,gardner1 ,mass4 #adj1jjj4 ,mendota1 ,ills4 #ahd1jjj4 ,worcester1#a ,mass4 #cbb1jjj4 ,worcester1#a ,mass4 7,fletcher's estimate74 #ejj1jjj4 ,madison1#a ,wis4 #h1jjj1jjj4 ,,contact ,,beds4 ,manchester1 ,eng4 7crude sewage7 #ejj1jjj4 ,manchester1#a ,eng4 #gjj1jjj4 ,manchester1 ,eng4 7storm water sewage7 #b1ejj1jjj4 ,footnote #a3 ,secondary filtration4 ,table ,,iii shows the capacity of representative plants4 ,best authorities consider #ajj1jjj gallons per acre per day to be the maximum rate permissible under the best conditions for the treatment of crude sewage by the intermittent downward filtration system4 ,with unfavorable conditions the quantity of sewage should be limited to as low as #bj1jjj gallons4 ,wherever too large a dose is applied to the bed the sewage is not properly purified and the beds soon become clogged up and unfit for further use4 ,when the beds are used for secondary purification1 #gej1jjj gallons may be treated per acre per day4 ,the results of extensive experiments made at ,manchester1 ,england in #ahih and #ahii show that by means of contact beds crude sewage may be treated at the rate of #ejj1jjj gallons per acre per day4 ,when the beds are used for secondary purification1 #gej1jjj gallons may be successfully treated1 and storm water sewage treated at the rate of #b1ejj1jjj gallons per acre per day4 ,the capacity of the chemical precipitation plant at ,madison1 ,wisconsin is #fh percent of the daily flow1 which in #ahii was estimated at #cjj1jjj4 ,the company that built the plant agreed that the plant should have a daily capacity of #a1bjj1jjj for each and every day in the year4 ,this shows the estimated capacity of the tank to be #bh percent4 ,at ,worcester1 one of the best examples of this process is in operation4 ,the size of the tanks is equal to #bh percent of the total flow of #ag4a million gallons per day of which #aj4a million gallons is the out flow from a comparatively clear pond4 ,if the actual amount of sewage is considered the tanks have a capacity of #fe percent of the total flow4 ,rafter and ,baker in their discussion of the size of tanks recommends that the total capacity should be nearly #ej percent of the average daily flow4 ,the two typical types of septic tanks are those at ,exeter1 ,england and at ,champaign ,illinois4 ,the first has a cubic capacity of #ic percent of the total daily flow1 while the second has a capacity of #g4e percent of the daily flow4 ,when the capacity of the tank is as small as at ,champaign the bacteria do not have time to act upon the sewage as they would if the flow was not so rapid4 ,it is conceded now by the highest authorities on this subject that the tank should have a capacity equal to from one fourth to one half of the average daily flow4 ,concerning the conditions for which the various processes are applicable1 it may be said that the dilution process is used when advantage may be taken of natural resources4 ,this method can be utilized by most cities situated along rivers or streams large enough to sufficiently dilute and carry away the sewage1 and fulfill sanitary requirements4 ,as an example of the use of dilution the ,chicago ,river may be cited4 ,there the uncertain flow of the river was made to pass inward toward the ,illinois ,river with a speed of #b miles per hour and a discharge of #bj1jjj gallons per minute per #ajj1jjj inhabitants4 ,the ,blackstone ,river was used by the cities of ,massachusetts until the pollution of the river became unbearable and the state was compelled to pass a law forcing the cities to purify their sewage4 ,broad irrigation is a method which cannot generally be used on account of the large amount of land and labor required4 ,this method is especially applicable to asylums1 alms houses1 and reformatories where cost of labor is small4 ,it is used in the ,west where the value of all available water leads to the application of sewage to crops1 and also on account of the low stage of western streams during the summer which renders sewage discharged into them an unbearable nuisance4 ,intermittent downward filtration may be used where there is a considerable area of sandy soil1 and also where a high degree of purification is necessary4 ,chemical precipitation does not require a large area for its operation and used alone does not give a high degree of purification4 ,where land and material for beds is expensive1 and partial purification is sufficient1 this system may be used4 ,the septic tank requires a small area4 ,the odors are not offensive and cannot be noticed #ajj feet away4 ,the effluent may be discharged into small streams and soon loses its identity4 ,contact beds are used where a high degree of purity is required2 if the effluent is emptied into rivers or sources of water supply4 ,the beds do not require a large area and the process may be recommended if suitable material is at hand4 ,the cost of construction and maintenance of the different systems vary so largely according to local conditions that a fair estimate is not possible4 ,as the most striking example of maximum and minimum cost the disposal system at ,chicago and at ,lowell1 ,massachusetts may be cited4 ,the purification in both cases is by dilution1 the cost being practically nothing at ,lowell while the ,chicago ,drainage ,canal cost #cc1jjj1jjj4 ,it may not be fair to charge this entire cost to the sewerage system2 nevertheless up to date it has been used for no other purpose4 ,at ,berlin1 ,germany where broad irrigation is used1 the sewage has to be pumped to the farms and involves a considerable cost4 ,aside from this the receipts derived from the sale of farm products are enough to pay the running expenses of the farm4 ,the first cost of the intermittent downward filtration plant is estimated by the writers at #ij1jjj per million gallons per day of sewage treated1 where the beds are artificial4 ,where natural beds can be used the first cost may be reduced to #g1ejj per million gallons per day4 ,the cost of maintenance is about #b4jj per #a1jjj1jjj gallons4 ,the average cost for operating a chemical disposal plant is about #eh cents per inhabitant per year1 or #af4jj per #a1jjj1jjj gallons treated4 ,at ,manchester ,england where broad irrigation and chemical precipitation are used in combination1 the average cost was #fc4jj per #a1jjj1jjj gallons treated4 ,a septic tank for treating #a1jjj1jjj gallons of sewage per day will cost less than #aj1jjj and the cost of maintenance will be about #a4jj per #a1jjj1jjj gallons treated4 ,conclusion ,in selecting a method of sewage disposal1 the conditions1 surroundings1 and requirements of the city should be carefully studied and analyzed1 and judgment and discretion must be used4 ,a matter of so much importance to the community should be placed in the hands of men qualified to make a proper solution of the problem4 ,while in general several methods of purification may be applied to the requirements of the city1 usually local conditions and considerations will narrow the choice to two plans or possibly to a single method4 ,the governing features of the dilution process are so distinct that it is not usually difficult to determine where this method is applicable1 and likewise1 the broad irrigation process has peculiar conditions4 ,in both1 the plans involve only matters of construction4 ,the other methods have more in common and the determination of their relative value is not so easy4 ,as before stated1 the recently developed biolytic processes promise to displace chemical precipitation4 ,where a suitable deposit of sand or gravel is conveniently located on cheap land which may be made without great expense into filtration areas and the sewage discharged upon them by gravity1 intermittent downward filtration may be the most satisfactory1 especially if a highly purified effluent is desired4 ,the item of expense of attendance1 and labor of maintenance must be considered in connection with the cost of this method4 ,in the absence of such favorable conditions and especially where complete purification is not required the septic tank may be the most suitable4 ,for higher purification the combination of the septic tank with filter beds1 or contact beds run at comparatively high rates1 makes a satisfactory purification and is applicable to a wide range of conditions4 ,a bacteria bed may be substituted for the septic tank for the roughing process but its applicability in not so general4 ,in conclusion it may be said that if the next ten years gives as much development in sewage purification as has the last decade1 some of the processes herein outlined will have been discarded and sanitary engineering will have achieved still greater triumphs4 ---------------------------------------- -------------------------------- ,,transcriber',s ,,notes #a4 ,table of ,contents added by transcriber4 #b4 ,all text after the ,contents was handwritten4 #c4 ,silently corrected typographical errors and variations in spelling4 #d4 ,retained anachronistic1 non-standard1 and uncertain spellings as printed4 #e4 ,footnotes have been re-indexed using numbers4 #f4 ,enclosed underlined text in underscores4