.J 5‘] O :n ‘ c.) :21 :1: % {5 a F) L" l" I Ll! M. i | $ . r 1 W‘il'liil" ‘. ‘ | WIM‘WW _{ I MW! ,w m; N_.\ (DOD-A THE CONSTRUCTION OF A MODEL FILTER PLANT THESIS FOR DEGREE OF B. S. GEORGE HONEYWELL |926 9. THESIS The PonstructiOfi of q ”odel sfilter Plant. A Thesis Submitted to the Faculuy 0' the fichigah State College of Agricu ture and Applied Science bar J George ”aneywell m Bachelor of Scipfice June 1996. T: {C‘CTV‘ The purpose of this thesis is to give a working model of a modern filter plant. Po attevpt has been made to follow the deeivn of any one filter plant but merely to Five 3 re- presenative "edel wWich will show the different units of a filter plant and new they function. 10.33.71 1'.- The action of a filter plant may be outlined in three major operations. First, the mixine of the coagulant with the raw water. qecond, the settline of the coa~ulant. Third, the filterin" of the water throurh the sand beds. 3 “he mheory of Filtration. In filterine water throush sand, the principal results to be accorplished are the removal of visible suspended hatter causine turbidity and the bacteria. qometimes also the removal of color is an object of im- portance. Within certain limits, a sand filter is a very efficient device to aocorplish these purposes. “he action of a filter is obviously much more than that of a strainer. Iaree particles are of course removes by this action, but the chief function of the filter is to remove bacteria and particles of sediment of ricrosconic and sub- microscopic size, and its ability to do this cannot rest on its strainine action alone. In part, the sand-bed undonbtei- -2- 1y serves as numerous minute sedimentation chambers, which, ownine to their small size and the low velocity of flow, are quite efficient in the removable of the finer suspended par- ticles, includins bacteria. In this way particles much smal- ler than the pore spaces in the sand are reroved to a very considerable extent by purely mechanical means. If, however, Fe th° process was purely mechanical, the filtered water should i be as wood at one time as another, but such is not usually 3 the case. As a matter of fact, a sand filter becomgg. to a 6 certain deares, more efficient after a period of service, L_ showins that core other factor than purely mechanical removal, functions in the process. The explanation of the irproved action of a "ripened" filter is the formation of a certain amount of slihy sediment or coatine around and among thesand grains, especially in the upper layers of the bed. When critically exarined, this material is found to contain inorganic wetter, as silt, of all kinds, organic substances, as bacteria, aleae, diatoms, and material of a colloidal character. This deposit appears to be larsely effective in retainins the minute particles and the colloids contained in the w1ter. It is possible that the true explanation of this action will be found to lie in the electrical properties of colloids. The Use of Coagulants. Various chemicals when added to water will carbine with certain substances ordinarily present, formins precipitates -3- which are were or less trelatinous in character. These act as coaeulants to collect the finely divided suspended matter into relatively laree easses which are thus ruch more readily removed by sedimentation or filtration. Color may also frequently be removed to a large extent by this treatment tut its ereatest use is in connection with the subsidence of turbid waters. fr Several substances can be used as coaeulants. That most commonly employed is sulphate of Aluminu", which,when in- troduced into water containins cartonates and bicarbonates of lime and racnesium, is decorposed, the sulphuric acid forminr L— sulphates with the lime and scenesiuu, while the carbonic acid is set free, and the aluminu” unites with the water to fore a bulky pelatphydroxide. this precipitates out and constitutes the coag.aeent. the chemical reactions are shown by this ferrule: Alg(904)3¥'3CaW2(003)2~”A12(07)5f'3 Ca§04+'6002 The different units of the model are made with class sides so that one may follow the path of the water from the time it enters until it leaves, and observe the action which takes place in each unit. . The six units in order in which they are used are as follows: The clear well and sedimentation chamber. mhe coaeulant feeder. The mixer. The coaeulatine basin. The sand filter, and the storaee reservoir. .4- The clear well allows the coarser particles to settle out and also shows the condition of the water before entering the filter. “he coaeulant feeder is an auto"atic arranverent which keeps a constant arount of Aluminum sulphate emptinr into the water as it enters the mixer. The mixer is a lone narrow channel with buffets arransed f~ to thoroushly mix the coaculant with the water. L After the water leaves the mi