TITLE: JAR TEST1.0 INTRODUCTION Coagulation/flocculation is the process of binding small particles in the water together into larger, heavier clumps which settle out relatively quickly. The larger particles are known as floc. Properly formed floc will settle out of water quickly in the sedimentation basin, removing the majority of the waters turbidity. !n many plants, changing water characteristics require the operator to adjust coagulant dosages at intervals to achieve optimal coagulation. "ifferent dosages of coagulants are tested using a jar test, which mimics the conditions found in the treatment plant. The first step of the jar test involves adding coagulant to the source water and mi#ing the water rapidly $as it would be mi#ed in the flash mi# chamber% to completely dissolve the coagulant in the water. Then the water is mi#ed more slowly for a longer time period, mimicking the flocculation basin conditions and allowing the forming floc particles to cluster together. &inally, the mi#er is stopped and the floc is allowed to settle out, as it would in the sedimentation basin. The type of source water will have a large impact on how often jar tests are performed. Plants which treat groundwater may have very little turbidity to remove are unlikely to be affected by weather'related changes in water conditions. (s a result, groundwater plants may perform jar tests seldom, if at all, although they can have problems with removing the more difficult small suspended particles typically found in groundwater. )urface water plants, in contrast, tend to treat water with a high turbidity which is susceptible to sudden changes in water quality. *perators at these plants will perform jar tests frequently, especially after rains, to adjust the coagulant dosage and deal with the changing source water turbidity. + 2.0 OBJECTIVE: +. To conduct jar test. ,. To show the effectiveness of chemical treatment in a water treatment facility. -. To evaluate coagulation efficiency. .. To determine the most effective dosage of the recommended coagulants and flocculants. /. To selects the best chemical or best dosage to feed on the basis of clarifies of effluent and minimum cost of chemicals. 0. To gain a 1hands on1 understanding of the treatment process for removing suspended solids from water. 3.0 THEORY: 2aw water or wastewater must be treated to remove turbidity, color and bacteria. Colloidal particles are in the si3e range between dissolved substance and suspended particles. The particles are too small to be removed by sedimentation or by normal filtration processes. Colloidal particles e#hibit the Tyndall effect4 that is, when light passes through liquid containing colloidal particles, the light is reflected by the particles. The degree to which colloidal suspension reflects light at 567 angle to the entrance beam is measured by turbidity. The unit of measure is a Turbidity 8nit $T8% or 9ephlometric Turbidity 8nit $9T8%. !t is determined by reference to a chemical mi#ture that produces a reproducible refraction of light. Turbidities in e#cess of / T8 are easily detectable in a glass of water and are usually objectionable for aesthetic reasons. &or a given particle si3e, the higher the turbidity, the higher the concentration of colloidal particles. Color is a useful term that is used to describe a solution state. :ut it is difficult to distinguish ;dissolved color1 and ;colloidal color1. )ome color is caused by colloidal iron or manganese comple#es. (lthough, the most common cause of color is from comple# organic compounds that originate from the decomposition of organic matter. <ost color seems to be between -./ and +6=m, which is colloidal. Color is measured by the ability of , the solution to absorb light. Color particles can be removed by the methods discussed for dissolved or colloidal, depending upon the state of the color. &inely dispersed solid $colloids% suspended in wastewater are stabili3ed by negative electric charges on their surfaces, causing them to repel each other. )ince this prevents these charged particles from colliding to form larger masses, called flocs, they do not settle. To assists in the removal of colloidal particles form suspension, chemical coagulations and flocculation are required. These processes, usually done in sequence, are a combination of physical and chemical procedures. Chemicals are mi#ed with wastewater to promote the aggregation of the suspended solids into particles large enough to settle or be removed. Coagulation is the destabili3ation of colloids by neutrali3ing the forces that keep them apart. Cationic coagulants provide positive electric charges to reduce the negative charge of the colloids. (s a result, the particles collide to form larger particles $floc%. 2apid mi#ing is required to disperse the coagulant throughout the liquid. The coagulants overdose can cause a complete charge reversal and destabili3e the colloid comple#. ( coagulant is the substance $chemical% that is added to the water to accomplish coagulation. There are three key properties of a coagulant4 +. Trivalent cation> (s indicated in the last section, the colloids most commonly found in natural waters are negatively charged4 hence a cation is required to neutrali3e the charge. ( trivalent cation is the most efficient cation. ,. 9onto#ic> This requirement is obvious for the production of safe water. -. !nsoluble in the neutral p? range. The coagulant that is added must precipitate out of solution so that high concentrations of the ion are not left in the water. )uch precipitation greatly assists the colloid removal process. The two most commonly used coagulants are aluminum $(l -@ % and ferric iron $&e -@ %. :oth meet above three requirements. (luminum can be purchased as either dry or liquid alum A(l,$)*.%-B+.?,*C. Commercial alum has an average molecular weight of /5.. Dhen alum added to a water containing alkalinity, the following reaction occurs4 - (l,$)*.%-B+.?,* @ 0?C* ' - E ,(l$*?%-$s% @ 0C*, @ +.?,* @ -)*. ,' The above reaction shifts the carbonate equilibrium and decreases the p?. Dhen sufficient alkalinity is not present to neutrali3e the sulfuric acid production, the p? may be greatly reduced4 (l,$)*.%-B+.?,* E ,(l$*?%-$s% @ -?,)*. @ F?,* !f the second reaction occurs, lime or sodium carbonate may be added to neutrali3e the acid. The optimal p? range for alum is appro#imately /./ to 0./ with coagulation possible between p? /to p? F under some conditions. !n flocculation process, the flocculating agent is added by slow and gentle mi#ing to allow for contact between the small flocs and to agglomerate them into larger particles. The newly formed agglomerated particles are quite fragile and can be broken apart by shear forces during mi#ing. !ncreasing the dosage will increase the tendency of the floc to float and not settle. *nce suspended particles are flocculated into larger particles, they can usually be removed from the liquid by sedimentation, provided that a sufficient density difference e#ists between the suspended matter and liquid. Dhen a filtering process is used, the addition of a flocculants may not be required since the particles formed by the coagulation reaction may be of sufficient si3e to allow removal. The flocculation reaction not only increases the si3e of the floc particles to settle them faster, but also affects the physicals nature of the floc, making these particles less gelatinous and thereby easier to dewater. . 4.0 EQUIPMENT AND MATERIAL +. Gar test apparatus with si# rotating paddles ,. )i# $0% beaker -. Thermometer / .. Time / )topwatch /. p? meter 0. Turbidity meter H. pipette 0 5.0 REAGENT +. Coagulant e.g. aluminum sulfate $alum%, polyaluminum chloride $P(C%, ferrous sulfate, ferric chloride, etc. ,. Coagulant aid e.g. p? adjusters $lime or sulfuric acid%, activated silica, polyelectrlye $e.g. synthetic polymer such as acrylamide%, clays $e.g. bentonite, montmorillonite, etc.% -. Iiquid sample 6.0 PROCEDURES +. The waste water from the treatment plant was prepared. The sodium was use to stability the P? of the waste water to the neutral. ,. The temperature, p?, color, alkalinity and turbidity of the synthetic water sample were measured. -. 066ml was filled each of the prepared synthetic water suspension into si# different beakers $Ple#iglas beakers% .. The prescribed dose of coagulant was added to each jar by using a pipette. *ne jar has no coagulant since a control sample was required. /. !f a coagulant aid is required, it is added to each jar $e#cept for control sample% during the last +/ seconds of the rapid mi# stage. 0. )tart stirring rapidly $06 to F6 rpm% for - minute $2apid mi# stage%. H. (fter the rapid mi# stage, reduce the speed to -6 rpm for ,6 minutes. F. &loc formation were record ed by referring to the chart of particle si3es in final +6 minutes. 5. (fter the stirring period was over, stop the stirrer and the flocs was allowed to settle for about / minutes as in scheme $iv% +6. /66mI of settle water was separate out into another beaker. ++. The temperature, p?, color, alkalinity and turbidity of the clarified water were determined. +,. ( graph of turbidity versus coagulant dose $mg/I% was plotted. The most effective dose of coagulant $or with the present of coagulant aid% that gives the least turbid H results also determined. +-. The qualitative characteristics of floc as bad, moderate, good and very good were recorded. Cloudy samples indicate bad coagulation while good coagulation refers to rapid floc formation resulting in clear water formation on the upper portion of the beaker. +.. The following graph> color versus coagulant dose, p? versus coagulant dose, temperature versus coagulant dose, etc. were plotted. These graphs will assist students in the interpretation of the coagulation'flocculation process. F .0 RESULT AND DATA ANALYSIS G(2 9*. + , - . / 0 !nitial p? 0.., 0.., 0.., 0.., 0.., 0.., !nitial Temperature $ o C% ,0./ ,0./ ,0./ ,0./ ,0./ ,0./ Coagulant dose $mg/I% +6 ,6 -6 .6 /6 control (gigate $minutes% ,- ,- ,- ,- ,- ,- &ast $rpm% H6 H6 H6 H6 H6 H6 )low $rpm% -6 -6 -6 -6 -6 -6 )ettling "epth $mm% +6 F . - , , &inal p? /.-/ ..60 -.06 -.,/ -.,, ' &inal Temperature $ o C% ,-.+ ,-.+ ,,.5 ,,.5 ,,.5 ' &inal Turbidity $9T8% H / . +H -, +6F &loc &ormation fine Jery fine moderate Coarse Jery coarse <oderately fine Time of floc formation K / minutes &loc si3es for> Jery fine is 6.-6mm to 6.H/mm &ine is 6./6mm to 6.H/mm <oderate fine is +.66mm to +./6mm. &rom the graphs we could conclude4 The most effective coagulant dose is +6 mg/I, and ,6 mg/I The most effective p? is /.-/ The e#pected temperature was ,,.56 at optimum coagulant dose. !.0 DISCUSSION De had successfully done this e#periment because the objective of this e#periment, to conduct various e#periments on chemical coagulation and flocculation and 5 to determine the optimum dose combination of coagulant aid $when used% which will produce the highest removal of turbid water sample has achieved. Gar tests have been used to evaluate the effectiveness of various coagulants and flocculants under a variety of operating conditions for water treatment. . This procedure allows individual polymers to be compared on such criteria as floc formation, settling characteristics, and clarity. Lenerally, the best performing products provide fast floc formation, rapid settling rate, and clear supernatant. This test should be performed on' site, since large amounts of water may be required for testing. Turbidity is essentially a measure of the cloudiness of the water which indicates the presence of colloidal particles. The particles should be making sure removed from the water before for the publics use. ?owever these colloids are suspended in solution and can be removed by sedimentation or filtration. Jery simply, the particles in the colloid range are too small to settle in a reasonable time period, and too small to be trapped in the pores of a filter. &or colloids to remain stable they must remain small. <ost colloids are stable because they posses a negative charge that repel other colloidal particles before they collide with one another. The colloids are continually involved in :rownian movement, which is merely random movement. Charges on colloids are measured by placing "c electrodes in a colloidal dispersion. The particles migrate to the pole of opposite charge at a rate proportional to the potential gradient. Lenerally, the larger the surface charge, the more stable the suspension. :ased on this e#periment, the first jar is serving as a control and no coagulant was added. The coagulant doses increased in the containers from no +to no 0. &or this water, as the dose of coagulant increased the residual turbidity improved. !t is important to note that the optimum coagulant dose is the dose which meets the specified turbidity required on the regulatory permit. The addition of e#cess coagulant may reduce turbidity beyond what is required but also could lead to the production of more sludge which would require disposal. +6 The most effective dose of coagulant we get from the Lraph turbidity versus coagulant after the e#periment is ,6 mg/I. The most effective p? is /.-0. Gar tests are used in these procedures to provide information on the most effective flocculants, optimum dosage, optimum feed concentration, effects of dosage on removal efficiencies, effects of concentration of influent suspension on removal efficiencies, effects of mi#ing conditions, and effects of settling time. The general approach used in these procedures is as follows> a% Prepare stock suspension of sediment. b% Test a small number $si#% of polymers that have performed well on similar dredged material which has ,'grams'per'litre suspensions and is a typical concentration for effluent from a well'designed containment area for freshwater sediments containing clays. !f good removals are obtained at low dosages $+6 milligrams per liter or less%, then select the most cost'effective polymer. !f good removals are not obtained, e#amine the polymer under improved mi#ing and settling conditions and test the performance of other flocculants c% The effects of settling time on the removal of suspended solids and turbidity from a suspension of average concentration should be e#animate using the selected dosage and likely mi#ing conditions. d% The effects of the range of possible mi#ing conditions on the required dosage of flocculants for a typical suspension should be e#animate. ".0 CONCLUSION (s conclusion, this e#periment is successfully been done and it is because the objective of this e#periment which to conduct various e#periments on chemical ++ coagulation and flocculation and to determine the optimum dose combination of coagulant aid $when used% which will produce the highest removal of turbid water sample has achieved. Gar testing is an e#perimental method where optimal conditions are determined empirically rather than theoretically. Gar test are meant to mimic the conditions and processes that take place in the clarification portion of water and wastewater treatment plants. The values that are obtained through the e#periment are correlated and adjusted in order to account for the actual treatment system. (fter the e#periment, Lraph turbidity versus coagulant dose are plot, from the graph we get the most effective dose of coagulant is 06mg/I :ase on the data, we conclude that although the turbidity is generally declines as the amount of the alum which added into the water but there is a point where more alum should not be added. This is because alum will make the water more acidic. Therefore, to overcome these problems, buffer should be added with same amount of alum at the same time the alum is added. (fter this e#periment, we reali3e that a successful Gar Test is very reliant upon the proper preparation of the polymers being tested. "ilution technique $Mmake downM% is especially critical, since it involves compactly coiled large molecules in emulsions, prior to activation. The polymer must be uncoiled to provide ma#imum contact with the colloidal particles to be flocculated. !f the following procedures are not followed, the Gar Test results will be very unreliable. (s conclusion, after we analy3ed the data, we have decided that the optimum dosage of alum for this e#periment is 10 #$%L. we reach this conclusion base on the fact that the turbidity minimum at NTU. 10.0 QUESTIONS Two sets of e#perimental data obtained from a jar test on water samples with initial turbidity of +/9T8 and ?C*- alkalinity of /6mg/I CaC*- +, Gar 9o + , - . / 0 Ph /.6 /./ 0.6 0./ H.6 H./ Coagulant dose $mg/I% +6 +6 +6 +6 +6 +6 Turbidity $9T8% ++ H /./ /.H F +- JAR TEST 1 Gar 9o + , - . / 0 p? 0.6 0.6 0.6 0.6 0.6 0.6 Coagulant dose $mg/I% / H +6 +, +/ ,6 Turbidity $9T8% +. 5./ / ../ 0 +- JAR TEST 2 +6.+ Plot a graph of turbidity versus p? and turbidity versus coagulant dose $mg/I%. +6., )tate the optimum p? value and optimum alum dose of the coagulation process of the raw water. The optimum p? was chosen as 0.,/ and the optimal alum dose was about +,./mg/I $based on graph H.+% +6.- Dhat is the usage of Gag testN The purpose of Gar Testing is to predetermine the amount of chemicals requird to treat and precipitate as sludge the contaminants in a given volume of wastewater. The phrase MGar TestingM is commonly used in the waste treatment industry. !t is used in reference to a method that will determine treatability of a solution or establish a sequence of steps required to achieve treatability. Gar Testing is used as a tool to determine why proper treatment is not being achieved. +- +6.. ?ow to reduce dosage of alum in treatment plantN )ince the two important factors in coagulant addition are p? and dose. Therefore to reduce the dosage of alum we can add coagulant aids such as p? adjusters $lime or sulfuric acid%, activated silica, clay $bentonite montmorilionite%and polymers . The addition of activated silica and clays is especially useful for treating highly colored, low turbidity waters as it add weight to the floc . +6./ 9ame and e#plain briefly three types of alkalis that are suitable for p? control. Iime Ca$*?%, ,soda ash $9(,C*-%, )odium :icarbonate, )odium ?ydro#ide <agnesium ?ydro#ide, Calcium :icarbonate and others .The alum reacts rapidly with compounds in the water that contain carbonates, bicarbonates and hydro#ides to produce a jelly'like substance that absorbs impurities. (t the same time, alum, with a positive charge, neutrali3es the negative charge common to natural particles, which draws them together. )mall particles microfloc are formed. The following equation shows the reaction of alum with alkalinity> A&2'SO4(3 . 14H2O )3C*'HCO3(2 2A&'OH(3 ) 3C*SO4 ) 6CO2 )14H2O A&+#,-+# S+&.*/0 C*&1,+# B,1*234-*/0 A&+#,-+# H56247,60 C*&1,+# S+&.*/0 C*234- D,47,60 8*/02 +6.0 Dhat are the advantages of using coagulant aidsN To accelerate settling, minimum the usage of chemical in treatment and adjustd the p? of the water into the optimal range for coagulation. +6.H Dhat are the effects of alum dosage in treatment criteriaN (lum will have the effect of lowering p? so careful monitoring is necessary when applying alum. (lum contains aluminum, which is to#ic to fish in acid water, therefore overdose of alum can give negative effect to the environment. (lum use results in sludge of precipitated particles that should either be vacuumed out or removed via a bottom drain . +. +6.F 9ame five differences between alum and ferric coagulants. a. Ph' The optimum p? range for alum is generally about / to F. The optimum p? range for ferric chloride is . to +,. b. "osage ' &erric dosage is typically about half of the dosage required for alum. c. Chemical 2eaction' &erric coagulant reacts in water with hydro#ide alkalinity to form various hydrolysis products that incorporate &e$*?%-. These compounds possess high cationic charge which allows them to neutrali3e the electrostatic charges found on colloidal compounds and also to bind to negatively charged particles, including the ferric hydro#ide itself. This ability to bind to itself is the mechanism for the formation of floc aggregates and the basis for ferric chloride1s flocculation abilities. &eC!- @ - ?C*- K &e $*?% - @ -C*, @ -C! ' !n the case of alum coagulants, these reactions can be represented as follows> (l,$)*.%- @ - Ca$?C*-%, K , (l$*?%- @ - Ca)*. @ 0 C*, (l,$)*.%- @ - Ca$*?%, K , (l$*?%- @ - Ca)*. (l,$)*.%- @ - 9a,C*- @ - ?,* K , (l$*?%- @ - 9a,)*. @ - C*, The alum reacts rapidly with compounds in the water that contain carbonates, bicarbonates and hydro#ides to produce a jelly'like substance that absorbs impurities. (t the same time, alum, with a positive charge, neutrali3es the negative charge common to natural particles, which draws them together. )mall particles microfloc are formed. d. &erric coagulant can be purchased either in sulfate salt $&e , $)* . % - .#? , *% or chloride salt $&eCl - .#? , *% where as alum only in sulfate salt (l , $)* . % -. e. Iiquid alum is sold appro#imately .F.F percent alum $F.-O(l , * - % and /+., percent water.if it is sold as a more concentrated solution, there can be probles with +/ crystalli3ation of the alum during shipment and strorage. Dhile ferric coagulant is available in various dry and liquid forms. 11.0 APPENDI9 AND RE:ERENCE +0 +H +F R0.020-10;: L. G. )chroepfer, <. I. 2obins, and 2. ?. )usag, $+50.%P2esearch Program on the <ississippi 2iver in the Jicinty of <inneapolis and )t. Paul,Q (dvances in Dater Pollution 2esearch, vol. + I."avis , !.Cornwell. !ntroduction to Rnvironmental Rngineering. Third Rdition. Iab sheet> Rnviromental Rngineering, Test> G(2 Test Debsite> . th &eb ,660 $date retrieved% http>//www.waterspecialists.bi3/html http>//www.phippsbird.com/ http>//home.alltel.net/mikeric/Pretreat<aint/ ?ammer, <arkG. $,66+%QDater and Daste water Technology &routh RditionQ 9ew Ter3ey> Prentice ?all <aster, Lelbert < $+55F% P!ntroduction to Rnvironmental Rngineering and )cienceQ :lack, G.L. $+550%. Microbiology. Principles and Applications. Third Rdition. Prentice ?all. 8pper )addle 2iver, 9ew Gersey. +5 Tortora, L.G., &unke, :.2., Case, C.I. $+55/%. Microbiology. An Introduction. &ifth Rdition. The :enjamin/Cummings Publishing, Co., !nc., 2edwood City, C(. ?. (. Thomas,$+55F% PLraphical "etermination of :. *. ". 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