Dugal, Hardev S.

Hatcher, Herbert J.

Joyce, T. W.

Zanella, Eugene F.

Scholarly Materials And Research @ Georgia Tech

THE INSTITUTE OF PAPER CHEMISTRY, APPLETON, WISCONSINIPC TECHNICAL PAPER SERIESNUMBER 95THE EFFECT OF AN ENZYMATIC SLIMECONTROL AGENT MX-1361 ACTIVATEDSLUDGE TREATMENT PLANTSTHOMAS W. JOYCE, EUGENE F. ZANELLA, HARDEV S. DUGALAND HERBERT J. HATCHERMAY, 1980The Effect of an Enzymatic SlimeControl Agent MX-1361 on ActivatedSludge Treatment PlantsThomas W. JoyceEugene F. ZanellaHardev S. DugalEnvironmental Sciences DivisionThe Institute of Paper ChemistryAppleton, Wisconsin 54911Herbert J. HatcherScientistEconomics LaboratorySt. Paul, MinnesotaABSTRACTSlime control in the paper mill is a major operationalproblem and expense facing paper companies. At present,slimes are controlled with synthetic organic chemicals, manyof which contain heavy metals or are highly halogenated andare currently the focus of regulatory scrutiny...An enzyme preparation MX-1361 has been developed to:"control"slimes in pulp and paper mills. The mode of action of the enzymeis ,to cleave carbohydrate bonds in the bacterial slime,, therebydissipating it. There is a concern, however,.that the enzymemight create problems either by deflocculating the bacterialflocs in the waste treatment plant or by exerting toxicity inthe biologically treated effluent..The conclusions of this study were:1. The concentration of BOD and suspended solids inthe treated effluent and the settling properties-of the activated sludge are not affected by theaddition of the enzyme.2. No acute toxicity, as measured with Daphnia, wasfound in the treated effluents.This enzyme preparation appears to have no effect on theoperation or effluent characteristics of activated sludge systems.Apparently, the enzyme has been biologically oxidized because- 2 -tests specific for the enzyme showed no enzyme in the treatedeffluent.INTRODUCTIONRecent concerns over the presence of toxic compounds in theenvironment have been widely publicized. These concerns emanatefrom the knowledge that a few toxic compounds are very recalci-trant to biodegradation and have the potential of bioaccumulationin the environment. The end result of this bioaccumulation hasnot been well documented in most cases, but it is generallybelieved to have an adverse impact on the environment. For thesereasons, there is a growing concern that the currently usedslimicides may not be acceptable to regulatory agencies in thenear future.Operation of most paper mills would be virtually impossiblewithout the use of chemicals to control slime formation. Thevery characteristics which make desirable slimicides, high toxicityand slow biodegradability, are the same characteristics whichattract regulatory attention. There would, obviously, be lessregulatory agency concern with a slimicide derived from a naturalproduct that would be easily biodegradable.Economics Laboratory has developed an enzyme preparation,designated MX-1361, which could be used as a slime control agent.It disrupts the bacterially produced slime which concentratesparticulates and microbes that form a.deposit. Because of themode of action.of the enzyme, i.e., cleaving carbohydrate bondsin bacterial slimes, the enzyme has the potential to disruptbacterial flocs in the. waste treatment plant as well.. If thiswere to occur, the effluent suspended solids and effluent BODmight rise to unacceptable levels, and also the settling char-acteristics of the sludge might deteriorate to the point ofprocess failureThe objectives of this study were to:1. Determine if the activated sludge process is affectedby the addition of MX-1361, and, .2.Determine if the treated effluent contains toxicityattributable to MX-1361.The approach taken to meet these objectives was to treata sulfite-alkaline chemimechanical pulp mill effluent in benchscale activated sludge reactors and to monitor process perfor-mance and sludge settling characteristics. One reactor wasoperated on mill effluent taken before entering the mill'sbiological treatment, plant. Another, reactor was operated on thesame effluent supplemented with active MX-1361 enzyme preparation.A third reactor was operated on the effluent supplemented withheat inactivated MX-1361 enzyme preparation. Inactive enzyme wasalso used because the enzyme is a protein and could create effluenttoxicity without affecting the activated sludge process.- 4 -The treatment conditions were identical in each of the benchscale units and we're chosen to be similar to the oxygen-activatedsludge plant at the mill. The level of MX-1361 was selected tosimulate normal'operation throughout the paper mill supplementedby a spill of MX-1361 in one paper machine'. Thus, consideringboth the addition of MX-1361 just prior to biological treatmentand the simulated spill, this is probably the highest concentra-tion of MX-1361 that would enter the treatment plant.The bench scale activated sludge reactors were run for 31days. The nominal hydraulic residence time (HRT) was 6 hours,and the nominal mean cell residence time (MCRT) was 8 days.Both of these conditions are typical of operating treatmentplants in the pulp and paper industry. Throughout the courseof the study, the effluent characteristics and sludge settlingproperties were monitored. A test for acute toxicity, asmeasured with Daphnia, was also performed.RESULTS AND DISCUSSIONAt the nominal MCRT of 8 days', 31 days operation was morethan sufficient time to attain steady-state conditions. No sig-nificant operating problems were encountered after adjustment ofthe HRT.5Initially, the HRT was set at 3 hours to correspond withthe HRT in the mill's aeration tank. However, the clarifierson the bench scale units were not large enough -to -handle theflow, and it was necessary to increase the nominal HRT to 6 hours.Thus, instead of attempting to mimic treatment conditions at themill, we attempted to simulate treatment effect, i.e., theremoval of BOD and suspended solids.Presented in Table 1 is a summary of reactor effluentcharacteristics. Also included is selected operating data fromthe mill wastewater treatment plant for comparison.The data show that there was no difference in the effluentcharacteristics of the three bench scale activated sludge systems.Further, all three reactors were operating well within the boundsof typical effluent permits issued by regulatory agencies. Com-parison of the bench scale reactor data with the full scale treat-ment plant shows that the reactors were treating the mill effluentat a slightly higher efficiency. This is expected since there isusually more control over bench scale units, and corrective ac-tions can betaken quicker than on full scale plants.A summary of the activated sludge settling data is presentedin Table 2. The data show that there is no difference in eitherthe initial settling velocities (ISV) or sludge volume indices(SVI) for the bench scale reactors. The ISV is a measure of howrapidly the sludge will settle, while the SVI is a measure of how- 7 -difference in the settling properties of these sludges. MX-1361apparently has no effect on the settling properties of activatedsludge.The last issue to be resolved was related to effluenttoxicity. There was a concern that either the enzyme or thestabilizers in the enzyme preparation might be toxic. Accord-ingly, static, acute bioassays with Daphnia magna neonates wereperformed on the treated:effluents and also on active MX-1361enzyme preparation at a concentration of 400 units/gallon. Asummary of test conditions for these assays is presented inTable 3. An analysis of the data from these assays revealedEC50 values greater than 100% by volume in all cases. Thismeans that no acute toxicity, as measured with Daphnia, waspresenting any of the treated effluents or in the MX-136l enzymepreparation diluted to 400 units/gallon.The last task undertaken was to determine if MX-1361 couldbe detected in the effluent from the reactors. A low.enzymeactivity in the feed to the bench scale reactors was reported,but there was none in the effluent. Either the enzyme had beeninactivated by the strong oxidizing conditions in the reactor orit has been biologically degraded.- 8-TABLE 2.Sludge Settling DataIS Va,ft/hrNo EnzymeActive EnzymeInactive EnzymeMill -operating data3.7 ± 0.3 62 ± 83.9 ± 0.43.7 ± 0.15.8 ± 1.7a. Initial settling velocityb. Sludge volume indexTABLE 3Summary of Test Conditions for,Daphnia magna NeonatesSample SourceNo Enzyme Reactormean initialmean finalDissolvedOxygen,pH mg/L7 .97.98.5.6.6Temp.°C19.021.0EC 5 0% Volume>100Active Enzyme Reactormean initialmean finalInactive Enzyme Reactormean initialmean finalMX-1361 Enzyme Preparationmean initialmean finalREACTOR SVI b ,mls/g64 ± 660 + 461 ± 199.37.48.07.97.87.87 .86.419.021.019.021.021.021.07.77.9>100>100>1007.47.5- 9 -CONCLUSIONSIt can be concluded from this laboratory study that:'1. Enzyme MX-1361 does not affect the operation ofactivated sludge systems,2. MX-1361 does not contribute to toxicity in theeffluent of activated sludge systems arid- cannotbe detected in the effluents of activated sludgesystems.EXPERIMENTALAnalytical TestsChemical analyses were done according to Standard Methods(l) except that color determinations were made according to ahNCASI recommended procedure(2).The settling tests were performed according to standardprocedures (3) except that'a 6-rph stirrer was placed in thegraduated cylinder to assist settling. The SVI test was doneaccording to Standard Methods (1).Bioassays were conducted using Daphnia magna cultured inthe Institute's laboratory for over 100 generations. Procedureswere in agreement with guidelines set forth by the U.S. EPA (4).Specific procedural details are presented in Table 4.- 10 -Biological TreatmentBiological treatment was performed in.3 liter completelymixed activated sludge reactors for 31 days. Each reactor wasbaffled and mechanically stirred to ensure complete mixing.Air was metered. through a water-filled gas washing bottle tominimize evaporation losses in the reactors. The reactorswere,fed at. a rate of 12 L/day, producing a hydraulic resi-dense time of 6 hours. The MCRT was controlled by daily wastingof sludge directly from the reactor. The nominal MCRT was 8 days.TABLE 4Details of Bioassay TestsTest Chambers:Life Stage Tested:Number of Test Organisms:Dilution Water Source:Test Duration:Aeration:Water Hardness:Sample Adjustment for pH:Pretest Storage:Monitored Parameters:Feeding:250-mL beakers, 5 organisms per beakerNeonate, less than 24 hours old20 neonates per concentrationLake Winnebago (lower Fox River headwaters) water filtered through 0.45pmglass fiber filter48 hoursNone during experiment, dilution waternear saturation at outset of experiment167 mg/L as CaCO3None; samples used as receivedNoneDissolved oxygen, pH, temperature and% survival of test organismsTest organisms were not fed during theexperiment- 11 -A minimum level of dissolved oxygen of 1.0 mg/L wasmaintained in the reactors, and concentrations of 1.0 mg/Lnitrogen and 0.5 mg/L phosphorus were maintained in the effluentto prevent nutrient limitations.The reactors were operated until a steady-state condition,as judged by stable effluent quality over time, was reached.Samples were then taken for analyses.Enzyme PreparationThe enzyme preparation is derived from a bacterium. Theenzyme is capable -offdepolymerizing levan, a major component ofbacterial slimes. The enzyme preparation cannot reduce ellulose,hemicellulose, starch, or dextrin; it does have a low level ofproteolytic activity.AcknowledgmentWe thank Messrs Dennis Van Rooy and James E. Beatty ofAppleton Paper's Combined Locks mill for the effluent samples usedin this study.We also thank Mr. Arthur A. Webb and Miss Sally A. Berben ofIPC for laboratory assistance.- 12 -REFERENCES1. APHA, AWWA, and WPCF, Standard Methods for the Examinationof Water Wastewater, 14th Edition, (1976).2. "An Investigation of Improved Procedures for Measurementof Mill Effluent and Receiving Water Color", NCASI TechnicalBulletin No. 253 (December, 1971).3. Vesilind, P., Treatment and Disposal of Wastewater Sludges,Ann Arbor Science, Ann Arbor, Michigan (1974).4. Peltier, W., "Methods for measuring the acute toxicity ofeffluents to aquatic organisms", U.S. EPA Report No.EPA 600/4-28-012 (January, 1978).

The effect of an enzymatic slime control agent MX-1361 activated sludge treatment plants

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The effect of an enzymatic slime control agent MX-1361 activated sludge treatment plants

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