Carleton Maltby Carleton Maltby
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This 7 page Class Notes was uploaded by Adelia Pouros on Wednesday September 30, 2015. The Class Notes belongs to Carleton Maltby at Western Michigan University taught by Chem Engr in Fall. Since its upload, it has received 27 views. For similar materials see /class/216998/carleton-maltby-western-michigan-university in Paper Engr at Western Michigan University.
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Date Created: 09/30/15
SLUDGE BULKING A secondary biological sludge with poor settling and compaction characteristics I SIGNIFICANCE Why a concern H H w cowownhWNH gt 99P Nt 1 High TSS and associated BOD 0 108 lb BODleSS in ef uent possible permit Violation 2 Difficulty in achieving desired solids in RAS and therefore difficulty in controlling activated sludge system ORIGIN OF HIGH TSS ANDOR SLUDGE SETTLING PROBLEMS Clari er design and condition mechanical problems Uneven ow splitting parallel clarifiers Inlet and outlet structures ow distribution velocity dissipation Flocculation chamber Weir placement and condition Sludge removal mechanism Hydraulic overloading or surges Solids overloading or surges Windcreated or thermalinduced currents Problems Related to Solids Characteristics Pin ee from high shearoveraeration low FM toxicity Dispersed growth from high FM low nutrients Rising sludge from denitriflcation anaerobic conditions Severe foam or scum from surfactants high FM or low FM laments Viscous bulking Filamentous bulking III VISCOUS BULKIN G A Also called slime polysaccharide hydrous nonfilamentous or zoogloeal bulking B Extracellular polymeric substances EPS surround bacterial cells and consist of carbohydrates ie polysaccharides proteins and other substances C EPS is critical to the ability of bacteria to occulate settle and dewater D With Viscous bulking the polysaccharide content is higher than normal which causes the density of the bacteria to be reduced poor settling E Generally caused by a nutrient de ciency not enough nitrogen or phosphorus IV FILAMENTOUS BULKING The most common of settling amp compaction problems A The culprits Filamentous organisms bacteria maybe fungi 1 Their shape is long and narrow length gtgt width 2 They remove BOD good 3 In small concentrations they provide physical support to ocs good 4 At high concentrations they interfere with settling in secondary clarifiers bad 031 Bulking characteristics A Poor compaction of sludge blanket high blanket level but if there is a supernatant it is usually very clear High SVI Sludge Volume Index measure of volume in mL of one gram of settled sludge J Use a lliter graduated cylinder with a 30min settling time SVI settled volume in mLL 1000 mgg initial lVILSS in mgL SVI gt 150 usually a concern but high SVI is treatmentplant specific As SVI rises so may ef uent TSS Sludgc Volume Indrx mm x 800 700 600 gt 500 400 10 107 10 Extended Filmncm Length unim Large strong ocs but which settle poorly 100x microscope Good Floc Structure C Possible Causes These conditions can favor the growth of filamentous organisms which outcompete floc formers MAJOR FOR PULP amp PAPER TREATMENT PLANTS Septicity high sulfide andor volatile organic acid levels 2 Low FM ratio less than 02 03 Low dissolved oxygen less than 2 mgL but a function of FM amp temperature Nutrient deficiency Nitrogen or Phosphorus or possibly trace metals Approximate minimum residuals before clarifier Ammonia NH3 21 mgL as N Orthophosphate P043 2 05 mgL as P But some paper mills with strict permit limits for total P are able to operate successfully at lower levels of orthophosphate A U A MINOR FOR PULP amp PAPER TREATMENT PLANTS 5 Low pH lt65 or pH swings 6 Nature of the BOD high amount of easily degraded organic matter PLUS We may have more to learn D Remedial Measures 1 Treat the symptom shortterm solution usually a Add settling or weighting aids at secondary clarifier Polymers Lime Ferric chloride Alum b Add Toxic Agents Oxidants chlorinehypochlorite peroxide 2 10 lb Clgday1000 lb MLSS Proprietary Biocides pH shock usually add acid 2 Treat the cause longerterm solution a Identify the probable causes by identifying the predominant filamentous organisms identi cation requires expertise FILAMENT TYPES IN PULP AND PAPER ACTIVATED SLUDGE SYSTEMS FILAMENTOUS TYPE ASSOCIATED CONDITION More prevalent Thiothrix ll septicity low nutrients N Thiothrix l septicity low nutrients N Nostocoida limicola ll septicity Type 0914 septicity H hydrossis low dissolved oxygen Nostocoida limicola lll septicity low nutrients P Type 1851 low organic loading low FM Type 1701 low dissolved oxygen Type 021 N septicity low nutrients N Less prevalent Type 0092 septicity Type 0411 septicity Type 0675 low organic loading low FM Sphaerotilus natans low dissolved oxygen Type 0041 low organic loading low FM Type 0581 septicity Type 0803 low organic loading low FM Type 0211 septicity N nitrogen deficiency P phosphorus deficiency b Make operational andor equipment changes to correct the problem such as 0 Add more nutrients 0 Increase aeration 0 Adjust FM Install a selector A SELECTOR is an initial contact zone a separate tank or a sectionalized compartment of short duration 1560 min HRT where primary ef uent and RAS are combined such that the FM ratio is high and the DO level is controlled Selector may be aerated aerobic or not anaerobic or anoxic Selectors are little used in the paper industry dozen mills or so in US Most are aerobic Generally seem to work NOT suitable solution for low nutrients
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