SR0033424_ENG DESIGNED PLAN - Laserfiche WebLink

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1 ADVANT MA'NU:AL ll i &M 5 DO level drops,the degree of nitrification will wastewater constituents (i.e., BOD,TSS,TKN, 'I! normally drop as well,which could be a sign etc.). In this rase,the available alkalinity in the t of blinding or saturated flow conditions—any- water supply may not be adequate to accomplish thing that might inhibit free air from flowing the full level of nitrification desired. into the system. (Though it's quite possible to have low filtrate DOs and still have high effluent These constraints exist for all wastewater treat- qualit)6 as measured by BOD and TSS levels.) ment operations,regardless of whether the opera- tion involves a suspended growth contact stabi- Biological Growth on Filter lization process or an attached growth packed j With"fixed film" treatment systems,biological bed filter.Packed bed systems will perform better, i growth on the filter media is natural.The biomat especially if they have a large attached growth ? should appear light-brown to dark-brown in surface area per unit volume ratio, because of the color and gelatinous in texture. micro-sites near the attached side of the biomat, } Influent Characteristics where denitrification typically occurs,returning some of the alkalinity.Textile packed bed filters, Influent characteristics will greatly affect the because of their large surface area per unit amount of nitrogen reduction that is possible volume ratio,tend to perform even better. sfrom any wastewater treatment system. Nevertheless,additional buffering may be neces- pH:For normal residential nitrogen loads, sary to accomplish the level of nitrification i pH typically needs to be 6-8. desired. Alkalirft:Alkalinity is essential for nitrification. For each part ammonia that is nitrified,7.14 parts alkalinity are consumed(buffering the acidity caused by the release of hydrogen ions). I Consequently,if the degree of nitrification is less than expected,it could simply be that there isnt sufficient alkalinity to support more.Typical resi- dential nitrification requires alkalinity above 250± mglL for recirculating processes and double that for single pass processes.Many wastewater streams i do not have sufacient alkalinity to support complete nitrification. f Wastewater streams without sufficient alkalinity to support complete nitrification may,depending on the type of process,cause a depletion in the alkalinity to the point where the pH correspond- ingly drops to a level that causes the microbial activity to degrade(<6±). Recirculating the efflu- ent helps,since half the alkalinity can be restored ' in the recirc or process tank,wherever denitrifica- tion occurs(and adjusting the recite ratios may i also bring the pH back to preferred operating lev- els). But wastewater streams that are alkalinity- starved can't provide for 100%nitrification. The use of low flush fixtures requires special consideration. Low flush fixtures tend to reduce hydraulic loads,which causes elevation of