Quantification of Struvite to Avoid Bias in the Assessment of Digester/Dewaterability Performance

Authors:

  • Christopher White - Hazen and Sawyer

Spontaneous struvite (MgNH4PO4 ยท 6H2O) precipitation occurring within municipal anaerobic digesters can create a costly operational challenge if the deposited mineral impacts the mechanical operation of the digester and associated equipment. Additionally, for resource recovery facilities that recover struvite as a sellable product, the loss of struvite to nuisance precipitation within the digester can represent significant lost revenue. For these reasons, the application of technologies and approaches to prevent nuisance struvite precipitation within anaerobic digesters has been a recent industry focus (WERF NTRY1R12). Claims have been made regarding the use of these struvite mitigating technologies as a means for increasing cake solids dryness content, reducing polymer demand and improving digester volatile solids reduction performance at facilities practicing biological phosphorus removal. If true, these benefits to dewaterability and solids stabilization can result in significant costs saving for facilities.

This paper and presentation will review the implications of struvite accumulation within digested sludge and accumulated digester grit with a view to providing insight into the impact that struvite can have on performance assessments. We will also discuss methods for assessing digested sludge and digester grit struvite content so that the impact of mineral deposition on the measurement of volatile solids destruction and sludge solids content can be routinely and adequately assessed.

For more information, please contact the author at cwhite@hazenandsawyer.com.

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