Residuals Growing Media Mixer Development

PDF version

Numerous residuals generated by municipalities and industries may be used in single-use beneficial management opportunities alone.  However, additional value can be obtained by combining these residuals to make a product.  Examples include fabricated growing media, reclamation mixes and specialty soil products for wetland restoration or landfill closure.  The development of these products depends on a thorough understanding of the physical, chemical and biological characteristics of the individual feedstock residuals, as well as the intended function of the final mixed product.  Through over a decade of research SYLVIS has demonstrated the value of these unique residuals-based products; however a technology was required to combine these residuals in precise ratios to obtain the operational-scale production of a consistent product.

To address this challenge SYLVIS assessed different mixing and screening equipment (screen decks, pug mills, feed mixers, hammer mills) to identify a technology that would work with various residuals.  Attributes of several of the technologies could be useful, but no one technology could intimately mix the range of feedstock ingredients to create a uniform product.  The equipment must handle residuals that are dry and caustic, heavy and abrasive, as well as sticky and wet.  SYLVIS needed precise control on feedstock mix ratios and mixing duration.  The mixing technology also needed to be portable and cost effective and operationally efficient.

Based upon the information we obtained through our lab-scale research activities and our assessment of existing equipment, SYLVIS developed a team of material management experts; including structural and mechanical engineers, millwrights, steel suppliers and equipment fabricators, to design and build an operational residuals mixer prototype.  This SYLVIS mixing technology has proven itself capable of producing large operational volumes of residuals-based fabricated soils and reclamation mixes.  The mixer has been used to combine pulp sludge, ash, wood waste and fluidized bed waste sand to fabricate a landfill closure soil.  Municipal biosolids, dredged river sand, and wood waste have been mixed to produce growing media for regional parks, school playgrounds and greenhouses.

Our understanding of residuals concurrent with the development of a residuals mixing technology has enabled SYLVIS to create cost effective value-added products providing additional proven, accepted residuals management options.