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Solids handling processes at this facility include liquid sludge storage and two combined gravity belt thickener/presses. Either liquid or dewatered biosolids are applied to farmland. The City of Hutchinson is required by the State of Minnesota to provide 180 days of sludge storage. As a result of the 503 regulations and changing farm practices, the City was interested in improving their solids handling capabilities and flexibilities.
Donohue completed an investigation to explore the advantages of developing a Class A biosolids product. It was anticipated that the Class A biosolids would increase demand for the biosolid and decrease biosolids disposal costs. Facilities planning concluded drying and storing the dried material was cost-effective.
The selected technology uses a unique single-pass direct dryer with a pelletizer, which converts the biosolids to "pellets" that have many reuse applications. Other dryer appurtenances included sludge conveyors, including an indexing conveyor; wet cake bin; coolers; baghouse for exhaust dust collection; storage silos; and dried biosolids truck loading facilities.
As a pilot test project, the pellets were applied as fertilizer to a local golf course with exceptional results. Since then, the City has developed a sales and marketing plan for other applications.
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