Electro-dewatering applies a continuous direct electric current to a layer of partially dewatered biosolids cake through a cathode and an anode, thereby employing electrophoresis and electroosmosis to increase both the rate and extent of further dewatering — percent solids in
excess of 40% are readily attainable. No polymer addition is required. Pathogen reduction to Class A levels is typically achieved, through coulombic heating and electrical effects, and the resulting product intermediate typically has reduced odor. While the process relies on electricity,
it has the ability to remove water for a third of the energy required for drying. Since advanced biosolids processing that produces a Class A product (e.g., drying, gasification) typically involves water removal, the questions arise: “Would it be more energy-efficient and/or more cost-effective
to integrate electro-dewatering into biosolids processing; and for which processing methods will it offer the biggest contribution?” To address these questions, a “desk-top” evaluation was conducted to prepare comparisons for advanced biosolids processing with and without
electro-dewatering. Comparisons were made at three different facility sizes to observe the effects of scale. An overall total of 28 cases were developed for comparison, including variations that included add-on technologies (solar drying, lime addition) in order to meet Part 503 Vector Attraction
Reduction (VAR) and produce a Class A product with electro-dewatering. The results showed that integrating electro-dewatering into advanced biosolids processing is situationally worthy of consideration. Factors favoring its use were high biosolids disposition cost, a desire to produce a
Class A biosolids, and low rates for electricity. In particular, integrating electro-dewatering + solar drying was attractive for small-to-medium-sized facilities desiring to take a sustainable, Class A approach.
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