BEST OF THREE WORLDS – COMBINED BENEFITS OF DIGESTION, ALKALINE STABILIZATION AND DRYING
In summation, CDM feels that both the Rotary Drum Drying System, and the Combined alkaline drying System are two excellent sludge stabilization processes, and Middletown would be successful with either option. However, based on the advantages and disadvantages presented above, the recommended BMP to be implemented at the Middletown WWTP is a combination of advanced ATAD and the Combined alkaline drying™ System with utilization of the end product via a distribution and marketing program. The benefits of a combination BMP are numerous. For instance, the inclusion of ATAD not only increases stabilization by bringing in a biological digestion process but also reduces the sludge volume to be processed later on in the Combined alkaline drying system, which in turn decreases the sizing requirements and overall cost of the combined alkaline drying system. The combination offers the City high product quality and Class A redundancy. That is, Class A biosolids can still be produced even if one of the systems must be taken off-line. In addition, the combined alkaline drying system provides product flexibility with its many blending options that can be taken advantage of to match resultant products to various markets. Finally, the recommended BMP affords Middletown the ability to store digested, heat-dried biosolids to match market and regulatory requirements.
To facilitate funding and implementation, the plan will be implemented in a phased manner. ATAD will first be constructed in Phase I. This will be followed by a future implementation of alkaline drying. Figure 2 shows a new site plan for the Phase I facilities. Figure 3 is a new process flow schematic for the solids processes. With this plan, the City can enjoy the benefits provided by digestion to reduce solids and the risk of odorous product. ATAD also has the added benefit of meeting Class A pathogen reduction. The future implementation of alkaline drying will provide flexible Class A processing, with the capability to produce Class A alkaline or non-alkaline products. Alkaline drying can produce products in the 65-70 percent dry solids range with no elevated use of chemicals admixtures. Phase I of this plan is currently under design.
Document Type: Research Article
Publication date: January 1, 2005
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