To keep up with EPA standards and regulations, Waste Water Treatment Plants are continually searching for the best means and newest technology for sludge applications. It's not surprising that these Plants have put time and research into new Sludge Dryers. However, there are several points to consider. Not only does a new Sludge Dryer come with a very high price tag, but there are many other issues to contend with.
With a new Sludge Dryer, conveyance is a big problem. Sludge builds up, damages equipment, and prevents burners from lighting. This in turn can cause a major disruption in operations. Furthermore, there is a guaranteed need for fuel for Dryers, whereas sludge fuels a Multiple Hearth Furnace and reduces the dependency on natural gas.
It is said that Dryer systems will create a final product that will be sellable. However, there is no guaranteed market for the final product. Currently the demand for land application is low and Washington DC, for example, only sells 5% of what they make. Since a Dryer reduces hauling 60:1 and a Multiple Hearth Furnace reduces hauling 200:1, there will be a higher cost to haul the final product from a Dryer.
Lastly, a new Sludge Dryer will cost upwards of $10s of Millions. To upgrade an existing Multiple Hearth Furnace and make it compliant, the price should fall in the range of $4 to $6 million. Not to mention, the operators are already familiar with Multiple Hearth Furnaces and do not need training. Dryers would require retraining, and again, this will increase the price tag.
Overall, there area many points to consider when looking to invest in a new Sludge Dryer as a replacement of an existing Multiple Hearth Furnace. Conveyance, total final product, and price are all several factors influencing these decisions. Ultimately, upgrading a Multiple Hearth Furnace is more economical and will meet EPA requirements.
Click the Dryers vs. MHF Rehab link below to see an excerpt from a recent presentation for a WWTP:
 Dryers vs. MHF Rehab (486.23 KB)
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