Project Synopsis

Develop a testing protocol for solid waste sludge characterization that would help predict the morphology of a particular sludge feed being fed into the client’s custom sludge dryer equipment at a waste treatment facility that was experiencing difficulty maintaining consistent feed rate and product moisture level.

Project Summary

Sludge fed to the sludge dryer installed at a waste treatment facility has exhibited significant variability, resulting in difficulty maintaining consistent feed rate and product moisture level.  Normal (e.g., “good”) dryer feed is a moist, crumbly solid that falls through the sifter screen, rains down onto the dryer belt, and dries quickly and uniformly. In contrast, “bad” feed extrudes through the sifter screen as long cylinders before breaking off and falling onto the belt, where they often agglomerate and dry poorly.

Past efforts have been made to identify the variables that govern sludge morphology, though none have been successful.  Feed can be good in the morning and bad in the afternoon, or vice-versa, with no apparent change in processing variables.  To better understand which variables affect sludge morphology, and to identify early on if a dewatered sludge will process without problems, the client, an environmental consulting company and manufacturer of advanced sludge dryer systems, retained Process Engineering Associates, LLC (PROCESS) to develop a testing protocol.  After an exhaustive search, PROCESS identified two standard soils tests that have the greatest applicability to the morphology of the sludge – Shear Strength and Atterberg Plastic Limit.

Modified versions of these two tests were successfully developed by the project team to provide the client with an applicable test protocol for predicting how a sludge may behave in the drying process. The data gathered from these tests show a quantitative correlation between shearing and the cohesiveness of the material.   In addition, they also show the magnitude of change that occurs due to shearing time and processing steps.

Industry Type

  • Municipal Solid Waste Processing
  • Custom Process Equipment Design and Manufacturing.



Utilized Skills

  • Process evaluation
  • Analytical test methods identification
  • Process troubleshooting.


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