Case study: Transforming Sludge Dewatering and Thickening at South Dearborn

Multi-disk screw press

Equipment installed:

  • two of MDQ-353CLD Multi-disk screw press
  • one of MDQ-353TLD Multi-disk thickener
  • a total of three polymer feeders
  • and five shaftless screw conveyors.

Esmil’s representative in Indiana, American Pump Repair and Service, worked closely with the engineering firm and the plant to devise the best plan to solve the plants issue with underperforming belt thickening and conventional screw press dewatering equipment. In addition to this problem the existing machines were accumulating higher operating costs related to resource consumption (flushing water, electrical, polymer consumption, labor) and higher maintenance cost (wear parts, broken part replacement, maintenance labor and downtime). Also, the higher cost related to wetter cake material being transported to landfill was compounding quickly. Something needed to be done to address all these issues.

The plan of attack:

Look for technology with very low maintenance and operating cost. A technology that is simple to operate and will require no special qualifications of a certified factory technician. Something that can run hands free and produce results above the stated requirements. Esmil was awarded the job due to the certainty that Esmil equipment would outperform the exiting thickening and dewatering equipment and meet all other requirements mentioned above.

Action items:

Replace the belt thickening press before the digestor with a 3-drum Esmil multi-disk thickener. And, replace conventional screw press with two 3-drum Esmil multi-disk screw presses. One of the two screw presses to be a redundant press and not required for full production. All conveyance in the dewatering area to be provided new. The new shaftless screw conveyors were designed and manufactured by Esmil allowing seamless integration between machines and conveyance and providing multiple discharge zones for truck haul-away.

Final results:

The exiting belt thickener was removed and taken out of commission. In its place the new Esmil MDQ-353TLD was installed to thickened sludge feeding the anaerobic digestor. The Esmil thickener was sized to meet the stated requirement of up to 450 gpm infeed of 0.8% TS WAS and thicken to 4.5%. The unit was installed and commissioned and is currently exceeding expectations.

The required total sludge feed to the multi-disk screw presses is 180 gpm. The MDQ-353CLD dewatering press was required to dewater and produce up to 18% DS cake. The MDQ dewatering press selected included a double mixing tank design, one of several designs available through Esmil. The dual tank design provides a fully adjustable high speed “pre” mixing tank where infeed sludge and polymer first come together, and flocculation begins. This tank is followed by a larger tank with another mixing motor where floc formations can be adjusted by the operator if needed.

As in so many other projects, Esmil included polymer feeding as part of the package. When ancillary equipment such as polymer feeder, sludge pump, cake conveyors etc. are provided, Esmil gladly assumes all responsibility of monitoring and controlling the equipment making the entire unit a finely tuned system.

Success!

Installation and startup went smoothly, and the equipment supplied by Esmil is performing above and beyond stated requirement and will likely do so for many years to come. Dry cake results are greater than 18%, filtrate quality is greater than 98% and polymer consumption is very efficient and less than expected! Thank you to all who have made this possible!

Successful machine start-up was completed August of 2023.

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