In autumn 2021, Esmil Group held a demonstration of equipment for mechanical wastewater sludge thickening – MDQ-T series screw thickening press. Thanks to the use of this machine, the advantages of MDQ presses also become available in the thickening process!

The MDQ-T series screw thickening presses are based on the same technology and design as the MDQ screw dewatering units; however the main difference of the compacting press is the placement of the screw in an inclined position due to the important role of gravity in the thickening process. An additional advantage of the machine is that it can also work as a dehydrator after setting certain process parameters. The equipment features an energy-efficient and space-saving design, minimal maintenance, very low water consumption and a wide performance range. The MDQ series equipment operates trouble-free for many years and has no wear parts, so it does not require costly repairs or complex maintenance.

To demonstrate the effectiveness of the MDQ-T series screw compacting press in real conditions, ESMIL Prodeko-Ełk launched a demonstration model MDQ-351T at the Municipal Wastewater Treatment Plant in Biskupiec (Poland) in September 2021. This thickening press has one screw with a diameter of 350 mm.

Two types of sludge were thickened, i.e. excess sludge without pre-treatment, subjected only to gravity thickener with rod stirrer, and decayed sludge stored in an unused biological tank, which inadvertently became an open sludge digestion chamber

The results obtained were more than satisfactory:

  • Excess sludge with a concentration of 1.3% of dry matter was compacted to 3.6% of dry matter with a flocculant consumption of 4.5 kg/t of dry matter.
  • Decayed sludge with a concentration of 1.9% of dry matter was compacted to 5.6% at a flocculant consumption of 7 kg/t of dry matter.
  • In both cases the filtrate was clear, with 100 to 300 ppm of total suspended solids.
  • The hydraulic performance of the thickening press ranged from 19 to 22m3/h by inlet sludge.
  • Discharge of thickened sludge comprised about 3 m3/h

Filtrate

Depending on the expected degree of thickening, the dose of flocculant can be changed to obtain the desired result. The unit worked in automatic mode, i.e. after setting the appropriate values on the touch panel, the software automatically controlled the process thanks to the installed sensors and flow meters.

The management of the wastewater treatment plant in Biskupiec was very satisfied with the results and the high efficiency of the unit. MDQ-353 C screw press has been operating on site for several years.

Below we are pleased to quote the words of the head of the wastewater treatment plant, Ms. Monika Wołoszyn:

“Excess wastewater sludge in our wastewater treatment plants is difficult to dewater and compact due to the high degree of fragmentation of particles during the aeration process, so to achieve more than 2% of dry matter in the sludge, we would have to increase the gravitational thickening time, which, in turn, is impossible due to a large amount of excess sludge. The use of the screw thickening press made it possible to quickly thicken the excess sludge, reduce its volume (even by 5.6% of dry matter), obtain a clear filtrate and, most importantly, a very low flocculant consumption. As a result, the total flocculant consumption when using both machines (screw thickening press + screw press dehydrator) was only about 20% higher than in the case of dewatering only with a screw press dehydratorpreceded by a classic gravity thickener An additional advantage was the possibility to combine excess sludge with decayed thickened sludge, which gave an equally good thickening effect (in-house tests: approximately 16 m3/h and 3.2% of dry matter). The screw thickening press can be successfully used in wastewater treatment plants with limited gravity thickening capabilities, as well as for the dewatering of complicated sludge, such as decayed sludge.”

The MDQ-T series screw thickening presses are an excellent solution for wastewater treatment plants that require space-saving, economical and efficient sludge thickening. A wide model range allows optimal adaptation of the unit capacity to the conditions of the site, and a fully automated process ensures virtually maintenance-free operation.