· Case study,Wastewater treatment,Sludge dewatering,Polymer,Flocculants

Optimising Sludge Management at the Municipal 

Solid Waste Incinerator - Case Study

Sludge disposal is becoming an issue at the municipal solid waste incinerator (MSWI), especially for environmental and economic reasons. A case study of the optimization of the sludge management system was undertaken at the MSWI in the Czech Republic. The aim of the applied research presented in this case study is sludge management optimization by a mobile sludge dewatering press unit with optimal polymer combination for dewatering. With respect to the Czech standards, the proposed mechanical equipment must respect the sludge properties, scope and concentration of solids, physical characteristics of wastewater with sludge, aggressive and corrosive conditions, effects of abrasive substances and effects of additives used in wastewater treatment, i.e., flocculants.

Laboratory jar test

The flocculation jar tests were performed in the laboratory of CHEM.ENGI s.r.o. Flocculants, suitable for mechanical industry and sludge treatment were selected: anionic and cationic flocculant. On the polymer selection test were used the combination of polymers with the commercial brand YESfloc®. A suitable selection of flocculant means a volume of polymer, smaller volume of dewatered sludge, which saves 25 - 30% of opex. Flocculant could be used in a production lines of different industries, as are mining, cosmetics etc. To assess the flocculating tests variants, a methodology was defined based on the visual evaluation.

Pilot test – Selection of sludge dewatering equipment

Three pieces of sludge dewatering equipment were tested, one of which was Volute, the sludge dewatering press pilot unit, with a requirement for the selection of a suitable flocculant.

The results of dewatering the representative sample were compared with the performance of proposed equipment. Besides these two parameters, we also assessed the advantages and disadvantages of the considered mechanical equipment for soggy slag sludge dewatering such as: automated operation, operating demands, discontinuous operation, service availability and, last but not least, acquisition price. The main preferred advantages are: minimal requirements for operation (automated operation), minimum cleaning requirements, and discontinuous operation - these requirements are met by Volute, the sludge dewatering press. In order to verify the right selection of the equipment, pilot testing of a small sludge dewatering press was conducted under real conditions at the WWTP.

Pilot test – Selection of chemicals

Two flocculants were used during the pilot testing, which did not fully meet the expectations. Therefore, laboratory flocculation tests were performed followed by evaluation.

During the 1st phase we recommend joint dosing of mixed coagulant Yesfloc PA20 with anionic flocculant Yesfloc AWE30 with a concentration of 0.5%. During the 2nd phase, cationic flocculant Yesfloc CWE35 in a concentration of 3% is added to the sample. By using proposed polymers YESfloc® the proposed sludge treatment process at the MSWI does not require any additional high pH adjustment (around pH 12). By maintaining the current pH value, the metal compounds remain in insoluble form, which subsequently improves the quality of filtrate and increases dewatering efficiency.

As an optimum solution, a mobile sludge dewatering press unit has been proposed with a suitable flocculant combination which makes the sludge management with the proposed optimization a waste-free system without the necessity to carry out laborious and costly bottom ash tank and retention tank cleaning. These results can be transferred into optimizing ST of others MSWIs. Current research is focused on performing further flocculant tests for optimal combination of dewatering.



Jakub Raček 1, Natalia Anferova 2, Petr Hluštík 1,* and Petr Hlavínek 1,

1 AdMaS Research Centre, Faculty of Civil Engineering, Brno University of Technology, Purkyňova 651/139,

612 00 Brno, Czech Republic; racek.j@fce.vutbr.cz (J.R.); hlavinek.p@fce.vutbr.cz (P.H.)

2 CHEM.ENGI s.r.o., Za Tratí 207, 252 19 Chrášťany, Prague, Czech Republic; info@chem-engi.com

* Correspondence: hlustik.p@fce.vutbr.cz; Tel.: +420-541-147-735

† Presented at the 3rd EWaS International Conference on “Insights on the Water-Energy-Food Nexus”,

Lefkada Island, Greece, 27–30 June 2018.

Publisher: https://www.mdpi.com/2504-3900/2/11/651

Full case study: PDF file

CHEM.ENGI s.r.o. Za Tratí 207, 252 19 Chrášťany, Praha západ, Czech Republic 

Tel: +420 211 150 135

info*chem-engi.com (please replace * with @.)

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