VTA Biocitran^® FORTE: Better dewatering and twice the savings.

“Sewage sludge should look like this,” says Simon Rieder, the wastewater treatment plant manager, as he scoops a dark, crumbly mass from a pile that constantly drips with fresh sludge. On top of the pile, a screw press is operating at the Gastein Valley Clean Water Protection Association's treatment plant, which is responsible for wastewater disposal for the municipalities of Bad Gastein, Bad Hofgastein, and Dorfgastein. These names are familiar in winter tourism, and the plant's seasonal peak loads are correspondingly high.

However, in January of this year, in the middle of the high season, the wastewater sludge did not look ideal. The dry residue from the two digesters remained below 20% during dewatering and could not be increased even with the addition of large amounts of polymer. This was reason enough to consult VTA's experts.

Following analyses conducted in the field and in the laboratory, the experts' final recommendation was VTA Biocitran^® FORTE. This innovative, citric acid-based product improves floc structure, binds dissolved organic matter, and provides clearer filtrate. Optimizing dewatering in this way results in higher dry residue, lower polymer consumption, and less backwashing for the plant.

5% increase in dry residue

In practice, these advantages were confirmed almost perfectly in the Gastein Valley. Immediately after starting the dosing of VTA Biocitran^® FORTE, significant positive effects became measurable. Dry residue increased by more than 5% (to over 25%), and polymer consumption decreased by over 30% per ton of dry residue.

The fact that these effects are attributable to VTA Biocitran^® FORTE became clear when the product was temporarily unavailable at the plant: dry residue immediately dropped to 18.9%. When dosing of the high-performance VTA product was restarted, the parameters improved significantly within the same day (dry residue 24.4%, see graph). “And this happened without us making any other changes at the plant. This shows just how effective VTA Biocitran^® FORTE is,” adds Simon Rieder.

For the Gastein Valley Clean Water Protection Association, a dry residue increase of more than 5% means significant savings in the disposal of thermally recycled wastewater sludge since last year: "We are already paying more than €65 per ton, and this trend is still rising. Better dewatering means cash savings," says association director Peter Müllner. Polymer consumption is also significantly reduced, with a decrease of approximately one-third. This also represents a significant saving.

Tried and tested cooperation

Peter Müllner has known VTA for many years and holds them in high regard. When he took over the management of the Gastein Valley clean water protection association in 1999, plans to expand the treatment plant were already on the table. The plant dates back to 1981 and was initially expanded to 37,000 PE. This figure was regularly exceeded significantly during the ski season.

Despite this discrepancy, it was possible to optimize operations with VTA so that the treatment capacity always fully met the specifications. “Together, we utilized the plant's full potential. The experts were impressed by the results that could be achieved with the activated sludge process,” explains Müllner.

This meant that the multi-million euro expansion project could be postponed for several years. However, in 2019, based on a simulation by the Vienna University of Technology, an additional 1,500 m³ activated sludge tank and other measures were finally implemented. The treatment plant has now been expanded to 60,000 PE. Meanwhile, the 200-kilometer sewer network has been completely renovated, and external water inflow has been reduced by more than half, from six million to three million cubic meters per year. When engineer Peter Müllner retires this summer, his successor, Lukas Leitner, MSc, will take over a state-of-the-art facility that reliably meets requirements thanks to many years of cooperation with VTA.