Trust is good. Test is better.
GEA wins over wastewater treatment plant operators with mobile decanter.
The wastewater treatment plant in Hoehr-Grenzhausen, Rhineland-Palatinate, Germany, had been using a decanter for sludge dewatering for more than 17 years. The plant was now due for renewal. With a new screw press or a new decanter. An investment of this magnitude requires careful consideration.
After the operator had first tested a screw press, GEA suggested a trial with a mobile high-performance decanter. The result was surprising, convincing - and justified the confidence in the GEA solution.
WWTP Hoehr-Grenzhausen
The Hoehr-Grenzhausen wastewater treatment plant treats the wastewater of 11,000 inhabitants; the maximum capacity of the plant is 18,000 population equivalents.
Since 2004, the excess sludge at the Hoehr-Grenzhausen WWTP has been dewatered with a decanter together with sludge from a neighboring WWTP.
Screw press or decanter?
The plant is getting on in years, and the energy consumption and performance values of the decanter no longer meet current and future requirements. The Association of Municipal Utilities Hoehr-Grenzhausen are therefore considering a new decanter or a screw press.
Theoretically, it is difficult to compare two technologies with each other and with the existing plant. Therefore, the plant operator decided to conduct two practical tests to find the best possible dewatering system for the plant. First with a screw press and finally with a modern high performance decanter.
This is where GEA came in. Particularly pleasing: through a recommendation from another wastewater treatment plant that had very good experience with a GEA decanter.
Decanter - established in sludge dewatering
Decanters perform key functions in the dewatering and thickening of wastewater sludges with very high reliability.
GEA decanters offer the highest possible dewatering capacities with maximum separation efficiencies, high operational reliability with low wear - and all this with a minimum power consumption of less than 1 kWh/m³.
Test set-up and start on one day
On May 17, 2021, the time had come: At the Hoehr-Grenzhausen wastewater treatment plant, GEA began dewatering the excess sludge on a trial basis. A mobile decanter system was used. The GEA biosolids Decanter prime 4000 provided the plant operator with valuable data on volume flow, polymer addition rate and machine settings. The mobile, fully self-contained sludge treatment plant was up and running on site in a matter of hours.
Mobile GEA decanters - as good as stationary units
GEA mobile decanters are modular, plug-and-play units. They are installed on site as truck trailers or standardized sea containers. The individually adaptable units have all necessary components on board, are completely piped and ready for immediate operation. This allows wastewater treatment plant operators to test the performance and savings potential of GEA decanters during operation - and to make a serious investment decision.
The units are complete, turnkey systems. This means that full-scale tests can easily be carried out in existing wastewater treatment plants. The test results can be transferred 1:1 and form the basis for planning the decanter to be installed later.
The energy consumption of the screw press has been neglected to illustrate that energy costs are not a decisive factor in the investment decision and therefore not an argument against a decanter centrifuge.
Minimum power for maximum performance
It was clear from the outset that the dewatering of the aerobically stabilized excess sludge at the Hoehr-Grenzhausen wastewater treatment plant would work well with the GEA high-performance decanter.
However, it was important for the operator to back up his decision with facts:
- At flow rates of 5-15 m3/h, the GEA biosolids Decanter prime 4000 operates reliably and safely in dewatering mode.
- High plant availability and process reliability are guaranteed.
- A constant degree of dewatering is achieved even with varying feed concentrations and long plant operating times.
- Compared to the screw press and the previous decanter, the GEA decanter has the highest solids recovery, the lowest sludge disposal and lower power consumption (than the competitor's installed decanter).
- The annual costs are significantly lower than the comparable plants.
- In sludge dewatering, the GEA decanter consistently achieves separation efficiencies in excess of 98%. This provides the operator with process and economic planning reliability.
- The personnel costs for operating the GEA decanter are very low.
- Power consumption is very low with a maximum of 1 kWh/m3 sludge.
Significant savings in operating costs - even when compared to other technologies
GEA was able to show the operator that the new decanter would save up to €22,000 per year in operating costs compared to the previous solution. Compared to a new screw press, the savings would be even higher at up to €24,000 per year.
Cumulated over an estimated 15-year operating life, the savings add up to up to €330,000 - with no change in water, electricity, waste disposal, and other costs.
Conclusion
Screw press or decanter: If only the initial cost is compared, the decanter loses. But when deciding on a particular technology, operating costs must also be taken into account. And this over the predicted life cycle of the plant. Here, the GEA decanter is clearly ahead, as the on-site test and the operating cost calculation showed.
The Association of Municipal Utilities Hoehr-Grenzhausen therefore decided in favor of the GEA biosolids Decanter prime 4000, which will take over sludge processing in the wastewater treatment plant from fall 2023.
