Germany – Wastewater treatment plant construction work – Projekt Phoenix - Vergabe von Planung, Lieferung, Montage und Inbetriebnahme einer Biogasentschwefelungsanlage

The wastewater treatment plant Bitterfeld-Wolfen, which was commissioned in 1994, is one of the most modern and largest wastewater treatment plants in Central Germany. In addition to the treatment of industrial and commercial wastewater from the chemical region in and around Bitterfeld-Wolfen, which dominates in terms of cleaning performance, municipal wastewater from the catchment area of the Westliche Mulde wastewater association is also treated here. In addition, the plant is integrated into groundwater treatment at the site. Since 2012, the wastewater from a methylcellulose manufacturer has been anaerobically pretreated, during which biogas is produced, which is converted into electricity and heat in combined heat and power plants (CHP). Before the biogas can be utilized, hydrogen sulfide (H2S) must be removed from the biogas. For this purpose, a first new biogas desulfurization plant was already built and put into operation in 2020. In 2019, as part of the Phoenix expansion project, it was tested on a laboratory scale whether further wastewaters are suitable for anaerobic pretreatment. As a result, a new wastewater stream, the wastewater from a membrane and ion exchange resin manufacturer, was added to the anaerobic pretreatment in 2024. The MIA wastewater is characterized by a high concentration of very well degradable COD and a high sulfate concentration, which averages 2,600 mg/l. Calculations have shown that H2S concentrations of up to 70,000 ppm can occur in the biogas, depending on the proportion of MIA wastewater in the total wastewater quantity. A two-stage chemical-biological scrubbing process is used in the biogas desulfurization plant built in 2020. The first washing stage is carried out in countercurrent by contacting the biogas with a slightly alkaline washing solution (NaOH), where the H2S is bound as sodium sulfide or sodium hydrogen sulfide. The cleaned biogas leaves the washing column towards gas conditioning and the washing liquid enriched with sodium sulfide/sodium hydrogen sulfide passes into the second stage, where, with the addition of oxygen (aeration), the sulfide is oxidized to elemental sulfur by microorganisms. Sodium hydroxide for the alkaline washing solution is regenerated, which is returned to the first stage. The minor loss of alkalinity must be compensated for by NaOH metering. The entire quantity of MIA wastewater can only be anaerobically pretreated after a second biogas desulfurization plant has been built. This second biogas desulfurization plant is the subject of this tender procedure. The bidder's task is to design and size a second functional biogas desulfurization plant based on the design data, so that it is capable, together with the existing plant, of processing the H2S concentrations and loads. A two-stage chemical-biological scrubbing process must also be used for the new biogas desulfurization plant to be constructed.