Investigation of Readily Degradable Carbon Source Production by Hydrolyzing Sludge and Reject water at Ängen planned WWTP

Sammanfattning: As form of effort to mitigate the increase of pollution level that caused by human activity, Ängen wastewater treatment plant (WWTP) will be built in Lidköping as part of the European LIFE project (LIWE LIFE). Ängen WWTP will be operated based on enhanced biological phosphorus removal (EBPR) technology. This treatment plant is projected to be cost effective and resource efficient, therefore this treatment plant will rely on the biological process to recover the energy and the resources from the treatment plant’s stream. In EBPR technology, a readily degradable carbon source availability is needed to have an efficient removal process. To maintain the removal process the availability of readily degradable carbon source is need to be fulfilled. Volatile fatty acids (VFAs) are readily degradable carbon that results from the hydrolysis process on the sludge mixture. By introducing the VFAs back to the EBPR system, the necessity of the readily degradable carbon source can be fulfilled. This study is investigating the impact of the sludge mixture on the hydrolysis yield, rate, and VFAs production. The sludge mixture used was activated sludge (AS) / primary sludge (PS) and activated sludge (AS) / reject water (RW) from the primary sludge thickener. The sludge mixture was hydrolyzed for 10 days under temperature 13oC. The experiment with AS/PS mixture resulting in higher hydrolysis rate, hydrolysis yield, and VFAs production compared to the experiment with the AS/RW mixture. The highest hydrolysis rate and hydrolysis yield were generated by 50% AS : 50% PS composition. The hydrolysis yield rate is 84 mg/g TS and 0.44 mg/g TS×h-1 respectively. The highest hydrolysis rate and hydrolysis yield that was obtained by AS/RW are 38-40 mg/g TS and 0.21-0.23 mg/g TS×h-1 respectively by adding 5-10% of reject water in the experiment.The sludge mixture with more primary sludge composition is producing more VFAs and less phosphate (PO43-) and ammonia (NH4+). While the sludge with more activated sludge composition generating more phosphate (PO43-) and ammonia (NH4+) and fewer VFAs. The small amount of reject water addition in the experiment batch is improving the hydrolysis and generating more VFAs compared to the VFAs generated by only activated sludge. This result shows the potential and the benefits of the sludge mixture hydrolysis to achieve the cost effective and resources efficient wastewater treatment plant.