Hydrolys av överskottsslam för maximerat fosforsläpp - En studie i Bio-P som resurs för näringsåtervinning

Sammanfattning: During the biological phosphorus removal (EBPR) process, the phosphorus accumulating organisms (PAOs) accumulates excess phosphorus in the form of polyphosphorus (poly-P) in the aerobic phase. In the following anaerobic zone, PAOs take up volatile fatty acids (VFAs) and simultaneously releases poly-P. Through hydrolysis of the biosludge, the slowly biodegradable organic carbon is degraded into VFA. Return sludge from two Swedish wastewater treatment plants (Öresundsverket and Lundåkraverket) were used for laboratory experiments of phosphorus release and hydrolysis. The result from the experiments showed a well-functioning biological phosphorus removal for both plants (11.2 and 6.2 mg P/g VSSi •h). However, in the hydrolysis experiments the result differs between the two sludges. Return sludge from Öresundsverket reaches maximum concentration of phosphate (20.3 and 20.5 mg P/g VSSi) after approximately two days. Hydrolysis of return sludge from Lundåkraverket reaches maximum (19.7 mg P/g VSSi) after three and a half days. In the hydrolysis experiments with return sludge from Lundåkraverket, the concentration of phosphate phosphorus decreased when continuously mixing the biosludge. The reason may be that the mixing supplied oxygen into the sludge, but this could not be determined in this study. When the same method for hydrolysis was used for return sludge from Öresundsverket, the concentration of phosphorus did not decrease. The concentration of phosphate phosphorus in the hydrolysis of return sludge from Lundåkraverket reached the maximum level independent of temperature. However, it took more time for the phosphorus release at lower temperature.