Phosphorus Recovery from Urban Wastewater Treatment Plant Sludge Liquor by Ion Exchange

Abstract

In this study phosphorus recovery from sludge liquor by ion exchange process was investigated. The efficiency of a commercially available anionic iron oxide resin was evaluated in batch and packed column tests using synthetic phosphorus solution and actual sludge liquor, taken from of an urban wastewater treatment plant (UWWTP). When phosphorus recovery from sludge liquor was investigated, experimental data fitted quite well Generalized Langmuir–Freundlich isotherm (R² = 0.92 for the new resin and R² = 0.96 for the regenerated resin); the maximum adsorption capacity being 14.2 and 14.4 mg P/g, respectively. The saturation of adsorption sites was not achieved also after 11.5 hours and 120 bed volumes, in column tests. When the reactor was operated with sludge liquor and the new resin, the saturation of packed bed was achieved after approximately 175 min and 31 bed volumes. The recovery efficiency of phosphorus during the regeneration step was as high as 95% (less than 13 bed volumes). According to the results achieved and the increasing cost of phosphorus production from conventional resources (yearly incremental cost 0.012 €/(kg · y)), its recovery from UWWTPs sludge liquor by the ion exchange process is expected to be really useful and beneficial for the following 10–15 years.

Keywords:

• Generalized Langmuir–Freundlich isotherm
• iron oxide resin
• packed bed column tests
• resin regeneration

ACKNOWLEDGEMENTS

The authors would like to thank EU for the funding received through the ERASMUS exchange programme which allowed Dr. Antonio Bottini to work for six months at Karlsruhe Institute of Technology for his Master thesis. Moreover, Dr. Bottini would like to thank Prof. Erhard Hoffmann and Dr. Justyna Homa for their valuable advice and Dr. Luca Passio and Mr. C. Heidt for their technical support.