Removal and Recycling of Phosphorus from Wastewater Using Reactive Filter Material Polonite®
Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
Literature reviews and laboratory work were used to examine the phosphorus removal efficiency of the reactive filter material Polonite®. This material is produced from the calcium carbonate and silica based rock Opoka. The thesis mainly focuses on adsorption of phosphorus from wastewater with Polonite® but also discuss the possibilities of recycling the filter and the adsorbed phosphorus back into agriculture. This would be beneficial to the environment and a path to a sustainable use of phosphorus. It is important to reduce the employment of phosphorus because of the upcoming “Peak Phosphorus” and the negative impact that an excess of the nutrient has on water bodies. The two main objectives of this thesis were to evaluate and display the phosphorus sorption capacity of Polonite® in a breakthrough curve and to obtain adsorption isotherms of phosphorus on Polonite®. To achieve these objectives experiments were performed in a pilot-plant and in a laboratory at Hammarby Sjöstadsverk. A 500 kg Polonite® filter was connected to flow of wastewater of 400 L/hr and samples were collected and analyzed regularly. The filter did not perform as well as expected, having already shown promising results in other experiments. This is most likely due to the high flow of wastewater and to a too short residence time. The phosphorus reduction was down to 60 % after approximately 30 days and a breakthrough was noticed after 53 days. When saturated, the filter contained 0.6 kg of phosphorus, the equivalent of a sorption capacity of 0.12 %. The pH in the effluent from the Polonite® filter was 10.2 at the first measurement but then dropped fast. When the filter was saturated the pH was down to 8.7. The breakthrough curve gave some indications of that the saturated Polonite® filter might be able to release adsorbed phosphorus. It was also concluded that the Polonite® filter was acting mainly by sorption and thus reduced the dissolved, but not much of the particular, phosphorus.Equilibrium experiments were conducted using solutions with different concentrations of phosphorus. 1 g of Polonite® was added to each solution which was then stirred. With the help of adsorption isotherms the maximum loading capacity was estimated at 330 mg of phosphorus per gram of Polonite®. This corresponds to a 33 % capacity and is a very high number.
Recommendations for future studies would be to further examine the wastewater residence time in the Polonite® filter to improve sorption capacity of phosphorus. It could also be interesting to redo the equilibrium experiments to obtain a more probable loading capacity. The possible presence of pharmaceuticals and/or heavy metals in the filter is also important to investigate, as is the economic aspect of the employment of Polonite® filters for removal of phosphorus from wastewater.
Place, publisher, year, edition, pages
2012. , 43 p.
Phosphorus, Polonite®, adsorption, filter, removal, recycling, recovery, wastewater treatment
IdentifiersURN: urn:nbn:se:kth:diva-145868OAI: oai:DiVA.org:kth-145868DiVA: diva2:720771
Bachelor of Science in Engineering - Chemical Engineering