The recovery of phosphorous compounds from municipal waste water has gained special attention in the last decade because of the serious environmental concerns regarding the direct application of sewage sludge as fertilizer in agriculture. The main problems are the heavy metal contamination and the unknown effects of pathogens and drugs as well as other residues (e.g. microplastics and nanoparticles) potentially accumulating in the field crops and thereby introduced into human food chains. On the other hand phosphorus is an essential nutrient for plants and indispensable in modern crop cultivation. Phosphorus resources are limited and raw minerals from various sources are contaminated with heavy metal ions like cadmium and uranium.
Due to these reasons several research institutions, consortia of municipal companies and industrial associations are focussing the topic of phosphorus recovery, supported by current attempts in changing EU (and German) legislation. Beside the treatment of ashes from sewage sludge incineration several methods based on sorption and precipitation processes have been investigated. Implemented in industrial scale (and economically competitive) are mainly processes generating MAP (magnesium ammonium phosphate). However, there are only limited data available on the commercial application of these products in the fertilizer industry and agriculture.
It is well known that iron hydroxide containing materials are capable of binding oxo-anions from aqueous solutions even at very low residual concentrations. Former investigations of the project partners proved that iron hydroxide containing residues from mining water treatment had similar binding capacities e.g. for phosphate like commercially available products, but significantly lower resource consumption and production costs. Adaption of agglomeration process led to microstructured materials with optimized sorption kinetics and capacities. However, the desorption process was still the limiting step. Since the quality of the phosphorus containing product is substantial for the commercial application the current work is focussing on the development of an integrated recycling process with optimized combination of sorption/induced precipitation of mainly calcium phosphate compounds and their separation from the waste water stream...
Session: L13 - Depth Filtration and Adsorption - Granular Beds
Day: 24 October 2019
Time: 09:00 - 10:15 h