The recovery of nutrients from wastewater by adsorption and ion exchange

Abstract

Nutrients are essential to organisms. N and P are natural nutrients that are needed by plants. Meanwhile an excess of nutrients in water bodies can cause pollution and problems like eutrophication. The recovery of nutrients from waste streams is the research field of this dissertation work. The research focus is on adsorption and ion exchange using new materials and conventional resins. For the removal of ammonium from wastewater, montmorillonite anchored magnetite nanocomposite was developed and used as an adsorbent. The clay-based material is abundant and environmentally friendly. The modified material proved its capability for ammonium remediation during treatment of authentic stormwater sampled from a local landfill plant (in Mikkeli, Finland) and is worthy of further study. To deal with phosphate solving in aqueous solutions, one metal organic framework named MIL-100 (Fe) was applied as the modifier for a laboratory-synthesised Zn-Al layered double hydroxide to form an adsorbent. The adsorbent material was firstly produced as powder and tested for phosphate adsorptive removal. Then polyacrylonitrile was utilised as a polymer frame to combine the powder to form a spherical bead-type composite material. The composite bead operated in columns successfully. The material is applicable for large-scale phosphate recovery operations.

To overcome the limited capacity-focused comparison between column processes, a systematic quantitative methodology was established and applied in the comparison of column processes with different feeding contents and concentrations. The method was reliable and applicable for the purpose of comparing. The conventional resin was found to be a favourable option for the recovery of ammonium through column processes. The recovery of ammonium by conventional resin was conducted with industrial wastewater. The waste stream contained concentrated ammonium. Both laboratory-scale and pilot-scale tests were conducted successfully. A liquid compound fertiliser was generated as a by-product. The conventional resins are favourable for large-scale or industrial scale recovery of nutrients from wastewater. However, the resin has its drawbacks such as being sensitive to pollution. Developing novel adsorbents from various resources with the goal of creating (advanced) multifunctional materials is still a promising endeavour. Further studies are also needed to improve the stability of the novel adsorbents in column applications.