| 1. |
- Kholoma, Ezekiel, et al.
(författare)
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Leachability and plant -availability of phosphorus in post-sorption wastewater filters fortified with biochar
- 2019
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Ingår i: Environmental technology. - : Taylor & Francis. - 0959-3330 .- 1479-487X. ; 40:27, s. 3641-3651
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Tidskriftsartikel (refereegranskat)abstract
- Sand and gravel are widely applied for filtering pre- or primary-treated wastewater in small-scale wastewater treatment (SWT) systems. However, ecological materials continue to attract increasing interest in use as retrofits for achieving better performance in removing dissolved contaminants and recovering nutrients from wastewater. In this study, we assessed the plant availability and leachability of phosphorus (P) from sand (Sa) and gas concrete (GC) media previously fortified with biochar (BC) and used for phosphorus (P) removal in laboratory-scale packed bed reactors and field-scale constructed filter beds. Batch and leaching experiments were conducted, with distilled water and ammonium lactate (AL) solutions (1:20 solid–liquid (w/v) ratio) applied as extractants. In the findings, reference (Sa) and fortified (Sa-BC) sand filters leached 11.2 and 20.5 mg P kg−1 respectively, to percolating water while the P seemed less likely to leach from GC systems. Extraction with AL showed that P retained in GC was plant-available and that GC could release up to 90 mg kg−1 of the bound mass. These findings highlight the need to evaluate risks of nutrient leaching from filter media for SWT systems especially where groundwater and surface water are final recipients of such effluents. For greater sustainability of use of the media, the weakly bound P in media such as Sa and BC and strongly bound in media such as GC types of materials may be recovered by recycling the spent material to agriculture. However, this may require re-design of the treatment system especially with respect to particle size to make recycling technically feasible.
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| 2. |
- Renman, Agnieszka, 1969-
(författare)
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On-site wastewater treatment : Polonite and other filter materials for removal of metals, nitrogen and phosphorus
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bed filters using reactive materials are an emerging technology for on-site wastewater treatment. Chemical reactions transfer contaminants from the aqueous to the solid phase. Phosphorus is removed from domestic wastewater by sorption to filter materials, which can then be recycled to agriculture as fertilisers and soil amendments. This thesis presents long-term column and field-scale studies of nine filter materials, particularly the novel product Polonite®. Phosphorus, nitro-gen and metals were removed by the mineral-based materials to varying degrees. Polonite and Nordkalk Filtra P demonstrated the largest phosphorus removal capacity, maintaining a PO4-P removal efficiency of >95%. Analysis of filter bed layers in columns with downward wastewater flow, showed that phosphorus, carbon and nitrogen content was vertically distributed, with de-creasing values from surface to base layer. Polonite and Filtra P accumulated 1.9-19 g P kg-1. Nitrogen in wastewater was scarcely removed by the alkaline filter materials, but transformation from NH4-N to NO3-N was >90%. Pot experiments with barley (Hordeum vulgare L.) revealed that after wastewater treatment, slags and Polonite could increase plant production. Batch experi-ments and ATR-FTIR investigations indicated that amorphous tricalcium phosphate (ATCP) was formed in the materials, so some of the accumulated PO4-P was readily available to plants. Low heavy metal contents occurred in the materials, showing that they can be applied as soil amend-ments in agriculture without contamination risks. A full-scale treatment system using Polonite as filter material showed an average PO4-P removal efficiency of 89% for a 92-week period, indicat-ing the robustness of the filter bed technology.
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