Removal of phosphorus from wastewaters by

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Universidade Nova de Lisboa,. Campus da Caparica, Edifício Departamental,. Piso 3, gab. 364,. 2829-516 Monte da Caparica,. Portugal. E-mail: [email protected].
2019

© IWA Publishing 2013 Water Science & Technology

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Removal of phosphorus from wastewaters by biomass ashes R. Barbosa, N. Lapa, H. Lopes, A. Morujo and B. Mendes

ABSTRACT Removal batch assays of phosphates from a synthetic wastewater (SWW) and a pulp and paper mill wastewater (PPWW) with two forestry biomass ashes were performed. The supernatants were not only chemically characterized but also the ecotoxicity was determined using two organisms: Vibrio fischeri and Artemia franciscana. The addition of fly ash and bottom ash to the SWW in solid/liquid (S/L) ratios of 3.35 and 9.05 g L1, respectively, achieved removal percentages of phosphates >97% for both ashes. The addition of fly ash and bottom ash to the PPWW in S/L ratios of 34.45 and 46.59 g L1, respectively, yield removal percentages of phosphates >90% for both ashes. According to the results of the Langmuir and Freundlich isotherms, the removal of phosphates from the SWW was mainly explained by surface removal mechanisms, while the removal from the PPWW was partially explained by multi-layer mechanisms. The supernatants resulting from the treatment of SWW and PPWW with both biomass ashes did not present acute ecotoxicity. Key words

R. Barbosa N. Lapa (corresponding author) A. Morujo B. Mendes Faculdade de Ciências e Tecnologia, Department of Sciences and Technology of Biomass, Universidade Nova de Lisboa, Campus da Caparica, Edifício Departamental, Piso 3, gab. 364, 2829-516 Monte da Caparica, Portugal E-mail: [email protected] H. Lopes Laboratório Nacional de Energia e Geologia, Unidade de Tecnologias de Conversão e Armazenamento de Energia, Campus do Lumiar, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal

| biomass ashes, ecotoxicity, pulp and paper mill wastewater, removal of phosphates

INTRODUCTION Several chemical and biological treatment processes to remove P from wastewaters have been studied in recent years (Wood et al. ; Pratt & Shilton ). Within the group of chemical processes, the use of residues to remove P from wastewaters has been attempted in several works (for example, Yang et al. ). This is an interesting topic, because of the high P-adsorption capability of some sub-products and their low cost. Nevertheless, some sub-products require a previous thermal activation before their use as efficient adsorbents, increasing the cost of the final adsorption product (Xiong et al. ). Hence, the reuse of subproducts from thermal processes would be much more interesting, because they avoid the thermal activation pre-treatment. The use of ashes resulting from the forestry biomass power plants (biomass ashes) becomes in this context a very interesting issue, because they have high concentrations of active Ca, Al, and Fe that can participate in phosphate removal. Moreover, heavy metals are present in trace or even undetectable concentrations in these ashes (Ahmaruzzaman ; Singh et al. ). doi: 10.2166/wst.2013.455

The main objectives of this work were to (i) study the potential of biomass ashes to remove phosphates from both a synthetic wastewater (SWW) and a pulp and paper mill wastewater (PPWW) and (ii) assess the ecotoxicity impact caused by the addition of these ashes to both wastewaters.

MATERIAL AND METHODS Origin and characterization of biomass ashes Two types of biomass ashes were used in this study: fly and bottom ashes. They were collected in a biomass power plant that produces electricity by burning forestry residues (bark of eucalyptus and pine). The bottom ash was collected in the bottom of the furnace and fly ash was collected in the bag-house filters. In a previous work (Barbosa et al. ), both biomass ashes were characterized for (i) particle size distribution (ISO 3310-2 ) and (ii) chemical composition through acidic digestion (USEPA Method 3051A ).