title: Influence of pH on hydrothermal treatment of swine manure: Impact on extraction of nitrogen and phosphorus in process water.
abstract: This study investigates the influence of pH on extraction of nitrogen and phosphorus from swine manure following hydrothermal treatment. Conditions include thermal hydrolysis (TH) at 120°C and 170°C, and hydrothermal carbonisation (HTC) at 200°C and 250°C in either water alone or in the presence of 0.1M NaOH, H2SO4, CH3COOH or HCOOH. Phosphorus extraction is pH and temperature dependent and is enhanced under acidic conditions. The highest level of phosphorus is extracted using H2SO4 reaching 94% at 170°C. The phosphorus is largely retained in the residue for all other conditions. The extraction of nitrogen is not as significantly influenced by pH, although the maximum N extraction is achieved using H2SO4. A significant level of organic-N is extracted into the process waters following hydrothermal treatment. The results indicate that operating hydrothermal treatment in the presence of acidic additives has benefits in terms of improving the extraction of phosphorus and nitrogen.
authors.affiliation: Energy Research Institute, School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: U
authors.initials: U
authors.lastname: Ekpo
authors.affiliation: Energy Research Institute, School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom. Electronic address: a.b.ross@leeds.ac.uk.
authors.forename: A B
authors.initials: AB
authors.lastname: Ross
authors.affiliation: Institute for Public Health and Environmental Engineering, School of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom; Departamento de Ingeniería Química, Universidad Nacional de Colombia, Campus La Nubia, Manizales, Colombia.
authors.forename: M A
authors.initials: MA
authors.lastname: Camargo-Valero
authors.affiliation: Institute for Public Health and Environmental Engineering, School of Civil Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: L A
authors.initials: LA
authors.lastname: Fletcher
mesh_terms: D000818:Animals; D002244:Carbon / Q000737:chemistry; D005591:Chemical Fractionation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008372:Manure; D009584:Nitrogen / Q000737:chemistry / Q000302:isolation & purification*; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification*; D013464:Sulfuric Acids / Q000737:chemistry; D013552:Swine; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water
chemical_list: D008372:Manure; D013464:Sulfuric Acids; D014867:Water; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen; C033158:sulfuric acid
keywords: HTC; Manure; Nutrient recovery; Process water; pH