title: Production of volatile fatty acids from wastewater screenings using a leach-bed reactor.
abstract: Screenings recovered from the inlet works of wastewater treatment plants were digested without pre-treatment or dilution using a lab-scale, leach-bed reactor. Variations in recirculation ratio of the leachate of 4 and 8 l/lreactor/day and pH values of 5 and 6 were evaluated in order to determine the optimal operating conditions for maximum total volatile fatty acids (VFA) production. By increasing the recirculation ratio of the leachate from 4 to 8 l/lreactor/day it was possible to increase VFA production (11%) and soluble COD (17%) and thus generate up to 264 g VFA/kg-dry screenings. These VFA were predominantly acetic acid with some propionic and butyric acid. The optimum pH for VFA production was 6.0, when the methanogenic phase was inhibited. Below pH 5.0, acid-producing fermentation was inhibited and some alcohols were produced. Ammonia release during the hydrolysis of screenings provided adequate alkalinity; consequently, a digestion process without pH adjustment could be recommended. The leach-bed reactor was able to achieve rapid rates of screenings degradation with the production of valuable end-products that will reduce the carbon footprint associated with current screenings disposal techniques.
authors.affiliation: National University of Colombia, Engineering Department, Carrera 32 No 12-00, Palmira, Colombia. Electronic address: lscadavidr@unal.edu.co.
authors.forename: Luz Stella
authors.initials: LS
authors.lastname: Cadavid-Rodríguez
authors.affiliation: University of Leeds, School of Civil Engineering, Leeds LS2 9 JT, United kingdom.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Horan
mesh_terms: D000143:Acids / Q000378:metabolism*; D019149:Bioreactors; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D000143:Acids; D005232:Fatty Acids, Volatile; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Acidification; Anaerobic digestion; Hydrolysis; Volatile fatty acids; Wastewater screenings; pH