RESUMEN
This study explicated the functional activities of microorganisms and their interrelationships under four previously reported iron reducing conditions to identify critical factors that governed the performance of these novel iron-dosed anaerobic biological wastewater treatment processes. Various iron-reducing bacteria (FeRB) and sulfate reducing bacteria (SRB) were identified as the predominant species that concurrently facilitated organics oxidation and the main contributors to removal of organics. The high organic contents of wastewater provided sufficient electron donors for active growth of both FeRB and SRB. In addition to the organic content, Fe (III) and sulfate concentrations (expressed by Fe/S ratio) were found to play a significant role in regulating the microbial abundance and functional activities. Various fermentative bacteria contributed to this FeRB-SRB synergy by fermenting larger organic compounds to smaller compounds, which were subsequently used by FeRB and SRB. Feammox (ferric reduction coupled to ammonium oxidation) bacterium was identified in the bioreactor fed with wastewater containing ammonium. Organic substrate level was a critical factor that regulated the competitive relationship between heterotrophic FeRB and Feammox bacteria. There were evidences that suggested a synergistic relationship between FeRB and nitrogen-fixing bacteria (NFB), where ferric iron and organics concentrations both promoted microbial activities of FeRB and NFB. A concept model was developed to illustrate the identified functional interrelationships and their governing factors for further development of the iron-based wastewater treatment systems.
RESUMEN
This study evaluated feasibility of resource recovery from iron-based sewage sludge from a novel Fe(III)-dosed anaerobic bioreactor used for wastewater treatment. Sludge samples were calcined at five different temperatures (300, 350, 400, 450, and 500 °C) to investigate the transformation of the sludge into different magnetic phases of iron oxide particles. The material phase analysis revealed the presence of 14 to 39 wt% magnetite and 8 to 19 wt% maghemite for different temperature treatments, which indicate the successful conversion of sludge materials into magnetic particles. This magnetic conversion was further confirmed by magnetization measurements of the sludge byproducts that found a 6.3 to 10.9 emu/g saturation magnetization and a 0.7 to 2.0 emu/g remanent magnetization. Due to surface effects phenomenon of nanocrystals, the magnetization values were observed to increase with calcination temperature along with the crystallinity and crystallite size of the thermally-treated sludge materials. This indicates the crystallinity of the samples played a significant role in determining the magnetization properties of the sludge byproducts. Phosphate adsorption capacity and kinetics of the sludge byproducts were evaluated for the samples calcined at 350 and 500 °C. Both samples showed a high phosphate adsorption capacity, but the sample treated at 350 °C showed relatively higher capacity presumably due to smaller crystallite size and reduced crystallinity of the particles in the sample. This study demonstrated that a simple thermal treatment of the sludge can render dual benefits of recovering magnetic particles and further utilizing them for beneficial applications.
Asunto(s)
Fósforo , Aguas del Alcantarillado , Adsorción , Anaerobiosis , Compuestos Férricos , Hierro , Fenómenos Magnéticos , Eliminación de Residuos LíquidosRESUMEN
Damage to the inferior and fragile water and sanitation infrastructure of Haiti after Hurricane Matthew has created an urgent public health emergency in terms of likelihood of cholera occurring in the human population. Using satellite-derived data on precipitation, gridded air temperature, and hurricane path and with information on water and sanitation (WASH) infrastructure, we tracked changing environmental conditions conducive for growth of pathogenic vibrios. Based on these data, we predicted and validated the likelihood of cholera cases occurring past hurricane. The risk of cholera in the southwestern part of Haiti remained relatively high since November 2016 to the present. Findings of this study provide a contemporary process for monitoring ground conditions that can guide public health intervention to control cholera in human population by providing access to vaccines, safe WASH facilities. Assuming current social and behavioral patterns remain constant, it is recommended that WASH infrastructure should be improved and considered a priority especially before 2017 rainy season.