Evaluating the level of ammonia and sulfide in the liquid phase during anaerobic digestion of slaughterhouse waste operating at mesophilic scale digester—the impact of inhibition and process performance

This research article published by AIMS Press, 2020The performance of experimental batch-reactor loaded with slaughterhouse waste at mesophilic temperature was investigated as well as the inhibition of both ammonia and sulfide concentration in the aqueous phase. The digester was operated for 68 days by evaluating the process stability basing on controlling parameters such as pH, volatile fatty acids and alkalinity in relation to the methane produced. The maximum CH4 content of 69.6% was achieved at 0.37 VFA/Alkalinity ratio and pH of 7.51 during day 37 of anaerobic digestion. However, a sudden increase of ammonia nitrogen in the digester from day 44 to day 68 decreased the methane content about 62.15% from 65% to 24.6%. Similarly, as the amount of sulfide content decreased in the liquid phase, gaseous H2S was elevated up to 132 ppm in the 68th day. During this time, it was observed that the ratio of VFA/Alkalinity decreased to 0.16, with a very low concentration of VFA, which was 150.92 mg/L. This phenomenon indicated that all the acids produced were consumed by methanogens and ammonia inhibition was at the highest rate due to the increase of ammonia nitrogen concentration in the last days of digestion. Furthermore, among of peculiar characteristic shown by slaughterhouse waste is the ability to maintain the pH above 7 without the addition of any buffering agent throughout the AD process. Meanwhile, the evaluation of the level of both ammonia and sulfide in the aqueous phase revealed that the inhibitory effect of ammonia concentration was higher than sulfide concentration

Removal of hydrogen sulfide and ammonia from biogas using Oldoinyo Lengai Volcanic ash

A Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of Master’s of Science in Materials Science and Engineering of the Nelson Mandela African Institution of Science and TechnologyOldoinyo Lengai mountain located in Northern Tanzania is the only active natrocarbonatite volcano with unusually alkali-rich natrocarbonatites which are not found elsewhere in the world. Volcanic ash formed earlier during eruptions was collected from different sites along the mountain, and its potency to adsorb hydrogen sulfide (H2S) and ammonia (NH3) from biogas was investigated. The samples were calcinated at different temperatures (550–850 °C) and were characterized by X-ray fluorescence, scanning electron microscopy and X-ray diffraction techniques. The on-site adsorption experiments were conducted at the biogas digester at ambient conditions. The calcinated ash was packed into the reactor bed, biogas allowed to pass through the adsorbent, and the inlet and outlet concentrations of H2S and NH3 were measured. The height of the site where the adsorbent was taken from, calcination temperature, biogas flowrate and mass of the adsorbent were variable parameters and found to influence greatly on the efficiency of H2S and NH3 removal. The efficiency increased with calcination temperature raise and mass of adsorbent and decreased with flowrate increase. The samples collected from the top site of the mountain and calcinated at 850 °C exhibited the best sorption performance (SC) of 1.0 g of S/100 g of adsorbent when the mass of adsorbent of 1 g and the biogas flowrate of 0.002 m3/min were used as standard parameters for this study. Chemisorption of H2S was confirmed via bornite and hexahydrite, while CO2, confirmed via trona, pirssonite and nahcolite while NH3 was detected by gas analyzer

Oldoinyo Lengai Volcanic Ash for Removal of Hydrogen Sulfide and Ammonia from Biogas

This research article published by Scientific research an Academic Publisher, 2018Oldoinyo Lengai mountain located in Northern Tanzania is the only active natrocarbonatite volcano with unusually alkali-rich natrocarbonatites which are not found elsewhere in the world. Volcanic ash formed earlier during eruptions was collected from different sites along the mountain, and its potency to adsorb hydrogen sulfide (H2S) and ammonia (NH3) from biogas was investigated. The samples were calcinated at different temperatures (550℃ - 850℃) and were characterized by X-ray florescent, scanning electron microscopy and X-ray diffraction techniques. The on-site adsorption experiments were conducted at the biogas digester at ambient conditions. The calcinated ash was packed into the reactor bed, biogas allowed to pass through the adsorbent, and the inlet and outlet concentrations of H2S and NH3 were measured. The height of the site where the adsorbent was taken from, calcination temperature, biogas flowrate and mass of the adsorbent were variable parameters and found to influence greatly on the efficiency of H2S and NH3 removal. The efficiency is increased with calcination temperature raise and mass of adsorbent and decreased with flowrate increase. The samples collected from the top site of the mountain and calcinated at 850℃ exhibited the best sorption performance