Browsing by Author "Heaven, Sonia"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Ammonia inhibition and toxicity in anaerobic digestion: a critical review
    (Elsevier, 2019-07-20) Jiang, Ying; McAdam, Ewan; Zhang, Yue; Heaven, Sonia; Banks, Charles J.; Longhurst, Philip
    As a waste management technology which offers environmental benefit and renewable energy production, anaerobic digestion (AD) has become the preferred technology for the treatment of organic waste. However, in such waste streams nitrogen contents are likely to be high. There is prevailing literature evidence suggests that high ammonia concentration especially its free molecular form (NH3), derived from nitrogen content in substrates is the cause of inhibition and sudden failure of the AD process. This paper comprehensively reviews previous knowledge from digestion studies using high nitrogen waste streams as feedstocks and critically analysed the considerable variations in the inhibition/toxicity levels reported for ammonia. Literature evidences suggest methanogens, particularly acetoclastic methanogens are most susceptible to ammonia toxicity, and therefore this review has a particular focus on the mechanism of the ‘selective’ inhibition to methanogens and the impact of ammonia toxicity to the overall methanogen population in an AD digester. This population change explains in many reported cases that sufficient acclimatisation can significantly alleviate the phenomenon of inhibition and specific requirement of certain trace nutrients. Currently available mitigation strategies for high nitrogen content feedstock digestion are reviewed and discussed in relation to the population change and trace nutrient requirements.
  • Thumbnail Image
    ItemOpen Access
    Investigation of the impact of trace elements on anaerobic volatile fatty acid degradation using a fractional factorial experimental design
    (Elsevier, 2017-09-05) Jiang, Ying; Zhang, Yue; Banks, Charles; Heaven, Sonia; Longhurst, Philip
    The requirement of trace elements (TE) in anaerobic digestion process is widely documented. However, little is understood regarding the specific requirement of elements and their critical concentrations under different operating conditions such as substrate characterisation and temperature. In this study, a flask batch trial using fractional factorial design is conducted to investigate volatile fatty acids (VFA) anaerobic degradation rate under the influence of the individual and combined effect of six TEs (Co, Ni, Mo, Se, Fe and W). The experiment inoculated with food waste digestate, spiked with sodium acetate and sodium propionate both to 10 g/l. This is followed by the addition of a selection of the six elements in accordance with a 26−2 fractional factorial principle. The experiment is conducted in duplicate and the degradation of VFA is regularly monitored. Factorial effect analysis on the experimental results reveals that within these experimental conditions, Se has a key role in promoting the degradation rates of both acetic and propionic acids; Mo and Co are found to have a modest effect on increasing propionic acid degradation rate. It is also revealed that Ni shows some inhibitory effects on VFA degradation, possibly due to its toxicity. Additionally, regression coefficients for the main and second order effects are calculated to establish regression models for VFA degradation.
  • Thumbnail Image
    ItemOpen Access
    Quantifying the percentage of methane formation via acetoclastic and syntrophic acetate oxidation pathways in anaerobic digesters
    (Elsevier, 2017-04-07) Jiang, Ying; Banks, Charles; Zhang, Yue; Heaven, Sonia; Longhurst, Philip J.
    Ammonia concentration is one of the key factors influencing the methanogenic community composition and dominant methanogenic pathway in anaerobic digesters. This study adopted a radiolabelling technique using [2-14C] acetate to investigate the relationship between total ammonia nitrogen (TAN) and the methanogenic pathway. The radiolabelling experiments determined the ratio of 14CO2 and 14CH4 in the biogas which was used to quantitatively determine the percentage of CH4 derived from acetoclastic and syntrophic acetate oxidation routes, respectively. This technique was performed on a selection of mesophilic digesters representing samples of low to high TAN concentrations (0.2–11.1 g kg−1 wet weight). In high TAN digesters, the ratio between 14CO2 and 14CH4 was in the range 2.1–3.0; indicating 68–75% of methane was produced via the hydrogenotrophic route; whereas in low ammonia samples the ratio was 0.1–0.3, indicating 9–23% of methane was produced by the hydrogenotrophic route. These findings have been confirmed further by phylogenetic studies.
  • Thumbnail Image
    ItemOpen Access
    Scaling-up engineering biology for enhanced environmental solutions
    (American Chemical Society, 2024-06-21) Hassard, Francis; Curtis, Thomas P.; Dotro, Gabriela C.; Golyshin, Peter; Gutierrez, Tony; Heaven, Sonia; Horsfall, Louise; Jefferson, Bruce; Jones, Davey L.; Krasnogor, Natalio; Kumar, Vinod; Lea-Smith, David J.; Le Corre Pidou, Kristell; Liu, Yongqiang; Lyu, Tao; McCarthy, Ronan R.; McKew, Boyd; Smith, Cindy; Yakunin, Alexander; Yang, Zhugen; Zhang, Yue; Coulon, Frederic
    Synthetic biology (SynBio) offers transformative solutions for addressing environmental challenges by engineering organisms capable of degrading pollutants, enhancing carbon sequestration, and valorizing waste (Figure 1). These innovations hold the potential to revolutionize bioremediation strategies, ecosystem restoration, and sustainable environmental management.