Organic loading rate: a promising microbial management tool in anaerobic digestion

This study investigated the effect of changes in organic loading rate (OLR) and feedstock on the volatile fatty acids (VFAs) production and their potential use as a bioengineering management tool to improve stability of anaerobic digesters. Digesters were exposed to one or two changes in OLR using the same or different co-substrates (Fat Oil and Grease waste (FOG) and/or glycerol). Although all the OLR fluctuations produced a decrease in biogas and methane production, the digesters exposed twice to glycerol showed faster recovery towards stable conditions after the second OLR change. This was correlated with the composition of the VFAs produced and their mode of production, from parallel to sequential, resulting in a more efficient recovery from inhibition of methanogenesis. The change in acids processing after the first OLR increase induced a shift in the microbial community responsible of the process optimisation when the digesters were exposed to a subsequent OLR increase with the same feedstock. When the digesters were exposed to an OLR change with a different feedstock (FOG), the recovery took 7d longer than with the same one (glycerol). However, the microbial community showed functional resilience and was able to perform similarly to pre-exposure conditions. Thus, changes in operational conditions can be used to influence microbial community structure for anaerobic digestion (AD) optimisation. Finally, shorter recovery times and increased resilience of digesters were linked to higher numbers of Clostridia incertae sedis XV, suggesting that this group may be a good candidate for AD bioaugmentation to speed up recovery after process instability or OLR increase

The Evolution of Male-Biased Dispersal under the Joint Selective Forces of Inbreeding Load and Demographic and Environmental Stochasticity

Acknowledgments We thank G. Bocedi, S. Palmer, and three anonymous reviewers for helpful comments on earlier drafts. R.C.H. was funded by the Natural Environment Research Council (1271380). Simulations were performed on the University of Aberdeen’s Maxwell high performance computing cluster.Peer reviewedPublisher PD

The valuation of clean spread options: linking electricity, emissions and fuels

The purpose of the paper is to present a new pricing method for clean spread options, and to illustrate its main features on a set of numerical examples produced by a dedicated computer code. The novelty of the approach is embedded in the use of a structural model as opposed to reduced-form models which fail to capture properly the fundamental dependencies between the economic factors entering the production process

E-Learning for Teachers and Trainers : Innovative Practices, Skills and Competences

Reproduction is authorised provided the source is acknowledged.Final Published versio

Cyclic occurrence of gregarine trophozoites (Apicomplexa) in the burrowing echinoid <i>Echinocardium cordatum</i> (Echinodermata, Spatangoidea)

The occurrence of the gregarine Urospora neapolitana in the spatangoid echinoid Echinocardium cordatum was followed monthly over a 1 yr period. Infesting stages (sporozoites) were seen only in the digestive cells of the hosts' gastric caecum while growing stages (trophozoites) only occurred in the hosts' body cavity. Sporozoites showed no variation in abundance over the investigated period. The number of trophozoites, however, clearly varied with a minimum in summer and early autumn. Trophozoite variation appears to be related to the gonadal cycle of the host

Effect of pine bark and compost on the biological denitrification process of non-hazardous landfill leachate: Focus on the microbiology

In an attempt to optimize the cost-efficiency of landfill leachate treatment by biological denitrification process, our study focused on finding low-cost alternatives to traditional expensive chemicals such as composted garden refuse and pine bark, which are both available in large amount in South African landfill sites. The overall objective was to assess the behaviour of the bacterial community in relation to each substrate while treating high strength landfill leachates. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests with immature compost and pine bark. High strength leachate was simulated using a solution of water and nitrate at a concentration of 500 mg l−1. Results suggest that pine bark released large amounts of phenolic compounds and hydroxylated benzene rings, which both can delay the acclimatization time and inhibit the biological denitrification (only 30% efficiency). Furthermore, presence of potential pathogens like Enterobacter and Pantoea agglomerans prevents the applicability of the pine bark in full-scale operations. On the other hand, lightly composted garden refuse (CGR) offered an adequate substrate for the formation of a biofilm necessary to complete the denitrification process (total nitrate removal observed within 7 days). CGR further contributed to a rapid establishment of an active consortium of denitrifiers including Acinetobacter, Rhizobium, Thermomonas, Rheinheimera, Phaeospirillum and Flavobacterium. Clearly the original composition, nature, carbon to nitrogen ratio (C/N) and degree of maturity and stability of the substrates play a key role in the denitrification process, impacting directly on the development of the bacterial population and, therefore, on the long-term removal efficiency

The sources, impact and management of car park runoff pollution: a review

Traffic emissions contribute significantly to the build-up of diffuse pollution loads on urban surfaces with their subsequent mobilisation and direct discharge posing problems for receiving water quality. This review focuses on the impact and mitigation of solids, metals, nutrients and organic pollutants in the runoff deriving from car parks. Variabilities in the discharged pollutant levels and in the potentials for pollutant mitigation complicate an impact assessment of car park runoff. The different available stormwater best management practices and proprietary devices are reported to be capable of reductions of between 20% and almost 100% for both suspended solids and a range of metals. This review contributes to prioritising the treatment options which can achieve the appropriate pollutant reductions whilst conforming to the site requirements of a typical car park. By applying different treatment scenarios to the runoff from a hypothetical car park, it is shown that optimal performance, in terms of ecological benefits for the receiving water, can be achieved using a treatment train incorporating permeable paving and bioretention systems. The review identifies existing research gaps and emphasises the pertinent management practices as well as design issues which are relevant to the mitigation of car park pollution

Quantum nucleation in a single-chain magnet

The field sweep rate (v=dH/dt) and temperature (T) dependence of the magnetization reversal of a single-chain magnet (SCM) is studied at low temperatures. As expected for a thermally activated process, the nucleation field (H_n) increases with decreasing T and increasing v. The set of H_n(T,v) data is analyzed with a model of thermally activated nucleation of magnetization reversal. Below 1 K, H_n becomes temperature independent but remains strongly sweep rate dependent. In this temperature range, the reversal of the magnetization is induced by a quantum nucleation of a domain wall that then propagates due to the applied field.Comment: 5 pages, 4 figure