The rheological behaviour of anaerobic digested sludge

Producing biogas energy from the anaerobic digestion of wastewater sludge is one of the most challenging tasks facing engineers, because they are dealing with vast quantities of fundamentally scientifically poorly understood and unpredictable materials; while digesters need constant flow properties to operate efficiently. An accurate estimate of sludge rheological properties is required for the design and efficient operation of digestion, including mixing and pumping. In this paper, we have determined the rheological behaviour of digested sludge at different concentrations, and highlighted common features. At low shear stress, digested sludge behaves as a linear viscoelastic solid, but shear banding can occur and modify the apparent behaviour. At very high shear stress, the behaviour fits well to the Bingham model. Finally, we show that the rheological behaviour of digested sludge is qualitatively the same at different solids concentrations, and depends only on the yield stress and Bingham viscosity, both parameters being closely linked to the solids concentration

(In Press) Rheological characterisation of municipal sludge: A review

Sustainable sludge management is becoming a major issue for wastewater treatment plants due to increasing urban populations and tightening environmental regulations for conventional sludge disposal methods. To address this problem, a good understanding of sludge behaviour is vital to improve and optimize the current state of wastewater treatment operations. This paper provides a review of the recent experimental works in order for researchers to be able to develop a reliable characterization technique for measuring the important properties of sludge such as viscosity, yield stress, thixotropy, and viscoelasticity and to better understand the impact of solids concentrations, temperature, and water content on these properties. In this context, choosing the appropriate rheological model and rheometer is also important

Clear model fluids for peculiar rheological properties of thickened digested sludge

Optimising flow processes in wastewater treatment plants requires that designers and operators take into account the flow properties of the sludge. Moreover, due to increasingly more stringent conditions on final disposal avenues such as landfill, composting, incineration etc., practitioners need to produce safer sludge in smaller quantities. Anaerobic digestion is a key treatment process for solids treatment and pathogen reduction. Due to the inherent opacity of sludge, it is impossible to visualise the mixing and flow patterns inside an anaerobic digester. Therefore, choosing an appropriate transparent model fluid which can mimic the rheological behaviour of sludge is imperative for visualisation of the hydrodynamic functioning of an anaerobic digester. Digested sludge is a complex material with time dependent non-Newtonian thixotropic characteristics. In steady state, it can be modelled by a basic power-law. However, for short-time processes the HerscheleBulkley model can be used to model liquid-like properties. The objective of this study was to identify transparent model fluids which will mimic the behaviour of real sludge. A comparison of three model fluids, Carboxymethyl Cellulose (CMC), Carbopol gel and Laponite clay revealed that these fluids could each model certain aspects of sludge behaviour. It is concluded that the rheological behaviour of sludge can be modelled using CMC in steady state flow at high shear rates, Carbopol gel for short-time flow processes and Laponite clay suspension where time dependence is dominant

MicroRNAs of Gallid and Meleagrid herpesviruses show generally conserved genomic locations and are virus-specific

AbstractMany herpesviruses, including Marek's disease viruses (MDV1 and MDV2), encode microRNAs. In this study, we report microRNAs of two related herpesviruses, infectious laryngotracheitis virus (ILTV) and herpesvirus of turkeys (HVT), as well as additional MDV2 microRNAs. The genome locations, but not microRNA sequences, are conserved among all four of these avian herpesviruses. Most are clustered in the repeats flanking the unique long region (I/TRL), except in ILTV which lacks these repeats. Two abundant ILTV microRNAs are antisense to the immediate early gene ICP4. A homologue of host microRNA, gga-miR-221, was found among the HVT microRNAs. Additionally, a cluster of HVT microRNAs was found in a region containing two locally duplicated segments, resulting in paralogous HVT microRNAs with 96–100% identity. The prevalence of microRNAs in the genomic repeat regions as well as in local repeats suggests the importance of genetic plasticity in herpesviruses for microRNA evolution and preservation of function

Upper mantle temperature and the onset of extension and break-up in Afar, Africa

It is debated to what extent mantle plumes play a role in continental rifting and eventual break-up. Afar lies at the northern end of the largest and most active present-day continental rift, where the East African Rift forms a triple junction with the Red Sea and Gulf of Aden rifts. It has a history of plume activity yet recent studies have reached conflicting conclusions on whether a plume still contributes to current Afar tectonics. A geochemical study concluded that Afar is a mature hot rift with 80 km thick lithosphere, while seismic data have been interpreted to reflect the structure of a young, oceanic rift basin above mantle of normal temperature. We develop a self-consistent forward model of mantle flow that incorporates melt generation and retention to test whether predictions of melt chemistry, melt volume and lithosphere–asthenosphere seismic structure can be reconciled with observations. The rare- earth element composition of mafic samples at the Erta Ale, Dabbahu and Asal magmatic segments can be used as both a thermometer and chronometer of the rifting process. Low seismic velocities require a lithosphere thinned to 50 km or less. A strong positive impedance contrast at 50 to 70 km below the rift seems linked to the melt zone, but is not reproduced by isotropic seismic velocity alone. Combined, the simplest interpretation is that mantle temperature below Afar is still elevated at 1450◦C, rifting started around 22–23 Ma, and the lithosphere has thinned from 100 to 50 km to allow significant decompressional melting

Increasing the Operation Efficiency of Air Conditioning System for Integrated Power Plant on the Base of Its Monitoring

Increasing the Operation Efficiency of Air Conditioning System for Integrated Power Plant on the Base of Its Monitoring / E. Trushliakov, A. Radchenko, S. Forduy, A. Zubarev, A. Hrych // Advances in intelligent systems and computing. – 2020. – Т. 1113 AISC . – P. 351–360Abstract. The efficiency of reciprocating gas engines of integrated energy systems (IES) for combined electricity, heat and refrigeration generation is strictly influenced by their cyclic air temperatures. To evaluate the effect of gas engine cyclic air deep cooling, compared with conventional its cooling, the data on dependence of fuel consumption and power output of gas engine JMS 420 GS-N.L on its inlet air temperature at varying ambient air temperatures at the entrance of the radiator for scavenge air cooling were received. The results of treatment of gas engine efficiency monitoring proved non-effective operation of conventional chilling all the ambient air, coming into the engine room, because of increased air temperature at the inlet of turbocharger (TC), caused by heat influx from surroundings in the engine room. A new method of gas engine inlet air two-stage cooling at increased ambient air temperatures and advanced cyclic air cooling system with absorption lithium-bromide chiller and refrigerant ejector chiller was proposed. With this chilled water from absorption lithiumbromide chiller is used as a coolant in the first high-temperature stage of engine inlet air cooler and boiling refrigerant of ejector chiller in the second lowtemperature stage