Liquid fraction produced in anaerobic digestion (AD) of biodegradable waste can be treated on-site with microalgae, which can be recycled back as substrate to the biogas plant. For this research, a ...pilot high rate algal pond (HRAP) was set with connections to a full scale biogas plant that enabled the use of waste heat and CO2 from a combined heat and power gen-set (CHP). The microalgal mix produced in the thermophilic anaerobic digestate supernatant was tested as a substrate for biogas production in the thermophilic AD (i.e. untreated, bioaugmented with anaerobic bacteria Clostridium thermocellum, and thermally pretreated, respectively). The methane potential of the untreated microalgal mix was low (157.5 ± 18.7 mL CH4/g VS). However, after the thermal pretreatment of the microalgae, methane production increased by 62%, while in the bioaugmentation with C. thermocellum under thermophilic conditions (T = 55 °C) it was elevated by 12%. The outcome of our pilot trial suggests that microalgae produced in the thermophilic biogas digestate represent a prospective alternative AD feedstock. At the same time, microalgae reduce the digestate nitrogen and COD to the level sufficient for the outflow to meet the quality required by the sewage system (ammonia-nitrogen max 200 mg/L, nitrite max 10 mg/L).
•A pilot plant for treating thermophilic anaerobic digestate supernatant with microalgae was constructed outdoor (89 m2).•The removal efficiency by algal treatment of digestate was 83–97% for NH4-N, and 81–95% for COD.•By a continuous 63-day treatment under favorable weather conditions 22.5 g of TS/day/m2 of a microalgal mix was produced.•Biomethane potential of thermally pretreated microalgal mix showed significantly elevated methane production (+62%).•Bioaugmentation with Clostridium thermocellum increased methane production from microalgal mix by 12%.
This paper presents an innovative self-tuning nonlinear controller ASPECT (advanced control algorithms for programmable logic controllers). It is intended for the control of highly nonlinear ...processes whose properties change radically over its range of operation, and includes three advanced control algorithms. It is designed using the concepts of agent-based systems, applied with the aim of automating some of the configuration tasks. The process is represented by a set of low-order local linear models whose parameters are identified using an online learning procedure. This procedure combines model identification with pre- and post-identification steps to provide reliable operation. The controller monitors and evaluates the control performance of the closed-loop system. The controller was implemented on a programmable logic controller (PLC). The performance is illustrated on a field test application for control of pressure on a hydraulic valve.
Soil samples were obtained from Slovenian industrial region Šaleška dolina and aqueous leachates were prepared. The toxicity and genotoxicity potential of these aqueous fractions have been evaluated ...by in vitro toxicity and genotoxicity bioassays. Freshwater toxicity test (PROTOXKIT FTM) with a ciliate protozoan Tetrahymena thermophila, and genotoxicity comet assay using Tetrahymena thermophila, Caco-2 and HepG2 cell lines were performed. Biological data were completed through chemical analyses. It has been shown that physico-chemical analyses alone may not be sufficient to characterize soil hazards. To study soil ecotoxcity it is therefore necessary to take into consideration both, the physico-chemical analyses, toxicity and genotoxicity assays.
The presented self-tuning nonlinear controller ASPECT (advanced control algorithms for programmable logic controllers) is intended for control of a practically important class of nonlinear processes ...that may be presented by a set of low-order local linear models. The model is obtained by means of experimental modelling using an online learning procedure that combines model identification with pre- and post-identification steps that provide reliable operation. There is a choice of several control algorithms suitable for different processes that may be used for control and whose parameters are automatically tuned from the model. The controller monitors the resulting control performance and may react to detected irregularities. The choice of the controller structure and algorithms allows implementation on available industrial hardware, such as programmable logic controllers (PLCs) or open controllers, and simplifies configuration of parameters.
