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Supplementation of wastewater process modelling tools to enable the kinetic analysis of sewage sludge composting

100%

Kovacs R. , Mihaltz P. , Csikor Z.

Polish Journal of Environmental Studies

2007

tom 16

nr 6

831-839

This study demonstrates mathematical description of sewage sludge composting based on identification and separate characterisation of simple process parts. For a description of the microbial processes an ASM3-based mathematical model developed for autothermal thermophilic aerobic sludge digestion is used. The oxygen mass transfer was characterized in a separate way. The 2.964T0-3 m2-d-1 value of the oxygen diffusion coefficient in the sludge at 55°C indicates the strong oxygen limitation of the microbial degradation. The model extended with the oxygen mass transfer description has been validated using results from composting experiments performed with different specific sludge-air surface areas and with the renewal of the sludge surface.

Electrical characterization of the root system: a noninvasive approach to study plant stress responses

75%

Cseresnyes I. , Takacs T. , Sepovics B. , Kovacs R. , Fuzy A. , Paradi I. , Rajkai K.

Acta Physiologiae Plantarum

2019

tom 41

nr 10

A pot experiment was designed to demonstrate that the parallel, single-frequency detection of electrical capacitance (CR), impedance phase angle (ΦR), and electrical conductance (GR) in root–substrate systems was an adequate method for monitoring root growth and some aspects of stress response in situ. The wheat cultivars ‘Hombar’ and ‘TC33’ were grown in a rhyolite-vermiculite mixture under control, and low, medium, and high alkaline (Na₂CO₃) conditions with regular measurement of electrical parameters. The photochemical efficiency (Fv/Fm) and SPAD chlorophyll content were recorded non-intrusively; the green leaf area (GLA), shoot dry mass (SDM), root dry mass (RDM), and root membrane stability index (MSI) were determined after harvest. CR progressively decreased with increasing alkalinity due to impeded root growth. Strong linear CR–RDM relationships (R² = 0.883–0.940) were obtained for the cultivars. Stress reduced |ΦR|, presumably due to the altered membrane properties and anatomy of the roots, including primarily enhanced lignification. GR was not reduced by alkalinity, implying the increasing symplastic conductivity caused by the higher electrolyte leakage indicated by decreasing root MSI. Fv/Fm, SPAD value, GLA, and SDM showed decreasing trends with increasing alkalinity. Cultivar ‘TC33’ was comparatively sensitive to high alkalinity, as shown by the greater relative decrease in CR, SDM, and RDM under stress, and by the significantly lower MSI and higher (moderately reduced) |ΦR| compared to the values obtained for ‘Hombar’. Electrical root characterization proved to be an efficient non-intrusive technique for studying root growth and stress responses, and for assessing plant stress tolerance in pot experiments.

Selection of plant physiological parameters to detect stress effects in pot experiments using principal component analysis

63%

Fuzy A. , Kovacs R. , Cseresnyes I. , Paradi I. , Szili-Kovacs T. , Kelemen B. , Rajkai K. , Takacs T.

Acta Physiologiae Plantarum

2019

tom 41

nr 05

Appropriate selection and well-timed measurement of plant developmental, morphological and physiological parameters are essential to maximize efficacy and minimize time consumption of experiments. To select for the most sensitive indicators of drought or salt stress, three independent pot experiments with diverse setups were analysed with 20–20 measured parameters. Parameters of plant growth, phenology and symbiotic interactions, visual stress symptoms, photosynthetic activity, nutrient composition and vitality were studied and the result matrices were evaluated with principal component analysis (PCA). Stress effects manifested in PC1 of two experiments and in PC2 of the third one. Traits assumed to be adequate for stress indication were characterized by high PC1 or PC2 loading values. Beside parameters of biomass production, growth and visible stress symptoms, less evident traits e.g. root electrical capacitance, membrane stability index in roots and leaves, relative water content of leaves and SPAD units were identified.