The environmental monitoring (EM) is an essential part of protection of the environment, most of the methods of environmental protection based on visual techniques or physico-chemical and biochemical measurements. The automation of traditional methods proceeds at an accelerating rate, modern laboratories prefer this type of tools to conduct a more comprehensive assessment and online monitoring. The application of computer image analysis methods in biomonitoring brings to this discipline the opportunity to develop innovative tools that allow for more precise sensitive and quantified assessment of monitored processes. The application of techniques based on computer image processing technology will dominate in the future and very comfortable and intuitive tool for researchers in the study of the components of the environment quality. The article presents some methods of automation the acute toxicity bioassay based on the application of computational methods.

Physicochemical studies on wastewater quality and microscopic analyses of activated sludge are necessary to properly evaluate the condition of activated sludge. The aim of this study was to evaluate the application of the sludge biotic index to determine when a change in treatment quality is short-lived, caused by, e.g., a change in influent quality or quantity, and when it indicates adverse changes in the biocenosis of activated sludge, which would very likely result in the lower efficiency of wastewater treatment in the near future. The objects of the study were two identical parallel running small wastewater treatment plants. The following indicators of contamination were analyzed: the chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), and total suspended solids (TSS). The authors additionally carried out a microscopic analysis. The study confirmed a correlation between the sludge biotic index and the removal efficiency of COD and BOD₅; however, no correlation was found between the sludge biotic index and the removal efficiency of total suspended solids. The presence of metazoan microorganisms coincided in time with a good effluent treatment efficiency. When their quantity declined, a decrease in the efficiency of wastewater treatment was also observed.

The studies of the rheology of digested pulp from agricultural biogas plants have often been fragmentary and non-standardised due to their complexity and time-consuming nature. As a result of measurements, it was possible to develop a procedure and range of measurements for the correct determination of the parameters of the carrier substance. The applicability of the coaxial cylinder measurement system was demonstrated for assessing the rheological parameters of digested pulp from a fermenter that utilises agricultural biomass. To determine the characteristics of solid particles, the Zingg diagram was used, inter alia, allowing the comparison of particles from each fraction. The analysis of the shape and size of solid particles may help to describe the onset of motion of this phase, flow type, or sedimentation type. The authors propose a completely new research approach to obtain an appropriate, repeatable test conditions of medium, which is the carrier liquid from the biogas plant reactor. The proposed methodology and the scenario of the entire study make it possible to achieve scalable and comparable test results in any laboratory. The proposed solution eliminates the influence of most external factors on the sample and rheological measurements, and the effectiveness of the presented procedure was confirmed in tests.

This investigation specifically aims to enhance the understanding of digestate flow and mixing behavior across typical temperatures in bioreactors in agricultural biogas plants, facilitating energy-efficient mixing. Experimental tests confirmed that digestate exhibits non-Newtonian characteristics, allowing its flow behavior to be captured by rheological models. This study validated that digestate rheology significantly varies with temperature, which influences flow resistance, mixing efficiency and overall energy requirements. Two rheological models—the Bingham and Ostwald models—were applied to characterize digestate behavior, with the Ostwald model emerging as the most effective for Computational Fluid Dynamic (CFD) simulations, given its balance between predictive accuracy and computational efficiency. Specifically, results suggest that, while three-parameter models, like the Herschel–Bulkley model, offer high precision, their computational intensity is less suitable for large-scale modeling where efficiency is paramount. The small increase in the accuracy of the shearing process description does not compensate for the significant increase in CFD calculation time. Higher temperatures were found to reduce flow resistance, which in turn enables increased flow rates and more extensive mixing zones. This enhanced mass transfer and mixing potential at elevated temperatures are especially pronounced in peripheral areas of the bioreactor, farthest from the agitators. By contributing a model for rheological behavior under realistic bioreactor conditions, this study supports the optimization of energy use in biogas production. These findings emphasize that temperature adjustments within bioreactors could serve as a reliable control strategy to maintain optimal production conditions while minimizing operational costs.

In this paper, the preliminary study on the impact of filamentous particles (FP) in the septic tank effluent (STE) on filter cake (FC) development was presented. The number, length and diameter (30 p./cm³, 451 and 121 μm, respectively, on average) of FPs were measured using microscope image analysis of STE samples condensed using a vacuum evaporation set. Results of this study showed, that 0.73% of volatile suspended solids (VSSs) mass from the STE occurs in the form of FPs. No correlation between FP total mass and VSS was found. An experiment with a layer of FPs simulated by ground toilet paper was conducted and showed the impact of this layer (4.89 mg/cm²) on wastewater hydraulic conductivity – for an FC with FPs (FC–FP), hydraulic conductivity was seven times lower than for the FC without the FP layer, and on outflow quality (lower concentration of organic matter expressed as chemical oxygen demand (COD) in effluent from the FC–FP filter than in the effluent from the FC filter: 618 and 732 gO₂/m³, respectively). Despite a relatively small amount of FPs in STE solids (as volume fraction), they play an important role in FC development due to their relatively high length and low degradability. Probably relatively small pores of the FC containing FPs (FC–FP) caused a small particle blocking and a decrease in permeability.