The paper presents a study on the possibility of using the laser diffraction method for measuring the size of the activated sludge particles. Susceptibility of the particles to mechanical disintegration, dependent on the programmed value of stirring intensity, was observed (stirring was caused by required dynamic flow of analysed suspension through the measurement unit). According to the conclusions presented in this paper, it may be assumed that the laser diffraction method can be applied for measurement of activated sludge particle diameters under the following conditions: 1) the size of activated sludge particles measured by the laser diffraction method is not a real value, but after standardisation of measurement conditions can be treated as a parameter describing the sludge; 2) the particle diameters of activated sludge should be stabilised before the measurement, eg by mixing in the measurement unit or by ultrasound waves application.

The effect of ion‐exchange substrate Biona‐312 additions to nickel (Ni)–polluted soil on yield and mineral composition of cherry tomato and cucumber was evaluated. The plants were grown on the following media: untreated soil (the control series) and soil with added Ni (40 and 100 mg of Ni kg⁻¹, respectively) as well as Biona‐312 (2 and 5% mass additions, respectively). In the presence of 40 mg of Ni kg⁻¹ of soil, the plant yield did not change significantly, whereas in conditions of 100 of mg Ni kg⁻¹, it decreased significantly. Biona‐312 application on Ni‐polluted soil increased the productivity of both species. The content of macronutrients in the plant biomass varied depending on the growth stage, Ni level, and Biona‐312 dose. For both species, higher Ni content was observed in the aboveground organs than in roots, but tomato contained more Ni than cucumber. Biona application reduced the Ni content in plant biomass of both species after being introduced into soil with a higher Ni level.

The presented study aimed at determining the influence of the increasing dose of new Z-ion zeolite substrate on the growth of maize (Zea mays L.) as species belonging to energy crops. In order to achieve the study aim, the pot experiment was carried out where the plants were grown on six series of media i.e.: on marginal soil (the control series I), on arable soil (the control series II) and on four mixtures of marginal soil with increasing Z-ion substrate addition (1%, 2%, 5%, 10 % v/v). The pot test was carried out in a phytotron with a 13/11 light/dark regime. After the end of the experiment, the mean values of the vegetative parameters (wet and dry biomass of roots and stems) characterizing the plant growth in particular media series were determined. The C:N ratio for maize stems was calculated as well. The obtained study results showed a favorable influence of Z-ion substrate additions on the vegetative growth of maize. Already a 1% (v/v) substrate addition to marginal soil increased the wet and dry stems biomass by 173-204%. At the same time, it turned out that in the sixth week of plant growth, a 5% substrate addition to the marginal soil enables to achieve the value of vegetation parameters at a level similar to that of the parameters characterizing the plant development on arable land. Thus, at an early stage of plant growth, a 5% substrate dose can be considered as one allowing a similar course of maize growing on marginal soil as in the case of arable soil. It is worth noting that at this substrate dose, the C:N ratio in maize stems reached the value of 13.05, at which the plant biomass is the substrate ensuring the fairly proper course of methane fermentation supplying fuel in the form of biogas.

The effect of small additions of ion exchange substrate (nutrient carrier) on root development and accompanying ground cohesion (characterized by its penetration resistance) was studied. During two pot experiments Dactylis glomerata L. was grown on sand and its mixture with 1 and 2% (v/v) of ion exchange substrate, respectively. The number and total length of roots were measured during the first test. Penetration resistance was measured with a pentrologger, following the second experiment. After six weeks of growth, number and length of roots in sand mixture with 1 and 2% substrate was greater than in sand-only medium by 211-287 and 273-323%, respectively. At the same time, penetration resistance in series with substrate additions was significantly higher than in control medium at depth of 2.5-7(8) cm, whereas after 12 week of growth, penetration resistance in series with 1 and 2% substrate additions was significantly greater than in control sand at the whole analyzed depth. The highest resistance values in media with substrate additions 2-2.5 times greater than those in sand alone – were observed at depth of 3.5-4.0 cm. Higher resistance of sand-substrate mixtures results from more intensive development of root systems, forming a mesh which binds sand particles. Such media would be less susceptible to erosion.

Investigations concerned the effect on plant productivity in sand of a small addition of the standard ion-exchange substrate Biona-312, compared with alternative additions of the ion-exchange substrate Mp and a mixture of NPK monoionic forms—the latter both prepared from used ion-exchangers. The addition to sand of 2% v/v of the Biona-312 substrate increased the total orchard-grass yield 9.78-fold, and the total yield of birds-foot trefoil 6.47-fold. The effect of adding the Mp substrate and NPK monoionic forms was also very pronounced (with yields 1.66 to 4.49 times greater than in the control), although more limited than that obtained with the standard substrate Biona-312. The results therefore confirmed that additions of fertilizers prepared from used ion-exchangers are of value in the recultivation of degraded soils—something that allows the benefits of utilizing spent ion-exchangers to be combined with those of soil reclamation.

The article presents the relations between the saprobic index S as well as the biocenosis structure indices and BOD₅, the latter being the main parameter of the wastewater quality. Estimation was carried out for the essential indices: saprobic index S, taxon richness Δ_Sr(Δ*), Shannon-Wiener index H (H*), evenness index V (V*), MacArthur's index E (E*) and “proportionality” index P (P*), calculated for saprobes present in wastewater with different levels of pollution (characterized by BOD₅ values). For the calculation of the above mentioned indices, numbers and abundances of species (indices without asterisk) as well as the numbers and abundances of easily identified morphological-functional groups (indices with asterisk) were used. To determine the dependences between the indices and BOD₅, an analysis of correlation was carried out. Results showed that: (i) the value of BOD₅ for treated (or self-purified) wastewater can be assessed most accurately by using index E*—a slightly less precise evaluation of this parameter can be obtained on the basis of indices: H*, S, and H; (ii) bioindication based on biocenosis structure indices (E*, H,* and H) gives results comparable to and even more accurate than those obtained with the use of the saprobic index S; (iii) bioindication can be based on counting individuals (without assigning them to a species) in groups easily differentiated by well-observed morphological features.