Treatment of electropolishing industrial wastewater and its impact on the immobilisation of Daphnia magna.

The amount of industrial pollution entering the environment and its impact on living organisms is an ongoing concern. At the same time, due to an increasing awareness, new methods of wastewater treatment are being explored that are not only effective but also environmentally acceptable. Meeting environmental standards for permitted concentrations is a necessity, but investigating the effects of wastewater on living organisms is also an important issue. In this paper, the influence of metal ions (Fe(III), Cr(III), Ni(II), Cu(II)) in industrial wastewater from electropolishing of stainless steel on Daphnia magna has been investigated. Daphnids have been exposed to wastewater both before and after treatment (Ca(OH)2 precipitation, sorption with peat). Immobilisation in a 48-h acute toxicity test and EC50 has been determined. In the case of studied industrial wastewater, the organic content (expressed as total organic carbon) of the effluent has a positive impact in terms of the survival of D. magna and increases the range of heavy metal concentrations tolerated by them. The application of a two-stage process with Ca(OH)2 neutralisation followed by sorption with peat allows for the removal of almost 100% of metal ions from the wastewater. The reduction obtained ensured a limited impact on D. magna and a decrease in immobilisation to less than 10%. Proper execution of the wastewater treatment process ensures a reduction of its negative impact on living organisms.

Modelling of percolation rate of stormwater from underground infiltration systems.

Underground or surface stormwater storage tank systems that enable the infiltration of water into the ground are basic elements used in Sustainable Urban Drainage Systems (SUDS). So far, the design methods for such facilities have not taken into account the phenomenon of ground clogging during stormwater infiltration. Top layer sealing of the filter bed influences the infiltration rate of water into the ground. This study presents an original mathematical model describing changes in the infiltration rate variability in the phases of filling and emptying the storage and infiltration tank systems, which enables the determination of the degree of top ground layer clogging. The input data for modelling were obtained from studies conducted on experimental sites on objects constructed on a semi-technological scale. The experiment conducted has proven that the application of the model developed for the phase of water infiltration enables us to estimate the degree of module clogging. However, this method is more suitable for reservoirs embedded in more permeable soils than for those located in cohesive soils.

Rain garden hydrological performance - Responses to real rainfall events.

Rain gardens, as bioretention facilities belonging to blue-green infrastructure solutions, are becoming increasingly implemented in cities. The main reason for this is to support traditional drainage systems in receiving runoff from impermeable surfaces and managing it through temporary retention and infiltration into the ground. However, as practice shows, investors focusing on the construction of the systems and their commissioning skip their monitoring during the operating period, thus missing the opportunity to obtain reliable data on their hydrological performance under actual field conditions. The purpose of the study was to evaluate the effectiveness of a rain garden, located in an urban area, to capture runoff from the roof of a building. The assessment was based on the results of measurements carried out in 2021 on the variability of the levels of water retained in the rain garden and on measurements of growing medium moisture content at several selected points in the rain garden depression against thermal and rainfall conditions. The results showed that the rain garden demonstrated good hydrological performance. This was proven by the observed direct infiltration of rainwater into the structural layer or the short retention time for rainfall events with a higher rainfall total. The highest growing medium moisture was observed in the area of rainwater inflow to the rain garden. The results of the research may be useful in the planning and realization of future investments with rain gardens, which are to be situated in areas of similar meteorological conditions.