From a global perspective, drought is a well-known manifestation of climate change. The search for alternative sources of water also brings uncertainties and risks, for example, in relation to wastewater irrigation. We asked ourselves whether and how supplemental irrigation with pre-treated wastewater would affect the subsoil or groundwater quality. We constructed semi-operational models that were loaded with wastewater in a controlled manner over three years of observations. Ammonium nitrogen (NH₄⁺-N) pollution is one of the monitored parameters in wastewater discharge. In specific situations and under strict operating conditions, it can be assumed that ammonia nitrogen may not be a significant problem for groundwater. Already at a depth of 0.5 m below ground level, the average nitrogen levels are below 0.02 mg/L at an irrigation rate of approximately 15.5 mm/day. When monitoring total phosphorus (TP), these values are reduced with more variability—depending on the plant species at the surface, ranging from 0.17 to 0.95 mg/L. The measured values are used to calibrate the numerical model, or to determine the reaction parameters that enter the governing equation to describe the distribution of the solution in the soil environment. The results show an acceptable compliance between the model and real measurements, it will be possible to use them in practice for the design of wastewater irrigation systems.

As the planet-s population increases, pollution entering waterways increases, and the availability of non-renewable raw resource materials reduces. It is possible to reduce this pollution by constructing treatment wetlands, but these wetlands use significant amounts of natural aggregates. The question arises: is it not possible to replace non-renewable resources with recycled materials made from construction and demolition waste? This article examines the applicability of recycled building materials as filter media for vertical subsurface flow filters. The recycled aggregates of the 0-4 mm fraction are evaluated in terms of grain size and hydraulic conductivity. For the Czech Republic-s available raw recycled aggregates, washing methods are proposed to produce materials that meet the required grain size limits. Untreated aggregates contain a significant proportion of particles smaller than 0.063 mm (up to 21.8%), significantly reducing their hydraulic conductivity and preventing their use in water filtration. However, concrete and masonry aggregates with dust particle contents of 0.3% and 1.5% can be obtained through washing. The washed materials subsequently show an increase in hydraulic conductivity up to the required range of values, that is 10?4-10?3 m s?1. According to the evaluation carried out, it is possible to apply treated recycled materials to wastewater filtration. At the same time, the application of construction waste in constructed treatment wetlands creates opportunities to use fine recycled aggregates (0-4 mm) in these areas, which are currently limited, in the future.

The sludge layer formed during the first stage of French vertical flow constructed wetlands is a crucial component in achieving high removal efficiencies of water pollution, including suspended solids, chemical oxygen demand, nitrogen, and phosphorus. In the Czech Republic, persistent challenges with insufficient sludge layer development on the first stage have limited treatment performance due to the combined sewerage system. To address this, a pilot-scale experiment was conducted focusing exclusively on the formation of the sludge layer necessary for effective pollutant removal. This study determined and compared the saturated hydraulic conductivity (ks) of the sludge layer developing on the surface of the first stage of French system. Three measurement campaigns were performed: (i) on mineralized sludge of varying thicknesses, (ii) on primary sludge with and without an artificial grass layer, and (iii) on primary sludge with and without a geotextile layer. Saturated hydraulic conductivity was measured using a double-ring infiltrometer during an eight-day resting period. Results showed a strong dependence of ks on sludge thickness (8 cm: 1.7 10-4 m s-1; 5 cm: 8.6 10-4 m s-1; 3.8 cm: 1.3 10-3 m s-1). The grass layer on primary sludge initially reduced ks to 1.1 10-5 m s-1 compared to 5.7 10-5 m s-1 in the control, while the geotextile led to lower initial ks and slower conductivity increase over time. These findings confirm that sludge thickness and artificial modifications fundamentally influence the hydraulic behaviour of filter beds and can help optimize French system operation.