Radon Exposure in the Underground Tourist Route-Historic Silver Mine in Tarnowskie Góry, Poland.

An assessment of the exposure of workers and tourists to radon in the underground tourist route of the Historic Silver Mine in Tarnowskie Góry was carried out. The study was conducted over a one-year period to capture seasonal variations in radon concentrations. CR-39 track detectors were used to measure radon concentrations, which were exposed in the mine during the following periods: 9 February 2021-19 May 2021, 19 May 2021-26 August 2021, 26 August 2021-25 November 2021 and 25 November 2021-3 March 2022. The annual average radon concentration along the tourist route was 1021 Bq m-3. The highest measured concentration was 2280 Bq m-3 and the lowest concentration was 80 Bq m-3. Based on the measured concentrations, effective doses were calculated, assuming that employees spend 1350 h a year in underground areas and that the time of visiting the mine by tourists is ca. 1 h. The average annual effective dose a worker would receive is approximately 2.5 mSv, and a tourist below 2 µSv. The dose limit expressed as the annual effective dose is 1 mSv for members of the general public and 20 mSv for occupational exposure.

Powdered Ceramsite and Powdered Limestone Use in Aerobic Granular Sludge Technology.

The effects of two powdered mineral materials (powdered ceramsite and powdered limestone) on aerobic granulation of sludge were evaluated. The experiment was conducted on a laboratory scale bioreactors treating wastewater for 89 days. Three granular sequencing batch reactors (GSBRs) were operated at the lowest optimal organic loading rate (OLR) of 2.55 g COD/(L∙d). In the control reactor (R1), the mean diameter (d) of the biomass ranged from 124.0 to 210.0 µm, and complete granulation was not achieved. However, complete granulation did occur in reactors to which either ceramsite (251.9 µm < d < 783.1 µm) or limestone (246.0 µm < d < 518.9 µm) was added. Both powdered materials served as a ballast for the sludge flocs making up the seed sludge. Ceramsite particles also acted as microcarriers of granule-forming biomass. The granules in the reactors with added powdered materials had nonfibrous and smoother surfaces. The reactor with ceramsite exhibited the highest average efficiencies for COD, total nitrogen, and total phosphorus removal (85.4 ± 5.4%, 56.6 ± 10.2%, and 56.8 ± 9.9%, respectively). By contrast, the average nitrification efficiency was 95.1 ± 12.8%.

The impact of powdered keramsite on activated sludge and wastewater treatment in a sequencing batch reactor.

As the efficiency of biological wastewater treatment in activated sludge systems can be increased if powdered mineral materials are added, the work described here investigated the effect of powdered keramsite on activated sludge and wastewater treatment in a sequencing batch reactor on the laboratory scale. Specifically, experiments were carried out on two sequencing batch reactors, with the reference system being the classical SBR with conventional activated sludge, while the second system involved a K-SBR (Keramsite - Sequencing Batch Reactor) with powdered keramsite added with a view to enhancing the effectiveness of the activated sludge. The concentration of powdered keramsite in the latter reactor was maintained at 0.75 g/L. The results confirmed the greater efficiency of biological wastewater treatment processes where activated sludge was supported by the keramsite.