Evaluating the effectiveness of lime-based filter-media on sewer air hydrogen sulphide

The formation and release of odorous gasses such as hydrogen sulphide from sewer systems have intensified over the last years concurrently with the centralisation of wastewater treatment plants (Hvitved-Jacobsen et al., 2013). Hydrogen sulphide is toxic at low concentrations, and the formation of hydrogen sulphide can result in high cost for rehabilitation and maintenance following biogenic concrete corrosion. Different technologies are applied to prevent hydrogen sulphide emissions where injecting chemicals to either prevent the formation or remove formed sulphide are among the most common ones (Hvitved-Jacobsen et al., 2013). However, the European Parliament has expressed support for the employment of nature-based solutions due to the politic aim for a more sustainable society. Therefore, this paper's underlying theme focuses on a full-scale technical plant based on biological hydrogen sulphide treatment in Aarhus, Denmark.

The plant receives air discharge from a sewer system that is then neutralised by mussel shell, which functions as a lime-based filter medium. This technology uses the same bacteria that cause hydrogen sulphides corrosion in sewers but moves the process from the concrete assets and over to the filter medium. This paper takes its onset in the full-scale facility design and uses the loadings and experiences to demonstrate the effectiveness of different lime-based filter media on hydrogen sulphide through an experimental column setup. The different lime-based filter media used in this setup are mussel shells, chalk pellets, crushed concrete and lava stone. The removal rate of hydrogen sulphide in each filter medium is investigated, and each filter medium's functionality is assessed. Hydrogen sulphide is injected in the inlet in concentrations of 50 ppm, 100 ppm, 350 ppm and 750 ppm to simulate various scenarios. When hydrogen sulphide reacts with the lime-based mediums, gypsum is created. The columns are therefore flushed with water comparable to the watering system in the technical plant. A hydrogen sulphide sensor is installed to monitor the columns' hydrogen sulphide transformation.

The experimental setup results are finally compared to what is achieved at the full-scale facility in Aarhus, presenting data from both systems.