Sacrificial pipe – A practical marble sacrificeLena Heldgaard Pind Jensen2023-03-10T20:45:46+01:00 Sacrificial pipe – A practical marble sacrificeWhen wastewater remains for a long period of time in a sewage system, hydrogen sulphide may form. Artelia has participated in the development of the “sacrificial pipe” concept that can neutralise the toxic and destructive gas. The EU’s Framework Directive on Water has entailed a centralisation of wastewater treatment, while stipulating requirements for the drainage of open land. This means that wastewater will increasingly have to be transported over longer distances, and the oxygen in the wastewater will be depleted. The same phenomenon can be seen in holiday areas, where the wastewater remains for a long period of time and depletes the oxygen in the water. The oxygen-deficient environment provides fertile grounds for the development of the toxic gas hydrogen sulphide, which has a distinctive smell of rotten eggs and can be a health hazard. Measurements taken in Danish sewage pipes show a concentration of hydrogen sulphide of up to 1,000 ppm, which represents a life-threatening inhalation dose. Once this limit has been surpassed, there is no alarm signal either, since hydrogen sulphide can no longer be smelled at such high concentrations. The aggressive hydrogen sulphide also corrodes sewer pipes, structures, technical installations and pumps. It even inhibits the processes at the treatment plants. To date, attempts have been made to tackle the hydrogen sulphide problem by adding chemicals to the wastewater or by blowing air into the pressure line. Common to both these methods is the fact that the operating costs are very high, and the use of chemicals is obviously an environ-mentally hazardous solution. This is therefore both a financial and health problem, and so-called sacrificial pipes may be the answer to these challenges. Pipes attacked by hydrogen sulphide Sacrificial pipe Why use sacrificial pipes? As the name suggests, a sacrificial pipe is a section of pipe that is “sacrificed”. The pipe consists of a concrete mixture that can neutralise the hydrogen sulphide, at the same time as the concrete degrades during the process. Marble is one of the important ingredients, since a high lime content strengthens the alkaline properties of the concrete. The lime forms an intermediate product, gypsum, which helps neutralise the hydrogen sulphide. The section of pipe is generally installed as an extension to a pumping well at the end of a pressure line. The sacrificial pipe also has a strategic position on the section, which is based both on measurement of the concentration of hydrogen sulphide and more practical considerations. In order for the solution to be profitable, it must be easy both to install and to dig up again at a later time. Artelia was part of the research team that developed the concept. We have subsequently tested the solution in practice with great success, and we have sections where we can measure a 99 % reduction of the concentration from the inlet to the outlet.
