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Sewage |
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Sewage waste is perhaps one of the more uniformly treated wastes, regardless of who it came from it is a mixture of organics, inorganics and water. The problem with this kind of waste is that it can be unpleasant, and dangerous (pathogens), the treatment therefore is to remove pathogens, and nutrients before it reaches the environment. Old sewerage systems, which treat the sewage before releasing it into the environment, may still be found on planets, especially in more rural locations as these methods are simpler, though widely it has become more sophisticated, some of these have been listed below.
The process of pyrolysis can be thought of fire without the fire, but does act in the sae respect to reduce compounds to simpler substances, and shares the same sterilising effect. Pyrolysis is the predominant sewage treatment in more technological locations, such as settlements, cities and spacecraft and asteroid complexes. Though pyrolysis requires energy, energy is readily available in these situations. The process is in effect quite simple, the raw sewage is emptied into a pressure vessel, and the vessel heated and injected with supercritical steam. Organic compounds spontaneously decay into simple inorganics (such as carbon dioxide and ammonia) under these high temperature conditions (in excess of 600’C), when the treatment is finished what remains is water, mostly clear apart from any inorganic grit or sand, and any gases generated, mostly carbon dioxide and hydrogen. These gases may be reintroduced into solution by photosynthetic bacterial cultures or consumed by plants, and the resulting fluid is suitable for hydroponics applications as the treated waste has been converted into a sterile solution containing all the salts and nutrients required for plant growth. The benefits of such a method are apparent when the sewage producing population is also dependent on hydroponic agriculture for their food, as the cycles are in effect neatly closed, for this reason this system is the practically the sole system used on asteroid colonies, as it frees the asteroid on having to import additional biomass. This system is also in Federation cities, as it offers not only solutions for agriculture, but also a hygienic way of disposing large amounts of waste without requiring large volumes to be standing about in sewerage tunnels. Typically a group of house, or an apartment block will have its own pyrolyser, though larger systems fed by sewerage pipes are also in place. The actual pyrolysis process can be made relatively efficient as the breakdown of organics in the solution liberates energy which is used to heat the vessel and generate the supercritical state, the only dangers are the high pressures involved, for these reasons small (and therefore easier to control) centralised pyrolysis units situated below ground in armoured reaction vessels are the preferred method. Pyrolysis is less often used on starships which have little in the way of hydroponics. Starships are unique in many ways, often because technologies developed elsewhere are simply insufficient for their demands. Sewage handling is another process that has fallen under new and interesting technologies at the hands of spacecraft designers. Starships often have very little in the way of organic material on board, and there is strict control over its use, it therefore demands a rapid process where waste can be quickly and efficiently converted back into the original building blocks, as this reduces not only the amount of equipment needed to store the waste material, but also reduces the total amount of organic material that needs to be carried. Pyrolysis (link) is often the first step of the process in larger starships in the treatment of sewage, but the relatively large volume of slightly impure water is energy intensive to separate back into elements, and so often there is a separate cycling of organic material and water. Sewage is first heat sterilised, often immediately after its production, (starship toilets have the same unnerving edge of toilets on trains and aircraft), the sewage is firstly treated by homogenising and flash sterilised by intense bursts of infra-red and UV. The sterile solution is then piped to an osmotic membrane unit where the majority of the water is separated. The separated water is effectively pure (as only water can pass through the separation membrane), these units use high pressure pumps to force water over the osmotic membranes and are used to typically reduce the sewage so that the organic and inorganic parts constitute some 20-30% of the volume, more is not removed as movement around the hardware is impeded if the sludge becomes any thicker. The sludge is then baked on a rotating surface and the condensed water is recirculated through the previous stage and recovered, the sludge is converted into a fine powder, this fine powder is then fed into a matter disassembler, a modified version of matter extraction technology. The fine powder is vaporised by using a fine plasma stream, and the resultant plasma separated into its constituent atoms by magnetic deflection (link: materials processing). The end product is that the powder is separated into its constituent atoms, which are then separately stored, gases are liquefied and pressurised, solids often kept as powders or blocks. The effect of the treatment is to disassemble the waste back into the fundamental building blocks, and therefore widen its application (in contrast with pyrolysis). This method is also used for other wastes and refuse. |
