Thermophilic High Speed Treatment of Wastewater by a Novel Anaerobic UASB Reactor

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All practical-scale UASB processes constructed so far have adopted either mesophilic or ambient temperature conditions. There is at present no thermophilic UASB process in operation, except one demonstration-scale process. One of the main causes hindering the dissemination of thermophilic UASB process may be the difficulty or less reliability of granule formation, compared with mesophilic processes.In order to investigate the performance of new developed thermophilic UASB reactor and the behavior of methanogenic activities of the retained sludge, the laboratory-scale UASB reactor was operated approximately 2 years by feeding with an alcohol distilllery wast under thermophilic conditions (55ﾟC). The reactor was inoculated with mesophilically-grows granulated sludge harvested from an UASB reactor receiving a carbohydrate (mainly juice) waste water.The novel thermophilic UASB reactor having a multistage of gas solid separator resulted in a low SVI and good stability of retained granulated sludge. As a result of establishment of well-settleable, high-activity granuled sludge, the reactor allowed ultimately a volumetric organic loading of 100kgCOD/m3/day, with a COD removal efficiency of around 85-90%. Methanogenic activities of the retained sludge reached finally up to 2.9g COD/g VSS/d for acetate, 0.69g COD/g VSS/d for propionate, and 16.2g COD/g VSS/d for hydrogen. Low values of the propionate-fed methanogenic activity compared to other thermotrophic groups, indicate that the propinate breakdown is mostly subject to be a rate-limiting step in thermophilic methane fermentation process.