Financial Daily from THE HINDU group of publications
Wednesday, Jul 23, 2003
Financial Daily from THE HINDU group of publications Wednesday, Jul 23, 2003 |
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Industry & Economy
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Environment Anaerobic tech mooted for sewage treatment Vinson Kurian
Thiruvananthapuram , July 22 A WORLD Bank consultant associated with its India-related pollution control projects has proposed that integration of anaerobic technology at sewage treatment plants can lead to easy savings in energy consumption and sludge handling. According to the New Delhi-based Mr Stefan van den Hark, an expert on anaerobic technology, sludge management and membrane technology, an anaerobic pre-treatment unit can be integrated in the conventional activated sludge process. It can be seen that the BOD (biochemical oxygen demand, by which oxygen demanding substances are measured) and SS (suspended solids)-load that would normally be transferred directly to the aeration tank are considerably reduced in the anaerobic pre-treatment step. Savings in energy consumption and sludge handling are easily achieved in this manner. Mr Stefan proposed the new technology in a paper he is presenting at the National Conference on Biological Treatment of Wastewater and Waste Air (BTWWA) being hosted here by the Regional Research Laboratory-Thiruvananthapuram (RRL-T) next month as part of the silver jubilee of RRL institutions in the country. Anaerobic treatment of domestic wastewater is a broadly recognised technology for sustainable wastewater treatment. The technology has been successfully applied in several countries such as India, Columbia and Brazil. However, anaerobic treatment applications in India for domestic wastewater have until now been based on the concept of anaerobic treatment with a post-treatment step in the form of oxidation ponds or anaerobic lagoons. This configuration has proved to be sensitive, especially during the winter months, for not meeting the prescribed effluent standards. The application of anaerobic treatment in a stand-alone configuration also defies the concept of anaerobic technology. Anaerobic wastewater treatment is highly effective as a pre-treatment step but should always be followed up by a post treatment step in the form of activated sludge treatment. Reference is made to many successful industrial applications of anaerobic wastewater treatment, of which none are operating without a proper post-treatment step. However, the technology is not new, as it has been implemented in various treatment plants, including the 100-mld upflow anaerobic sludge blanket (UASB)-aeration treatment in Surat, Gujarat. In addition to the anaerobic pre-treatment step, it is proposed to withdraw sludge from the anaerobic reactor and pump it into sludge digesters, commonly used for mineralisation of activated sludge. The digested sludge from the digesters is used to replenish the sludge in the UASB reactor. By recirculating the sludge over the sludge digesters, a high level of sludge mineralisation, sludge activity and biogas production can be achieved.
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