| Summary: | The European Union stipulated in directive 91/271/EEC of 21st May 1991 that high nitrogen removal is expected for wastewater effluent of coastal cities with greater than 10,000 inhabitants. The nitrogen removal efficiency of the Luleå municipality (kommun) Uddebo wastewater treatment plant (WWTP) that process wastewater of 75,000 p.e was investigated. The wastewater effluent from the Uddebo plant which employ the trickling filter (TF) that operate at 13% removal efficiency was evaluated and a nitrogen mass balance on the whole wastewater processing was estimated yielding a nitrogen content of 874kg N/d as against the 374kg N/d stipulated by the EU. The result showed that the nitrogen content in the effluent is not satisfactory, it far exceeds the discharge limit, and further treatment techniques or technologies were needed to help Luleå municipality fulfil the effluent quality. Biological nitrogen reduction by bacteria involving two processes in sequence namely nitrification and denitrification forms the basis for high nitrogen removal from wastewater. In theory, the nitrogen in the wastewater would be converted to nitrogen gas. A wide range of treatment processes and alternatives were discussed. After careful evaluation of all available treatment technologies and options, three were identified as the best suited for Luleå municipality: upgrading to a moving bed biofilm reactor (MBBR), using wetlands for some part of the municipality wastewater, and using urine diversion system for part of Luleå city wastewater. For a better effluent result, the options were grouped into four alternatives which include: (1) Upgrading the Uddebo plant to MBBR (2) Constructed wetlands for areas with 1,000 or fewer inhabitants plus MBBR for remaining municipal wastewater (3) Urine diversion for part of Luleå city plus MBBR for the remaining wastewater (4) Mixed wastewater treatment system with wetlands, urine diversion and MBBR process. A detailed evaluation of the alternatives was done based on efficiency, reliability and ...
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