Ορθολογική περιβαλλοντική διαχείριση αστικών λυμάτων

Abstract

Orthological environmental management of urban wastewater in a thorough biological treatment plant demands the combinatory study and evaluation of various parameters, the most important of which are: - The quantity and the quality of untreated wastewater - The environmental status of the final receiver of the treated wastewater (eutrophication phenomenon) - The required wastewater treatment - The possible alternative methods for the further utilization of the plant's final products - The current legislative status of each stage of the plant's design. So far, the biological treatment plants in Greece have been designed and constructed based on the treatment required and only. No such a plant in Greece has ever been designed based on all the above criteria. This fact has been the motive for this dissertation. The Psyttalia Wastewater Treatment Plant (PWSP) has been selected as a case study, because it arises to be the largest (it is designed to treat the quantity of 1.000.000 m3 of wastewater per day), the most important of its type in Greece and it is so long under construction. It treats the wastewater of the Metropolitan area of Athens. The PWSP is in Akrokeramos of Keratsini area (pretreatment units) and on Psyttalia Island (basic treatment units). Psyttalia Island is a tiny island in Saronikos gulf between Piraeus and Salamina Island. Except for the urban wastewater, toxic sewage from factories at a percentage of 20% of total wastewater also end up in the PWSP. The population of the area served by the sewerage network is estimated to be about 3.300.000 inhabitants at the total amount of 3.600.000. The total sewerage covers an area of 5.700 Km approximately. Though the primary treatment units (A' Phase project) have been constructed since 1994 and are in operation, the secondary treatment units - biological treatment, is under construction and it is estimated to be ready to operate by the end of 2003. A' phase project has been constructed in the period 1988-1994 and provides the primary treatment of the wastewater as well as the treatment of the sludge produced by the primary settlement tanks (anaerobic digestion and dewatering). Treated effluents end up in Saronikos gulf and more precisely on the marine area of Akrokeramos in Keratsini at a depth of 65 m through submarine pipes. The dewatered sludge ends up at the dump of Ano Liosia area. The B' phase project, constitutes the sequence of that one of A' phase. The construction of this project has been commenced in 1999 end is estimated to be finished at the end of 2003. It will provide the secondary treatment of the wastewater as well as the removal of nitrogen in accordance to 91/271/E.C. Directive for sensitive receivers. Inner Saronikos Gulf has been recently characterized, via Greek law, as to be a sensitive receiver. Drastically reduced pollution loading of b' phase effluents will undoubtedly improve the environmental status of Saronikos gulf. Nevertheless, the removal of phosphorus also should be considered since it \s not scientifically proved that…