Implicaciones sobre la estación depuradora de la gestión de aguas pluviales en los sistemas de saneamiento unitarioestrategias de integración y afecciones sobre procesos

Abstract

New designs and strategies to manage wet weather flows in combined sewer systems, which main objective is to minimize environmental impacts on water bodies, require the treatment of large volumes of stormwater. Wet weather flows introduced into combined sewer show dynamic-transient behavior both in terms of flow discharges and pollution. With traditional design strategies, large pollution peaks are spilled during rain events into water receiving bodies by combined sewer overflows (CSOs). Nowadays, CSOs have been reduced providing some storage capacity into the combined sewer systems (either in network, by means stormwater tanks, or in WWTP). The stored stormwater and its associated pollution should be treated. WWTP inflows during rainy events are conditioned by the local stormwater management strategy. The WWTP can be overcome if it is managed using traditional dry weather strategies. In order to optimize the treatment performance and to assure that urban pollution do not reach aquatic environment, the WWTP must participate in the system in an integrated manner. This is a key element. This paper shows firstly the importance of CSO pollution and the development of new strategies for stormwater management in combined sewer systems. Stormwater tanks, located in the sewerage system, have been one of the most common solutions adopted but there are some experiences of wet weather flow management at the WWTP. All these strategies are revised in the paper. Once the role of the WWTP in the new combined sewer systems is known, the article presents a review about the problems generated by the hydraulics overloads and the large variations of the pollution characteristics on different stages of the water line. Special emphasis is made on the problems generated in secondary processes based on activated sludge. These problems are analyzed in detail and some mitigation strategies are proposed.