Remoção de coliformes fecais e matéria orgânica em um reservatório profundo de estabilização tratando águas residuárias domésticas.

Abstract

The increase of both population and water per capita rate, particularly in urban areas of developing countries, has demanded increasing volumes of water. Besides, many water sources are unsuitable for use due pollution. In many parts of the world people have problems with water supply and many face scarcity. Nowadays there is a global concern about the necessity of adopting water resources management programs, including reuse of effluents. Wastewater storage and treatment reservoirs (WSTR) could be a low cost alternative for sewage treatment. WSTR are easily operated and besides they may produce a suitable effluent for agricultural irrigation. These reactors were firstly conceived in Israel in the early 1970s and nowadays are used in many countries, particularly in arid and semiarid regions, where climate favours their operation. Since 1994, EXTRABES (Experimental Station for Biologically Treating Sanitary Sewage) have been studying WSTR treating domestic wastewater in northeast Brazil, aiming to obtain regional design parameters and better operational strategies. This work describes the removal of both faecal coliform and organic matter in a WSTR (RE-3) investigated at EXTRABES, emphasizing the aspect of their kinetics. The 6.95 m deep pilotscale RE-3 was fed with raw sewage and operated as a batch reactor, during two different experimental periods (27/09/94-08/03/94 and 15/03/95-22/05/95) under distinct operational characteristics. After filling, the reservoir was allowed to rest until faecal coliform numbers decreased down to less than 100 cfu/100 ml in the water column. Faecal coliform, BOD5, COD, suspended solids, total alkalinity, pH, temperature, dissolved oxygen and chlorophyll a were measured throughout the water column during the whole experiments. RE-3 was shown efficient in both faecal coliform and BOD5 removal being these reductions time dependent and their velocities influenced by factors associated to the operational conditions, mainly organic loading which was found to be the most characterist parameter in the operation of the reservoir.