Perdas de vazão e seus efeitos na operação do sistema de esgotamento sanitário de Campina Grande-PB.

Abstract

Studies on both estimation and variation of flow rates are of fundamental importance in designing and operating urban sewerage systems because the size of pipes and equipment as well as the functioning of their units are dependent of such a factor. This study aimed the identification of wastewater diversion points of the sewerage system of Campina Grande City, Paraiba state, northeast Brazil, mainly for reuse in agriculture. Also, the decreasing of flow rates and their effects on the operation of the sewerage system were evaluated. The study was developed in points of two interceptor pipes and of the final pipeline of the system mainly along periurban areas of Campina Grande. Points with illegal withdrawal of sewage were registered, as well as points considered vulnerable to such a type of practice. Water heights measured in Parshall flume at the entrance of the Sewage Treatment Plant of Catingueira, measured hourly were used to study the variation of contribution of sewage over four years (2009, 2010, 2011 and 2012). Analysis of variance of one factor, at a level of significance of 5%, was applied for comparing hourly flow-rate means obtained along the four years studied. ANOVA results demonstrated significant differences amongst the means, being that of 2012 significantly less than those of preceding years. This reduction was attributed to the diversion of wastewater mainly used for irrigation of grass in periurban areas. Such a practice is dangerous for both health and environment and injurious to the physical structure of the system as pipelines are frequently broken to facilitate the wastewater withdrawal.