Caracterização das perdas no sistema de abastecimento d'água do município de Queimadas-Paraíba.

Abstract

This work estimates the real and apparent water losses in the distribution system of the city of Queimadas, PB, using two methods of estimation. The city of Queimadas, PB, is located in the "Cariri" geographical region of the state. The city is located 138 kilometers from the state capital of Joao Pessoa and 14 kilometers south of the city of Campina Grande. The city has a population of about 36,032 inhabitants, according to the federal census taken in 2000. The historical data for the water system was supplied by CAGEPA. The data covers the year of 2003 January to December. Three different areas for measurement, described as "sectors", were established for study. The first with 124 (one hundred and twenty-four) users, the second with 424 (four hundred and twenty-four) users, and the last with 299 (two hundred and ninety nine) users connected to the ZPR-1 distribution zone, supplied by the R-l reservoir which Is responsible for 78.53 % of the distribution to the city. A Woltmann meter was installed to take measurements over three different weeks in order to monitor the minimum night flow from 3:00 AM to 4:00 AM over a period of six days, as well as a measurement of line pressure using a paper disc registration device which registered the pressure in each sector over a 24 (Twenty-four) hour period within three distinct and separate weeks. The first method used for arriving at the estimates consisted of applying a NDF (Night-Day Factor) to the minimum night flow data collected In each sector in order to estimate the real treated water loss. The results for NDF fit within the expected range for systems, that provide water for homes with home water storage systems, which is 24 hours or less. The pressure measurements was within the range prescribed by the Technical Norm NBR - NM - 12218 of the ABNT In order to arrive at an estimate of the real and apparent water losses from the distribution system as a whole, computations were made of the average of the daily losses from the three sectors proportionally to the total number of connections of the system in each month of the year. The second method of estimation used formulas in which parameters obtained from figures available in specialized publications were used in order to estimate the apparent loss, calculating the real loss for each month of 2003, against total lost water volume. The distribution system studied demonstrated precarious conditions in both its physical state and its operational control, which will require improvements In order to, more accurately, estimate real and apparent treated water loss in the future. Residential usage represents 96.45 % of the connections within the distribution system. The average loss index for the system Is about 38.78 % of the total volume of treated water produced for the system. The index for loss using the night flow data method was 44.31 % and 55.69 % respectively, while the estimate arrived at using the EMBASA's method was 41.43 % and 58.57 % respectively, demonstrating the compatibility of the two methods applied. The apparent losses were significantly higher that the real losses. The total volume of treated water lost from the system represented a revenue loss of 59.55 % when compared to annual income figures for 2003 published by the treated water providor, CAGEPA In the system of Queimadas.