Calibração e monitoramento do desempenho da estação de tratamento de água da Vila de Murrupula

Abstract

This work presents the results of monitoring the performance of a Water Treatment Station (WTS) for consumption recently built in Murrupula village, Nampula province as part of the construction project of the Water Supply System in that village. The respective WTS is based on the double direct filtration model, comprising two production lines scaled for a production flow rate of approximately 90m3/d and comprising the following unit processes: (1) inlet chamber; (2) coagulation; (3) upflow prefiltration with hydraulic flocculation; (4) slow downward filtration and (5) disinfection. The work carried out included the assessment particularly of the conformity of the operational parameters with those established in the design phase and, in general, the conformity of the qualitative parameters with the quality standards established for drinking water according to the Law no. 16/91, from August 3rd, Water Law and the Presidential Decree no. 11/95, from December 29th. The overall average turbidity removal was between 42 – 98% (for the period in service). The removal efficiency in the upflow filter was around 55,0 – 57,8%, and in the slow sand filter around -6,2 – 78,1% (both in the start-up period). Both units operated by gravity, with filtration rates of around 0,55 – 0,8m/h for the pre-filters and 0,22 a 0,27m/h for the slow filters. Regardless of the operating conditions, there was a need to establish G values between 20 – 70s-1 in the upflow filter, providing hydraulic flocculation. The best performances were achieved during the service period, where turbidity, pH and residual chlorine values respected the permissible limits, without the need for alum intervention for coagulation or regulation of filtration rates. In general, the URFL and SSF had a great improvement in performance starting from the transition from the start-up period to the in-service period, guaranteed by the regeneration of the filter beds, well-delivered sizing flows in the units, satisfactory dosage of alum and chlorine, and turbidities tributaries to the SSF in accordance with its permissible limit.