UP-FLOW ROUGHING FILTRATION - REHABILITATION OF A WATER-TREATMENT PLANT IN TARATA, BOLIVIA

This paper presents the methodology used for the rehabilitation of the pretreatment stage in a water treatment plant for a village located i n Bolivia which has 3500 inhabitants. The treatment plant was initiall y composed by horizontal-flow roughing filters and slow sand filters. but due to the high contents of colloidal turbidity of the providing s ource, it did not work properly. A plan of rehabilitation was made whi ch comprised laboratory tests, pilot tests and proposal of modificatio ns based on the results of previous stages. The laboratory tests were made in order to find the optimum conditions to coagulate the raw wate r. It was found that horizontal-flow roughing filters must be turned i nto up-flow roughing filters, so a pilot plant was built and was opera ted for three months in order to find suitable design parameters. The results obtained obtained during the operation of the pilot plant and the proposal of modifications are presented. The results of operation of the final plant, which are also reported. demonstrated the advantag es of the up-flow roughing filtration as a pretreatment stage when it is neccesary to add chemical products in small treatment plants. (C) 1 998 IAWQ. Published by Elsevier Science Ltd.