Strategies for upgrading primary facultative ponds in Fortaleza, Northeast Brazil

Abstract

During the last two decades waste stabilization ponds had a considerable advance in Brazil. In parallel, the evolution of this technology was accompanied by an increasing restrictive environmental regulation with regard to effluent standards. Thus, old plants comprised basically by single primary facultative ponds do not meet new stringent demands. The present paper deals with upgrading alternatives for six full-scale pond systems located at Fortaleza (38o 32' W; 3o 43' S), northeast Brazil. For each plant six different arrangements were considered with the inclusion of anaerobic reactors and maturation ponds. In three of them a polishing filter was considered. For those without a polishing filter the removal of unfiltered BOD and COD would reach 84 and 79%, respectively. For filtered samples the performance would increase to 95 and 91%, respectively. For the new arrangements with a polishing filter the performance would be 92 and 90% for BOD and COD, respectively. On average faecal coliform removal would rise from 1.362 logs in primary facultative ponds to 3.916 logs in the new plant schemes.