Prospectus of waste stabilization ponds in Ceará, Northeast Brazil

WSP technology has been used in Ceará, Northeast Brazil, since middle 1970s. There are presently 96 ponds plants and most of them are comprised by single cells (40%) and series of 3 ponds (35%). They were under loaded due to incomplete house connections to the sewerage network and low per capita wastewater contributions. Highest removal rates of organic material, ammonia and faecal coliform were found in 3 pond series. Faecal coliform removal was in accordance with the literature and series of ponds reached numbers ≤10⁵ cells/100 ml. In series with 4 and 5 ponds FC was below 10³ cells/100 ml. Ammonia removal varied from 30 to 80% and total phosphorus the removal was not significant. An increase in the number of maturation ponds enhances nutrient and coliform removal. Up-grading schemes should be investigated as well as effluent reuse potential.