Pós-tratamento de efluente anaeróbio em lagoa de polimento

Abstract

The domestic sewage treatment in UASBs reactors followed by polishing pond is a sustainable alternative, especially to the northeast of Brazil. Therefore, the present study applied polishing ponds as anaerobic effluent post-treatment. Two treatment systems were constructed and operated: 1) compact station (UASB reactor with intermittent flow sand filter) followed by two 0.18 m deep shallow polishing ponds; 2) UASB reactor followed by two polishing ponds with different hydraulic systems (batch and continuous) and same depth (0.60 m). At system 1, at experimental conditions, with low organic concentration (87 mgO2.L -1 filtered COD and 49 mgSSV.L -1 ), high sunlight incidence (597 Wm ), high temperature (20 to 30 ºC) and carbon dioxide biological consumption sufficient to raise the average pH units; the pond 1, feed with the aerobic effluent from the compact system, reached a 9.6 pH and provided an average removal of 86% of the total kjeldahl nitrogen, 82% of total phosphorus and 88% ortho-phosphate and coliform less than 1000 UFC.100ml

meeting the requirements of WHO (2006) for unrestricted irrigation. Also at system 1, the pond 2, feed with the anaerobic effluent from the compact system, reached a 8.6 pH and removed 80% NTK-N, 53% of total phosphorus and 44% ortho-phosphate, but did not obtain coliform final average less than 1000 UFC.100ml -1 . Both the 0.60 m deep ponds, 9 days batch and 12 days continuous hydraulic systems, achieved low nutrients removal and poor coliform efficiency, 96,85 and 97,21 %, equivalent to only two log units. Also achieved a negligible removal efficiency for both total phosphorus (efficiency <2%) and for ortho-phosphate (efficiency <25%); the NTK-N removal, compared to the ponds of 0.18 m were inefficient average values, 55% and 68% for PP3 and PP4 respectively.