Tratamento de águas residuárias da bacia de sedimentação com uso de um sistema combinado de reatores anaeróbio e aeróbio em uma fazenda de carcinicultura no Município de Aracatí - CE

Abstract

Shrimp farming has been increasing in Brazil, especially in Ceará state, due to the high economic returns, suitable environmental conditions, high productivity and easy adaptation of Litopenaeus vannamei. However, the shrimp cultivation has been blamed for many environmental impacts, whose the extent and magnitude can vary according to the size of the undertaking, cultivation methods, water consumption, and production and processes of the effluent treatment. The research aimed to evaluate the application of the combined system of UASB - FSA reactors operated on a pilot scale for the treatment of the effluents from the sedimentation basin generated from the fishing and recirculation in shrimp farms in order to achieve the launch and reuse quality standards. This study was developed in a farm located in Aracati, Ceará state, and monitored the stages of biological treatment from the physical, chemical and bacteriological parameters of effluents stored in a sedimentation basin in order to know the characteristics of that wastewater and contribute to sustainability of that fishing activity. The starting of the UASB reactor was held with the formation of its own biological sludge and a flow rate of 60 L/h for a 60-day period. The biological system was monitored from January to July 2012, with a full flow of 120 L/h. The hydraulic retention time (HRT) used for operation of the UASB reactor was approximately 28.1 hours, while 19.8 hours for the FSA one and 8.3 hours for the internal secondary decanter. The aerobic reactor was filled with half support of HDPE model MSS 265, which has a surface area of 265m2/m3. The results obtained for removal efficiency of concentrations of nutrients, and organic and bacteriological material showed percentages of 64.66 % of COD, 74.05 % of BOD5, 61.31 % of total ammonia, 33.33 % of nitrite, 28.74 % of total phosphorus, except for the parameter of nitrate, registering an increase of 29.63 %. The fractions of suspended solids(SS) showed the best removal efficiencies, been confirmed a percentage of 70.69 % for total suspended solids(TSS), 85.81 % of fixed suspended solids(SSF) and 63.40 % of volatile suspended solids (VSS). The biological system was also quite efficient for the removal of parameters of perceived colors and turbidity, with the overall results of 87.82 % and 87.76 %, respectively. Regarding the parameters related to the pigments contained in the treated wastewater, the system achieved a removal of 98.03 % of chlorophyll a and 90.48 % for pheophytin a. Based on microbiological monitoring, the combined system of UASB-FSA reactors was able to remove 61.08 % of total coliforms(TC) and 93.22 % of faecal coliform (FC). Therefore, the results obtained in this study allow the discharge of treated wastewater in the receiving bodies, enable the proposal to reuse it in the farm to fill the ponds of shrimp farming, promote savings of water catchment and induce better management of water resources, especially in regions which suffer from limitations of water.