Avaliação da eficiência do processo físico-químico com cal no tratamento de águas residuárias domésticas.

Abstract

The experimental stage of the present work was carried out from 28,11,90 to 05/20/91 in a pilot system of physical-chemical treatment located in the Experimental Station of Biological Treatment of Sanitary Sewers - EXTRABES. The objective of the research was to verify the validity of the application of physicochemical system with lime for the treatment of domestic wastewater. In the experiments, calcium hydroxide [Ca (OH) 2] was used to raise the pH of the raw wastewater to the high pH range 11.0 and 11.5). With this, the reactions of flocculation and precipitation were intensified, and sedimentation was achieved by the clarification of raw wastewater. The best experimental results were obtained with the hydraulic holding time of 12 hours in the unit of sedimentation, and 35 hours in the refueling unit, when the best effluents were observed in terms of physico-chemical and bacteriological parameters. During the experiments the calcium hydroxide consumption was verified in relation to the volume of treated sewage, the volume of sludge produced and the pH value of the effluent of the system. The research made it possible to conclude that the physical-chemical treatment presents as a drawback a large production of sludge and a high pH of the effluent. However, it is efficient in the removal of suspended solids, turbidity, COD, total and soluble phosphorus C, and in the reduction of fecal coliforms. Its application is recommended in places with little area for facilities and / or when high efficiency in the removal of the phosphorus present in the raw waste water is desired.