Study of the Simultaneous Elimination of Phosphates and Heavy Metals Contained In Dairy Wastewater by A Physical-Chemical and Biological Mixed Process;; Consequences on the Biodegradability.

摘要

The study examines the influence of the presence of heavy metals presence on the elimination of phosphates in dairy wastewater. It focuses on the phosphates precipitation in a stoichiometric dose of ferric chloride and is made of two main parts:-Without contribution of heavy metals.-With contribution of heavy metals (lead and cadmium). In both parts, the removal was carried out at first in a physical-chemical way by the precipitation of phosphates with ferric chloride;; the residual phosphates concentrations were then biologically eliminated by activated sludge taken from an urban wastewater treatment plant. For the tests conducted with heavy metals presence, lead and cadmium concentrations between (10 and 100 mg / L) were added to the wastewater kept for our study. The main results show:-Good phosphate precipitation with the use of ferric chloride.-The combination of biological and physical-chemical processes is possible since a removal of 69% in presence of Lead (Pb) and 93% in presence of Cadmium (Cd) were obtained.-Maximum removals of 100% lead (for 100 mg / L of Pb) and 94% cadmium (for 50 mg / L of Cd) were obtained after phosphates precipitation by the ferric chloride. Moreover, in an attempt to assess the performance of the biological treatment by activated sludge combined to the physical-chemical process on the removal of heavy metals in the water to be treated. The evolution of the Cadmium's concentration according to time was followed in both supernatant and sludge. This was made possible by a kinetic study in batch. In this case, the results show: Cadmium removal from about 81% in the supernatant. Good retention of cadmium in the sludge. The synthesis of all the results obtained during this study shows that the combination of physical-chemical and biological processes improves the removal of phosphates in the absence and presence of heavy metals.