Nutrient removal and sludge production in the coagulation–flocculation process

Nutrient removal and sludge production in the coagulation–flocculation process, applied to a slaughterhouse effluent, have been studied. Fe2(SO4)3, Al2(SO4)3 and polyaluminium chloride were used as coagulants. Inorganic products were used as coagulant aids: activated silica, powdered activated carbon and precipitated calcium carbonate and synthetic polyelectrolytes: cationic polyacrylamide, polyacrilic acid, anionic polyacrylamide and polyvinyl alcohol. Performances were measured under optimum conditions for the products used. They were found after studying the different variables which influence the process. Phosphorus removal is very high (≈100% for the orthophosphate and between 98.93% and 99.90% for the total phosphorus). Ammonia nitrogen removal is very low although appreciable performances are observed for albuminoid nitrogen (73.9–88.77%). The use of coagulant aids reduces the volume of the sludge produced up to 41.6%.