Method for treating wastewater sludge

Abstract

A method for treating wastewater sludge which comprises the steps of further treating the sludges after they have been mixed with alkaline materials and are still in a wet condition with carbon dioxide containing gases wherein the carbon dioxide is a significant constituent for a time sufficient to reduce the pH below 10 and to prevent the emission of the ammonia nitrogen. Preferably heat is added to the mixture to accelerate the reaction and facilitate drying. The product is useful as an agricultural product. In a preferred process, the amount of alkaline materials being sufficient to raise the pH of the mixture to 12 or above and to heat the mixture by an exothermic reaction to a range of about 52.degree. C. to about 62.degree. C. and maintain the pH above 12 and the temperature range for a minimum of 12 hours to reduce significantly offensive odor of the sludge to a level that is tolerable; to reduce anumal viruses therein to less than one plaque forming unit per 5 grams dry weight of said sludge; to reduce pathogenic bacteria therein no less than three colony forming units per 5 grams dry weight of said sludge; to reduce parasites therein to less than one viable egg per 5 grams dry weight of said sludge; to retain a soil-like indigenous microflora; to reduce vector attraction to said sludge; and to prevent significant regrowth of the pathogenic microorganism; and thereafter subjecting the mixture to carbon dioxide containing gas wherein carbon dioxide is a significant constituent for a time sufficient to reduce the pH below 10 and to prevent the emission of the ammonia nitrogen.