DOSE OF LIME AND CHEMICAL CHARACTERISTICS OF LIMED SEWAGE SLUDGE

Abstract

The sewage sludge, after being sanitized with the addition of lime, can be used to correct soil acidity and improve fertility. However, little is known about the post-liming characteristics of sewage sludge. This work was done to define the dose of lime for hygienization of sludge generated during the primary treatment of domestic sewage, determine chemical characteristics after liming, and determine application rate for use in parks and gardens. The sludge was collected from sewage drying bed of treatment Plant José Cirilo, Muriaé, MG. After sieving (2 mm mesh) an incubation curve was generated by adding different doses (0, 25, 50, 100, 150, 200 and 250 kg m-3) of hydrated lime. The data revealed that to keep the pH slightly above 12 for more than 2 h, liming dose should be 43.20 kg m3 and if this pH is to be maintained for 72 h the application rate should be increased to 71.20 kg m-3. The sludge treated at the rate of 71.2 kg m-3, was subjected to nitric-perchloric digestion to quantify total N, P, K, Ca, Fe, Na, Mg, Cr, Ni, Cd, Pb, Cu, Mn and Zn. The values, in g kg-1, were 10.08 of N, 3.63 of P, 2.80 of K, 3.16 of Ca and 52.53 of Fe, while, in mg kg-1, 268.75 of Mg, 33.50 of Ni, 2.25 of Pb, 119.75 of Cu, 499.00 of Mn and 395.50 of Zn. The Cd and Cr were not detected.