Effectiveness of Various Sludge Stabilization and Solidification Methods

Abstract

If sludge contaminated with heavy metals is not properly treated, water flowing over the sludge can cause the heavy metals in it to leach out, polluting groundwater. To establish an effective means of dealing with this problem, the engineering applicability and stability of sludge solidified using portland cement (A1), a gypsum-type agent (B1), a cement Type I agent (A2), and a cement Type II agent (B2) were studied. The sludge was obtained from Keelung River. After the treated sludge had cured for 7, 14, 28, and 60 days, each sample was tested to ascertain its compressive strength and the rate at which six different hazardous heavy metals leached out. This was done to evaluate the feasibility of sludge solidification. The findings indicate that the ratio at which the solidifying agent is used determines the strength of the treated sludge. No significant improvement was found when the treatment agent was used at rates of less than 10 percent. Except for the A1 agent, marked improvement was observed for all types of solidifying agents except when the amount of additive was increased to 20 percent. The heavy-metal leaching rate of treated specimens met the requirements of the pollution control regulations, indicating that hazardous heavy metals had been effectively fixed within the sludge. Therefore, solidifying agents comprise an effective and feasible method of solidifying and stabilizing Keelung riverbed sludge.