Exploring Stabilization Alternatives for a Lime-Softening Sludge with a High Organic Content

Stabilization of the sludge originating from a water treatment plant, where a lime‐soda softening of the creek water containing a high organic matter is employed, was investigated. Several stabilization alternatives, namely, aerobic stabilization, acid stabilization, base stabilization, lime stabilization and thermal stabilization were tested. Thermal stabilization outperformed among the others. It was observed that exposing the sludge to at least 375°C would render the sludge disposable into non‐ hazardous waste landfills. Aerobic stabilization did not work at all. Acid, base and lime stabilization processes, though resulted in the organic content decrease from 6 to 9% in the sludge, could not satisfy the leachate organic content criteria of 80 mg L‐1 DOC, since, probably, the organic matters in the sludge became less adsorbable to the sludge and, hence, more leachable to the bulk solution