Sludge Ash Bricks Fired to above and below Ash‐Vitrifying Temperature

The City of Indianapolis' Belmont Advanced Wastewater Treatment Facility produces 32 dry metric tonnes per day of ash from incineration of municipal sewage sludge. Available capacity at the existing ash disposal site is limited. To determine the feasibility of an alternate disposal method, a bench‐scale study was conducted to determine the physical characteristics of bricks produced at four ratios of clay content to ash content and fired to temperatures above and below the vitrification temperature of the ash. The bricks were assessed for drying weight change and shrinkage, firing weight change and shrinkage, total weight change and shrinkage, density before and after firing, compressive strength, water absorption, freeze‐thaw resistance, and tendency to leach metals during acid extraction (“EP‐Tox”). The use of sewage sludge ash as an admixture in brick appeared to be promising, especially when the ash amended bricks were fired to above ash vitrification temperature. The City of Indianapolis and an Indianapolis‐area brickmaker are preparing for a full‐scale demonstration run; the parent company of the brick maker advanced to full‐scale ash brick production, using ash from another major city.