Factory-scale proving trials using combined mixtures of three by-product wastes (including incinerated sewage sludge ash) in clay building bricks

This paper reports the results of a series of factory trials which has been recently completed involving Staffordshire University, a major United Kingdom water company and a commercial brick manufacturer, which demonstrate the practical possibilities of incorporating three by-product wastes, waterworks sludge, incinerated sewage sludge ash and carpet yarn, into the commercial brick-manufacturing process as a sustainable alternative to their current disposal route of landfill. An initial laboratory development programme primarily involving waterworks sludge or water treatment residue (WTR) confirmed the technical feasibility of its use in brick-making as an alternative disposal route. However, owing to the very high water content of this waste when freshly produced, ranging between 85 and 70% depending on individual sources, its introduction into the commercial brick-making processes was identified as likely to present practical difficulties. Consequently, to overcome this problem the reported work describes a successful way in which the handling of WTR was improved by pre-mixing it with the two other by-products that jointly possess water-absorbing properties and the ability of improving the unfired strength of the experimental products. This investigation then progressed from the laboratory to full-scale brickworks trials encompassing the manufacture of >300000 experimental bricks. This work programme also included emission monitoring during the firing process, together with full physical testing of the experimental products for direct comparison with the standard commercial products manufactured at the collaborating brick factory. (C) 2002 Society of Chemical Industry.