Incorporation of water sludge, silica fume, and rice husk ash in brick making

The water sludge is generated from the treatment of water with alum. Disposing of sludge again to the streams raises the concentrations of aluminum oxides in water, which has been linked to Alzheimer's disease. The use of water treatment plant (WTP) sludge in manufacturing of constructional elements achieves both the economical and environmental benefits. Due to the similar mineralogical composition of clay and WTP sludge, this study investigated the complete substitution of brick clay by sludge incorporated with some of the agricultural and industrial wastes, such as rice husk ash (RHA) and silica fume (SF). Three different series of sludge to SF to RHA proportions by weight were tried, which were (25: 50: 25%), (50: 25: 25%), and (25: 25: 50%), respectively. Each brick series was fired at 900, 1000, 1100, and 1200 o C. The physical and mechanical properties of the produced bricks were then determined and evaluated according to Egyptian Standard Specifications (E.S.S.) and compared to control clay-brick. From the obtained results, it was concluded that by operating at the temperature commonly practiced in the brick kiln, a mixture consists of 50% of sludge, 25% of SF, and 25% of RHA was the optimum materials proportions to produce brick from water sludge incorporated with SF and RHA. The produced bricks properties were obviously superior to the 100% clay control-brick and to those available in the Egyptian market. The disposal of the residuals generated during the various water treatment processes must receive careful consideration. These residuals include wash water and sludge. The sludge is composed of the impurities removed and precipitated from the raw water together with the residuals of any treatment chemical used. Disposal of alum sludge can be a major concern for water treatment plants (WTPs). Most of the WTPs in Egypt discharge the sludge into the river Nile again with no treatment at all. The discharging of sludge into water body leads to accumulative rise of aluminum concentrations in water, aquatic organisms, and human bodies. Some researchers have linked aluminum's contributory influence to occurrence of Alzheimer's disease, children mental retardation, and the common effects of heavy metals accumulation (Prakhar and Arup 1998). Consequently stringent standards of