The present study investigates the possibility of using water treatment plant (WTP) sludge of New Assiut city (Assiut-Egypt) as partial substitute for shale in brick making. Due to the high content of organic matter in water sludge, incineration of the WTP sludge is necessary to remove of all organic compounds contained therein. For brick making, mixture of various proportions from 10 % to 50% by weight of sludge ash added to shale are used as raw materials in hand molding brick making. The produced brick samples after drying process and firing at 1000 0 C for 6 hr ,, s , received a series of tests including firing shrinkage , weight loss on ignition water, absorption ,bulk density ,compressive strength , slake durability and efflorescence test. Satisfactory results were achieved when the percentage of sludge ash was up to 30% (by wt.) or less in the mixture. The specifications of the produced bricks match the Egyptian standard ES: 1756/1989 of fired clay building units for non load bearing walls. The test results indicate that, the sludge ash proportions are one of the most important key factors determining the brick quality. Reuse of sludge ash as a construction and building material converts the waste into useful products that can alleviate the disposal and environmental problems.

A large quantity of sludge is generated each year from the water treatment plants in Egypt. Some plants dispose the generated sludge into the Nile river, the others which far from the Nile river banks dispose the sludge in the nearest site beside the plant. The pumped sludge contains at least 96 % water, which causes certain environmental problems and health hazards in the future. The future trend of sludge management, are to convert the produced sludge into useful materials. One of the industrial centrifugal separators is the hydrocyclone. It has been used widely in industry for dewatering suspensions, such as liquid clarification, slurry thickening (or both simultaneously), and solid washing. The present work focused on the use of one stage or two stage hydrocyclone as dewatering tool for thickening, the sludge generated from water treatment plant of New Assiut City (Assiut, Egypt). The effect of feed concentration on dewatering performance of the hydrocyclone was studied using two identical hydrocyclones each of 50 mm diameter. The obtained results show that, using one stage hydrocylone is not effective in thickening the sludge. To improve overall recoveries of thicker sludge and clearer overflow simultaneously, two stages hydrocyclone connected in series are used. The overall recovery of the whole system is better than the recovery of any of the individual cyclones used within 20-24 % when diluted feed solid concentration less than 2 % was used. It is hoped that this work will lead to an improvement in the utilization of the hydrocyclones in dewatering the sludge generated from fresh water treatment plants.

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