الفهرس 
Heavy metalsOnly 14 pages are availabe for public view
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Abstract
Sludge produced from biological treatment processes normally contains from 95 to 99.5% water, mechanical and mechanical/chemical processes exist for thickening biological sludge. These processes utilize belt presses, frame presses, belt thickeners, and dissolved air floatation for reducing the water content in the sludge. The solids content of the thickened sludge leaving these processes varies from 40% to 30% depending upon the specific means of operation. Sludge often contains high concentrations of heavy metals as lead, mercury, cadmium which negatively affects the reuse of sludge after dewatering. Moreover, it affects the environment and the public health of the human. In most cases, the associated processing cost of dewatering sludge increase with the solid particles concentration.
In the present thesis, we used a simple method for dewatering the floated sludge by using nitrogen gas. The idea of this research is like theory with dissolved air flotation but using nitrogen gas under pressure. Flotation is a physical treatment method which is used for separation of solid or liquid particles from a liquid phase. Separation is carried out through introducing of fine gas bubbles, mostly gas, into liquid phase. Gas bubbles attach to solid particles and floating force of particles, gas bubbles are high enough to cause particle rise to surface. Thereby, particles with density more than liquid density can be forced to raise surface.
The objective of this research is to study the utilization possibilities of less expensive adsorbents for the elimination of heavy metals from wastewater sludge. Agricultural waste by-products such as date pits have are used for the elimination of heavy metals from wastewater sludge. Results showed agricultural waste can be used as absorbent for adsorption of contaminates for wastewater sludge as it has some advantages that include availability in large quantities, eco-friendly, cost-effective and renewable in nature.
This study planned to consider the aspect of pollution control and resource recovery: The technology used was quick in time and less in cost compared to other methods. There will be utilized a few added substances for improving the productivity of the treatment and dewatering of sludge from the wastewater treatment plant, by using alum, nitrogen gas for dewatering sludge and using date pits for removing heavy metals.
The researcher designed an experimental model for the treatment and dewatering of sludge from the wastewater treatment plant. In addition. The experiment was carried out in four stages: First, the bubbling pressure was used to dissolve N2 gas into the sludge; Second, alum was added to accelerate the process of coagulation of the sludge particles and facilitate their flotation; Third ,nitrogen gas was used to help floating the sludge particles and reduce the processing time because the nitrogen gas from the inert gases ; and Fourth, thickened sludge is taken after being dewatered and injected with fixed doses of heavy metals (lead Pb and mercury Hg), then the sample was injected with different doses of date pits and the remaining heavy metals found was measured. The best conditions of the experiments in this study were obtained as the bubbling pressure was 0.6 bar, the alum dose was 80 mg/l and the nitrogen gas amount was 60 mg/l.