一般污泥和含油污泥的处理方法（中英文）-环境影响评价工程师-筑龙技能培训论坛

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奖励

奖励于 2006-04-20 01:59:22

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flying_10

发表于2006-04-19 | 只看该作者

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The ways of regular sludge and oily sludge treating
Generally speaking， there is a procedure for treating sludge after secondary treatment of wastewater if we want to prevent our living environment from second polluting. Wastewater treatment objectives are accomplished by concentrating impurities into solid form and then separating these solids from the bulk liquid. This concentration of solids， referred to as sludge， contains many objectionable materials and must be disposed of properly. Sludge disposal facilities usually represent 40 to 60 percent of disposed of the construction cost wastewater-treatment plants， account for as much as 50 percent of the operating cost， and are the cause of a disproportionate share of operating difficulties.
First of all， the initial sludge is separated from the clean water lying upon it in the secondary clarifier by pumping it to a tank. Because the initial sludge have a high water content that usually can up to 99.5 percent in volume， sludge thickening is a necessary procedure， and there are several techniques are available foe volume reduction. Mechanical methods such as vacuum filtration and centrifugation may be used where the sludge is subsequently to be handled in a semisolid state. There methods are commonly used preceding sludge incineration. Where further biological treatment is intend，volume reduction by gravity thickening or flotation is common practice. In both cases， the sludge remains in a liquid state.
Gravity thickeners are very similar in design and operation to the secondary clarifiers used in wastewater treating systems. The thickening function is the major design parameter， and tanks are generally deeper than secondary clarifiers to provide greater thickening capacity. A well-designed， well-operated gravity thickener should be able to， at least double the solids content of the sludge. In another word， the water content ratio of sludge can be reduced from 99.5 percent in volume to 98 percent or ever much more reduction. It should be noted that the design of gravity thickeners should be based on the results of pilot plant analysis wherever possible， since successful loading rates are highly dependent on the nature of the sludge.
In dissolved air flotation， a small quantity of water， usually secondary effluent is subjected to aeration under a pressure of about 400kPa. This supersaturated liquid is then release near the bottom of a tank through which the sludge is passed at atmospheric pressure. The air is release in the form of very small bubbles that attach them selves to， or become entrapped in， the sludge solids， floating the solids to the surface. The thickened sludge is skimmed off at the top of the tank while the liquid is removed near the bottom and is returned to the aerator.
After volume reducing， sludge represents a considerable hazard to the environment and must be rendered inert prior to disposal. The most common means of stabilizing is by biological degradation. Because this process is intended to convert solids to unicellular end products， the term digestion is commonly applied to this process. Sludge digestion serves both to reduce the volume of the thickened sludge still further and to render the remaining solids inert and relatively pathogen-free. These goals can be accomplished by either anaerobic or aerobic digestion.
Sludge contains a wide variety of organisms， and thus requires a wide variety of organisms for its decomposition. The literature relating to anaerobic sludge digestion often divides the organisms into two kinds， the acid formers and the methane formers. So we can divide the anaerobic sludge digestion into two steps too. On the first step， the acid formers consist of facultative and anaerobic bacteria that solubilize the organic solids through hydrolysis. The soluble products are then fermented to acids and alcohols of low molecular weight. The second step， the methane formers consist of strict anaerobic bacteria that convert the acids and alcohols， along with hydrogen and carbon dioxides to methane. Becau

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