Waste Sludge Processing

Trickling Filters. The so-called trickling filter is not a filter but a bed of stones or other coarse material (packing) over which the sewage flows. In terms of the total number of installations, it is the most widely used biological treatment process. However, the greatest total volume of waste is treated by the activity-sludge process (12). 

G. M. Shaul, R. J. Lieberman, C. R. Dempsey, and K. A. Dostal, "Eate of Azo Dyes in the Activated Sludge Process," presented at the 41st Annual Purdue Industrial Waste Conference, Purdue University, West Lafayette, Ind., May 13—15, 1986. 

In addition to many varied apphcations in the chemical industiy, the reactotherm is widelv used to process waste sludges which must be dried in order to lanc fill the sohd components. In many of these cases, the solvents are valuable components of the waste stream and can be recovered and recycled. 

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 ton/hr Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarhide, silica hydrogels Waste sludges and slurries... 

Disposal The final func tional element in the sohd-waste-management system is disposal. Disposal is the ultimate fate of all solid wastes, whether they are wastes collected and transported direc tly to a landfQl site, semisolid wastes (sludge) from industrial treatment plants and air-pollution-control devices, incinerator residue, compost, or other substances from various solid-waste processing plants that are of no further use. 

Comminution Shredding. A mechanical treatment process which cuts large pieces of waste into smaller pieces so that they won t plug pipes or damage equipment. Contact stabilization Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment. 

The activated sludge process usually must be preceded by neutralization and some metal removal, and possibly by solids removal. The process is normally followed up by a separation step, usually sedimentation, to remove the biological sludge from the waste liquid stream. 

Centrifugation is a well-established liquid-solid separation process popular in commercial and municipal waste treatment facilities. It is usually used to reduce slurry and sludge volumes and to increase the solids concentration in these waste streams. It is a technically and economically competitive process and is commonly used on waste sludges produced from water pollution control systems and on biological sludges produced in industry and municipal treatment facilities. 

While the emphasis here has been on the reduction of the amount of waste sludges, it is also equally important to address the problem of regulating the effluents and emissions. In this context, special mention may be made of ammonia which must be carefully regulated. The procedure for processing ammonium fluoride or ammonium sulfate containing solutions begins with lime treatment. The filtrates are fed continuously into a column and stripped with live steam and upgraded. In this way it is possible (with improved equipment and carefully controlled operation) to attain ammonia contents of less than 50 ppm in the effluent. 

Residual sulfur dioxide or hydrogen sulfide Air pollution control (APC) dust and/or waste treatment plant sludge Process wastewater Kish... 

Newer secondary recovery plants use lead paste desulfurization to reduce sulfur dioxide emissions and waste sludge generation during smelting. Battery paste containing lead sulfate and lead oxide is desulfurized with soda ash to produce market-grade sodium sulfate solution. The desulfurized paste is processed in a reverberatory furnace. The lead carbonate product may then be treated in a short rotary furnace. The battery grids and posts are processed separately in a rotary smelter. 

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