Waste activated sludge thickening

Thickening waste activated sludge (WAS) is a common application for the decanter in the municipal waste industry. Unusually for the decanter in sewage applications, it often does not require polymer for good performance with this 

Fiitiire 6.14. Graph - Particle Size v Recovery Clay Classification. 

Fifitire 6.17. Graph - Centrate Solids Composition v Centrate Rate - Clay Classification. 

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Soft solids, most of which are biological waste such as sewage, are difficult to convey up the beach. Annular baffles or dams have been commonly used to provide a pool-level difference wherein the pool is deeper upstream of the baffle toward the clarifier and lower downstream of the baffle toward the beach. The pool-level difference across the baffle, together with the differential speed, provide the driving force to convey the compressible sludge up the beach. This has been used effectively in thickening of waste-activated sludge and in some cases of fine clay with dilatant characteristics. 

Detention Time Waste activated sludge only, after sludge thickening. 10 -15 days volumetric displacement time. If sludge temperatures are much less than 60°F, more capacity should be provided. Primary sludge mixed with waste activated or trickling filter humus. 20 days displacement time in moderate climates. 

DESIGN A GRAVITY THICKENER FOR COMBINED PRIMARY AND WASTE-ACTIVATED SLUDGE 16.46... 

Design a gravity thickener for a wastewater treatment plan having primary and waste-activated sludge with the following characteristics ... 

Plant 000012 produces 3.9 x 10" kkg/year (8.7 x lO lb/year) of emulsion crumb rubber, primarily neoprene. The contact wastewater flow rate is approximately 8.45 m /day (2.25 X 10 gpd) and includes all air pollution control equipment, sanitary waste, maintenance and equipment cleanup, and direct contact wastewater. The treatment process consists of activated sludge, secondary clarification, sludge thickening, and aerobic sludge digestion. Noncontact wastewater, with a flow rate of approximately 1.31 x 10 m /day (3.46 x 10 gpd), is used on a once-through basis and is remrned directly to the river source. Contact wastewater is also returned to the surface stream after treatment. 

Fig. 4.27. Schematic diagram of conventional activated sludge process. 1 — wastewater, 2 — air supply, 3 — sludge return, 4 — clarified effluent, 5 — waste sludge, A — aeration basin, B primary sedimentation tank, C — secondary sedimentation (thickening) tank... 

In today s world of waste treatment, bubble and foam separations lemain lelatively little used techniques. Dissolved or induced air flotation is the most commonly used variation, havii been enqiloyed for many years in the treatment of wastewaters for the separation of suspended sc, oils, greases, fibeis, and other iow-density solids as well as fbr the thickening of activated sludge and flocculated chemical sludges. The most active commercial use was and is in ore flotation—as discussed in Chapter 16. The potential Cor the use of these separation techniques, however, is veiy high in both the areas of traditional and hazardous waste management. 

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