TYPES OF SLUDGES: a) Excess activated; b) Primary with activated or trickling-filter sludge
TOTAL QUANTITY OF WET SLUDGE: From an average treatment plant, between 1 and 2% of the sewage volume (influent) treated
VOLATILE SOLIDS REDUCTION EFFICIENCY: 40 to 60%
REDUCTION EFFICIENCY OF DEGRADABLE VSS: 85%
EXCESS SLUDGE PRODUCED: 0.2 lb per lb of BOD5 removed
TYPICAL INFLUENT CONCENTRATION: Over 10,000 mg/l SS
ORGANIC SOLIDS LOADINGS RATE (LB/1000 FT3): Below 100 (b); generally in the range of 40 to 120
AIR REQUIREMENTS (CFM/1000 FT3): 15 to 20 (a); 25 to 30 (b)
DIGESTOR TANK DESIGN: Similar to activated-sludge tanks; they are usually not covered or insulated
AERATION METHODS: Same as in conventional aeration tanks; mechanical surface aerators are superior to diffused aeration systems.
TYPICAL APPLICATIONS: Industrial and small municipal waste treatment plants in which mostly excess activated sludge is treated; cannot be used in cold climates of stabilization of volatile solids also varies with the sludge. This section discusses aerobic digestion as a separate treatment after solids-liquid separation is complete.
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