Secondary sludge

The secondary sludge in the secondary flotation clarifier is floating thus sludge rising is no longer a problem, and in fact, becomes a big plus. 

From Table III, the offensive nature of untreated sludge can again be seen. It is also clear that the effect of storage is most marked with secondary sludges. 

Suspended solids, which were found in up to three times higher concentrations in hospital effluent than municipal sewage, can be very efficiently removed by coagulation/flocculation [8, 16], thereby averting their accumulation on primary and secondary sludge. 

Wastewater treatment Solid Primary and secondary sludge, chemical sludge... 

Table I. Residue Organics TA98 Mutagenesis for Primary and Secondary Sludge Extracts Prepared by Various Procedures...

Procedure Metabolic Activation Primary Sludge Extracts Secondary Sludge Extracts... 

Table II. Effects of Method of Moist Pellet Processing on the Isolation of Mutagenic Residue Organics from Secondary Sludge...

Solid wastes represent the ultimate in mill residues and include the accumulated refuse of the mill and the sludges from primary and secondary effluent treatment. There is difficulty in removing water from the secondary sludge the primary and secondary sludges often are mixed to aid in water removal, which is important if the sludge is to be incinerated for disposal. The sludges from pulp and paper mills are handled mostly as landfill, and sometimes, if not toxic, they are spread for agricultural purposes. 

Flotation Air flotation has proved to be successful in concentrating secondary sludges to about 4 percent solids. The incoming solids are normally saturated with air at 275 to 350 kPa (40 to 50 psig) prior to being released in the flotation tank. As the air comes out of solution, the fine bubbles are trapped under the suspended solids and carry... 

Bahco units have been installed on municipal waste treatment facilities in two Japanese cities. These units will be part of a total pollution abatement facility. The units are operational and are awaiting the completion of the secondary sludge incinerators. The units will be operated with caustic soda. 

In a test program currently underway, dried wood fines will be used as fuel for the thermal degradation of a sodium based pulp mill secondary sludge. Key questions to be answered are What is the minimum temperature required to... 

The secondary sludge is usually pumped from the after-sedimentation into the primary settlers, and processed together with the primary sludge as a mixed sludge. Here, the primary sludge is the prevalent material. 

Figure 1. Examples of particulate size frequency distributions in natural waters and wastewaters. (A) Effluent, sedimentation basin, pilot-activated sludge plant, light microscope (26) (%) Lake Zurich, 40 m, 612176, Zeiss Videomat (19 (D) Deer Creek Reservoir, Utah, 20 m, 3/76, HI AC-12 Channel Counter (16) (O) digested primary and secondary sludge. Coulter Counter (S).

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