Sludge rising

Section 27.7 discloses the common causes of sludge rising and sludge bulking and discusses other possible alternatives for biological process optimization. 

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. 

Biosorption. This process makes use of a phenomenon observed but ignored by many iavestigators. If activated sludge floe and raw sewage are mixed and aerated, there is first a significant reduction ia BOD of the efflueat. It is foUowed by a aotable BOD rise and then by a decrease. Originally,... 

Flotation. Flotation (qv) is used to remove suspended soHds from wastes and for the separation and concentration of sludges (52,53). The waste flow is pressurized in the presence of sufficient air to approach saturation. When the pressurized air—Hquid mixture is released to atmospheric pressure in the flotation unit, minute air bubbles are formed. As they rise in the Hquor the sludge floes and suspended soHds are floated to the surface where the air—soHd mixture can be skimmed off. 

One way of implementing the UV disinfection process at existing activated sludge plants involves suspending the UV lights (in the form of low-pressure mercury arc UV lamps with associated reflectors) above the secondary clarifiers. The effluent is exposed to the UV radiation as it rises over the wire in a thin film. 

Pin Floe Excessive solids carryover. May occur from time to time as small suspended sludge particles in the supernatant. There are two kinds grey -ashlike, inert, has low BOD - indicates old sludge and brown, but a portion neither settles nor rises, has high BOD - indicates young sludge. 

Septic Tank Untreated liquid household wastes (sewage) will quickly clog your absorption field if not properly treated. The septic tank is a holding tank in which this treatment can take place. When sewage enters the septic tank, the heavy solids settle to the bottom of the tank the lighter solids, fats and greases partially decompose and rise to the surface and form a layer of scum. The solids that have settled to the bottom are attacked by bacteria and form sludge. 

The primary types of corrosion inhibitor treatments employed are generally based on inorganic chemicals such as sodium nitrite (together with combinations of borate, silicate, molybdate, and phosphate) and the addition of even 2 to 3 pints (0.95-1.4 liters) to a boiler can immediately raise the TDS in the BW to a level at which priming can occur. Secondary problems include an associated rise in the level of BW suspended solids and sludge. 

The rising cost of scrap and waste disposal, the scarcity of onsite landfill space, and potential environmental liabilities make it an economic necessity to recover iron units from dust and sludge. However, recycling to the blast furnace raises the hot metal phosphorus content to undesirable levels. 

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