Aeration tanks

Commercial-scale operations are conducted in batch, fed-batch, or continuous culture systems. Fermentation vessels include the conventional baffled aerated tank, with or without impeller agitation, and the ak-lift tower fermentors in which ak is sparged into an annular space between the... 

Phenol can be oxidi2ed and hence removed, ie, to levels <20 / g/L, from wastewater (248). Moreover, addition of potassium permanganate to the return activated sludge results in reduction of odors issued from the aeration tanks of conventional activated sludge wastewater treatment plants without any change occurring to the microbiology of the system (249). 

Fig. 4. Contact stabilization plant. Conventional activated-sludge process. The reaeration and contact tanks can be replaced by an aeration tank (21).

The floe returned to the aeration tank (10—50%) has the same function as trickling-filter slime. However, the floe concentration can be varied as operational needs dictate. Usually the so-called mixed Hquor—suspended soHds (MLSS) are 600—4000 mg/L (2.3—15 g/gal). 

Eoint-source pump of limited capacity. Experience has indicated that earings are a serious problem with mechanical-aeration equipment. Wave action generated within the aeration tank tends to produce lateral stresses on the bearings and has resulted in failures and increased... 

There is no standard aeration-tank shape or size. Aeration tanks can be round, square, or rectangular. Shallow aeration tanks are more difficult to mix than deeper tanks. Yet aeration-tank depths have ranged from 0.6 m (2 ft) to 18 m (60 ft). The oxidation-ditch systems tend to be shallow, while some high-rate diffused-aeration systems have used veiy deep tanks to provide more efficient oxygen transfer. 

Reaction and aeration tank lor phosphatic and acidic wastes... 

Activated sludge Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of organisms (including zoogleal bacteria) in aeration tanks in the presence of dissolved oxygen. The term "activated" comes from the fact that... 

Aeration tank The tank where raw or settled wastewater is mixed with return sludge and aerated. This is the same as an aeration bay, aerator, or reactor. 

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. 

Floe Clumps of bacteria and particulate impurities or coagulants that have come together and formed a cluster. Found in aeration tanks and secondary clarifiers. Flocculation The process of forming floe particles when a chemical coagulant or... 

MLSS Mixed Liquor Suspended Solids - the volume of suspended solids (see SS) in the mixed liquor (see ML) of an aeration tank. 

MLVSS Mixed Liquor Volatile Suspended Solids - the volume of organic solids that can evaporate at relatively low temperatures (550 C) from the mixed liquor of an aeration tank. This volatile portion is used as a measure or indication of microorganisms present. Volatile substances can also be partially removed by air stripping. 

The principal elements of the system include an aeration tank in which the wastewater is thoroughly mixed with continuously activated sludge and oxygen. From this part of the process, it passes into a clarifier tank, where the settled sludge is removed from the purified water to be recycled by the return activated sludge pumps. 

To enhance the purification process and increase the degree of purification, powdered activated carbon (PAC) may be added directly to the aeration tank, or the biologically treated wastewater may be filtered through granulated activated carbon (GAC) for posttreatment. 

Fig. 2.1. Reduction of carbohydrate in an aeration tank at various air flow rates.

Fig. 2.2. COD, cell dry weight (CDW), carbohydrate and dissolved oxygen concentrations in a 15 litres aeration tank at an air flow rate of 5 litres/min.

CASE STUDY OXYGEN TRANSFER RATE MODEL IN AN AERATED TANK FOR PHARMACEUTICAL WASTEWATER... 

Further experiments were conducted in a large aeration tank, 15 litres batch system to study die dry weight cell density, COD, carbohydrate, dissolved oxygen and oxygen transfer modelling. Two different airflow rates, 5 and 10 litres/min, were applied. However,... 

Fig. 3.5. COD reduction for small aeration tank with various airflow rates.

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