Extended aeration process

Gaudy AF, Gaudy ET, Feng YJ, et al. 1982. Treatment of cyanide waste by the extended aeration process. J Water Pollut Control Fed 54 153-164. 

Design an extended aeration process for the treatment of 1275 m3/day of pharmaceutical wastewater with a BOD5 of 3500 mg/L. Assume the following conditions are applicable ... 

Over the years, the conventional activated sludge process has been modified to improve or to suit a specific operational condition. Some of the more common modifications are extended aeration process, contact... 

The activated sludge process including multiple-stage, extended aeration, the Unox pure oxygen system, aerated ponds, and other variations. 

The performance of the ASP has been found to be more efficient when operating on an extended aeration basis. The design parameters of the process were evaluated for the treatment of combined wastewater from a pharmaceutical and chemical company in North Cairo that produced drugs, diuretics, laboratory chemicals, and so on [49]. The study revealed that at an extended aeration period of 20 hours, COD and BOD removal efficiency ranges of 89-95% and 88-98%, respectively, can be achieved. The COD and BOD values of the treated effluent were found to be 74 mg/L and 43 mg/L, respectively. 

Figure 4 Flow diagram for treatment process using activated sludge, extended aeration.

An extended aeration activated sludge process is designed to treat 2000 m day of condensate waste generated from a synthetic organic chemical plant. The system is operating at an organic... 

Wong and Maroney [49] reported on a pilot plant comparison of PACT and extended aeration (activated sludge) for treating petroleum rehnery wastewater. Results indicated that although both processes performed similarly in COD removal, only the PACT system yielded an effluent meeting the discharge requirements for whole effluent toxicity reduction. Similar results in toxicity reduction have been reported for wastewaters from other industries [50]. 

X 10 kkg/year, respectively]. Wastewater consists of direct contact process water, noncontact blowdown, and noncontact ancillary water. The total flow of contact water is approximately 1.27 x 10 mVday (3.355 x 10 gpd), and the total flow of noncontact water is 340.4 mVday (9 X 10" gpd). Treatment of the wastewater consists of coagulation, sedimentation, and biological treatment with extended aeration. Treated wastewater is discharged to a surface stream. 

Various biological processes have been used with good results, including extended aeration/activated sludge, sequential batch reactors, and biofihn reactors. Anaerobic treatment has not been effective because of high sulfate levels. 

A wash water stream from a frozen french fries processing plant gives a TOC (total organic carbon) reading of 1.1% (by weight) as it enters the extended aeration facilities. 

Aqueous waste streams with BODs of 5,000 to 20,000, which are essentially nontoxic may be produced by a food processing industry or by a distillery, may be efficiently treated by extended aeration in lagoons, or in deep shaft... 

Many modifications for the conventional process have been proposed for improving the system or for treating a specific type of wastewater. These modified processes are extended aeration, contact stabilization, step aeration, tapered aeration, high rate, and pure oxygen process. 

Rossin et al (1982) concluded that the increased metal removal at high SRT of CAS processes is due to the increase in the MLSS concentration, to the change in the composition of EPS and the metal species. SRT changes influence the distribution between the bound and the soluble EPS, the biomass concentration in the mixed liquor and the bacterial population. Changes in bacterial populations are accompanied by changes in the composition of the bacterial cell surface and in the metabolic products of the cell which are released in the liquid phase. Also, very high SRT result in conditions of extended aeration and in the deflocculation that increases the secretion of EPS and metal solubility. 

Where present in boiler MU water, both iron and manganese may present fouling and deposition problems in the pre-boiler section. These problems may extend to the boiler section, and therefore these metals must be removed at source. Typically, this is achieved by oxidation followed by filtering off the flocculated iron. (Process examples are aeration towers, contact with chlorine, pressure filters with BIRM media, manganese greensand filters, etc.)... 

Under the high-rate conditions, the fluid remains approximately 2 hours in the aeration basin, and the BOD of feed is reduced between 50 and 70%. When maximum conversion is desired, over 95% of the BOD can be removed. This is termed an extended activated sludge process, and the average residence time is at least 18 hours. The conventional conditions are a compromise, with 90% of the BOD being removed and the fluid being detained around 5 hours.34 Table 16-3 gives the design information for these systems. 

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