Activated sludge treatment

As a result of several studies, the following conclusions regarding viruses in sewage warrant consideration (1) primary sewage treatment has little effect on enteric viruses (2) secondary treatment with trickling filters removes only about 40 percent of the enteroviruses (3) secondary treatment by activated sludge treatment effectively removes 90 percent to 98 percent of the viruses and (4) chlorination of treated sewage effluents may reduce, but may not eliminate, the number of viruses present. 

Dispersing a gas m a liquid as fine bubbles (e.g., oxygen from air m a suspension of microorganism for fermentation or for activated sludge treatment). 

The primary distinguishing feature of the improved activated sludge treatment system is that high-rate DAF is the secondary clarifier for separation of suspended solids from the activated sludge aeration basin effluent, as opposed to secondary sedimentation alone in a conventional activated sludge system. 

A typical overloaded conventional complete-mix activated sludge treatment plant (shown in Figure 27.11) has been described in Section 27.3.3. The same conventional treatment plant can be improved by the addition of a secondary flotation clarifier (shown in Figure 27.12). Some advantages of the improved activated sludge system are mathematically presented below. 

Many pilot-scale and full-scale trials involving the use of secondary flotation (Krofta Supracell) in activated sludge treatment plants were conducted by KEC and Lenox Institute of Water Technology (LIWT) (formerly Lenox Institute for Research). Only partial operational data are selected for presentation in this chapter. The readers are encouraged to contact the authors for details. In the illustration of each case history, the true names of the company and its resident engineer involved are omitted for the protection of the Company s privacy. 

Many pilot plant operations have been conducted by KEC through Krofta Apparatebau G.M.B.H., Germany, under direct supervision of Mrs Elisabeth Hurst-Gaul, Manager. The use of a Krofta Supracell DAF clarifier for secondary clarification in the activated sludge treatment plant has been concluded to be feasible. This chapter summarizes the results of her investigation. 

A conventional activated sludge treatment plant in Flouston, Texas, is heavily overloaded. KEC and the LIWT evaluated the flotation characteristics of MLSS in the Krofta Supracell... 

For an existing conventional activated sludge treatment plant having a fungi problem, installing a DAF clarifier between the existing aeration basin and the final sedimentation clarifier (shown in Figure 27.12) will be the remedy. 

Eckenfelder WW and Musterman JL (1995) Activated Sludge Treatment of Industrial Wastewater, Technomic Publishing. 

Johnson AC, Belfroid A, Di Corcia A (2000) Estimating steroid oestrogen inputs into activated sludge treatment works and observations on their removal from the effluent. Sci Total Environ 256 163-173... 

Nakada N, Tanishima T, Shinohara H, Kiri K, Takada H (2006) Pharmaceutical chemicals and endocrine dismpters in municipal wastewater in Tokyo and their removal during activated sludge treatment. Water Res 40 3297-3303... 

Andersen HR, Hansen M, Kjolholt J, Stuer-Lauridsen F, Temes T, Halling-Sorensen B (2005) Assessment of the importance of sorption for steroid estrogens removal during activated sludge treatment. Chemosphere 61 139-146... 

Fig. 3 Range of removal rates (a) and average removal efficiencies (b) for some of the most ubiquitous pharmaceuticals under conventional activated sludge treatment in the whole set of WWTPs under investigation...

Sepaflot A process for removing solids and oil from wastewater by a combination of Activated Sludge treatment and dissolved air flotation. Offered by Lurgi. 

More advanced water purification techniques, utilizing UV-irradiation, ozonization, or activated charcoal, may significantly improve the removal of these compounds, but these techniques are not broadly applied due to their high cost. Thus, current European activated sludge treatment plants, with a hydraulic residence time not greater than 14 h, can in most cases not completely eliminate all the estrogens and progestogens from the effluent [23]. 

As shown in Table 1, many FMs meet the biodegradation criteria of a ready or inherent test. If a FM meets the criteria of a ready test, with or without acclimation, a first-order biodegradation rate of 3 h 1 in activated sludge can be assumed [ 1 ]. For FMs that show extensive biodegradation but fail the ready test criteria, a first-order rate of 0.3 h 1 can be assumed for activated sludge treatment [1]. 

Figure 8B shows the regression of the measured percent overall removal from activated sludge treatment plants only measured by Simonich et al. with... 

Where the system is located at an industrial facility with its own treatment plant or where large quantities of water are produced, complete on-site treatment is often the most economical procedure. Phase separation followed by air stripping and contact biological (or activated sludge) treatments are common procedures. A more in-depth treatment of coproduced water handling is presented in Chapter 8. 

Stover, E. L., Fazel, A., and Kincannon, D. F., 1985, Powdered Activated Carbon and Ozone Assisted Activated Sludge Treatment for Removal of Toxic Organic Compounds Science and Engineering, Vol. 7, No. 3, pp. 191-203. 

Ganczarczyk JJ. 1979. Second-stage activated sludge treatment of coke plant effluents. Water Res 13(4) 337-342. 

Richards DJ, Shieh WK. 1989. Anoxic-oxic activated-sludge treatment of cyanides and phenols. Biotechnol Bioeng 33 32-38. 

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