Biological treatment processes

There are three main types of biological process1-3  

Aerobic. Aerobic reactions take place only in the presence of free oxygen and produce stable, relatively inert end products such as carbon dioxide and water. Aerobic reactions are by far the most widely used. The oxidation 

Endogenous respiration reactions also occur, which reduce the sludge formation  

Nitrification reactions can occur, in which organic nitrogen and ammonia are converted to nitrate  

The nitrification reactions are inhibited by high concentrations of ammonia. 

It actually degrades target compounds, rather than just transferring them from one medium to another  

It is probably less expensive than incineration, especially for small volumes of contaminated soil. 

Although the two terms occasionally are interchanged, biodegradation is not synonymous with mineralization. Mineralization, which is the process by which compounds are transformed into carbon dioxide and water, is only one of several fates of contaminants in biological treatment systems. Contaminants also may be volatilized, bind to organic materials, be assimilated into an active biomass, or be transformed into compounds 

Bioremediation is most effective for dilute solutions of explosives and propellants. TNT in the crystalline form is difficult to treat biologically. 

TNT degrades under aerobic conditions into monoamino-, diamino-, and hydroxylamino-DNT, and tetranitro-azoxynitrotoluenes. RDX and HMX degrade into carbon dioxide and water under anaerobic conditions. Researchers have not identified any specific organisms that are particularly effective for degrading explosives waste a consortium of organisms usually effects the degradation. 

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Clarifiers typically are used in chemical precipitation and biological treatment processes to remove precipitated metal soHds and suspended biological soHds. To prevent the sludge blanket from becoming too thick or heavy, part of the sludge blanket is removed continuously or intermittently from the system and thickened prior to disposal. 

Trickling Filters. The so-called trickling filter is not a filter but a bed of stones or other coarse material (packing) over which the sewage flows. In terms of the total number of installations, it is the most widely used biological treatment process. However, the greatest total volume of waste is treated by the activity-sludge process (12). 

The four most common aerobic biological treatment processes are stabilization ponds, aerated lagoons, trickling filters, and activated sludge (see... 

Three-phase fluidized bed reactors are used for the treatment of heavy petroleum fractions at 350 to 600°C (662 to 1,112°F) and 200 atm (2,940 psi). A biological treatment process (Dorr-Oliver Hy-Flo) employs a vertical column filled with sand on which bacderial growth takes place while waste liquid and air are charged. A large interfacial area for reaction is provided, about 33 cmVcm (84 inVirr), so that an 85 to 90 percent BOD removal in 15 min is claimed compared with 6 to 8 h in conventional units. 

FIG. 25-49 Effect of BSRT on biological treatment process performance, m = minimum BSRT. 

Biological treatment processes can be used to treat organic contaminants in liquid, slurry, and soil matrices. However, it should be remembered that moisture is an essential need of the biomass both for... 

There are two major types of biological treatment processes attached growth and suspended growth. 

Secondary Treatment A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated. Sedimentation The process of subsidence and deposition of suspended matter from a wastewater by gravity. 

Mueller JG, SE Lantz, BO Blattmann, PJ Chapman (1991a) Bench-scale evaluation of alternative biological treatment processes for the remediation of pentachlorophenol- and creosote-contaminated materials solid-phase bioremediation. Environ Sci Technol 25 1045-1055. 

Wang, L.K., Shammas, N.K., and Hung, Y.T., Eds, Advanced Biological Treatment Processes, Humana Press, Totowa, NJ, 2009. 

Case 2 Comparison of Two Biological Treatment Processes Using... 

Loukidou, M.X. and Zouboulis, A.I., Comparison of two biological treatment processes using attached-growth biomass for sanitary landfill leachate treatment, Environ. Pollut., Ill, 273-281, 2000. 

Biological Treatment Processes for Urea and Formaldehyde Containing Wastewater... 

The deep shaft biological treatment process,87 which is one of the activated sludge systems, has been successfully applied to a paper mill wastewater treatment in Japan (see Case Study III, Section 21.6.3). 

Source Adapted from Daly, P.G. and Shen, C.C., The deep shaft biological treatment process, in Proceedings of the 43rd Purdue Industrial Waste Conference, May 1988. With permission. BOD, biochemical oxygen demand COD, chemical oxygen demand TSS, total suspended solids. 

The biological treatment process involves the use of microorganisms such as bacteria and fungi to convert finely divided colloidal and dissolved carbonaceous organic matter in wastewater into various gases and into cell tissues that are then removed from sedimentation tanks as flocculent settle-able organic and inorganic solids. This process often complements both physical and chemical processes and it is classified as follows. 

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