Wastewater biological transformations

Tchobanoglous, G. (ed.) (1981), Occurrence, effect and control of the biological transformations in sewers. Chapter 7 in Metcalf and Eddy, Inc., Wastewater Engineering Collection and Pumping of Wastewater, McGraw-Hill, New York, pp. 232-268. 

During domestic wastewater treatment, the concentratiOTi of several PFA and PFS has either remained constant or has even increased during the treatment process. The latter phenomenon probably is due to biological transformation of certain precursor compounds such as N-EtFOSAA [63],... 

It has been recognized for some time that fluids in motion, such as the atmosphere or the ocean, disperse added materials. This properly has been exploited by engineers in a variety of ways, such as the use of smoke stacks for boiler furnaces and ocean ontfalls for the release of treated wastewaters. It is now known that dilution is seldom the solution to an enviromnental problem the dispersed pollutants may accumulate to undesirable levels in certain niches in an ecosystem, be transformed by biological and photochemical processes to other pollntants, or have nnanticipated health or ecological effects even at highly dilute concentrations. It is therefore necessary to rmderstand the transport and transformation of chemicals in the natural environment and through the trophic chain ctrlminating in man. 

Reemtsma T, O Fiehn, G Kalnowski, M Jekel (1995) Microbial transformations and biological effects of fungicide-derived benzothiazoles determined in industrial wastewater. Environ Sci Technol 29 478-485. 

Microbial transformations and generally not chemical transformations characterize the sewer environment in terms of quality transformations of the wastewater. On the other hand, the physicochemical characteristics, e.g., diffusion in the biofilm and exchange of substances across the water-air interface, play an important role and must be integrated with the microbial transformations. The hydraulics and the sewer solids transport processes have a pronounced impact on the sewer performance. These physical processes, however, are typically dealt with in hydraulics and are, therefore, only included in the text when directly and closely related to the chemical and biological processes. 

Heterotrophic bacterial processes dominate transformations in the sewer. There are similarities with the corresponding processes in biological treatment plants. It is, however, from the very beginning, important to emphasize that transformations of wastewater under sewer conditions and in activated sludge or biofilm systems proceed differently. The processes in sewers, treatment plants and receiving waters must be dealt with as an entity however, they must also be considered with their own specific characteristics. 

This chapter deals with the microbial transformations of wastewater under aerobic conditions in a sewer network. It emphasizes the transformations of the organic matter and includes processes in both the water phase and the biofilm. Furthermore, transformations of particles in suspension originating from sewer sediments are included. A concept and a corresponding model for the integration of the major microbial processes, i.e., growth of the heterotrophic biomass, the respiration and the hydrolysis, are also dealt with. The basic chemical and biological aspects of sewer processes are focused on in Chapters 2 and 3. The reaeration process is dealt with in Chapter 4. 

My intent is for the book to contribute to an understanding of the sewer as a chemical and microbiological reactor for the transformation of wastewater, and that the processes within it influence not just the sewer system but the entire urban wastewater system. Chemical and biological processes in wastewater start at the sink and not at the inlet to treatment plants — or in the receiving waters during combined sewer overflows. 

The anaerobic digestion (AD) process is a pilot-scale up-flow fixed bed reactor made of a circular column of 3.5 m height, 0.6 m diameter and an originally useful volume of 0.984 m Cf. Figure 8). It performs the biological anaerobic fermentation of distillery wastewater, transforming organic carbon into methane and carbon dioxide. 

Biological. In activated sludge, 31.5% of the applied chlorobenzene mineralized to carbon dioxide after 5 d (Freitag et al., 1985). A mixed culture of soil bacteria or a Pseudomonas sp. transformed chlorobenzene to chlorophenol (Ballschiter and Scholz, 1980). Pure microbial cultures isolated from soil hydroxylated chlorobenzene to 2- and 4-chlorophenol (Smith and Rosazza, 1974). Chlorobenzene was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum. At a concentration of 5 mg/L, biodegradation yields at the end of 1 and 2 wk were 89 and 100%, respectively. At a concentration of 10 mg/L, significant... 

Biological. o-Phthalic acid was tentatively identified as the major degradation product of di-.n-octyl phthalate produced by the bacterium Serratia marcescens (Mathur and Rouatt, 1975). When di-.n-octyl phthalate was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, no degradation was observed after 7 d. In a 21-d period, however, gradual adaptation did occur, resulting in 94 and 93% losses at concentrations of 5 and 10 mg/L, respectively (Tabak et ah, 1981). In the presence of suspended natural populations from unpolluted aquatic systems, the second-order microbial transformation rate constant determined in the laboratory was reported to be 3.7 + 0.6 x lO L/organism-h (Steen, 1991). 

Biological. Under aerobic conditions or in experimental systems containing mixed cultures, hexachloroethane was reported to degrade to tetrachloroethane (Vogel et al, 1987). In an uninhibited anoxic-sediment water suspension, hexachloroethane degraded to tetrachloroethylene. The reported half-life for this transformation was 19.7 min (Jafvert and Wolfe, 1987). When hexachloroethane (5 and 10 mg/L) was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum for 7 d, 100% biodegradation with rapid adaptation was observed (Tabak et al, 1981). 

Research to date has focused primarily on azo and anthraquinone dyes, due to their commercial importance. Environmental processes including biodegradation, photolysis, sorption to soils and sediment, and abiotic transformation in sediment /water systems have been studied. The quantity of dyes apparently entering and potentially passing through wastewater treatment systems unaltered has prompted research on the behavior of these chemicals in biological and other types of wastewater treatment systems. 

Wiesmann, U. Biological Nitrogen Removal from Wastewater. Vol. 51, p. 113 Winterhalter, P., Skouroumounis, G. K. Glycoconjugated Aroma Compounds Occurence, Role and Biotechnological Transformation. Vol. 55, p. 73... 

In secondary treatment, a biological process is used where wastewater passes through tanks in which bacteria consume pollutants and transform them into carbon dioxide, water, and more biological cells. Following the biological process, settling is required, which is a physical treatment process. 

Among these plants, the wastewater rehabilitation plant of the Voronezh synthetic rubber plant (Russia) is worth to mention [2]. Here, two electron accelerators (0.7-1 MeV energy and 50 kW power), can treat up to 2,000 m of wastewater per day with the specific goal to transform the non-biodegradable emulsifier Nekal into a biodegradable form. A further decomposition is achieved with biological methods. 

Reemtsma T, Fiehn O, Kalnowski G, Jekel M (1995) Microbial Transformations and Biological Effects of Fungizide-Derived Benzothiazoles Determined in Industrial Wastewater. Environ Sci Technol 29, 478-485... 

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