Aerobic biological treatment systems

Colox An aerobic biological treatment system for municipal and industrial wastes. The biomass is fixed as a film on granules in a fixed bed. Developed in Texas by Tetra Technologies. 

It should be noted that full treatment of the waste could be accomplished with a retention time of approximately 5 min when only 0.8 U/mL of crude or pure enzyme were used in the presence of PEG. In contrast, an aerobic biological treatment system that was used to treat this particular foundry waste required a retention time of approximately 6 hr. This illustrates one of the most significant advantages of enzymatic treatment. On the other hand, the use of crude enzyme preparations and PEG contributes significant quantities of organic compounds to the waste, which ultimately must be removed in a subsequent treatment step. 

Another promising approach for the detoxification of PCBs is the finding that anaerobic bacteria dechlorinate PCBs reductively [79, 80]. The authors used anaerobic microorganisms from Hudson River sediment and report that, at PCB concentrations of 700 ppm Aroclor, 63 per cent of the total chlorine was removed in 16 weeks, and the proportion of mono- and dichlorobiphenyls increased from 9 to 88 per cent. Dechlorination occurred primarily from the meta and para positions. These results indicate that reductive dechlorination may be an important environmental fate of PCBs, and suggest that a sequential anaerobic-aerobic biological treatment system for PCBs may be feasible. The proton source for the microbial reductive dechlorination of 2,3,4,5,6-pentachlorobiphenyl has been identified by Nies and Vogel [81]. Tlie authors report that the exact mechanism of the electron transfer for the dechlorination of PCBs is imknown however, they could show that the sotirce of tiie hydrogen atom is the proton from water, and that chloride is released from the PCB. 

Aerobic biological treatment systems such as aerated stabilisation basins and activated sludge are most commonly used to treat pulp mill wastewaters. A considerable reduction in BOD and TSS occurs in these systems, but color remains relatively unaltered. For example, the secondary treatment system of an integrated bleached kraft mill showed a 92 % reduction in BOD, a 60 % reduction in TSS but only a 1 % reduction in color (16),... 

Many different factors influence the performance of biological treatment systems. Although each specific biological process has special requirements, factors common to biological processes, besides biodegradabihty, include organic concentration, temperature, pH, nutrients, and oxygen (aerobic or anaerobic). 

When organics containing reduced nitrogen are degraded, they usually produce ammonium, which is in equilibrium with ammonia. As the pK for NH3 NH4" is 9.3, the ammonium ion is the primary form present in virtually all biological treatment systems, as they operate at pH < 8.5 and usually in the pH range of 6.5-7.5. In aerobic reactions, ammonium is oxidized by nitrifying bacteria (nitrosomonas) to nitrite... 

COD testing has several advantages over BOD. Notably the COD test is more rapid, more repeatable, less susceptible to interferences and less labor intensive. On the other hand, BOD is more strongly correlated to processes that actually occur in wastewater treatment systems and receiving waters. For typical textile wastes, the COD BOD ratio is typically about 3 1. Wastewater with higher ratios (e.g. 7 1) are resistant to aerobic biological treatment. (USEPA, 1996). 

Five types of biological treatment systems have been evaluated for explosives contaminated soils, including (1) composting, (2) anaerobic bioslurry, (3) aerobic bioslurry, (4) white rot fungus treatment, and (5) land farming. 

The cumulative wastewater engineering experience has evolved to the extent where the design of plants for aerobic suspended growth biological treatment systems... 

Some packaging paper mills in central Europe today run with zero effluent systems (Fig. 5.6 ) using a combination of anaerobic/aerobic biological treatment (see Section 10.1) as kidney technology for COD reduction [5]. 

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