Environment dilute streams

Commercial operating conditions are mild and innocuous to the production environment. Process stream temperatures are below 110°F and pressures are less than 10 psi. While the products are usually corrosive or caustic, the relatively dilute aqueous form (typically 15 wt%) renders them significantly less harmful than the more conventional concentrated forms of acid and base (5(rBe, 98%, etc.) generally found in the plant environment. 

Combustion in an incinerator is the only practical way to deal with many waste streams.This is particularly true of solid and concentrated wastes and toxic wastes such as those containing halogenated hydrocarbons, pesticides, herbicides, etc. Many of the toxic substances encountered resist biological degradation and persist in the natural environment for a long period of time. Unless they are in dilute aqueous solution, the most effective treatment is usually incineration. 

The use of biodegradation for the treatment of dilute waste streams has already been discussed it also has potential for in-situ treatment. The critical need is to learn how to select and control microorgarrisms in a soil environment to achieve the desired degradation of organics. 

Osmotic effects are very important from a physiological standpoint. This is because biological membranes including the membrane of red blood cells behave like semipermeable membranes. Consequently, when red blood cells are immersed in a hypertonic solution (e.g., D5 A NS or D5NS), they shrink as water leaves the blood cells in an attempt to dilute and establish a concentration equilibrium across the blood cell membrane. Thus, when hypertonic solutions are administered into the blood stream, the fluid moves from interstitial and cellular space into the intravascular space. Conversely, when cells are placed in hypotonic environment (e.g., V2 NS), they swell because of the entry of fluid from the intravascular compartment, and may eventually undergo lysis. 

Environment Canada recently developed an evaluation system based on effluent toxicity testing, capable of ranking the environmental hazards of industrial effluents [185]. This so-called Potential Ecotoxic Effects Probe (PEEP) incorporates the results of a variety of small-scale toxicity tests into one relative toxicity index to prioritize effluents for sanitation. In the index no allowance has been made for in-stream dilution, therefore the acmal risk for environmental effects is not modeled. The tests performed on each effluent are the following bacterial assay [V.fisheri (P. phosphoreum), Microtox], microalgal assay S. capricornutum) crustacean assay (C. dubiay, and bacterial genotoxicity test E. coli, SOS-test). 

For CSTF runs, we need to have nutrient and product reservoirs which are connected to the fermenter aseptically. The rate of input and output stream needs to be controlled precisely. Sometimes, the control of the outlet flowrate can be difficult due to the foaming or plugging by large cell aggregates. Since the length of the run should last several days or even weeks to reach a steady state and also to vary the dilution rates, there is always a high risk for the fermenter to be contaminated. Frequently, it is difficult to reach a steady state because of the cell s mutation and adaptation to new environment. 

The decomposition of dilute mixtures of NH3 in a PBMR using Pd-alloy membranes was studied by Collins and Way [2.322], and by Gobina et aL [2.323]. This application is of potential interest in the treatment of coal gasification streams, and the laboratory results showed promise. It would be interesting to see, whether the same membranes prove robust in the real coal-gas environment. The use of a PBMR to study the hydrodechlorination of dichloroethane was reported by Chang et al. [2.324]. The reported potential advantage of the membrane would be in preferentially removing the by-product HCl, which deactivates the catalyst. The authors attribute the observed improved performance, however, to a dilution effect. 

The public awareness about the impact of human activity on the environment exerts a tremendous pressure on most industrial manufacturers and leads to the development of environmental-oriented catalysis. One of the main issues in this research field is the concern about the abatement of volatile organic compounds (VOC). Here, dilute VOC-containing effluent streams are by far the most prevalent, which makes their non-catalytic combustion an expensive operation since it requires a supplemental fuel supply [1]. The catalytic combustion, however, can be carried out at relatively low temperature with little or no... 

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