Multi-stage treatment

To achieve the required reductions in metal ion concentrations, it may be necessary to carry out a multi-stage treatment. In other cases, the treatment may require the oxidation state of the metal to be changed (e.g., oxidation of ferrous iron to ferric, which is more readily removed at low pH levels, and reduction of soluble Cr(VI) to Cr(III), which can readily be precipitated). 

The results of multi stage enzyme treatment suggests that further study of cellulase action is fully warranted. One hopeful area would be to decrease the hydrolysis time and enzyme concentration, and increase the number of stages. Another approach would be to remove the sugars by some other means, such as dialysis or fermentation (20). 

Assess results Several methods can be applied to minimize the ozone consumption in combined processes of ozonation and biodegradation. For example, the different operational behavior of batch and continuous-flow systems, with the resulting differences in oxidation products, etc. has to be considered, as well as the fact that multi-stage systems for each treatment process may be of advantage over single stage systems. 

After we have used water, it must be treated again before it can be returned to rivers, lakes and seas. This multi-stage process known as sewage treatment is shown in Figure 11.41. 

Supernova events as well as pre-supernova stages of stars play important roles in cosmochemistry. However, a number of aspects of astrophysics of both pre-supernova and supernova stages of evolution of massive stars remain unclear, as emphasized by Marcel Arnould (this volume). A major challenge comes from the uncertainties in the rates of some nuclear reactions and of weak interaction processes. Multi-dimensional simulations, especially of the late presupernova phases, are expected to be particularly helpful to understand these processes. Similarly, considerable efforts are still required for successful simulations of supernova explosions based on less uncertain pre-supernova models. Here again, the multi-dimensional treatment of a variety of physical effects, including rotation, magnetic fields, instabilities of different origins, and the transport of neutrinos needs careful inclusion. 

In Japan, multi-stage pig iron treatments have been developed, which include desulfurisation, de-siliconisation (using iron oxide), and de-phosphorisation (using lime plus fluorspar, or sodium carbonate), prior to the BOS process [27.5-27.7]. Such treatments are understood to have the potential to reduce lime consumption in the BOS process by about 25 % relative to the current levels, quoted in section 27.4. 

To suppress the reverse reactions, Matzing (1989a,b) proposed multi-stage plasma treatment with intermediate removal of the oxidation products. More interesting quenching effects occur in the plasma-generated droplets (see Section 11.7.4). In such droplets at certain pH conditions, it is possible not oidy to stabilize NO2 by formation of nitric acid in the solution but also to reduce NO2 to molecular nitrogen (N2) with simultaneous oxidation of sulfur from S(IV) to S(VI)... 

Wastewaters from paper factories containing dyes particularly aniline and sulfur ones are generated from the paper treatment process consisting in the addition of fillers and dyes to the bleached cellulose material. As a result of multi-stage purification of wastewaters from the cellulose plants, there is obtained a low value of BOD (biochemical oxygen demand) - 4 mg/L but COD (chemical oxygen demand) is maintained on the level 75 mg/L. These waste-waters contain a small amormt of suspended matter - 5 mg/L, but they are characterized by intensive colour - 40 mg Pt/L [21]. 

The following treatment techniques are applied sedimentation hydroxide precipitation multi-stage precipitation wet oxidation filtration procedures. 

The extract contains, in addition to the sucrose, further solved or colloidally dispersed components, which in the juice purification stage must be - as far as possible - precipitated or destroyed under alkaline conditions by adding calcium oxide. This is carried out by a multi-stage, continuous treatment with, first, calcium oxide and, second, carbon dioxide. Both processing aids are produced in a separate calcining process in parallel. The excess calcium oxide is precipitated in so-called carbonation vessels with carbon dioxide from the calcining process. All precipitates and deposits are separated in a multi-step filtration. The sludge... 

The other processes apply partly different atmospheres. In the oil-heat-treatment (OHT) vegetable oil is used in the French systems e.g. nitrogen is used (Retified Wood [bois retifie], NOW [new option wood]). The multi-stage PLATO (Providing Lasting Advanced Timber Option) process uses in the first... 

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