Pretreatment application

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

After the pilot-scale demonstration at a former petroleum storage site in Saratoga Springs, New York. Environmental Oxidation Systems, L.L.C., estimated the cost of consumables used during an ECP application. Pretreatment with 93% sulfuric acid would cost approximately 0.40 per 1000 gal of water treated. The hydrogen peroxide could be applied at a cost of 0.37 per 1000 gal of water treated. The electricity required by the electrodes would cost approximately 0.06 per 1000 gal of water treated (D22708H, p. 12). 

The issue of mismatch of thermal expansion coefficients similar to that for a composite membrane is also very critical for fuel cells. In the fuel cells, electrodes are attached to solid electrolyte membranes. Significant temperature variations during applications, pretreatments or regeneration of the membranes (e.g., decoking) can cause serious mechanical problems associated with incompatible thermal expansions of different components. A possible partial solution to the above problem is to use partially stabilized instead of fully stabilized zirconia. The former has a significantly lower thermal expansion coefficient than the latter. 

Notify users of applicable pretreatment standards and requirements,... 

Fig. 23. Two types of hollow-fiber modules used for gas separation, reverse osmosis, and ultrafiltration applications, (a) Shell-side feed modules are generally used for high pressure appHcations up to - 7 MPa (1000 psig). Fouling on the feed side of the membrane can be a problem with this design, and pretreatment of the feed stream to remove particulates is required, (b) Bore-side feed modules are generally used for medium pressure feed streams up to - 1 MPa (150 psig), where good flow control to minimise fouling and concentration polarization on the feed side of the membrane is desired.

Pretreatment ofFUlojs for Pone lain Enameling A.luminum, PEI Bulletin P-403 (70) and Enamel Preparation, Application, and Firingfor Porcelain Enameling Aluminum, PEI Bulletin P-404(70), Porcelain Enamel Institute, Washington, D.C., 1970. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

RO membrane performance in the utility industry is a function of two major factors the membrane material and the configuration of the membrane module. Most utility applications use either spiral-wound or hollow-fiber elements. Hollow-fiber elements are particularly prone to fouling and, once fouled, are hard to clean. Thus, applications that employ these fibers require a great deal of pretreatment to remove all suspended and colloidal material in the feed stream. Spiral-wound modules (refer to Figure 50), due to their relative resistance to fouling, have a broader range of applications. A major advantage of the hollow-fiber modules, however, is the fact that they can pack 5000 ft of surface area in a 1 ft volume, while a spiral wound module can only contain 300 ftVff. 

The incineration process may be viewed as consisting of four parts (1) preparation of the feed materials for placement in the incinerator (pretreatment), (2) incineration or combustion of the material in a combustion chamber, (3) cleaning of the resultant air stream by air pollution control devices (APCDs) which are suitable for the application at hand, and (4) disposal of the residues from the application of the process (including ash, and air pollution control system residues). 

As a first step in the selection process, the applicability of the various solidification/ stabilization processes for specific contaminants can be determined using Table 12. Since these waste treatment systems vary widely in their applicability, cost, and pretreatment requirements, many are limited as to the types of waste that can be economically processed. Waste characteristics such as organic content, inorganic content, viscosity and... 

In applying these general criteria, one should focus on the intended application. In wastewater treatment applications, filtration can be applied at various stages. It can be applied as a pretreatment method, in which case the objective is often to remove coarse, gritty materials from the waste-stream. This is a preconditioning step for waste waters which will undergo further chemical and physical treatment downstream. 

Depending on the type of filter device, additional requirements may be made of the cloth. For example, in a plate-and-frame press, the sealing properties of cloths are very important. In this case, synthetic cloths are more applicable staple cloths, followed by poly filament and monofilament cloths. In leaf filters operating under vacuum and pressure, the cloth is pulled up onto rigid frames. Since the size of a cloth changes when in contact with the suspension, it should be pretreated to minimize shrinkage. 

Chemical pretreatment is often used to improve the performance of contaminant removal. The use of chemical flocculants is based on system efficiency, the specific DAF application and cost. Commonly used chemicals include trivalent metallic salts of iron, such as FeClj or FeSO or aluminum, such as AISO. Organic and inorganic polymers (cationic or anionic) are generally used to enhance the DAF process. 

Efficient separation or pretreatment in the influent streams can include activated carbon absorption to reduce or prevent such problems. Principal applications of electrodialysis include ... 

Hydrofining usually involves only minor molecular changes of the feed with hydrogen consumption in the range of about 100 to 1,000 cu.ft./bbl. Typical applications include desulfurization of a wide range of feeds (naphtha, light and heavy distillates, and certain residua) and occasional pretreatment of cat cracker feeds. 

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