Water , treatment

Water treatment, often closely allied to detergency, may be carried out for various reasons which include 

In 1927, Hall first described the use of trisodium phosphate in boiler water to reduce scale formation [9]. A later patent in 1933 relates to the use of sodium metaphosphate to reduce alkalinity and sequester unwanted cations. Numerous patents, particularly in the 1930-1950 period, relate to the use of various oligo- and metaphosphates in all the applications (l)-(6) above. This gave rise to the wide range of commercial products which are available today. 

The water treatment method depends on many variables including, but not limited to, the availability of alternative methods, the economics of replacements, and practical limitations related to the implementation of aphysical/chemical treatment. 

A crucial aspect of water is its total dissolved solids (TDS). The existence of halophilic (salt-loving) SRB in waters with very high TDS (240,000 mg/L) has been reported [11]. Other aspects of water/biocide interaction (such as water activity and TDS content) will be discussed in more detail in Chapter 9. 

The oxygen concentration of water, as bulk fluid, may not always be useful and, in fact, it can even be deceiving. As discussed in Chapter 4, biofilms are capable of forming anaerobic patches in otherwise aerobic bulk solutions. It has been reported that a biofilm with a thickness of only 12 pm may be sufficient to create totally anaerobic regions in an anaerobic system where at the base of the biofilm, SRB can be motile and active [11]. Having said that, some researchers believe that by knowing the chemical oxygen demand (COD), it may be possible to know the concentration of electron donors available for sulphate or metal reduction so that a low COD would mean a low risk of availability of SRB or other types of reducers such as IRB [12]. 

After treatment, water is passed through a sand filter followed by an activated carbon filter to remove traces of chlorine, and then through a polishing filter (usually a cartridge filter of pore size 10 pm). 

Chitosan has been widely accepted in the purification process of water by virtue of its metal ion chelating capability and acting as a flocculating agent because of its poly-cationic character. It is also used as an adsorbent for removal of dyes from water. Pesticides and chemicals such as phenols, methyl mercury acetate, plutonium, etc., can be removed from wastewater [170]. 

The function of aeration in a wastewater treatment system is to maintain an aerobic condition. Water, upon exposure to air, tends to estabUsh an equihbrium concentration of dissolved oxygen (DO). Oxygen absorption is controlled by gas solubiUty and diffusion at the gas—hquid interface. Mechanical or artificial aeration may be utilised to speed up this process. Agitating the water, creating drops or a thin layer, or bubbling air through water speeds up absorption because each increases the surface area at the interface. 

The solubihty of a gas in water is affected by temperature, total pressure, the presence of other dissolved materials, and the molecular nature of the gas. Oxygen solubihty is inversely proportional to the water temperature and, at a given temperature, directly proportional to the partial pressure of the oxygen in contact with the water. Under equihbrium conditions, Henry s law apphes 

Dissolved matter lowers oxygen solubihty. At 20°C and 101.3 kPa (1 atm), the equihbrium concentration of dissolved oxygen in seawater is 7.42 mg/L. It is 9.09 mg/L in chloride-free water and 9.17 mg/L in clean water. This lessening of oxygen solubihty is of importance to wastewater treatment. The solubihty of atmospheric oxygen in a domestic sewage is much less than in distilled water (12). 

The driving force in diffusion involves differences in the concentration of the diffusing substance. The molecular diffusion of a gas into a hquid is dependent on the characteristics of the gas and the hquid, the temperature of the hquid, the concentration deficit, the gas to hquid contact area, and the period of contact. Diffusion may be expressed by Pick s law (13,14)  

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

One of the things we tend to take for granted is the availability of good drinking water. Most people of the world aren t as fortunate as we are. 

The water is brought in from a lake, stream, or reservoir and initially filtered to remove sticks, leaves, dead fish, and such. The turbidity (haziness) that s commonly present in river or lake water is removed through treatment with a mixture of alum (aluminum sulfate) and lime (calcium hydroxide), which forms gelatinous aluminum hydroxide and traps the suspended solids. This is basically the same treatment used in wastewater treatment plants (see Primary sewage treatment .  

Then the water is filtered again to remove the solid mass of fine particles (called a flocculate or floe ) leftover from the initial filtering treatment. Chlorine is added to kill any bacteria in the water. Then it s run through an activated charcoal filter that absorbs (collects on its surface) and removes substances responsible for taste, odor, and color. Fluoride may be added at this time to help prevent tooth decay. Finally, the purified water is collected in a holding tank, ready for your use. 

An alternate and improved means to achieve enhanced coagulation in treating drinking water, a composition for removing turbidity, particles, and color from drinking water, includes (a) primary polymeric coagulant refers to a cationic polymer (a natural, cationic polymer as chitosan or a cationic starch) which enhances the 

Water-soluble materials can readily be removed. If the resulting wastewater containing the dissolved substances is discarded to the outside, environmental pollution issues may result, so that clarification treatment may be required. Water color may indicate the presence of organic material. It may be necessary to isolate and eliminate the water-soluble materials in wastewater by means other than boiling, which may not sufficiently remove dissolved contaminants (inorgaiuc, organic). Procedures employed include (a) Ultrafiltration membranes are made of polymers with 

Goldman, L. Goldstein, E. Katchalski, in Biochemical Aspects of Reactions on SoUd Supports , GR. Stark, ed. Academic Press, NY, Ch 1, p. 1, 1974 

Salmona, C. Saronia, S. Garattini, eds, Immobilized Enzymes , Raven Press, NY, 1974 

Messing, ed, Immobilized Enzymes for Industrial Reactors , Academic Press, NY, 1975 

There is no single valid solution with regard to water treatments. The specific conditions of water supplies can be vastly different, even in systems separated by only a few meters. The evaluation of the water quality is typically determined by a chemical water analysis [9], As shown in Table 8.13, there are basically two general categories of water treatment methods  

Post-treatment Acid and caustic solution for cleaning of polluted thermal systems inclusively the neutralization of applied chemical detergents. 

Pretreatment Filtration of the subsoil water predominantly sand as filtering medium, in pressure and gravity filters. 

Post-treatment Automatic cleaning of tubes heat exchangers by sponge rubber balls or brushes without operating interrupt of the plant. 

In most engineering applications the supply water is not suitable for immediate use without treatment. It is essential that the method of water treatment selected be the one most suited to the application. If steam is used as the working medium for a process, it is essential that water treatment be used to prevent the precipitation of substances in the water from fouling pipe work and heat exchangers otherwise costly plant damage will result. 

The method of treatment selected depends on many factors, such as the nature of the salts and the pH of the water, and the assistance of a reputable specialist company is necessary to carry out regular testing and an analysis report. 

In the case of boilers operating at low pressure, organic materials such as natural and modified tannins, starches, or alginates are added to aid blowdown. For boilers operating at high pressure, synthetic materials such as polyacrylates and polymethacrylates have been developed. The most commonly used chemicals for boiler feedwater treatment are phosphates and hydrazine. 

External treatment involves the removal of impurities from the water by various methods before it enters the plant this is the most effective method of water treatment. This category of treatment involves one or more of the following processes. 

In sedimentation the water to be treated flows slowly through a tank, allowing the suspended material in the water to fall to the base of the tank. The use of coagulating compounds, such as aluminum and ferric sulfate, increases the efficiency. 

The largest liquid-pha.se application of activated carbons is in water treatment, where the demand for activated carbon has increased rapidly over the last few years the average annual rate of increase is about 6.6% in the USA [65]. It is important at the outset to note that there are various areas of water treatment, which are distinguished principally by the objectives of the treatment process. 

The water employed in industrial processes such as heat exchangers, cooling towers, and steam generators is obtained from the most convenient local sources. This water must be treated to remove species that can give rise to corrosion, the formation of deposits, and fouling. Here too, adsorption on activated carbon is often an integral part of the treatment process. 

A third important area of water treatment where activated carbons are also employed is in the treatment of effluent or waste waters that derive from a broad range of manufacturing plants. Before this water can be discharged, it must be rendered free of toxic substances that can pollute natural water sources and the biochemical oxygen demand that it would place on such systems must be limited. 

Use of granular activated carbon (GAC) is considered to be the best currently available technology for removing low-solubility contaminants such as disinfection by-products (usually from chlorination) that include trihalomethanes (THM), detergents, pesticides, herbicides, polyaromatic hydrocarbons, and some trace metals. The amendments to the Safe Drinking Water Act. state that other treatment technologies must be at least as effective as GAC [66]. 

Most of the granular activated carbons u.sed in adsorber beds are produced from bituminous coal because their hardness, abrasion resistance, relatively high density, and pore size distributions render them suitable to withstand operating conditions and to adsorb the small organic molecules often present in drinking water. 

The best known and most widely encountered application of ion exchange is in the field of Water Treatment. It has been estimated that the Worldwide production of ion exchange resins is of the order of 500 000 m per annum of which probably in excess of 90% is employed in such water treatment processes shown collectively in Table 8.1. The majority of applications are for clean or natural water treatment as opposed to waste water or effluents which are waters made dirty by the inclusion of added chemicals and solids arising from manufacturing processes. Of course, natural waters are 

Softening Strong Acid Cation Weak Acid Cation Chelating 

Dealkalizing Weak Acid Cation Strong Base Anion 

Demineralizing Strong Acid Cation Weak Acid Cation Strong Base Anion Weak Base Anion 

Organic removal Strong Base Anion Weak Base Anion 

Cleaning plants may reqnire up to 2000 gal/ton of feed coal, although volumes of only half this quantity are now reqnired by the latest jig designs, which are the units in a coal cleaning plant that require the greatest quantities of water (Couch, 1991). 

Unless the coal being washed contains appreciable quantities of soluble salts, cleaning processes do not materially alter water composition. However, difhculties may be encountered when iron carbonates and pyrite and pyrite are present, particularly if the coal passes through stockpiles that allow some oxidation of the iron salts. The contamination is usually indicated by a substantial lowering of pH, from a normal range of 6-7.5 to values of 3 or even less, and may necessitate addition of alkali (caustic soda or lime) to restore near-neutral conditions. This type of problem is not often encountered and the nsnal type of water treatment involves clarification to remove suspended salts (slime) after which the water may be recirculated. 

Clarification may be partially achieved using batteries of small-diameter hydrocyclones (see above) to remove particles down to about 50 pm (Couch, 1991). Complete water clarification requires settling in cones and static thickeners, in conjunction with chemical dosing to promote flocculation and rapid settling. 

Calcium limestones are used as a closely graded granular filter medium (e.g., 0.71 to 1.25 mm and 1.6 to 2.8 mm) [12.34]. The physical requirements are described in [12.35]. As a filter medium, it has the advantage that it can neutralise acidic water 

Abrasive (mild) - detergent cleaners Floor coverings tiles - asphalt 

Antacids (alkalisers) Medicines - anti-acid powders 

Baking - flour additive Neutralisation of acid pickling baths etc.  

Brewing - control of acidity Paint - filler extender 

Where manufacturing plants for the pol5mierisation of E-PVC and S-PVC are located side by side, it is common for them to share the same water treatment facilities. 

Any water which may be contaminated with VCM, for example water used for the cleaning of reactors containing VCM, transfer lines and suspension or latex stock tanks, must be passed through a water stripper to remove VCM. This may be either continuous, consisting of a packed column or a column equipped with trays, or be a batch process. The VCM removal is optimised by the correct combination of residence time and temperature. The removed VCM is sent to the recovery plant and the aqueous effluent to a water treatment facility. 

Some sites also use membrane filtration to recover the product and to recycle water. PVC separated from waste water is mostly sold, maybe as a lower quality product [27, TWGComments, 2004]. 

Polyvinylidene chloride (PVDC) and polyvinyl alcohol (PVA) microspheres were carbonized on ceramic membrane to fabricate activated carbon membrane for coke furnace wastewater treatment [15]. A ceramic tube was dipped into a polymer latex containing 70 wt% PVDC and PVA microspheres of 0.10-0.15 pm to form aggregates of polymeric microspheres on and within (within pores of) the ceramic pipe. The precinsor was heated at 300°C and further to 750°C for carbonization. Major decomposition of the polymeric precursor seems to occur at 300°C. By nitrogen adsorption applying Horvath and Kowazoe method the membrane was found to have micropores of 0.7-0.8 run in diameter and meso-pores of 2-20 nm. Hence, the membrane has bimodal pore size distribution. The molecular weight cutoff of the membrane was ca. 10,000 Dalton. 

The immobilization of biofilms on permeable membranes, for the biodegradation of pollutants has drawn increasing interest for applications, where conventional treatment technologies are difficult to apply. As one of such examples, Hu et al. demonstrated the usefulness of membrane aerated biofilm reactor (MABR) for the wastewater treatment [16] a carbon-membrane aerated biofilm reactor (CMABR) was constmcted to remove organics and nitrogen containing compounds simultaneously in one reactor. 

9 Applications of Carbon-based Membranes for Separation Purposes 

The reactor feed contained glucose and ammonium chloride as the sources of organic carbon and nitrogeneous component. In addition, the feed contained a small amount of minerals as element nutrition. The experimental membrane bioreactor contained 16 carbon tubes of length 20 cm with inner and outer diameter of 4.7 and 8.9 mm, respectively. The pore size was 2 pm. To enhance the bacterial attachment the shell side surface of the carbon membrane was covered with nonwoven material, 

The CMABR (2.4 L) is schematically shown in Fig. 9.22. Complete mixing of the feed is ensured by the recirculation of the feed mixture by a magnetic pump, while the influent was supphed from the reactor bottom by a peristaltic pump. The effluent is discharged from the top of the reactor. Air was supphed from the top of the reactor into the lumen side of the carbon tubes. A part of the air permeated through the carbon membrane tube to the shell side and reacted with the biofilm The rest was emitted from the bottom of the reactor. The reactor was maintained at 32°C by heating and also kept dark. The reactor was operated according to the operational scheme given in Table 9.4. 

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The utility system also creates waste through products of combustion from boilers and furnaces and wastewater from water treatment, boiler blowdown, etc. Utility waste minimization is in general terms a question of ... 

Once injection water treatment requirements have been established, process equipment must be sized to deal with the anticipated throughput. In a situation where water injection is the primary source of reservoir energy it is common to apply a voidage replacement policy, i.e. produced volumes are replaced by Injected volumes. An allowance above this capacity would be specified to cover equipment downtime. 

Oxygen Scavenger Corrosion Inhibitor Figure 10.23 Injection water treatment scheme... 

Keywords production decline, economic decline, infill drilling, bypassed oil, attic/cellar oil, production potential, coiled tubing, formation damage, cross-flow, side-track, enhanced oil recovery (EOR), steam injection, in-situ combustion, water alternating gas (WAG), debottlenecking, produced water treatment, well intervention, intermittent production, satellite development, host facility, extended reach development, extended reach drilling. 

As a field matures, bottlenecks may appear in other areas, such as water treatment or gas compression processes, and become factors limiting oil or gas production. These issues can often be addressed both by surface and subsurface options, though the underlying justification remains the same the NPV of a debottlenecking exercise (net cost of action versus the increase in net revenue) must be positive. 

If extra treatment capacity is not cost effective another option may be to handle the produced water differently. The water treatment process is defined by the production stream and disposal specifications. If disposal specifications can be relaxed less treatment will be required or, a larger capacity of water could be treated. It is unlikely that environmental regulators will tolerate an increase in oil content, but if much of the... 

If gas export or disposal is a problem gas re-injection into the reservoir may be an alternative, although this implies additional compression facilities. Gas production may be reduced using well intervention methods similar to those described for reducing water cut, though in this case up-dip wells would be isolated to cut back gas influx. Many of the options discussed under water treatment for multi-layered reservoirs apply equally well to the gas case. 

The role that a host facility plays in an incremental development project can vary tremendously. At one extreme all production and processing support may be provided by the host (such as gas lift and water treatment). On the other hand, the host may just become a means of accessing an export pipeline (if a production and processing facility is installed on the new field). 

The nitration of phthalic anhydride with a mixture of concentrated sulphuric and nitric acids yields a mixture of 3-nitro- and 4 nitro phthalic acids these are readily separated by taking advantage of the greater solubility of the 4 nitro acid in water. Treatment of 3 nitrophtlialic acid with acetic anhydride gives 3 nitrophthahe anhydride. 

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