Effluents, aqueous

The generation and treatment of aqueous contaminants is another aspect of coal liquefaction that must not be ignored. Major contaminants are hydrogen sulfide, anunonium sulfide, phenols, cresols, xylenols, and thiocyanates cyanides and solids (ash and char particles) may also be present. The gaseous contaminants (hydrogen sulfide and anunonia) are ranoved by steam-stripping. 

Waste-water treatment is a combination of processes for the treatment, recycling, and discharge of aqueous effluents (Table 25.4). 

Gaseous Emissions from Coal Liquefaction Processes 

Coal stwage and pretreatment Coal lock hopper 

Preheat, liquefaction preheater, hydrogen generation, hydrotreating, and solids-liquids separation Produce fractionation Catalyst regeneration 

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The process is designed from a knowledge of physical concentrations, whereas aqueous effluent treatment systems are designed from a knowledge of BOD and COD. Thus we need to somehow establish the relationship between BOD, COD, and the concentration of waste streams leaving the process. Without measurements, relationships can only be established approximately. The relationship between BOD and COD is not easy to establish, since different materials will oxidize at different rates. To compound the problem, many wastes contain complex mixtures of oxidizable materials, perhaps together with chemicals that inhibit the oxidation reactions. 

Problems of removal of mercury from aqueous effluents are more comphcated in plants that manufacture a variety of inorganic and organic mercury compounds it is generally best to separate the effluent streams of inorganic and organic mercurials. When phenyhnercuric acetate is precipitated from its solution in acetic acid by addition of water, the filtrate is collected and reused for the next precipitation. This type of recycling is necessary not only for economic reasons but also to minimise recovery operations. 

When an aqueous effluent stream containing organomercurials cannot be recycled, it may be treated with chlorine to convert the organomercury to inorganic mercury. The inorganic compounds thus formed are reduced to metallic mercury with sodium borohydride. The mercury metal is drained from the reactor, and the aqueous solution discarded. The process utilising sodium borohydride is known as the Ventron process (27). 

In the uranium-stripping step, a dilute HNO solution is used to remove uranium from the organic phase. The aqueous effluent containing the... 

With the ever increasing awareness of the need of environment protection, the emission of solvent vapors and organic fumes into the atmosphere should be prevented by treating the exhaust through a proper scmbber. The solvent used for cleaning the reactor is usually consumed as part of the thinning solvent. Aqueous effluent should be properly treated before discharge. 

Federal regulations (72) administered by the EPA estabHsh limitations on the ammonia in aqueous effluents on a site-specific basis. The range of values is 0.05—0.1875 kg of ammonia (as nitrogen) per ton of product on a maximum daHy basis corresponding 30-day average values range from 0.025 to... 

The reaction of aHyl chloride and chlorine ia water produces trichloropropane as a by-product even ia the aqueous phase, along with tetrachloropropyl ether. For maximum dichi orohydrin yield it is necessary to mn the reaction at low concentrations of chloride ion and of chlorohydrin, that is, with high water dilution. However, high dilution results ia an aqueous effluent that contains minor amounts of these by-products that require significant treatment to reduce them to levels acceptable ia outfalls to rivers, lakes, and other pubHc waterways. 

D. C. Baker, W. V. Bush, K. R. Loos, M. W. Potter, and P. F. Russell, "Environmental Characteri2ation of the Shell Coal Gasification Process. II. Aqueous Effluent," Sixth Annual Pittsburgh Coal Conference, Pittsburgh, Pa., Sept., 1989. 

The DMR process has no aqueous effluent, gives high purity products, and is less expensive. However, if hydrogen is produced, it has to be removed carefully and should not reach explosive limits. Not all metals are sufftcientiy reactive to be suitable for the DMR process. 

Liquid-solid Slurry Suspension Aqueous effluent from fume scrubbing... 

Strict control is necessary over pollutant levels, acidity, temperature, turbidity, etc. because of their impact upon aquatic environments. Common pollutants in aqueous effluents are identified in Table 16.11. 

Any of the variety of ehemieal engineering operations or unit proeesses listed in Table 17.10 may be used to treat aqueous effluents. Oxidation ineludes both ehemieal and biologieal proeesses the latter inelude triekling filters or an aetivated sludge bed. 

Residuals Produced The resulting residuals from a hydrolysis process are an aqueous effluent and insoluble organics. 

This chapter covers the design of facilities to handle equipment drainage and contaminated aqueous effluents that are sent for appropriate disposal blowdown drum systems to receive closed safety valve discharges, emergency vapor blowdowns, etc. and facilities for process stream diversion and slop storage. Also covered are criteria for selecting the appropriate method of disposal. Design of flares is covered in a subsequent chapter. 

The purpose of the facilities described in this chapter is to provide for safe handling of various drainage materials and emergency streams, so that they may be safely routed to the sewer, tankage, flare, or other appropriate destination. Drainage systems specified herein ensure that flammable or toxic materials may be disposed of without hazard of fire or injury when equipment is taken out of service. Also described are systems to handle process water drawoffs, cooling water, and other aqueous effluent streams which may be contaminated with hydrocarbons, and which could otherwise create hazardous conditions if they were discharged directly to the sewer. 

Because of the toxicity of CE, the aqueous effluent from the ethyl chloride reactor, Ri, causes significant problems for the bio-treatment facility. The objective of this case study is to optimally intercept CE-laden streams so as to reduce the CE content of R] to meet the following regulations ... 

These results can be used to construct the solution as shown in Fig. 7.14. The target for minimum CE discharge through segregation, mixing and direct recycle is 0.488 X 10 kg/s (about 15 kg/yr). The solution indicates that the optimal policy is to segregate the effluents of the two scrubbers, pass the effluent of the first scrubber to the reactor, recycle the aqueous effluent of the reactor to the hrst scrubber and dispose of the second scrubber effluent as the terminal wastewater stream. 

However, for water analysis, reverse-phase liquid chromatography is more suitable but its coupling with GC has some drawbacks because of the partly aqueous effluent. Several systems have been developed (88, 89) and applied to determine pollutants in water. 

C.A. Spano, R.A. Chulk, T.T. Walsh C. DiPietro, Abatement of Nitrobodies in Aqueous Effluents from TNT Production and Finishing... 

Table 13.8 identifies common pollutants in aqueous effluents. Of the metals, the most toxic are salts of the heavy metals beryllium, cadmium, chromium, copper, lead, mercury, nickel and zinc. 

Liquid Liquid Liquid-gas Liquid-liquid Liquid-solid Solution Foam Emulsions Slurry Suspension Metal plating effluent spent acids wash-waters Detergent foam Oil-in-water (e.g. suds) water-in-oil Aqueous effluent from fume scrubbing... 

Cold-pressed essential oils from the peel are some of the most important by-products recovered during the processing of Citrus fruits. The presence of limonene in the aqueous discharges, with its antimicrobial activity [1], decreases the effectiveness of the waste treatment system and increases the time necessary for the biological breakdown of the organic matter produced in the peel oil recovery system [2,3]. Additional recovery of essential oils from waste water would increase industry s returns and reduce the pollution problems associated with the disposal of waste water [4,5]. Several methods for reducing the levels of residual essential oils in the aqueous effluent have been developed over the years [6-11]. 

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