Wastewater economics

Reichold Chemicals, Inc. This University of Alabama case study deals with wastewater treatment problems at the company s Tuscaloosa plant. In addition to the emphasis on the methods for treating wastewater, economic, social, and community issues are raised. Although dated, this study provides a basis for considering alternate methods for the manufacture of phenol, the associated pollution problems, and community concerns. 

GTC Technology Carboxylic acid Acld-contalning aqueous steams Liquid-liquid extraction technology is combined with distillation to recover and concentrate carboxylic acids from wastewater. Economic for any aqueos stream generated by producing DMT, PTA, pulp/paper, furfural and other processes 2 NA... 

Method of synthesis produced by biosynthesis by bacteria and plants in response to physiological stress also Haloarcula sp. can be used to produce PHB from petrochemical wastewater economical high scale production from glycerol Is feasible Taran, M, J. Hazardous Mater., 188, 26-28,2011 Posada, J A Naranjo, J M Lopez, J A Higuita, J C Cardona, C A, Process Biochem., 46, 310-17,2011. 

Produce large amount of industrial wastewater Economically viable to compete with commercial petro-base diesel fuel... 

As the economic value of coproducts has decreased, it has become more difficult to provide capital for environmental controls on air emissions and wastewater streams such as toxic phenoHc effluents from chemical recovery operations. Some former coke and manufactured gas sites may require remediation to clean up contaminated soil and groundwater. These difficulties will force the shutdown of some operations and discourage recovery of coproducts in future installations. 

Whereas many of these technologies are not really new, they have never had the regulatory and economic justification for their use in metallizing. Each of these general methods has many variants. Some may be directed to waste treatment, some to recycle, and some to reclaim. An example is filtration, used to prevent release to air of zinc particles from flame spraying, microfiltration of cleaners to extend hfe, in combination with chemical precipitation to remove metal particles from wastewater, and many other uses. 

Lagoons. Where large land areas are available, lagooning provides a simple and economical treatment for nontoxic or nonhazardous wastewaters. There are several lagoon alternatives. 

A notable example of controlled water reuse was utilization of secondary sewage effluent from the Back River Wastewater Treatment Plant in Baltimore by the Sparrows Point Works of Bethlehem Steel (6). The Sparrows Point plant was suppHed primarily by weUs located near the brackish waters of Baltimore harbor. Increased draft on the weUs had led to saltwater intmsion. Water with chloride concentration as high as 10 mg/L is unsuitable for many steelmaking operations. Rollers, for example, are pitted by such waters. However, treated effluent from the Back River Plant can be used for some operations, such as coke quenching, and >4 x 10 m /d (10 gal/d) are piped 13 km to Sparrows Point. This arrangement has proved economical to both parties for >40 yr. 

Water can seldom be reused directiy. The treatment required depends on the intended second use. Disposal costs of the wastewater must be included in any economic analysis, and additional treatment for reuse may be justified when this expense is included. Costs of reclamation depend on the location, water scarcity, availabiUty of pubHc water suppHes, and the intended reuse. 

Chlorination was found (172) to be the most suitable and effective method for decolori2ing and reducing the COD of waste dyebaths containing a2o dyes. These findings have been substantiated for chlorination and biochemical purification (173). A study (174) has been done on the technical and economic feasibiUty of a chlorination dye wastewater reclamation system for treating effluent that is suitable for reuse in dyeing of polyester/cotton blends with disperse and direct dyes. 

Liquid-liquid extraction is used primarily when distillation is imprac-tic or too costly to use. It may be more practical than distillation when the relative volatility for two components falls between 1.0 and 1.2. Likewise, liquid-liquid extraction may be more economical than distillation or steam-stripping a dissolved impurity from wastewater when the relative volatility or the solute to water is less than 4. In one case discussed by Robbins [Chem. Eng. Prog., 76 (10), 58 (1980)], liquid-liquid extraction was economically more attractive than carbon-bed or resin-bed adsorption as a pretreatment process for wastewater detoxification before biotreatment. 

Extraction from Aqueous Solutions Critical Fluid Technologies, Inc. has developed a continuous countercurrent extraction process based on a 0.5-oy 10-m column to extract residual organic solvents such as trichloroethylene, methylene chloride, benzene, and chloroform from industrial wastewater streams. Typical solvents include supercritical CO9 and near-critical propane. The economics of these processes are largely driven by the hydrophihcity of the product, which has a large influence on the distribution coefficient. For example, at 16°C, the partition coefficient between liquid CO9 and water is 0.4 for methanol, 1.8 for /i-butanol, and 31 for /i-heptanol. 

Economic data, including cost of raw material management cost of air, wastewater, and hazardous waste treatment waste management operating and maintenance costs and waste disposal costs... 

Tighter control of water use can reduce the volume of wastewater requiring treatment, and result in cost savings - it can sometimes reduce volumes and increase concentrations to the point of providing economic material recovery in place of costly wastewater treatment. 

The technology that competes with ion exchange in wastewater application is reverse osmosis (RO), therefor it is appropriate to make some comparisons. Direct cost comparisons are not straightforward, and requires comparison of some of the hidden cost parameters. Since there appear to be few detailed comparisons in the open literature, there exists the general impression that RO is more economical than ion exchange. Whereas this may be true in a number of applications, as a general rule this is not the case. 

Air stripping is used to remove 90% of the toluene (molecular weight = 92) dissolved in a 10 kg/s (159 gpm) wastewater stream. The inlet composition of toluene in the wastewater is 500 ppm. Air (essentially free of toluene) is compressed to 202.6 kPa (2 atm) and bubbled through a stripper which contains sieve trays. In order to avoid fire hazards, the concentration of toluene in the air leaving the stripper is taken as 50% of the lower flammability limit (LFL) of toluene in air. The toluene-laden air exiting the stripper is fed to a condenser which recovers almost all the toluene. A schematic representation of the process is shown in Fig. 2.11. Calculate the annual operating cost and the fixed capital investment for the system. The following physical and economic data are available ... 

Hafez A, Khedr M, Gadallah H (2007) Wastewater treatment and water reuse of food processing industries. Part II Techno-economic study of a membrane separation technique. Desalination 214 261-272... 

Many of the waste streams from U.S. process industries are water containing small quantities of metal ions that the law requires be removed before the wastewater is disposed of There is an economic incentive to recoup at least some of the cost of wastewater treatment by recovering and selling the metal content instead of merely disposing of the metals as sludge. Because the waste streams are dilute in desired materials, research is needed to devise efficient extraction and separation processes. 

Pyrolysis of scrap tires was studied by several mbber, oil, and carbon black industries [14]. Pyrolysis, also known as thermal cracking is a process in which polymer molecules are heated in partial or total absence of air, until they fragment into several smaller, dissimilar, random-sized molecules of alcohols, hydrocarbons, and others. The pyrolysis temperature used is in the range of 500°C-700°C. Moreover, maintenance of partial vacuum during pyrolysis in reactors lowered the economy of the process. Several patents were issued for the pyrolysis of worn out tires to yield cmde oil, monomers, and carbon black in economic ways [15-18]. The major drawback of chemical recycling is that the value of the output is normally low and the mixed oils, gases, and carbon black obtained by pyrolysis cannot compete with similar products from natural oil. Pyrolyzing plant produces toxic wastewater as a by-product of the operation [19]. 

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