Environmental considerations wastewater treatment

Due to environmental considerations, many phenol plants are equipped with a special water treatment faciUty where acetone and phenol are recovered from the wastewater stream. Also, recovered heavy residue is considered a K-022 waste material by the U.S. EPA and must be properly disposed of by incineration or other means (12). 

The solids that result from wastewater treatment may contain concentrated levels of contaminants that were originally contained in the wastewater. A great deal of concern must be directed to the proper disposal of these solids to protect environmental considerations. Failure to do this may result in a mere shifting of the original pollutants in the waste stream to the fmal disposal site where they may again become free to contaminate the environment and possibly place the public at risk. A more reasonable approach to ultimate solids disposal is to view the sludge... 

One of the interesting features of the two-phase digestion process is that it can be retrofitted to an existing anaerobic digestion plant to effectively double its treatment capacity at a considerably reduced capital cost compared to the cost of a grassroots plant of the same additional incremental capacity. The U.S. Environmental Protection Agency s projection of new anaerobic digestion capacity needed in the United States for municipal wastewater treatment in... 

Separation science plays a pivotal role in many hydromet-allurgical processes, inclnding industrial wastewater treatment [1-7]. Ont of the various separation techniques, solvent extraction, ion exchange, and precipitation are the workhorse for various industrial applications. At the same time, there is a growing interest in membrane-based separation methods that are considered environmentally benign [7-10]. A combination of membrane separation and solvent extraction techniques, known as the liquid membrane (LM) technique, has drawn considerable attention for the separation scientists and technologists. LM-based separation methods are associated... 

Over the years, the precipitation of iron oxides and hydroxides from acidic solutions has received considerable attention in various fields, such as catalyst synthesis, environmental sciences and industrial processes [e.g. 22-29]. Freshly formed iron hydroxide particles help to control pollution in aquatic systems, e.g. by fixation and transport of phosphates, heavy metals and other reactive inorganic and/or organic species [30-33]. The high reactivity of these iron phases is mainly due to their small size. The formation and aggregation of iron colloids, which occurs in continental and marine aquatic systems [22, 34-38], is also employed in water and wastewater treatments [35, 39,40]. 

Environmental requirements are assuming great importance, since there is an increased interest in the industrial use of renewable resources such as starch and chitin. Considerable efforts are now being made in the research and development of polysaccharide derivatives as the basic materials for new applications. In particular, the increasing cost of conventional adsorbents undoubtedly makes chitin and chitosan-based materials one of the most attractive biosorbent for wastewater treatment. Chitin and chitosan biopolymers have demonstrated outstanding removal capabilities for certain pollutants such as dyes and metal ions as compared to other low-cost sorbents and commercial-activated carbons. Biopolymer adsorbents are efficient and can be used for the decontamination of effluents (removal of pollutants) and for separation processes (recovery of valuable metals). 

Concerns about municipal solid waste (MSW), defined by the U.S. Environmental Protection Agency as including residential, institutional, office, and commercial waste, but not including construction and demolition debris, wastewater treatment sludge, and industrial waste, stem from three main considerations. One is the amount of space occupied by the waste—space that therefore is not available for other uses. Another is the resources that... 

Abstract The potential fields of application of biocatalytic membrane reactors have widened considerably in recent years. Although biocatalytic membrane reactors, in general, are yet to achieve broad industrial application, in the not too far future they are expected to play a major role, not only for the production, transformation and valorization of raw materials but also for environmental remediations. This chapter comprehensively reviews the laboratory scale studies which demonstrate the potential of biocatalytic membrane reactors in wastewater treatment applications. Studies reported in the Mterature, however, serve as proof of concept only. Issues that need to be addressed in order to achieve scale-up of such systems have been discussed in this chapter. 

Environmental Factors These inchrde (I) eqrripment location, (2) available space, (3) ambient conditions, (4) availabuity of adeqrrate rrtilities (i.e., power, water, etc.) and ancillary-system facilities (i.e., waste treatment and disposal, etc.), (5) maximrrm aUowable emission (air polhrtion codes), (6) aesthetic considerations (i.e., visible steam or water-vapor phrme, etc.), (7) contribrrtions of the air-poUrrtion-control system to wastewater and land poUrrtion, and (8) contribrrtion of the air-poUrrtion-control system to plant noise levels. 

Replacement of hexavalent chromium with trivalent chromium offers important environmental advantages. Trivalent chromium is considerably less toxic than hexavalent. Trivalent systems use chromium concentrations that are typically two orders of magnitude less than in hexavalent systems. Thus, far less chromium enters the waste stream. Trivalent systems also generate few toxic air emissions, while hexavalent systems involve a reaction that produces hydrogen bubbles which entrain chromium compounds and carry them out of the baths. Trivalent chromium is readily precipitated from wastewater, while hexavalent chromium solutions must go through an additional step in a treatment system in which the chromium is reduced to its trivalent form before precipitation. It has been shown that trivalent chromium systems can successfully replace hexavalent ones for decorative chrome applications. Trivalent chromium systems are not suitable for hard chrome applications. More information regarding trivalent chromium plating can be obtained from Roy (1984), Robison (1978), Chementator (1982), and Smart (1983). 

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