Clarified effluent

Sedimentation Equipment. Centrifugal sedimentation equipment is usually characterized by limiting flow rates and theoretical settling capabihties. Feed rates in industrial appHcations may be dictated by Hquid handling capacities, separating capacities, or physical characteristics of the soHds. Sedimentation equipment performance is illustrated in Figure 8 on the basis of nominal clarified effluent flow rates and the appHcable values. The... 

In most water clarification or softening processes in which coagulation and precipitation occur, at least a portion of the clarified water is filtered. Clarifier effluents of 2—10 NTU may be improved to 0.1—1.0 NTU by conventional sand filtration. Filtration ensures acceptable suspended sohds concentrations in the finished water even when upsets occur in the clarification processes. 

Ravazzini AM, Nieuwenhuijzen AF, van der Graaf JHMJ (2005) Direct ultrafiltration of municipal wastewater comparison between filtration of raw sewage and primary clarifier effluent. Desalination 178 51-62... 

From the slow mix unit [T-100], the waste flows into the lamellar portion of the sedimentation clarifier [T-101].54 55 The lamella in the clarifier concentrates the metal hydroxide precipitates. Clarified effluent can be discharged to the sewer. 

Granular bed filters are used in ten coil coating plants to remove residual solids from the clarifier effluent, and are considered to be tertiary or advanced wastewater treatment. Chemicals may be added upstream to enhance the solids removal. Pressure filtration is also used in this industry to reduce the solids concentration in clarifier effluent and to remove excess water from the clarifier sludge. Figure 7.4 shows a granular bed filter and Table 7.13 presents the heavy metal removal data of a lime clarification and filtration system. 

Granular bed filters are used in porcelain enameling wastewater treatment to remove residual solids from clarifier effluent (sedimentation effluent or flotation effluent). Filtration polishes the effluent and reduces suspended solids and insoluble precipitated metals to very low levels. Fine sand and coal are media commonly utilized in granular bed filtration. The filter is backwashed after becoming loaded with solids and the backwash is returned to the treatment plant influent for removal of solids in the clarification step.10-12... 

In the recycle flow pressurization system (Figure 27.10), a portion (15-50%) of the clarified effluent from the flotation chamber is recycled, pressurized, and semisaturated with air in the air dissolving tube. The recycled flow is mixed with the unpressurized main influent stream just before admission to the flotation chamber, with the result that the air bubbles come out of aqueous phase in contact with suspended particulate matter at the inlet compartment of the flotation chamber. The system is usually employed in applications where preliminary chemical addition and flocculation are necessary and ahead of flotation. It eliminates the problems with shearing the flocculated particles since only the clarified effluent passes through the pressurizing pump and the friction valve. It should be noted, however, that the increased hydraulic flow on the flotation chamber due to the flow recirculation must be taken into account in the flotation chamber design. 

Conventional chemical treatment of metal finishing wastes will usually produce clarified effluent acceptable for discharge however, in those applications where it is desirable or necessary to recover the clarified rinse water for re-use, the technologies are utilized to purify or "desalt" the effluent for re-use. 

Membrane technologies can also be used in other parts of this total treatment system microfiltration could be substituted for the clarifier (see Figure 9), and reverse osmosis could purify the clarified effluent for re-use. 

Pressurization could be carried out on the entire feed stream (full-flow pressure flotation) or a fraction of the feed stream while the remainder is introduced directly without aeration into the flotation tank (split-flow pressure flotation). The spht-flow system offers a cost saving over the full-flow units, since only a portion of the influent needs to be pressurized. In both cases, however, if the sohd particles in the feed stream are flocculated before introducing to the flotation tank, the high shear during pressurization, aeration, and pressure release can destroy the floes. Also, if the particle loading in the feed stream is high, both systems are susceptible to block e of the air release devices. To minimize these problems, recycle-flow pressure flotation is often practiced (Fig. 19-71). In this process, the feed stream, flocculated or otherwise, is introduced directly into the process vessel, and part of the clarified effluent is pressurized, aerated, and recycled to the flotation tank in which it is mixed with the flocculated feed. The air bubbles are released as they attach to the floes and float to the tank surface. The recycle-flow devices are found to offer the highest unit capacities. 

Carbon adsorbents have traditionally been used for removal of coloration in the clarified effluent liquor. The general carbon adsorbents, which may be bone char, granular carbon, or powdered carbon products, are used in either a fixed-bed operation or a moving-bed process. These carbons are regenerated at intervals to maintain their effectiveness. 

Soluble iron or aluminum carryover in the clarifier effluent may result from inorganic coagulant use therefore, elimination of the inoiganic coagulant can minimize the deposition of these metals in filters, ion-exchange units, and cooling systems. 

Clarified Effluent The liquid being discharged from the flotation unit. 

Mound Facility Low-Risk Waste. Approximately 3 x 105 l of low-level waste are generated weekly at the Mound Facility. This particular waste stream is essentially local hard water which has been demineralized and then used in various chemical processes involving the radionuclides 238Pu and 233U. The first step in decontaminating the low-risk wastes entails addition of small amounts of calcium and iron salts followed by addition of NaOH to pH 11.5 to precipitate iron and calcium hydroxides and carbonates. The clarified effluent from the precipitation step is then passed through a 200 micrometer sand filter to yield a solution containing, typically, 0.1+ d/min/m alpha activity. 

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