Utilities wastewater treatment

Miscellaneous. Hydrochloric acid is used for the recovery of semiprecious metals from used catalysts, as a catalyst in synthesis, for catalyst regeneration (see Catalysts, regeneration), and for pH control (see Hydrogen-ION activity), regeneration of ion-exchange (qv) resins used in wastewater treatment, electric utiUties, and for neutralization of alkaline products or waste materials. In addition, hydrochloric acid is also utilized in many production processes for organic and inorganic chemicals. 

The pulp and paper industry and potable and wastewater treatment industry are the principal markets for aluminum sulfate. Over half of the U.S. aluminum sulfate produced is employed by the pulp and paper industry. About 37% is used to precipitate and fix rosin size on paper fibers, set dyes, and control slurry pH. Another 16% is utilized to clarify process waters. The alum sold for these purposes is usually Hquid alum. It is frequendy acidic as a result of a slight excess of H2SO4. Aluminum sulfate consumption by the pulp and paper industry is projected to remain constant or decline slightly in the near term because of more efficient use of the alum and an increased use of alkaline sizing processes (13). 

Fig. 2. Typical flow sheet for a domestic wastewater treatment plant utilizing the activated-sludge process.

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. 

Much of the experience and data from wastewater treatment has been gained from municipal treatment plants. Industrial liquid wastes are similar to wastewater but differ in significant ways. Thus, typical design parameters and standards developed for municipal wastewater operations must not be blindly utilized for industrial wastewater. It is best to run laboratory and small pilot tests with the specific industrial wastewater as part of the design process. It is most important to understand the temporal variations in industrial wastewater strength, flow, and waste components and their effect on the performance of various treatment processes. Industry personnel in an effort to reduce cost often neglect laboratory and pilot studies and depend on waste characteristics from similar plants. This strategy often results in failure, delay, and increased costs. Careful studies on the actual waste at a plant site cannot be overemphasized. 

Blowdown systems utilize a series of flash drums and condensers to separate the blowdown into its vapor and liquid components. The liquid is typically composed of mixtures of water and hydrocarbons containing sulfides, ammonia, and other contaminants, which are sent to the wastewater treatment plant. 

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... 

ATP measured by luciferin-luciferase BL assay was used to examine the effect of toxic substances on whole microbial communities in activated sludge mixed liquid samples [114], It was used to detect whether wastewater had an effect on the biodegradation capability of the resident population of microorganisms. Actually ATP BL represents an important rapid toxicity test that utilizes waste treatment natural microorganisms to determine the toxicity of wastes discharged to the sewer [132],... 

Because FMs are semivolatile, they are amenable to analysis by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) without derivitization. Table 2 shows that all of the analytical methods developed to measure FMs in wastewater treatment to date utilize GC or GC-MS. 

CDD/Fs presence in municipal wastewater treatment plant (MWTP) influents results in the PCDD/Fs presence in effluents and sludge. Evidence of polychlorinated dibenzo-p-dioxins and dibenzofurans formation within the MWTP was also found. All this aspects are discussed in the paper, with special attention to sewage sludge, because of further utilization demand according to EU directives. 

As mentioned, RMP addresses specific chemicals/materials (compounds) it addresses the accidental release of over one hundred chemical substances. Of the RMP chemicals listed, seventy-seven include acutely toxic chemical compounds and sixty-three flammable gases. Threshold quantity levels range from 500 pounds to 20,000 pounds. USEPA estimates that approximately 100,000+ sources are covered by the rule. The universe includes chemical and most other manufacturers, certain wholesalers and retailers, drinking-water systems, wastewater treatment works, ammonia refrigeration systems, chemical wholesalers and end users, utilities, propane retailers, and federal facilities. 

Auxiliary processes. Refineries also have other processes and units that are vital to operations by providing power, waste treatment, and other utility services, such as boilers, wastewater treatment, and cooling towers. Products from these facilities are usually recycled and used in other processes within the refinery and are also important with regard to minimizing water and air pollution. 

Wastewater is treated in on-site wastewater treatment facilities and then discharged to publicly owned treatment works (POTWs) or discharged to surface waters under National Pollution Discharge Elimination System (NPDES) permits. Petroleum refineries typically utilize primary and secondary wastewater treatment. 

Since they cannot utilize light energy, the decomposition of organic substrates is incomplete. Further decomposition of the acetic acid is not possible under anaerobic conditions. Nevertheless, these reactions are still suitable for the initial steps of wastewater treatment and hydrogen production, followed by further waste treatment stages. 

Although there are some applications in gas emissions reduction, for example, hydrogen sulfide and ammonia removal by utilizing carboxylic acid resins and ammonium anion-exchange resins, ion exchange is mainly used in wastewater treatment. Some characteristic environmental applications are the following (Noble and Terry, 2004) ... 

The examination of the total reagent usage in the two processes (last row in Table 8.3) clearly shows that the new enzymatic route (with recycling of 4) utilizes 7 times less input of chemicals. This includes 12 times less input of solvents as compared to the first-generation route. Moreover, in the optimized process, every chemical reaction is run in water with minimal solvents used for work-up. Some of the process water can be sent directly to the wastewater treatment plant, and the solvent from the hydrolysis/decarboxylation process is recovered. Further improvements from pilot plant and production scale runs have been demonstrated and will be implemented in the future. 

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