Waste aqueous, treatment

The capital cost of most aqueous waste treatment operations is proportional to the total flow of wastewater, and the operating cost increases with decreasing concentration for a given mass of contaminant to be removed. Thus, if two streams require different treatment operations, it makes no sense to mix them and treat both streams in both treatment operations. This will increase both capital and operating costs. Rather, the streams should be segregated and treated separately in a distributed effluent treatment system. Indeed, effective primary treatment might mean that some streams do not need biological treatment at all. 

Although the PO WW ER system can treat concentrated and dilnte aqueous wastes, treatment of dilute aqueous waste may require increased energy (however, brine disposal costs will be lower). Also, the PO WW ER system can treat a broad range of mixed aqneons waste streams, but the specific characteristics of the wastewater to be treated can affect the performance of the system. In addition, the pH and ionic strength of the waste stream, contaminant loading, nature of the contaminants, foaming, and catalytic poisons can all affect system performance. 

Preparation, Analysis and Behaviors of Ti-Based SnC>2 Electrode and the Function of Rare-Earth Doping in Aqueous Wastes Treatment... 

Nine hazardous waste incinerators that are operating commercially in the United States might be available, two each in Texas and Ohio, and one each in Arkansas, Illinois, Kentucky, Nebraska, and Utah. The largest commercial hazardous aqueous waste treatment facility in the United States is managed by DuPont in Deepwater, New Jersey. It provides a combination of physical, chemical, and biological treatment. Clean Harbors, in Baltimore, uses supercritical fluid extraction to treat aqueous wastes. Perma-Fix, with facilities in the Southeast and Midwest, uses proprietary aqueous treatment processes tailored to specific waste streams. 

Microbiological corrosion in the process industries is most often found in three areas cooling water systems, aqueous waste treatment, and gronndwater left in new equipment or piping systems after testing. Nearly all confirmed cases of MIC have been accompanied by characteristic deposits. These are usually discrete mounds. Deposit color can also be an indication of the types of micro-organisnis that are active in the system. For example, iron bacteria deposits on stainless steel, such as those produced by Gallionella, are often reddish. 

While incineration is the preferred method of disposal for wastes containing high concentrations of organics, it becomes expensive for aqueous wastes with low concentrations of organics because auxiliary fuel is required, making the treatment expensive. Weak aqueous solutions of organics are better treated by wet oxidation (see Sec. 11.5). 

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. 

Prepare the aqueous waste for biological treatment by removing excessive load or components that will inhibit the biological processes. 

Tertiary treatment. Tertiary or polishing treatment prepares the aqueous waste for final discharge. The final quality of the effluent depends on the nature and flow of the receiving water. Table 11.3 gives an indication of the final quality required. ... 

The treatment of aqueous wastes was also taken in account. 

Aqueous work-up of the typical Grignard reaction gives a mixed magnesium hydroxide—haUde solution or suspension which must be disposed of. The cost of disposal of the acidic aqueous waste in accordance with local wastewater treatment regulations must also be considered. 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Aqueous Eva.pora.tlon. Aqueous evaporation for hazardous waste treatment can be accompHshed in a closed process vessel that uses steam to evaporate the Hquid into a water vapor, which is ultimately condensed and may be reused, as shown in Figure 5. The concentrated Hquid is coUected for further treatment or disposal. 

Wet Air Oxidation. With wet air oxidation, increased temperature and pressure are used to oxidize dilute concentrations of organics and some inorganics, such as cyanide, in aqueous wastes that contain too much water to be incinerated, but are too toxic to be treated biologically. In general, wet air oxidation provides primary treatment for wastewaters that are subsequendy treated by conventional methods. This technology can be used with wastes that are pumpable (slurries andUquids). 

Inorganic heavy metals are usually removed from aqueous waste streams by chemical precipitation in various forms (carbonates, hydroxides, sulfide) at different pH values. The solubiUty curves for various metal hydroxides, when they are present alone, are shown in Figure 7. The presence of other metals and complexing agents (ammonia, citric acid, EDTA, etc) strongly affects these solubiUty curves and requires careful evaluation to determine the residual concentration values after treatment (see Table 9) (38,39). 

Hydrotheimal oxidation (HO) (also called supercritical water oxidation) is a reactive process to separate aqueous wastes into water, CO9, nitrogen, salts, and other byproducts. It is an enclosed and complete water-treatment process m ng it more desirable to the public than incineration (Fig. 22-25) (Tester et al., op. cit. Gloyna and Li,... 

A 3 Gaseous (gases, vapors, airborne particulates) W = Wastewater (aqueous waste) B11 Biological Treatment - Aerobic... 

L = Liquid waste (non-aqueous waste) B21 Biological Treatment - Anaerobic... 

Guide to Discharging CERCLA Aqueous Wastes to Publicly Owned Treatment Works (POTWs), March 1991 NTIS PB91-219364 Handbook for Monitoring Industrial Wastewater, August 1973 625/6-73-(X)2 ERIC W318 NTIS PB-259146. 

Flocculation and sedimentation arc two processes used to separate waste streams that contain both a liquid and a solid phase. Both are well-developed, highly competitive processes, which arc oflcii used in the complete treatment of waste streams. They may also be used instead of, or in addition to, filtration. Some applications include the removal of suspended solid particles and soluble heavy metals from aqueous streams. Many industries use both processes in the rcmowal of pollutants from their wastewaters. These processes work best when the waste stream contains a low concentration of the contaminating solids. Although they are applicable to a wide variety of aqueous waste streams, these processes arc not generally used to treat nonaqueous or semisolid waste streams such as sludges and slurries. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

Figure 2. Aqueous waste recovery and treatment processes (broken lines represent processes under development).

Waste Treatment. Figure 2 outlines the current waste recovery and treatment processes, and proposed changes. Acid waste streams are sent through nitric acid and secondary plutonium recovery processes before being neutralized with potassium hydroxide and filtered. This stream and basic and laundry waste streams are sent to waste treatment. During waste treatment, the actinides in the aqueous waste are removed by three stages of hydroxide-iron carrier-flocculant precipitation. The filtrate solution is then evaporated to a solid with a spray dryer and the solids are cemented and sent to retrievable storage. 

---