Liquid waste streams

Applicability This process is applicable to liquid (pumpable) organic wastes and finely divided, fluidizable sludges. It may be particularly applicable to the processing of liquid wastes with a high chlorine, pesticide, PCB or dioxin content. Sludges must be capable of being fluidized by the addition of a liquid. Waste streams must be free of (or preprocessed to remove) solids, which prevent satisfactory atomization. 

To remove the metals effectively so as to produce a liquid waste stream capable of reuse or finally meeting environmental discharge limits... 

Mixed fertilizer (subcategory G) treatment technology consists of a closed-loop contaminated water system, which includes a retention pond to settle suspended solids. The water is then recycled back to the system. There are no liquid waste streams associated with the blend fertilizer (subcategory G) process, except when liquid air scrubbers are used to prevent air pollution. Dry removals of air pollutants prevent a wastewater stream from being formed. 

ADTECHS Corporation (ADTECHS) has developed the radionuclides separation (RASEP) process for the removal and stabilization of radionuclides from liquid waste streams. The process uses filtration, selective adsorption, and electrodeposition fixation followed by cement sohdifi-cation. According to the vendor, the technology is commercially available. 

Table 10.2 Comparison of process liquid waste streams.

For an efficient absorption tower design, the plant should emit tail gases at less than 1000 ppm of nitrogen oxides. This level is about half the current emissions limit in Western Australia. Should emissions exceed this figure, then consideration must be given to the installation of a catalytic tail-gas combustor which enables emission levels to be lowered below 400 ppm. The plant does not normally produce any liquid waste streams (see Section 5.4.7 Environmental Impact Analysis). 

Fortunately the single-pressure nitric acid plant is a remarkably clean plant. It has no liquid waste streams in normal operation and... 

The plant is found to be highly efficient with a reaction yield of approximately 95%. Effluent levels from the process are small. There are no liquid waste streams and the tail gas should contain less than 1000 ppm of nitrogen oxides. 

Utilization of plutonium in early research and commercial orders to fabricate thermal recycle and fast breeder fuels did not coincide in timing with Pu availability from different sources. The plutonium comes mainly from high-exposure light-water reactor fuel reprocessing extended storage of this Pu as a nitrate solution leads to 241 contents up to 3%. For hands-on operation with this material it is necessary to reduce the Am content to about 0.5%. It was also necessary to minimize the liquid waste streams from the plant. In designing a technical-scale process, it was... 

Many of these wastes are effectively disposed of during operations. However, current permit requirements and other process limitations have resulted in significant quantities of these wastes accumulating on-site. Hydrolysate from the neutralization of the VX stockpile at Newport, a unique liquid waste stream among the wastes generated at the active chemical agent disposal facility sites, has also accumulated on-site. Specific quantities, issues, and comparisons associated with each of the main waste streams generated at the active disposal facilities are detailed in the remainder of this chapter. 

The liquid waste stream from the first step of the VX neutralization process at NECDF is called hydrolysate. Hydrolysate is the solution resulting from the treatment of the VX agent with an aqueous NaOH solution. It is a high-pH mixture that consists of two phases, aqueous and organic. The organic phase may represent up to 5 percent by volume of the total mixture. This hydrolysate process waste stream must be destroyed for compliance with the Chemical Weapons Convention treaty (NRC, 1998). Approximately 33 percent of the original VX stockpile at NECDF has been neutralized as of January 2007, resulting in the accumulation... 

No continuous liquid waste stream to treat—the water separated in the product purification section is recycled back to the aqueous MAH scrubber (2). 

The stabihzation of a range of contaminants, including Cr , in Ceramicrete was demonstrated by Wagh et al. [60] with two liquid waste streams that simulated radioactive supernatant and sludge from Hanford tanks within the DOE complex. These waste streams... 

Kentish SE and Stevens GW. Innovations in separations technology for the recycling and re-use of liquid waste streams. Chem Eng 7 2001 84 149-159. 

Liquid waste streams with a high-suspended solids content can be cleaned up by solids removal in clarifiers, thickeners, and liquid cyclones and by accelerated settling by inclined Chevron settlers or the like [73]. For waste streams with very finely divided solids in suspension (i.e., less than about 100 pm) dissolved air flotation techniques have been shown to be more efficient than methods employing sedimentation. Final dewatering of the sludges obtained may be carried out on a continuous filter or a centrifuge. The clarified water product can be accepted for more potential options of reuse or final disposal options than untreated water, and the separated solids may be burned or discarded to landfill, as appropriate [74]. 

Liquid waste streams containing an insoluble liquid can arise from extraction processes, from steam ejectors operating on solvent distillation systems, or from the loss of heat exchange fluid from a heat exchanger. These should be phase-separated before final disposal measures are undertaken. A simple settler, or a unit such as an American Petroleum Institute (API) separator can be used to accomplish this step. Coupling the initial separator to an entrained or dissolved air flotation unit can reduce the concentration of residual organics further [75]. The recovered organics can be recycled via a further cleanup if required, and the water phase more safely discarded. 

The components of most refinery liquid waste streams are recovered and reused, whenever feasible. Unfortunately, some of these, such as aqueous caustic phenolic or caustic sulfidic wastes, do not lend themselves readily to reuse. Deep well disposal, incineration, or precipitation in some manner and landfilling of the separated solids are the measures used in these instances. Raising the concentration of brine streams by reverse osmosis before discharge can help decrease final disposal costs by decreasing the waste volume [78]. 

New methods are focused on the preparation of solid catalysts without release of gaseous or liquid waste streams. In zeolite synthesis, the chemical compounds generated during combustion of templates (structure-directing agent) are often hazardous and harmful to the environment. A new method teaches disassembling the template within zeolite pore space into small fragments without combustion. ... 

One common step is to divide the gaseous and liquid waste streams into two separate waste streams, acidic and nonacidic, handled separately. Nonacidic gaseous waste streams from units, such as the dehydrogenation unit, or the acid-free section of the detergent alkylation unit, typically are combined and sent directly to a nonacid flare system where they are disposed of by burning. 

An acidic liquid waste stream originates from the HF acid regenerator bottoms. This material is neutralized, after which the hydrocarbon portion (heavy... 

Similarly use of cobalt acetate-manganese acetate as a catalyst for the oxidation processes of p-cresol to p-hydroxy benzaldehyde or 3,4,5-trimethoxy benzaldehyde will generate waste streams from which co-acetate and Mn-acetate are to be recovered and recycled. Use of other catalysts for other processes will similarly generate waste liquid streams containing unused surplus catalysts or as converted salts which need to be processed and make the liquid waste stream as much free from inorganic impurities as possible. Not only from ecologi-cal/environmental points of view, this is necessary but also commercially this will make the operations more viable and attractive. 

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