Bath water, reusing

Diluted or concentrated rinsewaters are circulated through the membrane at pressures greater than aqueous osmotic pressure. This action results in the separation of water from the plating chemicals. The recovered chemicals can be returned to the plating bath for reuse, and the permeate, which is similar to the condensate from an evaporator, can be used as make-up water. RO units work best on dilute solutions.30... 

For fixed residue removal, the total mass of metals in the rinse water will be the same with reduced water duty, the metals concentration increases. A smaller water volume now needs to be processed (or sewered). Alternatively, if the metals concentration is sufficiently high, it can be returned to the plating bath for reuse or can be recovered. 

Reverse osmosis is a treatment system utilizing semi-permeable membranes. The system operates at pressures up to 40 atmospheres and produces a concentrate on one side of the membrane and a clear permeate on the other. It has been apphed to nickel in plating-bath waters and is most effective if the concentrate can be reused [24]. Its value for treating lead-containing wastes is uncertain. 

Membrane bioreactors are an option for municipal wastewater treatment when high effluent water quality is required, for example, bathing water quality, or when the receiving water body is very sensitive or when the water is to be treated for reuse. As mentioned before (see Section 9.2.5.1), the effluent quality is superior to that of secondary sedimentation. To attain a similar effluent quality by conventional treatment, effluent filtration and disinfection would be required in addition. This needs to be taken into account when comparing the cost of MBR and conventional activated sludge treatment. 

Water is continuously added to the last extraction bath and flows countercurrenfly to filament travel from bath to bath. Maximum solvent concentration of 15—30% is reached in the coagulation bath and maintained constant by continuously removing the solvent—water mixture for solvent recovery. Spinning solvent is generally recovered by a two-stage process in which the excess water is initially removed by distillation followed by transfer of cmde solvent to a second column where it is distilled and transferred for reuse in polymer manufacture. 

The utilization of recycle and reuse measures has also been commonly used. Many facilities have been able to minimize water use and conserve rinsewaters and plating baths by measures including the following20 21 ... 

Treatment of separately collected and reconcentrated baths that initially contain dyestuff concentrations of approximately 1 g/L and are reconcentrated to approximately 10-20 g/L dyestuff by membrane filtration. Such techniques yield considerable amounts of recyclable water, but care has to be taken to avoid any disturbing effect during reuse caused by salt and alkali content in the regenerate. The concentrated dyestuff solution can be treated with similar methods as concentrated dye solutions from fillings of padder. 

After rinse solutions become too contaminated for their original purpose, they may be useful for other rinse processes. For example effluent from a rinse tank that follows an acid cleaning bath can sometimes be reused as influent water to a rinse tank following an alkaline cleaning bath. This reactive technique was discussed in Section 1322.3. Reactive rinsing must be used with caution, however, for it can lead to precipitation problems. 

Other rinsewater reuse opportunities are also available. Acid cleaning rinsewater effluent can be used as rinsewater for workpieces that have gone through a mild acid etch process. Effluent from a critical or final rinse operation, which is usually less contaminated than other rinse waters, can be used as influent for rinse operations that do not require high rinse efficiencies. Another option is using the same rinse tank to rinse parts after both acidic and alkaline baths. 

Evaporation has been successfully used in a number of ways to recover plating bath chemicals. In one technique, water is evaporated from rinsewater to reduce its volume sufficiently to allow the concentrate to be returned directly to the process bath. In another technique, it is water from the process bath that is evaporated, making room in the bath for spent rinsewater to be added as makeup. The water vapor can be condensed in some systems and reused in the rinse system. 

Nickel Sulfamate. Vltramon, a Thomas and Betts subsidiary, installed a 1 gpm ARO system to recover rinses and recycle nickel bath used to plate electronic capacitors. Previously, Vitramon had used an ion exchange system to remove the nickel. Ion exchange regenerant was shipped to a reclaimer. Water was reused. Ion exchange cost of operation was 4,000 per month. The ARO system maintains the rinse at less than 40 ppm nickel. Savings from nickel recovery and avoided treatment cost will provide a payback of approximately 10 months. 

Rinse Efficiency Drag-oul Reduction Recycling and Resource Recovery Waste Material Reuse Rinse Water and Process Bath Recycling Treatment Alternatives Water Supply Treatment Water Segregation... 

Next the material from the filter flask is poured over the tin and the 1-1. flask stoppered with the one-hole stopper. The temperature in the water bath is maintained at 25 2° and the reduction continued for exactly 2 hours. During this time the reduction solution will go from blue to purple to reddish-brown or green. Shortly before the reduction is over, a stoppered, 500-ml. Erlenmeyer flask is packed in crushed ice in a Dewar jug. The air in the flask is displaced with hydrogen chloride gas to avoid air oxidation. When the reduction is finished, the solution is decanted into the 500-ml. flask, the remaining tin being drained. This tin can be washed and reused. The reduction solution is resaturated with hydrogen chloride gas. (This step requires... 

Substantial savings in energy, dye, chemical, and water/sewer requirements have been demonstrated, and cost/benefit analyses based on the pilot-scale data anti industrial information indicate a recovery of capital investment of less than one year for all of the systems investigated on incorporation of dyebath/axuiliary bath reuse. 

Standardization Prepare a Standard Solution containing a total of about 10% solids, using sugars of known purity (e.g., USP Fructose Reference Standard USP Dextrose Reference Standard, or NIST Standard Reference Material maltose, Aid-rich Chemical Company or equivalent) that approximates, on the dry basis, the composition of the sample to be analyzed. Dissolve each standard sugar, accurately weighed, in 20 mL of purified water contained in a 50-mL beaker. Heat on a steam bath until all sugars are dissolved, then cool, and transfer to a 100-mL volumetric flask. Dilute to volume with water and mix. Freeze the solution if it is to be reused. 

Hybridization solution 45% Formamide, 5X SSC, 5X Denhardt s solution, 20 mMsodium phosphate, pH 6.5, 300 pg/mL freshly denatured, sheared, herring sperm DNA, 200 ng of biotinylated DNA/mL. Before its addition, the biotinylated probe DNA is denatured by incubating for 10 min in a boiling water bath and quickreduce size is unnecessary, since the products generated by nick translation are sufficiently small. Filter and store the hybridization solution as was done for the prehybridization solution. Hybridization solution can be recovered after use and stored at-20°C. The solution can be reused at least 10 times over a time-span of at least 5 mo, without noticeable... 

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