Water minimization reuse

So far the discussion on water minimization has restricted consideration to identify opportunities for water reuse. Maximizing water reuse minimizes both fresh water consumption and wastewater generation. However, the process constraints for inlet concentrations, outlet concentrations and flowrates have so far been fixed. Often there is freedom to change the conditions within the operation. Typical process changes that might be contemplated include ... 

The company has now been told that it must reduce the total water demand by at least 10 per cent. Carry out a water minimization study to determine the scope for reusing water. Discussions with the operations managers have concluded that not all the operations need to be fed with freshwater. The maximum concentrations that can be tolerated at the inlet of the operations are given in Table 26.20. 

Mann JG and Liu YA, (1999), Industrial Water Reuse and Waste water Minimization, McGraw-Hill. 

Mattioli D., Malpei F., Bortone G. and Rozzi A. (2002), Water minimization and reuse in the textile industry - Water and resource recovery in industry , Euro Summer School. Wageningen, 24-42. 

In a typical procedure, a solution of 0.175 mmol of L- -amino acid and 0.175 mmol of NaOH in 1 ml of water was added to a solution of 0.100 mmol of Cu(N03)2in 100 ml of water in a 100 ml flask. Tire pH was adjusted to 6.0-6.5. The catalyst solution was cooled to 0 C and a solution of 1.0 mmol of 3.8c in a minimal amount of ethanol was added, together with 2.4 mmol of 3.9. The flask was sealed carefully. After 48 hours of stirring at 0 C the reaction mixture was extracted with ether, affording 3.10c in quantitative yield After evaporation of the ether from the water layer (rotary evaporator) the catalyst solution can be reused without a significant decrease in enantioselectivity. 

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 ... 

California Steel Industries, Inc., located in Fontana, CA, reclaimed wastes to increase profits and address water use issues. The facility, a steel mill, is situated in an area that does not have a ready supply of process water. Also, the offsite recycling facility used to dispose of spent process pickle liquor was soon to become unavailable. As a result of these concerns, the company constructed an onsite recycling facility designed to recover ferrous chloride for resale and to reuse water and hydrogen chloride for use in steel processing operations. Environmental benefits include the recovery and resale of 20 to 25 t/d of ferrous chloride, 13,440 L/d of hydrogen chloride, and 49,200 L/d of water. In addition, corporate liability was minimized because spent liquor was no longer sent to a disposal facility. 

Parallel cooling water use that is minimized to achieve A Tmin at the outlet of each heat exchanger leads to a flowrate for the network of 25.4 kg s-1, with a cooling water return temperature of 52°C. Maximizing the reuse reduces this flowrate to 21.5 kg s-1, and the cooling water return temperature increases to 57.8°C. 

Based on the previous studies and the above discussions, it is required to achieve environmentally sustainable development in textile industry since closing of water cycle is highly recommended [29]. It can often be done by the application of the combined membrane-biological processes, especially by the implementation of NF-biological and RO-biological processes, which enables the water reuse process, thereby the minimization of freshwater consumption. 

The process recovers hydrocarbons suitable for reuse or recycling and recovers water treatable in wastewater treatment facilities. Thermal distillation can be used for waste minimization, recycling, or as a final treatment. 

The use of solvent extraction also represents a potentially feasible process. Solvent extraction is an engineering unit operation that is adapted effectively to continuous processing. It has been used with success for the isolation of nonpolar compounds of bp >100 °C (58). Solvent extraction (continuous liquid-liquid extraction) may represent a useful process for routinely concentrating 50-100 L of water. The major problem with solvent extraction is the evaporation and recovery for reuse of large volumes of the organic solvent. Other problem areas that must be considered are purification of sufficient solvent and minimization of artifact formation by heat. 

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