Reusing industrial waste water

Recycling purified waste water can improve the economics of the plant s balance sheet or it may be needed because water resources are insufficient. 

The most well-known example is refinery waste water. 

These effluents are reused after purification when there is side-stream filtration on the system with an incorporated coagulant to retain colloidal matter and prevent exchanger fouling (see Chapter 3 Section 4= Recycling and Chapter 6 Treatment Systems). 

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Phosphate is sometimes present in MU water sources (say, 1-2 ppm or more) usually as a result of field and factory run-off or from the deliberate addition as a city water threshold agent to prevent corrosion and deposition in the mains. The steady growth in the reuse of secondary water sources such as municipal and industrial waste waters means that phosphate is increasingly likely to be present in MU. If the phosphate remains undetected, it likely will scale and foul FW lines by forming amorphous calcium orthophosphate [tricalcium phosphate Caj(P04)2] sludge before it reaches the boiler section. 

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

It may not be the most economical option to clean up water to a standard at which reuse or even discharge to a water course is permissible. In, or close to, large centres of population very large quantities of non-industrial waste water are treated extremely economically. Here the dilution of industrial effluent for biodegradation may be the most economic route to take. As Table 3.2 demonstrates, the use of sewers to transport solvent-laden water may present problems and the use of municipal sewage treatment works will inevitably attract a charge. It will, however, avoid the use of valuable space on a factory site and is the ultimate in end-of-pipe treatment. 

To recondition the pots, the potliner is dug out and discarded Prior to discovery of the Spokane aquifer contamination, the procedure had been to remove the pot to an outdoor concrete slab where the pot was filled with water and allowed to soak for a few days to fracture and soften the cathode The contaminated water was presumably reused for soaking and not discharged to the industrial waste treatment system because of the cyanide content The pots were Jack-hammered and the potliner dumped on the slab The potliner was transfered by a front-end loader to an unprotected pile next to the slab ... 

A large source of water for reuse may be obtained by reclaiming polluted water. Sources of polluted water emanate from domestic wastewater, industrial waste solutions, agricultural effluent as runoff water, recirculated greenhouse water, and fish pond waste. All these must be treated to a tolerable quality to prevent deterioration of the soil and aquifers, and pollution of lakes, rivers, and the sea. Above all, this is a source of usable water. 

One answer to these problems lies in the ability of industrialized society to develop beneficial uses for these wastes as by-products. The reuse of waste by-products in lieu of virgin materials can relieve some of the burdens associated with disposal and may provide inexpensive and environmentally sustainable products. Current research has identified several promising uses for these materials. However, research projects concerning Environmental Impact Assessment (EIA) of various organic and inorganic contaminates in recycled complex mixtures and their leachates on surface and ground waters are still needed to insure that adverse environmental impacts do not result. 

Some areas of application are the nuclear industry and the treatment of radioactive liquid wastes, with two main purposes reduction in the waste volume for further disposal, and reuse of decontaminated water. Pressure-driven membrane processes (microfiltration, ultrafiltration, nanofiltration, and reverse osmosis [RO]) are widely used for the treatment of radioactive waste. 

Brady FJ. Industrial wastewater UF and RO treatment for water reclamation and reuse. A survey of commercial membrane system installations. 9th Annual Industrial Wastes Technical and Regulatory Conference, San Antonio, TX, April 13-16, 2003, 443-451. Lien L and Simonis D. Case histories of two large nanoflltration systems reclaiming effluent from pulp and paper mills for reuse. International Environmental Conference, Atlanta, GA, May 7-10, 1995, 1023-1027. 

Bes-Pia, A. et al., Comparsion between nanofiltration and ozonation of biologically treated textile waste water for it reuse in the industry, Desalination, 157, 81, 2003. 

Heavy Metals Heavy metals are usually added to wastewater from municipal commercial and industrial activities and may have to be removed if the waste-water is to be reused, or discharged into a water body. 

In most plants that use reverse osmosis in the preparation of process water, the reject stream is routed directly to waste discharge without any additional posttreatment. In industrial plants that use reverse osmosis to treat industrial wastes, the reject stream may contain valuable materials and this stream would be sent back to the process. In other applications of industrial waste treatment by reverse osmosis, the reject stream may require additional treatment prior to ultimate discharge. In this case, the reverse osmosis unit will have provided a large volume of water that is disposable or can be reused (the product) and a smaller volume of reject which can be treated more economically. 

Sarkar, B., Chakrabarti, P. P, Vijaykumar, A., and Kale, V., Waste water treatment in dairy industries—Possibility of reuse. Desalination, 195, 141, 2006. 

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