Measures to prevent the generation of waste water

The following measures result in a marked reduction in waste water  

Use of dry dedusting systems Dry dedusting systems can be used for most foundry exhaust gas flows. However, in exceptional cases, it may be necessary to use a wet scmbber for removal of iron-containing ultra-fine dust fractions. The applicabilities of dry and wet exhaust cleaning techniques are discussed in Section 4.5 

Biological waste gas scrubbers or compost filters The use of a biological waste gas scrubber can be considered if the gases to be treated contain readily biodegradable substances such as phenols, etc. Biological scrubbers generate less waste water than conventional wet scrubbers because biologically treated waste water can be recirculated more often. 

Note Compost ftlters (biofilters) do not generate any waste water, although the compost material must be sufficiently moist. The technique of biofiltration is discussed in Section 4.5.8.6 

Multiple use of treated waste water Multiple use of treated waste water needs to be considered, e.g. using process water from sand preparation in the moulding sand cycle or in slag granulation. The use of cooling water in wet scrubbing may also be considered Use of waste heat for the evaporation of waste water This technique can only be applied when waste heat is available on a continuous basis. A case-by-case evaluation is needed to evaluate its applicability and economic viability 

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