Organic liquid waste treatment

The organic nature of the waste often introduces additional hazards not encountered with inorganic waste, such as susceptibility to radiolysis and biodegradation, flammability, volatility, chemical toxicity and inherent bio­hazards. This results in special requirements and considerations for storage, treatment, conditioning and disposal of this waste. The volume of organic liquid waste is usually small compared with aqueous RAW. Unlike aqueous waste, it may not be possible to discharge treated organic waste to the environment because of its organic chemical content. The goals of organic liquid waste treatment may be: (a) conversion to a solid form either directly or after chemical adjustment to a form compatible with a solidification matrix (e. g., cement); (b) volume reduction; (c) decontamination for reuse. Various techniques for the treatment of liquid organic waste have been developed and implemented in different countries [19, 20] . In some cases processes and equipment selected for the treatment of aqueous and solid waste had been adapted for processing organic liquid waste, and combined processing was cost effective. For example, small quantities of organic liquid can be readily mixed with solid waste in an incinerator. Properly controlled incineration is an attractive technique for treating organic liquids because they are readily combustible, and high volume reduction factors can be achieved. After combustion, radionuclides from the waste will be distrib­uted between the ash, filters and off-gas, to a degree which depends on details of the unit’s design and operating parameters. Further immobiliza­tion, such as grouting of ashes, will be required to stabilize these residues, some of which will have a much higher radionuclide concentrations per unit volume compared to the original waste.

Wet oxidation is a technique for breaking down organic materials to carbon dioxide and water in a process that requires significantly lower temperatures compared to incineration. The main advantages of the process are the low temperatures required and use of aqueous media, which is easy to treat.

Simple distillation may be used for the treatment of scintillation fluids and miscellaneous solvent waste. Substantial volume reduction is possible and the recovered organic solvent could be used as a technical grade solvent or as a fuel for an incinerator. Distillation can be practised with conven­tional readily available equipment and space requirements for the equip­ment are small.

There are difficulties with solidification of organic waste by cementation. Only about 12 vol.% of oil can be incorporated directly in cement and still retain a waste form that is dry and monolithic. However, significant increases in waste loadings can be obtained when emulsification is applied. A simple way of on-site treatment of organic liquid RAW is converting the liquid to a solid form with absorbents. As long as there is an excess of absorbent, there is no need even for mixing; the liquid waste can be added to the absorbent in a suitable container and eventually all the liquid will be taken up. This technique has been routinely used for the solidification of radioac­tive turbine and pump oil. The use of absorbents converts the liquid waste into a form, which can vary from loose dry particles to a jelly-like solid. The waste forms have no special integrity and are only restrained from disper­sing by the container. Another frequently used option is embedding of absorbed organics into a cementitious waste form.

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