Physicochemical purification

This stage is called physicochemical because it combines the use of a coagulating agent and gravity separation of flocculated SS or HC. 

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By precipitation in the form of colloidal S or FeS, they can also make physicochemical purification flocculation more problematical and more sludge-producing. 

Physicochemical purification which eliminates the residual fraction of the mechanical emulsion or all of the HC in chemical emulsion. 

Lagoons, located after preliminary oil removal and before physicochemical purification, can provide one to several days residence time. They are common in the United States and sometimes even replace physicochemical purification. They are used for facultative aeration and for equalizing concentrations... 

This step cakes place before recycling to the desalter or before discharge into the general effluent, upstream from physicochemical purification. In the first case, it consists of a stripping operation. In the second, it may be limited solely to oxidation of the water, making sure there is no transfer of pollution to the air. Accordingly, only the effluents from the FCC and hydrocracker, if not from hydrodesulfurization, must be stripped. On the other hand, in a mixture with the other topping condensates, a drop in the the level to below a concentration of 300 mgT means that an atmospheric oxidation treatment can be contemplated, provided precautions are taken. 

The first purpose is to eliminate floating HC and a fraction of the HC in mechanical emulsion. The resulting water must be sufficiently oil-free to run through downstream physicochemical purification simply and with economical amounts of reagents. 

The second purpose is to eliminate sands and alluvia which are not wanted in physicochemical purification where they would hinder proper collection, concentration and final disposal of floated oily sludge. 

Oil separation therefore usually works without reagents. It is designed to equalize residual HC levels at the physicochemical purification inlet by reducing peak HC arrivals, whereas before it often used to be the only purification step and had to be sized up considerably. Depending on how fine the existing emulsions are, the resulting levels of insoluble HC may in fact vary from 20 to 150-200 mgd (in petrochemical plants). In principle, they can not be anticipated or calculated. A certain approach can, however, be acquired in the case of simple effluents (deballasting, produced water). 

Tire water falling downstream from the weir has no adverse effect on the physicochemical purification operation. It may, however, cause foaming and aerosols, or even odors. 

Generally speaking, controlling physicochemical purification processes, especially by dissolved air flotation, prioritizes the separator s safety function at the expense of the polishing function, which in any case has often become redundant. 

Z 6 Physicochemical purification of effluents from preliminary oil separators... 

Physicochemical purification can therefore be defined as the combination of flocculation using two possible processes and separation of the resulting (or potential) floe by two physical mechanisms flotation or filtration (see Fig. 27). 

Biological purification is the second main purification stage for refinery and petrochemical plant WW. It is designed initially to eliminate the soluble BOD5 that subsists after physicochemical purification and panicularly the phenols. 

An overly large amount of hydrocarbons coming from physicochemical purification, which is particularly likely when the purification step consists of filtration without coagulation. 

With IWW coming from physicochemical purification and BOD5 of over 100 mg l justifying activated sludge purification, the mass of volatile solids can be replaced by the... 

First of all the insoluble HC must have been properly removed by physicochemical purification. Otherwise they could dirow off the settling of activated sludge or plug up a trickling filter. A concentration of over 10% of HC in activated sludge is unacceptable whatever system of purification is used. 

Resort to preventive use of aluminum sulfate in physicochemical purification to precipitate up to 3 to 5 mg l" of anionic detergents. 

Pressurized or Biofor-type bioftlters can be used in line behind a trickling filter or directly on the effluents at the physicochemical purification outlet to solve the following problems ... 

Oily sludge, chiefly made up of physicochemical purification sludge. It is thickened on drying beds to about 30% of DS and contains less than 10% HC. Production of around 1300 CO 1500 fy . The sludge is dumped. 

Physicochemical purification includes flocculation (iron chlorosulfate and cationic polyelectrolyte) followed by flotation. 

The "North" effluent comes from the "plastics and polymers" center. An elementary scream (expandable PS, 8 m h ) has already undergone physicochemical purification. 

The "North" effluent goes through an API oil separator and is sent partly to physicochemical purification (DAF). The rest is sent directly to general biological treatment except if there is an accident, it is sent to the site s physicochemical purification process. 

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