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FA <br /> Im , <br /> 2.3 (:it.OUNUVVA'1'LIZ Ai`;I) SOIi. VAI'Olt'I'Itl?A'I'1VIrN'I"I'ECIINIQUES <br /> Below is a list of coaitntonly catlploycd treatment technologies: <br /> 1, 6ir stri yin= is a prm,x." that transfers hydrocarbons dissolved in the groundwater <br /> into the air that is passed through the water. There are four basic types of air strip- <br /> pers: coantereurrent packed CUlllnins,diffused aeration systems,cross flow towers, <br /> and coke tray aerators. Of titcse the countercurrent packed column is the most <br /> coninion type of strippcu. Air stripling is an efficient.cost-effective method of <br /> removing hydrocarbons from groum*-,ater. Treatment of[lits effluent vapors is then <br /> required by either carbon adsorption or oxidation techniques(see below). <br /> 2. Thermal and cntttEytic.oxicl:nior are two processes that are used to convert liyd,o <br /> carbons, ;itlicr collected from ;;oil by vapor extraction or froth water by air strip- <br /> ping, to carbon dioxide and waiter. '1'hermnl oxidation is used to treat vapors that <br /> contain high cor.centraitions of hydrocarbons,and catalytic oxidation is used to treat <br /> vapors that contain low concentrations of hydrocarbons. Batch of these treatment <br /> methods is readily available and relatively easy to inFtall. The advantage of using; <br /> either one of these treatment method: is that file contt,ntinant is destroyed on the site <br /> and not transported off the site. <br /> 3. C'irbor, adsorptiop is a physical process in which hydrocarbons are transferred from <br /> to the surface of the solid carbon,where it accumulates <br /> an aqucons or vapor phase <br /> for subsequent extraction or destruction. The phase transfer occurs primarily as at <br /> result of the low affinity of the hydrocarbons for water or vapor phase and their high <br /> affinity for the surface of the carbon. Further treatment or proper disposal of the <br /> spent car.bon is required ai a considerable cost. For this reason,carbon is preferable <br /> where hydrocarbon concentrations are tow and is most effective as a secondary or <br /> polishing irenuneiu itlelliod. <br /> 4, ]tcvcrse osmosis rentovcs hydrocarbons Goin the groundwater by forri;ig it under <br /> sufficient pressure througi: a semi-permeable membr:ane. "rhe membrane allows <br /> water to pass through alt at much greater rate than other compounds dissolved in it. <br /> Reverse osmosis is not effective ,or the removal of organic c:atnpotiIds-SU Al as <br /> hydrocarbons. <br /> 5. V-ieroxidation is a process ill which ultraviolet ry li:lua+s and hydrogen peroxide <br /> are used to create hydroxide radivals that attack and oxidize organic compounds <br /> such as hydrocarbons in the froundwater. The hydrocarbons are transformed into <br /> E inert and harmless clicniicAl,such as carbon dioxide and nitrogen. The cost of this <br /> type of treatment system is about four times that of air stripping and thermal or <br /> catalytic oxidation. <br /> s-.r <br /> M'Y1'NiM 6 <br />