(5) More Questions and Answers
Q.What kind of contaminated sites have proven to be effectively remediated?
A.Sites containing petroleum, MGP, and chlorinated solvent compounds have been tested and treated successfully.
Q.What is the radius of influence?
A.The radius of influence depends upon soil conditions; therefore it is best to do a pilot study. From our experience, the radius of influence can be 20 feet to greater than 100 feet.
Q.Under what soil conditions does gas injection and distribution work best?
A.Permeability: 10 -1 to 10 -5 cm/sec Seepage velocity: less than 10 ft (3.0 m) per day Aquifer thickness: 3 ft (1m) or greater(10 to 100 ft ideal)
Q.What is the tightest soil condition in which sparging is effective?
A.The tightest soil condition is 10 -5 cm/sec. 10 -6 cm/sec (clayey soils) is generally tight without enhancing the permeability of the formation.
Q.How can the effectiveness of gas injection be tested?
A.Initially, by the rise of water head elevation and change in dissolved oxygen concentration in the groundwater samples. Over a longer period, test by the rate of change of volatiles in groundwater samples.
Q.Do the microporous injection points plug over time?
A.No, properly installed and used points do not plug over time. However, if adequate pressure is not maintained by use of a check valve, water reflux occurs and there is a possibility of plugging. For protection against that possibility, a check valve is part of the Wellhead Assembly: it maintains pressure and prevents reflux.
Q.Can the aquifer be plugged by ozone injection?
A.Generally no, not from precipitation of solids. Micro-bubble injection creates a very oxidative condition in the aquifer. Injection of gas into the interstitial spaces within the formation will change the fluid flow dynamics. But this can be used to facilitate remediation, this is a consideration in the design of BLUEs system applications. Certain lithologies with high dissolved inorganic content should be evaluated for “formation fouling” but we have not experienced any detrimental effects over a wide variety of geologic settings.
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