Environmental Engineering Consulting

This write-up summarizes the journal article Geochemistry of Extremely Alkaline (pH>12) Ground Water in Slag-Fill Aquifers (2005) written by George S. Roadcap, Walton R. Kelly, and Craig M. Bethke.  The case study provides covers treatment techniques for an impaired aquifer, ultimately recommending air sparging as the best remediation alternative, of the four considered, for the remediation of high pH ground water under the conditions specified in the article.

Four (4) remediation schemes aimed at reducing the high pH waters were examined in this article, which are as follows.
•    Carbon Dioxide (CO2) sparging
•    Air sparging
•    Hydrochloric acid (HCl) addition
•    Dolomite (CaMg(CO3)2) addition

The article thoroughly summarizes the subsurface conditions in the Lake Calumet region near Chicago, IL, an area with several active and former steel mills.  The article serves as a valuable resource for people involved in remediating high pH ground and surface waters, as it is one of only a few articles covering this topic.  Although slag, a by-product of steel manufacturing processes, caused the poor water conditions in this location, the geochemistry and remediation aspects of this article are universally applicable to sites with high pH, and high concentrations of TDS, Iron and Ammonia.

A wide variety of industrial processes, in addition to steel manufacturing, may contribute to extremely alkaline waters.  As such, there may be many more sites that require remediation of the types included in this discussion.  Data collected from four (4) sites near Lake Calumet were analyzed in the authors’ discussion.  The sampling locations include two (2) springs (sites 2 and 7), one (1) shallow pond (site 3), and one (1) test pit (site 4), created for the purpose of collecting data steel slag samples (Roadcap, Kelly, and Bethke, 2005, Page 807).

The authors explained the methods used to collect and analyze the samples collected from the 4 locations listed above.  Conductivity, pH, temperature, and DO were measured in the field after proper calibration (Roadcap, Kelly, and Bethke, 2005, Page 808).  Sampled collected in the field were analyzed by an IL laboratory, and included several major and minor elements (Roadcap, Kelly, and Bethke, 2005, Table 1, Page 809).  X-Ray diffraction (XRD) was used to classify the mineral stratification in site 4.  Additionally, geochemical modeling was used to obtain other pertinent information such as dissolved gases fugacity (Roadcap, Kelly, and Bethke, 2005, Page 808).

REFERENCES

Roadcap, George S., Kelley, Walton R., and Benthke, Craig M. 2005. Geochemistry of Extremely Alkaline (pH > 12) Ground Water in Slag-Fill Aquifers. GROUNDWATER, 43(6), 806-816.