Environmental Engineering Consulting

The authors make important notice of the effect of oxygen on the water chemistry of slag-fill aquifers by observing that the shallow pond-sampling site (site 3) that had high DO concentrations also had high nitrate/nitrite relative to ammonia (Roadcap, Kelly, and Bethke, 2005, Page 811). In this instance, the results of the sampling activity are intuitive since obviously available nitrogen will bond with oxygen to form either NO3/NO2, prohibiting, to least some degree, the formation of ammonia (NH3).  Once the topic ground water had been thoroughly covered, its mixing with surface waters were covered at length.

Sampling at site 7, a spring mixing with two (2) surface water inflows, and downstream demonstrated that pH decreased rather quickly as it was mixed with other surface waters and the atmosphere.  As noted previously in the article, calcite forms in the spring’s discharge ditch under conditions that would prohibit its formation in neutral pH waters.  At this site, calcite forms due to the introduction of carbon dioxide from the atmosphere and its reaction with Ca2+ in the spring (Roadcap, Kelly, and Bethke, 2005, Page 814).  The concentration of most cations increased along the ditch’s flowpath, pH decreased.  These results are also somewhat intuitive since metals have increased solubility in lower pH waters.

Since the geochemistry described in detail in the article and summarized above demonstrates that the introduction of CO2 facilitates pH lowering, CO2 sparging seems like a very good option for remediating the stream.  Air sparging and hydrochloric acid addition are two other commonly used treatments, and were included this article.  Dolomite was available locally and had the chemical potential to reduce pH as well, which is why it was considered.

The authors wisely considered each treatment’s effect on aquatic toxicity.  The untreated water had a 100% organism mortality rate; waters with pH effectively lowered by treatment with CO2 sparging and hydrochloric acid addition yielded 30% to 40% mortality rates, and air sparging yielded a 10% mortality rate (Roadcap, Kelly, and Bethke, 2005, Page 815).

CO2 sparging was most successful at achieving the expressed purposed of the remediation, pH reduction, of the four (4) attempted.  It lowered pH very quickly; however, I agree with the authors that it is not an acceptable alternative because of its relative ineffectiveness at lowering organism mortality.  Hydrochloric acid addition is eliminated from the list of possible alternatives for the same reason, while dolomite addition did not adequately reduce the pH.

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.

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.

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Among the primary issues those in the environmental engineering consulting field are tasked with addressing is water quality.  And, one of the hottest topics in the area of water quality is TMDL implementation, and permitting.  This post summarizes the origins  of TMDL and reviews the general regulatory process, and implementation.

Total Maximum Daily Loads (TMDLs) were first introduced in the Clean Water Act (CWA).  The CWA had its origins in legislation going all the way back to the 1899 Rivers and Harbors Appropriations Act.  The primary concern of that legislation was public health, but the CWA and its subsequent updates have expanded goals to areas outside human safety.  During the 1970s, emphasis was placed on establishing and enforcing effluent standards for point sources.

Ambient-based water quality standards are established by the individual states, and are subject to federal (EPA) approval.  Prior to the Federal Water Pollution Control Act Amendments of 1972, water quality standards were ambient-based.  However, 1972 Act introduced effluents standards for certain individual pollutants in order to avoid common problems associated with watersheds.  By setting water quality standards for streams or waterbodies, states found it difficult to limit discharges since they were not equipped to analyze the wide array of pollutants contributed by multiple discharges.

By setting effluent standards all dischargers had to follow, enforcement became less complicated.  The National Pollutant Discharge Elimination System (NPDES) addresses the point source water pollution directly by setting national effluent standards – or “end of pipe” standards.  The NPDES system is now considered successful in improving quality in waters of the nation; however, the end of pipe standards did not address necessarily address non-point source pollution.

Section 303d of the CWA mandates that all states set TMDLs for their streams and waterbodies; which is an ambient-based system, in that states do the determinations for their own waterbodies.  States must determine all sources of pollution, both point and non-point, and establish TMDLs for each waterbody, and then allocate responsibility for achieving those TMDLs to each of the waterbody’s dischargers.  The TMDL procedure is as follows:

• States must identify all waters of the state
• Determine correct designated uses
• List impaired waterbodies, by determining if standards are met for its designated use (impaired waterbodies must be submitted to EPA every two years, as part of the 1992 CWA update)
• Planning – TMDL calculation, allocation of loads among dischargers
• Implementation – enforcement of allocations as “point” sources (e.g., use of Best Management Practices [BMPs] to handle non-point sources)
• Monitoring to determine the effectiveness of the implementation process; a waterbody may be delisted if implementation is demonstrated, by monitoring, to be successful

The primary take-away from the TMDL process: regulating non-point sources is very difficult, therfore, the EPA and state regulatory agencies use TMDL allocation to treat non point source pollution as point source for individual dischargers to a waterbody.

This post summarizes the Introduction of the National Research Council’s “Assessing the TMDL Approach to Water Quality Management.”

I am a graduate of the University of South Carolina’s College of Engineering and Information Technology with a Bachelor of Science in Civil Engineering with a special interest in environmental engineering.

I am a civil environmental engineer working in the environmental engineering consulting field.  My primary areas of expertise are air quality permitting, solid management including RCRA regulation, and water resources topics including TMDL Implementation.  I hope to use this site as a means of sharing information and learning from others with similar interests.