### MEMORANDUM

TO: Ron Jordan, EPA Jezebele Alicea, EPA

FROM: Liz Sabol, ERG TJ Finseth, ERG

DATE: 23 April 2012

SUBJECT: Summary of Performance Data Requested from Vendors for Chemical Precipitation Systems with Organosulfide Addition and Biological Treatment

1. I NTRODUCTION /B ACKGROUND

ERG contacted General Electric (GE) and Nalco to request pilot-, bench-, and/or full-scale performance data for chemical precipitation sy stems operating with organosulfide addition and biological treatment (GE only). ER G specifically requested performa nce data for dissolved mercury to determine the affect of organosulfide addition in chemical precipitation systems for the treatment of high dissolved mercury concentrations in FG D wastewater. In addition to dissolved mercury, ERG also requested performance data for total me rcury, selenate, and other metals, as available.

This memorandum summarizes the performance data and information received from GE based on studies of biological treatment and GE and Na lco based on studies of chemical precipitation systems with organosulfide addition.

2. GE B IOLOGICAL T REATMENT

– S ELENATE AND O THER M ISCELLANEOUS M ETALS

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3. GE C HEMICAL P RECIPITATION WITH O RGANOSULFIDE A DDITION

– D ISSOLVED AND
T OTAL M ERCURY

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4. N ALCO C HEMICAL P RECIPITATION WITH O RGANOSULFIDE A DDITION

– T OTAL AND
D ISSOLVED M ERCURY

Nalco provided raw data from a full scale ev aluation of Nalmet 1689 at a power plant FGD wastewater treatment facility. At this particular site, the FGD wastewater from 2 units/FGD scrubbers is processed through a single FGD wastewater treatmen t process. Unit 1 scrubber purge dissolved mercury concentrations ranged fr om 1,500 to 12,000 ppt. Unit 2 scrubber purge dissolved mercury concentrations range from 1,400 ppt to 20,000 ppt. Total mercury effluent concentrations range from 92 to 421 ppt. See Appendix C (monitoring data) for the specific

concentration data.Memorandum 23 April 2012 Page 2

Attachment CH-904, “Nalco Helps Wisconsin Po wer Plant Reduce Mercury Emissions” (included in Appendix C), is a summary of the FGD wastewat er at the Wisconsin power plant where the raw

data described above was collected. The FGD wa stewater influent merc ury concentration is approximately 10,000 ppt. Through chemical treatmen t using a sulfide-based coagulant (i.e., TMT15), the plant was able to achie ve 75% removal of the mercury, which was not enough to meet discharge requirements (1,500 ppt). As a result, the organosulfide based coagulant/flocculant Nalmet was used to lower mercury discharges. Because Nalmet is a polymer, coagulation and flocculation occur simultaneously. The addition of Nalmet creates la rge floc particles which settle quickly and therefore, do not read ily carry over into the effluent. Coupled with filtration, mercury concentrations could be reduced to the parts per trillion (430 ppt as shown in CH-904) level without further coagulation.

Attachment R-917, “Chemical Treatment Technol ogy for Effective Heavy Metals Removal from FGD Scrubber Wastewater” (inclu ded in Appendix C), provides data on three case studies. Case Studies 1 and 3 provide inform ation on mercury removal and Case Study 2 focuses on selenium removals. In Case Study 1, low-level mercury testi ng shows 48% better removal of soluble mercury with the organosulfide treatment over ferric chlori de alone. In Case Study 3, the addition of 30 ppm of NALMET gave 90% reduction of soluble merc ury. In Case Study 2, the goal of the treatment plan was to determine a chemical addition that w ould remove all of the insoluble selenium as well

as some of the soluble selenium in the selen ite or selenide form. According to the study, the best results were obtained using Na lmet 1689 in conjunction with Nalco 8130 and Nalco 71307. This combination (without filtration) provided over 80 % removal of total se lenium (100 % of the insoluble and 8 % of the soluble selenium). With filtration and Nalmet, Nalco 8130, Nalco 71307 treatment combination, over 90 % removal of tota l selenium (100 % of th e insoluble and 53 % of the soluble selenium) was achieved.

Attachment CH-1080, “Improved Mercury Remova l from FGD Wastewater with Nalco NALMET Technology” (included in Appendix C), is anot her case study of a plan t installing a new FGD wastewater treatment plant to remove solids a nd metals from the FGD blowdown as part of a retrofit FGD scrubber project. This FGD wastewater treatment plan t utilizes a high rate solids contact clarifier/thickener which combines coagul ation, flocculation and se ttling in two conjoined vessels. To achieve lower mercury levels in th e effluent than origin al system operations, organosulfide was added to the treatment process. Results of this jar testing showed that the optimum treatment for mercury removal was a co mbination of Nalco 8130, a proprietary coagulant blend, and Nalmet 1689 technolog y, achieving an average mercury concentration of 31 ppt.

Nalco stated that in wastewater treatment, 90+ percent removal of dissolved mercury can be

achieved if influent concentra tions reaching 40,000 to 50,000 ppt. Th at means that 400-500 ppt in the effluent can be achieved with proper treatment and clarification withou t a final filtration step.

Nalco noted that with a final filt ration step, effluent concentrati ons below 100 ppt can be achieved. Additionally, if a system designed for 100-200 ppt dissolved mercury suddenly received a concentration of 40,000 ppt, the re sponse of the system would depend on the dosage of chemistry used for mercury precipitation.Memorandum 23 April 2012 Page 3

5. C HEMICAL P RECIPITATION WITH O RGANOSULFIDE S UMMARY

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