From: Hunt, Tim

To: Spence, Kelley

Cc: Bradfield, John ; Dunkins, Robin ; Vipin Varma Subject: NSPS follow-up

Date: Monday, January 20, 2014 7:21:26 PM

Attachments: TRS treatment at hard-pipe mills_NCASI Summary 1-20-14.pdf



### Kelley,

As a follow-up to our November meeting, here is some additional information from hardpipe mills showing significant TRS reductions (roughly 70%) that NCASI was able to compile. I hope you find

this helpful. Please let me know if you have any questions.

Tim Hunt Senior Director, Air Quality Programs Tim_Hunt@afandpa.org (202) 463-2588 AMERICAN FOREST & PAPER ASSOCIATION 1101 K Street, N.W., Suite 700 Washington, D.C. 20005

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### Treatment of Total Reduced Sulfur (TRS) Compounds i **n Kraft Mill Condensates at Facilities**

**Employing the Clean Condensate Alternative (CCA) Op tion** 

**Background** The Maximum Achievable Control Technology (MACT) ru le for subpart S sources requires the collection and treatment of hazardous air pollutants (HAPs) in kraft pulping condensates by either (a) collecting and discharging condensates below the surface of a biological treatment system (hardpiping) or (b) routing condensates to a steam stripper, to reduce total HAP’s by at least 92 percent or more by weigh t (§63.446). In lieu of the requirement to collect a nd treat emissions from high volume low concentrati on (HVLC) sources such as the brownstock washers, faci lities are allowed to demonstrate compliance using the clean condensate alternative (CCA) (§63.447). Majority of facilities utilizing the CCA option demonstrate compliance by over-collecting and over- treating HAP in condensates. Emissions reductions under CCA are achieved by (a) diverting additional condensates away from open sewers and primary clarifier(s) and (b) reducing the HAP content in co ndensates used in brownstock washer showers and other affected process sources.

In the context of the ongoing review of new source performance standards (NSPS) for kraft pulp mill sources, EPA requested a qualitative assessment on the extent of control of total reduced sulfur (TRS) compounds achieved at facilities that utilize the C CA option. The following apply:

1. The over-collection of condensates under CCA, for t reatment in steam strippers or in biological treatment systems, results in a corresponding reduc tion in HAP and TRS content in process

water and brownstock washer shower water. The use of cleaner condensates, as process and shower water, can lead to lower TRS emissions from brownstock washers, i.e., a certain level of control is achieved due to changes in condensate re use practices. However, the impact of condensate quality on TRS emissions has not been th e subject of technical studies since the MACT rule focused only on HAP emissions

**.**

2. Facilities that treat over-collected condensates in steam strippers achieve TRS control when the stripper-off-gases (SOG) are incinerated. TRS cont rol in this case is expected to be similar to that achieved from the incineration of LVHC and HVLC gas es. (Stripper-off-gases (SOG) are burned along with low volume high concentration (LVHC) gas es in boilers, lime kilns, or incinerators).

3. Facilities that over-collect condensates in the har dpipe for subsequent treatment in biological treatment systems also achieve TRS control. Howeve r, an assessment of the level of TRS control achieved at hardpiping mills using CCA requires kno wledge of (a) TRS content in pulp mill condensates and (b) TRS control across aerated biol ogical treatment systems. Unfortunately, given that the subpart S MACT rule focused primaril y on HAPs, there is a lack of comprehensive information on TRS contents in pulp mill condensate s and on its removal across biological

treatment systems.**ncasi – summary of available information – Jan 2014**

**Concurrent TRS Control Achieved as a Result of CCA Approaches**  **TRS content in hardpiped condensates** As part of a study to investigate odor around waste water treatment plants (WWTPs), NCASI evaluated existing analytical methods and developed new metho ds to identify and quantify wastewater constituents that may contribute to odors in and ar ound treatment systems. As part of this effort, NCASI Method RSC-02.02 - “Reduced Sulfur Compounds by Direct Injection GC/PFPD,” was employed for the determination of total (inorganic) sulfide, met hyl mercaptan (MeSH), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS) in pulp and paper mill wastewaters (NCASI Technical Bulletin No. 933). The appendix to TB No. 933 includes analytical results for wastewater streams from a number of facilities, including TRS concentrations in hardpiped condensates at four pul p mills. Additionally, NCASI also carried out a deta iled study to quantify TRS emissions from WWTPs situated at kraft mills in 2005/06. As part of thi s study, concurrent liquid sampling was carried out to quantify the levels of organic reduced sulfur compo unds (RSC) using NCASI Method RSC-02.02 (NCASI Technical Bulletin No. 956). Two hard-pipe mills w ere included in this study.

The combined dataset consists of eleven grab sample s at six pulp mills. TRS concentrations in hardpip ed condensates at these mills ranged from 27 to 230 mg /L as sulfur, with a mean of 134 mg/L as sulfur. When converted to a TRS loading rate and indexed to mill production, this corresponds to a **TRS load in hardpiped condensates ranging from 0.42 to 6.23 lb/**  **ton as sulfur, with an average of 2.53 lb/ton as sulfur** 

.

**TRS Control across WWTPs**

TRS emissions from two Aerated Stabilization Basins (ASBs) receiving hardpiped condensates were also measured as part of the above-mentioned study. Whe n combined with inlet loading and effluent discharge rates, an apparent destruction percent ca n be calculated through a mass-balance. At Mill A (from NCASI Technical Bulletin No. 956), the averag e emission rate was 4.88 g/s as sulfur with an apparent percent destruction of 63%. At Mill B, th e average emission rate was 1.46 g/s as sulfur; wit h a calculated percent destruction was 76%. **The mean percent destruction of TRS compounds in AS Bs**  **receiving hardpiped condensates was 69%. When comb ined with the mean TRS loading factor above,**  **the average treatment of TRS compounds at hard-pipe mills is 1.75 lb/ton as sulfur.** 

**By comparison, TRS (as sulfur) emissions from BSWs average 0.055 lb/ton**  (NCASI 2013). In other words, this represents the average level of TRS control th at could be achieved by installing hoods on NSPS BS Ws at CCA mills. By comparison, data on TRS content i n condensates (and its destruction across biologica l treatment systems) indicate that significantly high er levels of TRS control is achieved in hardpiping mills through MACT compliance. Even when assuming only a 10% level of condensate over-collection in the hardpipe (at CCA mills), this corresponds to 0.18 l b/ton (as sulfur) of TRS control (1.75 lb/ton x 0.1 ), much higher than the level of treatment achieved th rough BSW collection.**ncasi – summary of available information – Jan 2014**

**Summary**

The over-collection of condensates under CCA achiev es TRS control due to (a) removal during biological treatment and (b) additional reduction in TRS emiss ions from brownstock washers due to the use of cleaner condensates. Facilities treating over-coll ected condensates in steam strippers achieve levels of TRS control from the incineration of SOGs (stripper -off-gases (SOG) are burned along with LVHCs and HVLCs in boilers, lime kilns, or incinerators). Ad ditionally, **limited characterization studies indicate that ~70% of the TRS (as sulfur) in condensates is treat**  **ed when the condensates are collected in a hard pip e**  **and subsequently routed to biological treatment.** On a lb/ton basis, the level of TRS control achie ved from treating condensates in biological treatment s ystems far exceeds the treatment that could be achieved by enclosing BSW systems.

**Challenges with quantifying TRS content in process condensates**  Site-specific measurements of TRS loadings and demo nstrations of treatment at hard-pipe mills are challenging, if not infeasible, at this juncture. The associated sampling and analytical techniques a re complex and difficult to implement. First and fore most, direct measurements of TRS emissions from large wastewater treatment sources require research -level resources and methods (such as the spatial ambient air sampling technique outlined in NCASI Te chnical Bulletin No. 957). In principle, an approa ch similar to the one used in Appendix C Form V could be used to estimate TRS emissions from wastewater sources (method used for hardpipe quarterly complia nce demonstrations). However, this method requires accurate speciated TRS concentration data from the various mixing zones of the ASB. The only suitable measurement method, NCASI Method RSC -02.0 2 has sample hold-time and analyte stability

issues that make it more suitable for research-leve l projects and analyses. The method is not widely offered by contract laboratories and is prohibitive ly expensive when available.

**References**

National Council for Air and Stream Improvement, In c. (NCASI). 2013. **Compilation of air toxics emissions data for sources at pulp and paper mills including**  **boilers.** NCASI AIR TOXICS EMISSIONS DATABASE.

National Council for Air and Stream Improvement, In c. (NCASI). 2008. **Emissions of reduced sulfur compounds and methane from kraft mill wastewater tr**  **eatment plants** . Technical Bulletin No. 956, Research Triangle Park, NC: National Council for Ai r and Stream Improvement, Inc.

National Council for Air and Stream Improvement, In c. (NCASI). 2008. **Spatial ambient air sampling and analysis methods for quantifying reduced sulfur com**  **pound and methane emissions from kraft mill wastewater treatment plants**  . Technical Bulletin No. 957, Research Triangle Par k, NC: National Council for Air and Stream Improvement, Inc.

National Council for Air and Stream Improvement, In c. (NCASI). 2007. **Development and application of a method for measuring reduced sulfur compounds in pu**  **lp and paper mill wastewaters** . Technical Bulletin No. 933, Research Triangle Park, NC: National Counc il for Air and Stream Improvement, Inc.