At a kraft pulp mill, methanol is one HAP among many. Under the Pulp and Paper MACT (40 CFR Part 63, Subpart S), it is the yardstick for showing that pulping condensates are collected and treated, and for proving that a biological treatment system is destroying what it receives. A sampling or lab error means more than just a bad data point as it can turn a compliant quarter into a reported deviation.
NCASI Method DI/MEOH-94.03, a direct injection GC/FID method for methanol in process liquids and wastewaters, is one of the methods Subpart S allows for those measurements. Whichever method a mill uses, usable results start in the field.
Where Methanol Data Drive Compliance
Section 63.446 requires kraft mills to collect pulping process condensates from the digester system, turpentine recovery, evaporator feed stages and vacuum system, and the HVLC and LVHC collection systems, and then treat them. Treatment options include recycling the condensates to a controlled process, reducing total HAP by at least 92%, meeting a mass removal limit (3.3 kg/Mg ODP for non-bleaching mills, 5.1 kg/Mg for bleaching mills), or meeting an outlet concentration limit (210 ppmw or 330 ppmw, respectively). Many mills hard pipe condensates below the liquid surface of an open biological treatment system and demonstrate compliance there.
Under 63.457(g), total HAP for the condensate requirements is measured as methanol. For biological treatment, the first quarterly test each year measures acetaldehyde, methanol, methyl ethyl ketone, and propionaldehyde. The remaining quarterly tests under 63.453(j)(3) may use a methanol-only procedure, carrying forward the ratio (“r”) of the other three compounds to methanol from the first-quarter test. Each of those tests is due within 45 days after the start of the quarter.
The biological treatment calculations in 63.457(l) take inlet methanol mass flow and a site-specific biodegradation fraction, fbio(MeOH), to compute percent reduction or mass removal. When a daily monitoring parameter such as outlet soluble BOD5 falls outside its established range, archived inlet and outlet grab samples may need to be analyzed to show that the excursion did not mean a loss of compliance. In each case, the answer depends on methanol concentrations measured in the liquid.
Method 305 Versus NCASI DI/MEOH-94.03
Section 63.457(c)(3) allows three approaches for measuring methanol in liquid streams: EPA Method 305, NCASI Method DI/MEOH-94.03, or another method demonstrated to the Administrator’s satisfaction. The first two are built on different ideas, and the choice affects both the field program and the result.
Method 305 does not measure total concentration. It measures emission potential, meaning the portion of each compound that can be stripped from the waste under a defined heated purge. In the lab, about 10 grams of sample is suspended in polyethylene glycol and water and purged with nitrogen at 75°C for 30 minutes. The purged compounds are captured on sorbent and analyzed by GC. Because a water-soluble compound like methanol does not purge completely, Subpart S requires the result to be divided by a compound-specific fraction measured (fm). For methanol, fm is 0.85. The method itself also notes that water-soluble compounds are hard to recover without analyzing the water in the knockout trap.
DI/MEOH-94.03 takes a more direct route. The liquid sample is spiked with an internal standard and injected straight into a GC/FID, with no purge step. NCASI validated it under EPA Method 301 for kraft and sulfite mill liquids, including foul and stripped condensates, evaporator condensates, and treated and untreated effluent. The minimum measurement level is 0.5 mg/L, and concentrated condensates are diluted into the calibration range.
The two methods also differ in the field. Method 305 samples are collected following Method 25D procedures, typically weighed into vials that already contain polyethylene glycol. DI/MEOH-94.03 samples go into 40 mL VOA vials filled with zero headspace. A sampling team needs to know which method the lab is running before mobilizing, and a mill switching methods partway through a compliance history should expect some discontinuity in its data.
Sampling Is Where Methanol Data Are Won or Lost
Methanol is volatile, and condensate streams are often hot. Regardless of the analytical method, most of the risk to a methanol result sits in sample collection:
- Sample location. Subpart S calls for sampling from an enclosed pipe before the liquid is exposed to the atmosphere wherever feasible. Sampling from an open sewer, sump, or tank hatch can understate inlet loading to a biological treatment system.
- DI/MEOH-94.03 calls for cooling streams above 160°F through a cooling coil before collection. Without it, methanol flashes off as the sample is drawn.
- Containers and headspace. Each method has its own container and fill requirements, and headspace in a methanol sample is lost data.
- Preservation and storage. Under DI/MEOH-94.03, effluent samples are acidified to pH 2 to 3 without going below pH 2, and all samples are refrigerated at 4°C. Archived daily grab samples for biological treatment must also be held at 4°C.
- Run structure. Each test needs at least three runs of at least one hour, with grab or composite samples taken at roughly equal intervals and inlet and outlet flow measured at the same time.
Coordination with operations matters as well. Quarterly tests have to reflect representative operation, inlet and outlet samples have to be paired in time, and the 45-day window at the start of each quarter leaves little room to repeat a test that went wrong in the field.
How Trinity Supports Methanol Sampling Programs
Trinity’s Chemical Sector Services group plans and performs wastewater and condensate sampling for Subpart S and other wastewater rules. Our article on Ethylene MACT and BWON wastewater compliance covers how the same sampling discipline applies at chemical plants. For Subpart S methanol programs, our support includes:
- Sampling plans. Developing site-specific plans that identify sample points, sampling sequence, run timing, and flow measurement for condensate and biological treatment tests.
- Field sampling. Collecting samples according to Subpart S and the selected method, including cooling hot streams, meeting container and headspace requirements, preserving and storing samples, and maintaining chain of custody.
- Method selection. Helping mills evaluate Method 305 and DI/MEOH-94.03 for their streams and setting up field procedures to match.
- Compliance calculations. Applying results to condensate mass removal and percent reduction, fbio(MeOH) and “r” value determinations, quarterly biological treatment tests, and excursion evaluations.
Mills planning their next quarterly test, revisiting sample locations, or seeing methanol results that do not line up with process expectations may benefit from a review of their field procedures. For assistance, please contact Amanda Antico or Deanna Duram.
