United States Environmental Protection Agency Industrial-Environmental Research Laboratory Cincinnati OH 45268 Research and Development EPA-600/S2-82-062 August 1982 Project Summary Emissions and Residue Values from Waste Disposal During Wood Preserving B. DaRos, R. Merrill, H. K. Willard, and C. D. Wolbach Agency restrictions on the discharge of wastewater generated during the preservation of wood has resulted in the increased use of evaporation techniques for water removal by the wood preserving industry. This report. which further details the type of work described in EPA report 600/2-81- 066 "Wood Preserving Industry Mul- timedia Emission Inventory." dis- cusses emissions and residues that were measured during thermal (pan) evaporation, spray pond evaporation. and direct thermal destruction of organic components in the wastewater. The information presented includes plant and evaporation device descrip- tions, wastewater and residue handling procedures, sampling and analytical results, and conclusions and recom- mendations. Also presented are quali- tative descriptions of the fugitive emissions and residues that occur during normal processing operations. It was concluded that toxic materials are both emitted and disposed as residues. This includes organic com- pounds (phenols and polynuclear aromatic hydrocarbons) that were emitted to the atmosphere during thermal (pan) evaporation. Similar organic emissions from the spray pond were below detectable levels. Contrarily, solid residues from evapo- rators had low concentrations of toxic organic constituents while residues in spray ponds contained much higher levels than the feed wastewater. Fugitive organic emissions from the retort and vacuum vents were highly concentrated although limited in duration. Thermal destruction of wastewater sludge by cofiring in an industrial wood-fired boiler was 96.1 to 99.99+ percent complete for the measured organics. Chlorinated dioxin and furan components were measured in both sludge and ash wastes, but varied too much to determine removal or generation rates. Sludges produced from each process contained a significant toxic organic fraction. Waste sludge must be recy- cled back to the process for reuse or disposed in a manner cognizant of the toxic components identified. This Project Summary was devel- oped by EPA's Industrial Environ- mental Research Laboratory, Cincin- nati, OH, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction The wood preserving industry pri- marily produces utility poles, railroad ties, and construction materials, chem- ically treated to enhance the useful life—usually with creosote, penta- chlorophenol (penta) or waterborne salts. Conditioning and preserving the wood generates a wastewater stream of wood extracts and toxic preservative components. To dispose of this waste in accordance with Environmental Protec- tion Agency (EPA) regulations, the ------- industry generally discharges effluent to POTWs or uses evaporation (thermal or pan methods, cooling towers, and solar and spray ponds) in conjunction with oil/water separation and other in- plant modifications. This report sum- marizes the results of test programs to quantify the release of organic species 1) from the pan evaporator treatment system to the air, 2) of similar emissions and residues to land from a spray pond and 3) of emissions and ash from preserving oil-laden wastewater dis- posal in an industrial steam boiler. Other residue discharges were also characterized for these systems. Conclusions The results of this program confirmed that the discharge of organic compounds during wastewater evaporation in thermal (pan) evaporates occurred and in greater amounts than usually pre- dicted. The toxic organic content of wastewater charged to the evaporators was many times higher than that of similar wastewater reported in litera- ture. Spray pond emissions were such that the cryogenic sampling systems did not yield enough sample material to detect the low volatility components of the wastewater if present. Therefore, of the evaporation systems studied, therm- al (pan) evaporation had the most emis- sions and spray ponds the least. Solid residues in spray ponds have much higher concentrations of toxic organic constituents while residues in evapor- ators contained much lower concentra- tions than the feed wastewater. The destruction of the organic com- pounds in an industrial steam boiler is a viable disposal option. The system tested accomplished a 96.1 to 99.99+ percent destruction efficiency of the phenols and PNAs measured; certain chlorinated dioxins and furans were present in the preserving waste feed and ash streams. No generation or destruction efficiency could be deter- mined for such dioxin or furan constit- uents due to limited analytical reliability. Industrywide, the air emissions from onsite treatment of wastewater handling had been estimated at <100 metric tons/year, based on the reported mass of volatile organic compounds contained in wastewater requiring treatment. However, PNAs and other aromatic compounds were emitted at rates up to 12 kg/hr for the plant tested (which uses two thermal evaporators). The wide variation in pollutant releases (<2 to 11,300 g/hr and ~0 to 52,000 ppm) within one day or less for individual sources precludes establishing exact mass emissions. Measured fugitive emissions, although of high concentra- tion, were apparently of relatively short duration. Thus, although localized emissions do occur, the wood preserving industry in total does not emit as much organic material as some other industry segments. Table 1 presents a summary of the organic materials discharged from the evaporation devices. Solid residues produced from each process must be recycled back to the process for reuse or disposed in a manner cognizant of the toxic compo- nents identified and quantified. Recommendations If evaporation technology is to be employed, it must be recognized that the thermal (pan) evaporation system is an emitter of organic components to the atmosphere and its minimal use would lessen air emittants. Regardless of the evaporator used, care should be taken' to develop oil/ water separation techniques which minimize oil and sludge carryover to the evaporator. A program should be conducted to establish the best available separation systems or to develop meth- ods to enhance the operation of existing systems. Systems with potential ap- plicability include chemical flocculation, solvent extraction, biological pretreat- ment, and land application. A pre- liminary study (EPA-600/2-81-043) has covered parts of the first three mentioned treatments. Disposal of residue from systems that minimized air emissions must be accomplished by modes (preferrably by reuse) that do not adversely impact the land. The destruction of wood preserving wastes by cofiring in boilers can be accomplished with minimal environ- mental impacts. It is recommended that industry pursue such disposal. Also a program should be conducted to deter- mine the proper injection (atomization) methods, and the residence times and temperatures necessary to satisfactorily destroy the organics in the waste at higher loadings. Such an incineration study could productively be extended to include the ash and a variety of sludges. Further analysis of the most toxic bypro- ducts (possibly furans) should be extended for better speciation and quantification of the chlorinated di- benzodioxins and chlorinated dibenzo- furans. Careful evaluation should be conducted of the partitioning of these organic components in ash, especially where no baghouse is used. Fugitive emission and residue studies should be extended to include the duration of emission or floyvrates and extent of onsite land (qr subsoil) contamination. Such information could be utilized along with the existing concentration values to quantify these pollutant sources. If further testing of very low level emissions from ponds is undertaken, it is recommended that surface emissions be sampled separately from spray drift sampling. Surface emissions can be analyzed from samples of the air layer above the surface. This air layer contains all pollutants emitted if the surface is enclosed by a film bubble that excludes all surrounding air transfer. Particle or aerosol drift can be better sampled by a high volume collection device. Wood Preserving Program Onsite Wastewater Disposal by Evaporation Excess wastewater is most easily managed onsite by water removal treatment. The practice of using evap- oration to achieve water removal is reviewed below as well as a model which predicts pollutant losses associ- ated with such practices. Results of a program funded by EPA lERL-Ci and reported as 600/2-81-066 indicated that organic components of the wood preserving wastewater could be dis- charged to the air during evaporation. In Table 1. Summary of Emissions and Residues of Organic Compounds* Emission Emissions Residues concentration rate concentration Source (ppm or fig/g) g/hr yg/g Thermal evaporator Spray pond evaporation Retort emissions/ residues Vacuum vent emissions 36 to 1.500 <1 220 to 3.700 22.000 to 52.000 1.8 to 11.300 0 to 20.000 75 48,000 2.100 to 14,000 * Organic constituents include volatile and semivolatile (PNAs) compounds only. Residues include only separately wasted material, not recycled streams. ------- a mathematical expression developed for the evaporation rate of these organic chemical pollutants, diffusivity in- creased as a function of increased temperature, which would then drive higher-molecular-weight compounds out of solution. This evaporation model applies to both solar ponds (quiescent lagoons) and thermal (pan) heated evaporators, and indicates emissions from thermal evaporators should be higher. Thermal evaporators apply heat directly to accelerate evaporation. The wastewater is contained in a tank or lined pond and heated by an external source such as boiler steam, or by using a cooling fluid to condense vapor from the retort before recycling to the evaporator Another way to enhance evaporation is to increase liquid surface area for greater liquid-air contact. One such device is a spray pond which isa lined or unlined lagoon with a pumping system and nozzles to spray the contained wastewater. Less land is required for evaporation of a given waste than is needed for solar ponds. The evaporation rate of organic compounds from sprayed wastewater was estimated using the equation for the evaporation rate of a free-falling drop. Diffusivity and partial pressure, as well as air resistance, were included in the evaporation model that applies to spray ponds and cooling towers. With cooling tower evaporation using Boulton conditioning, wastewater is condensed from the retort and sent through an oil/water separator, and is then added to the cooling water that recirculates through the condenser and cooling tower The waste heat promotes evaporation. For processes without Boulton conditioning, there is insuffi- cient waste heat to evaporate the wastewater generated. A field test at a cooling tower site had found low- molecular-weight compounds being emitted to the atmosphere while non- volatile organics remained in solution. Another evaporation process used by the industry is land irrigation. Waste- water is sprayed onto a field and part of the droplets evaporate, after which time solar evaporation occurs as the water percolates into the soil Each of the wastewater treatment processes described produces a residual sludge. The amount of solid waste material generated depends on the treatment technologies employed. This material is typically disposed of in landfills (usually onsite if land is available). Incineration of solid waste is a very limited practice at preserving plants. Characterization of Chemical Discharges from Thermal (Pan) Evaporators Field tests were conducted at a wood preserving plant (Plant A) equipped for thermal (pan) evaporation to determine the organic residues and emissions from two evaporators, one of which is for wastewater containing penta and the other for creosote wastes. The plant used two treating cylinders (one with penta, the other creosote) and Boulton conditioning. Oil/water sep- arators recovered oil for reuse, routing the remaining wastewater to its respec- tive evaporator. Steam was then pumped through coils in the tanks to boil the wastewater, driving off the water. Post evaporation oil/preservative was re- turned to the work tanks while a resi- dual sludge was subsequently landf illed in drums. Source emission sampling was con- ducted at the evaporator outlets; total hydrocarbons and specific low-molecu- lar-weight hydrocarbons were measured at each emission point. The EPA Method 5 sampling train was used with XAD-2 resms for nonvolatile organics; volatile organics were measured by field gas chromatography (GC). Grab samples also were taken of each evaporator's contents, of the treating solutions, penta in treating oil and creosote, and of both fractions from each oil/water separator. Emissions concentrations were cal- culated by dividing the amount of each component collected in the resins by the water volume in the impinger train as water vapor was the major carrier gas. Waste generation rates were based on plant information and field confirmed with measurements. Volume emission rates were computed from the rate of wastewater volume change in each evaporator. Because emission mass and concen- trations reported for the field tests were at times well above their predicted levels, a new model for predicting emissions was developed. In thermal evaporation, the concentration of the emitted specie varied in a cyclic pattern depending on when in the evaporation cycle the sample was taken. This was modeled as a series of physical mech- anisms, each dependent on the distri- bution of the particular component in the sludge, water, and oil. The results of this study confirm that all organic species analyzed in the wastewater stream are emitted to the atmosphere during pan evaporation. The emissions rate of all organics measured and of specific components is highly variable and is cyclic (highest just after charging) due to the once or twice- a-day charging of the evaporators from the oil/water separators. The rate of emitted organics during the test period varied from 11,300 to 1.8 g/hr for each evaporator (see Table 2). Mass dis- charges of organic material was not time weighted with the exception of a creosote charge. In that case, 65 percent of the daily charged organics were emitted in 3 hours. The concentra- ted residue consists of treating oil that was recycled back to the working tanks and a residual sludge (2 to 3 percent) that contained toxic compounds. Characterization of Chemical Discharges from a Spray Pond Field tests were conducted at a wood treating plant (Plant B) with a spray pond to determine the organic emissions from the pond, the resulting sludge, and the wastewater input. The program focused on determining if organic emissions were discharged during evaporation and if the transport mech- anisms could be established. Cryogenic sampling and resin trapping methods also were compared. The plant used two treating cylinders (one with penta, the other with creosote) and a closed steaming process. Individ- ual oil/water separators, operated manually, recovered the treating form- ulation for reuse from each wastewater stream. Creosote wastewater was discharged directly into the spray pond, but penta wastewater was treated further by a three-zone gravity separator and skimming device before discharge. Sprays were operated 24 hr/day. The field tests included sampling to determine characteristic of the air above the spray pond using cryogenic and resin trapping methods, and taking grab samples of pond wastewater and sludge. Toxic organic constituents contained in the wastewater discharged into the pond became concentrated in the bottom sludge layer. Concentrations of penta and PNAs evidently decreased in the pond liquid layer as they were far below the influent levels. Ultimate ------- Table2. Loading and Emitted Organic Compounds: PNAs, Penta 3 Phenol Combined Process Unit Creosote Penta Industry Average Evaporator Evaporator Wastewater** Flow (g/hr) (g/hr) (g/hr) Average hourly rate fed to evaporators 130 2,300 21 Exhaust emissions rates measures minimum maximum other sample 140 1,100* 960* 1.8 1 1.300* 8.0 * Measurements taken shortly after new charge addition. **Value based on EPA-EGD data on wastewater requiring disposal by evaporation or equivalent. sludge disposal was not monitored, but is anticipated to be affected after several years. Emission rates could not be deter- mined due to the detection limits of the sampling and analytical methodology. Although the system used is currently the best way to determine organic emissions from surface waters, the sampling system's limited volume and location (above surface) combined with low pond evaporation rates prevented the detection of low and medium volatile compounds. Characterization of Chemical Discharges from Cofiring Wastes in a Boiler Field tests were conducted at a wood preserving facility (Plant C) using a 18 kg/hr pile-burning watertube boiler to cofire wood waste and penta/creosote wastewater. To determine the destruc- tion and removal efficiencies of organic compounds in the wastewater, inputs (wood waste and sludge) and output (hopper ash, baghouse ash, bottom ash, and stack gases) were analyzed. Data for a material balance evaluation was collected. The facility used six retorts and a steaming process to treat wood with penta, creosote, or waterborne pre- servatives. Individual oil/water sepa- rators handled wastewater from each treating process, recovering the pre- servative fraction for reuse. The remain- ing wastewater and sludge was routed to a storage tank until enough had accumulated to be fired in the steam boiler. The boiler, consisting of a furnace and auxiliary cell, was fueled using two metering bins and a contin- uously operating screw conveyor. Fuel is stored in either a wet or dry wood fuel silo, or on a waste wood slab pile. The field tests included a preliminary characterization of the gas stream, isokinetic source sampling of the flue gas, determination of total hydrocarbons and specific low-molecular-weight hydrocarbons, composite sampling of the bottom ash, hopper ash and waste- water sludge, and grab samples of the baghouse ash, treating penta in oil, and bulk treating creosote. The EPA Method 5 sampling train was used with XAD-2 resins for nonvolatile organics. A field GC was used to determine volatile emissions. Air emission rates and ash estimates for naphthalene and phenol are sum- marized in Table 3. Other components were not detected in air emissions. Based on these emissions, destruction efficiencies of 96.1 to 99.99+ percent were calculated. Due to the high toxicity of some isomers, analyses for chlorodibenzo- furans (CDF) and chlorodibenzodioxins (CDD) were undertaken. No CDF or CDD were detected in the air emissions. Ash, sludge, and penta in oil samples were analyzed by three laboratories using split samples. Both CDFs and CDDs were found in the treating penta solution, waste sludge and the ash. Although these materials were detected, the quantities measured were not consistent and evidently depended on the analyzing laboratory's procedure. Extraction and cleanup procedures were quite different between the labs as were spiked sample recovery and detection limits. Unfortunately the toxicity of CDDs and CDFs are quite isomer specific while the results reported do not contain isomer data that is clearly independent of contamination and also reproducible. In terms of specific monomers, TCDDs are evidently generated in the process while OCDDs are reduced. The highly toxic isomer 2, 3, 7, 8-TCDD has not conclusively been demonstrated as present and apparently is not in ash samples. Values determined are in the range reported for combustion ash and especially of wood preserving waste ash from other sources (see Table 4). Measurements of Mono-CDD, Di- CDD, and Tri-CDD monomers are significant as this is only the second time combustion source measurements have had positive values reported. Table 4 contains typical data for the three laboratories. Evaluation of Fugitive Emission and Residue Sources Fugitive emissions measured were cylinder spillage and vapors released during unloading/charging operations, emissions from valves, fittings during transfer or preservative formulation, or open vessels, and vacuum vent exhaust during the treating cycles. These sources also are close to employee work areas. Air samples were collected directly above the access doors during unloading/charging using EPA Method 5 and XAD-2 cartridges; the fugitive emissions released appeared as a dense white plume. Emissions from preserv- ative transport on the plant site were not tested. Fugitive residues measured included treating liquid spillage and deposition. Samples of accumulated spillage were collected directly falling from the access doors of the penta and creosote treating cylinders. Emissions resulting from pressure release and vacuum exhaust during the treating process were characterized. Grab samples from a vacuum vent common to both penta and creosote treating cylinders were analyzed onsite for total hydrocarbons; Table 1 sum- marizes these and other hydrocarbon results. The grab samples also were tested for low-molecular-weight hydro- carbons—benzene, toluene, and ethyl- benzene. Significant concentrations of organic compounds were found to be emitted, and the vacuum vent was determined as the greatest fugitive air emission source with rates varying from 0 to 360 g/min of organics. The most significant solid fugitive discharges were retort drippings and spray pond residues. The final disposal of residues which accumulate in treatment lagoons, holding ponds or tanks depends on site specific management practices. When ------- Table3. Rates of Discharge and Efficiency of Destruction for Naphthalene and Phenol Test 2 Naphthalene Phenol Solid rate Test 3 Naphthalene Phenol Solid rate Test 4 Naphthalene Phenol Solid rate Feed (g/sec) 0.10 0.10 79 0.08 0.08 79 0.05 0.11 79 Bottom ash (g/sec) >5 x W5 >5 x 70-7 >5 >9 x iO's >4 x /CT6 >5 >4.8 x 70~5 >3 x 70~6 >5 Mech. hop. (g/sec) >J > >7 * >70 >7.7 >7 > >70 >2.2 >7 > >70 : 70"" : 70~6 x 70~4 '• 10'6 x 70~5 = 70~6 Baghouse (g/sec) >5> >2.5 >5 >1.9 c 70~5 x 70~9 x 70"5 >7 x 70"6 >5 >2.5 >7.5 >5 x W'5 x 7CT6 Gas (g/sec) 3.9 x 70~3 2.9 x ;o~5 re.ssr 7 x /o'3 >7.9 x 70"5 (6,85)* 1.10* W'3 1 6 x 70"5 P. or Total out (g/sec) 3.9x 70~3 2.9 x /O"5 7 x ;o~3 >2 x 70"5 7. 7 x 70~3 7.6x 70'5 Efficiency (percent) 96.1 99.97 98.7 >99.99 97.8 99.99 Assumptions: Feedrate, all cases=79 g/sec sludge; ash quantity is 5 g/sec total, but some unburned organics were observed in the mechanical hopper thus >10g is used. *Sm3/sec (23°C and 1 atm). Table 4. CDD Values in Penta and Ash Reported from Combustion Sources Reporting source This project (Plant A) Ash Lab A (d-2) Lab A (d-3) Lab A (d-4) Lab C (d-2) Bottom ash Baghouse (fly) Treating Solution Lab A LabB Multiple sources wood preserving waste ash Lab combustion of penta (smoke) Lab combustion of penta, 2, 4, 6 tri-. and 2, 3. 4, 6-tetra- chlorophenol (ash) Oil combustion (Swiss) TCDD 4 .8 3.3 10 960 1.1 i* 5.2 17 100 PCDD 32 2.6 6 20 1.400 33. i 14 ' 58 160 HiCDD 81 8.7 10 40 2,000 570 1,540 9-27 56 74 180 HpCDD (U9/9) 117 42 4 100 640 260 17,000 90-135 172 18 130 OCDD 198 96 1 140 210 4,000 >1 7.000 575-2,510 710 6 40 TCDD CDD .009 .005 .10 .032 .18 .0002 small 0 .005 .1 .16 OCDD CDD .45 .61 .032 .45 .04 .82 >.5 .8:9 .74 .035 .066 *i = Interference precludes determining values the equipment is part of the processing plant, the accumulated material is recycled if possible. On the other hand, holding lagoons and spray ponds may be cleaned only occasionally or else residue may accumulate until the lagoon is bypassed by some alternative device. In the latter case, residues may require removal to prevent impacting future land use. For the field sites surveyed, Plants A and C currently transfer residual sludge or ash to onsite landfills by direct hauling. Plant B's residue impacts the environment as a continuous minor land application is effected indirectly through lagoon bottom buildup. The character of this material is presented in Table 5. Plant A had a similar practice that was aban- doned for evaporation. The high values of spray pond components in Table 5 indicate that incoming waste eventually decreases in concentration while the bottom sludge increases. Higher molecular weight organics are not emitted very rapidly at low temperatures. Thus it is assumed that toxic organics settle onto the lagoon bottom and remain therefor some period of time. Residues are thereby slowly transferred to land, albeit with undocumented environmental effects. ------- Table 5. Characterization of wood preserving solid residues (concentrations in g/g) Sample location Cylinder Spillage and Dnppage Pan Evaporator Sludge Evaporation Pond Incineration Ash Compound Pentachlorophenol Phenol Fluoranthene Naphthalene Benzo(a)anthracene Benzo(a)pyrene Benzofluoranthenes Chrysene A cenaphthylene Anthracene Benzol g. h, ijperylene Fluorene Phenanthrene Dibenzo(a,h)anthracene lndeno(1.2,3-c,d)pyren Pyrene Benzene Toluene Ethylbenzene Other PNAs COO CDF *Not detectable. ** Abandon pond. Penta treating 1,800 <10 JOS 125 70 28 40 68 13 51 >40 125 235 <10 <10 82 0.1 0.3 <0.3 Creosote treating 1,100 <20 310 1.350 940 220 600 780 126 1,350 40 1,850 2.150 20 50 1,000 7 <1 <1 Penta treating 620 1.2 2.0 1.1 0.5 .05 0.2 0.4 .05 .5 1.0 3.5 <0.1 <0.1 1.4 <0.2 0.3 <0.2 2. 0. Creosote treating 260 30 590 680 390 91 190 240 840 260 10 660 1.100 <10 16 440 6.7 1.4 0.3 2** 4** Bottom sludge 15.000 <50 5.800 1.500 2.600 * * 2,000 * 1,700 * 5,600 9,000 # * 4,400 490 2.1 1.4 Recycle water 15 >.1 3 3.1 2.5 * * 3.4 # 0.7 # 1.8 6.9 * * 1.4 O.3 — — Bottom ash 0.5 0.8 36 12 2.8 0.5 3.4 0.7 2.5 1.9 — 0.5 19 — — — Mechanical hopper ash 2.7 0.1 0.9 6 0.1 0.1 0.1 0.2 0.1 0.1 — 0.1 0.5 — — — 0.4-2.3 0.1-1.1 B. DaRos, R. Merrill. H. K. Willard, and C. D. Wolbach are with Acurex Corp., Mountain View, CA 94042. Donald Wilson is the EPA Project Officer (see below). The complete report, entitled "Emissions and Residue Values from Waste Disposal During Wood Preserving." (Order No. PB 82-234 246; Cost: $19.50. subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Industrial Environmental Research Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 OUSGPO: 1982 — 559-092/0496 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 RETURN POSTAGE GUARANTEED PS U $ CHICAGO 00005i29 tNVlH LIBRAE S UEAROOKN SIKEET IL 006U4 ------- |