Pollution Prevention and Abatement Handbook WORLD BANK GROUP Effective July 1998

Wood Preserving

Industry Description and Practices and the treated wood storage areas. Some of the major pollutants present in drips, surface runoff, Wood preserving involves imparting protective and contaminated soil include polynuclear aro- properties to wood to guard against weathering matic hydrocarbons, pentachlorophenol, pesti- and attack by pests. Three main types of preser- cides, dioxins, chrome, copper, and arsenic. vatives are used: water based (for example, so- dium phenylphenoxide, benzalconium chloride, Pollution Prevention and Control guazatin, and copper chrome arsenate); organic solvent based (for example, pentachlorophenol Wood preserving involves different combinations and such substitutes as propiconazol, tebuco- of a wide variety of processes, and there are many nazol, lindane, permethrin, triazoles, tributyltin opportunities to improve on the traditional prac- compounds, and copper and zinc naphthenates); tices in the industry. The following improvements borates; and tar oils (such as creosote). Note that should be implemented where feasible. some of the preservatives mentioned here (for example, lindane, tributyltin, and pentachlorophenol) are • Do not use pentachlorophenol, lindane, banned in some countries and are not to be used. tributyltin, or copper chrome arsenate (or its The preservatives are applied to the surface of derivatives). wood by pressure impregnation, with a pressure • Give preference to pressurized treatment pro- range of 800 kilopascals (kPa) to 1,400 kPa; by cesses to minimize both wastage of raw materi- deluging (mechanical application by flooding or als and the release of toxics that may be present. spraying), by dipping or immersion; and by ther- • Minimize drippage by effective removal of mal processing (immersion in a hot bath of pre- extra preservative from the wood surface by servative). Application of vacuum helps to mechanical shaking until no drippage is no- improve the effectiveness of the process and to ticeable. Provide sufficient holding time af- recover some of the chemicals used. Pesticides ter preservative application to minimize free are applied using appropriate protective cloth- liquid. ing, including gloves, aprons, overalls, and in- • Recycle collected drips after treatment, if halation protection. necessary. • Heat treated wood when water-based preser- Waste Characteristics vatives are used. • Use concrete pads for the wood treatment area Any or all of the substances used in wood pre- and intermediate storage areas to ensure serving, such as preservatives and solvents, can proper collection of drippage. Treated wood be found in the drips and the surface runoff should be sent for storage only after drippage streams. Air emissions of solvents and other vola- has completely stopped. tile organics result from the surface treatment • Minimize surface runon by diversion of steps, drying of the treated wood, and storage stormwater away from the process areas. and transfer of chemicals. Soil contamination • Cover process areas and collect surface runoff may result from the drippage and surface run- for recycling and treatment. Where water- off, and this may happen near the process areas based preservatives are used, prevent freshly

433 434 PROJECT GUIDELINES: INDUSTRY SECTOR GUIDELINES

treated wood from coming into contact with ronmental assessment (EA) process on the basis of rainwater. country legislation and the Pollution Prevention and • Sites should be selected that are not prone to Abatement Handbook, as applied to local conditions. flooding or adjacent to water intake points or The emissions levels selected must be justified in valuable groundwater resources. the EA and acceptable to the World Bank Group. • Preservatives and other hazardous substances The guidelines given below present emissions should be stored safely, preferably under a roof levels normally acceptable to the World Bank with a spill collection system. Group in making decisions regarding provision • Proper labels should be applied, and used of World Bank Group assistance. Any deviations packaging should be returned to the supplier from these levels must be described in the World for reuse or sent for other acceptable uses or Bank Group project documentation. The emis- destruction. sions levels given here can be consistently achieved by well-designed, well-operated, and Target Pollution Loads well-maintained pollution control systems. The guidelines are expressed as concentrations Minimize contamination of surface runoff and to facilitate monitoring. Dilution of air emissions soil. Have a closed system for managing liquids or effluents to achieve these guidelines is un- to avoid the discharge of liquid effluents. acceptable. All of the maximum levels should be achieved Treatment Technologies for at least 95% of the time that the plant or unit is operating, to be calculated as a proportion of Air Emissions annual operating hours.

Exhaust streams should be treated, using carbon Air Emissions filters that allow the reuse of solvents, to reduce volatile organic compounds (VOCs) to acceptable The maximum air emission level from wood im- levels before venting to the atmosphere. Where pregnation areas for VOC is 20 milligrams per VOC recovery is not feasible, destruction is carried normal cubic meter (mg/Nm3). out in combustion devices or bio-oxidation systems. Liquid Effluents Liquid Effluents Wood-preserving plants should use closed sys- The main treatment process is recycling of col- tems, where feasible, or should attain the efflu- lected drips and surface runoff after evaporation. ent levels presented in Table 1. Other processes include detoxification (using ul- traviolet oxidation) and precipitation or stabili- Sludges zation of heavy metals. Wherever possible, generation of sludges and Solid and Hazardous Wastes contaminated soil should be minimized. Con- taminated soil and sludges must be treated, sta- Contaminated soil may contain heavy metals and bilized, and disposed of in an approved, secure toxic organics and should normally be managed landfill. The levels of toxics in the leachate should as hazardous waste. Treatment methods include be the same as for liquid effluents. incineration of toxic organics and stabilization of heavy metals. Ambient Noise

Emissions Guidelines Noise abatement measures should achieve either the levels given below or a maximum increase in Emissions levels for the design and operation of background levels of 3 decibels (measured on the each project must be established through the envi- A scale) [dB(A)]. Measurements are to be taken Wood Preserving 435

Table 1. Effluents (Including Surface Runoff) operating standards so that any necessary correc- from the Wood-Preserving Industry tive actions can be taken. Records of monitoring (milligrams per liter, except for pH) results should be kept in an acceptable format. The Parameter Maximum value results should be reported to the responsible au- thorities and relevant parties, as required. pH 6–9 TSS 50 Key Issues COD 150 Oil and grease 10 Phenol 0.5 The key production and control practices that will Arsenic 0.1 lead to compliance with emissions guidelines can Chromium be summarized as follows: Hexavalent 0.1 Total 0.5 • Do not use pentachlorophenol, lindane, Copper 0.5 tributyltin, copper chrome arsenate, or other Fluorides 20 preservatives that are considered toxic and for Polynuclear aromatic hydrocarbons which less toxic alternatives are available for (PAHs), such as benzo(a)pyrene (each) 0.05 wood treatment systems. Dioxins/furans (total) 0.0005 • Use pressurized treatment processes. Pesticides (each) 0.05 • Heat treated wood when water-based preser- Note: Effluent requirements are for direct discharge to surface vatives are used. waters. • Minimize drippage carryover by ensuring that drippage has completely stopped before re- at noise receptors located outside the project moving the treated wood from the process property boundary. area. Collect and recycle drip solutions, and put in place total recycle systems for liquids Maximum allowable log and effluents. equivalent (hourly • Use concrete pads for the wood treatment and measurements), in dB(A) intermediate storage areas. Day Night Receptor (07:00–22:00) (22:00–07:00) • Divert stormwater away from process areas. Collect and treat surface runoff. Residential, • Recycle solvent vapors, where feasible; other- institutional, wise, they should be destroyed in a combus- educational 55 45 tion device or in a bio-oxidation system. Industrial, • Manage contaminated soil and sludges as haz- commercial 70 70 ardous wastes.

Monitoring and Reporting Sources

Daily monitoring of the parameters listed in this United States. 1990. “Wood Preserving; Identification document, except for metals, should be carried and Listing of Hazardous Waste: Final Rule.” Fed- out to provide an indication of overall treatment eral Register, vol. 55, no. 235, December 6. reliability. Metals should be sampled at least World Bank. 1995. “Industrial Pollution Prevention and monthly. More frequent sampling may be re- Abatement: Wood Preserving Industry.” Draft Tech- quired for certain batches and during wet nical Background Document. Environment Depart- weather conditions. ment, Washington, D.C. Monitoring data should be analyzed and re- viewed at regular intervals and compared with the