Waste Treatment in the Process Industries - Chapter 11 pptx

11 Treatment of Pesticide Industry Wastes Joseph M. Wong Black & Veatch, Concord, California, U.S.A. 11.1 INTRODUCTION Pesticides are chemical or biological substances intended to control weeds, insects, fungi, rodents, bacteria, and other pests. They protect food crops and livestock, control household pests, promote agricultural productivity, and protect public health. The importance of pesticides to modern society can be summarized by a statement made by Norman E. Borlaug, the 1970 Nobel Peace Prize winner: “Let’s get our priorities in perspective. We must feed ourselves and protect ourselves against the health hazards of the world. To do that, we must have agricultural chemicals. Without them, the world population will starve” [1]. However, the widespread use of pesticides has also caused significant environmental pollution problems. Examples of these include the biological concentration of persistent pesticides (e.g., DDT) in food chains and contamination of surface and groundwater used for drinking sources. Because they can affect living organisms, pesticides are highly regulated in the United States to ensure that their use will be safe for humans and the environment. Recently, the National Research Council’s Committee on the Future Role of Pesticides in U.S. Agriculture conducted a comprehensive study and concluded that although they can cause environmental problems, chemical pesticides will continue to play a role in pest management for the foreseeable future. In many situations, the benefits of pesticide use are high relative to risks or there are no practical alternatives [2]. This chapter deals with the characterization, environmental regulations, and treatment and disposal of liquid wastes generated from the pesticide industry. 11.2 THE PESTICIDE INDUSTRY The pesticide industry is an important part of the economy. Worldwide and U.S. pesticide sales in 1990 were expected to reach more than $20 billion and $6 billion, respectively (Chemical Week, January 3, 1990). Usually the highest usage of pesticides is in agriculture, accounting for about 80% of production [3]. Agricultural pesticide use in the United States averaged 1.2 billion pounds of ingredient in 1997, and was associated with expenditures exceeding $11.9 billion. This use involved over 20,700 products and more than 890 active ingredients [2]. Household and garden pesticide uses are other significant markets. The United States constituted about 40% of 499 © 2006 by Taylor & Francis Group, LLC the world market for household pesticides, with annual sales exceeding $1 billion in 2002 [4]. China is the second largest national market with over $580 million of household insecticides purchased each year [5]. The United States also dominates the world market for garden pesticides with sales of over $1.5 billion per year. The United Kingdom is a distant second with sales of $155 million [5]. Pesticides are classified according to the pests they control. Table 1 lists the various pesticides and other classes of chemical compounds not commonly considered pesticides but included among the pesticides as defined by U.S. federal and state laws [1]. The four most widely used types of pesticides are: (a) insecticides, (b) herbicides, (c) fungicides, and (d) rodenticides [6]. The major components of the pesticide industry include manufacturing and formulation/ packaging [7]. During manufacture, specific technical grade chemicals are made. Formulating/ packaging plants blend these chemicals with other active or inactive ingredients to achieve the endproducts’ desired effects, and then package the finished pesticides into marketable containers. A brief overview of these sectors of the industry follows. Table 1 Pesticide Classes and Their Uses Pesticide class Function Acaricide Kills mites Algicide Kills algae Avicide Kills or repels birds Bactericide Kills bacteria Fungicide Kills fungi Herbicide Kills weeds Insecticide Kills insects Larvicide Kills larvae (usually mosquito) Miticide Kills mites Molluscicide Kills snails and slugs (may include oysters, clams, mussels) Nematicide Kills nematodes Ovicide Destroys eggs Pediculicide Kills lice (head, body, crab) Piscicide Kills fish Predicide Kills predators (coyotes, usually) Rodenticide Kills rodents Silvicide Kills trees and brush Slimicide Kills slimes Termiticide Kills termites Chemicals classed as pesticides not bearing the -cide suffix: Attractant Attracts insects Chemosterilant Sterilizes insects or pest vertebrates (birds, rodents) Defoliant Removes leaves Desiccant Speeds drying of plants Disinfectant Destroys or inactivates harmful microorganisms Growth regulator Stimulates or retards growth of plants or insects Pheromone Attracts insects or vertebrates Repellent Repels insects, mites and ticks, or pest vertebrates (dogs, rabbits, deer, birds) Source: Ref. 1 500 Wong © 2006 by Taylor & Francis Group, LLC 11.2.1 Pesticide Manufacturing There are more than 100 major pesticide manufacturing plants in the United States. Figure 1 presents the geographical locations of these plants [7]. Specific pesticide manufacturing operations are usually unique and are characteristic only of a given facility. Almost all pesticides are organic compounds that contain active ingredients for specific applications. Based on 500 individual pesticides of commercial importance and perhaps as many as 34,000 distinct major formulated products, pesticide products can be divided into six major groups [8]: 1. Halogenated organic. 2. Organophosphorus. 3. Organonitrogen. 4. Metallo-organic. 5. Botanical and microbiological. 6. Miscellaneous (not covered in the preceding groups). Plants that manufacture pesticides with active ingredients use diverse manufacturing processes, including synthesis, separation, recovery, purification, and product finishing such as drying [9]. Chemical synthesis can include chlorination, alkylation, nitration, and many other substitution reactions. Separation processes include filtration, decantation, extraction, and centrifugation. Recovery and purification are used to reclaim solvents or excess reactants as well as to purify intermediates and final products. Evaporation and distillation are common recovery and purification processes. Product finishing may involve blending, dilution, pelletizing, packaging, and canning. Examples of production facilities for three groups of pesticides follow. Halogenated Aliphatic Acids Figure 2 shows a simplified process flow diagram for halogenated aliphatic acid production facilities [8]. Halogenated aliphatic acids include chlorinated aliphatic acids and their salts, for example, TCA, Dalapon, and Fenac herbicides. Chlorinated aliphatic acids can be prepared by nitric acid oxidation of chloral (TCA) or by direct chlorination of the acid. The acids can be sold as mono- or dichloro acids, or neutralized to an aqueous solution with caustic soda. The neutralized solution is generally fed to a dryer from which the powdered product is packaged. As shown on Figure 2, wastewaters potentially produced during the manufacture of halogenated aliphatic acids include the following: . vent gas scrubber water from the caustic soda scrubber; . wastewater from the chlorinator (reactor); . excess mother liquor from the centrifuges; . process area cleanup wastes; . scrubber water from dryer units; . washwater from equipment cleanout. Nitro Compounds This family of organonitrogen pesticides includes the nitrophenols and their salts, for example, Dinoseb and the substituted dinitroanilines, trifluralin, and nitralin. Figure 3 shows a typical commercial process for the production of a dinitroaniline herbicide [8]. In this example, a chloroaromatic is charged to a nitrator with cyclic acid and fuming nitric acid. The crude product is then cooled to settle out spent acid, which can be recovered and recycled. Oxides of nitrogen Treatment of Pesticide Industry Wastes 501 © 2006 by Taylor & Francis Group, LLC Figure 1 Geographical distribution of major pesticide manufacturers in the United States. Most of the plants are located in the eastern half of the continent (from Ref. 7). 502 Wong © 2006 by Taylor & Francis Group, LLC Figure 2 General process flow diagram for halogerated aliphatic acid production facilities. Major processes for pesticide production, including chlorination, cooling, crystallization, centrifying, and drying. The salt of the pesticide is produced by another route (from Ref. 8). Treatment of Pesticide Industry Wastes 503 © 2006 by Taylor & Francis Group, LLC Figure 3 General process flow diagram for nitro-type pesticides. Major processes for pesticide production are mononitration, dinitration, filtration, amination, filtering, and vacuum distillation (from Ref. 8). 504 Wong © 2006 by Taylor & Francis Group, LLC are vented and caustic scrubbed. The mononitrated product is then charged continuously to another nitrator containing 100% sulfuric acid and fuming nitric acid at an elevated temperature. The dinitro product is then cooled and filtered (the spent acid liquor is recoverable), the cake is washed with water, and the resulting washwater is sent to the wastewater treatment plant. The dinitro compound is then dissolved in an appropriate solvent and added to the amination reactor with water and soda ash. An amine is then reacted with the dinitro compound. The crude product is passed through a filter press and decanter and finally vacuum distilled. The saltwater layer from the decanter is discharged for treatment. The solvent fraction can be recycled to the reactor, and vacuum exhausts are caustic scrubbed. Still bottoms are generally incinerated. Wastewaters potentially generated during the manufacture of the nitro family of pesticides include the following: . aqueous wastes from the filter and the decanter; . distillation vacuum exhaust scrubber wastes; . caustic scrubber wastewaters; . periodic kettle cleanout wastes; . production area washdowns. Metallo-Organic Pesticides Metallo-organic active ingredients mean organic active ingredients containing one or more metallic atoms, such as arsenic, mercury, copper, and cadmium, in the structure. Figure 4 shows a general process flow diagram for arsenic-type metallo-organic pesticide production [8]. Monosodium acid methanearsenate (MSMA) is the most widely produced organoarsenic herbicide in this group. The first step of the process is performed in a separate, dedicated building. The drums of arsenic trioxide are opened in an air-evacuated chamber and automatically dumped into 50% caustic soda. A dust collection system is used. The drums are carefully washed with water, the washwater is added to the reaction mixture, and the drums are crushed and sold as scrap metal. The intermediate sodium arsenite is obtained as a 25% solution and is stored in large tanks prior to further reaction. In the next step, the 25% sodium arsenite is treated with methyl chloride to produce the disodium salt DSMA (disodium methanearsenate, hexahydrate). This DSMA can be sold as a herbicide; however, it is more generally converted to MSMA, which has more favorable application properties [8]. To obtain MSMA, the DSMA solution is partially acidified with sulfuric acid and the resulting solution concentrated by evaporation. As the aqueous solution is being concentrated, a mixture of sodium sulfate and sodium chloride precipitates out (about 0.5 kg per 100 kg of active ingredient). These salts are a troublesome disposal problem because they are contaminated with arsenic. The salts are removed by centrifugation, washed in a multistage, countercurrent washing cycle, and then disposed of in an approved landfill. Methanol, a side product of methyl chloride hydrolysis, can be recovered and reused. In addition, recovered water is recycled. The products are formulated on site as solutions and are shipped in 1 to 30 gallon containers. Wastewaters that can be generated from the production of these pesticides include the following: . spillage from drum washing operations; . washwater from product purification steps; . scrub water from the vent gas scrubber unit; . process wastewater; Treatment of Pesticide Industry Wastes 505 © 2006 by Taylor & Francis Group, LLC Figure 4 General process flow diagram for arsenic-type metallo-organic production. Sodium arsenate is formed in the first reactor, disodium methanearsenate (DSMA) in the second reactor; DSMA is purified as a product or further changed to monosodium methanearsenate (MSMA) by acidification and purified (from Ref. 8). 506 Wong © 2006 by Taylor & Francis Group, LLC . area washdowns; . equipment cleanout wastes. 11.2.2 Pesticide Formulating/Packaging After a pesticide is manufactured in its relatively pure form (the technical grade material) the next step is formulation – processing a pesticide compound into liquids, granules, dusts, and powders to improve its properties of storage, handling, application, effectiveness, or safety [9]. The technical grade material may be formulated by its manufacturer or sold to a formulator/ packager. In the United States, there are more than a thousand pesticide formulating/packaging plants covering a broad range of formulations [7]. Many small firms have only one product registration, and produce only a few hundred pounds of formulated pesticides each year. However, USEPA [7] identified one plant operating in the range of 100 million pounds of formulated product per year. The approximate production distribution of formulators/packagers is presented in Table 2 [7]. The most important unit operations involved in formulation are dry mixing and grinding of solids, dissolving solids, and blending [8]. Formulation systems are virtually all batch-mixing operations. The units may be completely enclosed within a building or may be in the open, depending primarily on the geographical location of the plant. Production units representative of the liquid and solid formulation/packaging equipment in use as well as wastewater generation are described in the following. Liquid Formulation Units A typical liquid formulation unit is depicted in Fig. 5 [8]. Until it is needed, technical grade pesticide is usually stored in its original shipping container in the warehouse section of the plant. When this material is received in bulk, however, it is transferred to holding tanks for storage. Batch-mixing tanks are frequently open-top vessels with a standard agitator and may or may not be equipped with a heating/cooling system. When solid technical grade material is used, a melt tank is used before this solid material is added to the mix tank. Solvents are normally stored in bulk tanks and are either metered into the mix tank or are determined by measuring the tank level. Necessary blending agents (emulsifiers, synergists, etc.) are added directly. From the mix tank, the formulated material is frequently pumped to a holding tank before being put into containers for shipment. Before packaging, many liquid formulations must be filtered by conventional cartridge filters or equivalent polishing filters. Air pollution control equipment used on liquid formulation units typically involves exhaust systems at all potential sources of emission. Storage and holding tanks, mix tanks, and Table 2 Formulator/Packager Production Distribution Production (million lb/year) Formulator/ Packagers (%) ,0.5 24 .0.5 to ,5.0 41 .5.0 to ,50 35 Total 100 Source: Ref. 7. Treatment of Pesticide Industry Wastes 507 © 2006 by Taylor & Francis Group, LLC Figure 5 Liquid formulation unit. Technical grade pesticide products are blended with solvents and emulsifiers or other agents in a mix tank. Formulated products are filtered before packaging (from Ref. 8). 508 Wong © 2006 by Taylor & Francis Group, LLC [...]... Source control and waste minimization can be extremely effective in reducing the costs for inplant controls and end-of-pipe treatment, and in some cases can eliminate the need for some treatment units entirely The first step is to prepare an inventory of the waste sources and continuously monitor those sources for flow rates and contaminants The next step is to develop in- plant operating and equipment... technical Chlorobenzene 4-Chloro-m-cresol Chloroform o-Chlorophenol 4-Chloro-o-toluidine hydrachloride Creosote Cresylic acid (cresols) Cyclohexane Cyclohexanone Decachlorooctahydro-1,3,4-metheno-2Hcyclobuta[c,d]-pentalen-2-one (Kepone, chlordecone) 1,2-dibromo-3-chloropropane (DBCP) Dimbutyl phthalate S-2, 3-( Dichloroallyl diisopropylthiocarbamate) (diallate, Avadex) o-Dichlorobenzene p-Dichlorobenzene Dichlorodifluoromethane... particular wastewater stream Porras-Rodriguez and Talens-Alesson [42] found that flocs resulting from the adsorption of Al3þ to lauryl sulfate micelles possessed pollutant-sequestering properties In studies conducted by these researchers, the pesticide 2,4-D appeared to associate with the micelle-bound Al3þ following a Guoy – Chapman – Stern isotherm 11. 5.3 End-of-Pipe Treatment Methods End-of-pipe treatment. .. and COD Biological treatment involves using microorganisms (bacteria) under controlled conditions to consume organic matter in the wastewater as their food, making this a useful process for removing certain organic materials from the wastewater Because the process deals with living organisms, every factor in uencing the growth and health of the culture must be considered, including an adequate food... alcohol Aluminum phosphide 4-Aminopyridine Arsenic acid Arsenic pentoxide Arsenic trioxide Calcium cyanide Carbon disulfide p-Chloroaniline Cyanides (soluble cyanide salts) Cyanogen 2-Cyclohexyl-4,6-dinitrophenol Dieldrin 0,0-Diethyl S-[2-ethylthio)ethyl] phosphorodithioate (disulfoton, Di-Systonw) 0,0-Diethyl 0-pyrazinyl phosphorothioate (Zinophosw) Dimethoate 0,0-Dimethyl 0-p-nitrophenyl phosphorothioate... Photodegradation of the insecticide followed a pseudo-first-order kinetics described by the Langmuir– Hinshelwood equation Photocatalytic oxidation of the fungicide metalaxyl in aqueous suspensions containing TiO2 was explained in terms of the Langmuir– Hinshelwood kinetic model [37] Resin Adsorption Adsorption by synthetic polymeric resins is an effective means for removing and recovering specific chemical... raw materials as 2,4,5-trichlorophenol (2,4,5-T) and 1,2,4,5-tetra-chlorobenzene, which are characteristic of TCDD precursors A TCDD level as high as 111 mg/L has been found in drums of waste from the production of the pesticide 2,4,5-T Other Pollutants The pesticide industry routinely monitors conventional and nonconventional pollutants in manufacturing wastewaters According to the USEPA surveys [7],... with the regulations for liquid waste disposal, which is mainly under the CWA However, when the waste is disposed of as a hazardous waste, it is regulated by the RCRA 11. 4.1 Clean Water Act The U.S Congress enacted the Federal Water Pollution Control Act (FWPCA) in 1972 The act was significantly amended in 1977 and has since become known as the CWA It was again amended by the Water Quality Act of 1987 The. .. methanol, ethylamine, and ammonia [11] Thus, this process is used to reduce or remove organic solvents from waste Figure 9 Steam-stripping flow diagram The in uent is heated by the stripper effluent before entering the stripping column near the top; the liquid stream flows downward through the packing, and steam flows upward, carrying volatile compounds; the overhead is condensed and liquid returned to the column;... and pyrolyze the adsorbate Both the infrared furnace and fluidized bed reactivation processes have been pilottested by USEPA in drinking water treatment plants [18] Other adsorbing materials besides GAC have also been investigated for treating pesticidecontaining wastewaters [19] Kuo and Regan [20] investigated the feasibility of using spent mushroom compost as an adsorption medium for the removal of . alkaline condition, or in the presence of a free halogen. The end reaction results in either direct dioxin, intermediate dioxin, or predioxin formation that will ultimately form dibenzo-p-dioxins. occur in their manufacturing wastewaters due to imperfect separations. 11. 3.2 Pesticide Formulating/Packaging Washing and cleaning operations provide the principal sources of wastewater in formulating. washed with water, and the resulting washwater is sent to the wastewater treatment plant. The dinitro compound is then dissolved in an appropriate solvent and added to the amination reactor with