Handbook of Industrial and Hazardous Wastes Treatment
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22 Treatment of Pesticide Industry Wastes Joseph M. Wong Black & Veatch, Concord, California, U.S.A. 22.1 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 US 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. 22.2 THE PESTICIDE INDUSTRY The pesticide industry is an important part of the economy. Worldwide and US 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 1005 Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. 1006 Wong 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 US 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 Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. Treatment of Pesticide Industry Wastes 1007 22.2.1 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 Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. 1008 Wong 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). Figure 1 Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. Treatment of Pesticide Industry Wastes 1009 General process flow diagram for halogerated aliphatic acid production facilities. Major processes for pesticide production, Figure 2 including chlorination, cooling, crystallization, centrifying, and drying. The salt of the pesticide is produced by another route (from Ref. 8). Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. 1010 Wong ation, filtering, General process flow diagram for nitro-type pesticides. Major processes for pesticide production are mononitration, dinitration, filtration, amin and vacuum distillation (from Ref. 8). Figure 3 Copyright #2004 by Marcel Dekker, Inc. All Rights Reserved. Treatment of Pesticide Industry Wastes 1011 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.