section 2 small-scale enterprises · section 2 small-scale enterprises ... and a description of the...

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SECTION 2

SMALL-SCALE ENTERPRISES

This section defines the term small and medium-scale enterprise (SMSE) and discussesthe significance of these firms in environmental degradation. This includes a discussion of theimpact of industrial wastes on human health and the environment, a comparison of SMSE andlarger enterprises, and a description of the types of economic activities undertaken by SMSE.This is followed by industry profiles of four highly polluting SMSEs that may be goodcandidates for centralized waste treatment: tanneries, wet-end textile operations, electroplatingshops, and food processing operations. These profiles examine waste characteristics, wasteminimization options, and onsite treatment options for each industrial sector.

2.1 DEFINITION OF SMALL AND MEDIUM-SCALE ENTERPRISE

This manual uses the term “small and medium-scale enterprise” broadly to include anyenterprise that involves relatively few individuals or employees engaged in activities that createwaste byproducts. Any references in this manual to "small firms" or "small enterprises" referto SMSEs as defined here. SMSEs in newly industrialized countries are characterized bysimple, labor-intensive manufacturing methods. Equipment is often secondhand, and themanufacturing process is often inefficient compared with larger industries (Benavides, 1992).SMSEs are heterogeneous, differing in size and composition from city to city and country tocountry. Significant variations exist in the numbers of employees, production, wastegeneration, levels of capitalization, degree of spatial concentration, and technologicalprocesses employed (UMP, 1992). The characteristics of, and the solutions to, hazardouswaste problems associated with SMSEs, therefore, are location and process-specific, and onlylocal actions can solve these problems (UMP, 1992).

Various terms are used to describe and differentiate portions of this economicsector. Table 2-2 identifies several terms and criteria used to define economic activities basedon the number of workers or employees involved. The Urban Management Program (UMP) ofthe United Nations Development Program (UNDP)/United Nations Center for HumanSettlements (UNCHS)/World Bank uses the term small-scale industry (SSI) to include cottageenterprises in addition to formal SMSEs, which are registered with government regulatory ordata-gathering agencies. Cottage or artisan enterprises include household activities andworkshops and are usually resistant to change. Microenterprises, mostly located in theinformal sector (i.e., unregistered), tend to be undercapitalized, marginal producers but cangrow rapidly and adapt to new technologies when given the opportunity. As an example, Table2-1 includes definitions of small-scale enterprises commonly used in Peru.

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Table 2-1. Small scale-enterprise. Definitions used in Peru

SMALL-SCALE ENTERPRISE. DEFINITIONS USED IN PERU

a. According to a survey applied to 40 employees of 13 banks, the small-scale enterprise is definedas that selling between US$ 40,000 and US$ 750,000 annually and owning assets worth US$20,000 to US$ 30,000.

b. According to the Small and Micro-Scale Enterprise Promotion Law (L.D. No. 705, of November5, 1991), the small-scale enterprise has the following characteristics: no more than 20 workersand employees in total and a total sales value not higher than 25 “tax units” (in 1995, US$50,000).

c. COFIDE defines the small-scale enterprise as that with fixed assets not surpassing US$ 250,000,excluding land and facilities, and whose net annual sales do not surpass one million dollars.

d. According to Fernando Villarán (Reestructuración Anual: Subprogramas de Ajuste Estructural,Pequeña y Mediana Empresa Industrial. Lima: UNDP-UNIDO), a small-scale enterprise is thatenterprise with 5 to 19 workers and a capital of US$ 3,000.

e. According to Wong Cam, a small-scale enterprise is one that has 5 to 49 workers.

Source: Wong Cam, David. “Los grandes pequeños negocios”. Lima: Universidad del Pacífico.Centro de investigación; 1996.

As Table 2-1 indicates, criteria for defining enterprises based on size vary considerably.The difference between an SMSE and a medium-scale enterprise ranges from 20 to 50employees, and the criteria for differentiating a medium-scale enterprise from a large-scaleenterprise range from 100 to 300 employees. For the purpose of evaluating the feasibility ofcommon effluent treatment plants (CETPs) and hazardous waste treatment centers (HWTCs),SMSEs and medium-scale enterprises should be classified according to the system already usedin the country in question.

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Table 2-2. Criteria for defining small-scale enterprises

Category UMP Thailand India Peru ECLACa

(Benavides, (Kent, (Kent, (Benavides, (UMP,b

1992) 1991) 1991) 1992) 1992)

Number of Employees

Handicraft 1-8

Microenterprise 1-4 1-10

Cottage 1-4

Very small scale <10

Small scale 10-49 <20 <50 5-19 11-50

Medium scale 50-300 20-100 50-100 20-199

Large scale >300 >100 >100 200+

aECLAC = Economic Commission for Latin America and the Caribbean.bUMP = Urban Management Programme (UNDP/UNCHS/World Bank).Sources: As indicated.

2.2 SIGNIFICANCE OF SMALL AND MEDIUM-SCALE ENTERPRISES INENVIRONMENTAL DEGRADATION

2.2.1 Impact of Industrial Wastes from SMSEs on Human Health and theEnvironment

Industrial wastes usually contain traces or larger quantities of the raw materials,intermediates, final products, coproducts, byproducts, and residuals of ancillary or processingchemicals used in a particular industrial process. Substances present in industrial wastes in anycountry include detergents, solvents, cyanides, heavy metals, organic acids, nitrogenoussubstances, fats, salts, bleaching agents, dyes, pigments, phenolic compounds, tanning agents,sulfides, and ammonia. The health hazards of these industrial wastes include exposure to highconcentrations of toxic chemicals causing poisoning and burns, or exposure to low doses forlong periods, which can induce chronic diseases, cancers, sterility, and reproductive problems.Significant buildups of heavy metals have been reported in almost all industrial urban areas ofSoutheast Asia, posing hazards to human health and aquatic organisms (Hamza, 1991).

Three priority environmental health problems are associated with inadequate hazardousmaterials handling and hazardous waste management by SMSEs:

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n The first involves workers who are exposed to hazardous materials on the job. Thehealth effects on workers and the community are very much determined by theprocesses employed, and therefore the chemicals used, as well as the proximity ofenterprises to residential areas and water and other resources (UMP, 1992). Thisproblem is exacerbated by the large number of employees in many SMSEs.

n The second problem is environmental degradation resulting from the pollutionimpacts of uncontrolled hazardous waste discharges affecting especially surface andground water, air, soils, and the food chain (UMP, 1992).

n The third problem is associated with health risks of waste handlers (formal andinformal) and people who live near non-controlled waste dumps.

Because most small firms are located within the heart of cities, the pollution they causeis often acutely felt by the local population, both in terms of impacts on human health and onenvironmental degradation (UNEP, 1987). Table 2-3 outlines health and environmental effectsof various industrial pollutants.

The potential pathways by which hazardous wastes can enter the human environmentare summarized in Figure 2-1. Some pathways correspond to a direct input to anenvironmental compartment, such as the evaporation of a chemical to the atmosphere. Otherpathways represent indirect inputs, such as the atmospheric deposition of windborne particulatematter to surface waters (Batstone et al., 1989). The environment can assimilate industrialeffluents through two major routes: by chemical decomposition into compounds that enter thenatural cycles or as food for living organisms whose waste also may enter the natural cycles.In some instances, assimilation makes the toxicant more accessible to higher animal forms. Forexample, mercury salts in sediments may be methylated by bacteria that are taken in by fish asmethylmercury and eventually accumulate in the human body (Hamza, 1991). As pollutionbecomes excessive, particularly in urban centers with heavy concentrations of population andindustry, overloading of the natural assimilative capacity becomes evident in watercourses,land, and air (Hamza, 1991).

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Table 2-3. Health and environmental effects of pollutants (Hamza, 1991)

COMPONENT GROUP EFFECTS

1. Bio-oxidable expressed asBOD (L,S,P,A)

Desoxygenation, anaerobic conditions, fish kills, stinks due to H2Sproduction.

2. Primary toxicants: As, CN,Cr, Cd, Cu, P, Hg, Pb, Zn, Co,Ni, Sn, Mn. (L,S,P,A)

Cardiac disturbances Ba, myocordial failure Co, CardiovascularDiseases Cd, Skin Cancer As, neurological disorders Pb, bronchialcancer Ni, menamata disease Hg, photophobia Sn, symptomssimulating Parkisons’s syndrome Mn, fish kills, accumulations inflesh of fish and mollusks.

3. Acids and alkalines (L, A) Disruption of pH buffer systems disordering previous ecologicalsystem.

4. Disinfectants Cl2, H2O2,formalin, phenol (G, L)

Formation of chlorophenols – extremely poisonous – residuesrepresent health hazard to humans and aquatic life, selective kills ofmicro-organisms, taste, and odours.

5. Ionic forms: Fe, Ca, Mg, Mn,Cl-, SO---

(S, P, L, A)

Changed water characteristics, staining, hardness, salinity,encrustations.

6. Oxidizing and reducingagents: NH3, NO2

-, NO3-, S--,

SO3--

(S, P, L, A)

NO3 cause infant methaemoglobinaemia (more than 40 mg/l), NO2

form nitrosamines (potant carcinogens), altered chemical balancesranging from rapid oxygen depletion to over nutrition, odours andthe mass development of plankton and eventually, eutrophication.

7. Oils and grease and evident tosight and smell (I)

Foaming, floating, and settleable solids; stinks; anaerobic bottomdeposits; oils, fats, and grease; waterfowl and fish injuries.

8. Pathogenic organisms B,anthracis,(L, A, S)

Infections in man, reinfection of livestock, plant diseases fromfungi-contaminated irrigation water; Leptospira, toxic fungi.

G Pollutant occurs as a gasL Pollutant occurs as a liquidS Pollutant occurs as a solidP Pollutant occurs in particulate formA Pollutant occurs in aqueous solution or suspension

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Figure 2-2. Physical and biological routes of transport of hazardous substances, theirrelease from disposal sites, and potential for human exposure (Batstone,1989)

2.2.1.1 Water Pollution

One of the most obvious environmental impacts of small enterprises is theircontribution to water pollution. SMSEs involved in industry cause water pollution bydischarging effluents into streams, rivers, and public drainage systems that flow into rivers andoceans.

Industrial effluents containing concentrations of heavy metals and other toxic substancesdischarged to water bodies pose hazards to human health and aquatic organisms as follows(Hamza, 1991):

n Toxic substances can have detrimental effects on human health. For example,cyanides inhibit the phosphorylative oxidation reactions that permit cellularrespiration; mercury and its compounds, especially methylmercury, are associatedwith a number of episodes characterized by impaired hearing, vision, and muscularcoordination, and in some outbreaks, by high mortality; and, lead, which isconsidered a global pollutant, can produce a variety of serious effects, includingneurological disorders.

n Fish kills are often the result of acute toxicity due to dumping of sludges oraccidental release of highly toxic matter in water bodies. Chronic toxicity due tosteady release of low-level toxic pollutants changes the entire aquatic population

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balance by destroying susceptible species and encouraging less desirable but moretolerant species to flourish, diminishing algal and invertebrate food supply, andaltering reproductive potential because eggs are more susceptible to sublethalconcentrations of toxicants than are adults.

n Many organic materials may be biologically degraded in water streams, therebycausing excessive oxygen demands. Complete exhaustion of dissolved oxygen in apolluted stream would render the water incapable of supporting fish life; and, in theabsence of dissolved oxygen, some of the microorganisms would use the oxygencombined in certain materials such as sulfates, thereby creating malodor andnuisance.

n Coloring matter may substantially decrease light penetration and hence affectphotosynthetic oxygen production; increased turbidity and bacterial loads representother aesthetic problems that also cause detrimental effects on water quality.

Small manufacturing enterprises also create solid wastes and sludges, which frequentlyare disposed of improperly on public lands or in unlined landfills (Kent, 1991). Toxic elementsof these solid wastes may eventually leach downward to contaminate ground waters. Groundwater is water that naturally flows through and is stored in soil and rock bodies beneath theland. It is a major source of drinking water and of water used in the industry. Ground-watercontamination can occur when liquids (usually rainwater) move through waste disposal sitesand into ground water, carrying pollutants with them. Once contaminated, ground water isexpensive and difficult, sometimes impossible, to clean up. The actual time scales regardingthe movement of contaminants out of a waste site are generally very long. It can take decadesfor a contaminant to migrate from a disposal site to nearby drinking wells. Once the chemicalappears in the well water, however, it may remain there in elevated amounts for many years,even if remedial action is taken at the disposal site. Furthermore, the arrival of one pollutant inwell water may signal the arrival of dozens more contaminants over the course of many years.

2.2.1.2 Land Pollution

Land contamination can occur in the following ways (Hamza, 1991):

n Uncontrolled disposal to land of industrial solid and hazardous wastes such asmetal-bearing sludges, concentrated spent acids and alkalies, organic residues, andwasted oils.

n Uncontrolled burning of solid wastes on land sites, leaving residuals of ash, burnedrubber, toxic chemicals, and other burned debris.

n Storage, either temporarily or permanently, of discarded chemicals, productionresidues, toxic wastes, putrescible matter, and industrial reject material.

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n Deposition of stack emissions, transferring toxic substances via the atmosphere tothe land.

n Soil pollution caused by industrial influents running uncontrolled over land.

Industrial wastes disposed of on land can be complex mixtures of organic and inorganichazardous chemicals in combination with other nonhazardous wastes. Such wastes can be inthe form of solids, sludges, or liquids or mixtures of all three. Several health and safetyimpacts arise from uncontrolled waste disposal practices, including breeding of disease carriersat sites of decomposing organic matter; contamination of crops, fish, and drinking water bydirect discharge or by leachate runoff from waste dumps; and fires and explosions due toimproper storage of hazardous residues. Aesthetic effects also occur, including unsightlinessdue to accumulation of waste heaps close to industrial and residential areas, and emission ofobnoxious odors from burning or decomposition of organic matter.

2.2.1.3 Air Pollution

Many SMSEs create smoke and fumes that contribute to the severe air pollutionproblems existing in most large Asian cities. Small foundries, rice mills, bakeries, restaurants,food processors, brick-making operations, and lead smelters burn fossil fuels that createemissions (Kent, 1991). Compared with large-scale plants, SMSEs contribute smaller loads ofair pollutants. Nevertheless, their effects are sometimes more pronounced due to thecumulative impact of concentrations of small polluting establishments located within aresidential area. The emitted pollutants cause direct damage to buildings, paintwork,unprotected steelwork, and public monuments in addition to creating a dirtier environment,which makes life unpleasant.

Air pollution problems are intensified due to the existence of clusters of small-scaleplants that operate obsolete equipment and generate significant gas and particle emissions withno provisions for pollution control. Solvents used in these plants, including aliphatic andaromatic hydrocarbons, alcohols, aldehydes, ketones, and chlorinated hydrocarbons, emit toxicvapors. A great number of occupational hazards occur due to the uncontrolled release ofsubstances such as lead, mercury, cadmium, polychlorinated hydrocarbons, and asbestos(WHO, 1985). Exposure may occur in different processes, such as degreasing of metals in themachine industry, extraction of fats or oils, dry cleaning, painting, and the plastics industries.Solvent vapors enter the body mainly by inhalation, although some skin absorption may occur.The vapors are absorbed from the lungs into blood and are distributed mainly to tissues with ahigh content of fat and lipids such as the central nervous system, liver, and bone marrow(Hamza, 1991).

Windblown dispersal is another potential pathway of release to the atmosphere(affecting people through inhalation). Certain solid wastes (e.g., asbestos) are particularlysusceptible to windblown dispersal. The mobilization of contaminated soil or the contaminantsthemselves may be a particular problem at poorly managed hazardous waste disposal sites.

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2.2.2 Small and Medium-Scale Enterprises and Environmental Degradation inRelation to Larger Enterprises

Accurately assessing the overall impact of SMSEs on the environment is difficultbecause of the complexity of the question, the diversity of SMSE activities, and the lack ofdata. SMSEs may be worse polluters than large firms because SMSEs are less technicallyefficient, harder to monitor, and less likely to adopt abatement technologies (Kent, 1991).Small manufacturers frequently lack the technical knowledge and the financial means tocontrol or reduce effluents from their operations. Consequently, SMSEs in aggregate are alarge source of water and airborne pollutants and have been associated with significantvolumes of toxic and hazardous waste (World Bank, 1994).

A 1991 report prepared for the U.S. Agency for International Development (U.S. AID)examined the relation between SMSEs and environmental degradation with emphasis on Asia(Kent, 1991). This report concludes that while SMSEs might not be responsible for mostenvironmental degradation, per unit of production, they probably are more severe pollutersthan large firms. According to this report, SMSEs pollute more per unit output for fourreasons:

n Technical inefficiencies in productionn Technical inefficiencies in waste treatment and inadequate waste managementn Difficulties involved in monitoring and regulating SMSEsn Insufficient training on environmental issues.

The World Bank analysis of India's industrial pollution suggests that suboptimal scalesof production can be blamed for technical inefficiencies that increase pollution per unit (Kent,1991). Small firms are likely to produce output in batches, rather than continuously, withassociated higher pollution levels (e.g., water pollution associated with flushing machineryused for printing, tanning, and dyeing after each small batch). Small-scale manufacturers alsotend to use nonautomated, less expensive equipment (Hamza, 1991). The use of inferiorequipment can result in the production of excessive wastes as well as considerable losses ofraw materials, lubricating oils, energy, and processed products.

Wastes from SMSEs in newly industrialized countries are often not adequatelymanaged. Wastes enter the municipal system, ending up in dumps, landfills, sewers, or rivers.Waste treatment is rare in small industries because of a lack of control, skilled personnel, andadequate space for traditional treatment systems, as well as the high cost of pollutionabatement technology (Benavides, 1992). In a recent report examining hazardous wastemanagement in newly industrialized countries, none of the countries reviewed in case studies(i.e., India, Mexico, Peru, Zimbabwe) had waste management policies tailor-made for SMSEs(Benavides, 1992).

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The third explanation for why small firms appear to pollute more than large firms perunit of output is that SMSEs are more difficult to monitor and regulate. Large-scalemanufacturers provide a relatively easy target for authorities in terms of regulating andcontrolling emissions and discharges, whereas the same is not always true for smallermanufacturers because of the large numbers involved and the variety of manufacturingactivities carried out (UNEP, 1987).

In addition to the above, a variety of studies produced under World Bank supervisionconcluded that achieving pollution control in SMSEs is hampered by a lack of financialresources and sufficiently trained personnel and also by space limitations. SMSEs are unlikelyto adopt abatement measures because they cannot afford them and are unable to exploiteconomies of scale in abatement technologies; when abatement measures are installed, theabsence of trained personnel means that proper and effective operation cannot be ensured; and,finally, SMSEs have space limitations, so they experience difficulties in installing treatmentsystems.

2.2.3 Types of Economic Activities in Which Small-Scale Enterprises AreInvolved

SMSEs are involved in hundreds of different activities in the newly industrializedworld, some of which are potentially more harmful to the environment than others.Individually, an SMSE might produce a small quantity of hazardous waste; collectively,however, a number of SMSEs produce a large enough quantity of hazardous waste to representa substantial hazard to the community and the environment. Table 2-4 outlines themanufacturing sectors where SMSEs represent a major source of production and wastegeneration in the newly industrialized world. The general list at the beginning of Table 2-4includes all sectors identified as significant in the 1992 Expert Group Meeting on LocalManagement of Hazardous Wastes From Small-Scale and Cottage Industries (UMP, 1992).

Several reports stress that generalizations and exaggerations about SMSEs andenvironmental degradation should be avoided (Kent, 1991; Benavides, 1992). The relativeimportance of SMSEs in pollution is low in certain sectors of specific countries and high inothers (Kent, 1991). In many economic activities and countries, SMSEs are much morenumerous than large-scale enterprises but produce less total output and presumably less totalpollution (e.g., tanneries in Indonesia). In other activities and countries, small enterprisesproduce the largest share of a limited number of industries' output and presumably the largestshare of pollution related to these industries (e.g., tanneries in India) (Kent, 1991).

Table 2-5 summarizes information on SMSEs in a number of newly industrializedcountries and indicates large variations from country to country and from sector to sector.Different sources and classification systems make direct comparisons difficult. Where SMSEsrepresent a large percentage of the total number of enterprises or employees, they often do notmaintain a proportionate share of production or value added. For example, in Peru, 99 percent

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of the enterprises are in the small, micro, and handicraft categories, yet they account for only26 percent of total production.

Table 2-4. Major manufacturing sectors for SMSE in newly industrialized countries

Country Enterprise

General (UMP, 1992)

(Numbers in parentheses indicate the numberof times identified in the individual countrylists below.)

Automobile repair shops and gas stations (3)Battery production/recyclingDyestuff producers (1)Electroplating/metalworking (8)a

Food processing and beverages (6)a

Metal foundries (3)Paint shops (1)Pharmaceuticals (1)Pesticide formulation (3)Printing (2)Tanneries (8)a

Textile dyeing (5)a

Wood and furniture (2)

AfricaZimbabwe (Mubvami, 1991) Metals, metal products, and engineering (28%/69%)c

Garaging and transport (20%/75%)Textiles, clothes, and leather, including tanneries(17%/60%)Paper and printing, including photographic shops(10%/67%)Other chemicals (medicines, soap, etc.) (9%/52%)

South AmericaMexico Tanneries

Peru Lima Industrial Waste Survey (Benavides, 1989)Paints and lacquers (15%)b

Tanneries (12%)Metallic products (11%)Electric appliances and supplies (9%)Pesticide formulators (8%)Major Small-Scale Industries (Benavides, 1992)Automotive servicesElectroplatingMetal mechanics (machine and metalworking shop)Textile weavingNonferrous foundriesTextile dyeing

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Country Enterprise

AsiaBangladesh Bricks and tiles

Food processing (rice milling)MetalworkingPrintingWooden furniture

Hong Kong Tanneries

India Drinks and tobaccoDyestuffs and dyestuffs intermediatesFood processing (sugar distilleries)Metal productsNonmetallic mineral productsPesticides manufacture and formulationPharmaceuticals and drugsPulp and paperSoap makersTanneries and fur productsTextiles (wet-end)Wood and furniture

Indonesia ElectroplatingFood processing (tapioca and tofu production)Lead smelting (air pollution)Metal castingPesticide repackagingTanneriesTextiles (batik dyeing)

Malaysia Food processing (palm oil mills)Detergent manufacturingElectroplatingRubber-based productsSteel and iron worksTanneries

Philippines ElectroplatingFood processors (fruit juices/cocktails, fried snacks)Tanneries

Thailand ElectroplatingFood processorsTanneriesTextiles (wet-end)

aHigh-priority sectors identified by Kent (1991).bPercentage of the total number of enterprises in a survey of 746 industries with 20 or more employees (only top fivecategories listed).cNumber of firms in manufacturing subsector as a percentage of all manufacturing firms (only top five listed)/small-scalefirms (<50 employees) as a percentage of the number of firms in the subsector.

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Table 2-5. Characteristics of SSEs in newly industrialized countries

Location Size Class/Type

Number (%) Employees (%) Production Value(%)

India, selectedSMSEsa

(Chemcontrol,1991; Kent,1991)

PharmaceuticalsDyestuffsPesticide form.Drinks/TobaccoWood/FurnitureLeather/FurNonmetalsMetal products

9,000 (97%)

350 (86%)8,500 MT(23.3%)80,000 MT(56.7%)

58.7%84.3%81.1%53.2%55.5%

Indonesia,selected SMSEsa

(Kent, 1991)

WholesaleManufacturingTransport/Comm.ConstructionMining/QuarryingFood industryWearing apparelMachinery

99%96%91%

6,280,000 (95%)3,184,000 (73%)940,000 (64%)928,000 (59%)295,000 (80%)

24%25%26%

Indonesia,tanneries(Kent, 1991)

Small (<20)Medium-Large

470 (87%)70 (13%)540

2,642 (26%)7,427 (74%)10,069

5,881 t/yr(12%)43,657 t/yr(88%)49,538

Leon, Mexico,Tanneries(Benavides,1992)

CottageSmall (1-6)Medium (6-16) Total

443 (76%)118 (20%)22 (4%)583

2,545 (15%)2,414 (21%)2,194 (64%)7,153

Peru (1987), allsectors(Benavides,1992)

HandicraftMicroSmallMediumLarge Total

55,000 (35%)84,300 (53%)17,100 (11%)2,300 (1%)206 (<1%)158,906

165,000 (23%)210,000 (32%)137,000 (18%)115,000 (15%)92,000 (12%)719,000

5%8%13%28%46%

Zimbabwe,Manufacturing(Mubvami, 1991)

0-5050-250>250 Total

651 (65%)258 (26%)91 (9%)1,000

aSMSE percentages expressed as a percentage of the total (SMSE plus larger enterprises).Sources: As indicated.

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On the other hand, in India, SMSEs account for more than half of total production orvalue in six industrial/commercial categories: pesticide formulation, drinks and tobacco, woodand furniture products, leather and fur, nonmetal products, and metal products.

In the case of microenterprises in Latin America, most of them carry out trading andservice delivery activities. These activities, with some exceptions, usually do not have asignificant environmental impact. However, some problems can arise due to lack of hygiene oradequate services in the work environment. On the other hand, productive activities usuallypose major human and environmental risks due to inputs and waste products from theseactivities, as well as to the presence of SMSEs in residential areas. The people most affectedcan be the owner and his family, employees and neighbors (IDB, 1997).

While the great majority of SMSEs do not work with hazardous materials or generatehazardous wastes, a small number of industrial subcategories create significant problems andrequire urgent attention (UMP, 1992). Four categories of SMSEs deserve special attention inseveral Asian countries for two reasons: (a) they are involved in industries that create largequantities of pollutants or highly toxic wastes, and (b) they are involved in industries in whichSMSEs are responsible for a major part of total production (Kent, 1991). These include:

n Leather tanning operationsn Wet-end textile operations (dyeing and finishing)n Electroplating and metalworking shopsn Food processing operations

These manufacturing sectors contribute to environmental degradation in the following ways:

n Small leather tanneries release significant quantities of chromium that threaten topoison ground water used for drinking.

n Textile bleaching and dyeing create heavily polluted wastewaters that flow directlyinto rivers or public canals that lead to rivers.

n Small electroplating shops also discharge toxic heavy metals to surface waters.

n Food processing industries create large quantities of high biological oxygen demand(BOD) wastes that are dumped into streams and public drainage systems.

These four SSE sectors appear to be significant in half or more of the countries listed inTable 2-2: tanneries (eight countries); textile dyeing, which is also referred to as wet-endtextiles (five countries); electroplating (eight countries); and food processing (six countries).These same four sectors were identified by Kent (1991) as major sources of solid and liquidwaste from SSEs. Consequently, this section places special emphasis on these sectors. Othermajor sectors are covered in less detail in Section 2.3.7. Worksheets A through D in Section 3

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and Appendices A and B contain information on other industrial sectors that are not explicitlycovered here.

2.3 MAJOR SMALL AND MEDIUM-SCALE ENTERPRISE PROFILES

Most manufacturing activities involve multiple unit processes, with more than one wayoften available to complete a particular step in the overall manufacturing process and manyconfigurations possible from start to finish. Consequently, the appropriate specific wastemanagement and treatment options in any industrial category depend on the specific materials,chemicals, and processes used. This section provides some general information on wasteminimization and pretreatment options for the four highly polluting SMSEs identified above.Some concepts on minimization and clean production are given at the beginning of thissection. More detailed information can be obtained from Table B-1 in Appendix B. Likewise,Worksheets A-D in Volume II, and Appendices A and B contain information on otherindustrial sectors that are not explicitly covered here.

Table 2-6. Useful definitions

Useful definitions

Clean production (1) Waste minimization (2) Sustainable development (3)

Continuous application of anintegrated environmentalprevention strategy to processesand products, in order to reducehuman and environmental risks

Process to adopt organizationaland operational measures thatwill reduce to economically andtechnically feasible levels thequantity and hazardousness ofbyproducts generated whichrequire treatment or finaldisposal. This is achievedthrough source reduction andthrough recycling or recovery ofsecondary materials.

This concept seeks the ongoingdevelopment of humankind bypreserving the environment forfuture generations. In thiscontext, industries must absorb the environmental costs of usingcleaner technologies, not only toavoid damaging the environmentbut also because consumerbehavior must be more coherent.

(1) United NationsEnvironmental Program, UNEP

(2) SEMARNAP. Programa parala minimización y manejointegral de residuos industrialesy peligrosos en México 1996-2000. Edition INE, Mexico,1997.

(3) IPES. Instituto de Promociónde la Economía Social. Guíatécnica para el reciclaje deresiduos textiles. Perú. 1997.

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Figure 2-2. Cleaner production according to the United Nations Environmental Program

2.3.1 Cleaner Production and Waste Minimization Opportunities

Changing to clean technology and implementing effective in-plant controls, such asmodified operating practices, good housekeeping, preventive maintenance, and recycling ofbyproducts, represent rational options for SMSEs to reduce pollution and to comply withenvironmental statutes in a cost-effective manner (Hamza, 1991). A World Bank survey of thedifferent industrial sectors in newly industrialized countries revealed the potentially large scopeof waste minimization and resource recovery within industry (World Bank, 1991). This is thecheapest alternative for solving many problems associated with industrial waste disposal andshould be combined with a mandated effort to adopt clean technologies at the time of newproject appraisals. The potential for waste minimization needs to be realized through aconcerted effort involving incentives for water and energy efficiency and water recycling, theexamination of opportunities for waste recycling beyond the individual units generating thewaste, and promotion of process modernization and environmental audits at established plants.To ensure cost- effectiveness, end-of-pipe treatment should only be considered once theopportunities for process modification, waste minimization, and resource recovery have beenthoroughly examined (World Bank, 1991).

In the definition currently used by the U.S. Environmental Protection Agency (EPA),waste minimization consists of source reduction and recycling. This concept of wasteminimization is presented in Figure 2-3. Of the two approaches, source reduction is usuallypreferable to recycling from an environmental perspective. Source reduction and recyclingeach comprise a number of practices and approaches that are illustrated in Figure 2-4. Wasteminimization options are presented below for each of the industries profiled.

Waste minimization

PROCESSESRaw material and energy conservation.

Toxic substances eliminationWaste minimization

PRODUCTOSImpact reduction along product

life cycle

Inventiveness and resourcefulness Technology improvement Attitude change

Risk reduction to humans and theenvironment

SUSTAINABLE DEVELOPMEENT

Clean production

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Figure 2-3. Waste minimization definitions

WASTE MINIMIZATIONThe reduction, to the extent feasible, of hazardous waste that is generated or subsequentlytreated, stored or disposed of. It includes any source reduction or recycling activity undertakenby a generator that results in either (1) the reduction of total volume or quantity of hazardouswaste or (2) the reduction of toxicity of the hazardous waste, or both, so long as such reductionis consistent with the goal of minimizing present and future threats to human health and theenvironment (EPA's Report to Congress, 1986, EPA/530-SW-86-033).

SOURCE REDUCTIONAny activity that reduces or eliminates the generation of hazardous waste at the source, usuallywithin a process (op. cit.).

RECYCLINGA material is "recycled" if it is used, reused, or reclaimed (40 CFR 261.1 (c) (7)). A material isused or reused" if it is either (1) employed as an ingredient (including its use as an intermediate)to make a product; however a material will not satisfy this condition if distinct components ofthe material are recovered as separate and products (as when metals are recovered from metalcontaining secondary materials) or (2) employed in a particular function as an effective substitutefor a commercial product (40 CFR 261.1 (c) (5). A material is "reclaimed" if it is processed torecover a useful product or if it is regenerated. Examples include the recovery of lead valuesfrom spent batteries and the regeneration of sport solvents (40 CFR 261.1 (c) (4).

Waste Minimization

Source Reduction Recycling

First Last

High Low

Order of Exploration

Relative Environmental Desirability

2-18

Figure 2-4. Waste minimization techniques

Waste minimization techniques

Source reductionRecycling

(onsite and offsite)

Control en lafuente

Productchanges

- Productsubstitution- Product conservation- Change in product composition

Use and reuse

- Returnto original process- Raw material substitute foranother process

Reclamation

- Processed forresource recovery

- Processedas a by-product

Input materialchanges Technologychanges Goodoperatingpractices

- Materialpurification- Materialsubstitution

- Processchanges- Equipment, piping, or layout changes- Additionalautomation- Changes in operational settings

- Proceduralmeasures- Loss prevention- Managementpractices- Wastestreamsegregation- Materialhandling improvements

- Production scheduling

2-19

2.3.2 Pretreatment of Wastes at SMSEs

Some industrial wastewater destined to be discharged to a CETP must be pretreated atthe SMSE prior to discharge to remove toxic substances that would adversely affect theoperations of the CETP. Each of the following industrial profiles presents informationregarding onsite waste treatment options for SMSEs. Section 5 discusses pretreatment atSMSEs and pretreatment standards in detail. Also, some SMSEs can implement wasteminimization and recycling measures in general; some specific cases and its economic benefitson the topic can be found at the end of Section 8.

2.3.3 Tanneries

Figure 2-5 shows major process stages during tanning, including (1) rawhide trimmingand salting, (2) beamhouse removing hair/flesh, and hide pickling, (3) chrome tanning, (4)posttanning wetwork, and (5) finishing. Table A-1 in Appendix A identifies additionalreferences on environmental aspects of the tanning industry.

2.3.3.1 Waste Characteristics

Figure 2-5 also shows chemical inputs, liquid effluent, and solid wastes typicallyassociated with each stage of the tanning process. Typically, 1 ton of rawhide yields 200 kg ofleather and requires 50 m3 of water (50,000 L). Wastewater from tanning processes is high insuspended solids and has a high biological oxygen demand (see Table 2-5). Majorcontaminants of concern are chromium and sulfide (see Table 2-5). Kent (1991) cites dataindicating that small firms in Indonesia discharge 65 percent more chromium per ton ofprocessed leather than medium and large firms and suggests two possible explanations: (1)small-scale techniques are less efficient in chrome uptake, resulting in more chrome beingdrained off in wastewaters and (2) small-scale firms are less likely to treat their effluentsbefore discharge. Table A-11 (see Worksheet A in Volume II) contains a more detailed listingof chemicals and contaminants that may be associated with leather tanning.

2.3.3.2 Waste Minimization Options

Table 2-5 identifies a number of waste minimization options for various stages in theleather tanning and finishing process. For chromium, the major toxic inorganic pollutant ofconcern, improving uptake is probably the most feasible option for SMSEs, and using fewerpollutant inputs such as Acacia extracts for leather tanning. Capital costs for chromiumrecovery and recycling and for alternatives to chromium tanning, such as aluminum/titanium-based processes, create a barrier for most SMSEs.

2-20

Figure 2-5. Typical leather tanning and finishing process stages and associated chemicalinputs and wastes (K. Alexander and V. Donohue, 1990, “Cleanertechnologies in the tanning industries”. In: Proceedings of the InternationalConferences on Pollution Prevention: Clean technologies and clean products).(EPA, Washington, DC)

Chemical inputs Process stage Liquid effluent Solid wastes

salt

sulphide/lime

ammonium salts

enzimes

acids, salt

basic chromium sulphateauxiliary chemicals, buffersalts, acid, etc.

retanning agents

dyes, buffer salts

lubricants

Saltedhide

trimmings

Rawhide---------salt

trim ---------

salt solutionssoluble protein (BOD)degraded hairing (COD)sulphide, lime

sludge, lime, protein

fatty fleshingammonium saltsgreasesaline acid

Chrome IIIsalts, acid

sheetings (very thin splits)

chrome shavings

liquors containingspent process chemicals inlow concentrations

leather trimmings

buffing dust(solvent vapour)

leather trimmings

FINISHED SPLITLEATHER

FINISHED GRAINLEATHER

Pickled hide

BEAMHOUSE soak ----------

-------- unhair ---------

remove flesh -------- ----------- delime -------- -------enzime bate------ ------- acid pickle------

TANNING--- Chrome tanning---

sammingsplitting ------shaving ------

wet bluesplit leather

wet bluegrain leather

POST TANNINGWET WORK

------ retannage------ dyeing----- lubrication

dry trim --------stress softening

crust split leather

crustgrain leather

FINISHING

buffing -------surface coating --

trimming -----sorting

Water and solvent-basedpolymers, pigments

susp.solids

2-21

Table 2-7. Leather tanning industry profile

1 ton rawhide ---> 200 kg leatherWaste Characteristics(see also Table A-11 ofWorksheet A in Volume II) Liquid 150 kg/50 m3 TSS

235-250 kg/50 m3 COD100 kg/50 m3 BOD5-6 kg/50 m3 Cr10 kg/50 m3 sulfide

Solid 190-350 kg untanned waste350 kg tanned waste

Waste Minimization Options n Hide chilling to eliminate salt in effluentn Hair recovery processes to reduce effluent BODn Enzyme-assisted dehairing to reduce sulfide usen CO2 deliming to reduce ammonia in the effluentn Reduce chromium in effluent by better uptake/exhaustion or

recovery/n Recyclingn Alternative tanning (aluminum/titanium) to eliminate chromium

in effluentn Water-based and solvent-free top coats to eliminate VOC

emission

Treatment Options Pretreatment: coarse screening

Wastewater:n Activated carbon adsorptionn Sulfide oxidation (beamhouse)n Homogenization (mixing) of beamhouse and tanning effluentn Flocculation/sedimentationn Filtrationn Chromium reduction/precipitationn Biological treatment (oxidation ditches)

Other residuals:n Sludge dewatering and disposaln Fatty fleshings can be used for tallown Chrome shavings to landfill

2.3.3.3 Onsite Treatment Options

Figure 2-6 illustrates major steps in the treatment of wastewater streams from leathertanning operations before discharge to a CETP. Major chemical treatment steps involveoxidation of sulfides in beamhouse effluents and chromium reduction of tanning effluents.Figure 2-5 shows the treatment process for chromium reduction in more detail.

2-22

Figure 2-6. General physical/chemical treatment flow diagram for tannery effluent(Alexander and Donohue, 1990)

2.3.4 Textile Dyeing (Wet-End Processes)

Figure 2-7 shows three major process steps in the dyeing of textiles: (1) pretreatmentwith scouring agents, bleaches, and desizing agents, (2) the dyeing unit, and (3) postdyeinguse of fixatives and rinsing. Table A-1 in Appendix A identifies additional references oncharacteristics of the textile dyeing industry.

Figure 2-7. Example flow diagram for textile dyeing (U.S. EPA, 1988b)

Post tanning andrinaes

Tanning Coarsescreen

Coarsescreen

Sulphideoxidation

Chemicaltreatment Sedimentation

Sludge

Dewater anddisposal

Discharge tosewer

Tannery

Beamhouse Homogenisation

Substrate

Pretreatment

Dyeing unit

Post dyeing

Dyed substrate

Sludge todisposal

Onsite wastewatertreatment

Discharge tostream or potw

Scouring agents

bleaches

desizing agents water

Dyeing aidscarriers water

Fixativeswater

2-23


Textile dyeing produces large amounts of wastewater. Table 2-8 identifies major liquidwaste streams that result from dyeing. Spent pretreatment water typically has a low pH, and,depending on the dyes used, spent process water from dyeing units can contain residual toxicorganic dyes (e.g., azo dyes, heavy metals such as cobalt, copper, and chromium). Spentsolvents and solvent-contaminated wastewater can also be produced from cleaning of wool,production of synthetic textiles, and auxiliary dry-cleaning activities. Table A-11 (seeWorksheet A in Volume II) includes a more detailed listing of chemicals and contaminantsassociated with dyes and the textile industry.


Table 2-8 identifies a number of waste minimization options for textile dyeing. Mostoptions involve either substitution of less toxic dyes and other chemicals/solvents or recoveryand recycling of scouring agents, dyes, and solvents. Relatively high capital costs for recoveryand recycling generally limit this option for SMSEs.


Major treatment requirements for textile dyeing before discharge to a CETP include (1)neutralization and (2) chemical treatment to reduce metals if they exceed the CETP influentstandards.

2.3.5 Electroplating and Other Metals Fabrication

Figure 2-8 shows a sample flow diagram for chromium plating of decorative zinc diecastings. This particular process involves 14 separate cleaning, process bath, and rinse stepsfrom the initial degreasing of the metal parts to the final rinsing and drying of the chromium-plated part. Each facility is unique, so it is necessary to develop a flow diagram for eachparticular operation that details the use and flow of materials and chemicals and the wastesources resulting from the operation of each unit.


Table 2-9 identifies 10 commonly used bath solutions, and Table A-11 (see WorksheetA in Volume II) identifies the chemical composition of the solutions. Water used to rinse themetal parts after immersion in each bath solution contains lower concentrations of the samechemicals. Solid wastes associated with electroplating include filter sludges from plating andchemical conversion as well as sludges from onsite wastewater treatment.

2-24

Table 2-8. Textile dyeing industry profile

Waste Characteristics(see also Table A-11 ofWorksheet A in Volume II)

Liquid n Spent pretreatment water (scouring agents,bleaches, desizing agents)

n Spent process water from batch or continuousdyeing (toxic organic dyes, cobalt, copper,chromium)

n Spent fixative watern Spent solvents and solvent-contaminated

wastewater (wool cleaning, synthetic textiles, anddry-cleaning activities associated with textiledyeing)

Solid n Empty chemical containers

Waste Minimization Options n Substitute less-toxic dyes for toxic coal-tar-based dyesn Use triazine-based fiber reactive dyes to reduce use of more

toxic azo dyes and reduce waste concentrations of dyesduring washing and rinsing

n Substitute other chemicals for use of chromates to oxidizevat dyes

n Reduce or eliminate use of formaldehyde for dyeing anddurable press finishes

n Recover dye process water, replenish spent chemicals, andreuse

n Use hyperfiltration to recover caustic wastewater fromscouring for reuse/recycling

n Recover and recycle dyesn Recover and recycle solventsn Substitute nontoxic cleaners for toxic solvents

Treatment Options n Neutralizationn Biological treatmentn Coagulation/precipitationn Equalizationn Filtrationn Polymeric resin adsorption


Table 2-9 identifies a number of electroplating waste minimization options. Mostoptions focus on bath controls to extend the life of process solutions, dragout reduction toreduce rinsewater contamination, and improved rinsewater design. Many of these options canbe implemented at relatively low cost. Other options, such as substituting nonaqueous metal-coating processes and metals recovery, generally require significant capital investment.

2-25

Figure 2-8. Example flow diagram of chromium plating of decorative zinc die casting(U.S. EPA, 1988a)

ALKALINECLEAN

RINSE NEUTRALIZE ANDPRECIPITATE

ACID DIP

RINSE

CYANIDECOPPER STRIKE

RINSE

CYANIDEOXIDATION

PRECIPITATECOPPER

SETTLE

SLUDGE TREATEDWATER

FILTERSOLIDS

CLEANWATER

ACID DIP

ACID COPPERPLATE

RINSE

NICKEL PLATE

RINSE

CHROMIUMPLATE

RINSE AND DRY PRECIPITATECHROMIUM

REDUCECHROMIUM

PRECIPITATENICKEL AND

COPPER

AIR EMISSIONSAIR EMISSIONS

SPENT SOLVENTS ANDSLUDGE

METAL PIECES

FILTERSOLIDS

AIR EMISSIONS

FILTERSOLIDS

DEGREASING

2-26

Table 2-9 Electroplating industry profile

WasteCharacteristics

Liquid Spent bath solutions (see Table A-11 of Worksheet A in Volume II fortypical composition of different baths):n Brass and bronzen Cadmium cyaniden Cadmium fluoroboraten Copper cyaniden Copper fluoroboraten Acid copper sulfaten Coppern Fluoride-modified copper cyaniden Chromiumn Chromium with fluoride catalyst

Solid n Filter sludges from plating and chemical conversionn Wastewater treatment sludges (metal hydroxides, sulfides, carbonates)

Waste MinimizationOptions

n Substitute nonaqueous metal-coating processes (cladding, diffusion coating, hotdipping, cementation)

n Substitute less toxic process solutions (noncyanide bath solutions are available forcopper and tin electroplating)

n Bath controls to extend life of process solutions (bath filters, using deionizedwater for makeup, keeping racks clean, high quality raw materials in anodes)

n Dragout reduction to reduce contamination of rinsewater by process solution; useevaporation or reverse osmosis to concentrate dragout for reuse in plating bath;see also Table 2-14 for additional ways to reduce dragout

n Improve rinsewater system design to reduce makeup or extend life of rinses (rinsetank design, multiple rinsing tanks, conductivity measurement to controlrinsewater flow, reactive rinsing, fog nozzles and sprays, automatic flowcontrols, rinse bath agitation, use no-rinse coatings); see also Table 2-14 foradditional ways to improve rinse efficiency

n Reuse of contaminated rinsewater (secondary rinse as primary rinse or makeup,countercurrent rinsing, immiscible rinses, treatment of rinsewater for reuse)

n Metals recovery (see treatment options below)

Treatment Options Materials recovery:n Evaporationn Ion exchangen Reverse osmosisn Chromium electrodialysisn Electrolytic recovery/electrowinning

Wastewater treatment:n Metals precipitationn Cyanide oxidationn Neutralization

2-27


The toxicity of electroplating spent bath solutions and rinse wastewater generally meansthat onsite treatment is required before discharge to a CETP. Figure 2-9 shows that therinsewater from the alkaline cleaning and acid dip is mixed and neutralized, and metals areprecipitated. Cyanide in wastewater from the copper cyanide bath must be oxidized and thecopper precipitated out. The acid copper plate bath requires filtration to remove solids andrinsewater, and the nickel plate baths are treated to precipitate nickel and copper. Finally, therinsewater from the chromium plate bath must be treated to reduce, then precipitate,chromium. After precipitation, wastewater is combined to allow solids to settle before beingdischarged. Any residual sludge that cannot feasibly be treated to recover metals goes to anHWTC for further treatment and disposal.

Figure 2-9 shows a more detailed example of a conventional wastewater treatmentsystem for electroplating involving cyanide and chrome baths. Cyanide oxidation and chromereduction take place in separate units, and the resulting solutions are combined with otherrinsewaters as well as acid and alkali waste for mixing before neutralization and precipitation.In this example, a polymer is added to flocculate the precipitate and a clarifier settles the solidsout. The sludge is thickened and filtered, then the filter cake is sent to an HWTC or otherapproved disposal site.

Figure 2-9. Conventional wastewater treatment system for electroplating

2-28

Most metal fabrication activities, in addition to electroplating, produce hazardouswastes. Table A-11 (see Worksheet A in Volume II) identifies specific process and wastecharacteristics for: (1) case hardening, (2) copper, (3) jewelry/metal-plating shops, (3)machine and metalworking shops, (4) metal finishing, (5) metal molding and casting,including foundries, (6) metal polishing, and (7) metal stamping. Appendix A identifiesreferences that address waste recovery and minimization for the following processes associatedwith metalworking: (1) finishes and coatings, (2) degreasing and solvents, (3) metal partscleaning, and (4) metalworking fluids.

2.3.6 Food Processing

Food processing represents a large, diverse industrial sector that is difficult tocharacterize succinctly. Process flow diagrams should be developed for the particularenterprises of interest (see Figures 2-10, 2-11 and 2-12). Table A-1 in Appendix A identifiesadditional references on characteristics of different sectors of the food processing industry.


Table 2-10 identifies major types of wastewater streams that may be associated withfood processing, and Table A-11 (see Worksheet A in Volume II) identifies chemicals thatmay be associated with the following specific food processing categories: (1) beverages, (2)canned and preserved fruits and vegetables, (3) dairy products processing, (4) edible fatprocessing, (5) edible oil processing, (6) grain mills, (7) meat products and rendering, and (8)sugar processing. Generally, toxic wastes are less of a concern with food processing than otherindustries discussed in this chapter, although some processes may produce solvent and heavymetal wastes of concern.


Table 2-10 identifies some general waste minimization options for food processing.


Many food processing waste streams can be discharged to a CETP without any specialpretreatment other than possibly solids reduction. Exceptions are caustic wastewaters thatrequire neutralization and wastewaters contaminated with solvents/heavy metals. Some foodprocessing wastes may have excessively high oxygen demand, in which case they may requiresome form of biological pretreatment.

2-29

Figure 2-10. Hot-dog processing flow diagram

Source: Téllez Villena, José. Tecnología e industrias cárnicas. 1992.

Meat selection

Stages Characteristics

Mince

Cut

Grind

Stuff

Smoke

Cook

Cool

Drain

Preserve

Commercialize

Quality and quantity

Meat and fat separately (3 mm)

Meat + agglut. + ice + salt + preservative +seasoning

All the mix to the colloidal mill

Artificial or natural guts of 17/19 or 22/24 mm

30’ a 60 °C without smoke , 30’ a 66 °C with smoke30’ a 71 °C with smoke, 30’ a 77 °C with smoke

15’ a 74/77 °C

10’ running water

Ambient temperature 5’

Refrigerator (24 hours)

2-30

Figure 2-11. Qualitative operation flow diagram for obtaining canned mussels, mollusks,clams and seafood cocktail in brine

Source: Kanashiro Irakawa, Ana. Estudio de prefactibilidad para la instalación de unaplanta de conservas de mariscos. 1994.

Receipt

Washing

Pre-cooking and bleaching

Extraction, selection and sorting

Washing

Packing

Exhausting

Preservative addition

Sealing

Sterilization

Cooling

Drying and washing

Storage

Labeling

Packing

2-31

Figure 2-12. Operation flow diagram for obtaining juice from citrics

Source: Vidal Añaños, Edelmira. Influencia del método de procesamiento sobrelas características del jugo de naranja (Citrus senensis cv. “Valencia”). 1993.

Washing

Extraction

Sieving

Dexaeration

Sterilization

Packing

Cooling

Storage

2-32

Table 2-10. Food processing industry profile

Waste Characteristics (seealso Table A-11 of WorksheetA in Volume II)

Liquid n High BOD/COD process wastewatern Wastewater from equipment cleaning/disinfectionn Wastewater with spent catalysts (i.e., nickel, nickel

compounds for hydrogenation of vegetable oils)n Spent solvents/wastewaters from extraction/carrier

processesn Pesticides/herbicide-contaminated wastewater

Solid n Plant residuesn Animal product residues (putrescible organic wastes)

Waste Minimization Options n Process changes to reduce BODn Recover and reuse product from waste streamsn Treat and reuse rinse/washwatern Use wastes as animal food

Treatment Options n Neutralizationn Biological treatment

2.3.7 Other SMSE Industry Profiles

Tables 2-8 through 2-13 provide the following information on other significantmanufacturing sectors for SMSEs in newly industrialized countries: (1) waste characteristics,(2) waste minimization options, and (3) treatment options. Individual sectors are discussedbriefly below. Additional information about these industries can be obtained from referencesindexed in Table A-1 in Appendix A and by following the procedures described for WorksheetA in Volume II.

2.3.7.1 Pesticide Formulation

Pesticide formulation, as distinct from pesticide manufacturing, tends to be performedat large plants, be decentralized, and be conducted in agricultural and industrial areas.Consequently, CETPs are less likely to be an option for pesticide formulation than for otherSMSE industries covered in this section. Figure 2-13 identifies types of process wastesassociated with various steps in the formulation of liquid and dry pesticides for application oncrops. Table 2-11 provides additional information, and Table A-1 identifies major referencesthat deal with minimization and treatment of pesticide wastes.

2-33

Figure 2-13. Process wastes associated with pesticide formulation: (a) liquid formulation,(b) dry formulations (U.S. EPA, 1990)

PesticideConcentrate

®¯±

Special PurposeActivities

®±

Solvent Storage

®±

Mixer

¬̄ ±

Filter

¬

Packaging, ContainerTesting & Storage

¬

FinalProduct

Process Waste Categories

¬Waste rinse water

Waste cleaning solvents

®Discarded raw material containersP̄esticide dusts

°Off -specification products

±Evaporated losses of volatile organic compounds

(a) Liquid Pesticide Formulation Process

PesticideCrusher

¬¯

Pulverizer

¬¯

Blender

¬¯

Carrier

High SpeedGrinding Mills

¬¯

AdditivesAdditives

Blender

¬¯

FluidEnergy

Mill

¬¯

Blender

¬¯

Packaging

¯

FinalProduct

Process Waste Categories

¬Waste rinse water

Waste cleaning solvents

®Discarded rawmaterial containersP̄esticide dusts

°Off -specification products

(b) Dry Pesticide Formulation Process

°

°

®®

® ®

2-34

Table 2-11. Pesticide formulation industry profile

Waste Characteristics Liquid n Pesticide- and solvent-contaminated waste rinsewater from equipmentcleaning, area washdown, hot water bath for leak checking

n Pesticide-contaminated laundry wastewater from washing of protectiveclothing

n Pesticide- and solvent-contaminated scrubber water from air pollutionequipment use for unloading of dry pesticides into blending tanks

n Stormwater runoff contaminated by pesticide spillage and fallout ofpesticide dust in open process areas

n Pesticide-contaminated solvents from equipment cleaning (commonlyused solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol,toluene, xylene, chloroform, carbon tetrachloride, benzene, andtetrachloroethylene)

n Waste liquid pesticide formulations from accidental spills (commonlyused solvents in liquid pesticide formulations include MIBK, kerosene,methyl isobutyl ketone, and amyl acetate)

n Waste off-specification pesticide formulations and laboratory analysiswastes

Solid n Waste pesticide formulations from accidental spillsn Waste off-specification pesticide formulationsn Empty chemical containers


n Plant redesign, process modifications (substitute solvents and other raw materials withless toxic materials; reformulate to reduce process waste and cleaning requirements; usesolvent or water used in formulation to clean the preceding equipment before adding tothe mix tank; avoiding off-specification products; blending/using waste stream toproduce marketable products)

n Reduce cleaning frequency (dedicate equipment to single formulation; increase length ofproduction runs; sequential formulations that do not require cleaning between batches)

n Reduce water used for cleaning (wiper blades; well-designed drains; foams or plasticpigs to clean lines; low-volume, high-efficiency cleaning equipment such as steamcleaners and high-pressure spray nozzles)

n Wastewater reuse (final rinse as prerinse for the next cleaning cycle when multiplerinses are used; store rinsewater and use in subsequent formulations; onsite treatmentfor reuse)

n Reduce wastewater from cleanup of spills and area washdowns (dry absorbents;dedicated mops and squeegees; recycled water for initial cleanup; low-volume, high-efficiency cleaning equipment; paving of high spill areas)

Treatment Options Wastewaters:n Granular activated carbonn Biological treatmentn Demulsification/sorption/filtrationn Coagulation/precipitationn Evaporationn Chemical oxidationn Neutralizationn Air/steam stripping

Solids:n Incineration, pyrolysisn Low temperature thermal desorption

2-35

Table 2-12. Commercial printing industry profile

Waste Characteristics(see also Table A-11 ofWorksheet A in Volume II)

Liquid n Spent photoprocessing chemicals (high BOD, silver)n Plate development/cleaning wastes (spent acids, alkalis, solvents, developers, rinsewaters)n Spent fountain solutions (may contain chromium)

Solid Ink/resin sludges

Waste Minimization Options n Good operating practices (proper storage of temperature and light-sensitive chemicals to preventspoilage, first-in/first-out inventory control, etc.)

n See Table 2-13 for image processing minimization optionsn Alternative metal etching or plating processes (presensitized lithography, plastics or photopolymers,

hot metal printing)n Alternative nontoxic developers and finishersn Waste ink recyclingn Reduce rinse wastewater by countercurrent rinsingn Reduce dragout (proper positioning, drain boards, higher temperatures to reduce surface tension, etc.)n Other minimization options related to metal plating and cleaning in Table 2-9 may be applicable

Treatment Options n Neutralizationn See Table 2-13 for treatment options for photoprocessing

Table 2-13. Photoprocessing industry profile

WasteCharacteristics(see also Table A-11of Worksheet A inVolume II)

Liquid n Plant redesign, rehardeners, hardeners, and prebaths (organic chemicals,chromium compounds)

n Developers (organic chemicals)n Stop baths (organic chemicals)n Bleaches (ferricyanide, dichromate/organic chemicals)n Clearing/fixing baths (organic chemicals, silver, thiocyanate, ammonium

compounds, sulfur compounds)n Neutralizers (organic chemicals)n Stabilizers (phosphate)

Solid Sludges with silver (evaporation treatment)


n Good operating practices (proper storage of temperature and light-sensitive chemicals toprevent spoilage, first-in/first-out inventory control, etc.)

n Use floating lids to prevent evaporationn Use squeegees (wiper blades, air, vacuum, wringer sling, rotary buffer) to wipe excess

chemical solutions from film and papern Substitute nonsilver containing photographic materials (diazo, vesicular, photopolymer,

electrostatic films)n Extend life of fixing baths (addition of sodium thiosulfate, acid stop bath, addition of acetic

acid to fixing bath as needed to keep pH low)n Color developer regeneration (ion-exchange, electrolytic, persulfate, ozone regeneration,

precipitation)n Rinsewater recycling

Treatment Options n Neutralizationn Activated carbon adsorptionn Coagulation/precipitationn Filtrationn Ion exchangen Silver recovery (metallic replacement, electrolytic recovery, chemical precipitation)n Evaporationn Steam strippingn Cyanide oxidationn Chromium reduction

2-36

Table 2-14. Pharmaceuticals manufacturing industry profile

Waste Characteristics(see also Table A-11 ofWorksheet A in VolumeII)

Liquid n Plant redesign, waste rinsewater from equipment cleaning and extractionresidues

n Scrubber water from air pollution equipment used for dust- or hazardous-waste-generating processes

n Spent aqueous solutions from solvent extraction processesn Spent fermentation broth (high oxygen demand, suspended solids)n Process liquors from organic synthesis (solvents, oxygen demand, suspended

solids, high/low pH)n Spent solventsn Accidental spillsn Off-specification or outdated products from manufacturing operations

Solid Sludges


Process Modifications:n Reduce organic solvent use (water-based solvents for tablet-coating, aqueous-based

cleaning solutions)n Use solvent or water used in formulation to clean the preceding equipment before

adding to the mix tankn Avoid off-specification productsn Blend/use waste streams to produce marketable productsn Mix acid and alkaline waste solutions to reduce requirements for neutralization

reagents

Reduce Equipment Cleaning Wastes:n Use sequential formulations that do not require cleaning between batchesn Dedicate equipment to formulationsn Reduce clingage and residue to be cleaned between batches (manual use of wiper

blades, squeegees, mops; mechanical wipers in mix tanks; rework remainder intoproducts; clean lines using foam/plastic pigs; self-draining pipe design)

n Use low-volume, high-efficiency cleaning (new nozzle heads or higher pump pressureson existing hoses; high-pressure spray washers; steam cleaners)

n Collect and reuse rinsewater and cleaning wastes (final rinse as prerinse of nextcleaning cycle, reuse for primary cleaning, reuse as part of compatible formulation)

n Treat cleaning wastes for reuse (regenerate/recover solvents by distillation)

Improve Cleaning Procedures for Spills and Area Washdowns:n Dedicated vacuum system (powders)n Use dry cleanup methods (dry absorbents)n Closing floor drains to encourage dry cleanup methods and discourage excessive water

usen Dedicate mops and squeegees to reduce water hosing for floor washingn Use recycled water for initial cleanupn Use high-pressure water knife spray nozzles on hose to reduce water used for floor

washingn Pave areas where spills frequently occurn Recover and use spilled materials

Treatment Options n Neutralizationn Sedimentationn Biological treatmentn Incineration/pyrolysis

2-37

Table 2-15. Printed Circuit Board Manufacturing Industry Profile

Waste Characteristics(see also Table A-11 ofWorksheet A in VolumeII)

Liquid Process liquid wastes (see Table A-11 of Worksheet A in Volume II forcomposition):n Cleaning/surface preparationn Catalyst application/electroless plating wastewatersn Pattern printing/maskingn Electroplatingn Etching

Solid Airborne particulates (board/sanding materials)


Cleaning/Surface Preparation:n Use mechanical cleaning methods (abrasive blast cleaning) instead of solvent-based

methodsn Regenerate spent acid baths for reuse (ion exchange)

Pattern Printing and Masking:n Reduce use of toxic developers and solvents (aqueous processible resist; screen-

printing instead of photolithography)n Recycle and reuse spent photoresist stripper by decanting and filtering solution into a

clean tank

Reduce Drag-Out From Plating and Process Baths:n Minimize bath chemical concentration to reduce chemicals in dragout and viscosityn Increase bath operating temperature to lower viscosity and surface tension of process

solutionn Use wetting agents to reduce surface tension of process solutionn Position workpiece properly on plating rackn Withdraw boards slowly and allow for ample drainagen Use drain boardsn Use still or dead rinses

Improve Rinsing Efficiency:n Use closed circuit or countercurrent rinsingn Use spray rinsing and fog nozzlesn Proper equipment design and operationn Use conductivity probe or pH meter to control fresh water through rinse systemn Use deionized water to improve rinse efficiency and reduce sludge volume in

wastewater treatment systems

Etching:n Reduce thickness of copper foil claddingn Use pattern plating instead of panel platingn Eliminate need for copper etching by using the additive method rather than subtractive

methodn Use nonchrome etchants such as ferric chloride or ammonium sulfide to reduce waste

toxicityn Recycle spent etchants

Treatment Options See also electroplating treatment options (Table 2-9)n Activated carbon adsorptionn Coagulation/precipitationn Filtration

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2.3.7.2 Commercial Printing and Photoprocessing

Tables 2-10 and 2-11 profile waste characterization, minimization, and treatmentoptions for the commercial printing and photoprocessing industries. Mubvami (1991) notesthat in Zimbabwe photographic chemicals are reused to the point where they are very weakwhen they are finally discharged down the drain because replacing chemicals at therecommended intervals is very costly.

2.3.7.3 Pharmaceuticals Manufacturing

Table 2-14 profiles waste characterization, minimization, and treatment options forpharmaceuticals manufacturing. In India, approximately 9,000 SMSEs, representing 97percent of the total number of enterprises, are engaged in the manufacture of pharmaceuticals.The information in Table 2-14 applies mainly to large-scale manufacturing enterprises and maynot be fully relevant to SMSEs.

2.3.7.4 Electronics Manufacturing

Table 2-15 profiles waste characterization, minimization, and treatment options forprinted circuit board manufacturing. Circuit board manufacturing combines processes from theelectroplating, printing, and photographic industries.

2.4 REFERENCES

Alexander, K., and V. Donohue. 1990. Cleaner Technologies in the Tanning Industries. In: Proceedings of the International Conference on Pollution Prevention: Clean Technologies andClean Products. EPA/600/9-90/039. Washington, DC.

Batstone, R., J.E. Smith, Jr., and D. Wilson, eds. 1989. The Safe Disposal of HazardousWaste: the Special Needs and Problems of Developing Countries. World Bank Technical PaperNumber 93, 3 v.

Benavides, L. 1992. Hazardous Waste Management for Small-Scale and Cottage Industries inDeveloping Countries: Overview. Expert Group Meeting on Management of Hazardous Wastesfrom Small-Scale and Cottage Industries. Nairobi: HABITAT, Urban ManagementProgramme.

Hamza, A. 1991. Impacts of Industrial and Small-Scale Manufacturing Wastes on UrbanEnvironment in Developing Countries. United Nations Center for Human Settlements, UrbanManagement Programme (May).

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Interamerican Development Bank. 1997. Guía para la aplicación de procedimientosambientales en operaciones de crédito para microempresas. Washington, DC; IDBKent, L. 1991. The Relationship Between Small Enterprises and Environmental Degradation inthe Developing World (With Emphasis on Asia). DAI, Bethesda, MD. Prepared for U.S. AID.

Mubvami, T. 1991. Hazardous Waste Management for Small-Scale Manufacturing andCottage Industries in Urban Areas of Zimbabwe. Prepared for UMP/UNCHS, Nairobi.

United Nations Environment Program (UNEP). 1987. Industry and Environment (June).

Urban Management Programme (UMP). 1992. Draft Final Report of Expert Group Meeting onLocal Management of Hazardous Wastes From Small-Scale and Cottage Industries. (November23). [Meeting was held in Metepec and Leon, Mexico; organized by UMP(UNDP/UNCHS/World Bank) and cosponsored by UNEP, WHO, and ECO/PAHO]. Editedby Carl Bartone.

World Bank. 1991. Industrial Pollution Control Projects, India: Feasibility Assessment ofCommon Treatment Facilities in Gujarat, Maharastra, and Tamil Nadu, India. Prepared forthe World Bank by Chemcontrol A/S, Denmark (March).

World Bank. 1994. Staff Appraisal Report: India, Industrial Pollution Prevention Project.World Bank, Country Operations, Industry and Finance Division, Washington, DC (June).

World Health Organization (WHO). 1985. Environmental Pollution Control in Relation toDevelopment. WHO Tech. Rep. Ser. 718.

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