WASTE ABATEMENT AND MANAGEMENT IN NATURAL RUBBER PROCESSING SECTOR pptx

Dry rubber refers to the grades, which are marketed in the dry form such as rubber sheet, crepe rubber, and crumb rubber, whereas liquid rubber refers to the latex concentrate production

WASTE ABATEMENT AND MANAGEMENT

IN NATURAL RUBBER PROCESSING SECTOR

ED 78.20 Industrial Waste Abatement and Management

Prepared by Group 3:

HOANG NGOC TUONG VAN DANG THI THUY DUONG NGUYEN THI MAI THANH THACH HUYNH THI THU TRANG IMASTINI DINURIAH

SUBARNA SHARMIN HUYNH MINH KHAI TRAN NGUYEN QUANG HUY

ASIAN INSTITUTE OF TECHNOLOGY

SCHOOL OF ENVIRONMENT, RESOURCES AND DEVELOPMENT

April 2007

1 INTRODUCTION

Natural rubber (NR) processing sector is an industry which produces raw materials used for the manufacture of rubber industrial products (conveyor belts, rubber rollers, etc.), automotive products (fan belts, radiator hoses, etc.), latex products (rubber gloves, toys hygienic products, etc.) and many kinds of adhesives (see Figure 1.) The major users of natural rubber are tire and footwear industries

Crumb Rubber

rubber gloves, toys hygienic

products

Skim Latex Latex Concentrate

Figure 1 Flow diagram of typical Natural Rubber (NR) processing and manufacturing

The raw material used for natural rubber processing is latex mainly tapped from rubber tree

(Hevea brasiliensis) Historically, natural rubber has been used since pre-columbian

period by ancient people in Mexico, Peru, and the Amazon Basin but its processing industries were firstly developed in Brazil in 1870 However, due to the lack of labor sources and limited land for rubber tree plantations in Brazil, the industries move to Asian countries where land and labor sources are abundant Therefore, it is reasonable that nowadays Asia is the main source of natural rubber in the world, which account for around 94% of output in 2005 and the three largest natural rubber producing countries i.e Indonesia, Malaysia and Thailand account for around 72% of all natural rubber production (http://en.wikipedia.org/wiki/Natural rubber, 2007) Natural rubber factories are always located around the plantation area, and they could be categorized from small scale to large scale industries depending upon the size of rubber tree plantation

As the demand of rubber products is increasing time to time, the existence and development of natural rubber processing sectors become significantly important Data

from International Rubber Study Group in http://www.lgm.gov.my/nrstat/nrstatframe.html

showed that global natural rubber production increased from 6,440 metric tons in 1996 to 8,821 metric tons in 2005, whereas its consumption increased from 6,110 metric tons in

1996 to 9,000 metric tons in 2005 (see Annex 1, Table 1.) It is estimated that world net exports in 2010 are projected to grow by 1.3 percent annually to reach 5.5 million tons, 15 percent above the average of 1998-2000, with the bulk of the increase from Indonesia, Vietnam and some smaller Asian countries (www.fao.org., 2007)

Raw material products from natural rubber processing sector provide huge benefits to human beings as they are exploited to manufacture many kinds of important rubber goods However, environmental damages generated from this sector could become big issues Natural rubber processing sector consumes large volumes of water and energy and uses large amount of chemicals as well as other utilities It also discharges massive amounts of

wastes and effluents The most common environmental issues are wastewater containing chemicals and smell, hazardous waste, noise, and thermal emission In order to reduce the damage in the environment, waste abatement and management in natural rubber processing sector should be handled properly

This paper is presented to discuss in detail about natural rubber processing sector in terms

of its processing operations, major environmental issues generated from the sector and its sources as well as its characteristics In addition, waste treatment practices and identification of CP potential in this sector are conferred One case study referring to Xuan Lap natural rubber processing in Vietnam is also discussed

2 NATURAL RUBBER PRODUCTION PROCESSESS

The raw material used for the production of natural rubber is “white milky fluid” called latex taken from the latex vessels of rubber trees, which can be categorized as field latex, scrap, soil lump, and bowl lump Chemically, latex consists of rubber, resins, proteins, ash, sugar, and water Verhaar (1973) mentioned that rubber content in the latex comes from the trees is approximately 30 to 40% Latex, which is a kind of biotic liquids, will be deteriorated if it is not preserved by ammonia or sodium sulfite which is called anticoagulant Anticoagulants prevent latex from pre-coagulation The kind of anticoagulant used is depended upon the production process Sodium sulfite is preferred if crepe or sheet rubbers are to be made, but ammonia is more suitable for latex concentrate

In summary, the product of natural rubber can be broadly classified under two categories i.e dry and liquid rubber Dry rubber refers to the grades, which are marketed in the dry form such as rubber sheet, crepe rubber, and crumb rubber, whereas liquid rubber refers to the latex concentrate production in which the field latex is separated into latex concentrate containing about 60% dry rubber and skim latex with 4-6% of dry content Skim latex is produced as a byproduct during the preparation of latex concentrate It has a dry rubber content of only 3 to 7% and its dirt content is very low Coagulation of skim latex can be either spontaneously or by acid treatment It is important that the ammonia content is kept

as low as possible Further processing is the same as for smoked sheet The processing of miscellaneous latex also exists in some factories (see Annex 6, Figure 6.)

Referring to the whole steps in natural rubber processing, it is obvious that both dry and wet processes are involved Size reduction, digestion, washing, and drying are unit operations involved in these processing activities The step of washing consumes large amount of water, so that wastewater generated from these processing operations mainly

comes from this step Brief descriptions of processing of each type of natural rubber are

presented below

2.1 Processing of rubber sheet

Rubber sheet could be categorized as Air Dried Sheet (ADS) and Ribbed Smoked Sheet (RSS) The main difference of ADS and RSS is on the method used for drying the sheet,

in which ADS exploits air, whereas RSS uses smoke provided in a smokehouse with the temperature up to 60°C The original type of smokehouses has been replaced by so-called

“Subur” smokehouses The principle of the design of these houses is to eliminate as much

as possible manhandling of sheets The smoking chambers are on ground level, so that trolleys can be loaded with sheets in the factory and then transported by rail into the smoke chambers The smoking process in the “Subur” smokehouses is basically a continuous process

Rubber sheet processing is started from latex collection in the field It is then diluted and screened before the addition of formic acid for coagulation process The wet sheet is

sheeted off to a thickness of about 3 mm and finally passes an embossed two roll mill The sheets are dried whether by air or in a smokehouse for about one week at temperatures The specific smell of the smoked sheets is caused by the wood and other organic materials such as coconut shells used to produce the smoke The sheets produced are finally classified and packaged The flow diagram of rubber sheet processing is presented in the Annex 2, Figure 2

2.2 Processing of Crepe rubber

Crepe rubber is made from latex field coagulum In the production of crepe rubber from latex, the raw material is prevented from coagulation by adding ammonia After transported to the factory, latex is filtered through a screen to remove coagulated rubber, particles, or leaves It is then transferred to mixing tank with stirring blade after determine dry rubber content (DRC), latex is diluted with water to reduce DRC to 20 – 22%

In the production of crepe rubber, there are three important steps Diluted latex from mixing tank is transferred to stationary coagulation troughs through movable throughs Acetic or formic acid solution (2%) is normally used to neutralize ammonia added in the field for coagulation prevention and to reduce pH to 5.0 – 5.2, near the isoelectric point of 4.3 The second step is primary and secondary milling After coagulation, water is added to coagulation troughs to float up the coagulum In water, coagulum is easy to move to milling machine After primary milling, slabs of coagulum is passed through pair of roller

of which the final one is grooved so as imprint on each the rib to increase the surface area for drying Each roller is equipped with water sprayers to wash away non rubber particles Then coagulum is cut into small, then it is dried by hot air and pressed The flow diagram

of crepe rubber processing is presented in the Annex 3., Figure 3

2.3 Processing of crumb rubber

This type of natural rubber product is relatively new, which in trade market it is known as

“technical specification rubber” (Setyamidjaja, 1993) There are some benefits of crumb rubber processing i.e the process is faster, the product is more clean and uniform, and the appearance of product is more interesting Raw materials used for making crumb rubber can be field latex or low quality lump The steps included in crepe rubber processing using field latex are latex coagulation, milling, drying, bale pressing, and packing Coagulation process uses 1% formic acid plus 0.36% melase Sodium bisulfate is usually added to the coagulation mixture to get brighter end-product If the raw material used is lump, the step will be started by soaking and/or washing the lump, and then followed by hammer milling,

crepe formation, milling, drying, bale pressing, and packing The flow diagram of crumb rubber processing is presented in the Annex 4., Figure 4

2.4 Processing of latex concentrate

Latex colleted from the field is pre-treated such as screen, wash and ammonia addition before processing After processing, the field latex is centrifuged Because the disperse phase (rubber) and the continuous phase (water mainly) differ in density, the concentrated latex (60%) rubber is separate and is collected from the center of centrifuge bowl, whereas skim, about 5% rubber, is taken from the outer edge of centrifuge bowl The concentrate latex is bulked, ammoniated and then stored The skim latex is deammoniated, coagulated with acid, creped and dried The flow diagram of rubber sheet processing is presented in the Annex 5., Figure 5

3 ENVIRONMENTAL ISSUES OF NATURAL RUBBER

PROCESSING SECTOR

Despite the numerous benefits that are rendered to the modernization of this world by natural rubber, the consequence of natural rubber processing has yet provide a serious problem due to its highly polluted effluents The rapid growth of this industry generates large quantities of effluents coming from its processing operations which is really a big problem because of its wastewater contains high biological oxygen demand and ammonia Without proper treatment, discharge of wastewater from rubber processing industry to the environment may cause serious and long lasting consequences

3.1 Major environmental problems

3.3.1 High concentration of BOD, COD, & SS

Wastewater discharged from latex rubber processing usually contains high level of BOD, COD and SS (see Table 2) These characteristics vary from country to country due to difference in raw latex and applied technique in the process The main source of the pollutants is the coagulation serum, field latex coagulation, and skim latex coagulation These compounds are readily biodegradable and this will result in high oxygen consumption upon discharge of wastewater in receiving surface water

Table 2 Typical characteristics of wastewater from rubber processing

34,900 3,645

58,752 5,873

14,142 1,962

28,307 13,597

Note: All Parameters are expressed in mg/I, except pH

Source: India Central Pollution Control Board, 2001

3.3.2 Acidic effluent

It is noted by Pandey et al (1990) that the effluent from latex rubber processing industries

is basically acidic in nature Different extents of acid usage in the different factories attribute to pH variation of different effluent Due to the use of acid in latex coagulation,

the effluent discharged from latex rubber factories is acidic and re-dissolves the rubber

protein The effluent comprises mainly of carbonaceous organic materials, nitrogen and sulfate The quantity of acid used for coagulation of the latex, specifically in skim latex after centrifugation operation, is generally found to be higher than the actual requirement

3.3.3 High concentration of ammonia and nitrogen compounds

The high concentration of ammonia presents in the latex concentrate effluent posed another serious threat to the environment Most of the concentrated latex factories in the South of Thailand discharge treated wastewater that contains high level of nitrogen & ammonia to a nearby river or canals leading to a water pollution problem If high level of ammonia is discharged to water bodies, it could lead to death of some aquatic organisms living in the

water Land treatment system has been conducted to treat and utilize nitrogen in treated wastewater from the concentrated latex factory

3.3.4 High level of sulfate

The effluent from latex concentrate factories contains high level of sulfate which originated from sulfuric acid used in the coagulation of skim latex The high level of sulfate in this process can cause problem in the biological anaerobic treatment system as high levels of H2S will be liberated to the environment and generates malodor problem The free H2S also

inhibits the digestion process, which gives lower organic removal efficiency (Yeoh et al.,

1993)

3.3.5 High level of odor

The odor causing compound such as hydrogen sulfide, ammonia, amines, can be produced

by many of wastewater treatment process Most odor of organic nature arises from the anaerobic decomposition of compounds containing nitrogen and sulfur (Dague, 1972; Henry, 1980) The odor is detectable even at extremely low concentrations and makes water unpalatable for several hundred miles downstream from the rubber plants The problems presents varies considerably depending on the plant site, the raw material used, and the number of intermediary product Most rubber factories in Songkhla province have been forced to use activated sludge process or aerated lagoon to prevent the bad smell from the anaerobic condition

Table 3 Gaseous concentration emission from latex processing

(mg/m 3 )

H 2 S (mg/m 3 )

3.3.6 Favorite condition for pathogenic bacteria

A large population of bacteria also presents in the effluent discharged from the factories

The type of bacteria found in rubber effluent are coliform, Streptococci and E.Coli Most

of constituents of the effluent can act as substrate for the growth of these microorganisms (Baskaran, 1980)

Source: Vietnam Rubber Company, 2004

3.3 Wastewater pollution load (kg/ton)

Table 5 Wastewater pollution load

Parameter Latex

concentrate

Skim latex

Miscellaneous latex

Crumb rubber

Pale latex

Estate brown latex

4 WASTE TREATMENT PRACTICES

The waste treatment practices may change accordingly to the characteristics of effluent discharges and allowable limitations Waste treatment practices include practices for wastewater treatment, air pollution control and solid management Of all environmental issues generated from this industry, wastewater is the major problem with a wide range of effects on human health and environmental health Air pollution and solid management are not major problems hence in this paper we mainly focus on wastewater treatment practices

4.1 Wastewater treatment practices

Wastewater collected from rubber processing factory contains a variety of substances as well as the commercially important constituent, in this case rubber hydrocarbon It contains proteins, minerals, non-rubber hydrocarbons and carbohydrates This wastewater has high concentration of ammonia, BOD5, COD, Nitrate, Phosphorus as well as total solids Moreover, the wastewater from latex concentrate and skim crepe industry contains sulfate which comes from sulfuric acid in the skimming process and in some processes produce rather high content of zinc and cadmium Wastewater treatment practices can be mentioned

as pollution abatement Pollution abatement involves (a) in-plant control of waste and (b)

end-process treatment of wastewater Some in-plant control measures can be introduced to enable reduction in consumption of water, generation of pollutants and to increase the efficiency of the end-of-process wastewater treatment

4.1.1 In-plant control measures

In the crepe and crumb rubber units, in which field coagulum is processed, high required water quantity is generally used for soaking and also the soaking time allowed is not adequate If the raw scrap rubber is properly soaked and primary dirt removal is done by scrap-washer, the quantity of water consumed in milling can be reduced

In the crumb units, wastewater from final milling can be collected separately from the effluent of the other milling section and can be used either for soaking the scrap rubber or for the first milling process This is comparatively clean and the amount of reduction can

be up to 25% of the total water consumption

In centrifuge machine bowl, washing is done at the interval of 3-4 hours to remove the sludge About 0.5% rubber is lost during this washing step To reduce loss, washing step can be done at two stages The first washing which is more concentrated may be segregated and collected in a separate tank and coagulated for recovery of the rubber lost during washing This will result in reduction of pollution load in the effluent The possibility of diverting this waste stream into the skim coagulation tank can also be considered

The quantity of acid used for coagulation of the latex, especially skim latex kit after centrifugation stage is generally found to be higher than the actual requirement The time needed in coagulation tank is also less The incomplete coagulation results in the loss of rubber particles into the effluent along with the skim serum The excess acid not only causes acidic effluent but also re-dissolves the rubber protein and causes delay in coagulation Hence, it is suggested that proper acid concentration applied and sufficient coagulation time should be provided to obtain more or less clear liquid after complete coagulation The skim latex if de-ammoniated before coagulation, acid requirement can be reduced and the ammonia concentration in effluent may also be reduced In the latex process units the segregated first washing of the coagulum may be diverted to the skim coagulum tank where after skim coagulum recovery, the effluent may join the other wastewater streams

4.1.2 End of process treatment

Basically wastewater treatment can be divided into pretreatment, primary treatment, secondary treatment, and tertiary treatment

Pretreatment

The rubber trap used for arresting suspended matters should have holding capacity of at least 12 hours with proper baffles to induce continuous up and down flow pattern If designed properly, this can reduce suspended solids by 40 to 60% The equalization tank should have at least one day detention time It is preferred to have two equalization tanks, each of them with one day detention time

Primary treatment

For a latex processing unit, effluent from the equalization tank to be sent for neutralization and chemical treatment by alum and iron salt (about 200 mg/l) Combined wastewater of latex process units also needs neutralization by using of lime and settling of suspended solids by using of coagulants The settler/clarifier should have adequate detention time for removal of suspended solids The sludge may be taken to sludge drying beds for dewatering The dewatering of sludge produced by primary clarifier is normally carried out

on belt or vacuum filters which raises the sludge consistency from 20 to 40%

Secondary treatment

Following the primary treatment, the effluent should be subjected to the biological treatment If sufficient land area is not available, then the effluent after primary settling may be subjected to an extended aeration activated sludge type biological treatment process

Before going for biological treatment, it must be ensured that:

(a) All the in-plant control measures are adopted,

(b) Primary treatment e.g rubber trap equalization neutralization and clarification steps are incorporated

The above measures will reduce substantial quantity of pollutants particularly BOD and suspended solids The primary treated effluent can be treated in a secondary/biological treatment unit It is envisaged to render secondary treatment by adoption of extended aeration activated sludge process The biological treated effluents should be settled in a secondary settling tank

If there is no constraint of land, the biological treatment could be anaerobic followed by aerobic pond system with the proper dimensions, holding capacity and adequate detention time (10 to 15 days) for anaerobic pond followed by 5 to 10 days for aerobic ponding system The type of soil and proximity to the wastewater and ground water table condition should be taken into consideration before going for these treatment systems Protective lining is recommended to eliminate any risk

In place of the anaerobic-aerobic system, an oxidation ditch of detention time of 2-3 days can also be considered as an alternative for treating the effluents of the crumb rubber unit Depending on the real conditions of countries and specific processes, some units of wastewater treatment are modified and adjusted to have better efficiency For example, most of the latex concentrate factories in the South of Thailand discharge treated wastewater that contains high level of nitrogen to a nearby river or canals leading to a water pollution problem Land treatment system is used to treat and utilize nitrogen in treated wastewater from the concentrated latex factory The land treatment system resulted high removal efficiency for nitrogen (Rungruang, 1998)

In recent years, many studies were carried out to treat wastewater from this industry by biological methods such as ASP (activated sludge process) and use of oxygenic phototrophic bacteria for treating latex rubber sheet wastewater (Thongnuekhang and Puetpaiboon, 2004) These studies aim at improving the efficient treatment of wastewater from this industry and contribute to partially reduce the emission of toxic gases into the environment

Tertiary treatment

The remaining components after primary and secondary treatment are residual SS, residual BOD, odor and hydrocarbon Tertiary treatment designed to remove these components are generally carbon adsorption, massive lime treatment and foam separation, mainly for treatment of Residual Refractory Organics The flow diagram of treatment system adopted presently given in Annex 8., Figure 7

4.2 Air pollution control

In production process, a mixture of poisonous gases is generated from coagulation of rubber and latex It should be controlled and reduced by activated carbon treatment Chimney gases should be controlled technically, otherwise it might affect the growth of agricultural plants in the fields

Besides, foul smell due to wastewater drainage is a problem and it is difficult to control It can be reduced by applying in-plant measures or cleaner production such as reducing the amount of wastewater generated from the process and separating wastewater from the latex immediately when discharged Most rubber factories in Songkhla province, Thailand have

been forced to use activated sludge process or aerated lagoon to prevent the bad smell from the anaerobic condition

Air pollution control is related to wastewater treatment methods Hence, air pollution

control can be obtained by controlling and treating wastewater from production process

5 IDENTIFICATION OF CP POTENTIAL IN NATURAL LATEX

RUBBER PROCESSING

A closed look reveals that rubber industry consumes large volumes of water, uses a lot of chemicals and other utilities and discharges enormous amounts of wastes and effluents The few cleaner production assessments and implementation programs carried out in many countries has shown tremendous benefits Some of them are lesser usage of chemicals, efficiency in energy and utilities including water, improvement in productivity and profitability, lesser loads and volumes of effluent discharged to the neighborhood, better image and relationship with employees internally and with the neighborhood externally

Rubber Tapping and Transportation

Usage of traditional coconut shell as the cup for latex collection gives a large cup lump increasing the scrap crepe This should be replaced by a plastic bowl and the traditional galvanized iron bucket is replaced by plastic buckets

The addition of chemicals to the field latex is still a problem and training of tapers and other personnel seems to be the main option available The transportation of the field latex

by mild steel bowlers adds rust to latex A coating of epoxy is very effective to eliminate rust contamination of latex

Coagulation

A simple partitioning of the coagulation tank using wooden planks will be very effective instead of cutting the coagulum to size by a knife as in tradition This saves labor involved and the blocks are of uniform size, which produces uniform edged laces at milling

Skim Coagulation

In centrifugation unit, the scrum water contains about 1% rubber which is usually coagulated using sulfuric acid The addition of ammonia in the field as well as in the factory prior to centrifugation results in high usage of acid for skimming and causes many problems in final treatment of effluent To get the most effective latex formulation and chemical dosing at field and in the factory through controlled trials is the most appropriate solution to the problem which is complicated and time consuming The long-term benefits

of this solution are very attractive Before skim coagulation, the de-ammoniation of effluent helps to reduce usage of sulfuric acid

In all latex concentrate factories the scrum water from latex, centrifuge wash water and bowler wash water is discharged as one stream The segregation of these streams can help

to reduce final treatment cost and possibility of recycling of the wash water with a little treatment for selected uses

Energy Consumption

The uniform edged laces reduced the milling needs and blankets and bundles formed took lesser time In the dryer tower the internal partitioning and systematic passing of hot air from chamber to chamber improved the drying efficiency

Scrum Water

The serum water has many nutrients and other substances, which can be of high commercial value Trials are being conducted to use serum water as a liquid fertilizer

6 CASE STUDY: XUAN LAP NATURAL RUBBER PROCESSING, VIETNAM

A natural rubber processing factory (Xuan Lap factory) has the following parameters:

6.1 Cost and Investment (See Table 6.)

Table 6 Cost and investment of Xuan Lap natural rubber factory

Investment cost

Cost for installing others includes

environment protection equipments

ventilation, ear cap, muffler, etc

Compensation cost (if any) for land

clearance

Operation cost of wastewater treatment

plant (should be more specific in cost

59,008

16,956 27,236 13,277 1,539

The factory operates three main processes i.e concentrated latex, skim latex, and miscellaneous latex

6.2 Environmental issues related to the operation of the factory

1 Air pollution: mainly is H2S arises from raw latex, NH3 from the process However, they can be considered as minor problems

2 Solid waste (See Table 7.)

Table 7 Solid waste from natural rubber processing

Type of solid

waste

Latex concentrate process

Skim latex process

Miscellaneous latex process

3 Wastewater (see Table 8)

Table 8 Characteristic of wastewater from individual process

Parameters Unit Concentrated

process

Skim latex process

Miscellaneous process

-Characteristics of combined waste water are as follow (see Table 9):

Table 9 Characteristics of combined wastewater

6.3 Opportunity for Waste segregation

The effluent from all processes have similar constituent i.e high BOD and COD load, high

SS concentration which is contributed from uncoagulated latex; high concentration of

Nitrogen, and basically in acidic condition

Especially, the liquor discharged directly from the process has very high concentration, i.e

5,000 – 6,000 mg/l of BOD and 9,500 – 12,000 mg/l of COD for centrifuge process This

effluent is difficult to be treated directly, so they should be diluted by combining with other

process effluents e.g miscellaneous process and rinse/washout water that has lower

loading before transported to the treatment plant

However, wastewater from miscellaneous and general washout usually contains certain

amount of sand and grit, so that they should be separated for grit removal before

combining with wastewater from other process If not, the grit removed from the treatment

plant would contain high amount of latex and serum and that would lead to unpleasant

odor when dumping it due to high degradable of latex and serum

6.4 Wastewater treatment layout

The lay out of wastewater treatment plant is proposed as described in Annex 8, Figure 7

based on the following criteria:

- Characteristic of the effluent

- Available resources for wastewater treatment plant (land area available, cost)

- Terrain, location and reception source

- Operation regulation

The Major O&M issues related to wastewater treatment plants could be:

- High level of odor from NH3 and H2S

- Acidic condition leads to corrosion in the equipment

- The factory is only operated during a certain season in a year, i.e about 7 months/year

This will lead the problem in frequently start up the treatment system and effect the

treatment efficiency

6.5 Material Balance

Although the factory is operated three processes, this case study only focus on the latex

concentrate processing to carry out the material balance in order to assess process

performance and to find out potential for improvement

Step 1: Determining Inputs

Amount of consumption Item of chemical

Di-Ammonium Hydrogen

Phosphate (NH4)2HPO4 2.3

Di-Ammonium Hydrogen Phosphate (NH4)2HPO4

Step 2: Recording water usage

Unit operation m 3 /ton of field latex m 3 /day

Step 3: Quantifying process outputs

Unit operation Wastewater By-product/

Waste reused

Atmospheric Solid waste

tree skin, etc…

containing latex

Centrifugation Process water

Rinse water

Packaging Spilled centrifuged

latex

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