How does rubber impact the environment?
The growing market for rubber is a major, but largely overlooked, cause of tropical deforestation, new analysis shows. Most of the rubber goes to produce tires, more than 2 billion a year, and experts warn the transition to electric vehicles could accelerate rubber use.
The elephants are gone. The trees are logged out. The Beng Per Wildlife Sanctuary in central Cambodia is largely destroyed, after being handed over by the government to a politically well-connected local plantation company to grow rubber.
In West Africa, the Luxembourg-based plantations giant Socfin has been accused in recent weeks of deforestation and displacing Indigenous people around its rubber plantations in Nigeria and Ghana.
Meanwhile, on the heavily deforested Indonesian island of Sumatra, tire multinational Michelin and a local forestry company raised $95 million worth of green investment bonds on the promise that they would reforest bare land with rubber trees. But the NGO Mighty Earth has found that much of the plantation went ahead on land from which natural forest had been removed as recently as a few months before by a subsidiary of the local company.
These are just three examples among hundreds of one of the biggest, but least discussed, causes of tropical deforestation. The spread of rubber plantations is driven primarily by our demand for more than 2 billion new tires each year. The full devastating impact of this has been exposed by a new analysis of high-resolution satellite images that can, for the first time, distinguish rubber plantations from natural forests.
Rubber as a crop is a worse deforester than coffee or cocoa and is now closing in on palm oil for the top spot.
But even as the true environmental cost of the ubiquitous rubber tire is being exposed, the damage could be about to escalate sharply. The new culprit is electric vehicles. Being substantially heavier than conventional vehicles, they reduce the life of a tire by up to 30 percent, and so could raise demand for rubber by the same amount.
Natural rubber is a milky latex harvested manually by tapping the bark of the Hevea brasiliensis, a tree originally from the Amazon that is now grown widely in plantations, especially in Southeast Asia. World demand has been rising by more than 3 percent a year. But with no sign of increased yields on plantations, that requires ever more land to keep pace.
Yet there has been little outrage. While growers and processors of other tropical commodity crops, such as soy, beef, palm oil, cocoa, and coffee, are under ever greater pressure from both regulators and consumers to show their products are not grown on land deforested to accommodate them, rubber has escaped public attention. When did you last see deforestation-free rubber tires advertised?
One reason for this environmental blind spot is that the truth has not been able to be seen by the remote-sensing systems used to track changing land use in much of the tropics. Unlike with other commodity crops, even the most assiduous analysis of satellite images of forest regions has been unable to distinguish the foliage of monocultures of rubber trees from the canopies of natural forests.
Until now.
A new international analysis published in October has for the first time used high-resolution imagery from the Sentinel-2 earth observation satellites, launched by the European Space Agency, to accurately identify rubber plantations. “The results have been sobering,” says lead author Yunxia Wang, a remote-sensing specialist at the Royal Botanic Garden Edinburgh.
She has found that between 10 and 15 million acres of tropical forests, an area larger than Switzerland, has been razed in Southeast Asia alone since the 1990s to feed our hunger for rubber. This is three times more than some previous estimates used by policymakers, she says. It makes the crop a worse deforester than coffee or cocoa and closing on palm oil for the top spot.
Tires on electric vehicles can wear out 30 percent faster than on conventional models, tire companies note.
Wang found that more than 2.5 million acres of this forest loss has been in Key Biodiversity Areas, a global network of natural sites identified by ecologists as critical for protecting endangered species. And she concluded that the recent boom means rubber plantations now occupy at least 35 million acres of Southeast Asia, where Thailand, Indonesia, and Vietnam are the world’s top three natural rubber producers.
Rubber’s deforestation footprint is also rising fast in Cambodia, says Wang. The country has lost a quarter of its forests in the past quarter-century, with at least 40 percent of new rubber plantations established in forests cleared for rubber production, including the Beng Per Wildlife Sanctuary. And it seems likely there will be many more to come. The Cambodian government has allocated 5 percent of the country for rubber growing, according to Global Forest Watch.
You can see why. Natural rubber is used widely in everything from condoms to sportswear and toys to industrial machinery. But more than 70 percent makes the 2.3 billion new tires the world buys each year. With ever more cars on the roads, demand continues to surge.
Rubber resin collected from a tree near Lubuk Beringin, Indonesia. Tri Saputro / CIFOR
Early this year, Eleanor Warren-Thomas, a conservation scientist at Bangor University in Wales, and colleagues estimated that up to 13 million acres more land will be needed to meet rising rubber demand by 2030. And that, she says, is before considering the potential impact of the switch to electric vehicles.
Electric automobiles are typically a third heavier than equivalent combustion-engined vehicles, largely because of the weight of their batteries. Also, they can accelerate and brake faster, which adds further to wear and tear on tires. Tires are being developed for e-vehicles that will be more robust. But meanwhile, tire companies such as Goodyear say traditional tires on electric vehicles can wear out 30 percent faster than on conventional models.
The rubber tree was one of the first discoveries made by Europeans in the Americas. Christopher Columbus spotted how natives on the Caribbean island of Hispaniola milked its bark to make rubber balls for their children. But it was another 300 years before industrialized rubber production began, first for waterproofing cloth and later for tires. This unleashed a boom in extraction from wild trees in the Amazon rainforest. Tens of thousands of natives were pressed into service to tap the trees, while their traders grew so rich that they turned the Brazilian river port of Manaus into “the Paris of the tropics.”
Eventually, European botanical entrepreneurs took the Amazon seeds and set up plantations in British Malaya, French Vietnam, and Dutch Indonesia, undercutting wild harvesting. In 1926, America’s Harvey Firestone broke a European price cartel by establishing what remains the world’s largest rubber plantation, covering 4 percent of the West African state of Liberia and boasting its own golf course, Mormon church, and yellow American school buses.
“There is a low public awareness that rubber is a crop, let alone a crop that drives deforestation,” says a researcher.
But today such large plantations grow only around 15 percent of the world’s rubber. The rest is produced by around 6 million independent smallholders, who sell via complex networks of middlemen and processors to supply a handful of major tire manufacturers, headed by Michelin, Bridgestone (owners of Firestone), Continental, Goodyear, and Pirelli.
In 2017, several tire and car manufacturers reacted to trends in other commodity-crop businesses by promising to deliver much more sustainable rubber tires. Many subsequently joined the Singapore-based Global Platform for Sustainable Natural Rubber, a collaboration between corporations, academics, and NGOs. But to date there has been little outcome from the promises. The platform hopes to publish next year an “assurance model” designed to “validate member companies’ adherence to their commitments to environmental sustainability.” But so far some of its members concede that it has not gained the same traction as its equivalents in industries such as palm oil.
Tire manufacturers and the Global Platform explain that the fractured and dispersed rubber supply chain makes it hard for them to know precisely where their rubber comes from, much less to root out deforestation. Sam Ginger, who researches the rubber industry at the Zoological Society of London, a science-based charity based at London Zoo, agrees there is a “void of traceability.” But, he says, there is also a void of ambition in the industry.
A rubber tree plantation in North Sumatra, Indonesia. Maskur Has / SOPA Images / LightRocket via Getty Images
Ginger compiles a regularly updated database on the environmental activities of the industry’s major players. His most recent assessment, published in March, found a huge gap between their policies and practice. While 69 percent of the surveyed companies have policies requiring zero deforestation from their suppliers, “only 7 percent of companies publish evidence that they regularly monitor deforestation in supply operations,” he told Yale Environment 360, “And none disclose that they monitor their entire supply chains.”
Why the slow progress? One reason is a lack of public pressure. “Despite the ubiquity of rubber products, there is a low public awareness that rubber is a crop, let alone a crop that drives deforestation,” says Ginger. As a result, “the industry has been able to continue expansion with little scrutiny, while the spotlight has been focused on other commodities, such as palm oil and soy.”
So, what can be done? One route would be through the Forest Stewardship Council (FSC), which certifies deforestation-free forestry and forest products. Again, results have so far been fitful. Currently there is only one tire marketed as FSC-certified: a Pirelli tire launched in 2021 for a single BMW model. (Pirelli did not respond to questions about where this rubber is grown, other than to say it is from smallholders.)
One way to reduce pressure on the world’s rainforests would be to use more synthetic rubber and less natural rubber.
One early advocate of a sustainable approach was the Vietnam Rubber Group, a state-owned planting and processing company. But the company reported last year that just 2 percent of its 1.35 million acres of rubber plantations were certified.
There is also confusion about what sustainability objectives the tire industry should adopt, and how important preventing deforestation is to that agenda.
Typical tires are today made of roughly equal amounts of natural rubber and synthetic rubber from mineral oil, a fossil fuel product. Synthetics are essential for some tire characteristics. So, one way to reduce pressure on the world’s rainforests would be to use more synthetics and less natural rubber.
But if anything, the trend is in the opposite direction. Some manufacturers appear to be prioritizing the phaseout of the fossil fuel footprint of their products, even at the expense of worsening deforestation. Michelin, for instance, says it wants to have all its tires made of 100 percent “biosourced, renewable or recycled” rubber by 2050 and attributes progress so far in part “to a greater use of natural rubber.” Whether or not the trade-off is an environmental gain will depend on both sources of supply and environmental priorities.
A rubber plantation in western Ghana owned by Ghana Rubber Estates Ltd. Cristina Aldehuela / AFP via Getty Images
With the industry seemingly unable or unwilling to deliver on zero deforestation, government regulation could break the logjam. Leading the way is the European Union, whose 27 members use about a tenth of the world’s rubber.
Last December, the EU defied concerted rubber-industry lobbying to add rubber to a list of tropical commodity products, including palm oil, beef, cocoa, soy, coffee, and wood, that importers will be required to demonstrate are deforestation-free under its upcoming Deforestation Regulations. Ginger says there are serious questions about whether the industry is ready or able to comply with the new rules.
Rubber is also among crops listed in the similar Forest Act in the U.S., which is currently stalled in Congress, and in planned U.K. legislation. But both would only penalize those importing rubber grown on illegally deforested land, says Ginger. Deforestation deemed legal by host countries would still be allowed.
By far the biggest rubber market today is China, which consumes more than a third of the world’s rubber. Its demand has driven much of the recent growth in rubber cultivation in Southeast Asia, and China has begun taking a leading role in the international market. State-owned ChemChina bought tire giant Pirelli in 2015, and this year the China Hainan Rubber Industry Group purchased a controlling stake in the word’s bigger rubber trader, Singapore-based Halcyon Agri. While China’s Chamber of Commerce can be credited with producing the earliest draft rules for sustainable rubber production, there has been little buy-in by its companies to date.
Some scientists advocate agroforestry, noting planting rubber among other crops can deliver yields as good as plantations.
What will shift the dial?
Ginger says more transparency in supply system could help drive up standards. Increasing demand could be met from existing plantations, he argues, if big-brand companies would identify and support smallholders to achieve better yields.
Warren-Thomas says another approach is to encourage the adoption of agroforestry in place of plantations. She has studied how this might work in southern Thailand. Planting rubber amid food and other tree crops can deliver yields as good as monoculture plantations, she says. Pilot projects are happening. In Sumatra, Pirelli and BMW, in partnership with Birdlife International and other environment groups, are supporting rubber agroforestry as a means to protect the nearby Hutan Harapan forest.
Warrern-Thomas believes controlling demand is just as important. Recycling of used rubber tires could help, especially by turning them back into new tires, rather than current lower value uses such as bouncy playground surfaces. But the highest priority should be reducing our reliance on the car through improved public transport, she says. “Cars use much more rubber per-person-kilometer than buses.”
And a transition to electric vehicles could make that difference even greater. So if we simply accept the idea that e-vehicles solve all our environmental dilemmas over transportation, we run the risk of unleashing a new round of deforestation.
ASSIGNMENT :3
ENVIRONMENTAL ISSUES CAUSED BY RUBBER INDUSTRY
DONE BY:
“KINGFISHER”
VISHNU .V
PRIYADARSHINI.C.S
HAINY HILBERT
IMK Senate House Campus, Palayam
PREFACE
We know that almost most of the business organizations will raise environmental issues to a certain extent whether big or small. It is as important as making profit for the business organization to adopt necessary measures to alleviate the environmental issues caused as a result of their activities.
We devoted our time to study a business organization and the environmental hazards raised by this organization, though we started this just as an assignment it became our necessity to find maximum methods as possible to curb the environmental problems raised by the company’s day to day activities. The business organization we chose was “RUBBER INDUSTRY”.
We all knew that Kerala is the leading producer of rubber in India and lots of industries are depending on this. Just as it provides income and profit for the many people in Kerala, it also has its deleterious effects on the environment. So the business organization must take it as a moral responsibility to nullify the harmful effects caused by the various by-products produced by them. As far as rubber industry is concerned, the environmental issues are caused due to the chemical usage at the different stages of operation. The end products formed after the use of chemicals will be poisonous and highly toxic and whose effective disposal will become very much essential. Let as go detailed into the production of natural rubber, various operations involved, the environmental problems caused and the methods which can be implemented to abate the deleterious effects caused by the bi-products obtained during its manufacture. We have prescribed some methods which are successfully implemented in Malaysia and Thailand.
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 .The major users of natural rubber are tire and footwear industries.
The raw material used for natural rubber processing is latex mainly tapped from rubber tree (Hevea brasiliensis). 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.
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.
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. The 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.
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.
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.
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 iso-electric 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.
Processing of crumb rubber
This type of natural rubber product is relatively new, which in trade market it is known as “technical specification rubber”.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.
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.
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.
MAJOR ENVIRONMENTAL PROBLEMS
High concentration of BOD, COD, & SS
Wastewater discharged from latex rubber processing usually contains high level of BOD, COD and SS .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.
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.
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.
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).
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..
WASTE DISPOSAL MEASURES
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.
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.
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.
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.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 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.
BIOLOGICAL METHOD INCORPORATED WITH SULPHATE REDUCTION SYSTEM
Low cost operation, high removal efficiency and also producing the biogas as a useful energy sources are some advantages of anaerobic wastewater treatment system. However, this treatment results in the formation of H2S due to consumption of sulphate instead of oxygen by sulphate
reducing bacteria. H2S is toxic and increases the smell of putrid eggs. The gas also causes a big problem in biogas producing systems (Kantachote and Innuwat, 2004). As a result, sulphide could inhibit the activity of methane producing bacteria due to its toxicity. It also revealed that the high amount of sulphide reduced the COD removal. Therefore sulphide elimination is an important stage for this kind of wastewater before a biogas production step.
Sulphate reduction reactor (SRR) has been used for treatment of sulphate rich rubber wastewater from concentrated latex and skim crape. The SRR is needed for reduction of sulphate concentration in wastewater before biogas production by UASB. However, the produced biogas does not have a good quality due to its high amount of H2S. Therefore, the biogas was burnt to remove the very toxic and corrosive H2S gas.Hence, converting the sulphide to sulphur by partial oxidation is needed. It is realized that levels of sulphide oxidation are dependent on oxygen concentration. Additionally, bacteria with ability of oxidizing reduced sulphur compounds can be used for removal of H2S from treated wastewater or gaseous systems. Thus, selection of a microbe that can grow at room temperatures and neutral pH with ability of oxidizing sulphide to sulphur in wastewater is important. Identification of bacteria which can grow in the concentrated latex wastewater was studied by Choorit. In this work, the efficiency of the isolated strains for organic content reducing of concentrated latex effluent was evaluated. The purple non-sulphur photosynthetic bacteria which were isolated from a concentrated latex effluent were cultured in a wastewater without any supplementation. After 40 h of cultivation, 34% of COD was decreased by Rubrivivax gelatinosus and Thiobacillus sp. (Choorit et al., 2003). Thiobacillus sp. meanwhile is extensively used worldwide for removal of both organic and inorganic sulphur compounds in wastewater. Thiobacillus sp. Can reduce inorganic sulphur compounds as an energy source and therefore is used for removing sulphide from wastewater. Four kinds of Thiobacillus sp. were isolated from domestic and rubber wastewaters in Thailand by Kantachote and Innuwat (2004). All isolates could grow in pH of 2.0 – 7.0 (optimum 6.5), temperature of 25 – 45°C (optimum 30 – 35°C) under both aerobic and anaerobic conditions. The results showed that the highest COD removal (54%) can be obtained by Thiobacillus sp. WI1 which cultivated in rubber sheet wastewater for 14 days. However, it does not show the good ability for BOD reduction and it declined by only 33%. Against, the efficiency of strain WI4 for BOD and COD removal was 83 and 46% .Kantachote et al. (2005) also isolated some purple nonsulphur photosynthetic bacteria (PNSB) from rubber sheet wastewater in Thailand. Isolate DK6 as a kind of Rhodopseudomonas shows the best potential for effluent treatment since it can grow well under microaerobic-light conditions and a mixed culture. It has been found that the mixture of 0.50% ammonium sulphate and 1mg/l nicotinic acid with latex rubber sheet wastewater makes the optimum growth of DK6. Using these conditions and either under a pure or a mixed culture, it can reduce the COD and BOD of wastewater to 90%. Therefore, it can be concluded that using the bacteria strains for rubber wastewater treatment is an environmental friendly method and ecologically balanced. This technology is also applicable in other organic waste disposal.
BIOLOGICAL METHOD INCORPORATED WITH PRECIPITATION
One of the parameter that can affect the efficiency of biological treatment processes is the presence of heavy metals such as zinc in wastewater. Adsorption, membrane separation and precipitation are some examples of effective technologies that have been used for removal of heavy metals from wastewater .Currently, simple and inexpensive method such as precipitation by hydroxide is the more common approach that are used in Malaysia. However, this method is not suitable for highly organic polluted rubber wastewater due to zinc-organic ligand complexes production. Therefore, reduction of organic matter that includes heavy metals from wastewater is required. It has been found that some kinds of microorganisms in anaerobic and aerobic processes can be used for this purpose. Microbial flocculation under aerobic conditions can be avoided by high amount of total dissolved solids (TDS) in rubber wastewater. In order to meet the effluent standards, rubber factory have to use some tertiary treatment such as coagulation and filtration processes to remove the excess solids. This significantly increases their treatment and disposal costs. Therefore, reduction of the TDS to a level that does not inhibit or interfere with aerobic microbial aggregation is required. Another method for removal of heavy metal is sulphide precipitation. In this process, use neutral pH which is also suitable for microbial growth In addition to, the removal efficiency of sulphide precipitation is usually better than the hydroxide treatment under a low dissolved solid condition. Therefore, sulphide precipitation is a more promising option than the recent technology. In other hand, adjustment of optimal dosage in hydroxide precipitation system is much easier than sulphide method especially under frequent fluctuation of zinc concentration. In fact, high amount of sulphide can makes malodour and also excessive residual sulphide whilst inadequate dose of precipitant can results in an effluent with high amount of zinc. Therefore, study about the effect of important parameters on sulphide addition control system which is easy and cheap are needed. Chemical and biological processes without any pH adjustment were used for treatment of acidic latex wastewater with high amount of zinc. Sulphide and hydroxide precipitation increased the total dissolved solids of treated effluent by 1.1 and 2.8 times, respectively. 92% of TDS was removed by anaerobic filter in more than 11.8 gCODL-1 day-1 of organic loading rate. For the activated sludge process, average removal efficiencies for COD and BOD were 96.6 and 99.4%. This combined system was verified to be an effective method for purification of rubber thread wastewater.
Another most cost effective system for zinc removal from the wastewater in Malaysia is using a mixture of 800 mg/l of sodium sulphide and 5 mg/l of polyelectrolyte LT27, respectively. The optimum settling time and flocculation time were 60 and 20 min. The best results can be obtained in a speed of 20 rpm in a 110 mm diameter reactor. The approximate cost of this system is RM1.04/m3 (US $0.26/m3) of wastewater discharged .In a study by Kolmetz et al. (2003), the efficiency of an expanded bed biofilm reactor in the treatment of wastewaters contaminated with heavy metals has been investigated for rubber product manufacturing industry. Some advantages of biofilm systems are ability to retain relatively high biomass concentrations that results in shorter liquid retention times, better performance stability and higher volumetric removal rates. In the study, it has been found that the process could achieve 60 to 90% removal of Zinc. In addition, the efficiencies of an expanded bed biofilm reactor and a sequencing batch biofilm reactor for heavy metal adsorption were studied using Zn and Cu containing wastewaters. The results showed that heavy metal adsorption by these reactors are 50 – 95%.
ADVANCED RUBBER WASTEWATER TREATMENT METHODS
Currently, several effective methods have been used for treatment of rubber wastewater in Thailand which makes natural rubber industry more environmentally friendly and economically viable. In response to problems associated with rubber wastewater and its effect on the Malaysian’s environment, further research can be performed to develop the novel methods for treatment of this wastewater. As follow some inventive technologies that were used in Thailand and Malaysia will be described.
Natural process
A constructed wetland is an artificial marsh or swamp that includes substrate, vegetation and biological organisms contained within a physical configuration. Suitability designed and operated wetlands have considerable potential for lowcost, efficient and self maintaining wastewater treatment systems. This system has demonstrated capability to remove nutrients, suspended solids, organic compounds, pathogens and metallic ions and to increase oxygen and pH levels in wastewater. In comparison to conventional systems, lagoons or land application flow, wetlands waste treatment systems require fewer amounts of capital and operating costs, minimal operator training and land area Puetpaiboon studied the possibility of treat wastewater from a rubber sheet factory in Thailand using the pilot-scale experiment constructed wetland (CW). This system consisted of vertical flow constructed wetlands (VF) followed by subsurface flow constructed wetlands (SSF) with nut grass (Cyperus rotundus Linn.) plantation. The tested COD loadings in this experiment were 500, 750, 1000 and 1250 kg COD/ha.d. The results showed that the best removal efficiency of BOD5, COD, SS and TKN were 99, 99, 93.6 and 97.8%, respectively, using VF followed by SSF with nut grass (C. rotundus Linn.) plantation at 750 kg COD/ha.d.
Biological method
One of the extensively used methods for removal of dissolved and colloidal organics in wastewater is the activated sludge process. This system changes the dissolved and colloidal organic contaminants to a biological sludge which can be removed by settling. After a primary settling basin, usually use an activated sludge process as a secondary treatment. Ratanachai and Chevakidagarn surveyed two rubber treatment plants, which are single-stage activated sludge process in Songkhla, Thailand. They reported that the suspended solids removal capacities were low (from 78 to 87%). The treatment plants often had bulking and rising sludge problems because of insufficient oxygen concentrations. Thus, it is recommended that an appropriate oxygen control system to be included in this system for the rubber industry to ensure sufficient oxygen is provided. This will assist in compliance with the effluent standards. Chevakidagarn also upgraded the operation of conventional activated sludge treatment plants to save aeration energy and at the same time to provide better utilization of existing plant capacity for nutrient removal without major financial investment. The first stage of the experiments was to observe the possibility of using oxidation-reduction potential (ORP) for aeration control in treatment plant fed with the wastewater from the latex rubber industry. The results proved that the ORP was greatly affected by the change in air supply. However, it was also affected by the fluctuation of wastewater temperature, which contributed to the bulking sludge problem. In another study, Chevakidagarn used surrogate parameters for rapid monitoring of contaminant removed for activated sludge treatment plant for rubber and seafood industries in Southern Thailand. UV absorbency at various wavelengths was used in this study as surrogate parameters, for predicting the removal capacity of each plant. The results showed that UV absorbency at 220 nm can be used as a parameter to predict nitrate nitrogen concentrations which less than 15 mg/l. Also, it was found that 550 and 260 nm are suitable wavelengths for predicting of suspended solids concentration and COD. In generally, aerated lagoon or activated sludge can reduce fault smell of rubber wastewater but have a high consumption of electricity and relatively high investment and operation costs
Chemical methods
Electrochemical methods: Longer hydraulic retention time is needed for treatment of rubber wastewater by conventional biological methods and sometimes exposure to failures if shock loaded. Recently, much more attention has been drawn to electrochemical method for treatment of wastewater due to the cost, ease of control and the increased efficiencies provided by the use of new electrode material and compact biopolar electrochemical reactor. The electrochemical treatment methods are preferred as the less required of hydraulic retention time.These systems are not successful because of variation in wastewater strength or due to the existence of toxic material. Generation of chlorine or hypochlorous acid is the best alternative method for performing the electrolytic treatment. Therefore, there is a considerable interest for developing a new method of wastewater treatment based on in situ hypochlorous acid generation as a kind of electrochemical. An electrolytic cell including of graphite as anode and stainless sheets as cathode was providing the hypochlorous acid. For organic destruction of the rubber wastewater used, the produced hypochlorous acid acts as an oxidizing agent. The results showed the efficiency of 99.9 and 98.8% for COD and BOD removal. Moreover, it has been indicated that pH 7.3; TOC 45 mg/l; residual total chlorine 136 mg/l; turbidity 17 NTU and temperature 54EC can be obtained by this system for an influent with the initial pH 4.5; current density of 74.5mA/cm2; sodium chloride content 3% and electrolysis period of 90 min, respectively. At the same condition and up to 2% of sodium chloride concentration, 95.7 and 88.6% of COD and BOD removal, pH 7; TOC 90 mg/l; residual total chlorine 122 mg/l; turbidity 26 NTU and temperature 60EC can be achieved
Ozonation
Some of the non-biodegradable materials and also ammonia nitrogen of natural rubber wastewater cannot be completely removed using biological process. Therefore, the organic contents of effluent are above those of the standard limits. It is generally approved that ozonation transforms refractory or poorly degradable organic materials into by-product with smaller molecular size. Moreover, it has been found that ammonia can be converted to nitrate by ozonation which usually makes biodegradability. Rungruang and Babel (2008) studied the efficiency of batch activated sludge process (BAS) with or without ozonation for rubber wastewater treatment at Chonburi, Thailand. The effects of different contact times (0 – 90 min) and ozone dosages (37.20, 56.90 and 66.44 mg O3/L O2) at various pH (7.4, 9.0 and 11.0) on wastewater treatment were studied. As a result, it was found that 66.44 mg O3/ L O2 of ozone dosage; pH of 9.0 and 30 min of contact time are the optimum conditions for reduction of pollutants. It has been found that the combination of BAS and ozonation makes higher removal efficiency for all parameters compared to another system
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. invention of electrostatic precipitator(ESP) is very useful in trapping the smoke particles and aerosols that are very harmful. though the efficiency of ESP start decreasing as the smoke particles start accumulating in the electrode and its removal becomes important. Even rather than relying more on the wood burning we can make optimum use of the environmental friendly sunlight to dry the rubber sheets and even the discharge of smoke can be controlled their by regulating the energy usage.
CONCLUSION
Environmental situation in rubber production varies according to the nature of each industry. In rubber sheet drying industry, smoke particles contribute to pollution in workplace and neighboring atmosphere. The high concentration of aerosol particles in the atmosphere can cause adverse effects on the workers health. And also waste water effluents are also a serious concern as they contain highly toxic substances which if not treated properly can cause havoc to not only environment but also to humans. So we have studied some popular methods implemented in the major rubber producing countries like Thailand and Malaysia which we can adopt here in our Kerala and their by reduce the deleterious effects of the chemical substances involved in the processing of rubber.
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