ARSENIC REMOVAL PROJECT
Available technologies for arsenic treatment:
Method Advantages Disadvantages Co-precipitation: No monitoring of a break through is required. Relatively low cost simple chemicals. Low capital costs. Serious short and long term problems with toxic sludge. Multiple chemicals requirement Operation requires training and discipline. Alum coagulation Durable powder chemicals normally available Efficient pre-oxidation is a must Iron coagulation More efficient than alum on weigh basis Medium removal of As (III) Lime softening Most common chemicals Re-adjustment of pH is required. Sorption techniques: No daily sludge problem. Requires monitoring of break through or filter use. Requires periodical regeneration or medium shift. Activated alumina Relatively well known and commercially available. Re-adjustment of pH is required. Iron coated sand Expected to be cheap. No regeneration is required. Yet to be standardized. Toxic solid waste. Ion exchange resin Well defined medium and hence capacity. High cost medium. High tech operation & maintenance. Regeneration creates a sludge problem. Membrane techniques: Low space requirement. Capable of removal of other contaminants, if any. High running costs. High investment costs. High tech operation and maintenance. Toxic wastewater. Re-adjustment water quality is required. Reverse Osmosis Membrane does not withstand oxidizing agents.
ARSENIC REMEDIATION TECHNOLOGY :
- In-situ remediation of arsenic contaminated ground water using iron filings permeable walls,
- In-situ remediation of arsenic contaminated sandy soils by incorporating iron filings into the sand,
- In-situ treatment of contaminated lake and wetland sediments, ·
- Treatment of domestic drinking water supply, and
- Ex-situ treatment of groundwater.
Traditional arsenic contaminated sites include areas of mining activities and smelters. Arsenic can be also found in coal and coal combustion by-products. Inorganic arsenic species in contaminated industrial sites exist in the arsenate (oxidation form = V), arsenite (oxidation form = III), arsenic sulfide (HAsS2), elemental etc.
Elemental iron on the other hand, in the presence of aqueous solution, can be oxidized both aerobically and anaerobically providing electrons for the reduction of other redox sensitive chemical species such as arsenate and sulfate. This invention presents a new method for the immobilization of inorganic arsenic species, such as arsenates and arsenites, by iron filings. The method uses iron filings (zero valent iron) and sand to reduce inorganic arsenic species to iron co-precipitates, mixed precipitates and, in conjunction with sulfates, to arsenopyrites. Other constituents may be added to the mixture to control porosity or chemistry. The method may be employed, for example, as part of an in-situ funnel-and-gate groundwater treatment system or ex-situ as part of a groundwater extraction and treatment system (pump and treat).. Inorganic arsenic contaminated water, spiked with equivalent sulfate concentrations passes through an iron filings/sand "filter". This results in removing most of the arsenic from the solution.
Available arsenic removal technologies are neither cost effective for the poor nor easily operable and maintainable. For example devices based on sorptive techniques need periodic regeneration by washing as flocculate particles clog the filter media slowing down flow rate which makes those devices cumbersome to use After some days there may arise the necessary to change the filter media which demands extra replacement cost. Another process is coagulation-flocculation-coprecipitation with chemicals that may leave harmful residual elements in dissolved state in water. If coagulated with alum and potassium permanganate, there is a chance of having residual aluminium in treated water that may have toxic effects on human nervous system. Again manganese may contribute undesirable tastes to beverages and stains to laundering. Even we don't know whether these technologies are efficient enough in removing a significant portion of arsenic or not.
Researchers in Australia developed a simple method to remove arsenic from contaminated drinking water or mining waste using just sunlight and air (Young, 1996). A century old water purification unit of Faridpur (Bangladesh) Water Supply reduces arsenic contaminated water below Bangladesh standard simply by sunlight and filtration (Photo ).
Faridpur Water Supply (almost a century old) reduces arsenic concentration from 220 µg/l to 42µg/l.
The ultraviolet radiation in sunlight helps the dissolved oxygen to oxidise the arsenic to the less toxic form, which can then be precipitated (iron arsenate) and removed. During 1998 and 1999 experimental studies were carried out in Bangladesh simply using sun, air, iron (if necessary) clay pots and sand filter. The result was surprisingly lower than allowable standard. The effluent of acid rinses is mixed with the caustic rinses and this mixed arsenic waste can then be disposed on a prepared bed of cow-dung in a shallow hole dug in earth. The micro-organisms in cow-dung transform the arsenic to gaseous arsine.
The sunlight /air/clay pot method costs almost nothing and can be carried out all over Bangladesh without relying foreign technology. But a cheaper solution that would take trouble to go amongst the people and teach them the simple technology does not create enough money and does not attract NGOs and government agencies.
The principal goal of this project is to introduce a low cost-effective, efficient and appropriate method of water purification, ie;
Formation of village committees who will be trained to look after water purification and disposal units, health and environmental aspects.
Regain traditional wisdom, enhance traditional profession - clay pottery, jute bag maker, stop use of plastic, use biological pesticides Neem (Azadirachita indica) etc.
Water purification from 1000 tube wells (1000) families contaminated with arsenic/enteric bacteria, coliform bacteria by using sunlight, air and earthen pot method
Introducing inexpensive sand filters using local clay pot, sand (and charcoal, if water is contaminated with pesticides, etc.).
Cleaning , maintenance and self production of sand filter.
Innovating clay potters to introduce optimal water containers and sand filters.
Disposal of arsenic precipitates in cow-dung pits.
If tube well near water pond is arsenic free or low arsenic, advise to shift other tube wells to this site
Construction of water tank that obtains sunlight and passes through sand filter for school children (500-800) .
Cultural and social meetings for transfer of knowledge.
Population of this sub-continent knew since thousands of year sunlight disinfection and charcoal filtration method of water purification. If the villagers get back their dying wisdom to produce, and maintain small water purification units under the present circumstances, there are chances that a population could be saved.
Mr. Syed Marghub Morshed, Secretary Ministry of Environment and Forest, Government of Bangladesh writes (11.06. 2000):
This project is completely different from other Arsenic mitigation project because villagers will produce clay pots, sandfilter etc. and later distribute to other villagers. This simple and rapid mitigation project can be spread all over Bangladesh. This project is also the only project in Bangladesh in which arsenic-sludge disposal is done by using a very inexpensive but effective microbial transformation.
There are several arsenic separators in the market.. All these filter or separators have disadvantages - too expensive, difficult to operate, stop flowing water after a few run, one poison is replaced by others, no disposal programme etc. Proshikha intends to make brick from arsenic sludge (Baral, PHA Conference 7.12.2000). National Occupational Commission Australia (1999) reports arsenic trioxide filings will explode on heating and besides bricks are used for road construction in Bangladesh and will further contaminate surface and ground water.. It is likely to recycle to nature and wall with dangerous substance pose potential health hazard.
With our co-operation the Clay Potters of Madhavpur, Faridpur have introduced simple and cheap filter (2003). This filter will be soon introduced in village markets. All profits go to the poor clay potters.
In early 1998 author published sunlight-air-clay pot method found to separate arsenic from drinking water. After travelling in several villages in Bangladesh I found "open dug hole" or
bangla Kua or Indira does not contain arsenic. At Alipur, Faridpur I found an open dug hole "Kua" and a tube well where water from the tube well contained 0.50mg/L arsenic (WHO standard 0.01mg/l) and water from "Kua" did not contain any arsenic. But this open dug hole has vanished from Bangladesh through UNICEF and other agencies.
Open dug hole "Kua" can be dug only during February, March and April at low water level and costs about Tk. 5000. It should be monitor properly. There is hardly any time, if agencies, organisations want to stop arsenic poisoning now.
UNICEF/agencies should rebuild the open dug hole and send all tube wells to their head quarters, since their consultants (British Geological Survey and Mott MacDoland Ltd U.K) have reported that arsenic was always present in Bangladesh.
Water from the open dug hole can be improved through protection (keep it clean) and bacteria can be removed through solar radiation (without cost) or through boiling. A simple filter produced and maintained by the villagers cannot cost more than 100 Taka.
Faridpur Water Supply was built during British period which contains two open basins (Photo) - first oxidation chamber and the second sedimentation chamber. The water pumped from the ground water contains a high arsenic concentration but after oxidation, sedimentation and filtration water has been below Bangladesh standard. This process can be further improved. Such system can be easily introduced on small and large scale in the most affected areas on community basis and does not require outside know how and import high technology. Unfortunately, every day the arsenic sludge is dispose of nearby water pond. The arsenic sludge can be dispose of under cheap biological disintegration method.Project Report 2003- Clay Pot Filter (JIBON)
CLOTH FILTER COULD CUT CHOLERA DEATHS
Simply filtering drinking water though cloth from old clothes can cut new cholera cases in half, researchers have found. The technique was tested in Bangladesh, where it could potentially save many lives. Cholera is a waterborne disease that causes severe diarrhoea. It kills tens of thousands of people a year world-wide
Scientists have long known that the bacteria that cause cholera live in a mutually beneficial symbiotic relationship with tiny aquatic organisms called plankton. Researchers from the US National Science Foundation decided to test the theory that filtering plankton out of drinking water would also remove the cholera bacteria. They found that an old sari cloth, folded at least four times, was as successful as specially designed nylon filters at removing plankton from water
The scientists then tested the effectiveness of both sari cloth and nylon filters at preventing new cholera cases in Bangladesh villages over an 18-month period. Villages trained to use sari cloth experienced about half the historic average of new cholera cases. The nylon filter produced marginally less impressive results.
The researchers say that not only does the use of old sari cloth, and similar fabrics worn in other parts of the world, appear to be an effective way to combat cholera, the material is cheap and convenient to obtain. Lead researcher Dr Rita Colwell told BBC News Online: "The method can save thousands of lives during massive epidemics, particularly those of children under the age of five."
Dr Claire-Lise Chaignat, coordinator of the World Health Organization's global taskforce on cholera control, said the technique sounded "very promising". She said: "Cholera affects only the poorest of the poor who have hardly any access to safe water or proper sanitation. "A simple method of cleansing water for these people would be very interesting."
The research is published in the Proceedings of the National Academy of Sciences.
(Source: BBC, Tuesday, 14 January, 2003, 00:16 GMT )
The people will invent more methods and survival strategies, if we really want to survive and refused to vested business interest of many western companies offering inadequate and expensive technologies. These methods are not practised in their own countries.
We do not want millions of rural poor to end up with slow, painful suffering. I still cannot forget the face of Sulekha and the helpless family.
Cleaning Drinking Water with Bacteria
Bacteria and drinking water are not two things that usually go together very well, but according to a new study, certain species of microbes may help remove trace minerals such as zinc, selenium and even arsenic from your drinking water in the future. In nature, sulfate-reducing bacteria (SRB) play an important role in binding sulfate in water.
Using x-ray experiments, the researchers discovered that the bacteria formed mineral deposits from the water that surrounds them, binding them in the form of tiny spheres. In this particular case, the bacteria bound zinc and sulfate, and they did it so effectively that the zinc concentration in the spheres became a million times higher than that in the surrounding water. Indeed, the spheres consisted almost entirely of zinc sulfide (see image). This ability makes the tiny life-forms potentially very useful in the process of water treatment. They could be used to remove zinc, selenium and even arsenic traces from contaminated water, as in the mining tunnel, or even from drinking water supplies( Harald Franzen, Dec.4, 2000)
Aquatic weed (water hyacinth) may remove arsenic from water
An aquatic weed has the potential to save thousands of lives from arsenic, according to an article published by the Royal Society of Chemistry (RSC) in the United Kingdom last week, reports BSS. A team led by Dr Parvez I Haris of De Montfort University, the UK, has identified the weed which, he claimed, can save lives by removing arsenic contamination ffrom tubewells in Bangladesh,said a message received here today. The water hyacinth plant grows prolifically around the world, often clogging up waterways. The plant is called a "green plague", but Haris's report in the Journal of Environmental Monitoring suggests that it may be a natural solution to a natural problem, arsenic. The introduction of tubewells in Bangladesh brought fresh water to the majority of the 140 million population, but the presence of naturally-occurring arsenic has contaminated the water supplies far in excess of the WHO guideline of 10 ppb (parts per billion).
Long-term exposure to low levels of arsenic can cause numerous diseases, including cancer. Millions of people are already suffering and more than 70 million people in the region are at risk. Dr Haris and his team discovered that the powdered dried roots of the water hyacinth can rapidly remove arsenic from water, reducing the arsenic concentration to below the WHO guideline levels. He suggests a simple filtration system utilising the roots would be able to remove arsenic both from drinking and irrigation water.
Dr Haris was inspired to investigate the ability of the water hyacinth to absorb arsenic during a visit to Bangladesh last year. Arsenic contamination of water supplies in the region was first brought to the world's attention by another high-impact RSC publication, The Analyst, in 1995. However, little has been done to remedy the situation, which was again highlighted in the Journal of Environmental Monitoring in 2004. Dr Haris and his team said Bangladesh remain as the most vulnerable country in the world to arsenic-contaminated water.The possibility of using an abundant, cheap, natural resource to reduce arsenic levels has the potential to end the suffering of millions and save thousands of lives, they added (Bangladesh Observer, March 25, 2005).
Removal of Arsenic in Water by Iron Oxide Coagulation and Filtration
Current research in arsenic removal technologies focuses on several main techniques: oxidation, co-precipitation and absorption into coagulated floccs, lime treatment, absorption into sorptive media, ion exchange resin and membrane techniques (Ahmed 5). Arsenic-contaminated ground water is a major concern for many countries. In Bangladesh, arsenic contaminated ground water is most commonly found in tube wells, and contributes greatly to the low standards of drinking water. In Sweet Home, Oregon arsenic has recently been found in the bedrock and ground water. Arsenic is the world?s problem and new efficient ways to deal with this problem need to be developed. Our investigation may contribute to a better solution for treating arsenic-contaminated water throughout the world. Originally this investigation was designed to compare a new system of arsenic removal using coagulation, and a method using the hyper accumulator pteris vittata, or Chinese Brake Fern; however, the investigation had to be revised due to the fact that not enough ferns were purchased and they all died. The final investigation is designed to evaluate the efficiency of a new system of arsenic removal.
In the process the iron oxide bonds with the arsenic forming large visible floccs. These floccs are large enough to be filtered out by a layer of sand thus purifying the water. Potassium permanganate is used to aid in the reaction. Our hypothesis is that this system will perform moderately well, but might not filter out all the iron and arsenic floccs, and may color the water. This is because our system for filtering the floccs out is very simple compared to the BUET system, and because our chemicals are different than those used in other arsenic-removal systems
1. Measure 50 ml of arsenic water to be tested
2. Test water using arsenic test kit
3. Measure 2000 ml water from the same source and pour into 2-gallon mixing bucket
4. Mass 300 mg Ferric Oxide
5. Mass 3 mg Potassium Permanganate
6. Pour chemicals into mixing bucket
7. Agitate for 10 minutes using glass stirring rod
8. Pour water into top bucket of the MINAJE system
9. After water has filtered through completely (10-15 min.), measure treated water
10. Measure 50 ml of treated water and test using arsenic test kit. 11. Record data
300 mg ferric oxide per test (Fe2O3) 3 mg potassium permanganate (KMnO4) 1000 ml graduated cylinder Glass stirring rod MINAJE treatment system 2L arsenic-contaminated water per test EZ Arsenic Test Kit
Result obtained show that all contaminated water show absence of arsenic. The results of the investigation clearly show that the system for arsenic removal is definitely effective.
New device to detect arsenic level below 10 microgram
A new, simple and cheaper method to detect arsenic level in water has been evolved in Kushtia by a group of foreign scientists. The team was led by a Kushtia-born scientist, now a citizen of Canada. Arsenic level less than 10 microgram per litre (ug/L) can be measured by using the method while those now used being in the country can not detect the contamination if it is below 50 microgram per litre.
The World Health Organization (WHO) - prescribed tolerable limit of arsenic in water for humans is 10 microgram per litre. Thousands of people are being affected in the country with the deadly poison as they are unknowingly taking water with arsenic contamination of around 50 microgram per litre. The new method is more accurate and precise and does not need use of atomic absorption spectrometer or other expensive equipment, according to the innovators.
arsenomolybdate' methodIn the 'arsenomolybdate' method arsenic can be detected by using a simple spectrophotometer, distillation unit for purifying water, analytical balance, top-loading balance, glassware, an arsine generator, scrubber and absorber and some very common reagents.
All these cost Tk 6500 only while the methods now being used cost around Tk 37,000, Dr. Bibudhendra Sarkar, leader of team of foreign scientists, told this correspondent recently. Any household or a small community can set up a small laboratory, which will open a new dimension in supply of arsenic-free water, he said. The innovation has been made after eight year's experiment in four Kushtia villages by volunteer scientists called Scientists Without Borders, headed by Dr Bibudhendra Sarkar of the Hospital for Sick Children and Faculty of Medicine, University of Toronto, Canada ( Source: 19 July, 2005, The Daily Star).
Ineffectiveness and Poor Reliability of Arsenic Removal Plants in West Bengal, India
“Decontamination plants installed at wells throughout West Bengal are failing to reduce arsenic in local drinking water to safe levels,” an article published in the July issue of the Nature journal has reported, quoting a report published in the Environment, Science and Technology magazine. “Of 18 arsenic-removal plants (ARP) monitored over a two-year period, none reduced arsenic levels below the maximum safe value stipulated by the WHO, says epidemiologist, Mr Dipankar Chakraborti of Jadavpur University whose team carried out the tests,” the Nature article said.
The article quoted the report titled, ‘Ineffectiveness and Poor Reliability of Arsenic Removal Plants in West Bengal, India’ published in the Environment, Science and Technology magazine. This report has been prepared by a team from the School of Environmental Studies, Jadavpur University and the Indian Statistical Institute. The members of the team are M. Amir Hossain, Mr Mrinal Kumar Sengupta, Sad Ahamed, Mohammad Mahmudur Rahman, Mr Debapriya Mondal, Mr Dilip Lodh, Mr Bhaskar Das, Mr Bishwajit Nayak, Mr Bimal K. Roy, Mr Amitava Mukherjee, and Mr Dipankar Chakraborti. According to the Environment, Science and Technology magazine, the revised manuscript of this report was received on 28 February, 2005 and and it was accepted on 9 March, 2005.
The Nature article goes on to say: “The findings come as a blow to efforts to address what has been called the worst mass poisoning in history, in which millions of people were exposed to dangerous or fatal levels of arsenic in their water. The arsenic comes from natural geological sources that weren’t recognised when the wells were dug during the 1970s. An estimated 35 million people were drinking from such wells, dug by aid agencies so that locals wouldn’t have to rely on rain and river water, which is often contaminated. To try to fix the situation, some 2,000 arsenic-removal plants were installed in wells in West Bengal, and many more in Bangladesh, at an average cost of US$ 1,500 each.”
Mr Chakraborti and his colleagues tested 18 such plants, from 11 different manufacturers in India, Germany and the United States. The average arsenic concentration in water treated during a two-year period was 26 micrograms per litre — more than twice the value recommended by the WHO. Only two of the plants met the Indian standard value for arsenic levels, which is five times higher than that of the WHO,” the Nature article adds. The original report published in Environment, Science and Technology says that: “Our 2-year study showed that none of the ARPs could maintain arsenic in filtered water below the WHO provisional guideline value (10g/L) and only two could meet the Indian standard value (50 µ/L) throughout.”
When asked to comment, Mr Asim Barman, state public health and engineering secretary, said: “ Their report is not correct. Some of the ARPs may have failed to attain the permissible standards, but all are not same. The state government, after all, has some responsibility and it has spent a lot of money in installing these ARPs (The Statesman, 1975).
A powder that purifies water won an award in Stockholm. Manufactured by Procter & Gamble, will it be used in India?
A WATER treatment powder has won the 2005 Stockholm Industry Water Award for innovative corporate development of water and wastewater process technologies. The powder — Purifier of Water, or PUR — was developed by Procter and Gamble, USA. It enables point-of-use water treatment through flocculation, sedimentation and disinfection, the same processes that conventional water treatment is based on. But treating water with chlorine tablets does not remove its turbidity while PUR does, claims the company. “Since its introduction in 2000, PUR has provided 260 million litres of safe, clean water in many countries, including the tsunami-ravaged region of South Asia, where 15 million sachets were delivered,” said Greg Allgood, director of the Children’s Safe Drinking Water Programme, P&G.
PUR is available in a single-use sachet that can purify 10 litres of water. Its ingredients include ferric sulphate (flocculant) and calcium hypochlorite (disinfectant). When the powder is added to water and it is stirred for five minutes, flocculation occurs, followed by precipitation. The water is then filtered through a cloth to remove the precipitate. The powder leaves residual chlorine in water for continued disinfection.
Besides organic matter and micro-organisms, the powder even removes heavy metals such as arsenic, chromium and lead from water, P&G claims. The residue should be discarded out of reach of animals and children, the company advises. To promote PUR, P&G worked closely with non-governmental organisations, local and national governments and health organisations like the Centres for Disease Control and Prevention (USA), the International Federation of the Red Cross and Red Cresent Societies, Unicef and the Johns Hopkins University (USA). Said Allgood, “We plan to expand beyond the current social markets of Haiti, Uganda and Pakistan at the rate of two countries per year.”
The company claims PUR- treated water meets the standards of the World Health Organisation for drinking water. Clinical trials conducted by CDC and Johns Hopkins University showed significant reduction in diarrhoea in Guatemala (40-72 per cent), Kenya (17-42 per cent), Liberia (59-64 per cent) and Pakistan (87-95 per cent). Besides, PUR-treated arsenic contaminated (130 to 430 parts per billion) well-water samples from Bangladesh, contained less than 10 ppb (Who guideline value) of the toxic element, according to the company.
“In the USA, a PUR sachet costs three cents. In countries like India it will cost Rs 3.50 due to customs duties and taxes. Our effort is to manufacture the product locally so as to cut down the costs,” said Chris Smith, P&G, UK. So far, P&G’s strategy had been to supply PUR through governments and NGOs to the needy. Allgood explained the challenges, “Market surveys showed repurchase rates (five to 13 per cent) are not sufficient for sustainable commercial approach by P&G. This calls for a change in consumer habit and hence necessitates broad partnerships with public health groups.”
Will this product be used in India? Said Paul Deverill, Unicef, India, “The product seems to be impressive. However, given the regional diversity and magnitude of problems in India, Unicef in collaboration with a leading water testing laboratory will study its effectiveness and user friendliness. If results are satisfactory, we would take up the matter with the government of India.” Besides costs, there also is a concern about the contaminant-laden residues and their disposal (The Statesman, CSE/Down to Earth Feature Service, 1975).
Plastic bottles could clean arsenic-contaminated water
A team of chemists at Monmouth University, United States, found that bits of plastic coated with cysteine, a common molecule found in foods, bind to arsenic.
“Laboratory experiments have shown that the method has the potential to be very efficient and very cost effective,” Tsanangurayi Tongesayi, lead author of the study and an assistant professor at the university told SciDev.Net. “The method uses plastics which are cheap and locally available,” he added. “[It] is eco-friendly because it involves recycling of plastic bottles [and] is also safe because the chemical ingredients used are not toxic.”
In Bangladesh alone some 35 million people are exposed to arsenic contamination from drinking water, according to the Department of Public Health Engineering (DPHE), and estimates say around 100 million in the developing world are affected. Arsenic has been linked to a variety of health problems from stomach pains and blindness to various cancers — one in five deaths in Bangladesh has been linked to arsenic exposure. Tongesayi presented his team’s findings last week (31 August) at the annual meeting of the American Chemical Society. The researchers showed that the method can reduce the arsenic content from 20 parts per billion (ppb) — two times higher than the safe standard set by the US Environmental Protection Agency for drinking water — to 0.2 ppb. Tongesayi said they were now looking for a commercial partner to scale up the process.
But Guy Howard, the UK Department for International Development’s Research and Evidence Representative in South Asia, said: “Simply looking for a commercial partner is not the key to scaling up”. The technology first has to be shown to work in field conditions, which may vary a lot and where other chemical species compete with arsenic for adsorption sites, he said. He added that the technology also needs to be shown to be acceptable to potential users, who must understand how to use it and when to replace filters, for example. Some previous technologies that worked in the lab, have failed at these two steps, Howard said.
“Finally such a technology has to pass regulatory requirements — some scientists appear to believe these do not exist in countries like Bangladesh. The reality is quite the reverse — Bangladesh has a very stringent technology verification process and technologies are only accepted for wide deployment once this is passed,” he said.
Shudhir Kumar Ghosh an engineer at the DPHE said the new method has good prospect in Bangladesh since it will use low cost plastic bottle and the easily available chemical. He
added that there are already various methods in use to remove arsenic from drinking water in Bangladesh, including six chemical-based technologies — half of those invented locally. Such methods can be useful at a household level but need constant monitoring of the presence of the chemical and arsenic in water, Kumar Ghosh said. (Dawn, Sept 12, 2011)
Last Modified September 15, 2011