Does iron ore mining need water ? Why

Why does iron ore mining need water?

For magnetite mining, water is used in ore processing, to increase the quality and concentration of iron. After crushing, the dry ore is mixed with water and wet screened. This allows the ore to be directly fed into a steel pellet plant without further treatment. Some operations also use water to transport the ore via a slurry pipeline. Importantly, a significant amount of the water used in processing and transport is recycled.

Waste Characteristics

In certain mines with ores with high sulfur content, drainage from mine workings and waste heaps can become highly acidic and contain dissolved high concentrations of heavy metals. This Acid Mine Drainage (AMD) can have a pH of 3 or lower; sulfate levels of 800-1800 milligrams per liter (mg/L); copper levels up to 50 milligrams per liter (mg/L); iron levels up to 1000 milligrams per liter (mg/L); lead levels up to 12 milligrams per liter (mg/L); zinc levels up to 1700 mg/L, and cadmium levels of several milligrams per liter depending on the contents of the ore. The tailings pond effluent may also contain concentrations of chromium of several milligrams per liter. Base metal mining tailings decant may also contain high concentrations of thiosalts. Chemicals used in metal concentration (floatation and other) processes could also pose toxicity when released in effluents.

Surface runoffs may also pose significant environmental problems through erosion and carry-over of tailings and other mining residues. Explosives, such as ammonium nitrate, may also be present in surface runoff. Contamination of surface water can also occur from transport of mined material and from machinery maintenance and repair.

Significant levels of dust, above to 3 kilogram per ton (kg/t) (with a range of 0.003 to 27 kg/t) of ore mined, may be generated. This dust can be generated by extraction activities, crushing, ore beneficiation, transportation and traffic, and by wind borne losses. Significant releases of metal (including mercury) containing dust may result from the drying of the ore concentrate.

Process

Iron ore is converted into various types of iron through several processes. The most common process is the use of a blast furnace to produce pig iron which is about 92-94% iron and 3-5% carbon with smaller amounts of other elements. Pig iron has only limited uses, and most of this iron goes on to a steel mill where it is converted into various steel alloys by further reducing the carbon content and adding other elements such as manganese and nickel to give the steel specific properties.

Extraction

Refining

• The mined ore is crushed and sorted. The best grades of ore contain over 60% iron. Lesser grades are treated, or refined, to remove various contaminants before the ore is shipped to the blast furnace. Collectively, these refining methods are called beneficiation and include further crushing, washing with water to float sand and clay away, magnetic separation, pelletizing, and sintering. As more of the world's known supply of high iron content ore is depleted, these refining techniques have become increasingly important.
• The refined ore is then loaded on trains or ships and transported to the blast furnace site.

The Manufacturing Process

Charging the blast furnace

• After processing, the ore is blended with other ore and goes to the blast furnace. A blast furnace is a tower-shaped structure, made of steel, and lined with refractory, or heat-resistant bricks. The mixture of raw material, or charge, enters at the top of the blast furnace. At the bottom of the furnace, very hot air is blown, or blasted, in through nozzles called tuye'res. The coke burns in the presence of the hot air. The oxygen in the air reacts with the carbon in the coke to form carbon monoxide. The carbon monoxide then reacts with the iron ore to form carbon dioxide and pure iron.

Separating the iron from the slag

• 2 The melted iron sinks to the bottom of the furnace. The limestone combines with the rock and other impurities in the ore to form a slag which is lighter than the iron and floats on top. As the volume of the charge is reduced, more is continually added at the top of the furnace. The iron and slag are drawn off separately from the bottom of the furnace. The melted iron might go to a further alloying process, or might be cast into ingots called pigs. The slag is carried away for disposal.

Treating the gases

• 3 The hot gases produced in the chemical reactions are drawn off at the top and routed to a gas cleaning plant where they are cleaned, or scrubbed, and sent back into the furnace; the remaining carbon monoxide, in particular, is useful to the chemical reactions going on within the furnace.

A blast furnace normally runs day and night for several years. Eventually the brick lining begins to crumble, and the furnace is then shut down for maintenance.

Byproducts/Waste

There are a great many possible environmental effects from the iron industry. The first and most obvious is the process of open pit mining. Huge tracts of land are stripped to bare rock. Today, depleted mining sites are commonly used as landfills, then covered over and landscaped. Some of these landfills themselves become environmental problems, since in the recent past, some were used for the disposal of highly toxic substances which leached into soil and water.

The process of extracting iron from ore produces great quantities of poisonous and corrosive gases. In practice, these gases are scrubbed and recycled. Inevitably, however, some small amounts of toxic gases escape to the atmosphere.

A byproduct of iron purification is slag, which is produced in huge amounts. This material is largely inert, but must still be disposed of in landfills.

Iron making uses up huge amounts of coal. The coal is not used directly, but is first reduced to coke which consists of almost pure carbon. The many chemical by products of coking are almost all toxic, but they are also commercially useful. These products include ammonia, which is used in a vast number of products; phenol, which is used to make plastics, cutting oils, and antiseptics; cresols, which go into herbicides, pesticides, pharmaceuticals, and photographic chemicals; and toluene, which is an ingredient in many complex chemical products such as solvents and explosives.

Scrap iron and steel—in the form of old cars, appliances and even entire steel-girdered buildings—are also an environmental concern. Most of this material is recycled, however, since steel scrap is an essential resource in steel making. Scrap which isn't recycled eventually turns into iron oxide, or rust, and returns to the ground.

Laundry Wastewater Treatment System Process Description - Industrial

Uniforms worn by manufacturing personnel, hospital employees, and meat packers; shop towels used by service stations, printing companies, and bakers; and floor mats from offices, stores and schools are all items that are washed on a daily basis by industrial laundries.

The wastewater generated from industrial washers contains sand and grit, lint, free and emulsified oil and grease, heavy metals and volatile organic compounds (VOC’s).

The treatment of these waste streams involves multiple stages. Lint removal is accomplished through screening, grit removal requires sedimentation, oils and greases are de-emulsified, coagulated and flocculated through chemical conditioning, solubilized metals are precipitated by pH adjustment, and VOC’s  can be removed with activated carbon treatment.

The typical method to treat Oil Recycling Facility wastewater is as follows:

Stage 1 Emulsion Cracking/pH Adjustment:
pH is lowered (or raised) to ~3.5 with the pH controller using acid (or caustic).  A coagulant de-emulsifier is added to break any emulsion.

Stage 2 pH Adjustment/Precipitation and Coagulation:
pH is adjusted to ~8.5 using caustic and a coagulant is added such as Alum or PAC to cause further de-emulsification and precipitation of the solids. A “pin floc” is developed indicating the emulsion and the suspended solids are precipitated.

Stage 2  - Flash Mix:
The wastewater with it’s precipitated pin floc is introduced to the flash mix zone where a polymer flocculent is added.  This stage maximizes flocculent dispersion throughout the coagulated wastewater.

Stage 3 - Flocculation:
The wastewater is now introduced to the slow mix zone to agglomerate the floc into larger particles suitable to be enmeshed with the air bubbles.

Clarifier, Dissolved Air Flotation (DAF):
The flocculated wastewater is introduced into the DAF inlet where the floc particles are comingled with a pressurized dissolved fine bubble recycle stream.  The floc particles attach to the bubbles and float to the surface where they are mechanically skimmed into the float scum sludge chamber.  The clarified treated water then exits the end of the DAF and flows downstream to sewer or further treatment if necessary.  The DAF system bubbles come from a Recycle Air Dissolving system that takes a portion of treated effluent, pressurizes it and introduces air to be dissolved.  The dissolved air comes out of solution and forms a fine bubble stream when the pressure is released at the DAF entrance in the presence of floc wastewater.

DAF Sludge Handling:
The resulting DAF waste scum/sludge is removed from the DAF automatically as the scum accumulates and is pumped to the sludge holding tank where it further thickens and accumulates a batch for disposal or processing in a filter press. The sludge is mixed and conditioned with a filter aid such as DE to improve porosity and filterability.

Sludge Dewatering:
The thickened DAF scum/sludge is allowed to accumulate sufficiently to provide a full batch for the Filter Press.  First a precoat slurry is circulated thru the filter press to coat the cloths with DE to prevent blinding of the cloth and aid in easy cake removal.  The filter press is then pumped with sludge until it is full.  The press is emptied of the “cake” which is a semi solid of approximately 20-35 % solids.  Sludge cake is high in fats and greases and solids and should be disposed of according to environmental regulations.

NOTE:
These operations can be performed with screening, microfiltration, dissolved air flotation and/or clarification.  All of these treatments produce a thickened slurry or sludge that may require additional conditioning before being processed with a filter press.  Precoating of the filter cloth may be required to reduce cloth blinding and cleaning problems.

Why does iron ore mining need water?

Why does iron ore mining need water:-

For magnetite mining, water is used in ore processing, to increase the quality and concentration of iron. After crushing, the dry ore is mixed with water and wet screened. This allows the ore to be directly fed into a steel pellet plant without further treatment. Some operations also use water to transport the ore via a slurry pipeline. Importantly, a significant amount of the water used in processing and transport is recycled.

Waste Characteristics

In certain mines with ores with high sulfur content, drainage from mine workings and waste heaps can become highly acidic and contain dissolved high concentrations of heavy metals. This Acid Mine Drainage (AMD) can have a pH of 3 or lower; sulfate levels of 800-1800 milligrams per liter (mg/L); copper levels up to 50 milligrams per liter (mg/L); iron levels up to 1000 milligrams per liter (mg/L); lead levels up to 12 milligrams per liter (mg/L); zinc levels up to 1700 mg/L, and cadmium levels of several milligrams per liter depending on the contents of the ore. The tailings pond effluent may also contain concentrations of chromium of several milligrams per liter. Base metal mining tailings decant may also contain high concentrations of thiosalts. Chemicals used in metal concentration (floatation and other) processes could also pose toxicity when released in effluents.

Surface runoffs may also pose significant environmental problems through erosion and carry-over of tailings and other mining residues. Explosives, such as ammonium nitrate, may also be present in surface runoff. Contamination of surface water can also occur from transport of mined material and from machinery maintenance and repair.

Significant levels of dust, above to 3 kilogram per ton (kg/t) (with a range of 0.003 to 27 kg/t) of ore mined, may be generated. This dust can be generated by extraction activities, crushing, ore beneficiation, transportation and traffic, and by wind borne losses. Significant releases of metal (including mercury) containing dust may result from the drying of the ore concentrate.

Process

Iron ore is converted into various types of iron through several processes. The most common process is the use of a blast furnace to produce pig iron which is about 92-94% iron and 3-5% carbon with smaller amounts of other elements. Pig iron has only limited uses, and most of this iron goes on to a steel mill where it is converted into various steel alloys by further reducing the carbon content and adding other elements such as manganese and nickel to give the steel specific properties.

Extraction

Refining

• The mined ore is crushed and sorted. The best grades of ore contain over 60% iron. Lesser grades are treated, or refined, to remove various contaminants before the ore is shipped to the blast furnace. Collectively, these refining methods are called beneficiation and include further crushing, washing with water to float sand and clay away, magnetic separation, pelletizing, and sintering. As more of the world's known supply of high iron content ore is depleted, these refining techniques have become increasingly important.
• The refined ore is then loaded on trains or ships and transported to the blast furnace site.

The Manufacturing Process

Charging the blast furnace

• After processing, the ore is blended with other ore and goes to the blast furnace. A blast furnace is a tower-shaped structure, made of steel, and lined with refractory, or heat-resistant bricks. The mixture of raw material, or charge, enters at the top of the blast furnace. At the bottom of the furnace, very hot air is blown, or blasted, in through nozzles called tuye'res. The coke burns in the presence of the hot air. The oxygen in the air reacts with the carbon in the coke to form carbon monoxide. The carbon monoxide then reacts with the iron ore to form carbon dioxide and pure iron.

Separating the iron from the slag

• 2 The melted iron sinks to the bottom of the furnace. The limestone combines with the rock and other impurities in the ore to form a slag which is lighter than the iron and floats on top. As the volume of the charge is reduced, more is continually added at the top of the furnace. The iron and slag are drawn off separately from the bottom of the furnace. The melted iron might go to a further alloying process, or might be cast into ingots called pigs. The slag is carried away for disposal.

Treating the gases

• 3 The hot gases produced in the chemical reactions are drawn off at the top and routed to a gas cleaning plant where they are cleaned, or scrubbed, and sent back into the furnace; the remaining carbon monoxide, in particular, is useful to the chemical reactions going on within the furnace.

A blast furnace normally runs day and night for several years. Eventually the brick lining begins to crumble, and the furnace is then shut down for maintenance.

Byproducts/Waste

There are a great many possible environmental effects from the iron industry. The first and most obvious is the process of open pit mining. Huge tracts of land are stripped to bare rock. Today, depleted mining sites are commonly used as landfills, then covered over and landscaped. Some of these landfills themselves become environmental problems, since in the recent past, some were used for the disposal of highly toxic substances which leached into soil and water.

The process of extracting iron from ore produces great quantities of poisonous and corrosive gases. In practice, these gases are scrubbed and recycled. Inevitably, however, some small amounts of toxic gases escape to the atmosphere.

A byproduct of iron purification is slag, which is produced in huge amounts. This material is largely inert, but must still be disposed of in landfills.

Iron making uses up huge amounts of coal. The coal is not used directly, but is first reduced to coke which consists of almost pure carbon. The many chemical by products of coking are almost all toxic, but they are also commercially useful. These products include ammonia, which is used in a vast number of products; phenol, which is used to make plastics, cutting oils, and antiseptics; cresols, which go into herbicides, pesticides, pharmaceuticals, and photographic chemicals; and toluene, which is an ingredient in many complex chemical products such as solvents and explosives.

Scrap iron and steel—in the form of old cars, appliances and even entire steel-girdered buildings—are also an environmental concern. Most of this material is recycled, however, since steel scrap is an essential resource in steel making. Scrap which isn't recycled eventually turns into iron oxide, or rust, and returns to the ground.

*Open Source  

Net neutrality: Net activism packs a punch

For the first time in the history of internet campaigns in India, a protest movement has successfully changed the course of a debate without having to take to the streets. The net neutrality movement is being fought almost totally in the virtual world. Hashtag activism isn't new in India. In recent times, several big campaigns have been bolstered by the internet which helped mobilize mass support and kept people constantly updated on events. Pink Chaddi, Jan Lokpal and the Nirbhaya movements were some examples of successful on-the-ground campaigns that were galvanized by social media. But they still needed public action — dharnas, candlelight vigils and actual pink undies — to make a difference.

But the ongoing battle for internet freedom has proved that clicktivism isn't just about passive engagement with a cause. While it's all too easy to 'like' a cause, leading to what David Carr describes as "favoriting fatigue" in an article in the New York Times, some clicks can count in the real world.

It all started when the Telecom Regulatory Authority of India (Trai) posted a vaguely worded and complicated discussion paper on net neutrality and called for public responses to it. "Clearly, many people understood that some of the proposals put forward by Trai in its paper threatened the internet as they knew it," says Anja Kovacs, who directs the Internet Democracy Project and has closely followed online activism in India.

Soon, an unlikely collective of techies, lawyers, journalists and even stand-up comics had banded together. Some of them — such as tech entrepreneur Kiran Jonnalagadda and journalist Nikhil Pahwa — had been writing and tweeting about the issue for a while but the Trai paper galvanized them. "I dropped everything and asked for help. Kiran, (lawyers) Apar Gupta amd Raman Chima, Sandeep Pillai, standup group All India Bakchod and several Reddit India users (some of whom remain anonymous), started getting involved," says Pahwa, who is the founder of Medianama. The only common factor was their love for internet and an acute worry what this policy consultation might do to destroy its open and equal nature.

Though scattered across India, once they came together online, this 'apolitical collective' was able to rope in engineers, developers, open source activists, entrepreneurs, policy experts, lawyers and journalists as volunteers.

The best way to counter propaganda and opposition was to get people involved. An abridged version of the voluminous Trai paper was posted online, and a FAQ section created on a public Google Doc. "Many came forward to answer the questions and that exercise helped create an understanding of the situation," explains Pahwa. By the time, Jonnalagadda and a few other developers set up the savetheinternet.in website by April 1, there was enough information and data points. Lawyers Gupta and Chima had also decoded the legalese and prepared cogent answers to Trai's 20 questions. This was turned into a ready-to-use email template for users to hit 'send'.

And send they did. The flood of emails to the Trai inbox number is already 803,723 and counting. The results of the social media backlash are evident — with e-commerce retailer Flipkart pulling out of Airtel Zero and several websites backing out of Facebook and Reliance's internet.org. "I was hoping to get around 15,000 responses to counter, say, 15 from the telecom lobby. Now, people make fun of me because I said that," laughs Pahwa. In this case, what also struck a chord was the idea of a bunch of young guys using tech to take on mismanagement by the older generation and corporate greed, says entrepreneur Mahesh Murthy. "We were telling them we like things on the internet as they are now."


But it is hard to sustain online outrage without an action plan, relentless groundwork and some comic warfare. So, when the contentious paper came out on March 27, the website was followed by AIB's punchy video that decoded the concept and took irreverent potshots at those who wanted to limit access while urging people to write to Trai. A lot of the lessons for the campaign came from the US where a John Oliver video turned the tide in the net neutrality debate. "We had seen that several people don't take internet petitions seriously. Also, we wanted to follow the proper legal course in this issue and not hold dharnas," says Jonnalagadda.

It is also important for campaigns to result in doable action. As Kovacs points out, savetheinternet.in and netneutrality. in gave users practical tools to respond before the April 24 deadline. The team also kept clarifying doubts and complex concepts on social media and also had an AMA (ask me anything) chat on Scrollback on Saturday while the 'other side' stuck to big words and jargon.

Of course, like every movement, this one too has attracted criticism. The proneutrality band has been branded as socialist and utopian and there were intense arguments amongst supporters. "Disagreements and arguments are not unique to the activism online," says Pranesh Prakash, policy director at Centre for Internet and Society.

Earlier in the debate, Prakash had said he'd received strong pushback from friends and allies when he spoke about the possible benefits of non-competitive zero rating, an example would be allowing companies to offer free access to their sites and apps via an arrangement with a telecom company — if effective competition exists. Airtel Zero and Reliance's Internet.org claim to do the same though most supporters remain critical. Says Prakash: "There might've been differences. But the fact that a lot of people are thinking about effects of 'free', and comparing it to predatory pricing shows that #savetheinternet is one of the better examples of engaged activism."

Online campaigns have previously also successfully mobilized people to get involved in issues they do not know much about, says author Nilanajana Roy, who is an influential voice on Twitter. The J&K flood relief efforts last year started on Twitter but got volunteers moving on the ground, she says. "People don't always realize what they care strongly about so, despite the risk of compassion fatigue or armchair volunteerism, it's worth having some online activism," says Roy.

Meanwhile, those behind the savetheinternet campaign are struggling with their new-found identity as "activists". "I think of myself as a venture capitalist and marketing consultant, not a khadi kurta-jholawala from JNU," says Mahesh Murthy, among those who strongly support the movement.

And at the end of the day, most of these activists would like to go back to their cubicles, free to browse or start a business. But not before they've tried to keep the internet open.

My First 90 Days : Don’t Get Stuck in the Cement

The first 90 days on a job are all about assessing the scope of your role and establishing connections. Even if you have fairly prescribed responsibilities, it’s still worth analyzing the scope of the position you’ve filled. You want to make sure it’s clear to everyone that you are a creative thinker and someone who is capable of finding better ways to do things.

Of course, the first and foremost requirement is that you do an excellent job at the assignments you are given. But you also want to avoid being typecast as someone with a narrow set of capabilities. If you can offer constructive suggestions about how the job could be done better, people will see that you are a creative thinker. Without being overly pushy, you want to be recognized as someone willing to volunteer new ideas.

The second part — about establishing connections — is equally critical. You want to spend the first 30 days reading your immediate supervisor, his or her bosses, and your colleagues. You need to understand what their personal objectives and priorities are, in addition to their sensitivities and hot buttons.

In the next 60 days, you want to build connections with all these key parties, using the knowledge you gained about how to read them and what their individual needs and priorities are. Listen more than talk. Show that you are willing to support your colleagues’ agendas, not just further your own.

The first 90 days offer a unique opportunity because the cement is still wet. Your colleagues will be assessing you, as the new kid on the block, and because their opinions haven’t hardened yet, you have a chance to shape what people think of you.

Over the past two years, I have gone through my own first 90 days, first when I was named President of ABC LTD and then CEO, as well. While I wasn’t new to the company, I did have a different role, and suddenly had to lead the firm and the group of senior executives with whom I’d previously been a peer.

I knew one of the first things they would be assessing me on is whether I was willing to make difficult decisions. We had an issue that needed to be addressed and I dealt with it quickly. It wasn’t a show of power, but rather an effort to make clear I was willing to make the tough calls. I didn’t move unilaterally. I made sure key stakeholders were prepared for the decision. If you don’t take advantage of that first opportunity to be decisive, and instead let a problem linger, you may encounter more institutional resistance later when you finally decide to take steps to resolve it.

Of course, your opportunity to positively effect change – and to shape people’s opinions of you – doesn’t end after your first 90 days. You want to always be proactive and offer new ideas, but it does get harder later when people have formed their opinions of you.

One of the tricks to sustaining the opportunities you have when you’re new on the job is to keep the cement wet. Keep growing and learning. Be dynamic and flexible but also avoid appearing inconsistent. Yes, that’s a fine line to walk. Let colleagues see you’re capable of adapting to change and thinking in new ways. The best way to prevent your feet hardening in cement is to always keep moving.

* post is from open source

Oil & Gas, Renewables, and Water

Conventional thinking is that hydrocarbons are ‘fossil’ fuels, and that the only way to get them is via extraction. Renewable energy is viewed as an ‘arms length’ alternative - one either does oil and gas or one does renewables. From a pure technology standpoint, such distinctions are meaningless. The economics are fast catching up - the situation is sufficiently complicated that the entire situation needs rethinking.

The first group of interested parties are policy makers - at present sovereign leaders, governors, and trading blocs are facing collapsing prices, correspondingly collapsing tax receipts, employment reductions, investment shrinkage, and in some cases remediation and clean up costs. For some this is great, for others a disaster, and increasingly it can be both. The US and UK, with big industrial interests and huge extraction industries, are merely moving pieces around on the board. Countries that are dependent mostly on extraction are in big trouble.

The second group are the industry players. This includes the majors and independents, but it also means in particular the various suppliers - geophysical analysts, pipeline operators, energy traders, etc. A huge amount of knowledge applies to the process of finding, extracting, and transporting hydrocarbons - much of this is just as useful in dealing with electric power transmission and water management.

Oil, Gas, and Wind Power

One of the original reasons for construction of massive wind turbines in West Texas was to power oil wells. In the early 2000s, power companies were in no mood to build 200Mw power stations ‘out in the middle of nowhere’. Wind turbines could be installed quickly, and scaled appropriately - if you needed 50 megawatts you put in as many turbines as did the job. Of course, in the middle of the night when the wind is howling, such turbines are producing more than anyone can use, but so what?

Offshore wind turbines are proving to be attractive for a number of reasons. The main one is NIMBY - people think that turbines ‘tear up the landscape’. When a platform already exists, as one finds in various parts of the Gulf of Mexico or the North Sea, one suspects that plopping a turbine on top helps one avoid an expensive decommissioning process. Power consumers are left to enjoy their ‘viewshed’.

Someone who drives a truck for collecting oil or disposing of water wouldn’t think twice of hauling around turbine blades. The people putting up refineries and long distance electric towers are the same people putting up wind turbine pylons. Roughnecks might find that the pay for maintaining turbines and transmission lines is closer to average, however it is also predictable.

Long Distance Pipelines and Water

People are predicting that awful things will happen as the US ‘runs out of water’. What this means more particularly is that aquifers are depleted and/or that urban expansion will outgrow existing reservoirs. There is enormous infrastructure for long distance transmission of natural gas, oil, and refined products, however it is relatively uncommon to move water over such distances. Water is, in comparison to petroleum products, ‘cheap’, however it is also essential. Creating long distance water transmission networks is likely to need government involvement - such infrastructure will be used largely to insure supplies during droughts.

One of the side products of oil extraction is water - often brackish (salty). This is usually injected back in the ground, in some cases in such a way as to enhance oil production. Desalination processes have become more effective and efficient. In situations where the energy to drive the desalination is renewable, this water might as well be used to augment municipal or agricultural supplies.

Methane, Garbage, and Sewage

Methane is one of the decay products of organic waste (others are carbon dioxide and hydrogen sulfide). ‘Landfill gas’ is collected and used to generate power or is combined with other sources and piped to municipal users. Methane is the primary constituent of natural gas. To this degree natural gas is ‘renewable’ - breaking the link between ‘fossil’ and ‘hydrocarbon’. Sewers have similar decomposition outputs. As water becomes more valuable and the processes for cleaning it up more economical, sewage becomes increasingly simply a feedstock for producing pure water, natural gas, and various other chemicals.

Many organic waste products can be decomposed in ‘digesters’ - basically tanks full of (for example) the residues left over from brewing beer, where microbes break down the organic matter further, producing methane and CO2 as byproducts. In some cases such infrastructure is described as a ‘biorefinery’ - in short an ‘oil refinery’ that uses organic matter instead of oil as its input.

Energy Storage in Flow Batteries

Flow batteries have tanks with separate reactants, which are situated between electrodes where they chemically react to product electricity. The reaction product flows ‘out’ and is stored in a third tank. When the process is reversed, the chemical product of the electricity generation ‘flows backwards’ through the electrodes, where it is converted back to the original reactants. Companies are starting to commercialize these. While their viability isn’t yet clear, it’s worth noting that the ‘power storage’ situation is close to solution at the municipal scale.

People that build and maintain oil tanks probably wouldn’t give one of these a second thought. In short, another tank, another project, another contract. Often these would be built either in the area of, or to replace, oil storage tanks.

One side effect of such chemical reactions is heat (regardless of reaction direction). Such heat could be used to heat green houses, pools, or public buildings such as schools or airport terminals.

Sequestration and Security

CO2 in the atmosphere is eventually going to be taken up by organisms, and is ‘sequestered’ in plant mass. The current conventional wisdom is that if we stopped emitting CO2, it would take 100 years to return to preindustrial norms. When one has wells and coal mines, one already has the plumbing and repository for various forms of carbon. As renewable energy gets cheaper, at some point it becomes viable to simply convert CO2 back into either coal or oil (or something analogous, such as middleweight alkanes and/or anthracene). These would be pumped or deposited into ‘strategic reserves’. This would be a means for ‘managing’ levels of CO2 and other greenhouse gasses. Such reserves would be situated in ways to make them useful near major markets - thus they would be near refineries and/or power plants.

Resources and Resolution

At present, ‘energy resources’ are viewed as reservoirs of oil, gas, coal, or other minerals (uranium, for instance). However, increasingly ‘resources’ are a mix of infrastructure and engineering talent - wind farms, solar plants, pipelines, and skills to build and maintain energy gathering infrastructure. A county’s ‘energy security’ is just as much a matter of knowing how to acquire and deploy renewable energy as it is having control over hydrocarbon deposits. Businesses should focus on maintaining a diversified portfolio of both natural and human energy resources - oil, gas, biomass, and turbines; but also engineering talent, patents, demand management, and refining/conversion plants. The focus should be on making sure that consumers have reliable access to power, water, and fuel; and that the resource portfolio be periodically rebalanced to exploit lower costs and greater efficiencies.

* post is from open source

Ground Water - Sulfate Removal Technologies

Sulfate Removal Technologies

Magnesium sulfate crystals photographed under polarized light

By Mark Reinsel, Ph.D., P.E., Apex Engineering, PLLC

Sulfate concentrations in water have come under increasing scrutiny from regulatory authorities over the past two decades.  In contrast to contaminants such as nitrate, arsenic, and heavy metals, sulfate has no primary standard for drinking water or aquatic life.  However, the secondary standard for drinking water in the U.S. is 250 mg/L and concentrations above 600 mg/L may create laxative effects.  In Minnesota, future sulfate discharges may be limited to as low as 10 mg/L (an unenforced standard that is currently under review) to protect wild rice habitat.  Guidelines for sulfate levels around the world are shown in Table 1.

TABLE 1.  RECOMMENDED MAXIMUM SULFATE LEVELS

Authority	Sulfate Concentration (mg/L)
USA	500
Canada	1,000
European Union	1,000
South Africa	600
Australia	1,000
World Health Organization (drinking water)	250

From:    Ramachandran, 2012

Many treatment technologies have been developed and refined to remove sulfate from water, including chemical, biological, and physical processes.

Chemical Treatment Technologies

Chemical methods for reducing sulfate concentrations include:

1. Lime precipitation
2. Barium precipitation
3. The CESR process
4. The SAVMIN™ process

The simplest technology for reducing high sulfate concentrations is lime precipitation.  Adding calcium as pebble lime, hydrated lime, or limestone can precipitate calcium sulfate (gypsum) and reduce sulfate concentrations to the solubility limit of 1,500-2,000 mg/L.  Concentrations already below this level will generally be unaffected by lime addition.  Typical equipment requirements for this process are a lime silo, lime slaker, or other reagent feed system, reaction tank, and clarifier.  If sulfate must be further reduced (“polished”), an add-on process such as barium, CESR, or SAVMIN is recommended.

As a polishing step for sulfate removal, barium salts can be added to precipitate barium sulfate, which has a very low solubility in water, with the final sulfate concentration limited only by the amount of barium added and reaction time.  Typical salts used are barium chloride and barium carbonate.  The disadvantage of barium addition is the relatively high chemical cost; a recent price for barium chloride was about $2/lb.

The Cost-Effective Sulfate Removal (CESR) process was originally developed as the Walhalla process in Europe in the 1990s.  A specialized powdered cement (reagent) is added to precipitate ettringite, which is a hydrated calcium aluminum sulfate compound.  The CESR process requires lime addition and a pH of about 11.3 for ettringite formation, and can achieve sulfate concentrations far below the gypsum solubility limit (Reinsel, 2001).  Sulfate concentrations are typically limited only by the amount of reagent added and reaction time.  Disadvantages are the large amount of sludge generated, and the fact that high sodium concentrations inhibit the process.  The CESR reagent costs about $0.40/lb.

The SAVMIN process was developed by MINTEK in South Africa in the 1990s to treat acid mine drainage.  Ettringite is precipitated as in the CESR process, in this case by recycling aluminum hydroxide.  Sulfate levels can be reduced to less than 200 mg/L by this process.  MINTEK has signed an agreement with Veolia South Africa to further develop the SAVMIN process (Ramachandran, 2012).  The first pilot evaluation of the improved SAVMIN process using Veolia’s MULTIFLO™ clarifier was recently undertaken.

Biological Treatment Technologies

If metals are present in the water to be treated, biological treatment has the advantage of being able to remove them along with sulfate via metal sulfide precipitation.  Biological processes for removing sulfate include:

1. The THIOPAQ™ process
2. Other packed bed or fluidized bed reactors
3. Passive treatment
4. In situ treatment

In the THIOPAQ process developed by the PAQUES company (Netherlands), sulfide is produced by contacting the sulfate-containing stream with sulfate-reducing bacteria (SRB) in the presence of a carbon source (electron donor) such as hydrogen gas or acetic acid.  The reaction for hydrogen is:

                SO42- + 4 H2 + SRB à S2- + 4 H2O

Excess sulfide can then be converted to elemental sulfur (So) with aerobic bacteria as follows:

                HS- + ½ O2 + bacteria à So + OH-

The main advantages claimed by this process are:  a) H2S concentrations are low, b) most of the H2S present will be dissolved in water rather than in the gas phase, c) the process can be conducted at ambient temperatures, and d) flow rates can be varied.  The first commercial plant for this process was built in 1992 at the Budel Zinc refinery to remove zinc and sulfate from acid plant blowdown (Ramachandran, 2012).  Numerous other plants are in operation using this technology.

Apex Engineering has designed several relatively small-scale treatment systems for sulfate removal from mine water (Table 2).  The first three are packed bed systems with a continuous carbon source feed (methanol or ethanol), while the last is a passive bioreactor.  We are in the process of designing two more passive bioreactors for construction in 2015.

TABLE 2.  SULFATE REMOVAL SYSTEMS
Location	Client	Year Built	Description
Babbitt, MN	PolyMet Mining	2012	Packed bed 10-gpm system for mining pit lake
Republic, WA	Kinross Gold	2006	Packed bed 50-gpm system for mining-impacted groundwater at closed gold mine
Republic, WA	Kinross Gold	2005	Packed bed 6-gpm system for mining-impacted groundwater near active tailings impoundment
Elko, NV	Veris Gold	2014	Passive 10-gpm system for seepage from rock disposal area at active gold mine

Passive bioreactors or biochemical reactors are another proven technology for sulfate removal.  Biochemical reactors (BCRs) are engineered treatment systems that use an organic substrate to drive microbial and chemical reactions to reduce concentrations of metals, acidity, and sulfate (ITRC, 2013).  BCRs have been used primarily to treat mining-influenced waters over the past two decades.  BCRs may be configured to operate with or without external energy and chemical input, and can often be sustained for months at a time without human intervention (hence the name “passive bioreactors”).  A list of sulfate-reducing BCRs is shown in Table 3.

TABLE 3.  BIOCHEMICAL REACTORS

Site Name	Location	Design Flow (gpm)
West Fork	Missouri	1,200
Golinsky Mine	California	10
Iron King Mine	Arizona	7
Yellow Creek 2B	Pennsylvania	10
Ore Hill Mine	New Hampshire	6
Golden Cross Mine	New Zealand	300
Kendall Mine	Montana	5
Haile Mine	South Carolina	6
Quinsam Mine	British Columbia, Canada	250
Delamar Mine	Idaho	20
Luttrell Repository	Montana	5

According to Mattson (2014), standard bioreactors have a performance advantage over BCRs but at increased capital and O&M cost.  Standard bioreactors such as THIOPAQ or packed bed systems are more efficient and can be better adapted to large-scale applications, according to Mattson.

In situ sulfate reduction (ISSR) is an innovative technology that combines biological sulfate reduction with remediation hydrogeology approaches (Gillow et al., 2014).  A carbon source such as lactate is injected to catalyze sulfate reduction via in situ SRB, with sulfur then sequestered as sulfide minerals and/or elemental sulfur.  ISSR was developed by ARCADIS.  Apex Engineering has incorporated ISSR as a component of the treatment systems for Kinross Gold and Veris Gold (Table 2).

Reported advantages are:  a) many choices for low-cost carbon sources, b) low potential for process disruptions, and c) less effort to operate than pump and treat.  However, challenges include managing the precipitates, managing final water quality, distributing the carbon source in the subsurface, and the possibility of sulfate “rebound” after treatment ceases.  Several options are available for injecting the carbon source. 

ARCADIS’s view on the future outlook for ISSR is that:

• It is a viable technology for specific applications.
• It is important to consider depth, saturated thickness and downgradient receptors.
• Iron addition to control dissolved sulfide should not be necessary.
• Hydraulic performance and biogeochemical parameters should be monitored.
• The technology should be scaled from pilot-scale to intermediate/full-scale.

Physical Treatment Technologies

Physical processes for removing sulfate include:

1. Ion exchange processes such as GYP-CIX and Sulf-IX™
2. Nanofiltration
3. Reverse osmosis

GYP-CIX is a fluidized bed ion exchange process developed in South Africa to remove sulfate from water that is close to gypsum saturation, so it could be used as a polishing step after lime precipitation.  It is the historic predecessor to the Sulf-IX process, which maintains the IX resin in the same vessel to minimize attrition from resin handling.

BioteQ Environmental Technologies of Vancouver has developed the Sulf-IX process to remove sulfate from waters high in hardness and at near gypsum saturation levels.  The Sulf-IX process is designed to selectively remove calcium and sulfate from water to achieve effluent compliance with sulfate discharge limits.  It is a two-stage IX using two resins (one cationic and one anionic) to partially demineralize the feed water.  The cationic and anionic resins are regenerated using sulfuric acid and lime, respectively, to generate nontoxic solid gypsum (the only byproduct of the process).  One significant advantage of Sulf-IX over membrane systems is that it produces no brine solution, providing substantial cost savings on brine disposal via storage or evaporation.  The first commercial plant using this technology has been operating in Arizona since 2011, with a capacity of 600 m3/day (110 gpm).

Nanofiltration (NF) is a membrane process that can be used to remove sulfate and other contaminants.  It operates at higher pressures (higher operating costs) than microfiltration or ultrafiltration, but lower pressures than reverse osmosis (RO).  NF will have a high removal (high rejection) of sulfate because it is a divalent ion, but will have lower rejection of monovalent ions such as nitrate and sodium.  For NF and other membrane processes, sulfate and other contaminants are concentrated in a reject stream, which may comprise between 10 and 40 percent of the original flow.  Disposal or treatment of the reject stream is another consideration.

Reverse osmosis for sulfate removal is generally only considered when monovalent contaminants must also be removed.  Otherwise, NF is more cost-effective for sulfate removal than is RO.

Golder Associates presented a recent paper summarizing sulfate removal treatment processes (Golder, 2014).  Their conclusions include:

• Active biological treatment has never become popular despite extensive research and development.
• Passive treatment has advanced and may be cost-competitive.
• Operating costs for IX are sensitive to reagent prices and reagent utilization efficiency.
• Membrane technologies for sulfate removal below gypsum solubility levels are commercially demonstrated and have achieved acceptance.
• The cost and complexity of advanced sulfate removal projects warrants independent peer review.