Simpler mining water treatment

Together with Montana, GeoChemTec has the honour and pleasure to continue the Baccu Locci project of simpler mining water treatment with geochemical technology and minerals.

In a presentation, 'Simpler mining water treatment with geochemical technology and minerals' , we show case studies elucidating the application of passive treatment of heavy-metal contaminated mining water, from abandoned historic mines in Mediterranean countries. The water with metal concentrations up to a gram per litre of the remediated mining waste site of Baccu Locci was successfully treated down to less than a milligram per litre, by gravitational flow through compact filters with very reactive porous mineral granules, as developed by GeoChemTec. The technology of preparation of materials and the operation and maintenance of the filters is straight forward and can be managed by local contractors in remote mountainous areas without power, industrial equipment and constant supervision.

The lecture was presented at Remtech Europe 2021. Please, feel free to download the slideshow for further details

Accidents will happen: Insured

Severe environmental pollution by heavy metals can be extremely costly to remediate and insure if it concerns very large-scale and long-term operations. A famous example is cadmium pollution of the Toyama Prefecture (Japan) by mining, causing Itai-Itai disease with softening of bones and kidney failure, taking a century of environmental remediation since 1912. Another example is mercury poisoning discovered in 1956 in Kumamoto Prefecture (Japan), causing the Minamata disease affecting the nervous system, leading to insanity (as from 'mad as a hatter' like the hat making Mancunians working with mercury. Large-scale cleanup and settlement for damages of nearly $100 million only reached completion almost half a century later in 2010. Finally, there is the famous case of the more than 10 years of severe Hinkley groundwater contamination between 1952 and 1965, with genotoxic-carcinogenic chromate, leading to a class action lawsuit (starring Julia Roberts as Erin Brockovich) that was only settled in 1996 for a staggering $333 million.

At RemTech 2020 conference, Duncan Spencer shows what role insurance can play in managing pollution liabilities during remediation projects, inherited, or created during works. It is argued that liability insurance covering risk of larger damages in the order of $100 million is not that readily available, has maximum terms of 5 to 15 years and demands best available remediation strategy, guaranteeing maximum control over spreading of toxic substances, when immobilized on site or disposed elsewhere.

From a geochemical technology point of view, long-term isolation of pollutants in disposal sites in the dynamic natural environment of the geochemical cycle is impossible and not desirable. Since disposal sites cannot remain completely sealed forever, the controlled leakage of toxic compounds is a preferable solution, needed to slowly defuse a potential environmental bomb. Dilution is a solution to pollution if concentrations in the bio-available phase can remain below safe natural background values.

For truly stable methods of immobilization of most toxic pollutants, such as radioactive compounds now temporarily stored above or possibly definitely in deep clay deposits below ground, nature offers minerals and concretions as examples of alternatives. Take for instance concretions of quartz, composed of the most stable mineral at earth surface conditions and able to encapsulate heavy metals. Not only were they our best friend during the stone age, making for the toughest tools of flint, but further understanding of the way they form, might provide us with efficient geochemical technology to spontaneously attract, concentrate and maintain immobilized, the most dangerous pollutants, even within the dynamic environment at the earth surface and also on the very long-term.

Ashes to ashes: Coal slag

Since the first use of railway steam locomotives (1804, Richard Trevithick) and the burning of coal for electricity generation, great amounts of coal slag and fly ash are produced causing environmental problems requiring recycling and remediation.

At RemTech 2020 conference, Ugo Bacchiega presented a detailed study of a large historic coal slag waste deposit along the Ferrara railway station in the Italian Alps. Soil drillings, monitoring wells, trench, geophysical surveys, and chemical analysis show the size and composition of a body of soil, ground water and waste, contaminated by heavy metals and hydrocarbons. It was decided to leave the contaminated materials on site, keeping them in permanent security ('messa in sicurezza permanente'), by containment with a constructed green wall of vegetated, re-enforced earth.

From a geochemical technology point of view, this coal slag is only a waste when it is stored too far away from the site where it becomes a valuable commodity. It is our task to imagine application that is efficient enough to overcome transport costs, as the coal slag is an alkaline mineral reagent, required for doing work in an acid environment.

With nature as an example, we look at orebodies and think of self-sealing layers and the concentration of heavy metals herein for secondary mining. Coal slag or fly ash with hydrocarbon substrate for bacteria, when properly combined with metal sulfide mining waste, allows for recycling of metals and sequestering of carbon dioxide and mitigating climate change.

Blowing in the wind: Asbestos

The asbestos chrysotile, is a fibrous magnesium silicate mineral of which airborne dust-sized particles can be carcinogenic. This heat resistant and chemically inert mineral has been abundantly used in construction before it was banned about 20 years ago in Europe. How can geochemical technology manage asbestos pollution?

When asbestos containing constructions are damaged, special cautionary measures are required to prevent the spreading of asbestos dust. The challenges posed by exceptionally large constructions and the way these can be met with sophisticated technology were discussed by Mariangela Venco (ENI Rewind) in her lecture titled Design of asbestos removal from large-scale industrial site asset, presented at the RemTech Europe 2020 conference.

How collected asbestos is best handled and what treatment technologies are needed remains to be seen.

Can it be buried safely on the long term in special disposal sites, should it then first be encapsulated and consolidated and what would be the minimum disposal costs to stimulate recycling and treatment technology?

Can asbestos be economically transformed into harmless glass by melting or into filler by ball milling at over 1000 degrees Celsius, destroying the fibrous crystal structure?

How can we handle the voluminous and impure asbestos, diluted by building waste, soil or water?

What role can geochemical technology play in designing safe, cost-efficient and effective storage in acidic soil with natural weathering that is supported by fungi, mitigating climate change, when released magnesium ions sequester carbon dioxide?

Going with the geochemical cycle

Together with Montana, GeoChemTec had the honor and pleasure to give a presentation on geochemical technology with minerals at Remtech Europe 2020

In our presentation, 'Going with the geochemical cycle', we show various case studies elucidating the application of geochemical technology with minerals for the treatment of heavy-metal contaminated water, rock and soil, from abandoned historic mines in Mediterranean countries.

Remtech Europe is part of RemTech Expo, the most important Italian event on remediation technologies with European Commission’s Joint Research Centre (JRC) as part of the scientific committee. The internationally oriented conference enables sharing of knowledge, new ideas and elucidating case histories, encouraging the development of remediation processes and application of innovative sustainable technologies, bringing suppliers of available services and technologies together with owners of environmental problems, providing a platform for discussion between various stakeholders.

Please, feel free to download the slideshow for further details

Color Our Reef ALive

Corals are most elegant bio-geochemical engineers, building their colorful homes out of sunlight and air. But why do they bleach when stressed and how can we help them relax?

Modern, shallow (sub) tropical reefs are made by hermatypic stony ‘scleractinian’ corals. They are colonies of polyps with stingy tentacles, like the related sea anemone, secreting calcium carbonate cups; the corallite, an exoskeleton in which they can retract.

Hermatypic corals are colored by pigmented unicellular algae that they host in their tissue at concentrations of several million per square centimeter. These algae are dinoflagellates known as zooxanthellae which photosynthesize, using sunlight and carbon dioxide to produce oxygen and organic compounds, which they share with corals in exchange for nutrients and protection.

When corals are stressed, for example by extreme water temperature, salinity and light, they may expel their colored zooxanthellae and turn white (Coles & Jokiel, 1978). As the corals bleach, they become brittle and more prone to disease. When conditions return to normal, corals may incorporate the zooxanthellae again and regenerate after a while (Buddemeier & Fautin, 1993). The extreme circumstances may change the zooxanthellae from beneficial symbionts into harmful parasites that need to be expelled and if, for instance by climate change, such conditions occur too often, without time for regeneration, coral bleaching becomes permanent and entire reefs will die (Baker et al., 2018).

Coral reefs are the most diverse ecosystems on earth. They are not only a wonderful underwater world of great beauty, but they protect vast stretches of coast against wave erosion and ultimately feed billions of people with hundreds of billions of dollars’ worth of seafood. Coral reefs deserve protection and we have to:

  • Learn how to diminish environmental stress for coral reefs
  • Teach corals how to deal better with their environmental stress

We ask ourselves, for improving the well-being of coral hosts and their symbiotic guests, what bio-geochemical technology is best to use?

String of microbially precipitated nano crystals of magnetic iron oxides within the elongated cell of a magnetotactic bacteria

What is going on between minerals, metals and microbes in bio-geochemical technology?

By using minerals in bio-geochemical technology, we can influence the interaction between microbes and metals, to improve environmental management.

The health of soil and water can be managed through the interaction between microbes and metals, using minerals in bio-geochemical technology. Microbes (bacteria, fungi and algae) influence metal concentrations when deteriorating rock and minerals during bio-weathering and when forming, directly or indirectly, minerals during bio-mineralization (Gadd, 2010).

This interaction between minerals, microbes and metals determines the availability of life sustaining resources and life-threatening toxins that regulate the natural habitat of the critical zone or biosphere; the near-surface environment of rock, soil, water and air, home to living organisms.

Microbes concentrate the essential nutrients from mineral surfaces (Vaughan et al, 2002); i.e. carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur that form 95% of the biomass and other elements with essential biochemical and structural functions such as K, Ca, Mg, B, Cl, Fe, Mn, Zn, Cu, Mo, Ni, Co, Se, Na and Si. Microbes and minerals also control the concentrations and bio-availability of thirteen trace metals and metalloids that are considered priority pollutants i.e. Ag, As, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl and Zn (Sparks, 2005).

Many examples show how microbes interacting with metals may operate in environmental management. For instance, microbial metal mobilization through bio-leaching can be used for metal recovery, recycling and bioremediation of mineral waste and contaminated soil (White et al, 1998). Microbes can be used to immobilize metals by bio-precipitation, for decrease of toxic concentration in bio-available phases. Reduced metal(loid)s like Se(0), Cr(III), Tc(IV) and U(IV) form insoluble precipitates through reduction in anaerobic processes. Single-oxidation-state metals are immobilized during precipitation with biologically produced sulfide and phosphate. Immobilization through microbial biosorption occurs by physico-chemical binding of metals on dead and living walls of microscopically small cells that expose a very high surface per weight to the metal containing solution. Biominerals such as microbial nano crystals of magnetic iron oxides precipitated by magnetotactic bacteria can be used for sorption of metals and their recovery from solution by magnetic separation.

For practical use of microbes and minerals in environmental management we have to ask: How can microbes manage metals better with minerals in biogeochemical technology?